A Field-Deployable Direct Readout Solution-Based SERS Method for the Rapid and Sensitive Detection of Pesticides in Fruits and Vegetables (2008 – Present)

Investigator:  Radha Narayanan, University of Rhode Island
Mentor:  Chris Brown, University of Rhode Island 

Abstract:  The use of 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, as well as 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 LC-MS has been widely used for the detection of pesticides, some disadvantages of this method include the use of large volumes of expensive solvents, relatively long analysis times, and not being portable or field-deployable. 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 also conduct analysis more rapidly by decreasing the sample preparation time. Our methodology would harness optimal contributions from the electromagnetic effect as well as the lightning rod effect by the use of 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 functional group that is present 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. Some potential ways to increase the sensitivity of our SERS labels include the generation of colloidal hot spots by synthesizing colloidal aggregates or dimers and trimers of different shapes, increasing the gold nanoparticle concentration, and by synthesizing stable silver nanoparticles that resist oxidation and using these nanoparticles as SERS labels. Overall, the field-deployable direct readout solution-based SERS methodology for the rapid and sensitive detection of pesticides in fruits and vegetables is very promising for remediation efforts to reduce their negative impact on human health.