Nanobelt Heterostructures Research Articles

Synthesis of Few‐Layer MoS2 Nanosheet‐Coated TiO2 Nanobelt Heterostructures for Enhanced Photocatalytic Activities

MoS(2) nanosheet-coated TiO(2) nanobelt heterostructures--referred to as TiO(2)@MoS(2)--with a 3D hierarchical configuration are prepared via a hydrothermal reaction. The TiO(2) nanobelts used as a synthetic template inhibit the growth of MoS(2) crystals along the c-axis, resulting in a few-layer MoS(2) nanosheet coating on the TiO(2) nanobelts. The as-prepared TiO(2)@MoS(2) heterostructure shows a high photocatalytic hydrogen production even without the Pt co-catalyst. Importantly, the TiO(2)@MoS(2) heterostructure with 50 wt% of MoS(2) exhibits the highest hydrogen production rate of 1.6 mmol h(-1) g(-1). Moreover, such a heterostructure possesses a strong adsorption ability towards organic dyes and shows high performance in photocatalytic degradation of the dye molecules.

Nanopaper based on Ag/TiO2 nanobelts heterostructure for continuous-flow photocatalytic treatment of liquid and gas phase pollutants

The Ag/TiO2 nanobelt heterostructures were prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The photocatalytic activity of TiO2 nanobelts was evidently enhanced by the heterostructures between Ag nanoparticles and TiO2 nanobelts. The nanopapers based on Ag/TiO2 nanobelt heterostructures were fabricated via a modified paper-making process. A novel continuous photocatalytic reactor was designed, and MO removal rate of Ag/C–TiO2 nanopaper was achieved to 100% in 40min for single layer and only in 6min for three layers. The self-supported TiO2 nanopapers with porous structures also showed an excellent continuous photocatalytic performance for toluene gas under UV light irradiation, and the corresponding degradation rate was 69.5% in 184min. Moreover, the Ag/TiO2 nanobelts nanopaper showed a good antibacterial effect. The multifunctional TiO2 nanopapers modified by the heterostuctures could have potential applications in the environmental and biomaterial fields.

Enhanced gas sensing performance ofSnO2/α-MoO3 heterostructure nanobelts

Extremely high sensitivity and low working temperature of gas sensors are realized fromSnO2/α-MoO3 heterostructure nanobelts. Their sensitivity against 500 ppm ethanol is up to 67.76 at the working temperature of300 °C, which is higherthan that of bare α-MoO3 and SnO2 nanostructures. Also the working temperature can be lowered down to120 °C. Such behaviors are attributed to the variation of the junction barrier at theSnO2/α-MoO3 interface. The present results imply that heterostructured 1D nanomaterials may yield gassensors with improved characteristics, and can be applied to a wide range of gas sensors.

Phase transformation of TiO2 nanobelts and TiO2(B)/anatase interface heterostructure nanobelts with enhanced photocatalytic activity

TiO2 nanobelts are very attractive due to their dimensional confinement and structurally well-defined physical and chemical properties. However, the obscure phase transformation mechanism and the low photocatalytic activity of TiO2 nanobelts limit their wide applications. Here, the phase transformations among H2Ti3O7, TiO2(B), anatase and rutile nanobelts were characterized in detail by X-ray powder diffraction, high resolution transmission electron microscopy, Raman spectroscopy and UV-Vis diffuse reflectance spectra. TiO2(B) is inevitable in the phase transformation of TiO2 nanobelts due to the shape limiting effort and the similar crystal structure between H2Ti3O7 and TiO2(B). TiO2 nanobelts have a good thermal stability for the crystal phase and nanostructures. TiO2(B)/anatase interface heterostructure nanobelts were obtained by calcining H2Ti3O7 nanobelts at 800 °C, which had an enhanced photocatalytic ability comparing with pure TiO2(B) and anatase nanobelts. The mechanisms of the phase transformation of TiO2 nanobelts and the enhanced photocatalytic activity of TiO2(B)/anatase interface heterostructure nanobelts were discussed. The self-transformed heterostructure nanobelts have good photocatalytic activity, stability and easy-recovery properties, which will have important practical applications.

Nanoheterostructures on TiO2 nanobelts achieved by acid hydrothermal method with enhanced photocatalytic and gas sensitive performance

Nanoheterostructures of TiO2 nanoparticles/TiO2 nanobelts and Ag/TiO2 nanoparticles/TiO2 nanobelts are prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The experimental parameters, including acid corrosion time and calcination temperature, are investigated in detail. Compared with TiO2 nanobelts, the single nanoheterostructure TiO2 nanoparticles/TiO2 nanobelts have a better photocatalytic activity. The double nanoheterostructure Ag/TiO2 nanoparticles/TiO2 nanobelts can further dramatically enhance photocatalytic properties of TiO2 nanobelts. The mechanisms for formation of the heterostructure and the enhanced photocatalytic effect of the heterostructure are discussed. The liquid continuous-flow photocatalysis based on TiO2 nanobelt nanopaper with different heterostructures is carried out, which has an efficient photocatalytic ability. At the same time, the obtained TiO2 nanobelt heterostructures have a good gas sensitive performance for ethanol.

Wide bandwidth lasing randomly assembled ZnS/ZnO biaxial nanobelt heterostructures

Wide-bandwidth random lasing action is observed from the randomly assembled ZnS/ZnO biaxial nanobelt heterostructures under optical excitation. This is because optical gain at ultraviolet regime can be obtained from the near-band-edge radiative recombination of ZnS and ZnO. Surface defects related radiative recombination centers of ZnS and ZnO nanostructures also contribute to the visible optical gain. Hence, a broadband optical gain is obtained from the ZnS/ZnO biaxial nanobelt heterostructures. Moreover, a wide bandwidth coherent optical feedback can be achieved from the randomly assembled biaxial nanobelts due to high refractive index contrast between the nanobelts and air.

