Colloidal aggregation mechanisms induced by distinct sample preparation methods and their relation with SERS sensitivity and reproducibility

• Grant number: 22/09619-2
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: October 20, 2022
• End date: April 19, 2023
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Carlos José Leopoldo Constantino
• Grantee: Marcelo José dos Santos Oliveira
• Supervisor: Santiago Sánchez-Cortés
• Host Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil
• Institution abroad: Centro de Física Miguel Antonio Catalán (CFMAC), Spain
• Associated to the scholarship: 21/05460-6 - Detection of emerging contaminants in solutions via surface amplified Raman scattering (SERS), BP.MS

Abstract

The project in progress in the country has the main focus on the application of the surface-enhanced Raman scattering (SERS) technique in the detection of pesticides using Ag colloid, being evaluated the effect of sample preparation (multiple addition method of pattern and external pattern) on the SERS signal and detection limits. In this context, the level of aggregation of nanoparticles in colloids is one factor that influences the reproducibility and sensitivity of the SERS signal. The formation of nanoparticle aggregates from the addition of analytes to colloid can be classified by two mechanisms: diffusion-limited colloid aggregation (DLCA) and reaction-limited colloid aggregation (RLCA). These mechanisms can be influenced by the chemical composition of the analyses and the interaction of the analyte/nanoparticle surface. Thus, this project aims to investigate the different levels of aggregation (mechanism and morphology) of nanoparticles induced by analysis (pesticide). In addition to the need to understand the aggregation mechanisms for the improvement of the SERS signal of these pesticides, the motivation of this study is because we found a divergence in the literature in published studies on such aggregates. The determination of the aggregation mechanism that each pesticide induces in the colloidal system will occur through a systematic study via transmission electron microscopy (TEM) combined with the absorption technique in UV-Vis (extinction) and the SERS spreading itself. The project will be carried out in Spain supervised by researcher Dr. Santiago Sanchez Cortés, who has extensive experience in the synthesis of colloidal systems (metal nanoparticles), using the SERS technique in applications with various analytes. Our research group has had a fruitful collaboration with the researcher Santiago for more than 10 years. Within this period the candidate held a 3-month internship at the Council of Scientific Investigations (CSIC) in the undergraduate period with Dr. Santiago, which will surely help him in the development of his internship. (AU)