Rice Husk Templated Mesoporous ZnO Nanostructures for Ethanol Sensing at Room Temperature

Mesoporous zinc oxide nanostructures are successfully synthesized via the sol-gel route by using a rice husk as the template for ethanol sensing at room temperature. The structure and morphology of the nanostructures are characterized by x-ray diffraction, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and nitrogen adsorption-desorption analyses. The mechanism for the growth of zinc oxide nanostructures over the biotemplate is proposed. SEM and TEM observations also reveal the formation of spherical zinc oxide nanoparticles over the interwoven fibrous network. Multiple sized pores having pore diameter ranging from 10- 4Ohm is also evidenced from the pore size distribution plot. The larger surface area and porous nature of the material lead to high sensitivity （40.93% for 300 ppm of ethanol）, quick response （42s） and recovery （40 s） towards ethanol at 30014. The porous nature of the interwoven fibre-like network affords mass transportation of ethanol vapor, which results in faster surface accessibility, and hence it acts as a potential candidate for ethanol sensing at room temperature.

Synthesis and characterization of ZnO nanostructures prepared by a thermal evaporation process

A series of ZnO nanostructures such as nanowires,nanobelts,nanocombs and mesoporous nanoballs were fabricated by a simple carbon reduction method without catalyst.The morphologies and microstructures of all samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and energy dispersive X-ray spectroscopy.The results indicate that different deposition temperatures have great impact on different shapes of ZnO nanostructures.The growth mechanisms of these ZnO nanostructrues suggest that,by controlling the experiment parameters,different morphological configurations nanostructures can be fabricated.

Controlling Growth of ZnO Nanostructures Via A Solution Route

A solution method was developed for fabricating ZnO nanostructures using （NH4）2CO3 as starting material SEM analysis shows that ZnO nanostructures exhibit nanorod, branch and flower-like morphologies. The crystal phase of as-synthesized products was characterized by X-ray diffraction （XRD）. The growth process, formation mechanism and optical property were also discussed by means of transmission electronic microscopy （TEM）, high resolution transmission microscopy （HRTEM） and photoluminescence （PL）. The growth direction of ZnO nanostructures was investigated based on the results of HRTEM. The PL spectrum shows two strong peaks （centered at around -387 and -470 nm） and a broad Deak （centered at around -580 nm）.

Zinc Oxide Nanostructures for NO_2 Gas–Sensor Applications:A Review

Because of the interesting and multifunctional properties,recently,ZnO nanostructures are considered as excellent material for fabrication of highly sensitive and selective gas sensors.Thus,ZnO nanomaterials are widely used to fabricate efficient gas sensors for the detection of various hazardous and toxic gases.The presented review article is focusing on the recent developments of NO2gas sensors based on ZnO nanomaterials.The review presents the general introduction of some metal oxide nanomaterials for gas sensing application and finally focusing on the structure of ZnO and its gas sensing mechanisms.Basic gas sensing characteristics such as gas response,response time,recovery time,selectivity,detection limit,stability and recyclability,etc are also discussed in this article.Further,the utilization of various ZnO nanomaterials such as nanorods,nanowires,nano-micro flowers,quantum dots,thin films and nanosheets,etc for the fabrication of NO2gas sensors are also presented.Moreover,various factors such as NO2concentrations,annealing temperature,ZnO morphologies and particle sizes,relative humidity,operating temperatures which are affecting the NO2gas sensing properties are discussed in this review.Finally,the review article is concluded and future directions are presented.

Zinc Oxide Nanostructured Biosensor for Glucose Detection

Zinc oxide （ZnO） nanocombs were fabricated by vapor phase transport, and nanorods and hierarchical nanodisk structures by aqueous thermal decomposition. Glucose biosensors were constructed using these ZnO nanostructures as supporting materials for glucose oxidase （GOX） loading. These ZnO glucose biosensors showed a high sensitivity for glucose detection and high affinity of GOX to glucose as well as the low detection limit. The results demonstrate that ZnO nanostructures have potential applications in biosensors.

