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Our overall goal is to establish a stand-off detection system for remote sensing of agriculturally important analytes. The nanoparticle sentinel system is based upon a nanoparticle component which generates a signature Raman scattering spectrum when the analyte is bound. Nanotechnology provides the tools for creating materials that exploit unique phenomena at the nanoscale. <P>
In this effort two nanoscale properties will be harnessed; (i) molecular target capture and (ii) quantum enhancement of molecular spectral fingerprints. The information generated by these nanoparticle sentinels will allow farmers to more accurately manage crops and to more effectively apply supplements to their fields. In this effort, a number of different gold nanoparticles will be tested whose size and shape varies to include roughened spherical particles and nanostars. The differences in size and shape will have an effect on the spectrum that we obtain and the sensitivity and specificity.
NON-TECHNICAL SUMMARY: This research project aims to establish a standoff detection system for remote sensing of agriculturally important analytes. The nanoparticle sentinel system is based upon a nanoparticle component which generates a spectroscopic signature when the analyte is bound. Nanotechnology provides the tools for creating materials that exploit unique phenomena at the nanoscale. In this effort two nanoscale properties will be harnessed; (i) molecular target capture and (ii) quantum enhancement of molecular spectral fingerprints. The planned research will require the synthesis of gold/silver nanoparticles and specific chemical reagents designed to bind both the nanoparticles and various pesticides. This chemical binding will provide a unique chemical 'fingerprint' that can be assigned to individual pesticides and will be tracked throughout a crop field and over time. The information generated by these nanoparticle sentinels will allow farmers to more accurately manage crops and to more effectively apply supplements to their fields.
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APPROACH: This effort will deliver a practical solution to real-time analysis of distribution and fate of pesticides using two components. One component of the nanoparticle sentinel system will be a SERS active nanoparticle that is able to complex with the target pesticide. The other component is a standoff detection instrument that can be used in the field for detecting SERS spectra from these nanoparticles. The nanoparticles will be designed and optimized laying a foundation for other pesticides and other agents that are applied in the field. In combination, these components will provide a real-time monitoring of pesticide application and fate. Synthesis of gold nanoparticles with different geometries to serve as SERS substrates. As an example of the type of nanoparticle synthesis that we will carry out, highly anisotropic gold nanostars will be prepared following protocols from recent literature. The optical and chemical physico-chemical properties of the gold nanoparticle SERS components will focus on the signal obtained from SERS microscopy and also on the use of a number of complementary surface analytical techniques including scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and attenuated total internal reflection Fourier-transform infrared spectroscopy. Synthesis of nanoparticle ligands capable of binding pesticides. A small library of B-cyclodextrin derivatives will be synthesized that are capable of binding both the SERS-active nanoparticles and various pesticides. The general design of these pesticide chemosensors will accommodate a single thiol binding site for gold/silver nanoparticles and the intrinsic host/guest complexation chemistry of B-cyclodextrin will be exploited to increase the binding affinity for specific pesticides. This will be accomplished by modifying the primary hydroxyl face of B-cyclodextrin. Binding kinetics and thermodynamics of the chemosenosrs with various pesticides will be evaluated using nuclear magnetic resonance spectroscopy, UV visible spectroscopy and SERS spectroscopy. Building a standoff SERS device for detection. A standoff SERS device will be designed and fabricated using commercially available components. The design of the system is based around the use of a telephoto lens to provide the longer working distance. The planned device uses a standard 980nm fiber coupled diode laser (Thorlabs) that is sent through a beam splitter and the telephoto lens to the target. The scattered light is collected through and coupled back into the fiber where it is extracted in the beamsplitter and filtered to remove the elastically scattered light. The filtered light is then sent through for analysis. Testing of the standoff SERS system using a model field application. Actual field testing will be carried during the growing season using fields at the NYS Experiment Stations. The nanoparticle sentinel system will be tested in a manner that is consistent with normal pesticide usage. The fate of the nanoparticles will be followed within the limits of detection for the standoff instrument by scanning the field and potential areas of collection from rain runoff.