A ZnO photocatalyst was hybridized with graphite-like C3N4via a monolayer-dispersed method. After hybridization with C3N4, the photocurrent of ZnO was enhanced by 5 times under UV irradiation and a photocurrent under visible light irradiation was observed. The photocatalytic activity of C3N4/ZnO under UV irradiation was increased by 3.5 times, the visible light photocatalytic activity was generated and the photocorrosion of ZnO was suppressed completely after ZnO was hybridized with C3N4. The enhancement in performance and photocorrosion inhibition under UV irradiation was induced by the high separation efficiency of photoinduced holes from ZnO to the HOMO of C3N4. Under visible light irradiation, the electron excited from the HOMO to the LUMO of C3N4 could directly inject into the CB of ZnO, making C3N4/ZnO present visible light photocatalytic activity. The optimum synergetic effect of C3N4/ZnO was found at a weight ratio of 3%, which corresponded to a monolayer dispersion of C3N4 on the surface of ZnO.

Enhancement of photocurrent and photocatalytic activity of ZnO hybridized with graphite-like C3N4

Review on the improvement of the photocatalytic and antibacterial activities of ZnO

Monomolecular-layer polyaniline (PANI) was dispersed on the surface of zinc oxide (ZnO) and formed the hybrid effect between ZnO and PANI. The hybrid photocatalysts showed dramatic photocatalytic activity for the degradation of the methylene blue (MB) both under ultraviolet and visible light irradiation, and the photocorrosion of ZnO was successfully inhibited. The enhanced photocatalytic activity for PANI-hybridized ZnO originated from the high separation efficiency of photogenerated electrons and holes on the interface of PANI and ZnO, which was produced by the hybrid effect of PANI and ZnO. The photocorrosion inhibition of ZnO could be attributed to the rapidly transferring of photogenerated holes by the PANI monolayer. The relationship between the PANI content of the samples and their photocatalytic performance shows that an optimal PANI weight percent (1.0%) can significantly enhance the photocatalytic efficiency and anticorrosion of ZnO particles. In particular, the mechanisms on the enhancement of ...

Photocorrosion Inhibition and Photoactivity Enhancement for Zinc Oxide via Hybridization with Monolayer Polyaniline

Coupling ZnO with carbon materials using a suitable integration method to form ZnO-carbon composites has been established as a promising strategy to ameliorate the photocatalytic performance of semiconductor ZnO. In this perspective article, we describe the recent advances and current status of enhancing the photocatalytic activity and anti-photocorrosion of semiconductor ZnO by coupling with versatile carbon materials, e.g., C60, carbon nanotube, graphene and other carbon materials. The primary roles of carbon materials in boosting the photoactivity and photostability of ZnO have been outlined and illustrated with some selected typical examples. In particular, the three main kinds of mechanisms with regard to anti-photocorrosion of ZnO by coupling with carbon have been demonstrated. Finally, we give a concise perspective on this important research area and specifically propose further research opportunities in optimizing the photocatalytic performance of ZnO-carbon composites and widening the scope of their potential photocatalytic applications.

Improving the photocatalytic activity and anti-photocorrosion of semiconductor ZnO by coupling with versatile carbon

Branched SnO2/α-Fe2O3 semiconductor nanoheterostructures (SNHs) of high purity were synthesized by a low-cost and environmentally friendly hydrothermal strategy, through crystallographic-oriented epitaxial growth of the SnO2 nanorods onto the α-Fe2O3 nanospindles and nanocubes, respectively. It was demonstrated that the SnO2 nanorods would change their preferential growth direction on the varied α-Fe2O3 precursors with distinct crystallographic surface, driven by decrease in the distortion energy induced by lattice mismatch at the interfaces. All of the prepared SNHs were of high purity, ascribing to the successful preinhibition of the SnO2 homonucleation in the reaction system. Significantly, some of the SnO2/α-Fe2O3 SNHs exhibited excellent visible light or UV photocatalytic abilities, remarkably superior to their α-Fe2O3 precursors, mainly owing to the effective electron−hole separation at the SnO2/α-Fe2O3 interfaces.

