Experimental and theoretical investigation of ligand effects on the synthesis of ZnO nanoparticles

ZnO nanoparticles with highly controllable particle sizes(less than 10 nm) were synthesized using organic capping ligands in Zn(Ac)2 ethanolic solution. The molecular structure of the ligands was found to have significant influence on the particle size. The multi-functional molecule tris(hydroxymethyl)-aminomethane (THMA) favoured smaller particle distributions compared with ligands possessing long hydrocarbon chains that are more frequently employed. The adsorption of capping ligands on ZnnOn crystal nuclei (where n = 4 or 18 molecular clusters of(0001) ZnO surfaces) was modelled by ab initio methods at the density functional theory (DFT) level. For the molecules examined, chemisorption proceeded via the formation of Zn...O, Zn...N, or Zn...S chemical bonds between the ligands and active Zn2+ sites on ZnO surfaces. The DFT results indicated that THMA binds more strongly to the ZnO surface than other ligands, suggesting that this molecule is very effective at stabilizing ZnO nanoparticle surfaces. This study, therefore, provides new insight into the correlation between the molecular structure of capping ligands and the morphology of metal oxide nanostructures formed in their presence

Zinc oxide nanostructures with carbon nanotube and gold additives for co gas sensing application

Abstract: Zinc oxide (ZnO) nanostructures were synthesised for gas sensing application. In an attempt to improve the surface area and the electrical conductivity of the ZnO, nanomaterials such as the carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) were used separately to produce CNTs/ZnO and Au/ZnO nanocomposites, respectively. The addition of these nanomaterials onto the ZnO nanostructures significantly improved the gas sensing properties such as the sensitivity and response time. Synthesis of gold nanoparticles was successfully achieved via gold salt (HAuCl4.3H2O) reduction using the Turkevich method. Citrate molecules were used as the stabiliser and to systematically control the sizes of the AuNPs. The sizes of AuNPs were found to increase from 14 nm to 40 nm when the concentration of citrate ions was reduced from 1 mM to 0.3 mM. The size distribution of AuNPs was relatively wider as the particle size increased. The synthesized AuNPs were stable for over a period of 4 weeks. Carbon nanotubes synthesis was achieved using chemical vapour deposition (CVD) method using acetylene gas as the carbon source and ferrocene as the catalyst. An increase in the flowrate of the precursor gas (acetylene) yielded an increase in amorphous carbon, which was attached to the walls of the carbon nanotubes. The optimum flowrate of acetylene was found to be 150 m3/min that yielded CNTs with an average diameter of 95 nm and a relatively narrow size distribution. The hydrothermal chemical precipitation method was used to synthesise ZnO nanostructures. Zinc sulphate (ZnSO4) and sodium hydroxide (NaOH) were used as a metal precursor and reducing agent, respectively. The NaOH concentration of 0.3 M yielded ZnO nanosheets with relatively the highest surface area of 102 m2/g. Gas sensing analysis was conducted using carbon monoxide (CO) gas at 250°C. The sensitivity and response time were calculated to be 9.8% and 114 seconds, respectively, at a CO concentration of 200 ppm. The composites CNTs/ZnO and Au/ZnO were prepared, separately. The average surface area of the Au/ZnO composite was 131 m2/g and that of CNTs/ZnO composite was 153 m2/g. The CNTs/ZnO composite showed an optimum sensitivity of 9.9% and the response time of 49 seconds when exposed to 200 ppm of CO gas at 250°C.M.Tech. (Chemical Engineering

Enhanced UV and ethanol vapour sensing of a single 3-D ZnO tetrapod alloyed with Fe2O3 nanoparticles

