Effect of refluxing time on the morphology of pencil like zinc oxide nanostructures prepared by solution method

This paper presents the fabrication of pencil like zinc oxide nanorods by solution method using precursor zinc acetate di-hydrate (Zn(Ac)₂.2H₂O) and alkali sodium hydroxide (NaOH) at a very low refluxing temperature (75 °C) for different ageing/ refluxing (12 h, 24 h, 36 h, 48 h and 60 h) time intervals. The morphological observation was carried out by using Field Emission Scanning Electron Microscopy (FESEM). The FESEM revealed that as the aging/refluxing time increased, the size (length and diameter) of the zinc oxide nanorods also increased. Furthermore, the morphology and crystallinity of the products grown were also confirmed by Transmission Electron Microscopy (TEM), high-resolution TEM, and Selected Area Electron Diffraction (SAED) patterns, which indicated that grown pencils grew along a [0001] direction with an ideal lattice fringe distance of ∼0.52 nm. The optical properties of the grown pencil-like zinc oxide nanorods were characterized by using UV-vis spectroscopy. Strong absorbance peaks were observed at ∼375 nm to 378 nm, which is the characteristic peak for the wurtzite hexagonal phase of ZnO. The FTIR spectroscopic measurement showed a standard peak of zinc oxide in the range of 428 cm⁻¹ to 520 cm⁻¹. Additionally, on the basis of chemical and morphological analysis, we have also proposed a possible growth mechanism for pencillike zinc oxide nanostructures.     

Room temperature ferromagnetism of boron-doped ZnO nanoparticles prepared by solvothermal method

In this study, B-doped ZnO nanoparticles were synthesized by template-free solvothermal method. X-ray diffraction analysis reveals that B-doped ZnO nanoparticles have hexagonal wurtzite structure. Field emission scanning electron microscopy observations show that the nanoparticles have a diameter of 50 nm. The room temperature ferromagnetism increases monotonically with increasing B concentration to the ZnO nanoparticles and reaches the maximum value of saturation magnetization 0.0178 A·m2 ·kg-1 for 5 % B-doped ZnO nanoparticles. Moreover, photoluminescence spectra reveal that B doping causes to produce Zn vacancies (VZn ). Magnetic moment of oxygen atoms nearest to the B-VZn vacancy pairs can be considered as a source of ferromagnetism for B-doped ZnO nanoparticles.     

Effect of Co substitution on the structural and optical properties of ZnO nanoparticles synthesized by sol-gel route

Co doped ZnO nanoparticles were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDAX), UV-Visible absorption spectroscopy and Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the formation of single phase structure of all samples which was further supported by FTIR data. With the increase in Co concentration from 0% to 5%, crystallite size was observed to vary from 27.1 to 21.3 nm. It suggests the prevention of crystal growth as a result of Co doping in ZnO. It was also evident from the absorption spectra that the absorbance tends to increase with the increase in dopant concentration. Optical band gap was found to increase slightly with the increase in Co content, confirming the size reduction as a result of Co doping.     

XPS and IR study of electrochemically or chemically redoped poly(3-methylthienylene) films

XPS (X-ray photoemission spectroscopy) and IR (infrared) analyses of poly(3-methylthienylene) films, electrochemically or chemically redoped0 with various chemical species at varying doping levels, have been investigated. On the basis of these results, the major chemical species of dopants have been identified. As a results, the dopant content was determined and the poly(3-methylthienylene) films were classified as light or heavy by doping level. The conductivity ranged from about 10^?12 to 10₂ S cm^?1 for all the films investigated. The conductivity and the activation energy of conduction for the heavily-doped films vary as a function of the dopant content, independent of the different chemical species of dopants. In particular, a sudden change is observed in the dependence of activation energy on dopant content. This sudden change may be associated with the semi-conductor-metal transition. Furthermore, it is shown that the specific absorption bands in the infrared are induced by the doping, intensified with increasing dopant uptake and accompanied by an increase in conductivity.     