Synthesis of In2O3 Nanowire-Decorated Ga2O3 Nanobelt Heterostructures and Their Electrical and Field-Emission Properties

We report on the synthesis of In2O3 nanowire-decorated Ga2O3 nanobelt heterostructures via a simple catalyst-free method. A typical heterostructure, where an In2O3 nanowire forms a sort of a "dorsal fin" on the Ga2O3 nanobelt, exhibits the T-shaped cross-section. The structure, electrical porperties, and field-emission properties of this material are systematically investigated. The heterostructures possess a typical n-type semiconducting behavior with enhanced conductivity. Field-emission measurements show that they have a low turn-on field (approximately 1.31 V/microm) and a high field-enhancement factor (over 4000). The excellent field-emission characteristics are attributed to their special geometry and good electrical properties. The present In2O3-decorated Ga2O3 heterostructures are envisaged to be decent field-emitters useful in advanced electronic and optoelectronic nanodevices.

CdS/CdSe lateral heterostructure nanobelts by a two-step physical vapor transportmethod

The two-dimensional heterostructure nanobelts with a central CdSe region andlateral CdS structures are synthesized by a two-step physical vapor transportmethod. The large growth rate difference between lateral CdS structures on both ± (0001) sidesof the CdSe region is found. The growth anisotropy is discussed in terms of the polar nature of theside ± (0001) surfaces of CdSe. High-resolution transmission electron microscopy reveals the CdSe centralregion covered with non-uniform CdS layer/islands. From micro-photoluminescencemeasurements, a systematic blueshift of emission energy from the central CdSe region inaccordance with the increase of lateral CdS growth temperature is observed. This resultindicates that the intermixing rate in the CdSe region with CdS increases with the increaseof lateral CdS growth temperature. In conventional CdSSe ternary nanostructures,morphology and emission wavelength were correlated parameters. However, the morphologyand emission wavelength are independently controllable in the CdS/CdSe lateralheterostructure nanobelts. This structure is attractive for applications in visibleoptoelectronic devices.

Interface dominated high photocatalytic properties of electrostatic self-assembled Ag2O/TiO2 heterostructure

Electrostatic self-assembled Ag(2)O/TiO(2) nanobelts heterostructure was synthesized via simple physical mixing of Ag(2)O nanoparticles and TiO(2) nanobelts. The morphologies and microstructures of Ag(2)O/TiO(2) nanobelt heterostructure were characterized by high resolution transmission electron microscopy. The interface dominated high UV photocatalytic activity and degraded photoluminescence strength of composite catalyst confirmed the heterostructure effect between Ag(2)O nanoparticles and TiO(2) nanobelts. X-ray photoelectron spectroscope provided direct evidence of charge transfer on the heterostructures between them.

Preparation of ZnO/In2O3(ZnO)n heterostructure nanobelts

Bent In2O3(ZnO)n/ZnO (n = 4 and 5) heterostructure nanobelts were successfully synthesized by a simple thermal vapor method for the first time, using Au as a catalyst. The heterostructures were characterized by transmission electron microscopy and nanoprobe X-ray energy dispersive. The relationship between the strain induced by lattice mismatch and the radius of curvature of the nanobelts with heterostructure is discussed in terms of geometric mathematics. A formation mechanism of the heterostructures is suggested. Such a structure could be an ideal model system for exploring novel phenomena with potential applications and studying size and dimension dependent properties at the nanoscale.

Formation and photoluminescence of one-dimensional SiOx dot array–ZnO nanobelt heterostructures

We designed and successfully synthesized novel SiOx/ZnO heterostructures via one-step thermal reaction route. Orbicular SiOx dots regularly and alternately arrange in the middle of the up/down surfaces of a nanobelt to form a one-dimensional SiOx dot array, respectively, by their self-assembly. A high-resolution transmission electron microscopy study and a selected area electron diffraction pattern revealed that ZnO nanobelts are crystalline while SiOx dots are amorphous. The formation process of such heterostructure is discussed in terms of the Stranski–Krastanow growth mode of semiconductor quantum dots. Strong white luminescence was observed by bare eyes when the photoluminescence spectrum was measured.

Zn2SiO4/ZnO Core/Shell Coaxial Heterostructure Nanobelts Formed by an Epitaxial Growth

Si-doped ZnO can be synthesized on the surface of the early grown Zn2SiO4 nanostructures and form core/ shell coaxial heterostructure nanobelts with an epitaxial orientation relationship. A parallel interface with a periodicity array of edge dislocations and an inclined interface without dislocations can be formed. The visible green emission is predominant in PL spectra due to carrier localization by high density of deep traps from complexes of impurities and defects. Due to band tail localization induced by composition and defect fluctuation, and high density of free-carriers donated by doping, especially the further dissociation of excitons into free-carriers at high excitation intensity, the near-band-edge emission is dominated by the transition of free-electrons to free-holes, and furthermore, exhibits a significant excitation power-dependent red-shift characteristic. Due to the structure relaxation and the thermalization effects, carrier delocalization takes place in deep traps with increasing excitation density. As a result, the green emission passes through a maximum at 0.25I(0) excitation intensity, and the ratio of the violet to green emission increases monotonously as the excitation laser power density increases. The violet and green emission of ZnO nanostructures can be well tuned by a moderate doping and a variation in the excitation density.