Jiqiang Ning

Carbon‐Coated CdS Petalous Nanostructures with Enhanced Photostability and Photocatalytic Activity

With a bandgap ofaround 2.4 eV, which matches well with the visible spectralrange of solar irradiation, CdS exhibits excellent photocata-lytic activity because of its highly effective absorption of solarenergy. As a visible-light-driven photocatalyst, it has beenextensively investigated and its photocatalytic activity hasbeen found to be influenced by a variety of factors includingpreparation conditions, particle size, morphology, and crys-tallinity.

Semiconducting and electroluminescent nanowires self-assembled from organoplatinum(II) complexes

Organometallic nanowires with luminescent and current‐modulating properties were self‐assembled from cyclometalated/terpyridyl platinum(II) complexes with auxiliary arylisocyanide/arylacetylide ligands and incorporated into a compact organic light‐emitting field‐effect transistor (see picture) by solution‐processable protocols. The nanowires exhibit both electron and hole mobilities of 0.1 cm2 V−1 s−1.

Facile Formation of Mesoporous BiVO4/Ag/AgCl Heterostructured Microspheres with Enhanced Visible-Light Photoactivity

In this study, we demonstrate a facile and novel dual-ion-exchange method together with subsequent visible-light induced reduction for synthesis of mesoporous BiVO4/Ag/AgCl ternary heterostructured microspheres (HSMSs) with uniform size distribution. Using flower-like BiOCl microspheres as the starting material, and introducing NaVO3 and AgNO3 by a facile impregnation method, mesoporous BiVO4/AgCl HSMSs have been obtained through solid-phase dual-ion-exchange reactions at 400 °C for 2 h. Interestingly, it has been found that Ag(+) ions play an indispensable role on the dual-ion-exchange reactions, and then the BiVO4/AgCl HSMSs are converted into BiVO4/Ag/AgCl ternary HSMSs by a facile visible-light illumination for 2 h. The as-prepared mesoporous BiVO4/Ag/AgCl ternary HSMSs manifest high photocatalytic activity in degrading methyl orange (MO) and phenol under visible-light illumination, and a possible Z-scheme photocatalytic mechanism is proposed to understand the enhanced photochemical properties.

Facile preparation of 2D sandwich-like CdS nanoparticles/nitrogen-doped reduced graphene oxide hybrid nanosheets with enhanced photoelectrochemical properties

A facile surface-layer-absorption strategy was successfully integrated via a simple in situ sulfidation reaction route for the deposition of CdS nanoparticles on N-doped reduce graphene oxide (N-rGO) nanosheets to produce 2D sandwich-like CdS/N-rGO hybrid nanosheets (HNs). The successful doping of N in the rGO nanosheets and the sandwich stuffing of CdS nanocrystals in the N-rGO sheets were revealed using a variety of techniques, including XPS, XRD and TEM. Compared to the pure CdS and CdS/rGO samples, the as-prepared sandwich CdS/N-rGO HNs exhibited a significantly enhanced photoelectrochemical current response and improved photocatalytic activity for the reduction of aqueous Cr(VI) and the photodegradation of rhodamine B (RhB) under visible-light irradiation. Owing to nitrogen doping in the carbon network of graphene and the unique combination of the CdS nanocrystals and N-rGO nanosheets, superior electrical conductivity could be obtained with the N-rGO matrix. This led to improved charge separation and transport of the photoinduced carriers from the CdS nanoparticles as well as enhanced photochemical performance, which was confirmed by transient photocurrent and electrochemical impedance spectroscopy (EIS).

Facile one-pot solvothermal preparation of Mo-doped Bi2WO6 biscuit-like microstructures for visible-light-driven photocatalytic water oxidation

The adsorption behavior and the separation efficiency of photogenerated electron–hole pairs are two important elements in estimating the photocatalytic activity of a photocatalyst. In this work, we have developed a facile one-pot solvothermal method for the preparation of Mo-doped Bi2WO6 with uniform three-dimensional (3D) hierarchical porous biscuit-like microstructures (PBMs). Mo doping is found to have two important roles in the synthesis of Bi2WO6 particles, leading to porous microstructures and adjusting band gaps of the Bi2MoxW1−xO6 particles. The band structure of the as-prepared porous Bi2MoxW1−xO6 products is characterized by UV-vis diffuse reflectance spectroscopy and valence-band X-ray photoelectron spectroscopy. Density functional theory (DFT) calculations give further insights into the band structure of the Bi2MoxW1−xO6 products. In all the samples, Bi2Mo0.21W0.79O6 PBMs exhibit a very efficient catalytic performance in oxidizing water under visible light irradiation (λ > 420 nm), with an average O2 evolution rate of up to 147.2 μmol h−1 g−1 and an apparent quantum efficiency (QE) of 3.1% at 420 nm, representing a 2 times more enhancement compared with the non-doped Bi2WO6 sample. This study provides a simple method for designing metal-doped semiconductors with porous structures for different applications.

