Source: IOWA STATE UNIVERSITY submitted to
DEVELOPMENT OF A MULTI-ENZYME BIOSENSOR WITH INK JET PRINTED NANOPARTICLES FOR REAL-TIME MULTI-PESTICIDE SCREENING IN THE FIELD
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
1009251
Grant No.
2016-67021-25038
Project No.
IOWW-2015-07819
Proposal No.
2015-07819
Multistate No.
(N/A)
Program Code
A1511
Project Start Date
Mar 1, 2016
Project End Date
Nov 30, 2020
Grant Year
2016
Project Director
Claussen, J. C.
Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
Mechanical Engineering
Non Technical Summary
The world population is expected to increase in size by a third to approximately 9.7 billion by the year 2050. This projected 2050 world population would require a 70% increase in worldwide food production.More efficient and sustainable farming techniques are needed to meet such growing global food demands as population increase, available cropland reduces and climate change inflicts additional stress on crops.Developing soil-based biosensors that precisely tell the farmer when to fertilize their crops is desperately needed to increase crop efficiency while reducing negative environmental impacts. Pesticides are necessary to maintain and increase crop yields in order to meet the food demands of the burgeoning world population, however, pesticides propose a tremendous health and environmental burden on the environment and in particular watersheds. The now seemingly ubiquitous nature of pesticides in the environment, even at "low" concentrations, have far reaching and diverse negative effects from potential links to autism spectrum disorder to honey bee colony decline. Therefore, the need to regulate pesticide use and track pesticide run-off is paramount to environmental protection and in particular protection of surface and ground water where pesticides can be further transmitted through the food chain.Currently farmers do not have a reliable and cost-effective method to monitor pesticide concentrations in crop fields; do not have the tools necessary to prevent pesticide overuse and hence prevent pesticide water-contamination; and do not have a rapid, inexpensive method to monitor fertilizer levels in the soil and subsequently reduce/prevent fertilizer run-off into precious watersheds. Current methods for fertilizer concentration testing in soils include chromatographic laboratory methods that aretime consuming and expensive; require extensive sample preparation/cleanup; specialized personnel and instrumentation; and in some cases involve toxic solvents and chemicals that can be more harmful to the environment than the pesticides themselves. Thesechromatographic methodsare therefore not amenable to in field-testing nor for use in developing countries where resources are limited.This research will fulfill this technology gap.This project will produce a disposable test strip that can monitor pesticides levels on-site in soils in a manner of minutes with a portable electrochemical reader. The test strip will be patterned after the common glucose test strip that diabetics use to monitor their glucose levels and will be able to interface with an electrochemical reader much like the glucometer diabetics use. The test strip sensor developed in this project will be fabricated with inks that contain non-toxic nanoscale metal particles and biological molecules called enzymes. The combination of these nanoparticles and enzymes will be capable of selectively sensing pesticides in soils. Mathematical modeling and electrochemical experiments of these nanostructured test strip biosensors will be performed to determine the size, shape, and density of nanoparticle-enzyme compounds that are necessary for sensitive and selective pesticide detection in soil samples. The ultimate goal of this proposed project is to provide farmers and field help with easy-to-use, inexpensive, and rapid means to test the level of pesticides in the soil at the site of contamination. Such sensor technology will therefore be particularly well-suited for use in remote or resource limited countries where access to such technology is nonexistent. This technology is expected to decrease the pollution of farmlands and the environment due to water runoffs from overuse of pesticides. The progress of this work will be published in peer-reviewed journal articles, presented in national research conferences, and explained in workshops and classroom environments.
Animal Health Component
0%
Research Effort Categories
Basic
70%
Applied
20%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
40252202020100%
Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
5220 - Pesticides;

Field Of Science
2020 - Engineering;
Goals / Objectives
The research goal of this project is to develop the nanomanufacturing techniques needed to create highly sensitive, multi-enzyme biosensors that can provide rapid, inexpensive, and in situ parallel screening of multiple pesticides in a single sample. Such a pesticide-screening test would be used to alert the user of potentially dangerous levels of pesticides in water, soil, or food products. More costly, but more accurate, chromatographic methods (i.e. gas or liquid chromatography coupled with mass spectrometry) could then be reserved for identifying and quantifying pesticides in samples that did not pass the multi-enzyme biosensor-screening test.Objective 1. Develop a kinetic model to help pinpoint the optimal nanoparticle size and surface chemistry for immobilized enzyme performanceObjective 2. Experimentally identify the nanoparticle surface chemistry and enzyme-to-nanoparticle coupling chemistry that will maximize activity of immobilized enzymes on distinctly sized quantum dots and gold nanoparticles.Objective 3. Develop printed enzyme-nanoparticle biosensors on recyclable surfaces that are able to screen multiple pesticides simultaneously on-site with soil samples acquired from the field.
Project Methods
EffortsLaboratory instruction carried out the US Naval Research Laboratory. Two graduate students will receive instruction on how to work with enzyme-nanoparticle bioconjugates and perform enzyme assays.Biosensor techniques will be integrated into a graduate level course taught at Iowa State University. The teaching of the class will involve a flipped classroom environment where students interact in small group settings on a regular basis to discuss biosensor techniques and the integration of nanotechnology into biosensors.A formal lecture and small workshop on nano-biosensors will be organized and presented at the annual Nanotechnology for Defense Conference.PI and co-PIs of the proposal will instruct graduate students in the laboratory one how to perform mathematical modeling and biosensor fabrication and testing.EvaluationKey MilestonesA mathematical model that is capable of predicting the diffusion-reaction kinetics associated with enzyme-nanoparticle bioconjugates reacting with incident substrate.A graphene electrode that is printed on a disposable substrates (e.g., paper) that retains its electrical conductivity and electroactive nature upon use in soil samples.A nanoparticle carrier that is capable of holding multiple attached enzymes in a way that retains or improves the activity of the attached enzymesAn enzyme-nanoparticle bioconjugate that is capable of being printed onto a surface without significant loss to enzyme activity during testing in soil.Data To Be CollectedMathematical modelFluorescent assays that display enzyme kinetic dataPrinted graphene characteristicselectrical conductivityelectrochemical activitywettability on different substrates (e.g., paper, plastic, glass)Nanoparticle-enzyme Ink formulation measurementsViscosityConcentrationParticle sizeSurface tensionNanomaterial Printer Setting MeasurementsWaveform settingsNozzle TemperatureSubstrate temperatureJetting velocityDrop spacingBiosensor TestingElectrochemical data of pesticide concentrations in controlled environments (e.g., buffer solutions)Electrochemical data of pesticide concentrations in soil samples

