Single-crystalline Sb-doped SnO2 nanowires: synthesis and gas sensor application

Synthesis of ZnO Nanoflower Arrays on a Protrusion Sapphire Substrate and Application of Al-Decorated ZnO Nanoflower Matrix in Gas Sensors

In this study, we utilized a sapphire substrate with a matrix protrusion structure as a template. We employed a ZnO gel as a precursor and deposited it onto the substrate using the spin coating method. After undergoing six cycles of deposition and baking, a ZnO seed layer with a thickness of 170 nm was formed. Subsequently, we used a hydrothermal method to grow ZnO nanorods (NRs) on the aforementioned ZnO seed layer for different durations. ZnO NRs exhibited a uniform outward growth rate in various directions, resulting in a hexagonal and floral morphology when observed from above. This morphology was particularly evident in ZnO NRs synthesized for 30 and 45 min. Due to the protrusion structure of ZnO seed layer, the resulting ZnO nanorods (NRs) displayed a floral and matrix morphology on the protrusion ZnO seed layer. To further enhance their properties, we utilized Al nanomaterial to decorate the ZnO nanoflower matrix (NFM) using a deposition method. Subsequently, we fabricated devices using both undecorated and Al-decorated ZnO NFMs and deposited an upper electrode using an interdigital mask. We then compared the gas-sensing performance of these two types of sensors towards CO and H₂ gases. The research findings indicate that sensors based on Al-decorated ZnO NFM exhibit superior gas-sensing properties compared to undecorated ZnO NFM for both CO and H₂ gases. These Al-decorated sensors demonstrate faster response times and higher response rates during the sensing processes.

Improving Hazardous Gas Detection Behavior with Palladium Decorated SnO2 Nanobelts Networks

Transparent Conductive Oxides (TCOs) have been widely used as sensors for various hazardous gases. Among the most studied TCOs is SnO₂, due to tin being an abundant material in nature, and therefore being accessible for moldable-like nanobelts. Sensors based on SnO₂ nanobelts are generally quantified according to the interaction of the atmosphere with its surface, changing its conductance. The present study reports on the fabrication of a nanobelt-based SnO₂ gas sensor, in which electrical contacts to nanobelts are self-assembled, and thus the sensors do not need any expensive and complicated fabrication processes. The nanobelts were grown using the vapor-solid-liquid (VLS) growth mechanism with gold as the catalytic site. The electrical contacts were defined using testing probes, thus the device is considered ready after the growth process. The sensorial characteristics of the devices were tested for the detection of CO and CO₂ gases at temperatures from 25 to 75 °C, with and without palladium nanoparticle deposition in a wide concentration range of 40-1360 ppm. The results showed an improvement in the relative response, response time, and recovery, both with increasing temperature and with surface decoration using Pd nanoparticles. These features make this class of sensors important candidates for CO and CO₂ detection for human health.

Investigation of doping effects of different noble metals for ethanol gas sensors based on mesoporous In2O3

Elaborating the sensitization effects of different noble metals on In₂O₃has great significance in providing an optimum method to improve ethanol sensing performance. In this study, long-range ordered mesoporous In₂O₃has been fabricated through replicating the structure of SBA-15. Different noble metals (Au, Ag, Pt and Pd) with the same doping amount (1 at%) have been introduced by anin situdoping routine. The results of the gas sensing investigation indicate that the gas responses towards ethanol can be obviously increased by doping different noble metals. In particular, the best sensing performance towards ethanol detection can be achieved through Pd doping, and the sensors based on Pd-doped In₂O₃not only possess the highest response (39.0-100 ppm ethanol) but also have the shortest response and recovery times at the optimal operating temperature of 250 °C. The sensing mechanism of noble metal doped materials can be attributed to the synergetic effect combining 'catalysis' and 'electronic and chemical sensitization' of noble metals. In particular, the chemical state of the noble metal also has a great influence on the gas sensing mechanism. A detailed explanation of the enhancement of gas sensing performance through noble metal doping is presented in the gas sensing mechanism part of the manuscript.

