Abstract
The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO2 is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. When TiO2 nanoparticles are modified with graphene quantum dots (GQDs), some significant improvements can be achieved in terms of (i) broadening the light absorption wavelengths, (ii) design of active reaction sites, and (iii) control of the electron-hole (e−-h+) recombination. Accordingly, TiO2-GQDs nanocomposites exhibit promising multifunctionalities in a wide range of fields including, but not limited to, energy, biomedical aids, electronics, and flexible wearable sensors. This review presents some important aspects of TiO2-GQDs nanocomposites as photocatalysts in energy and biomedical applications. These include: (1) structural formulations and synthesis methods of TiO2-GQDs nanocomposites; (2) discourse about the mechanism behind the overall higher photoactivities of these nanocomposites; (3) various characterization techniques which can be used to judge the photocatalytic performance of these nanocomposites, and (4) the application of these nanocomposites in biomedical and energy conversion devices. Although some objectives have been achieved, new challenges still exist and hinder the widespread application of these nanocomposites. These challenges are briefly discussed in the Future Scope section of this review.
Highlights
Accepted: 22 February 2021Smart and multifunctional materials are rapidly transforming the energy and biomedical fields [1,2,3]
The basic properties of graphene quantum dots (GQDs) are mainly dependent on the shape, size, and edge structures, which play an active role in the positioning of absorption peaks in UV–Vis spectra
Results indicated that the TiO2 -GQDs nanocomposites synthesized by the hydrothermal method showed slightly better photocatalytic activity than those synthesized by the sonochemical method. for sonochemical reaction
Summary
Smart and multifunctional materials are rapidly transforming the energy and biomedical fields [1,2,3]. The inherent optical and electronic properties very limited capability to use solar energy and (2) the rapid recombination of its photoof TiO2 are insufficient to achieve adequate catalytic efficiency for energy harvesting and generated electron-hole pairs during catalytic processes [19,20]. The homogeneous of at least two dissimilar nanomateriTiO2 and graphene-based materials, with diverse properties andproperties complementary functiongraphene-based materials, with diverse and complemenals, such as TiO2 and alities, holds great promise for addressing theforgrowing needs of energy and biomedical tary functionalities, holds great promise addressing the growing needs of energy and biomedical [29,30,31,32].which Such materials, whichby arethe formed by theof mixture of two applications [29,30,31,32]. We focus on some important aspects of TiO2 -GQD nanocomposites, such as their synthesis methods, characterization techniques, and applications
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