Structural and optical study of samarium doped cerium oxide thin films prepared by electron beam evaporation

Samarium doped cerium oxide films were grown on the glass substrate using e-beam deposition technique and then characterized using different techniques: X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and UV-visible spectroscopy measurements. XRD analysis shows that all the films have cubic structure and the crystallite size decreases from 18 to 13 nm as the samarium (Sm) concentration increases. The FE-SEM images indicate that all the films have columnar growth. UV-visible measurements reflect that the films have high transparency (>80%) in the visible region. From the Raman spectra, we have observed two peaks at 466 and 565 cm⁻¹. The peak at 466 cm⁻¹ is assigned to the F_2g mode of cerium oxide (CeO₂) whereas the peak at 565 cm⁻¹ is due to the presence of the oxygen vacancies. The increase in the intensity of the peak at 565 cm⁻¹ indicates that the oxygen vacancy increases with Sm doping.     

Fourier transform infrared study of electrochemically prepared polythienylene films with varying doping levels

Fourier transform infrared (FTIR) spectra of electrochemically prepared polythienylene films doped with various dopant species at varying doping levels have been obtained. These doped polythienylene films exhibit four conspicuous absorption bands at 1330 - 1310, 1200, 1220 - 1080 and 1030 - 1020 cm^?1 made IR active and/or given prominent intensity due to the doping, independent of the difference in dopant species and contents. On the other hand, the bands specific to each dopant species are distinctly observable for the heavily-doped polythienylene films. Some typical band profiles in accordance with varied doping levels will be presented.     

Synthesis and characterization of Er doped CaF2 nanoparticles

Er³⁺ doped CaF₂ nanoparticles were synthesized by a chemical co-precipitation method. Effect of the dopant concentrations on the structure and optical properties of the CaF₂ nanoparticles was investigated. The X-ray powder diffraction and transmission electron microscopy analysis was used to characterize the structure and morphology of the nanoparticles. The nanoparticles with different dopant concentration exhibited a sphere-like morphology with diameters of about 8-36 nm. The incorporation of Er³⁺ ions into CaF₂ resulted in the decrease in grain size and deterioration of crystallinity, but enlarged the lattice constants of CaF₂. Additional annealing treatment at 400 °C to the prepared CaF₂ removed the NO₃⁻ and OH⁻ groups adsorbed on the particles’ surfaces, and improved the optical properties of the nanoparticles. The fluorescence intensity, with a maximum at approximately 0.4 mol%, decreased with the increase in doping concentration because of concentration quenching.     

Optical and electrical properties of zinc oxide thin films with low resistivity via Li-N dual-acceptor doping

Zinc oxide thin films with low resistivity have been deposited on glass substrates by Li-N dual-acceptor doping method via a modified successive ionic layer adsorption and reaction process. The thin films were systematically characterized via scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, ultraviolet-visible spectrophotometry and fluorescence spectrophotometry. The resistivity of zinc oxide film was found to be 1.04 Ω cm with a Hall mobility of 0.749 cm² V⁻¹ s⁻¹ and carrier concentration of 8.02 × 10¹⁸ cm⁻³. The Li-N dual-acceptor doped zinc oxide films showed good crystallinity with prior c-axis orientation, and high transmittance of about 80% in visible range. Moreover, the effects of Li doping level and other parameters on crystallinity, electrical and ultraviolet emission of zinc oxide films were investigated.     

Enhancing the Antibacterial Efficiency of ZnO Nanopowders Synthesized by Combustion Method Through Ag + Fe Co-doping

(Ag + Fe)-doped ZnO nanopowders have been synthesized using combustion method. Ag doping level was kept as 2 at.%, and Fe doping level was varied from 3 to 6 at.%, and the structural, optical, surface morphological, and antibacterial properties have been investigated. The structural studies show that ZnO/(Ag + Fe) nanopowders have hexagonal wurtzite structure with a preferential orientation along the (101) plane. The FE-SEM images indicate that there is a gradual decrease in the grain size with the increase in the doping level of Fe, and the TEM images are correlated well with FE-SEM images. The XPS profile clearly confirms the presence of expected elemental composition. Photoluminescence studies reveal the presence of extrinsic defects in the material. Antibacterial activity of Ag- and Fe-doped ZnO nanopowders against Vibrio parahaemolyticus, Vibrio Cholerae, and Staphylococcus aureus bacteria was also investigated.     