Construction of Ag3PO4/SnO2 Heterojunction on Carbon Cloth with Enhanced Visible Light Photocatalytic Degradation

In this study, the Ag3PO4/SnO2 heterojunction on carbon cloth (Ag3PO4/SnO2/CC) was successfully fabricated via a facile two-step process. The results showed that the Ag3PO4/SnO2/CC heterojunction exhibited a remarkable photocatalytic performance for the degradation of Rhodamine B (RhB) and methylene blue (MB), under visible light irradiation. The calculated k values for the degradation of RhB and MB over Ag3PO4/SnO2/CC are 0.04716 min−1 and 0.04916 min−1, which are higher than those calculated for the reactions over Ag3PO4/SnO2, Ag3PO4/CC and SnO2/CC, respectively. The enhanced photocatalytic activity could mainly be attributed to the improved separation efficiency of photogenerated electron-hole pairs, after the formation of the Ag3PO4/SnO2/CC heterojunction. Moreover, carbon cloth with a large specific surface area and excellent conductivity was used as the substrate, which helped to increase the contact area of dye solution with photocatalysts and the rapid transfer of photogenerated electrons. Notably, when compared with the powder catalyst, the catalysts supported on carbon cloth are easier to quickly recycle from the pollutant solution, thereby reducing the probability of recontamination.

Epitaxial highly ordered Sb:SnO2 nanowires grown by the vapor liquid solid mechanism on m-, r- and a-Al2O3

Epitaxial, highly ordered Sb:SnO2 nanowires were grown by the vapor-liquid-solid mechanism on m-, r- and a-Al2O3 between 700 °C and 1000 °C using metallic Sn and Sb with a mass ratio of Sn/Sb = 0.15 ± 0.05 under a flow of Ar and O2 at 1 ± 0.5 mbar. We find that effective doping and ordering can only be achieved inside this narrow window of growth conditions. The Sb:SnO2 nanowires have the tetragonal rutile crystal structure and are inclined along two mutually perpendicular directions forming a rectangular mesh on m-Al2O3 while those on r-Al2O3 are oriented in one direction. The growth directions do not change by varying the growth temperature between 700 °C and 1000 °C but the carrier density decreased from 8 × 1019 cm-3 to 4 × 1017 cm-3 due to the re-evaporation and limited incorporation of Sb donor impurities in SnO2. The Sb:SnO2 nanowires on r-Al2O3 had an optical transmission of 80% above 800 nm and displayed very long photoluminescence lifetimes of 0.2 ms at 300 K. We show that selective area location growth of highly ordered Sb:SnO2 nanowires is possible by patterning the catalyst which is important for the realization of novel nanoscale devices such as nanowire solar cells.

High-Response Room-Temperature NO2 Sensor and Ultrafast Humidity Sensor Based on SnO2 with Rich Oxygen Vacancy

SnO₂ nanosheets with abundant vacancies (designated as SnO_{2- x}) have been successfully prepared by annealing SnSe nanosheets in Argon. The transmission electron microscopy results of the prepared SnO₂ nanosheets indicated that high-density SnO_{2- x} nanoplates with the size of 5-10 nm were distributed on the surface of amorphous carbon. After annealing, the acquired SnO_{2- x}/amorphous carbon retained the square morphology. The stoichiometric ratio of Sn/O = 1:1.55 confirmed that oxygen vacancies were abundant in SnO₂ nanosheets. The prepared SnO_{2- x} exhibited excellent performance of sensing NO₂ at room temperature. The response of the SnO_{2- x}-based sensor to 5 ppm NO₂ was determined to be 16 with the response time and recovery time of 331 and 1057 s, respectively, which is superior to those of most reported room-temperature NO₂ sensors based on SnO₂ and other materials. When the humidity varied from 30 to 40%, Δ R/ R was 0.025. The ultrafast humidity response (52 ms) and recovery (140 ms) are competitive compared with other state-of-art humidity sensors. According to the mechanistic study, the excellent sensing performance of SnO_{2- x} is attributed to its special structure.

Pd-loaded SnO2 hierarchical nanospheres for a high dynamic range H2S micro sensor

The sensitivity of Pd-loaded SnO₂ nanosphere sensor to H₂S gas: micro gas sensors based on Pd-loaded SnO₂ nanospheres have credible gas detection abilities down to 10 ppb and 4 orders of magnitude concentration detection ranges.