Progress 03/01/16 to 11/30/20

Outputs
Target Audience:During this final year of the project the target audience that we reached included experts in the field and interested industry representatives. Researchers in the field were reached through the four journal articles that we published. One of those publications made the front cover of the journal, Journal Materials Chemistry C (impact factor = 7.059). The citations for these research presentations are given in the products section of this progress report. The ongoing pandemic cancelled all conferences and university talks during this timeframe. However, we were able to present these research results at a NSF planning meeting for a potential Industry-University Cooperative Research Center (IUCRC) titled 'The Center for Soil Dynamics Technologies'. The webinar included about 30 industry experts who were interested in agricultural technology. As with the Global Insurance Symposium in Des Moines last year, the industry experts were interested in how the sensors in this project could be deployed to warn of pesticide drift and water/soil contamination so remedial action could take place before further environmental damage (i.e., pollution of drinking water supplies) could take place. Finally, the results of this research were disseminated to the general public through a nightly news piece put together by the Iowa ABC News station (WHO Channel 13) located in Des Moines which is the capital in Des Moines. The news station came to our research laboratory in October of 2020 and they broadcast the news piece in November (see https://who13.com/news/isu-researchers-working-on-9-15-million-bio-based-electronics-project/). The news team also interviewed the lead graduate student that worked on this pesticide biosensor project. The news piece highlighted our work with pesticide biosensors as well as our related research projects on developing sensors with graphene made from bio-based materials. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?During this no cost extension phase of the project we have been able to continue to train one postdoc, two graduate students and one undergraduate student. The graduate and undergraduate students continued working on this project full-time in Dr. Claussen's lab while the postdoc worked at the US Naval Research Laboratory with Dr. Medintz The graduate student in Dr. Claussen's laboratory was able to acquire expertise in biosensing, graphene printing and scribing while the student in Dr. Medinitz's lab learned how to synthesize enzymes for this project. The graduate student working in Dr. Claussen's laboratory replaced the graduate student that was previously working on this project. This student therefore will be able to continue to work on pesticide biosensors for years to come and will help the laboratory continue this important research on pesticide sensing even after this project is over. Also, an additional undergraduate student was trained in on this project in Dr. Claussen's laboratory. This undergraduate research experience allowed the student to gain valuable laboratory experience and to see if they would like to continue their education in graduate school. How have the results been disseminated to communities of interest?The main results of this project were disseminated through 4 peer-reviewed journal article publications, 3 invited conference talks, and 3 invited university presentations, and 1 industry sponsored seminar. Three of the journal articles made the front cover of thejournals titled Journal of Materials Chemistry C, ACS Sensors, and Nanoscale Horizons. All conferences and invited university talks were canceled due to the ongoing pandemic; therefore, this research could not be presented at these typical venues. However, we were able to hold a webinar with over 30 industries to help establish a NSF funded Industry-University Cooperative Research Centers (IUCRC) titled 'The Center for Soil Dynamics Technologies'. In this webinar and with other discussions we were able to present our work on pesticides sensors and demonstrate how the sensors could be used in the field to help the farmers that the amount of pesticide applied to a field was the amount that the crop plants received, help farmers understand if their crop damage was caused by pesticides that drifted to their fields from neighboring ones, and help researchers understand the extend of pesticide contamination in farm fields, surface waters, and even drinking water. The publications and this webinar allowed us to disseminate the results of this work, gain valuable feedback especially from industry, and open the door for future industry collaborations. These manuscripts and the webinar given listed in the 'products' and 'other products portion of this report. Finally, the results of this research were disseminated to the general public through a nightly news piece put together by the Iowa ABC News station (WHO Channel 13) located in Des Moines which is the capital in Des Moines. The news station came to our research laboratory in October of 2020 and they broadcast the news piece in November (see https://who13.com/news/isu-researchers-working-on-9-15-million-bio-based-electronics-project/). The news team also interviewed the lead graduate student that worked on this pesticide biosensor project. The news piece highlighted our work with pesticide biosensors as well as our related research projects on developing sensors with graphene made from bio-based materials. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have made significant progress in transitioning our printed sensors into multiplexed pesticide biosensors in this year of the project were the biosensor will be integrated with a flow cell to test multiple pesticides with one field sample. In order to make the electrodes adhere to adhesive Kapton®, the electrodes were created with gold leaf in lieu of graphene. In summary this work developed a new manufacturing technique we coined Etching Inkjet Maskless Lithography (E-IML) to synthesize and pattern NPGL and metal leaf materials (thickness ~100 nm) for flexible electronics. E-IML utilizes the versatility of an inkjet printer to pattern electrodes for rapid prototyping, even on flexible substrates (polyimide). In order to demonstrate the utility of the peel-and-stick biosensors, a disposable tape pesticide biosensor and reusable 3D printed flow cell were developed for organophosphate detection in soil samples. Multiple NPGL working electrodes were fabricated on single devices so that that each electrode could be functionalized with distinct concentrations of the enzyme acetylcholinesterase (ACHE). Paraoxon (a model organophosphate) sensing results demonstrated a low detection limit (0.53 pM) and high sensitivity (376 nA/nM). The unique multi-electrode enzyme functionalization protocol allowed for a wider paraoxon sensing range (four orders of magnitude: 1 nM - 10 µM) than one electrode alone. The flow cell platform biosensor was also tested in real-world samples (soil slurry) and demonstrated a signal recovery of approximately 93.5% and 91.5% for soil slurry samples spiked with 10 nM and 1 µM paraoxon concentration respectively. Hence these thin-film E-IML NPGL patterning and synthesis techniques could be useful for a wide variety of applications including electrochemical sensors, supercapacitors, batteries, fuel cells, energy harvesters, triboelectric nanogenerators, and membranes. This work was been published in the Journal of Materials Chemistry C. It should be noted that this publication made the front cover of the journal. We have also made great progress on developing a pumpless open microfluidic strategy to divert a single fluid sample to distinct regions where electrochemical biosensors can be printed. This simple, printed all-graphene open microfluidic approach will allow us to create low-cost fluidics that can be used to split a single fluid sample to multiple pesticide biosensors. This will allow us to monitor, for example, different classes of pesticides such as herbicides, insecticides, and fungicides from a single water sample; this open microfluidic will enable multiplexed sensing of pesticides. This will be vital to mapping large areas of a watersheds and farmland for pesticide contamination which is the ultimate goal of this project. More specifically, we reported the first all graphene-based open microfluidics through a scalable, rapid laser patterning technique. Graphene, a type of 2-dimensional (2D) carbon material, has been explored for diverse applications including energy storage, thermal management, filtration, and biosensing, due to its unique and advantageous properties (e.g., high electrical and thermal conductivity, surface area, as well as mechanical and thermal stability). Recently, the surface wettability of graphene has been shown to be tunable via selective graphene growth on patterned silicon substrates with microwave plasma chemical vapor deposition, solvent dispersion, and rapid-pulsed laser annealing. We present a laser scribing technique that uses a CO2 laser to scribe micron sized grooves into spin coated graphene flake films on flexible substrates [e.g., Polyethylene terephthalate (PET)]. The spin coated graphene is first made hydrophilic by treating the surface within an oxygen plasma environment. Next, a CO2 laser is used to pattern micron scale grooves into the graphene to form superhydrophobic regions (water contact angle ~ 160º) that act as fluid flow channel boundaries for the open microfluidic tracks. These all-graphene open microfluidic tracks are capable of transporting liquid droplets with a velocity of 20 mm/s on a level surface and uphill at elevation angles of 7º. All manufacturing steps (graphene coating, plasma treatment, and laser scribing) can be performed outside of a cleanroom environment. Furthermore, channel designs can be easily created and modified with computer aided design (CAD) software, which does not require a mask nor a mold. Hence, this novel all-graphene open microfluidic manufacturing technique is economical and amenable to scalable manufacturing, which is highly applicable across diverse fluid transport applications. This work has been published in the journal Nanoscale Horizons (impact factor = 9.972) and it should be noted that this publication made the front cover of the journal. Moreover, we have developed new innovations that have been incubated in part from the funding, techniques, and ideas generated from this USDA-NIFA grant. In particular, we have developed our first aerosol jet printed graphene electrochemical sensor. Aerosol jet printing (AJP) is a direct-write additive manufacturing technique that eliminates the need for masks, stencils, or hybrid techniques to produce patterned circuits with high spatial resolution. High-resolution lines with widths less than 50 μm can be achieved by AJP, which consequently enables a wide variety of components in printed electronics. Additionally, AJP is a more versatile printing technology as a wider range of inks can be used without the concerns of piezoelectric inkjet nozzle clogging. Due to minimal constraints on ink properties, AJP can be used to print diverse materials, ranging from ceramics to carbon nanomaterials to organic semiconductors. To this end, AJP graphene may be a more viable option for pesticide sensing than our previous inkjet printed graphene sensors. Hence, this technology could be applied to numerous electrochemical applications that require low-cost electroactive circuits that are disposable and/or flexible. This work has been published in the journal ACS Applied Materials & Interfaces (impact factor = 8.758). Another innovation that has been developed from this grant is the development of laser-induced graphene electrodes for pathogen detection. These laser-induced graphene electrodes may present a less complex method to create graphene electrodes then printing them because they do not require ink formulation and post-print annealing. Therefore, they may be the option we pursue in creating multiplexed electrochemical pesticide biosensors in the future. The developed laser induced graphene electrodes were functionalized with antibodies for food-borne pathogen detection. After functionalization with Salmonella antibodies, the LIG biosensors were able to detect live Salmonella in chicken broth across a wide linear range (25 to 105 CFU mL-1) and with a low detection limit (13 ± 7 CFU mL-1; n = 3, mean ± standard deviation). These results were acquired with an average response time of 22 min without the need for sample preconcentration or redox labeling techniques. Moreover, these LIG immunosensors displayed high selectivity as demonstrated by nonsignificant response to other bacteria strains. These results demonstrate how LIG-based electrodes can be used for electrochemical immunosensing in general and, more specifically, could be used as a viable option for rapid and low-cost pathogen detection in food processing facilities before contaminated foods reach the consumer. This work has been published in the journal ACS Sensors (impact factor = 6.944) it should be noted that this publication made the front cover of the journal.

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: L. S. Hall, Doh-Gyu Hwang, B. Chen, B. Van Belle, Z.T. Johnson, J. A. Hondred, C.L. Gomes, Michael D. Bartlett, J. C. Claussen, All-graphene-based open fluidics for pumpless, small-scale fluid transport via laser-controlled wettability patterning, Nanoscale Horizons, 6, 24-32, (2020). - COVER ARTICLE
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: R.R.A. Rainer, R. G. Hjort, E. L. Reis, N.F.F. Soares, E.S. McLamore, J.C. Claussen*, C.L. Gomes*, Laser induced graphene electrochemical immunosensors for rapid and label-free monitoring of Salmonella enterica in chicken broth, ACS Sensors, 5, 7, 19001911, (2020).  COVER ARTICLE


