Surface-enhanced Raman Scattering (SERS): pesticide detection and adsorption mechanism

• Grant number: 21/02746-6
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): May 01, 2021
• Effective date (End): April 30, 2022
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal researcher: Carlos José Leopoldo Constantino
• Grantee: Isabela Bianchi Carvalho
• Home Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil
• Associated research grant: 18/22214-6 - Toward a convergence of technologies: from sensing and biosensing to information visualization and machine learning for data analysis in clinical diagnosis, AP.TEM

Abstract

The population growth demands large-scale food production and, in this context, the use of pesticides is a necessary condition and a fundamental element for productivity gains in the agribusiness chain. However, it is also known that, despite the technical standards that regulate the sector, the management of pesticides, since its preparation, application and disposal, does not always follow the standardization, leading risks to the environment and human health. Therefore, strict supervision is necessary and, for this, simple, sensitive and selective methods must be developed and/or improved. In this context, surface-enhanced Raman scattering (SERS) has proven to be a viable technique in the detection of various analytes, including pesticides, due to their more fundamental characteristics, and which are prerequisites in the case of sensing application: sensitivity, given by the enhancement factor of the Raman signal, and selectivity, given by the vibrational nature of Raman scattering. In this IC project, it is proposed the detection via SERS of ethefon, acid-2-chloroethylphosphonic, a growth regulator used to strengthen cereals, promote maturation of fruits and vegetables, stimulate flowering, among other functions, but whose toxicity and environmental dangerousness determined by ANVISA require its monitoring. Ethefon will be dissolved in water and diluted in colloidal dispersions of Ag nanoparticles (AgNPs) at acidic, neutral and basic pHs. Such systems will be characterized by UV-Vis extinction spectroscopy, zeta potential, dynamic light scattering (DLS) and SERS in order to determine the mechanism of ethefon adsorption in AgNPs for the different pHs. Once the pH that confers the best SERS signal in terms of signal/noise resolution is determined, an analytical curve for the ethefon via SERS will be obtained: linear ratio for the "SERS signal intensity" as a function of the "ethefon concentration". It is worth mentioning that the analytical application of the SERS technique is a challenge for the area of knowledge even today.