ZTO Nanowires Research Articles

ZnSn(OH)6 nanocube/ Zn2SnO4 nanowires yolk–shell hierarchical structure with tunable band gap for deep-UV photodetection

Ternary oxides nanomaterials (TONs) are the mostly investigated as a promising candidate for ultraviolet detection due to its excellent photoconductivity. Among them, Zn2SnO4 (ZTO) has received extensive attention, but its advantages cannot be utilized in deep-ultraviolet (DUV) detection due to band gap limitation. Herein, we synthesized ZnSn(OH)6 nanocube/ ZTO nanowires yolk–shell hierarchical structure with tunable band gap between 3.6 and 4.4 eV by the dual laser ablation in liquid plus hydrothermal method. This hierarchical structure is applied to DUV photodetection and the results showed that it could improve the Ilight/ Idark ratio of ZTO DUV photodetection by two orders of magnitude while retaining the advantage of ZTO’s rapid response time (τrise =0.43 ms, τdecay =0.55 ms). Moreover, deep-UV imaging is also realized based on this material. This approach provides a new way of tuning the TONs’ band gap and its application to DUV photodetection or imaging.

Fabrication and Photocatalytic Properties of Zinc Tin Oxide Nanowires Decorated with Silver Nanoparticles.

With the continuous advancement of high-tech industries, how to properly handle pollutants has become urgent. Photocatalysis is a solution that may effectively degrade pollutants into harmless molecules. In this study, we synthesized single crystalline Zn2SnO4 (ZTO) nanowires through chemical vapor deposition and selective etching. The chemical bath redox method was used to modify the ZTO nanowires with Ag nanoparticles to explore the photocatalytic properties of the nanoheterostructures. The combination of the materials here is rare. Optical measurements by photoluminescence (PL) and UV–Vis show that the PL spectrum of ZTO nanowires was mainly in the visible light region and attributed to oxygen vacancies. The luminescence intensity of the nanowires was significantly reduced after modification, demonstrating that the heterojunction could effectively reduce the electron-hole pair recombination. The reduction increased with the increase in Ag decoration. The conversion from the UV–Vis absorption spectrum to the Tauc Plot shows that the band gap of the nanowire was 4.05 eV. With 10 ppm methylene blue (MB) as the degradation solution, ZTO nanowires exhibit excellent photodegradation efficiency. Reusability and stability in photodegradation of the nanowires were demonstrated. Photocatalytic efficiency increases with the number of Ag nanoparticles. The main reaction mechanism was confirmed by photocatalytic inhibitors. This study enriches our understanding of ZTO-based nanostructures and facilitates their applications in water splitting, sewage treatment and air purification.

Piezopotential‐Induced Schottky Behavior of Zn1−xSnO3 Nanowire Arrays and Piezophotocatalytic Applications

This article presents the piezotronic‐ and piezophototronic effect‐enhanced photocatalysis (piezophotocatalysis) of Zn1−xSnO3 (ZTO) nanowires fabricated through a two‐step hydrothermal reaction. The highlights of this research include (1) tailoring hydrothermal synthesis parameters to obtain well‐aligned LN‐type single‐crystalline ZTO nanowire arrays; (2) exploring the piezopotential‐driven piezotronic and piezophototronic effects of ZTO nanowires; (3) identifying Schottky barrier height variations; and (4) exploiting synergistic piezophotocatalysis for decomposing methylene blue (MB). Transmission electron microscopy, electron probe energy‐dispersive spectroscopy, and X‐ray photoelectron spectroscopy analyses reveal highly crystalline Zn‐deficient ZTO nanowires. The band gap is estimated to be approximately 3.8 eV. The ZTO nanowires exhibit piezopotential‐modulated piezotronic and piezophototronic effects. The corresponding Schottky barrier height variation is calculated using thermionic emission‐diffusion theory. The calculated photodegradation rate constant k of the sample, under pressure from ultrasonic vibration and a piece of glass, is approximately 1.5 × 10−2 min−1, approximately four times higher than that of ZTO nanowires in the absence of stress. The observed synergistic piezophotocatalysis is attributed to (1) band bending of ZTO nanowires; (2) application of alternating ultrasonic vibration; (3) MB mass transfer enhancement; and (4) abundant active reaction sites generated from ZTO nanowire surface sweeping.

