Functionalization of metallic nanostructures with different shapes applied as SERS platforms with SIERS effect to selective pesticide detection

• Grant number: 23/08540-6
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: December 01, 2024
• End date: August 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
• Principal Investigator: Italo Odone Mazali
• Grantee: Deysiane Alves Lima dos Santos
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

This project aims to develop sensors for environmental control based on Surface-enhanced Raman scattering (SERS) for pesticide detection, such as atrazine, fipronil, 2,4-D, and benzo(a)pyrene. The sensors will be fabricated using silicon substrates with V-shaped microchannels (Si-V) by lithography and anisotropic etching. The microchannel design will be fabricated at different distances to investigate their effect with different metallic nanostructures and analytes of interest. Specifically, the Si-V substrates possess an effect called SIERS (shaped-induced enhanced Raman scattering), which was discovered in our group in previous work. Briefly, this effect is based on the intensification of the Raman signal promoted only by the shape of the V-cavity on the Si surface, which occurs in the absence of metallic nanostructures and can be observed both for the characteristic band of Si and for any molecule added inside these cavities. This proposal explores how this effect (SIERS) can enhance the plasmonic functions of different metallic morphologies. For this, gold and silver spheres and nanocubes (AuSph, AgSph, AuNCs, and AgNCs) were selected to verify the influence of the plasmonic effect generated by the nanocube vertices concerning the spherical morphologies for SERS signal intensification added to the SIERS effect. The intention is to obtain spherical nanostructures and cubes with approximate sizes (~50 nm) and to evaluate how the SIERS effect can improve the plasmonic functions of spheres near high hot spots generated by the nanocube vertices. The deposition of metallic nanostructures on Si-V substrates will be optimized by the drop-casting method and spontaneous deposition by the self-assembled monolayer (SAM) method. The detection of pesticides will be evaluated by Raman spectroscopy (SIERS/SERS) individually for each of the metallic nanostructures to verify the preferential interactions of the molecules on the surface of the nanostructures and the mixture of two or more molecules. Strategies for functionalizing the metallic nanostructures with molecules that interact specifically with analytes will be performed to obtain selective sensing for each of these molecules. Finally, characterization techniques by UV-vis, FTIR, DLS, transmission, and scanning electron microscopy will be used, as well as simulation tools for better targeting of the experiments and interpretation of the data.