Optimization of the optical coupling in nanowire-based integrated photonic platforms by FDTD simulation

The optimized design of a photonic platform based on a nanowire light emitting diode (LED) and a nanowire photodetector connected with a waveguide is proposed. The light coupling efficiency from the LED to the detector is optimized as a function of the geometrical parameters of the system using the finite difference time domain simulation tool Lumerical. Starting from a design reported in the literature with a coupling efficiency of only 8.7%, we propose an optimized photonic platform with efficiency reaching 65.5%.

Remarkably Enhanced Room-Temperature Hydrogen Sensing of SnO₂ Nanoflowers via Vacuum Annealing Treatment

In this work, SnO₂ nanoflowers synthesized by a hydrothermal method were employed as hydrogen sensing materials. The as-synthesized SnO₂ nanoflowers consisted of cuboid-like SnO₂ nanorods with tetragonal structures. A great increase in the relative content of surface-adsorbed oxygen was observed after the vacuum annealing treatment, and this increase could have been due to the increase in surface oxygen vacancies serving as preferential adsorption sites for oxygen species. Annealing treatment resulted in an 8% increase in the specific surface area of the samples. Moreover, the conductivity of the sensors decreased after the annealing treatment, which should be attributed to the increase in electron scattering around the defects and the compensated donor behavior of the oxygen vacancies due to the surface oxygen adsorption. The hydrogen sensors of the annealed samples, compared to those of the unannealed samples, exhibited a much higher sensitivity and faster response rate. The sensor response factor and response rate increased from 27.1% to 80.2% and 0.34%/s to 1.15%/s, respectively. This remarkable enhancement in sensing performance induced by the annealing treatment could be attributed to the larger specific surface areas and higher amount of surface-adsorbed oxygen, which provides a greater reaction space for hydrogen. Moreover, the sensors with annealed SnO₂ nanoflowers also exhibited high selectivity towards hydrogen against CH₄, CO, and ethanol.

Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO₂, ZnO, and In₂O₃ are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C₂H₅OH and NO₂, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

A highly photoconductive composite prepared by incorporating polyoxometalate into perovskite for photodetection application

A photoconductive perovskite-polyoxometalate composite was prepared for the first time by a facile low-temperature and solution-processed method, and this composite exhibited a significantly enhanced photoconductivity and photodetection performance due to introduction of polyoxometalate into the perovskite for fine energy-level matching and efficient charge transfer.

Perovskite Nanoparticle-Sensitized Ga2O3 Nanorod Arrays for CO Detection at High Temperature

Noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La(0.8)Sr(0.2)FeO3 (LSFO) nanoparticle surface decoration on Ga2O3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts was of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga2O3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga2O3 nanorod surfaces with faster surface CO oxidation reactions.

Synergistic Effects of a Combination of Cr2O3-Functionalization and UV-Irradiation Techniques on the Ethanol Gas Sensing Performance of ZnO Nanorod Gas Sensors

There have been very few studies on the effects of combining two or more techniques on the sensing performance of nanostructured sensors. Cr2O3-functionalized ZnO nanorods were synthesized using carbothermal synthesis involving the thermal evaporation of a mixture of ZnO and graphite powders followed by a solvothermal process for Cr2O3-functionalization. The ethanol gas-sensing properties of multinetworked pristine and Cr2O3-functionalized ZnO nanorod sensors under UV illumination were examined to determine the effects of combining Cr2O3-ZnO heterostructure formation and UV irradiation on the gas-sensing properties of ZnO nanorods. The responses of the pristine and Cr2O3-functionalized ZnO nanorod sensors to 200 ppm of ethanol at room temperature by UV illumination at 2.2 mW/cm(2) were increased by 3.8 and 7.7 times, respectively. The Cr2O3-functionalized ZnO nanorod sensor also showed faster response/recovery and better selectivity than those of the pristine ZnO nanorod sensor at the same ethanol concentration. This result suggests that a combination heterostructure formation and UV irradiation had a synergistic effect on the gas-sensing properties of the sensor. The synergistic effect might be attributed to the catalytic activity of Cr2O3 for ethanol oxidation as well as to the increased change in conduction channel width accompanying adsorption and desorption of ethanol under UV illumination due to the presence of Cr2O3 nanoparticles in the Cr2O3-functionalized ZnO nanorod sensor.