A novel self-catalytic route to zinc stannate nanowires and cathodoluminescence and electrical transport properties of a single nanowire

Abstract A simple chemical vapor evaporation (CVD) method has been employed to fabricate zinc stannate (Zn 2 SnO 4 ) inverse spinel nanowires without using any catalyst. It is found that the Zn 2 SnO 4 (ZTO) nanowires are single crystals and their average length is up to several tens of micrometers. Based on the results of X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy, and transmission electron microscopy, the mechanism in the formation of the Zn-rich ZTO nanowires has been deduced, and it is found that the growth of the wires follows a self-catalytic vapor–liquid–solid (VLS) mechanism. The cathodoluminescence (CL) spectrum of a single nanowire contains a strong and broad red emission, which is originated from the disordered spinel structure induced by the substitution of excess Zn ion for the sites of the Sn ions. The electrical transport measurement of a single ZTO nanowire reveals that it is an N-type semiconductor behavior. The calculated resistivity without gate voltage is ca . 1.6 Ωcm −1 at 300 K. The gate-dependence plot shows a distinguish gate control for the voltage ranged between −10 and 30 V, and the resistance decreased almost linearly with increasing gate voltage.

Synthesis and characterization of single-crystalline zinc tin oxide nanowires.

Crystalline zinc tin oxide (ZTO; zinc oxide with heavy tin doping of 33 at.%) nanowires were first synthesized using the electrodeposition and heat treatment method based on an anodic aluminum oxide (AAO) membrane, which has an average diameter of about 60 nm. According to the field emission scanning electron microscopy (FE-SEM) results, the synthesized ZTO nanowires are highly ordered and have high wire packing densities. The length of ZTO nanowires is about 4 μm, and the aspect ratio is around 67. ZTO nanowires with a Zn/(Zn + Sn) atomic ratio of 0.67 (approximately 2/3) were observed from an energy dispersive spectrometer (EDS). X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrated that the ZTO nanowire is hexagonal single-crystalline. The study of ultraviolet/visible/near-infrared (UV/Vis/NIR) absorption showed that the ZTO nanowire is a wide-band semiconductor with a band gap energy of 3.7 eV.

Interface studies of N2 plasma-treated ZnSnO nanowire transistors using low-frequency noise measurements

Due to the large surface-to-volume ratio of nanowires, the quality of nanowire–insulator interfaces as well as the nanowire surface characteristics significantly influence the electrical characteristics of nanowire transistors (NWTs). To improve the electrical characteristics by doping or post-processing, it is important to evaluate the interface characteristics and stability of NWTs. In this study, we have synthesized ZnSnO (ZTO) nanowires using the chemical vapor deposition method, characterized the composition of ZTO nanowires using x-ray photoelectron spectroscopy, and fabricated ZTO NWTs. We have characterized the current–voltage characteristics and low-frequency noise of ZTO NWTs in order to investigate the effects of interface states on subthreshold slope (SS) and the noise before and after N2 plasma treatments. The as-fabricated device exhibited a SS of 0.29 V/dec and Hooge parameter of ∼1.20 × 10−2. Upon N2 plasma treatment with N2 gas flow rate of 40 sccm (20 sccm), the SS improved to 0.12 V/dec (0.21 V/dec) and the Hooge parameter decreased to ∼4.99 × 10−3 (8.14 × 10−3). The interface trap densities inferred from both SS and low-frequency noise decrease upon plasma treatment, with the highest flow rate yielding the smallest trap density. These results demonstrate that the N2 plasma treatment decreases the interface trap states and defects on ZTO nanowires, thereby enabling the fabrication of high-quality nanowire interfaces.

