One-dimensional TiO2 (1D TiO2) nanomaterials with unique structural and functional properties have been extensively used in various fields including photocatalytic degradation of pollutants, photocatalytic CO2 reduction into energy fuels, water splitting, solar cells, supercapacitors and lithium-ion batteries. In the past few decades, 1D TiO2 nanostructured materials with a well-controlled size and morphology have been designed and synthesized. Compared to 0D and 2D nanostructures, more attention has been paid to 1D TiO2 nanostructures due to their high aspect ratio, large specific surface area, and excellent electronic or ionic charge transport properties. In this review, we present the crystal structure of TiO2 and the latest development on the fabrication of 1D TiO2 nanostructured materials. Besides, we will look into some critical engineering strategies that give rise to the excellent properties of 1D TiO2 nanostructures such as improved enlargement of the surface area, light absorption and efficient separation of electrons/holes that benefit their potential applications. Moreover, their corresponding environmental and energy applications are described and discussed. With the fast development of the current economy and technology, more and more effort will be put into endowing TiO2-based materials with advanced functionalities and other promising applications.

A review of one-dimensional TiO2 nanostructured materials for environmental and energy applications

Review on the criteria anticipated for the fabrication of highly efficient ZnO-based visible-light-driven photocatalysts

Among the most challenging problems that human beings appear to face are depleting energy sources and increasing environmental pollutions. Heterogeneous photocatalytic processes are the most reward...

Magnetically separable nanocomposites based on ZnO and their applications in photocatalytic processes: A review

Photoelectrochemical (PEC) water splitting is a promising approach for solar-driven hydrogen production with zero emissions, and it has been intensively studied over the past decades. However, the solar-to-hydrogen (STH) efficiencies of the current PEC systems are still far from the 10% target needed for practical application. The development of efficient photoelectrodes in PEC systems holds the key to achieving high STH efficiencies. In recent years, crystal facet engineering has emerged as an important strategy in designing efficient photoelectrodes for PEC water splitting, which has yet to be comprehensively reviewed and is the main focus of this article. After the Introduction, the second section of this review concisely introduces the mechanisms of crystal facet engineering. The subsequent section provides a snapshot of the unique facet-dependent properties of some semiconductor crystals including surface electronic structures, redox reaction sites, surface built-in electric fields, molecular adsorption, photoreaction activity, photocorrosion resistance, and electrical conductivity. Then, the methods for fabricating photoelectrodes with faceted semiconductor crystals are reviewed, with a focus on the preparation processes. In addition, the notable advantages of the crystal facet engineering of photoelectrodes in terms of light harvesting, charge separation and transfer, and surface reactions are critically discussed. This is followed by a systematic overview of the modification strategies of faceted photoelectrodes to further enhance the PEC performance. The last section summarizes the major challenges and some invigorating perspectives for future research on crystal facet engineered photoelectrodes, which are believed to play a vital role in promoting the development of this important research field.

Crystal facet engineering of photoelectrodes for photoelectrochemical water splitting

Quantum dots (QDs) show great promise for use in nanotechnology, owing to their high quantum efficiency, color tenability, narrow emission, and high luminescence efficiency. As a new generation of light-emitting devices (LEDs), QD-LEDs have attracted a great deal of attention in displays and lighting. To meet the commercial requirements, the brightness of QD-LEDs needs to be further improved. In this work, we propose multilayer heterostructures on a SiO2 substrate, which provides multiple reflective bands with the very high reflective efficiency of nearly up to 100%. Electric field distributes mostly in the superficial layer. The proposed structure provides highly multiband reflection covering the emission peaks of QDs in LEDs; hence, it can eventually enhance QDs' fluorescence and enhance the brightness of QD-LEDs. We investigate four typical emission wavelengths, mainly aiming for red QD-LEDs and infrared QD-LEDs, which correspond to the applications of displays, infrared illumination, optical communication, and so on. The total reflection bands can be adjusted according to practical requirements by tuning the thickness of every layer. One fabrication procedure can be used for different kinds of QDs or the same kind of QD with different sizes without changing their processing properties. The proposed structure has fewer flat layers compared with 1-D photonic crystals, which leads to lower cost and easier fabrications.