Hydrothermal Synthesis, Structural Characteristics, and Enhanced Photocatalysis of SnO2/α-Fe2O3 Semiconductor Nanoheterostructures

A series of Zn1−xMgxO samples with dopant content ranging from x = 0 to 0.10 were prepared by a novel rheological phase reaction route. All Zn1−xMgxO samples were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductive coupled plasma optical emission spectroscopy, infrared and UV−vis absorption spectroscopy, and the Barrett−Emmett−-Teller technique. The effects of Mg2+ doping in ZnO on the electronic structures and photogradation of methylene blue dye solution were investigated experimentally and theoretically. All Zn1−xMgxO samples exhibit high photoactivities comparable to Degussa P-25, which first increased with the Mg doing content up to x = 0.05, and then slightly decreased with further doping of Mg to x = 0.10. Density function theory calculations revealed that the substitutions of Mg for Zn ions in the wurtzite ZnO structure largely affected the conduction band, but left the valence band nearly unchanged. The bottom of the conduction band shifted...

Origin of the Enhanced Photocatalytic Activities of Semiconductors: A Case Study of ZnO Doped with Mg2+

Highly crystalline SnO2 nanocrystals with and without Zn2+ doping were directly prepared by a solvothermal method. By systematic characterizations using x-ray diffraction, transmission electron microscopy, infrared spectra, and UV–vis spectra, it is demonstrated that all samples crystallized in a single phase of rutile structure, and that upon Zn2+ doping particle sizes closer to the exciton Bohr radius (2.7 nm) of SnO2 were achieved, while the particle size of SnO2 nanoparticles was as large as about 12 nm without Zn2+ doping. The smaller particle sizes for Zn2+ doped nanoparticles had led to a lattice expansion, a blue-shift of the surface phonon mode for the anti-symmetric Sn–O stretching vibration, and a significantly narrowed band-gap energy, opposite to what is theoretically predicted by the quantum size effect. The photocatalytic activity of the doped samples is measured by monitoring the degradation of methylene blue dye in an aqueous solution under UV-radiation exposure. It is found that Zn2+ doped SnO2 showed excellent activity toward photodegradation of methylene blue solution under UV light irradiation. These observations were interpreted in terms of the Zn2+ doping at the surface sites of SnO2 nanoparticles and the relevant defects that have increased the surface active sites and moreover improved the ratio of surface charge carrier transfer rate to the electron–hole recombination rate. These results illustrate the potential of rationally modifying the particle size and surface defect characteristics for novel semiconductor oxide photocatalysts.

http://iopscience.iop.org/article/10.1088/0957-4484/20/15/155706/pdf

Surface doping for photocatalytic purposes: relations between particle size, surface modifications, and photoactivity of SnO2:Zn2+ nanocrystals

A novel white-light phosphor GdVO4:Ho3+ was prepared via a simple hydrothermal reaction route. Under ultraviolet excitation, the as-prepared nanocrystals showed a broad band emission and sharp line...

Hydrothermal synthesis of GdVO4 : Ho3+ nanorods with a novel white-light emission

Highly dispersed Ln(3+)-doped GdVO4 nanorods were prepared via a hydrothermal method with the assistance of EDTA and CTAB. By systematic structural and property characterization using X-ray diffraction, transition electron microscope, selected area electron diffraction, infrared spectra, and photoluminescence, it is indicated that the as-prepared GdVO4 nanocrystals showed a rod-like shape with an average diameter of about 7 nm and length of 30-50 nm. Under a single-wavelength excitation at 320 nm, GdVO4 nanocrystals doped with Dy3+, Sm3+, and Eu3+ gave surprising multicolor emissions in the visible region, while no blue component at 430 nm from un-doped GdVO4 nanocrystals was seen. This observation was interpreted in terms of the effective energy transfer process between [V4+]A center and lanthanide ions.

Junjie Liu

Papers

Origin of the Enhanced Photocatalytic Activities of Semiconductors: A Case Study of ZnO Doped with Mg2+

Surface doping for photocatalytic purposes: relations between particle size, surface modifications, and photoactivity of SnO2:Zn2+ nanocrystals

Hydrothermal synthesis of GdVO4 : Ho3+ nanorods with a novel white-light emission

Multicolor light emission of GdVO4:Ln3+ nanorods by a single-wavelength excitation.