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Photocatalyst-assisted degradation of organic pollutants, which exhibits a novel strategy for solar-energy utilization, possesses enormous potential in various applications. Extending the light-absorption range in the spectrum of sunlight and improving light-conversion efficiency are always primary issues to enhance the catalytic performance of these photocatalysts. Herein, a new structure of gold-nanorod-decorated TiO2 rambutan-like microspheres is designed, which exhibits superior photocatalytic ability toward Rhodamine B in the range of visible light due to the 3D distribution of the TiO2 branches on the surface of the microspheres, which prompts the multireflection of photons. The absorption rate of photons is thereby tremendously enhanced. This is beneficial for the generation of hot electrons originating from the localized surface plasmonic resonance of Au nanorods, which can be used to both initiate the reaction and produce the photothermal effect. Hot electrons generated by a single Au nanorod in microspheres to initiate the degradation reaction can be as high as 2.5 times of those in the nanowires' counterpart. Moreover, the heating power of a single Au nanorod in microspheres reaches up to 4.4 times higher than that in nanowires, which further accelerates the degradation rate. The reaction pathway of visible-light-assisted RhB degradation catalyzed by Au/TiO2 microspheres goes through an initial N-deethylation process instead of the complete cycloreversion catalyzed by pure TiO2 microspheres under UV irradiation. This strategy of structure design for improved photon absorption, which achieves high degradation rate and photothermal effect, is promising for the development of novel photocatalysts. [ABSTRACT FROM AUTHOR]

This paper reports a facile fabrication of N-doped graphene quantum dots (N-GQDs) showing controllable chemical properties through a hydrothermal treatment. The N-GQDs have a uniform size of 3.06 ± 0.78 nm and prefer the equilibrium shapes of circle and ellipse due to the minimization of edge free energy. The N/ C atomic ratio in N-GQDs can be precisely tailored in a range from 8.3 at% to 15.8 at% by simply controlling the concentration of N source (ammonium hydroxide). One order of magnitude quantum yield of 34.5% is achieved by N-GQDs, compared with the N-free GQDs, as the substitutional N has an essential role in more effective radiative emission. Excessive N dopants in N-GQDs can lead to photoluminescence quenching, through nonradiative transition back to the ground state. The N-GQDs are further found to be suitable as photocurrent conversion materials due to benign energy matching with anatase nanofibers, the ultrafast electron injection at their interface, and efficient electron transfer. This work provides an efficient and inspiring approach to engineering both chemical components and physical properties of N-GQDs, and will therefore promote their basic research and applications in energy conversion. [ABSTRACT FROM AUTHOR]