Hierarchical ZnO Nanowires-loaded Sb-doped SnO2-ZnO Micrograting Pattern via Direct Imprinting-assisted Hydrothermal Growth and Its Selective Detection of Acetone Molecules

We propose a novel synthetic route by combining imprinting transfer of a Sb-doped SnO₂ (ATO)-ZnO composite micrograting pattern (MP), i.e., microstrip lines, on a sensor substrate and subsequent hydrothermal growth of ZnO nanowires (NWs) for producing a hierarchical ZnO NW-loaded ATO-ZnO MP as an improved chemo-resistive sensing layer. Here, ATO-ZnO MP structure with 3-μm line width, 9-μm pitch, and 6-μm height was fabricated by direct transfer of mixed ATO and ZnO nanoparticle (NP)-dispersed resists, which are pre-patterned on a polydimethylsiloxane (PDMS) mold. ZnO NWs with an average diameter of less than 50 nm and a height of 250 nm were quasi-vertically grown on the ATO-ZnO MP, leading to markedly enhanced surface area and heterojunction composites between each ATO NP, ZnO NP, and ZnO NW. A ZnO NW-loaded MP sensor with a relative ratio of 1:9 between ATO and ZnO (1:9 ATO-ZnO), exhibited highly sensitive and selective acetone sensing performance with 2.84-fold higher response (R_air/R_gas = 12.8) compared to that (R_air/R_gas = 4.5) of pristine 1:9 ATO-ZnO MP sensor at 5 ppm. Our results demonstrate the processing advantages of direct imprinting-assisted hydrothermal growth for large-scale homogeneous coating of hierarchical oxide layers, particularly for applications in highly sensitive and selective chemical sensors.

One-step synthesis and the enhanced xylene-sensing properties of Fe-doped MoO3 nanobelts

Pure and Fe-doped MoO₃ nanobelts were synthesized by a facile one-step hydrothermal method and their xylene-sensing properties were investigated.

Superhydrophobic and H2S gas sensing properties of CuO nanostructured thin films through a successive ionic layered adsorption reaction process

Superhydrophobic surfaces of CuO were synthesized using a successive ionic-layered adsorption reaction technique by varying the number of deposition cycles followed by a thermal annealing process.

Nanowire Chemical/Biological Sensors: Status and a Roadmap for the Future

Chemiresistive sensors are becoming increasingly important as they offer an inexpensive option to conventional analytical instrumentation, they can be readily integrated into electronic devices, and they have low power requirements. Nanowires (NWs) are a major theme in chemosensor development. High surface area, interwire junctions, and restricted conduction pathways give intrinsically high sensitivity and new mechanisms to transduce the binding or action of analytes. This Review details the status of NW chemosensors with selected examples from the literature. We begin by proposing a principle for understanding electrical transport and transduction mechanisms in NW sensors. Next, we offer the reader a review of device performance parameters. Then, we consider the different NW types followed by a summary of NW assembly and different device platform architectures. Subsequently, we discuss NW functionalization strategies. Finally, we propose future developments in NW sensing to address selectivity, sensor drift, sensitivity, response analysis, and emerging applications.

SnO2 highly sensitive CO gas sensor based on quasi-molecular-imprinting mechanism design

Response of highly sensitive SnO₂ semiconductor carbon monoxide (CO) gas sensors based on target gas CO quasi-molecular-imprinting mechanism design is investigated with gas concentrations varied from 50 to 3000 ppm. SnO₂ nanoparticles prepared via hydrothermal method and gas sensor film devices S_C (exposed to the target gas CO for 12 h after the suspension coating of SnO₂ film to be fully dried, design of quasi-molecular-imprinting mechanism, the experiment group) and S_A (exposed to air after the suspension coating of SnO₂ film to be fully dried, the comparison group) made from SnO₂ nanoparticles are all characterized by XRD, SEM and BET surface area techniques, respectively. The gas response experimental results reveal that the sensor S_C demonstrates quicker response and higher sensitivity than the sensor S_A does. The results suggest that in addition to the transformation of gas sensor materials, surface area, and porous membrane devices, the Molecular Imprinting Theory is proved to be another way to promote the performance of gas sensors.

A miniature room temperature formaldehyde sensor with high sensitivity and selectivity using CdSO4 modified ZnO nanoparticles

A light activated miniature formaldehyde sensor working at room temperature is fabricated by CdSO₄ modified ZnO nanoparticles.

