Kinetic versus Thermodynamic Control over Growth Process of Electrodeposited Bi/BiSb Superlattice Nanowires

The growth mechanism of the electrodeposited single crystalline nanowires is generally considered to follow a three-dimensional to two-dimensional (2D) transition mode, and as for the 2D growth, it is ordinarily considered as a plane growth mode (layer-by-layer growth mechanism). We report in this Letter the growth of Bi/BiSb superlattice nanowires by adopting a charge-controlled pulse electrodeposition technique, and to our best knowledge, different growth modes of the nanowires, the 2D plane growth mode, the tilted plane growth mode, and the curved plane growth mode, were first observed. These growth modes were gathered and analyzed from the perspectives of crystal growth as well as kinetics and thermodynamics. It is shown that the superlattice nanowires are good structures for studying the growth mechanism of electrodeposited nanowires. This work will deeply benefit the understanding of the growth process of the electrodeposited nanowires and provide important experiment data to crystal growth theory

Abnormal Growth of Electrodeposited BiSb Alloy Nanotubes

BiSb alloy nanotube−nanowire array has been fabricated by the pulsed electrodeposition technique. It was found that the growth of the polycrystalline nanotubes is terminated by polycrystalline nanowires abruptly and then follows by single crystalline nanowires. The formation mechanism of the nanotubes and the origin of the transition from a polycrystalline nanotube to a polycrystalline nanowire were analyzed and discussed from the perspective of the crystal growth theory. The deep understanding of the transition is of high importance for the controlled synthesis and application in thermoelectric field of Bi-based nanotubes arrays

Controllable Preferential-Etching Synthesis and Photocatalytic Activity of Porous ZnO Nanotubes

Porous ZnO nanotubes have been synthesized via a facile hydrothermal method based on a preferential etching strategy. The nanotubes have a nearly homogeneous size with about 250 nm diameter, 40 nm wall thickness, and 500 nm length. Nanoholes with diameters ranging from tens to hundreds of nanometers were created on the side wall of the tubular structure. Formation of the porous ZnO nanotubes resulted from preferential etching along the c axis and relatively slow etching along the radial directions due to the polar feature of the ZnO crystal. Superior photocatalytic activity of the porous ZnO nanotubes in the degradation of methyl orange compared to the other samples has been demonstrated, and the origin is mainly ascribed to the scattered nanoholes on the wall of the porous nanotubes. The influence factors and formation mechanism of the porous ZnO nanotubes were analyzed and discussed

The Formation of Mesoporous TiO₂ Spheres via a Facile Chemical Process

The mesoporous TiO2 solid and hollow spheres have been synthesized via a controllable and simple chemical route. Structural characterization indicates that these TiO2 mesoporous spheres after calcined at 500 °C have an obvious mesoporous structure with the diameters of 200−300 nm for solid spheres and 200−500 nm for hollow spheres. The average pore sizes and BET surface areas of the mesoporous TiO2 solid and hollow spheres are 6.8, 7.0 nm and 162, 90 m2/g, respectively. Optical adsorption investigation shows that TiO2 solid and hollow spheres possess a direct band gap structure with the optical band gap of 3.68 and 3.75 eV, respectively. A possible formation mechanism for TiO2 solid and hollow spheres is discussed

Hydrothermal Synthesis of Mo-Doped VO₂/TiO₂ Composite Nanocrystals with Enhanced Thermochromic Performance

This paper reports a one-step TiO2 seed-assistant hydrothermal synthesis of Mo-doped VO2(M)/TiO2 composite nanocrystals. It was found that excess Mo doping can promote formation of the VO2(M) phase, and rutile TiO2 seed is beneficial to morphology control, size reduction, and infrared modulation of Mo-doped VO2(M) nanocrystals. The Mo-doped VO2 nanocrystals epitaxially grow on TiO2 seeds and have a quasi-spherical shape with size down to 20 nm and a nearly 35% infrared modulation near room temperature. The findings of this work demonstrate important progress in the near-room-temperature thermochromic performance of VO2(M) nanomaterials, which will find potential application in constructing VO2(M) nanocrystal-based smart window coatings

