Ruilong Zong

Performance Enhancement of ZnO Photocatalyst via Synergic Effect of Surface Oxygen Defect and Graphene Hybridization

ZnO1-x/graphene hybrid photocatalyst was prepared via a facile in-situ reduction of graphene oxide and ZnO1-x surface defect oxide. The hybrid photocatlayst showed enhanced photocatalytic activity for the photodegradation of methylene blue. The photocorrosion of ZnO1-x was successfully inhibited by graphene hybridation. ZnO1-x/graphene hybrid photocatalyst with 1.2 wt % graphene showed the optimized photocatalytic activity. The photocatalytic activity of ZnO1-x/graphene-1.2 wt % under visible and UV light was about 4.6 and 1.2 times that of ZnO1-x sample, respectively. The photocurrent intensity of ZnO1-x under visible and UV light irradiation can be enhanced by 2 and 3.5 times by graphene hybridization. The enhancement of photocatalytic activity and photocurrent intensity in ZnO1-x/graphene was attributed to the synergistic effect between graphene and ZnO1-x for high separation efficiency of photoinduced electron-hole pairs mainly resulting from the promotion of HOMO orbit of graphene and the Oi″ defect level of ZnO1-x in ZnO1-x/graphene.

Defect-related photoluminescence and photocatalytic properties of porous ZnO nanosheets

A porous ZnO nanosheet with a near-rectangular morphology has been successfully prepared through a simple solvothermal-annealing method using Zn5(OH)6(CO3)2 as a pore-directing agent. Moreover, the features of ZnO can be easily tuned by changing the annealing temperature. The evolution of defects along with the increase of annealing temperature has been revealed as follows: the content of surface oxygen vacancy of the as-prepared samples first increases and then decreases, however, the content of impurities decreases gradually. A clear relationship between the defects and photoluminescence/photocatalytic characteristics of ZnO is observed. The defect-related emission mechanism of the visible photoluminescence (PL) for the as-prepared ZnO samples has been proposed. In addition, the samples also show good activities for photo-degradation of phenol under UV light irradiation. ZnO-500 °C (annealed at 500 °C) exhibits the best photocatalytic activity, which is superior to that of commercial ZnO. The photocatalytic activity can be greatly influenced by the relative concentration ratio of surface defects to bulk defects, crystallization performance and specific surface area.

Polyaniline/Carbon Nitride Nanosheets Composite Hydrogel: A Separation-Free and High-Efficient Photocatalyst with 3D Hierarchical Structure.

A polyaniline (PANI)/carbon nitride nanosheets (CNNS) composite hydrogel with 3D hierarchical nanostructure is synthesized via in situ polymerization. The 3D hierarchical structure is robust and stable, making the composite hydrogel separation-free and easy to recycling. It is highly excellent in removing organic pollutant for PANI/CNNS composite hydrogel on account of the cooperation of adsorptive preconcentration and the following photocatalytic oxidation. Pollutants are first adsorbed and concentrated into the 3D hierarchical nanostructure of the composite hydrogel. Then the pollutants are in situ oxidized via photocatalysis. The promoted photocatalytic performance can be mainly ascribed to the outstanding interfacial charge separation and photoelectrochemical performance. A new idea of the construction of 3D hierarchical photocatalysts is presented, which can be applied in the sustainability field.

Photocatalytic hydrogen generation on bifunctional ternary heterostructured In2S3/MoS2/CdS composites with high activity and stability under visible light irradiation

A bifunctional ternary heterostructured In2S3/MoS2/CdS composite photocatalyst with high activity and stability under visible light irradiation was fabricated via a simple hydrothermal method. The bifunctional ternary heterostructured photocatalyst displayed higher activity for photocatalytic hydrogen evolution than GO/CdS and rGO/CdS composites and can be compared with the hydrogen-gennerating efficiency of systems containing the well-known Pt co-catalyst. But above all, the photocorrosion of CdS was also suppressed effectively. The heterojunction structure between MoS2 and CdS promoted the interfacial charge transfer process, suppressed the charge recombination and enhanced the performance of photocatalytic hydrogen generation. Due to the well matching of the VB of CdS with that of In2S3, holes on the VB of CdS could be easily transferred to that of In2S3via the heterojunction structure between In2S3 and CdS, which prevented the accumulation of holes on the VB of CdS, inhibited its photocorrosion and dramatically enhanced its stability. The structure sequence and deposition site play an important role in photocatalytic activity: MoS2 deposited on the interface of CdS and In2S3 was more efficient in promoting charge transfer and thus significantly improved the photocatalytic activity of the composite photocatalyst. Our findings pave a way to design bifunctional CdS-based ternary heterostructured composites for highly efficient H2 generation and photocorrosion suppression.

Self‐Assembled PDINH Supramolecular System for Photocatalysis under Visible Light

A self-assembled perylene-3,4,9,10-tetracarboxylic diimide(PDINH) supramolecular system consisting of all-organic PDINH molecule building blocks through non-covalent interactions works as a visible light photocatalyst with high activity.