Room temperature, ppb-level NO2 gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination

Reports of the gas sensing properties of ZnSe are few, presumably because of the decomposition and oxidation of ZnSe at high temperatures. In this study, ZnSe nanowires were synthesized by the thermal evaporation of ZnSe powders and the sensing performance of multiple-networked ZnSe nanowire sensors toward NO2 gas was examined. The results showed that ZnSe might be a promising gas sensor material if it is used at room temperature. The response of the ZnSe nanowires to 50 ppb-5 ppm NO2 at room temperature under dark and UV illumination conditions were 101-102% and 113-234%, respectively. The responses of the ZnSe nanowires to 5 ppm NO2 increased from 102 to 234% with increasing UV illumination intensity from 0 to 1.2 mW/cm(2). The response of the ZnSe nanowires was stronger than or comparable to that of typical metal oxide semiconductors reported in the literature, which require higher NO2 concentrations and operate at higher temperatures. The origin of the enhanced response of the ZnSe nanowires towards NO2 under UV illumination is also discussed.

Effects of Mg doping on optical and CO gas sensing properties of sensitive ZnO nanobelts

We report the synthesis, optical characterization and enhanced carbon monoxide (CO) gas sensing properties of magnesium (Mg) doped 1D zinc oxide (ZnO) nanobelts obtained via a vapor transport method.

Fabrication of a transparent ultraviolet detector by using n-type Ga2O3 and p-type Ga-doped SnO2 core-shell nanowires

This study investigates the feasibility of synthesizing high-density transparent Ga(2)O(3)/SnO(2):Ga core-shell nanowires on a sapphire substrate at 1000 °C by VLS. The doping Ga concentrations are 0.46, 1.07, 2.30 and 17.53 atomic%. The XRD spectrum and HR-TEM reveal Ga(2)O(3) and SnO(2) as having monoclinic and tetragonal rutile structures, respectively. Experimental results indicate that the XRD peak shift of SnO(2) to a larger angle increases with the increasing amount of Ga doping. According to the CL spectrum, SnO(2) and Ga(2)O(3) peak at approximately 528-568 nm and 422-424 nm, respectively. The maximum quantum efficiency of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 0.362%. The UV light on-off current contrast ratio of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 1066.7 at a bias of 5 V. Moreover, the dynamic response of Ga(2)O(3)/SnO(2):Ga core-shell nanowires has an on-off current contrast ratio of around 16. Furthermore, the Ga(2)O(3) region functions similar to a capacitor and continues to accumulate SnO(2):Ga excited electrons under UV light exposure.

Low-voltage SnO₂ nanowire transistors gated by solution-processed chitosan-based proton conductors

Recently, a bioprotonic field-effect transistor with chitosan nanowire channel was demonstrated [Nat. Commun., 2011, 2, 476]. Here, it is interesting to find that solution-processed chitosan films with a large electric-double-layer (EDL) specific capacitance can also be used as the gate dielectrics for low-voltage individual SnO(2) nanowire transistors. The field-effect electron mobility, current on/off ratio and sub-threshold slope of such a hybrid SnO(2) nanowire device is estimated to be 128 cm(2) V(-1) s(-1), 2.3 × 10(4) and 90 mV per decade, respectively. Such low-voltage nanowire EDL transistors gated by chitosan-based proton conductors are promising for nanosensors and bioelectronics.

One-Dimensional SnO2Nanostructures: Synthesis and Applications

Nanoscale semiconducting materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, like nanowires, nanobelts, and nanotubes, have gained tremendous attention within the past decade. Among the variety of 1D nanostructures, tin oxide (SnO2) semiconducting nanostructures are particularly interesting because of their promising applications in optoelectronic and electronic devices due to both good conductivity and transparence in the visible region. This article provides a comprehensive review of the recent research activities that focus on the rational synthesis and unique applications of 1D SnO2nanostructures and their optical and electrical properties. We begin with the rational design and synthesis of 1D SnO2nanostructures, such as nanotubes, nanowires, nanobelts, and some heterogeneous nanostructures, and then highlight a range of applications (e.g., gas sensor, lithium-ion batteries, and nanophotonics) associated with them. Finally, the review is concluded with some perspectives with respect to future research on 1D SnO2nanostructures.