Morphology and optical properties of ternary Zn–Sn–O semiconductor nanowires with catalyst-free growth

This study reports the synthesis of Zn2SnO4 (ZTO) nanowires with various morphologies using thermal evaporation without a metal catalyst. X-ray diffraction patterns show that the structure of the as-synthesized ZTO nanowires is a face-centered cubic spinel phase. Scanning electron microscopy images exhibit that the as-synthesized nanowires have various morphologies, and homogeneously cover the area of interest. High-resolution transmittance electron microscopy reveals that these ZTO nanowires have single crystalline microstructures with four morphologies. The results of low-temperature cathodoluminescence (CL) measurements show the crystal defects of oxygen vacancies and interstitials may contribute to blue-green and yellow-orange emissions, respectively, for the as-synthesized single nanowire. This study also discusses the effects of thermal annealing under oxygen-rich and reducing ambient on the CL properties of the single ZTO nanowire.

Flexible Zn2SnO4/MnO2 Core/Shell Nanocable−Carbon Microfiber Hybrid Composites for High-Performance Supercapacitor Electrodes

We demonstrate the design and fabrication of a novel flexible nanoarchitecture by facile coating ultrathin (several nanometers thick) films of MnO2 to highly electrical conductive Zn2SnO4 (ZTO) nanowires grown radially on carbon microfibers (CMFs) to achieve high specific capacitance, high-energy density, high-power density, and long-term life for supercapacitor electrode applications. The crystalline ZTO nanowires grown on CMFs were uniquely served as highly conductive cores to support a highly electrolytic accessible surface area of redox active MnO2 shells and also provide reliable electrical connections to the MnO2 shells. The maximum specific capacitances of 621.6 F/g (based on pristine MnO2) by cyclic voltammetry (CV) at a scan rate of 2 mV/s and 642.4 F/g by chronopotentiometry at a current density of 1 A/g were achieved in 1 M Na2SO4 aqueous solution. The hybrid MnO2/ZTO/CMF hybrid composite also exhibited excellent rate capability with specific energy of 36.8 Wh/kg and specific power of 32 kW/kg at current density of 40 A/g, respectively, and good long-term cycling stability (only 1.2% loss of its initial specific capacitance after 1000 cycles). These results suggest that such MnO2/ZTO/CF hybrid composite architecture is very promising for next generation high-performance supercapacitors.

Physical and Electrical Properties of Single Zn[sub 2]SnO[sub 4] Nanowires

Electrical characterizations of single Zn2SnO4 (ZTO) nanowire devices are presented. These include resistivity, mobility, and photosensing measurements. The resistivity and the mobility of the Zn2SnO4 nanowire were measured to be 5.6 cm and 0.2 cm2/Vs, respectively. These values were found to be strongly dependent on the amount of electron-donating defects and less dependent on the thickness of the nanowires. An increase in the resistivity when changing the ambient atmosphere is observed. This change is caused by defect states lying in the bandgap, as shown by photoluminescence. The results imply the potential of ZTO nanowires as phototransistors and other photosensitive devices. © 2010 The Electrochemical Society.

Synthesis, characterization and opto-electrical properties of ternaryZn2SnO4 nanowires

Ternary oxides have the potential to display better electrical and opticalproperties than the commonly fabricated binary oxides. In our experiments,Zn2SnO4 (ZTO) nanowires were synthesized via thermal evaporation and vapor phase transport. Theopto-electrical performance of the nanowires was investigated. An individual ZTO nanowirefield-effect transistor was successfully fabricated for the first time and shows an on–off ratio of104 and transconductance of 20.6 nS, which demonstrates the promising electronic performanceof ZTO nanowire in an electrical device. Field emission experiments on ZTO nanowirefilm also indicate their potential application as a field emission electron source.

High performance ultraviolet photodetectors based on an individual Zn2SnO4 single crystalline nanowire

Zn2SnO4 (ZTO) nanowires were prepared by thermal evaporation method and ultraviolet photodetectors based on an individual ZTO nanowire were investigated. The devices exhibited high performance such as high “ON/OFF” current ratio, high response speed and excellent device stability.

