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Synthesizing novel photocatalysts that can effectively harvest photon energy over a wide range of the solar spectrum for practical applications is vital. Porphyrin-derived nanostructures with properties similar to those of chlorophyll have emerged as promising candidates to meet this requirement. In this study, tetrakis(4-carboxyphenyl) porphyrin (TCPP) nanofibers were formed on the surface of ZnO nanoparticles using a simple self-assembly approach. The obtained ZnO/TCPP nanofiber composites were characterized via scanning electron microscopy, X-ray diffraction analysis, and ultraviolet–visible absorbance and reflectance measurements. The results demonstrated that the ZnO nanoparticles with an average size of approximately 37 nm were well integrated in the TCPP nanofiber matrix. The resultant composite showed photocatalytic activity of ZnO and TCPP nanofibers concomitantly, with band gap energies of 3.12 and 2.43 eV, respectively. The ZnO/TCPP photocatalyst exhibited remarkable photocatalytic performance for RhB degradation with a removal percentage of 97% after 180 min of irradiation under simulated sunlight because of the synergetic activity of ZnO and TCPP nanofibers. The dominant active species participating in the photocatalytic reaction were •O2– and OH•, resulting in enhanced charge separation by exciton-coupled charge-transfer processes between the hybrid materials.

In this study, ZnO/reduced graphene oxide (ZnO/rGO) nanocomposites with various GO concentrations were hydrothermally fabricated. We showed that ZnO and rGO phases coexist in these ZnO/rGO nanocomposites and that the ZnO morphology varies from nanoplates to nanoparticles, with the average ZnO nanocrystal decreasing in size from 38 nm to 20 nm as the GO concentration increased from 0% to 10%. Oxygen-containing functional groups were strongly reduced during the ZnO/GO hybridization process used to form these nanocomposites. The visible 400–800 nm absorption band of the rGO layers increased in intensity with increasing GO concentration. Photocatalytic activity of ZnO/rGO nanocomposite samples was studied under visible light for 60 min. The photocatalytic properties of the ZnO/rGO nanocomposites were significantly superior to those of pure ZnO, with photocatalytic efficiency increasing with increasing GO concentration. Photocatalytic efficiency of ZnO/rGO nanocomposites increased by 30%, 32%, and 60% for samples with 4%, 6%, and 10% GO concentration respectively, after 60 min. These results highlight the potential of the ZnO/rGO nanocomposites for use in pollution-remediation applications.

Herein we studied the structure deformation and photoluminescence properties of titanium dioxide nanotube (TNT) hydrothermally grown on pristine graphene (Gr) surfaces. This Gr/TNT composite shows photocatalytic enhancement in terms of methylene blue degradation efficiency and short saturation time, as a result of heterogeneous junction formation through the interfacial connection of graphene by a facile one-step hydrothermal method. The Gr content within the composites was varied between 0.5 wt.%–8 wt.%, and the sample containing 5 wt% Gr (0.01 g) displayed the highest photocatalytic activity with methylene blue (20 ppm) degradation efficiency of 99.63%. In addition, all the composites exhibited a very short saturation time of ~5 min under sunlight irradiation. The morphological, crystal structural, optical and photocatalytic properties of the composite material were investigated using transmission electron microscopy, scanning electron microscopy, x-ray diffraction, Raman scattering spectroscopy and photoluminescence spectroscopy. The TNTs grown in situ with graphene showed that it enhanced their photocatalytic activity via the reduced carrier recombination rate of TNTs, which was studied by photoluminescence emission measurement. Furthermore, the mechanism by which the combined material properties affect the photocatalytic performance were characterized and clarified.