Hydroxyl-/Carboxyl-Rich Graphitic Carbon Nitride/Graphene Oxide Composites for Efficient Photodegradation of Reactive Red 195 and Antibacterial Applications.

In this work, a protonated graphitic carbon nitride (P-g-C3N4)-coated graphene oxide (GO) composite (GO/P-g-C3N4) was prepared via wet-chemistry exfoliation, followed by a freeze-drying process. The GO/P-g-C3N4 composite was found to have an outstanding photodegradation performance effect on the reactive red 195 (RR195) dye and very strong antibacterial properties. Both the GO structure and the dispersed state of P-g-C3N4 were found to play a significant role in enhancing the photocatalytic activity of GO/P-g-C3N4. The GO/P-g-C3N4 obtained via freeze-drying retained a large number of oxygen-containing groups and showed higher catalytic activity and reusability than the reduced GO (rGO)/g-C3N4 obtained via thermal reduction. Characterization of the samples indicates that GO/P-g-C3N4 has a higher specific surface area and photocurrent density than rGO/g-C3N4; it is likely that these properties lead to the superior photocatalytic activity observed in GO/P-g-C3N4. Adsorption energy calculations indicate that O2 can be readily adsorbed onto the GO surface, which results in stronger oxidizing superoxide anion radicals (•O2-) and holes (h+); these active radicals can rapidly degrade RR195 dyes. Moreover, broad-spectrum antibacterial activity (demonstrated against Staphylococcus aureus and Escherichia coli) was observed in the case of the GO/P-g-C3N4 composite irradiated with visible light. This work offers new insights into the design of cost-effective g-C3N4-based photocatalysts for environmental remediation.

Sub-20-nm anatase TiO2 anchored on hollow carbon spheres for enhanced photocatalytic degradation of reactive red 195.

Herein, hollow carbon sphere (HCS)-supported titanium dioxide (TiO2) nanoparticles (sub-20-nm; HCS@TiO2)-based composites are rationally designed and fabricated via a facile wet-chemistry strategy. The introduction of an HCS, which acts as a conductive substrate, improves the separation efficiency of photogenerated hole/electron pairs (h+/e-) from TiO2 because photogenerated electrons are transferred to conductive carbon skeleton. Due to the three-dimensional spherical structure and excellent hydrophilicity of the carbon skeletons, low-density HCS with outstanding conductivity not only accelerate the separation of photogenerated h+/e- pairs from TiO2 but also improve the adsorption performance of the soluble reactive red 195 molecules (RR195) on the surface of TiO2 nanoparticles. These properties of HCS@TiO2 composites enable efficient photocatalytic degradation of RR195. The obtained results indicated that HCS@TiO2 composites (80 wt% TiO2) achieved the best photocatalytic degradation performance with higher photodegradation rate of 97% than pure TiO2 nanoparticles (86%). This study offers a new pathway for the design and preparation of novel photocatalysts to achieve efficient degradation of degrading organic pollutants.