Progress 03/01/19 to 02/29/20

Outputs
Target Audience:During this fourth year of the project the target audience that we reached included experts in the field, interested industry representatives, and the general public. Researchers in the field were reached through the five journal articles that we published from this project but also were reached through invited research seminars at The University of Wisconsin, William Penn University, Iowa State University, and the Global Insurance Symposium as well as through annual conferences associated with the American Society of Mechanical Engineers (ASME), American Chemical Society (ACS), and SPIE Defense and Commercial Sensing (DCS). The citations for these research presentations are given in the products section of this progress report. Moreover, the seminar talk at the Global Insurance Symposium in Des Moines included industry experts interested in agricultural technology. In particular the industry experts were interested in how the sensors in this project could be deployed to warn of pesticide drift and water/soil contamination so remedial action could take place before further environmental damage (i.e., pollution of drinking water supplies) could take place. Finally, the results of this research were disseminated to the general public through numerous press releases. In November of 2019, the National Institute of Food and Agriculture in Research and Science Technology posted an article on our printed graphene-based biosensors titled, "New Nanosensor Detects Microscopic Contaminants in Water". These press releases were consequently were picked up and broadcast through a variety of other media outlets including scientific outlets such as Nano.gov, Graphene-Info, and The Graphene Councile but also agricultural based outlets that catered to those associtated with the agribusiness. For example, The Land ran an article on this research titled 'Nanostructured Biosensors Detect Pesticide, Help Preserve Environment'. The Land is a weekly agriculture-rural life publication printed in Mankato, Minn., since 1976 that serves farmers, ranchers, rural residents and agribusinesses across the entire state of Minnesota and northern Iowa. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Note that we have had the opportunity to train 1 postdoc, 2 graduate students and 3 undergraduate students through this last year of the project. One of the graduate students continued working on this project full-time in Dr. Claussen's lab while the other graduate student worked at the US Naval Research Laboratory with Dr. Medintz through a summer internship funded by this project. The graduate student in Dr. Claussen's laboratory was able to acquire expertise in biosensing and graphene printing while the student in Dr. Medinitz's lab learned how to synthesize enzymes for this project. The graduate student in Dr. Claussen's laboratory successfully graduated this year. However, before he left, this graduate student was able to train in a new graduate student that was recruited from William Penn University. Therefore, the knowledge gained from this project was successfully transitioned to a new student so that the progress made could continue on this project and future projects associated with pesticide biosensing. Also, both the previous and new graduate student working on this project in Dr. Claussen's laboratory were able to train 3 undergraduate students during the past year to work on this project. These undergraduate research experiences allow these students the opportunity to gain valuable laboratory experience and act an opportunity to for these students to see if they would like to continue their education in graduate school. We were also able to continue hosting a Fulbright Scholar from Ukraine to work on this project this last year. The stiped of the postdoc was covered through the Fulbright Scholar program but the materials he used to complete his research were funded from this project. This postdoc had a strong background in electrochemical biosensing and was able to provide valuable expertise in both the functionalization of the graphene electrodes with enzymes and in the testing protocols themselves. This postdoc was to increase the knowledge of the graduate student working on this project in Dr. Claussen's laboratory and was able to train and mentor our new graduated student working on this project as well as the 3 undergraduate students. How have the results been disseminated to communities of interest?The main results of this project were disseminated through 4 peer-reviewed journal article publications, 3 invited conference talks, and 3 invited university presentations, and 1 industry sponsored seminar. One of the journal articles made the front cover of the journal titled Journal of Materials Chemistry C. All of these venues allowed the PI to interact with the greater research communities in biosensors and nanomaterials to disseminate the results of this work, gain valuable feedback, and open the door for future collaborations. These manuscripts and invited talks are given listed in the 'products' and 'other products portion of this report. Unique to this year was the industry sponsored event to Insurance companies and other industry experts. Finally, the results of this research were disseminated to the general public through numerous press releases. One of the more notable press releases was a blog post by USDA-NIFA titled, "New Nanosensor Detects Microscopic Contaminants in Water". This blog post highlighted our work on graphene-based pesticide biosensors and was in turn posted on various news outlets. What do you plan to do during the next reporting period to accomplish the goals?This year was very productive for us in that we were able to complete the fabrication of the printed graphene and nanoporous gold leaf (NPGL) biosensor that was capable of selectively monitoring organophosphates in complex soil and water samples. The graphene biosensors were very sensitive (0.6 nM) and hence capable of monitoring organophosphate pesticides at levels significantly lower than the EPA drinking water limit (24 nM). The NPGL biosensors were adhered to a 3D printed flow cell and tested in real-world samples (soil slurry). The sensors demonstrated a signal recovery of approximately 93.5% and 91.5% for soil slurry samples spiked with 10 nM and 1 μM paraoxon concentration respectively. Overall these NPGL sensors could monitor organophosphates over a very wide sensing range (5 orders of magnitude: 10 nM to 1 µm). Therefore, these sensors are not only well-suited for use with field samples (soil slurries collected from a farm field or water samples collected from a field drain tile) where concentrations of pesticides would be expected to be highly concentrated, they could also be used to rapidly assess such pesticide concentrations in drinking water where the pesticide concentration should be low/disperse. During the last year of this project we have also had the opportunity to complete the first prototype of the multiplexed, printed pesticide biosensor where multiple pesticides could be analyzed from a single sample. This sensor was completed with NPGL electrodes that could adhere to and seal a 3D printed flow cell. In this way, a field water or soil slurry sample could be introduced to the flow cell so that multiple pesticides could be monitored in the field without the need to test the samples back in the laboratory with expensive and time-consuming equipment. These prototype NPGL sensors were functionalized with one enzyme (acetylcholinesterase), albeit at different concentrations on each electrode, in order to monitor organophosphates across a very wide linear sensing range as mentioned in the previous paragraph. In the no-cost extension part of the project we aim to functionalize these electrodes with a variety of different enzymes so that different classes of pesticides, including insecticides and herbicides, can be monitored from a single field sample. Therefore, the project goals in this next year are the following: (1) complete a multiplexed pesticide biosensor complete with an accompanying flow cell so that both insecticides and herbicides can be monitored from a single field sample (water or soil slurries), and (2) provide a sensing protocol that researchers, farmers, or others can utilize so that they can make pesticide measurements in the field. Since we have completed the initial multiplexed biosensor and flow cell, we are confident that we will be able to complete the next stated goals in the last year of the project.

Impacts
What was accomplished under these goals? As mentioned in our previous project reports, we developed a new patterning technique [i.e., Inkjet Maskless Lithography (IML)] to form high resolution, flexible graphene films (line widths as small as 20 μm) that significantly exceeds current graphene inkjet printing resolution (line widths ~ 60 μm). We also demonstrated how these graphene electrodes fabricated with this IML technique can be made highly electrically conductive (sheet resistance changed from 25 M ohms / sq. to 10-25 ohms / sq.) with tunable surface wettability with our rapid pulse laser technique. Finally, we also demonstrated how laser-annealed, IML-printed graphene electrodes can be functionalized with the enzymephosphotriesterase (PTE) for selective sensing of organophosphates inreal samples (tap water, river water, and a soil slurry) down to a detection limit of 3 nM.The research goals for this last year of this project were to improve the sensitivity of the organophosphate sensing capability of the pesticide sensors and to demonstrate the ability to perform simultaneous monitoring of multiple pesticides (multiplexed biosensing). During this past year, we were able to improve the electrocatalytic activity and consequently the sensitivity of the pesticide biosensors by modifying the IML printing technique to induce micrsoscale 'divots' into the printed graphene. Macrosized pores (25-50 μm) were formed by utilizing salt crystals as porogens (hard templates) in the graphene ink while patterning, a process we refer to as Salt Impregnated Inkjet Maskless Lithography (SIIML). Additionally, microsized pores (100 nm - 2 μm) are etched into the graphene surface through CO2laser annealing, even on flexible heat sensitive substrates (PET). We demonstrate that SIIML is an effective tool for enhancing the electrochemical activity and pesticide sensitivity of the graphene through functionalization with the enzyme acetocholine esterase (ACHE). Graphene electrodes with macrosized pores through salt impregnation outperformed their non macropore counterparts (sensitivity to acetocholine of 28.3 μA nM−1 vs. 13.3 μA nM−1). The SIIML graphene ACHE sensor had a wide linear sensing range (10 nM to 500 nM), low limit of detection (0.6 nM), and high sensitivity (12.4 nA nM−1) to paraoxon (a model organophosphate). This research was published in the journal Nanoscale Horizons (9.391). We have also made significant progress in transitioning our printed sensors into a multiplexed pesticide biosensors in this year of the project were the biosensor will be integrated with a flow cell to test multiple pesticides with one field sample. In order to make the electrodes adhere to adhesive Kapton®, the electrodes were created with gold leaf in lieu of graphene. In summary this work developed a new manufacturing technique we coined Etching Inkjet Maskless Lithography (E-IML) to synthesize and pattern NPGL and metal leaf materials (thickness ~100 nm) for flexible electronics. E-IML utilizes the versatility of an inkjet printer to pattern electrodes for rapid prototyping, even on flexible substrates (polyimide). We demonstrated how NPGL electrodes can be synthesized and patterned from gold/silver leaf material with E-IML and dealloyed (silver removed) via electrochemical etching. These combined E-IML patterning and electrochemical dealloying techniques can pattern NPGL with feature and pores sizes down to approximately 25 nm and 5 nm respectively. The resultant high resolution and high surface area NPGL circuits demonstrate excellent electroactivity and high enzyme loading capability that consequently improves electrochemical biosensing performance. Additionally, a pseudo-reference electrode was E-IML patterned from silver leaf and chlorinated with a diluted bleach solution to make a Ag/AgCl electrode that could be used with NPGL working and counter electrodes for 3-electrode electrochemical biosensing. These 3-electrode electrochemical biosensors were patterned on adhesive polyimide films for use as disposable peel-and-stick tape biosensors or wearable sticker biosensors. In order to demonstrate the utility of the peel-and-stick biosensors, a disposable tape pesticide biosensor and reusable 3D printed flow cell were developed for organophosphate detection in soil samples. Multiple NPGL working electrodes were fabricated on single devices so that that each electrode could be functionalized with distinct concentrations of the enzyme acetylcholinesterase (ACHE). Paraoxon (a model organophosphate) sensing results demonstrated a low detection limit (0.53 pM) and high sensitivity (376 nA/nM). The unique multi-electrode enzyme functionalization protocol allowed for a wider paraoxon sensing range (four orders of magnitude: 1 nM - 10 µM) than one electrode alone. The flow cell platform biosensor was also tested in real-world samples (soil slurry) and demonstrated a signal recovery of approximately 93.5% and 91.5% for soil slurry samples spiked with 10 nM and 1 µM paraoxon concentration respectively. Hence these thin-film E-IML NPGL patterning and synthesis techniques could be useful for a wide variety of applications including electrochemical sensors, supercapacitors, batteries, fuel cells, energy harvesters, triboelectric nanogenerators, and membranes. This work was been published in the Journal of Materials Chemistry C. It should be noted that this publication made the front cover of the journal (November issue 2020). Moreover, we have developed new innovations that have been incubated in part from the funding, techniques, and ideas generated from this USDA-NIFA grant. In particular, we have developed our first aerosol jet printed graphene electrochemical sensor. Aerosol jet printing (AJP) is a direct-write additive manufacturing technique that eliminates the need for masks, stencils, or hybrid techniques to produce patterned circuits with high spatial resolution. High-resolution lines with widths less than 50 μm can be achieved by AJP, which consequently enables a wide variety of components in printed electronics. Additionally, AJP is a more versatile printing technology as a wider range of inks can be used without the concerns of piezoelectric inkjet nozzle clogging. Due to minimal constraints on ink properties, AJP can be used to print diverse materials, ranging from ceramics to carbon nanomaterials to organic semiconductors. To this end, AJP graphene may be a more viable option for pesticide sensing than our previous inkjet printed graphene sensors. Hence, this technology could be applied to numerous electrochemical applications that require low-cost electroactive circuits that are disposable and/or flexible. This work has been published in the journal ACS Applied Materials & Interfaces (impact factor = 8.758). Another accomplishment of this project was the development of stamped graphene electrodes for electrochemical biosensing. These stamped electrodes do not need ink binders or annealing processing. Hence these graphene electrodes were explored as a potential alternative to the inkjet and aerosol printed graphene electrodes in order to potentially find a more scalable wrote to producing pesticide sensors than relying on direct write methods that are more geared towards rapid prototyping and not mass production. When tested on flexible substrates, the expanded graphite laminates demonstrated excellent adhesion and durability during testing. These properties make the electrodes adaptable to a variety of tests for field-based or wearable sensing applications.This work was published in the journal Microchimica Acta (Impact Factor of 6.232).