Enhancing the Brightness of Quantum Dot Light-Emitting Diodes by Multilayer Heterostructures

A TiO2 nanotubes array film with nanowires directly formed on top (denoted as TiO2 NTWs) was prepared by an anodization method (potentiostatic anodization growth). Bi2S3 QDs were sensitized on the CdS/TiO2 NTWs array by a simple successive ionic layer adsorption and reaction (S-SILAR). A short-circuit photocurrent density of 2.16 mA cm−2 was obtained under an illumination of AM 1.5 G. The data of the photoelectrochemical performance test show that Bi2S3/CdS co-modification can boost the photocurrent density of the bare TiO2 NTWs by up to 308%. The photocatalytic activity was tested by treating rhodamine B (RhB) and methyl orange (MO) solutions, which were degraded completely after 240 min and 210 min, respectively. The present study shows the Bi2S3/CdS/TiO2 NTWs array can be applied in photocatalytic devices, and the greatest advantages are low-cost, easy reuse and recyclability.

Simple synthesis method of Bi2S3/CdS quantum dots cosensitized TiO2 nanotubes array with enhanced photoelectrochemical and photocatalytic activity

Fabrication of MgFe2O4–ZnO heterojunction photocatalysts for application of organic pollutants

Te–Sn co-doped Co4Sb12 bulk polycrystalline materials Co4Sb11.7−xTexSn0.3 have been prepared using a high pressure and high temperature method and then characterized using X-ray diffraction. The aim was to use the disorder of the lattice orientation generated by both high pressure and doping with Te and Sn to reduce the thermal conductivity. The thermoelectric properties were measured at room temperature. As expected, as the synthesis pressure increased, the Seebeck coefficient and electrical resistivity increased, but the thermal conductivity decreased greatly. A minimum thermal conductivity of 2.41 W m−1 K−1 was obtained at room temperature for Co4Sb11Te0.7Sn0.3 synthesized at 3 GPa.

Effect of HPHT processing on the structure, and thermoelectric properties of Co4Sb12 co-doped with Te and Sn

Semiconductor/metal composite nanomaterials have been used as surface-enhanced Raman scattering (SERS) active substrates and have attracted increasing attention due to their widespread applications in both optical and material fields. Here, we report a facile strategy to prepare highly sensitive SERS substrates with excellent reproducibility and stability based on uniform and well-controlled Ag nanoparticle (NP) decorated Cu2O nanoframes. Our strategy is a unique one-pot procedure. Simply, hollow Cu2O/Ag composite nanoframes (Cu2O/Ag CNFs) with tunable silver content have been successfully designed and constructed by reduction of Ag+ with sodium citrate in a 14 day old Cu2O-containing mother solution, and then a second component (Ag) was directly deposited onto primary nanomaterials (Cu2O nanoframes). There is an optimum amount of Ag NPs. When 0.40 mM AgNO3 is used, the prepared Cu2O/Ag CNFs show significantly improved SERS properties with an enhancement factor of ~105. Furthermore, the enhancement mechanism, reproducibility and stability of Cu2O/Ag CNFs are investigated in detail. The excellent properties of the prepared Cu2O/Ag CNFs suggest that this substrate has a potential application in SERS detection.

Pin Lv

Papers

Simple synthesis method of Bi2S3/CdS quantum dots cosensitized TiO2 nanotubes array with enhanced photoelectrochemical and photocatalytic activity

Fabrication of MgFe2O4–ZnO heterojunction photocatalysts for application of organic pollutants

Effect of HPHT processing on the structure, and thermoelectric properties of Co4Sb12 co-doped with Te and Sn

Fabrication of Cu2O/Ag composite nanoframes as surface-enhanced Raman scattering substrates in a successive one-pot procedure

Photoelectrochemical property of CdS and PbS cosensitized on the TiO2 array by novel successive ionic layer adsorption and reaction method