Fabrication of multifunctional devices based on nano- and microstructures of a single semiconducting oxide is an important step for a better understanding of their maximum sensing properties and the base for the development of bottom-up nanotechnologies. In this work we have fabricated, for the first time devices based on a single or two interconnected ZnO tetrapods (T), doped with Fe and alloyed with Fe2O3 nanoparticles (NPs) and microparticles (MPs) in order to improve their sensing properties towards ultraviolet (UV) sensing and ethanol vapour (EtOH). Compared to pristine ZnO-T improved UV and gas sensing properties of Fe-doped ZnO-T were observed. By Fe2O3-alloying of Fe-doped ZnO-T further improvement in sensing properties was obtained with a reduced influence of the relative humidity (RH) on the sensing response. A gas sensing mechanism was proposed and discussed in detail based on the alloyed Fe2O3 NPs and MPs. The results presented here demonstrate the efficiency of doping and alloying of single ZnO microstructures with other semiconducting oxides to improve their sensing properties, including the decrease in influence of RH on the gas response and the rapidity of the sensors

Synthesis of Metal Oxide Semiconductor Nanostructures for Gas Sensors

Zinc oxide (ZnO) is a unique and important metal oxide semiconductor for its valuable and huge applications with wide band gap ( 3.37 eV) and most promising candidate for gas sensor due to its high surface-to-volume ratio, good biocompatibility, stability, and high electron mobility. Due these properties, metal oxide shows good crystallinity, higher carrier mobility, and good chemical and thermal stability at moderately high temperatures. In this chapter nanostructures have been investigated, main focus being their synthesis and sensing mechanism of different toxic chemicals, synthesized by thermal evaporation through vapor transport method using vapor-liquid-solid (VLS) mechanism. The doped ZnO nanobelts showed significant enhanced sensing properties at room temperature, indicating that doping is very much effective in improving the methane CH4 sensing of ZnO nanostructures. ZnO nanowires showed a remarkable sensing response toward acetone and CH4 gas

Growth of ZnO nanowire and its application as UV photodetector

Zinc Oxide (ZnO) nanostructures with their significant properties have various application in optoelectronics, sensor devices and energy conversion devices. This report includes deposition of ZnO film by rf reactive sputtering on glass substrate. Its analysis using XRD, FESEM and UV-VIS spectroscopy to study its morphology, crystal structure, band gap and transmittance. Further, the deposited film is taken as substrate for the growth of ZnO nanowires using Hydrothermal Method. Various parameters affecting the growth conditions like growth temperature, growth time, and precursor concentration have been studied and optimizations of reaction conditions are done. Analysis of the samples fabricated under different conditions is carried out using XRD and FESEM characterization techniques. Zinc oxide nanowires have their application as UV photodetector due to their wide band gap and high surface to volume ratio. To enhance the absorption ability, carrier concentration and photoresponse, Zinc Oxide nanowires surface is functionalized using Poly(vinyl alcohol) for the application of UV photodetector. Photoresponse and sensitivity is studied for both coated and uncoated, using I-V characterization. To analyse optical switching action under the illumination of UV light photoresponse of these nanowires is plotted with respect to the time

Zinc Oxide Nanostructures: Synthesis and Characterization

The summary should be ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Zinc oxide (ZnO) is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It has been used considerably for its catalytic, electrical, optoelectronic, and photochemical properties. ZnO nanomaterials, such as quantum dots, nanorods, and nanowires, have been intensively investigated for their important properties. Many methods have been described in the literature for the production of ZnO nanostructures, such as laser ablation, hydrothermal methods, electrochemical deposition, sol-gel methods, chemical vapour deposition, molecular beam epitaxy, the common thermal evaporation method, and the soft chemical solution method. The present Special Issue is devoted to the synthesis and characterization of ZnO nanostructures with novel technological applications.

TiO2 nanotubes for room temperature toluene sensor

TiO2 nanotubes were used to prepare gas sensor and the gas sensing properties towards toluene were analyzed. Titania nanotube arrays were fabricated via electrochemical anodization method in glycerol electrolytes containing NH4F. The sensor fabricated from these nanotubes exhibits a good response to toluene at room temperature with good sensitivity. The toluene sensing properties were tested from 20 to 150 ppm concentrations.Fil: Perillo, Patricia Maria. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; ArgentinaFil: Rodriguez, Daniel Fabian. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; ArgentinaFil: Boggio, Norberto Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; Argentin