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: J.A. Hondred, Z., T. Johnson,! J. C. Claussen, Nanoporous gold peel-and-stick biosensors created with etching inkjet maskless lithography for integration with microfluidics and electrochemical pesticide monitoring, Journal of Physical Chemistry C, - COVER ARTICLE Journal of Materials Chemistry C, 2020, 8, 11376  11388.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: J. A. Hondred, I. L. Medintz, J. C. Claussen, Enhanced electrochemical biosensor and supercapacitor with 3D porous architectured graphene via salt impregnated inkjet maskless lithography, Nanoscale Horizons, 4, 735-746 (2019).
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: K. Parate, S. V. Rangnekar, D. Jing, D. L. Mendivelso-Perez, S. Ding, E. B. Secor, E. A. Smith, J. M. Hostetter, M. C. Hersam, J. C. Claussen, Aerosol-jet-printed graphene immunosensor for label-free cytokine monitoring in serum, ACS Applied Materials, 12, 7, (2020).
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: L.R. Stromberg, J.A. Hondred, D. Sanborn, D.Mendivelos-Perez, S. Ramesh, I.V. Rivero, J. Kogot, E. Smith, C. Gomes, J.C. Claussen, Stamped multilayer graphene laminates for disposable in-field electrodes: application to electrochemical sensing of hydrogen peroxide and glucose, Microchimica Acta, 186, 533, (2019).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: J.C. Claussen, J.A. Hondred, I.L. Medintz, American Chemical Society (ACS) Nanotechnology, San Diego CA, Printed and laser induced graphene electrochemical sensors for in-field pesticide and fertilizer ion monitoring, Aug. (2019).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: J.C. Claussen, J.A. Hondred, I.L. Medintz, SPIE Defense and Commercial Sensing (DCS) Annual Conference, Baltimore MD, Printed and laser induced graphene electrochemical biosensors for in-field soil and food monitoring, Apr. (2019).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: J.C. Claussen, J.A. Hondred, I.L. Medintz, ASME International Mechanical Engineering Congress & Exposition (IMECE), Salt Lake City, UT, Printed Graphene Biosensors and Fluidics for Environmental and Health Monitoring in the Field, Nov. (2019).


Progress 03/01/18 to 02/28/19

Outputs
Target Audience: During this third year of the project the target audience that we reached included experts in the field, interested industryrepresentatives, and the general public. Researchersin the field were reached through the four journal articles that we published from this project but alsowere reached through invited research seminars at Rice University, as well as through conferences associated with the Institute of Food Technologist (IFT), American Chemical Society (ACS), World Congress on Biosensors (Elsevier), and the Conference of Food Engineering (CoFE). The citations for these research presentations are given in the productssection of this progress report. Moreover, these research conferences, especially IFT and CoFE, also included discussions with industry represeentatives. Finally, the results of this research were dissiminated to the general public through numerous press releases. One of the more notable press releases wasin the form of a podcast put togethery by Brigham Young University (BYU) Radio.Another press releaseinclude those from the Iowa State University Foundation regarding ourrobust printable graphene biosensors that we have been developing for this project. These press releases were consequently were picked up and broadcast through a variety of other media outlets. Details and links to these press releases are given below. News story from the Iowa State University Foundation regarding ourthe robust printable graphene biosensors that we have been developing for this project. The title of this news piece is 'Wash and Wear Electronics' since the graphene electrodes can withstand wasing and bending/flexing and still can retain their electrical conductivity.https://www.foundation.iastate.edu/s/1463/images/editor_documents/news/your_iowa_state/2018/newsletter_may_v2_email.pdf Podcast from Brigham Young University Interviews Professor Claussen about the robust printable graphene biosensors that we have been developing for this project.http://web.me.iastate.edu/claussen/videos_and_audio/BYU_Radio.mp3 Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Note that we have had the opportunity to train 1 postdoc, 2 graduate students, and 3 undergraduate students through this last year of the project. One of the graduate students continued working on this project full-time in Dr. Claussen's lab while the other graduate student worked at the US Naval Research Laboratory with Dr. Medintzy through a summer internship funded by this project. The graduate student in Dr. Claussen's laboratory was able to acquire experise in biosensing and graphene printing while the student in Dr. Medenitz lab learned how to synthesize enzymes for this project. We were also able to aquire a Fulbright Scholar from Ukraine to work on this project this last year. The stiped of the postdoc was covered through the Fulbright Scholar program but the materials he used to complete his research were funded from this project. This postdoc had a strong background in electrochemical biosensing and was able to provide valuable expertise in both the functionalization of the graphene electrodes with enzymes and in the testing protocols themselves. This postdoc was to increase the knowledge of the graduate student working on this project in Dr. Claussen's laboratory and was able to train and mentor 3 undergraduate students during the past year to work on this project. How have the results been disseminated to communities of interest? The main results of this project were disseminated through 4 peer-reviewed journal article publications, 2 conference posters, 3 invited conference talks, and 1 invited University talk. All of these venues allowed the PI to interact with the greater research communities in biosensors and nanomaterials to disseminate the results of this work, gain valuable feedback, and open the door for future collaborations. These manuscripts and invited talks are given listed in the 'products' and 'other products portion of this report. Finally, the results of this research were disseminated to the general public through numerous press releases. Some of the more notable press releases where in the form of a podcast through Brigham Young University radio as well as a news piece through the Iowa State University Foundation. The details regarding these news pieces are given below. These are two good examples of how our research is being disseminated to the general public. News story from the Iowa State University Foundation regarding ourthe robust printable graphene biosensors that we have been developing for this project. The title of this news piece is 'Wash and Wear Electronics' since the graphene electrodes can withstand wasing and bending/flexing and still can retain their electrical conductivity.https://www.foundation.iastate.edu/s/1463/images/editor_documents/news/your_iowa_state/2018/newsletter_may_v2_email.pdf Podcast from Brigham Young University Interviews Professor Claussen about the robust printable graphene biosensors that we have been developing for this project.http://web.me.iastate.edu/claussen/videos_and_audio/BYU_Radio.mp3 What do you plan to do during the next reporting period to accomplish the goals? This year was very productive for us in that we were able to complete the fabrication of the printed graphene biosensor that was capable of selectively monitoring organophosphates in complex soil and water samples. These biosensors were very sensitive (0.6 nM) and hence capable of monitoring organophosphate pesticides at levels significantly lower than the EPA drinking water limit (24 nM). Therefore, this sensor is not only well-suited for use with field samples (soil slurries collected from a farm field or water samples collected from a field drain tile) where concentrations of pesticides would be expected to be highly concentrated, it could also be used to rapidly assess such pesticide concentrations in drinking water where the pesticide concentration should be low/disperse. During the last year of this project we have also had the opportunity to almost complete the first prototype of the multiplexed, printed pesticide biosensor where multiple pesticides could be analyzed from a single. The creation of this multiplexed biosensor would complete the goals of this project. We have therefore asked for a no-cost project extension to complete and optimize this multiplex biosensor. We have received an additional year through the no-cost project extension. Therefore the project goals in this next year are the following: (1) complete the initial prototype of the printed multiplexed pesticide biosensor complete with an accompanying flow cell so that field samples (water or soil slurries) can be rapidly assessed, (2) provide a sensing protocol that researchers, farmers, or others can utilize so that they can make pesticide measurements in the field, (3) optimize the design of the sensor system mathematically through the help of co-PD Eliot Winer, (4) complete a final, optimized multiplexed pesticide biosensor. Since we have just about completed the intial multiplexed biosensor (goal 1 above), we are confident that we will be able to complete the next 3 stated goals in the last year of the project.

