Synthesis and chemical modification of Graphene Quantum Dots (GQDs) through oxidative processes, advanced oxidative processes and plasmon catalyzed oxidations: elucidation of synthesis mechanisms and applications in sensors.

• Grant number: 24/17639-9
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2025
• End date: July 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Paola Corio
• Grantee: Paola Corio
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Daniele Cristina Ferreira

Abstract

Carbon nanomaterials (such as single and multi-walled carbon nanotubes, graphene, fullerene, carbon dots and graphene quantum dots) have important technological applications ranging from transistors, sensors, optoelectronic, biochemical, to catalysis among others. Graphene quantum dots (GQDs) represent the latest form of carbon relevant in all these areas. GQDs are graphene nanoparticles with the size of the order of 100 nm. Such nanomaterials have extremely peculiar optical, electronic, chemical, and biological properties. The photoluminescent properties of GQDs can be considered one of their most notable characteristics and are associated with the presence of defects especially at the edges. Due to their photoluminescent properties, high surface area, water solubility, low cytotoxicity, and excellent biocompatibility, GQDs have potential applications in various fields of science. Among the applications of GQDs, we can mention drug delivery, sensors for different chemical species and biomolecules, environmental applications (detection and adsorption of heavy metals), pollutants degradation, among others. This research project proposes the study of methodologies for the synthesis of graphene quantum dots (GQDs) through chemical oxidation methods, advanced oxidative processes (AOPs) and plasmon-enhanced photocatalysis, using different carbon materials as precursors (graphite, graphene, oxidized graphene, coal, glucose, L-lactic acid, citric acid, among others). Chemical oxidation is one of the main methods for synthesizing GQDs and relies in approaches where carbon precursor materials are oxidized through reaction with O3, Cl2, H2SO4, HNO3, H2O2, or other oxidants. Advanced oxidative processes are based on the generation of hydroxyl radicals, which react quickly and indiscriminately with most organic compounds. Plasmon-catalyzed processes mediated by plasmonic nanoparticles (NPs) will also be addressed. The applications of plasmonic metal NPs nanoparticles are based on the unique optical properties that arise from the photoexcitation of localized surface plasmons resonances (LSPRs), which are collective oscillating modes inherent to the conduction band electrons exhibited by certain nanomaterials, in particular Au, Ag. These unique optical properties can be used to promote efficient chemical transformations of substances to achieve photocatalysis in metallic NPs. The GQDs obtained will be chemically modified with heteroatoms (mainly N and S), through hydrothermal and microwave-based methods to tailor their properties, especially photoluminescent. In this project, we will seek to investigate correlations between synthesis methodologies, the morphology of the GQDs obtained, their electronic properties and potential applications in sensors. Among the main methods for characterizing the obtained materials, we mention Raman spectroscopy, resonance Raman spectroscopy, infrared, fluorescence, hyperspectral microscopy, X-ray diffraction, electron spectroscopy, and transmission electron microscopy (HR-TEM) and scanning electron microscopy (SEM). (AU)