This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Using pesticides in fruits and vegetables can have a great negative impact in human health and has resulted in several types of cancers, reproductive problems, fetal deaths, birth defects, and kidney and liver damage. As a result, it is very important to develop a rapid and sensitive method to detect trace levels of toxic pesticides. While liquid chromatography-mass spectrometry (LC-MS) has been widely used for the detection of pesticides, some disadvantages include the use of large volumes of expensive solvents, relatively long analysis times, and not being portable or field-deployable. Surface enhanced raman spectroscopy (SERS) is an attractive alternative method that is very sensitive, portable, and field-deployable. In addition, by developing a solution-based SERS method, we can decrease the sample preparation time. We will harness optimal contributions from the electromagnetic effect and the lightning rod effect by using suitable gold nanoparticle shapes with colloidal surface plasmon band that is closest in resonance with the laser excitation wavelength. We will select target pesticides that can either covalently bind to the nanoparticle surface via a suitable functional group or electrostatically bind to the nanoparticle surface if it is charged. Based on the detection limits obtained from the calibration curve generated by SERS spectra obtained at different concentrations of the target pesticide, we will explore potential methods to increase the sensitivity and further lower the detection limit. We will test several methods for improving detection limits such as synthesizing controlled colloidal hot spots, increasing the gold nanoparticle concentration, and synthesizing stable silver nanoparticles that resist oxidation.
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