Impacts
What was accomplished under these goals? As mentioned in our previous project reports, we developed a new patterning technique [i.e., Inkjet Maskless Lithography (IML)] to form high resolution, flexible graphene films (line widths as small as 20 μm) that significantly exceeds current graphene inkjet printing resolution (line widths ~ 60 μm). We also demonstrated how these graphene electrodes fabricated with this IML technique can be made highly electrically conductive (sheet resistance changed from 25 M ohms / sq. to 10-25 ohms / sq.) with tunable surface wettability with our rapid pulse laser technique. Finally, we also demonstrated how laser-annealed, IML-printed graphene electrodes can be functionalized with the enzymephosphotriesterase (PTE) for selective sensing of organophosphates inreal samples (tap water, river water, and a soil slurry) down to a detection limit of 3 nM.The research goals for this last year of this project were to improve the sensitivity of the organophosphate sensing capability of the pesticide sensors and to demonstrate the ability to perform simultaneous monitoring of multiple pesticides (multiplexed biosensing). During this past year, we were able to improve the electrocatalytic activity and consequently the sensitivity of the pesticide biosensors by modifying the IML printing technique to induce micrsoscale 'divots' into the printed graphene. This work was the major focus of Objective 2 of this project. More particularly, macrosized pores (25-50 μm) were formed by utilizing salt crystals as porogens (hard templates) in the graphene ink while patterning, a process we refer to as Salt Impregnated Inkjet Maskless Lithography (SIIML). Additionally, microsized pores (100 nm - 2 μm) are etched into the graphene surface through CO2laser annealing, even on flexible heat sensitive substrates (PET). We demonstrate that SIIML is an effective tool for enhancing the electrochemical activity and pesticide sensitivity of the graphene through functionalization with the enzyme acetocholine esterase (ACHE). Graphene electrodes with macrosized pores through salt impregnation outperformed their non macropore counterparts (sensitivity to acetocholine of 28.3 μA nM−1 vs. 13.3 μA nM−1). The SIIML graphene ACHE sensor had a wide linear sensing range (10 nM to 500 nM), low limit of detection (0.6 nM), and high sensitivity (12.4 nA nM−1) to paraoxon (a model organophosphate). This research was published in the journal Nanoscale Horizons (9.391). This research also permitted us to submit a provisional patent on this SIIML technique as noted in the products section of this report. We have also made significant progress in transitioning these printed graphene sensors into a multiplexed pesticide biosensor integrated with a flow cell to test multiple pesticides with one field sample. This work was the focus of Objective 3 of this project. The graphene electrodes were printed on the adhesive side of Kapton® tape, laser processed to create highly sensitive and flexible electrochemical electrodes, and finally functionalized with enzymes [e.g., phosphotriesterase (PTE), acetylcholinesterase (ACHE)] via covalent attachment to the oxygenated species of the graphene using carbodiimide chemistry. These printed biosensors are then adhered to the open channels of a 3D printed flow cell via the adhesive surrounding the graphene on the tape. The flow cell is expected to increase the accuracy and sensitivity of the sensors system as it permits precise sample fluid control to the sensor surfaces and facilitates sensor-pesticide interactions (decreases analyte diffusion time). The first manuscript on this multiplexed pesticide biosensor approach should be published later this year. Moreover, we have developed new innovations that have been incubated in part from the funding, techniques, and ideas generated from this USDA-NIFA grant. In particular, we have been able to demonstrate how a UV laser technique can be used to convert polyimide into laser induced graphene (LIG) that can be functionalized with ion selective membranes. These sensors are capable of selectively and electrochemically sensing fertilizer ions (ammonium and nitrate) in soil columns.On a broader scale, these LIG-based electrodes are comparable to the recent trend of creating low-cost carbon-based electrodes via screen printing and inkjet printing solution-phase flakes in lieu of developing electrodes from more costly CVD graphene synthesis processes. However, these solution-phase graphene printing techniques require metal screen masks, expensive printing equipment, development of a jettable ink, or postprint annealing processes that have complicated their fabrication. The approach described herein represents a one-step, low-cost manufacturing pathway for LIG electrodes and is the first example using LIG for use in ion sensing. Additionally, no metals, such as metallic nanoparticles, were needed to improve the electroreactive nature of the electrode, hence these LIG electrodes are amenable to scalable roll-to-roll manufacturing and suitable for use in disposable sensor technologies. Such LIG may be quite useful for making low-cost, disposable pesticide biosensors which is a focus of this project.This research was published in ACS Applied Materials & Interfaces (Impact Factor 8.097). We have also demonstrated how the laser-annealed printed graphene can be functionalized with a molecular imprinted polymer to selectively and electrochemically sense cotinine in saliva to monitor human nicotine/tobacco. Such nanostructuring of the SPCE was necessary to obtain measurable cotinine readings with this MIP functionalization approach.Due to the high sensitivity of the biosensor, the developed MIP biosensor could also be used to help distinguish between smoke ingestion from actual smokers or from secondhand smoke. Such information could be useful to pass legislation that ensures high smoke-free air quality in public places like hospitals, office buildings or schools as well as to pass guidelines for smoking in private locations. Therefore, this graphene electrode could be a possible candidate for pesticide biosensing when properly functionalized with an appropriate enzyme.This work was published in the journal of Sensors and Actuators B: Chemical (Impact Factor of 5.667). Finally, we demonstrate how the inkjet printing techniques developed herein can be used to print bioflavonoid extract for enhanced biophotovoltaics and pH sensitive thin films. This project demonstrated how versatile the inkjet printing process can be in developing a variety of printed biomaterials for biosensing. This research was published in the journal Biotechnology Progress (Impact Factor 1.947).

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: J. A. Hondred!, I. L. Medintz, J. C. Claussen*, Enhanced electrochemical biosensor and supercapacitor with 3D porous architectured graphene via salt impregnated inkjet maskless lithography, Nanoscale Horizons, 4, 735-746 (2019).
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: K. Parate, C. Karunakaran, J.C. Claussen, Electrochemical cotinine sensing with a molecularly imprinted polymer on a graphene-platinum nanoparticle modified carbon electrode towards cigarette smoke exposure monitoring, Sensors and Actuators B: Chemical, 287, 165-172, (2018).
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: N. T. Garland, E. S. McLamore, N. D. Cavallaro, D. Mendivelso-Perez, E. A. Smith, D. Jing, J. C. Claussen*, B. Flexible Laser-Induced Graphene for Nitrogen Sensing in Soil, ACS Applied Materials and Interfaces, 10, 45, (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: J.A. Hondred, J.C. Breger, S.R. Das, S.A. Walper, I.L. Medintz, J.C. Claussen*, Graphene-Based Electrochemical Biosensors Manufactured via Inkjet Maskless Lithography for Rapid and Sensitive Monitoring of Pesticide Levels in the Soil, World Congress on Biosensors, Miami FL, (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: J.A. Hondred, J.C. Breger, S.R. Das, S.A. Walper, I.L. Medintz, J.C. Claussen, In-field, disposable soil sensor for monitoring pesticide levels via laser annealed graphene electrodes, Iowa State University - Graduate and Professional Student Senate (GPSS) Conference, Ames IA, (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Invited Conference Presentation - Jonathan Claussen American Chemical Society (ACS) Midwest Regional Meeting, Ames, IA, Printed and Laser Induced Graphene for In-Field Electrochemical Biosensing. Oct. 2018
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Invited Conference Presentation - Jonathan Claussen Conference of Food Engineering (CoFE), Minneapolis, MN, Low-cost, Flexible Electrochemical Biosensors with Printed and Laser Induced Graphene, Sept. (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Invited Conference Presentation - Jonathan Claussen Institute of Food Technology (IFT), Chicago IL, Electrochemical foodborne pathogen and soil health monitoring with printed graphene biosensors, July (2018)
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: A. Demirbas, K. Groszman, M. Pazmino, R. Nolan, D.C. Vanegas, B. Welt, J.A. Hondred!, N.T. Garland!, J.C. Claussen, E.S. McLamore*, Cryoconcentration of bioflavonoid extract for enhanced biophotovoltaics and pH sensitive thin films, Biotechnology Progress, 34, 1, (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: J.A. Hondred, J.C. Breger, N.T. Garland, S.A. Walper, I.L. Medintz, J.C. Claussen, Printed Graphene biosensors for pesticide monitoring in the farm field, Nanoscale Science and Engineering for Agriculture and Food Systems  Gordon Research Conference, Mt. Holyoke MA, (2018)


