Photochemical and photophysical properties of methylene blue in the microenvironments provided by functionalized gold nanostructures

• Grant number: 23/10315-0
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date until: December 01, 2023
• End date until: February 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Iseli Lourenço Nantes Cardoso
• Grantee: Victor Hladkyi Toledo
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Associated scholarship(s): 24/03168-4 - Ligand exchange in chiral gold nanorods synthesized with 1,12- binaphthyl-2,22-diamine for subsequent cationic dye attachment, BE.EP.DD

Abstract

Different solvent properties like polarity and hydrogen bonds could affect the behavior of the thiazinic dye methylene blue (MB) in solutions. Our group's research, along with others, has demonstrated that the dye properties change significantly when it aggregates or associates with micelles, nanoparticles, films, or different solvents, impacting its applications. Initially, during the Thematic Project (2017-02317-2), the proposal was to investigate how the crystal facets of gold nanostructures affected the photochemical and photophysical properties of MB. However, as the project progressed, we discovered that the dye has a low affinity for these interfaces, a limitation solved by functionalization with an anionic thio-surfactant, 11-mercaptoundecanoic acid (MUA). During the research internship abroad (BEPE-DD 2022/07342-3), we got insights to redirect the project towards studying MB photochemical and photophysical properties modulated in the microenvironment created by functionalization of gold nanostructures surface. In this case, the crystal facet of gold may have either a direct or indirect effect on the dye properties, depending on its organization on the functionalized surface of gold. The capacity to establish hydrogen bonds or hydrophobic interactions in these microenvironments will contribute to the changes in MB properties. The microenvironments will be provided by gold nanospheres, nanorods, nanotriangles, and thin films functionalized by MUA. The nanostructures will be characterized before and after MB association. A deeper comprehension of the surrounding environment's effect on MB will be favored by complementary studies involving different solvents. (AU)