Optical properties of transparent copper nanorod and nanowire arrays embedded in anodic alumina oxide

Transparent copper nanorod/nanowire arrays and anodic alumina oxide composite films have been prepared by alternating current electrodeposition, and their linear optical properties have been systematically characterized by absorption spectra. In the experimental spectra, there exist transverse and longitudinal resonance peaks, which are caused by the surface-plasmon resonance along the diameter and the length of the copper nanorods, respectively. The transverse resonance peak is affected by the diameter and aspect ratio of the nanorod. The longitudinal resonance peak appears at longer wavelength when a polarized light illuminates the film with an angle of incidence of about 70 degrees , where the angle is defined with respect to the surface normal. Moreover, the longitudinal resonance mode is sensitive to the polarization direction when compared with the transverse resonance mode.

Controlled synthesis and optimum luminescence of Sm3+-activated nano/submicroscale ceria particles by a facile approach

Rare-earth Sm3+-activated nano/submicroscale ceria particles were prepared by a rapid combustion reaction. Characterized with X-ray diffraction patterns and Raman spectra, the formation of solid solution was confirmed after Sm3+ doping into ceria, and the concentration of oxygen vacancies in the host was gradually increased with the increase of Sm3+ doping content. Assisted by polyvinyl alcohol (PVA) in the combustion reaction process, the morphology of the particles was well distributed and the particle size was controlled from nano (10 nm) to submicro (∼250 nm), depending on the post-sintering temperature. More interesting was that the samples could be effectively excited with 370 nm and emitted strong orange-red light after optimization, which was suitable for the demands of high-efficiency UV LEDs. Without the addition of PVA, the samples showed very weak luminescence even after lengthy sintering. However, the samples prepared by PVA-assisted combustion synthesis exhibited remarkably enhanced emission after an appropriate heat treatment. The quenching concentration of activator Sm3+ was 1.5 mol%, and the optimal luminescence intensity reached nearly 10-fold in comparison with that of samples prepared by conventional solid state reaction. The Sm3+-activated nano/submicroscale ceria materials have potential for use in solid state lighting.

Fabrication of Wide-Range-Visible Photocatalyst Bi2WO6-x nanoplates via Surface Oxygen Vacancies.

Bi2WO6 as a high visible-light-driven catalyst has been aroused broad interest. However, it can only be excitated by the light with λ < 450 nm and the solar energy utilization need to be improved. Here, the wide–range–visible photoresponse Bi2WO6−x nanoplates were fabricated by introducing surface oxygen vacancies through the controllable hydrogen reduction method. The visible photoresponse wavelength range is extended from 450 nm to more than 600 nm. In addition, the photocatalytic activity of Bi2WO6−x is also increased and is 2.1 times as high as that of pristine Bi2WO6. The extending of the photoresponse range and the enhancement of the photoactivity both can be attributed to the surface-oxygen-vacancy states. This is because surface-oxygen–vacancy states generated above and partly overlapping of with the valence band (VB) will result in the rising of valence band maximum (VBM), thus broadening the VB width. This approach is proposed to develop many types of wide–range–visible optical materials and to be applicable to many narrow and wide bandgap materials.

Photonic band gap in (Pb, La)(Zr, Ti)O3 inverse opals

(Pb,La)(Zr,Ti)O3 (PLZT) inverse opal photonic crystals were synthesized by a process of self-assembly in combination with a sol-gel technique. In this process, PLZT precursors were infiltrated into the interstices of the opal template assembled by monodisperse submicron polystyrene spheres, and then gelled in a humid environment. Polystyrene template was removed by calcining the specimen at a final temperature of 700 °C accompanied with the crystallization of perovskite phase in PLZT inverse opal network. Scanning electron microscope images show that the inverse opals possess a fcc structure with a lattice constant of 250 nm. A wide photonic band gap in the visible range is observed from transmission spectra of the sample. Such PLZT inverse opals as photonic crystals should be of importance in device applications.

Kinetically controlled seed-mediated growth of narrow dispersed silver nanoparticles up to 120 nm: secondary nucleation, size focusing, and Ostwald ripening

A facile synthesis method was developed based on the seed-mediated growth to get the narrow dispersed silver nanoparticles with controllable sizes ranging from 20 nm to larger than 120 nm. Environmentally friendly glucose acts as a reducing agent. Because of its weak reducing ability, the secondary nucleation is prevented in the seed-mediated growth, and the size of silver nanoparticles can be tuned continuously by the continuous addition of reactants. Controlling the supersaturation level is critical to suppress both the nucleation and Ostwald ripening, which can be realized by carefully controlling the addition rate of the reactants. We also set up a convenient method to determine the size and size-distribution of silver nanoparticles from the size-dependent absorption spectra of the colloids, and optimize the growth parameters using this method to get narrow dispersed silver nanoparticles.