Progress 03/01/17 to 02/28/18

Outputs
Target Audience:During this second year of the project the target audience that we reached included experts in the field, interested industry representatives, and the general public. Experts in the field where reached through invited research seminars at Iowa State University, industry seminar at 3M at ther R&D headquarters in St. Paul MN,as well as through conferences associated with theInstitute of Food Technologist (IFT), Materials Research Society (MRS), American Society of Mechanical Engineers (ASME), Nanotech TechConnect World Expo. The citations for these research presentations are given in the products and other products section of this progress report.Moreover, these research conferences, especially IFT and NanoTech, also included discussions with industry represeentatives. Finally, the results of this research were dissiminated to the general public through numerous press releases. Some of the more notable press releases is in the form of a vidoe that made the local Des Moines Iowa 6pm news. Note that Des Moines is the capital city of Iowa and the largest city in Iowa so these news piece, put together for the lay person, should have reached a broad auidence. Also our research was highlighted in theAnnual Report of the National Nanotechnology Initiative which should particularly reach lawmakers. Other press releases include thos from Iowa State University regarding are research on creating superhydrophobic printed graphene that also made the front cover of the Journal of Nanoscale. These press releases from Iowa State University were consequently were picked up and broadcast through a variety of other media outlets. Details and links to these press releases are given below. Press Releases (Video and Written Articles) Jacob Pelko from Channel 5 News in Des Moines visits our lab and reports on our printed graphene biosensors. Watch the news clip that made the 6 o'clock news here.http://web.me.iastate.edu/claussen/videos_and_audio/channel_5.mp4 Read about our Printed Graphene Pesticide Biosensor Research in the Annual Report of the National Nanotechnology Initiative - see "Smart Technology for Food Technology on Page 8".http://www.nano.gov/sites/default/files/pub_resource/NNI-FY18-Budget-Supplement.pdf Engineers develop flexible, water-repellent graphene circuits for washable electronics, Iowa State University -https://www.news.iastate.edu/news/2018/01/23/washableelectronics. Note thisresearch was also highlighted on the front cover of the journal Nanoscale" Our inkjet printed graphene research featured in the 2017 summer edition (vol.6, no.2) of the Iowa State University Foundation magazine under the article titled "The Next Big Breakthrough"http://www.foundation.iastate.edu/s/1463/images/editor_documents/forward/forward_summer_2017.pdf Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?As noted previously in this report, the Jonathan Claussen and the graduate students associated with this project were able to attend and present this research at multiple conferences including those sponsored by the Materials Research Society (MRS), American Society of Mechanical Engineering (ASME), NanoTech Tech Connect World Innovation, Institute of Food Technologists (IFT), and smaller local conferences at Iowa State University. These conferences have helped provide valuable learning on the latest key developments in the field and have facilitated the dissemination of knowledge to other researchers in the field. How have the results been disseminated to communities of interest?The main results of this project were diseminated three 3 publications as previously reported as well as through invited talks at a US University, industry, and 3 invited conference talks, and 4 conference poster presentation.All of these venues allowed the PI to interact with greater research communities in biosensors and nanomaterials to dissimenate the results of this work, gain valuable feedback, and open the door for future collaborations. These talks were listed under other products but are listed again below for completeness. University Talks Iowa State University, Dept. of Food Science & Human Nutrition , Ames IA, "Printed graphene electrodes for in-field electrochemical biosensing applications", January (2018) Iowa State University, Dept. of Chemical & Biological Engineering, Ames IA, "Fabrication and functionalization of flexible, printed nanomaterials for biosensing & energy harvesting", January (2018) Industry Talk 3M Tech Forum, St. Paul MN, "Flexible graphene circuits for biosensing and cellular differentiation", August (2017) Invited Conference Talk 2017 MRS Fall Meeting & Exhibit - Materials Research Society, Boston MA, "Scalable manufacturing of graphene-based biosensors for in-field fertilizer and pesticide sensing", Symposium: Tools and Sensors for Plant and Soil Characterization, December (2017) 2017 ASME Congress and Exposition, Tampa FL, "Inkjet printed graphene on flexible substrates with laser annealing for electrochemical biosensing and nerve cell regeneration", Topic 11-7 NanoTech Conference & Expo, Washington DC, "Scalable manufacturing of graphene-based biosensors functionalized with enzyme Nanoparticle bioconjugates for rapid, in-field pesticide monitoring" May (2017) Conference Posters J.A. Hondred, J.C. Breger, S.R. Das, S.A. Walper, I.L. Medintz, J.C. Claussen, "In-field, disposable soil sensor for monitoring pesticide levels via laser annealed graphene electrodes", MRS Fall Meeting & Exhibit, Boston MA, (2017) - First Place Graduate Student Poster Competition J.A. Hondred, L.R. Stromberg, J.C. Breger, I.L. Medintz, J.C. Claussen*, "In-field, disposable soil sensor for monitoring pesticide levels via laser annealed graphene electrodes", Nano@IAState - First Annual Conference on Nanotechnology, Ames IA, (2017) - First Place Graduate Student Poster Competition J.A. Hondred, J.C. Breger, N.T. Garland, S.A. Walper, I.L. Medintz, J.C. Claussen, "Scalable manufacturing of graphene-based biosensors for soil management and food safety", Institute of Food Technologists (IFT) Meeting, Las Vegas NV, (2017) S.R. Das, Q. Nian, G.J. Cheng, J.C. Claussen, "Boosting the electrical conductivity and 3D nanostructuring of inkjet printed graphene with pulsed laser irradiation", Materials Research Society (MRS) Spring Exhibit & Meeting, Phoenix AZ, (2017) Finally, the results of this research were dissiminated to the general public through numerous press releases. Some of the more notable press releases is in the form of a vidoe that made the local Des Moines Iowa 6pm news. Note that Des Moines is the capital city of Iowa and the largest city in Iowa so these news piece, put together for the lay person, should have reached a broad auidence. Also our research was highlighted in theAnnual Report of the National Nanotechnology Initiative which should particularly reach lawmakers. Other press releases include thos from Iowa State University regarding are research on creating superhydrophobic printed graphene that also made the front cover of the Journal of Nanoscale. These press releases from Iowa State University were consequently were picked up and broadcast through a variety of other media outlets. Details and links to these press releases are given below. Press Releases (Video and Written Articles) Jacob Pelko from Channel 5 News in Des Moines visits our lab and reports on our printed graphene biosensors. Watch the news clip that made the 6 o'clock news here.http://web.me.iastate.edu/claussen/videos_and_audio/channel_5.mp4 Read about our Printed Graphene Pesticide Biosensor Research in the Annual Report of the National Nanotechnology Initiative - see "Smart Technology for Food Technology on Page 8".http://www.nano.gov/sites/default/files/pub_resource/NNI-FY18-Budget-Supplement.pdf Engineers develop flexible, water-repellent graphene circuits for washable electronics, Iowa State University -https://www.news.iastate.edu/news/2018/01/23/washableelectronics. Note thisresearch was also highlighted on the front cover of the journal Nanoscale" Our inkjet printed graphene research featured in the 2017 summer edition (vol.6, no.2) of the Iowa State University Foundation magazine under the article titled "The Next Big Breakthrough"http://www.foundation.iastate.edu/s/1463/images/editor_documents/forward/forward_summer_2017.pdf What do you plan to do during the next reporting period to accomplish the goals?This year of the project was a productive one for us. This year culminatinatedin developing a robust and selective pesticide biosensor with the low-cost, printed graphenecircuits that incorporated the use of enzymes produced from our subawardee from the US Naval Research Laboratory to monitor organophosphate pesticides within actual field samples (river water and soil slurrys). This culminating work completes a significant milestone in the last objective (Objective 3) of the proposal. As mentioned previously this biosensor was able to detect organophosphates with a detection limit of approximately 3 nM. This is indeed a low detection limit and definetly suitable for monitoring these pesticides at the point of application on produce or in the farm field. However, the EU has a drinking water limit for organophosphates of approximately 1 nM. Therefore our first goal we wish to accomplish in Year 3 is to improve the sensitivity of the graphene sensor so that it can reach this 1nM detection limit with field samples. We feel we can accomplish this by further nano/microstructuring the surface of the graphene. For our second goal in Year 3,we wish to demonstrate the ability to create mutliplexed sensing (sense more than one pesticide from a single water or soil sample). We accomplish this by creating muliple printed electrodes on a single substrate that will share a common printed reference electrode. Completing such a biosensor will enable the rapid and facile in field monitoring of a broad spectrum of pesticides byfarmers, environmentalists, and other researchers.

