Estudio de los efectos de la adsorción de puntos cuánticos de grafeno en nanopartículas de dióxido de titanio: evaluación de las propiedades de intercambio de carga electrónica en medios electrolíticos: síntesis hidrotermal de puntos cuánticos de grafeno.

Abstract

This work describes the effect of sinthesized graphene quantum dots (GQDs) adsorbed on titanium dioxide nanoparticles (TiO₂-NPs) on the electron-hole recombination and charge carrier density. Several characterization techniques as X-ray diffraction, ultraviolet-visible spectroscopy, and infrared spectroscopy were used to verify that the method of synthesis of TiO₂-NPs/GQDs were successful. The percentage of cristallinity of TiO₂-NPs was 71.1%, and after the modification with GQDs increased to 74%. The size of the cristallites of TiO₂-NPs was 8.22 nm, and it was not modified after the adsorption of GQDs. The energy band gap of TiO₂-NPs/GQDs was 3.213 eV, and after the modification with GQDs this value increased to 3.269 eV. The size of the TiO₂-NPs determined by atomic-force microscopy was 97±24 nm, and 93±4 nm for TiO₂-NPs/GQDs. On the other hand, by using electrochemical techniques, it was established that the diffusion coefficients, reaction kinetic constants, and charge carrier densities were higher for the electrodes deposited with TiO₂-NPs/GQDs. Therefore, the charge recombination is lower in the TiO₂-NPs/GQDs than in the TiO₂-NPs.This result was confirmed by analizing the fluorescence intensity of TiO₂-NPs and TiO₂-NPs/GQDs. In conclusion, the adsorption of GQDs on the TiO₂-NPs causes a reduction of the charge recombination and an increase in charge carrier density. Therefore, the modification of TiO₂-NPs with GQDs could improve the photocatalytic activity of titanium dioxide.