Nanoparticles of antimony doped tin dioxide as a liquid petroleum gas sensor: effect of size on sensitivity

The gas sensitivity exhibited by nanoparticles of 1 wt% Pd catalysed antimony doped tin dioxide (ATO) prepared by a citrate-nitrate process is reported here. The reduction of particle size to <3 nm, a dimension smaller than double the thickness of the charge depletion layer, has resulted in an exceptionally high butane sensitivity and selectivity. The sensitivity and selectivity of ATO particles of different sizes unequivocally proved that reducing the size of particles to below twice the Debye length dimension produces materials with exceptionally high sensitivity and selectivity for sensor applications. The sensitivity of the samples towards 1000 ppm butane varied in the order 98%>55%>47%, for CNP>SP>CP samples having crystallite sizes of the order of 2.4 nm to 18 nm to 25 nm, respectively. The ATO nanoparticles exhibited not only a remarkable increase in gas sensitivity of around 98% towards 1000 ppm butane at 350 °C, but also a preferential selectivity to butane compared to other gases such as CO, CO2, SO2, CH4 and H2. In addition to the exceptionally high sensitivity and selectivity, the developed sensors also exhibited an improved response time and long term stability, which are of paramount importance for practical device development.

High gas sensing performance of one-step-synthesized Pd-ZnO nanoflowers due to surface reactions and modifications

Pd-ZnO nanoflowers with high uniformity were prepared via a novel one-step hydrothermal route. High sensitivity, fast response, high selectivity and low work temperature are obtained from Pd-ZnO nanoflower sensors. The sensitivity upon exposure to 300 ppm ethanol is up to 168 at 300  °C and maintains 2.6 at 120  °C. Such behaviors can be attributed to Schottky contact at the Pd/ZnO interface and catalytic activity of Pd nanoparticles. The present results open a way for uniform surface modification of one-dimensional nanostructures with Pd nanoparticles and further enhancing their gas sensing performance.

Preparation of LaFeO3 nanofibers by electrospinning for gas sensors with fast response and recovery

LaFeO(3) nanofibers are successfully prepared by the electrospinning method. XRD patterns show that the materials belong to a cubic system. After calcination at 600 °C for 3 h, SEM photographs show that the diameters of the nanofibers are about 80-90 nm and their surfaces are smooth. The response-recovery properties of an LaFeO(3) nanofiber sensor to ethanol are better than those of an LaFeO(3) nanobelt and nanoparticle sensor. LaFeO(3) nanofibers have relatively low resistance, and they improve the weakness of LaFeO(3) nanoparticles upon application. An LaFeO(3) nanofiber sensor also has good reversibility and selectivity to ethanol and is a very good p-type semiconductor material.

Selective detection of NO2 and C2H5OH using a Co3O4-decorated ZnO nanowire network sensor

The selective detection of two different gases, NO(2) and C(2)H(5)OH, has been achieved using a p-type Co(3)O(4)-decorated n-type ZnO nanowire (NW) network sensor. The gas selectivity was explained by the catalytic effect of nanocrystalline Co(3)O(4) and the extension of the electron depletion layer via the formation of p-n junctions.

One-dimensional boron nanostructures: Prediction, synthesis, characterizations, and applications

One-dimensional (1D) boron nanostructures are very potential for nanoscale electronic devices since their physical properties including electric transport and field emission have been found very promising as compared to other well-developed 1D nanomaterials. In this article, we review the current progress that has been made on 1D boron nanostructures in terms of theoretical prediction, synthetic techniques, characterizations and potential applications. To date, the synthesis of 1D boron nanostructures has been well-developed. The popular structures include nanowires, nanobelts, and nanocones. Some of these 1D nanostructures exhibited improved electric transport properties over bulk boron materials as well as promising field emission properties. By current experimental findings, 1D boron nanostructures are promising to be one of core materials for future nanodevices. More efforts are expected to be made in future on the controlled growth of 1D boron nanostructures and tailoring their physical properties.

A room temperature ethanol sensor made from p-type Sb-doped SnO2 nanowires

A p-type ethanol sensor with a response time of approximately 8.3 s at room temperature was produced by SnO(2):Sb nanowires. The electrical properties of p-type SnO(2) nanowires are stable with a hole concentration of 1.544 x 10(17) cm(-3) and a field-effect mobility of 22 cm(2) V(-2) S(-1). X-ray photoelectron spectroscopy (XPS) and Hall measurement revealed that as-synthesized nanowires exhibit p-type behavior. A comprehensive investigation of the p-type sensing mechanism is reported.