Impacts
What was accomplished under these goals? As mentioned in the progress report for Year 1 of this project,After this first year of project reporting we realized that more research focus needs to be on further developing the printed graphene electrodes so that they are suitable for robust pesticide sensing in the field. Consequently, at the end of that year we made the following goals for for the second year of the project which is being reported upon in this project report. Mainly the goals were made:1) improve the line resolution of the printed graphene electrodes, 2) tune the surface wettability of the graphene to superhydrophobic, and 3) develop methods to directly functionalize the graphene electrode surface with the enzyme phosphotriesterase developed from the US Naval Research Laboratory (NRL). These three objectives are important because a higher graphene line resolution (< 50 microns) will allow us to create more complex biosensor patterns in a smaller space to increase the multiplexing capability of the sensor (Objective 3). In other words more biosensors that can be printed in a smaller space and distinctly functionalized to montior different pesticides will be able to simutaneously react with a small soil and water field sample to give the end user to probe for multiple pesticides from a single sample. Secondly. converting the graphene to superhydrophobic in some locations will help prevent the surface from biofouling during actual in field sensing. Finally, successfully immbolizing the enzyme phosphotriesterase on the graphene surface will create the first prototype electrochemical pesticide biosensor for this project. The knowledge gained in this process will be used to further refine and multiplex the biosensor system. We are pleased to report that we did meet the goals we made for the first year of the project and where able to publish on all ofthese goals and were able to submit a related provisional patent. Goal 1: Improve the line resolution of the printed graphene electrodes We have developed a new patterning technique [i.e., inkjet maskless lithography (IML)] to form high resolution, flexible graphene films (line widths as small as 20 µm) that significantly exceeds current graphene inkjet printing resolution (line widths ~ 60 µm).IML uses an inkjet-printed polymer lacquer as a sacrificial pattern layer, viscous spin coated graphene, and a subsequent graphene lift-off to make the patterned films without the need for pre-fabricated stencils, templates or cleanroom technology such as photolithography. It should be noted that some researchers have demonstrated inkjet-printing photoresist as a protective mask,while others have inkjet-printed polymer layers for a sacrificial lift-off process, such as coffee-ring lithography and polymer microsieve pores. However, full patterning of high-resolution (< 25 µm) graphene circuits not been reported previously. Moreover, we have shown that after rapid pulse laser annealing IML printed graphene reaches an electrical conductivity much closer to printed metals (?/sq< 100). Such high conductivity is most likely do to the higher density of graphene in spin coated IML printed graphene than inkjet printed graphene. This concomitance of thickner printed graphene lines and higher resolution patterns has allowed us to improve the sensitivity of electrochemical pesticide biosensors as shown in our accomplishments in Goal 3 below. We were able to publish the details of the IML printed graphene for electrochemical sensor development in the journal ACS Nano (impact factor of13.709). Goal 2: Tune the surface wettability of the graphene to superhydrophobic We have also demonstrated that we can tune the power settings of the laser, that we showed in year 1 can anneal and grealty improve electrical conductivity and electroreactivity ofthe printed graphene, can be tuned to change the surface wettability of graphene. Thislaser process is also able to convert the inkjet-printed graphene to hydrophilic (water contact angle (WCA) ~ 45°) to hydrophobic (WCA ~ 110°), and to superhydrophobic (WCA ~ 155°) by tuning the energy denisty of the laser.In biosensing, high surface area can lead to a high amount of biorecognition agent immobilization and to a higher biosensor sensitivity, along with higher electrical conductivity. Moreover, supherhydrophobic electrodes have been shown more resistant to biofouling which may be crucial to creating a pesticide biosensor that can work in actual field water and soil samples.The results from this work were published in the journal article Nanoscale (7.233) and this manuscript made the front cover of the journal. Goal 3: Develop methods to directly functionalize the graphene electrode surface with the enzyme phosphotriesterase developed from the US Naval Research Laboratory (NRL). We have now developed a fully functional amperometric biosensor for the detection of organophosphate pesticides developed based on a printed graphene electrode (PGE) that has been nano/microstructured with post-print laser processing and electrodeposited platinum nanoparticles (PtNPs) as well as biofunctionalized with the enzyme phosphotriesterase (PTE) via glutaraldehyde cross-linking. The nano/microstructured printed graphene provides an effective transduction material for rapidly monitoring the oxidation of p-nitrophenol because of its high electrical conductivity, electroactive nature, and biocompatibility. The graphene transduction layer was further enhanced through laser annealing, which fused individual graphene flakes together, increased the electroactive surface area, and provided stable attachment locations for covalent enzyme functionalization with the increased superficial oxygen groups. The high surface area creates a hydrophobic biosensor that resists surface fouling by repelling nonspecific species from adsorbing on the electrode surface. The PtNPs were utilized to further increase the sensitivity of the biosensor by increasing the electroactive nature of the PGE. The resulting biosensor exhibited the lowest detection limit (3 nM) and highest sensitivity (370 nA/μM) of any electrochemical PTE biosensor. The designed biosensor displayed a stable response to paraoxon (retained 90% anodic current over 1000 s), long-term stability (70% over 8 weeks), reusability (90% after 12 repeated scans), and high selectivity to paraoxon. Finally, the biosensors were tested in real samples (tap water, river water, and a soil slurry) to demonstrate its effectiveness during sensing in biological matrices. It is also important to note this biosensor uses an enzyme (PTE, expressed by our subawardee the US Naval Research Laboratoryspecificaly for this project) that does not become inhibitied. This is an important point to make since mostenzymatic biosensors used to monitor organophosphatehave primarily focused on using cholinesterase enzymes (i.e., acetylcholinesterase or butyrylcholinesterase) that are inhibited in the presence of organophosphates.While such inhibition-based enzyme biosensors have displayed high sensitivity and ultra-low OP detection limits, they also are prone to false-positive signals as cholinesterase enzymes can be inhibited by heavy metals or detergents that are found in soil and water samples. Comparatively, the enzyme phosphotriesterase [PTE (EC 3.1.8.1)] selectively binds to OPs via a three O-linked binding pocket that is selective to specific ester bonds found in many OPs such as paraoxon. PTE catalyzes paraoxon into equimoles of p-nitrophenol, an electroactive molecule, which can be readily monitored through direct oxidation at an applied potential of +0.95 V versus an Ag/AgCl reference electrode. Finally this work from Goal 3 culminated in a journal publication in the journal ACS Applied Materials and Interfaces (8.097).

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: J. Hondred, L. R. Stromberg, C. L. Mosher, J. C. Claussen*, High resolution graphene films for electrochemical sensing via inkjet maskless lithography, ACS Nano, 11, 10, (2017)
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: S. R. Das, S. Srinivasan, L. R. Stromberg, Q. He, N. Garland, W. E. Straszheim, P. M. Ajayan, G. Balasubramanian, J. C. Claussen, Superhydrophobic inkjet printed flexible graphene circuits via direct-pulsed laser writing, Nanoscale, 9, 48, (2017)  COVER ARTICLE
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: J. A. Hondred, J. C. Breger, N. J. Alves, S. A. Trammell, S. A. Walper, I. L. Medintz, J. C. Claussen, Printed graphene electrochemical biosensors fabricated by inkjet maskless lithography for rapid and sensitive detection of organophosphates, ACS Applied Materials and Interfaces, 10, 13, (2018)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: J.A. Hondred, J.C. Breger, S.R. Das, S.A. Walper, I.L. Medintz, J.C. Claussen, In-field, disposable soil sensor for monitoring pesticide levels via laser annealed graphene electrodes, MRS Fall Meeting & Exhibit, Boston MA, (2017)  First Place Graduate Student Poster Competition
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: J.A. Hondred, L.R. Stromberg, J.C. Breger, I.L. Medintz, J.C. Claussen, In-field, disposable soil sensor for monitoring pesticide levels via laser annealed graphene electrodes, Nano@IAState - First Annual Conference on Nanotechnology, Ames IA, (2017)  First Place Graduate Student Poster Competition
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: J.A. Hondred, J.C. Breger, N.T. Garland, S.A. Walper, I.L. Medintz, J.C. Claussen, Scalable manufacturing of graphene-based biosensors for soil management and food safety, Institute of Food Technologists (IFT) Meeting, Las Vegas NV, (2017)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: S.R. Das, Q. Nian, G.J. Cheng, J.C. Claussen, Boosting the electrical conductivity and 3D nanostructuring of inkjet printed graphene with pulsed laser irradiation, Materials Research Society (MRS) Spring Exhibit & Meeting, Phoenix AZ, (2017)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Invited Conference Presentation - Jonathan Claussen NanoTech Conference & Expo, Washington DC, Scalable manufacturing of graphene-based biosensors functionalized with enzyme Nanoparticle bioconjugates for rapid, in-field pesticide monitoring May (2017)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Invited Conference Presentation - Jonathan Claussen 2017 ASME Congress and Exposition, Tampa FL, Inkjet printed graphene on flexible substrates with laser annealing for electrochemical biosensing and nerve cell regeneration, Topic 11-7 Material Processing of Flexible Electronics, Sensors, and Devices, November (2017)
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Invited Conference Presentation - Jonathan Claussen 2017 MRS Fall Meeting & Exhibit - Materials Research Society, Boston MA, Scalable manufacturing of graphene-based biosensors for in-field fertilizer and pesticide sensing, Symposium: Tools and Sensors for Plant and Soil Characterization, December (2017)