CHARACTERIZATION AND PHOTOCATALYTIC ACTIVITY OF Zn2SnO4 NANOSTRUCTURES SYNTHESIZED VIA HYDROTHERMAL METHOD

Nanosized zinc stannate Zn 2 SnO 4 ( ZTO ) was synthesized via a simple hydrothermal method using sodium hydroxide NaOH as a mineralizer. Hydrothermally treated at 150, 200, and 250°C for 24 h and 48 h, the X-ray diffraction (XRD) pattern showed that highly crystalline ZTO nanostructures could be formed at 200 and 250°C. Transmission electron microscopy (TEM) images showed that ZTO nanocubes were formed at 250°C, and a sheet-like structure was found at 200°C. Raman spectra revealed that ZTO had a spinel structure and there were two Raman shift peaks at approximately 668 and 535 cm-1, which were similar to the peaks of ZTO nanowires. Furthermore, the photocatalytic activity of the ZTO samples was assessed utilizing methylene blue (MB) under ultraviolet irradiation, and the UV-Visible light absorption spectra was investigated to interpret the relationship between photocatalytic properties and light absorptivity. The sheet-like ZTO nanostructures exhibited better photocatalytic activity due to their excellent light absorption properties.

Synthesis and characterization of axially periodic Zn2SnO4 dendritic nanostructures

Zn2SnO4 (ZTO) nanowires with a unique dendritic nanostructure were synthesized via a simple one-step thermal evaporation and condensation process. The morphology and microstructure of the ZTO nanodendrite have been investigated by means of field emission scanning electron microscopy (SEM), x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). SEM observation revealed the formation of branched nanostructures and showed that each branch exhibited a unique periodic structure formed by a row of overlaid rhombohedra of ZTO nanocrystals along the axis of the nanobranch. HRTEM studies displayed that the branches grew homoepitaxially as single-crystalline nanowires from the ZTO nanowire backbone. A possible growth model of the branched ZTO nanowires is discussed. To successfully prepare branched structures would provide an opportunity for both fundamental research and practical applications, such as three-dimensional nanoelectronics, and opto-electronic nanodevices.

Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

Mixed oxide photocatalysts, ZnO-Zn2SnO4 (ZnO-ZTO) nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrometer, and X-ray photoelectron spectra. The photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.

Single-Crystal and Twinned Zn2SnO4 Nanowires with Axial Periodical Structures

Single-crystal Zn2SnO4 (ZTO) nanowires were synthesized by thermal evaporation of a mixture of Zn and SnO powders at 1000 °C. The ZTO nanowires showed unique periodical structures in contrast to the traditional nanowires. It was found that the yield of the single-crystal ZTO nanowires was strongly dependent on the weight ratio of Zn and SnO in the source mixture. With the decrease of Zn content in the source, twinned ZTO nanowires with alternating (111) twins along the axial direction can be obtained. The formation mechanism of these ZTO nanostructures is discussed. The photoluminescence of the ZTO nanowires was measured.

A simple method to synthesize single-crystallineZn2SnO4 (ZTO) nanowires and their photoluminescence properties

Single-crystalline Zn2SnO4 (ZTO) nanowires have been successfully synthesized using a simple thermal evaporation methodby heating Zn and Sn powders directly without catalysts under a temperature lower than800 °C. The synthesized ZTO nanowires are ribbon-like, and have an average width of 100–200 nmand thickness of 50 nm. These nanowires are ultra-long, up to 0.5–1 mm. Further analysesindicate that the synthesized products are ZTO nanowires with a fairly high purity. Thesenanowires are highly single crystalline in the face-centred-cubic spinel structure, and growalong the direction. It is believed that the growth process of the nanowires follows a vapour–solidmechanism. Photoluminescence properties of the nanowires were measured, showing twogreen peaks at 529 and 544 nm and two yellow–orange emission peaks at 572 and 613 nm,which have not been reported before, besides the known blue–green peak (485 nm).

Growth and characterization of axially periodic Zn 2SnO 4 (ZTO) nanostructures

Transparent semiconductor Zn 2SnO 4 nanowires were synthesized for the first time by the thermal evaporation method. The nanowires show a unique periodic structure along the axis of the nanowire. By varying the Zn ratio in the reactants, ZTO nanowires with different morphologies can be achieved. High-resolution transmission microscopy (HRTEM) characterization confirms that the ZTO nanowires are crystalline. PL (photoluminescence) measurement of the ZTO nanowires reveals a green emission band centered at ∼493 nm. Our method provides a simple approach for assembling nanocrystals into one-dimensional periodic nanostructures. These nanostructures may have potential applications for opto-electronic nanodevices and nanosystems.