Photoluminescence and Raman mapping characterization of WS2 monolayers prepared using top-down and bottom-up methods

Two kinds of tungsten disulfide (WS2) monolayers, respectively prepared using top-down and bottom-up approaches, were studied with Raman and photoluminescence (PL) mapping techniques. By mapping the intensities of the two characterized phonon modes of WS2, the monolayer region can be quickly selected. Such selection by mapping the intensities is more conclusive than by comparing the small shift in phonon peak position. Also, PL mapping yields more information regarding the uniformity and quality of the monolayers than does Raman mapping. We also show that the focused laser may cause substantial damage to the crystal lattice of monolayers for long-duration mappings.

418cm−1 Raman scattering from gallium nitride nanowires: Is it a vibration mode of N-rich Ga–N bond configuration?

A Raman-active vibration mode at 418cm−1 is observed in wurtzite gallium nitride (GaN) nanowires synthesized by different growth methods. In particular, Raman scattering measurements of a number of GaN nanowires systematically prepared by nitriding β-Ga2O3 nanowires at different temperatures show an interesting evolution of the mode, revealing that it is most likely the vibration mode of N-rich octahedral Ga–N6 bonds. This idea is further supported by the high-resolution transmission electron microscopic observation.

Rapid formation of AgnX(X = S, Cl, PO4, C2O4) nanotubes via an acid-etching anion exchange reaction

This work presents a rapid nanotube fabrication method for a series of silver compounds AgnX, such as Ag2S, AgCl, Ag3PO4, and Ag2C2O4, from pregrown Ag2CO3 nanorod templates. The anion exchange process involved takes place in non-aqueous solutions just at room temperature and completes within 10 minutes. An acid-etching anion exchange reaction mechanism has been proved underneath the transformation process from Ag2CO3 nanorods to AgnX nanotubes by the observation of an intermediate yolk-shell nanostructure. It has been found that the final structure of the products can be conveniently controlled by simply varying the concentration of HnX acids, and the organic solvents employed play a vital role in the formation of the nanotubes by effectively controlling the diffusion rates of different species of reacting ions. As a demonstration, the as-prepared AgCl and Ag3PO4 nanotubes exhibit enhanced photocatalytic activity and favorable recyclability for the photodegradation of rhodamine B (RhB) under visible-light irradiation.

Localized surface optical phonon mode in the InGaN/GaN multiple-quantum- wells nanopillars: Raman spectrum and imaging

An interesting phonon mode at around 685–705 cm−1 was clearly observed in the Raman spectra of InGaN/GaN multiple-quantum-wells nanopillars with different diameters at room temperature. The Raman peak position of this mode is found to show a distinct dependence on the nanopillar size, which is in well agreement with theoretical calculation of the surface optical (SO) phonon modes of nanopillars. Moreover, this kind of SO phonon was evidenced to be located on the pillar surface by using scanning confocal micro-Raman microscopy.

Unusual formation of tetragonal microstructures from nitrogen-doped carbon nanocapsules with cobalt nanocores as a bi-functional oxygen electrocatalyst

A facile non-template solid-state reaction method has been developed for the first time preparation of a tetragonal microstructure self-assembled from nitrogen-doped carbon nanocapsules containing metallic cobalt nanoparticles (Co–N–C) by using graphitic carbon nitride (g-C3N4) and Co(CH3COO)2·4H2O as the only reactants, in which g-C3N4 acts as the effective source of nitrogen and carbon elements in the N-doped carbon nanocapsules and Co(CH3COO)2·4H2O controls the microscopic structure of the self-assembled product. The as-prepared Co–N–C tetragonal microstructures exhibit enhanced electrocatalytic activities for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The synergistic effect of the chemical compositions and the robust microstructure made of the interconnected N-doped carbon nanocapsules accounts for the superior ORR and OER activity and stability to the commercial Pt/C electrocatalyst. The synthetic strategy presented in this work demonstrates a new avenue for developing highly active carbon-based electrocatalysts for electrochemical energy storage and conversion.