In Situ Triggering and Dynamically Tracking the Phase Transition in Vanadium Dioxide

As the most widely studied thermochromic material, monoclinic vanadium dioxide (VO₂ (M)) shows promising applications in the energy-saving field. Solid-state transformation, especially fast annealing, plays an important role in the production of VO₂ nanomaterials. On the other hand, the fast process makes it impossible to real-time monitor the phase transition in VO₂. In this paper, a differential scanning calorimetry technique is proposed to in situ trigger and dynamically track the phase transition of VO₂ nanoparticles, which gives a distinguished method to identify the underlying size-dependent and defect-mediated structure phase transition

VO₂@SiO₂ Nanoparticle-Based Films with Localized Surface Plasmon Resonance for Smart Windows

As an ideal thermochromic material for smart windows, vanadium dioxide (VO2(M)) has been receiving wide research interest in recent years. Enhancing the optical switching ability before and after phase transformation of the VO2(M) (i.e., enhancing the solar regulation efficiency ΔTsol while maintaining a great luminous transmittance Tlum) is the target for its application in smart windows. However, the recrystallized growth in the annealing process ruins the thermochromic performance of VO2(M) nanoparticles (NPs). Here, we report the preparation and thermochromic performance of VO2(M)@SiO2 NPs. It was found that the SiO2 shell can effectively protect VO2(M) NPs from growth in the annealing process, and the VO2(M)@SiO2 NP film exhibits an excellent thermochromic performance with ΔTsol of 18.9% and Tlum of 38% after annealing at 450 °C, because of the outstanding contribution of the enhancement and blue-shifting of the localized surface plasmon resonance. Our results provide an efficient way to synthesize VO2(M) NPs with excellent thermochromic performance for smart windows

Different ZnO Nanostructures Fabricated by a Seed-Layer Assisted Electrochemical Route and Their Photoluminescence and Field Emission Properties

A simple seed-layer assisted electrochemical deposition (ECD) route has been successfully developed for preparation of different ZnO nanostructures, and their optical and field emission properties are also studied. ZnO films, nanowires, and nanosheets could be prepared in a rational way by just controlling the ECD current density. The corresponding growth mechanisms are also discussed on the basis of the characteristics of the ZnO crystal structure and the influences of the seed-layer and ECD current density. Except for ZnO nanosheets, both the room-temperature and low-temperature photoluminescence measurements of the ZnO films and nanowire arrays show strong ultraviolet excitonic emission, which proves their good crystal quality. Detailed analysis of the field emission (FE) properties indicates that the hierarchical ZnO nanowire array shows good FE property due to their high aspect ratio, small radius curvature, and proper density

A Submicrosecond-Response Ultraviolet–Visible–Near-Infrared Broadband Photodetector Based on 2D Tellurosilicate InSiTe₃

2D material (2DM) based photodetectors with broadband photoresponse are of great value for a vast number of applications such as multiwavelength photodetection, imaging, and night vision. However, compared with traditional photodetectors based on bulk material, the relatively slow speed performance of 2DM based photodetectors hinders their practical applications. Herein, a submicrosecond-response photodetector based on ternary telluride InSiTe3 with trigonal symmetry and layered structure was demonstrated in this study. The InSiTe3 based photodetectors exhibit an ultrafast photoresponse (545–576 ns) and broadband detection capabilities from the ultraviolet (UV) to the near-infrared (NIR) optical communication region (365–1310 nm). Besides, the photodetector presents an outstanding reversible and stable photoresponse in which the response performance remains consistent within 200 000 cycles of switch operation. These significant findings suggest that InSiTe3 can be a promising candidate for constructing fast response broadband 2DM based optoelectronic devices