Rapid Synthesis of Piezoelectric ZnO-Nanostructures for Micro Power-Generators

In this paper, we report a rapid synthesis of piezoelectric ZnO-nanostructures and fabrication of the nanostructures- based power-generators demonstrating an energy conversion from an environmental mechanical/ultrasonic energy to an electrical energy. The ZnO nanostructures are grown on a silicon wafer by a modified chemical solution method （CSD, chemical-solution-deposition） with a two-step thermal-oxidation approach. The synthesis process can be completed within 1 h. By varying the mixture-ratio of Zn micro-particles in an oxalic acid solution with 0.75 mol/l concentration in the CSD process, the growth mechanism is well-controlled to synthesize three different types of ZnO-nanostructures （i.e., dandelion-like nanostructures, columnar nanostructures, and nanowires）. Furthermore, through oxidizing at different temperatures in the thermal-oxidation process, the featured geometry of the nanostructures （e.g., the length and diameter of a nanowire） is modified. The geometry, size, morphology, crystallization, and material phase of the modified nanostructures are characterized by scanning electron microscopy and X-ray diffraction. Finally, the nanostructures are used to fabricate several micro power-generators. Through the piezoelectric effect, a maximum current density output of 0.28 μA cm-2 generated by a power-generator under an ultrasonic wave is observed.

Annealing effects on the structural and optical properties of ZnO nanoparticles with PVA and CA as chelating agents

The effects of annealing temperatures and chelating agents on the structural and optical properties of ZnO nanoparticles were investigated.The average particle size of ZnO nanoparticles increased with increase of annealing temperatures.The decrease of the full width at half maximum(FWHM)with increasing annealing temperatures inferred increase of particle/grain growth.The grain sizes were also observed to be increased with increase of annealing temperatures.From the absorption spectra of the samples,the absorption was red-shifted and the energy band gap was blue-shifted with increase of annealing temperatures.A sharp UV emission peak was observed and the intensity of this peak increased with annealing temperatures corresponding to the high crystallinity in the samples.At high annealing temperature of 700℃,ZnO exhibited a less intense deep level emission.This negligible deep level emission was attributed to the oxygen vacancies created at higher annealing temperatures.

Solvent-less synthesis of zinc oxide nanostructures from Zn(salen) as precursor and their optical properties

ZnO nanoparticles, 10-20 nm in size, were synthesized by heat treatment in air at 500 ℃ for 5 h., using [N,N＇-bis（salicylaldehydo） ethylene diamine]zinc（II）, i.e., Zn（salen）, as precursor, which was obtained by a solvent-flee solid-solid reaction. Heat-treated products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Room temperature photoluminescence spectra of ZnO nanostructures are dominated by green emission attributed to oxygen vacancy related donor-acceptor transition.

Synthesis and Characterization of ZnO Nanowires and ZnO–CuO Nanoflakes from Sputter-Deposited Brass(Cu_(0.65)–Zn_(0.35)) Film and Their Application in Gas Sensing

A novel method was presented for synthesis of ZnO and ZnO-CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass （Cu0.65-Zn0.35） films were deposited on oxidized Si substrate by radio frequency （RF） diode sputtering. Subsequently, these films having thickness in the range of 100-200 nm were oxidized in different oxidizing ambient in the temperature range of 300-550 ℃. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and photoluminescence （PL） techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy （XPS）. The synthesized nanowires had diameter in the range of 60-100 nm and length up to 50 μm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be -150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance Of the sensor was investigated for different nanostructured materials for various volatile organic compounds （VOCs）, It was observed that ZnO- CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.

Effect of Annealing Temperature on the Morphology and Sensitivity of the Zinc Oxide Nanorods-Based Methane Senor

ZnO nanorods in the form of thin films were synthesized by a facile chemical route and the effect of annealing temperature on the structure and sensitivity of such ZnO-based sensors was studied in detail towards methane sensing.Morphological analyses of such films were carried out by scanning electron microscopy,whereas,the crystalline structure and phase purity of the films were analysed by X-ray diffraction technique.The films were observed to display a gradual change in their morphology from granular to dense nanorods and each of them was used to fabricate methane sensor prototype.They were also tested for temperature-dependent methane-sensing capability with varying methane concentrations.The optimized sensor exhibited highest gas response of ＊80% at 250 °C with significantly low response and recovery time.