Progress 01/01/07 to 12/31/09
Outputs
OUTPUTS: A series of experiments have been completed which demonstrate the effectiveness of the approach originally proposed. The ability to detect a variety of analytes has been demonstrated along with some specificity and a limited amount of sensitivity testing PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The detection platform demonstrates the utility of a highly sensitive method for detection of a wide variety of analytes.
Publications
- Teixeira, L.M., Strickland, A.D., Mark, S.S., Bergkvist, M., Sierra-Sastre, Y. and Batt, C.A. (2009) Entropically driven self-assembly of Lysinibacillus sphaericus S-layer proteins analyzed under various environmental conditions. Macro. Biosci. 10: 147-155
- Sierra-Sastre, Y. Dayeh, S.A., Picraux, S.T. and Batt, C.A. (2010) Epitaxy of Ge Nanowires Grown from Biotemplated Au Nanoparticle Catalysts. ACS Nano 4: 1209-1217
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Progress 01/01/07 to 12/31/07
Outputs
In January 2007 we began our current efforts supported by the USDA NRI program. Due to reduced funding we scaled back the original set of objectives to these three: 1. Develop surface modification chemistries to enable sensitive and selective binding of a model target analyte, e.g., benzimidazole-derived pesticides, to the nanofabricated SERS arrays. 2. Create nanofabricated SERS arrays and perform physico-chemical and optical/spectroscopic characterization of SERS effects upon target analyte binding. 3. Test the nanofabricated SERS arrays in a model system for efficacy in detecting the target analyte (benzimidazole pesticides) under simulated environmental conditions. The revised work focused on proof-of-concept, which we have already in principle. The major effort that was removed was the use of S-layer proteins to generate SERS arrays, which we substituted with other synthetic chemical methods that now include the use of nanosphere patterned and nanoparticle SERS
enhancers. The activities we have engaged in towards reaching our goals include the synthesis of cyclodextrin-derived molecules and gold nanoparticles, spectroscopic/microscopic characterization of these products, and Raman-based detection assays using these products. In addition to providing us with a good launching point for our studies on pesticide detection, our current NRI efforts have led to new interactions between our lab and the Cornell community. The aforementioned products have produced formal and informal collaborations with researchers in the Cornell Center for Materials Research (CCMR). Specifically, the cyclodextrin molecules have been used to study new and potentially exciting surface-enhanced Raman scattering substrates, which has resulted in preliminary data used in a proposal submitted by our collaborators for work unrelated to our current NRI efforts. Furthermore, our use of gold nanorods has generated interests within CCMR regarding tip-enhanced Raman
spectroscopy, and CCMR has recently expanded their capital equipment for a core facility - a process that we impacted in the form of a letter of support. We expect that these new collaborations will result in new funding opportunities for our lab. A particularly important collaboration with Cornell's department of Plant Pathology has also surfaced from our work on pesticide detection technology. Based on our current results from this NRI supported effort, discussions with Professor Wayne Wilcox - who is affiliated with the New York State Agricultural Experiment Station - have not only highlighted the need for our proposed technology, but have also helped focus our activities and refine our goals. Details of this are described in the Outcomes/Impacts section of this report.
Impacts
Progress against the objectives set in the current NRI effort has been significant and stimulating, leading to a new paradigm for detection of pesticides in the environment. Our current results reveal that custom synthesized cyclodextrin molecules coupled to custom prepared gold nanoparticles can be used to detect trace levels of pesticides. To date, we have considerable progress toward two key milestones in the project: (1) development of surface enhanced Raman-active binding chemistry for benzimidazole-based pesticides, and (2) highly active surfaced enhanced Raman scattering (SERS) substrates. Specifically, we synthesized gold nanoparticles that have a plasmon absorption maximum that is in resonance with a near-infrared excitation source, which has led to substantial Raman signal enhancement of the pesticides. Furthermore, we have established a method for fine-tuning this resonance condition for excitation sources between 514 nm and beyond 800 nm. Concurrent with
SERS substrate synthesis, we have also established a non-covalent binding strategy for benzimidazole-based pesticides that takes advantage of chemistry exhibited by cyclodextrin molecules. Using the gold nanorods described above together with surface-enhanced Raman spectroscopy, we obtained a detection limit of 30 micromolar for inclusion complexes of a cyclodextrin derivative and a model benzimidazole pesticide. We expect to submit our results to a peer-reviewed journal by March 2008. In an effort to broaden the applicability of our detection strategy to important agricultural needs, we have somewhat expanded our goals to include the development of a field deployable sensor system. That is, using SERS detection we believe that nanoparticle-pesticide conjugates can be incorporated into a pesticide spray mixture to effectively determine pesticide dispersal efficiency and also its persistence/fate over time. To achieve this goal, we are currently fine-tuning the cyclodextrin-pesticide
binding chemistry to include functional groups that will support higher binding affinities as well as increased Raman signal intensities. It is important to note that we are not abandoning our original objective to create nanofabricated SERS arrays as suitable SERS detection platforms, and progress towards our expanded goals will also apply to SERS arrays and there application in SERS-based detection of pesticides. In fact, we believe that the two approaches could be used in concert to provide advanced sensor technologies for agriculturally important analytes. Resources made available by this NRI effort have greatly expanded on our laboratories knowledge of Raman spectroscopy and nanoscale surface characterization. Important collaborations within Cornell's Center for Material Research (CCMR) and the use of its facilities have resulted from the current USDA NRI efforts. Furthermore, a collaboration has started within Cornell's department of Plant Physiology and the New York State
Agricultural Experiment Station, which will provide expert advice and access to facilities aimed at testing our detection technology in plant models (e.g., grapevines and soy beans) under simulated field conditions.
Publications
- No publications reported this period
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