Detection of microplastics in the presence of synthetic dyes using cellulose-based SERS substrates and silver nanoparticles.

• Grant number: 23/18367-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: May 01, 2024
• End date: August 31, 2027
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Carlos José Leopoldo Constantino
• Grantee: Marcelo José dos Santos Oliveira
• Host 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 - Towards a convergence of technologies: from sensing and biosensing to information visualization and machine learning for data analysis in clinical diagnosis, AP.TEM

Abstract

Plastics have become indispensable materials in human daily life due to their high versatility, applicability, and low cost. They are used in various products such as medical supplies, packaging, toys, automobiles, etc. Consequently, this usage has led to the presence of residues of these materials in the environment, resulting in the formation of microplastics (MPs). MPs arise from the physical, chemical, and/or biological degradation of macroplastics. Due to their bioaccumulative and biopersistent nature, MPs can pose problems for living organisms. Moreover, they can act as a "Trojan horse," carrying other contaminants that adsorb to their surface, amplifying the negative effects of these pollutants.This doctoral project involves two main aspects: i) detection of MPs in the presence and absence of dyes using Surface-Enhanced Raman Scattering (SERS). Polyethylene (PE - negatively charged zeta potential) and polyamide 6 (PA 6 - positively charged zeta potential) MPs were chosen due to the high level of residues of these polymers in the environment. Considering the zeta potentials of these MPs, methylene blue and phthalocyanine will be used as SERS probes and representatives of cationic and anionic dyes, respectively, commonly used in the textile industry. SERS substrates will be optimized from suspensions of cellulose microfibers (MFC - positively or negatively charged) containing Ag nanoparticles (AgNPs - negatively charged) on their surface. Therefore, by balancing the charges involving MFCs, AgNPs, MPs, and dyes, the aim is to concentrate dispersed MPs in aqueous media, improving the chances of their detection. ii) Determine at the molecular level the interactions of MPs with dyes, AgNPs, and MFCs, aiming to optimize the SERS detection process. Interactions will be investigated using Raman spectroscopy, SERS, infrared and ultraviolet-visible absorption spectroscopies, as well as zeta potential and electron microscopy. This doctoral research is linked to the FAPESP Thematic Project 2018/22214-6 and includes a BEPE internship (12 months) in Vitória, Canada, under the supervision of Prof. Alexandre Brolo.