Progress 03/01/16 to 02/28/17

Outputs
Target Audience:During this first year of the project the target audience that we reached included experts in the field, interested industry representatives, and the general public Experts in the field where reached through invited research seminars at Texas A&M and the Army Research Laboratory, as well as through conferences associated with the Conference of Food Engineering (CoFE), Institute of Food Technologist (IFT), the World Congress of Biosensors. It should be noted that the World Congress of Biosensors was in Sweden. These research conferences, especially IFT, also included discussions with industry represeentatives and more such industry representative discussions were conducted during an invited research seminar with the Betty and Gordon Moore Foundation. Finally, the results of this research were dissiminated to the general public through press releases from Iowa State University, USDA-NIFA, and numerous other media outlets includingVegetable Growers News and Farm Progress. Details regarding these research presentations/discussions and news pieces are given below. University Texas A&M University, College Station TX, "Inkjet printed nanomaterials for low-cost and flexible biosensors and thermoelectric generators", October (2016) DoD Research Laboratory Army Research Laboratory, Aberdeen Proving Ground, MD, "Inkjet printed nanomaterials for low-cost, flexible, wearable biosensors & thermoelectric generators", August (2016) Foundation Betty and Gordon Moore Foundation, Palo Alto, CA, "Inexpensive and easy-to-use sensor system for point-of-service applications", July (2016) Conferences Institute of Food Technologist (IFT), Chicago IL, "Printable graphene-based, electrochemical soil sensors current innovations in biosensors for food quality and safety", July (2016) Conference of Food Engineering (CoFE), Columbus OH, "Enabling rapid and disposable in field fertilizer and pesticide sensing with inkjet printed graphene by 3D nanostructuring with pulsed-laser annealing", September (2016) World Congress on Biosensors, Gothenburg Sweden, "Welding and 3D etching ink jet printed graphene flakes via laser-pulse annealing on paper and textiles for highly sensitive electrochemical biosensing with disposable and wearable electrodes", May (2016) News Articles Moreover, the research garnered from this first year of the project was dissimenated to new oulets via Iowa State University and USDA-NIFA. In particular, the following news pieces were widely reported to the general public. Iowa State engineers treat printed graphene with lasers to enable paper electronics, devices . (https://www.news.iastate.edu/news/2016/09/01/paperelectronics). Nanostructured Biosensors Detect Pesticide, Help Preserve Environmenthttps://nifa.usda.gov/blog/nanostructured-biosensors-detect-pesticide-help-preserve-environment. This news pieces went viral and were picked up by numerous media outlets including the Vegetable Growers News and Farm Progress. Nanostructured biosensors detect pesticides in soil,https://vegetablegrowersnews.com/news/nanostructured-biosensors-detect-pesticides-soil/ Pesticide sensors could be saving grace for agriculture,https://www.farmprogress.com/crop-protection/pesticide-sensors-could-be-saving-grace-agriculture Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?One of the major unique training periods of this project period was that the Iowa State University PhD graduate student that is working on this project, was able to intern for the summer at the Naval Research Laboratory. This student acquiring his PhD in the department of mechanical engineering and needed to aquire more training in surface chemistry and biology in order to work with enzymes and functionalize nanomaterials with enzymes to complete the goals of this project. Fortunately our sub-awarded, Igor Medintz, was able to host this student for a summer internship at the US Naval Research Laboratory. The student was able to learn how to work with the enzymephosphotriesterase and covalently bind the enzyme to gold nanoparticles. The student was then able to perform enzyme assays with these enzyme-nanoparticle bioconjugates synthesized with distinctly sized gold nanoparticles (5 nm, 10 nm, and 20 nm). The work this student completed at the Naval Research Laboratory lead to the Analyst publication previously mentioned. The PI, Dr. Claussen, was also able to visit the Army Research Laboratory and discuss this project with a variety of staff scientists and discuss potential solutions to the challenges of created these pesticide biosensors. This day and a half trip allowed Dr. Claussen to receive valuable in sight from experts in the field. This trip culminated in a research presentation that Dr. Claussen gave at the laboratory. The details of the talk are given below. Army Research Laboratory, Aberdeen Proving Ground, MD, "Inkjet printed nanomaterials for low-cost, flexible, wearable biosensors & thermoelectric generators", August (2016) How have the results been disseminated to communities of interest?The main results of this project were diseminated three 3 publications as previously reported as well as through invited talks at a US University, DoD reseach laboratory, foundation, and 3 conferences (2 in the US, and 1 international). All of these venues allowed the PI to interact with greater research communities in biosensors and nanomaterials to dissimenate the results of this work, gain valuable feedback, and open the door for future collaborations. These talks were listed under other products but are listed again below for completeness University Texas A&M University, College Station TX, "Inkjet printed nanomaterials for low-cost and flexible biosensors and thermoelectric generators", October (2016) DoD Research Laboratory Army Research Laboratory, Aberdeen Proving Ground, MD, "Inkjet printed nanomaterials for low-cost, flexible, wearable biosensors & thermoelectric generators", August (2016) Foundation Betty and Gordon Moore Foundation, Palo Alto, CA, "Inexpensive and easy-to-use sensor system for point-of-service applications", July (2016) Conferences Institute of Food Technologist (IFT), Chicago IL, "Printable graphene-based, electrochemical soil sensors current innovations in biosensors for food quality and safety", July (2016) Conference of Food Engineering (CoFE), Columbus OH, "Enabling rapid and disposable in field fertilizer and pesticide sensing with inkjet printed graphene by 3D nanostructuring with pulsed-laser annealing", September (2016) World Congress on Biosensors, Gothenburg Sweden, "Welding and 3D etching ink jet printed graphene flakes via laser-pulse annealing on paper and textiles for highly sensitive electrochemical biosensing with disposable and wearable electrodes", May (2016) News Articles Moreover, the research garnered from this first year of the project was dissimenated to new oulets via Iowa State University and USDA-NIFA. In particular, the following news pieces were widely reported to the general public. Iowa State engineers treat printed graphene with lasers to enable paper electronics, devices . (https://www.news.iastate.edu/news/2016/09/01/paperelectronics). Nanostructured Biosensors Detect Pesticide, Help Preserve Environmenthttps://nifa.usda.gov/blog/nanostructured-biosensors-detect-pesticide-help-preserve-environment. This news pieces went viral and were picked up by numerous media outlets including the Vegetable Growers News and Farm Progress. Nanostructured biosensors detect pesticides in soil,https://vegetablegrowersnews.com/news/nanostructured-biosensors-detect-pesticides-soil/ Pesticide sensors could be saving grace for agriculture,https://www.farmprogress.com/crop-protection/pesticide-sensors-could-be-saving-grace-agriculture What do you plan to do during the next reporting period to accomplish the goals?After this first year of project reporting we have realized that more research focus needs to be on further developing the printed graphene electrodes so that they are suitable for robust pesticide sensing in the field. In particular we wish to work on the following main objectives: 1) improve the line resolution of the printed graphene electrodes, 2) tune the surface wettability of the graphene to superhydrophobic, and 3) develop methods to directly functionalize the graphene electrode surface with the enzyme phosphotriesterase developed from the US Naval Research Laboratory (NRL). These three objectives are important because a higher graphene line resolution (< 50 microns) will allow us to create more complex biosensor patterns in a smaller space to increase the multiplexing capability of the sensor (Objective 3). In other words more biosensorsthat can be printed in a smaller space and distinctly functionalized to montior different pesticideswill be able to simutaneously react with a small soil and water field sample to give the end user to probe for multiple pesticides from a single sample. Secondly. converting the graphene to superhydrophobic in some locations will help prevent the surface from biofouling during actual in field sensing. Finally, successfully immbolizing the enzymephosphotriesterase on the graphene surface will create the first prototype electrochemical pesticide biosensor for this project. The knowledge gained in this process will be used to further refine and multiplex the biosensor system.

Impacts
What was accomplished under these goals? This first year of the project was productive as we were able to complete Objective 1 and make progress on both Objective 2 and 3. Details regarding our major accomplishments in the first year of the project are given below. 1. Developed an effective enzyme for organophosphate sensing. Our subawardee, the US Naval Research Laboratory, was able to make the enzymephosphotriesterase which is selective towards binding to organophosphate enzymes.As noted in the publications were were able to conjugate the pesticide phosphotriesterase to gold nanoparticles and improve the catalytic efficiency of the enzyme towards the sensing of a model organophosphate pesticide (paraoxon). Note thatphosphotriesterase is an enzyme that is not inhibited by pesticides such as the enzymes acetocholineresterase and butyrylcholinesterase that are commoningly used in pesticide based biosensors. Not these latter enzymes also often sucuumb to inhibition by heavy metals in soil as well so phosphotriesterase should work better in sensing pesticdes in soil slurry samples than the cholinesterase enzymes. This accomplishment demonstrated the effectiveness of using the enzymephosphotriesterase towards monitoring organophosphates and we showed that the performance of the enzyme could be increased with immobilization on nanoparticles. Morevover we were able to use structural modeling to compute the relative enzyme densities on three distinctly sized nanoparticles (5 nm, 10 nm, and 20 nm) and correlate these enzyme densitives to the performance of the enzyme-nanoaprticle conjugages. This modeling combined with experimental results, demonstratedthat the maxium enzyme reaction rate (Vmax) can be improved by nearly 17 fold by localizing the enzymes on nanoparticles.The work in this accomplishment helped complete tasks associated with Objective 1 and 2 of the proposal. This task amounted to a journal publication in the journal Analyst (impact factor = 3.864?). 1. Demonstrated an effective strategy for developing low-cost printed graphene electrodes on disposable substrates such as paper. The overall objective of the proposal is to create low-cost in-field electrochemical biosensors for the rapid detection of pesticides in soil or water samples. To accomplish this we are developing a test stripe sensor that can be read by a portable potentiostat much like how a glucose test stripe sensor is read by a glucometer. We are using nanomaterials, in our case graphene in particular, to improve the sensitivity of the sensor to make such readings possible. Moroever, since the graphene is made from bulk exfoliation from graphite and will not require metals (such as precious metals typically used in electrochemical sensors)the sensors will be very low-cost, whille being completly disposalbe (just carbon and enzyme in the test strip sensor). The next major accomplishment of this year was developing two distinct methods to anneal printed graphene electrodes. It is important to note that after graphene or graphene oxide flakes are printed theyneed to be annealed to improve both their electrical conductivity and electrochemical reactivity for subsequent electrochemical sensing. Most annealing techniques require high temperatures which can degrade or completly destroy the sensitive polymers or papers the graphene flakes are printed on. In this first year we developed a technique (provisional patent submitted) to anneal graphene flakes with a rapid pulse laser. The laser improved the electrical conductivity of the graphene by three orders of magnitude (from approximately 25 mega ohms per square to 0.7 kiloohms per square). The technique also nano/microstructured the graphene surface to greatly improve its electrocatalytic surface area. Results demonstrated that after the laser annealing the graphene electrodes were very effective in electrochemical sensing hydrogen peroxide and improved reaction kinetics during ferrocyanide cyclic voltammetry. This work enabled us to create printed graphene electrodes even on paper for electrochemical sensing. This will be a key step in created an in-field electrochemical pesticides sensor. This research was published in the journal article Nanoscale (impact factor = 7.233) and made the front cover of the journal! Moreover, we demonstrated how a high-temperature annealing process could be used to dope the printed graphene surface with nitrogen. Nitrogen doped-graphene creates a highly electrically conductive electrode surface. This high temperature annealing process (up to 900 degrees Celsisus) would need to be performed on graphene printed on a non-thermally sensitive substrate (silicon or quartz) which is not as disposable as a paper-based substrate. However this nitrogen-doped graphene could act as alternative to the graphene that was laser-pulsed treated if the latter graphene was not sufficiently conductive for subsequent electrochemical pesticide sensing. The development of the nitrogen-doped graphene resulted in the publication of a journal article in ACS Applied Materials and Interfaces (impact factor = 8.097).

Publications

  • Type: Journal Articles Status: Published Year Published: 2016 Citation: S. R. Das, J. A. Hondred, A. A. Cargill, S. Ding, G. Chen, and J. C. Claussen, 3D Nanostructured Inkjet Printed Graphene via UV Pulsed-laser Irradiation Enables Paper-Based Electronics and Electrochemical Devices, Nanoscale, 8, 35, (2016)  COVER ARTICLE
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: J. A. Hondred, J. C. Breger, N. T. Garland, E. Oh, K. Susumu, S. A. Walper, I. L. Meditz, J C. Claussen*, Enhanced enzyme activity of phosphotriesterase trimer conjugated on gold nanoparticles for pesticide detection, Analyst, 142, 3261-3271, (2017)
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Q. He, S. R. Das, J. A. Hondred, A. A. Cargill, S. Ding, C. Karunakaran, J. C. Claussen, Enabling Inkjet Printed Graphene for Ion Selective Electrodes with Postprint Thermal Annealing, ACS Applied Materials & Interfaces, 9, 14, (2017)