Effect of pH on Crystal Size and Photoluminescence Property of ZnO Nanoparticles Prepared by Chemical Precipitation Method

The effects of pH value on crystal size and optical property of zinc oxide nanoparticles prepared by chemical precipitation method were investigated.Prepared samples have been characterized by means of X-ray diffraction,scanning electron microscopy,ultraviolet-visible spectrometer and photoluminescence spectrometer.From X-ray diffraction profile,it is found that the particle size of sample increases from 13.8 to 33 nm when the pH value of the solution was increased from 6 to 13.Microstructural study also shows that the particle size increases with pH value.Hexagonal shape of the zinc oxide nanoparticle has been confirmed by the scanning electron microscopy image.The recorded ultraviolet-visible spectrum shows excitonic absorption peaks around 381 nm.The energy gap of the prepared samples has been determined from the ultraviolet-visible absorption spectrum,effective mass model equation and Tauc's relation.It was found that the energy gap of the prepared samples decreases with increase in pH value.The recorded blue shift confirmed the quantum confinement effect in the prepared zinc oxide samples.Photoluminescence spectrum infers that the increase in pH value shifts the ultraviolet-visible emission but not the violet and green emissions.     

Ultrasonic synthesis of Zn-doped CdO nanostructures and their optoelectronic properties

The effect of Zn dopant on the growth of cadmium oxide (CdO) nanostructures through a sonochemical method was investigated. The X-ray diffraction (XRD) patterns of the nanoparticles show CdO cubic structures for the produced samples. Field emission scanning electron microscope (FESEM) images reveal that morphologies of the samples change, when they are doped with Zn atoms, and their sizes reduce. Room temperature photoluminescence (PL) and UV-Vis spectrometers were used to study optical properties of the samples. Evaluation of optical properties indicates that different emission bands result from different transitions and the value of CdO energy band gap increases due to doping. Studies of electrical properties of the nanostructures demonstrate that Zn dopant enhances electrical conductivity and photocurrent generation as the result of light illumination on the nanostructures due to improved density of photo-generated carriers. Considering the obtained outcomes, Zn dopant can alter the physical property of the CdO nanostructures.     

Crystallographic, optical and electrical properties of low zinc content cadmium zinc sulphide composite thin films for photovoltaic applications

In this paper a screen-printing method has been employed for the deposition of low zinc content cadmium zinc sulphide (Cd_0.9Zn_0.1S) composite thin films on ultra clean glass substrate. Cadmium sulphide, zinc sulphide and cadmium chloride have been used as the basic source material. With these basic source materials, the optimum conditions for preparing good quality screen-printed films have been found. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal) structure with strong preferential orientation of grains along the (1 0 1) direction. SEM/EDAX analysis confirms the formation of ternary compound. The optical band gap (E_g) of the films has been studied by using reflection spectra in wavelength range 350-600 nm. The DC conductivity of the films has been measured in vacuum by a two probe technique.     

Film characterization of titanium oxide films prepared by high-power impulse magnetron sputtering

Surface modification with a high power glow discharge is an emerging technology that can be used to improve the surface characteristics. Titanium oxide films are prepared using a high-power impulse magnetron sputtering (HPPS-M) glow discharge with a current density of 2 A/cm² and a power density of 1 kW/cm². Observing optical emission spectrum confirms that singly-ionized titanium ions are produced in the plasma. Ions are extracted from the HIPIMS glow plasma by a substrate placed near the plasma source. It is found that the substrate is immersed in the HPPS-M glow plasma. The film is deposited by a HPPS-M, and the results are compared to those of magnetron sputtering operated by a stationary dc power source. The deposition rate is lower by HPPS-M than that by DC-MS. The main structure of the films is rutile, however an anatase structure is also observed. The mixed structure is obtained at an oxygen rate as low as 5%. Anatase structure is not significantly observed in HPPS-M compared to that in DC-MS. The intensity of the XRD profiles becomes weaker with increasing the substrate position due to the collisions of metal species with the plasma species and the background gas particles. The deposition rate of the prepared titanium oxide film is significantly influenced by the production rate of titanium ions, distance of the substrate, and the gas mixture ratio. With regard to the effect of the gas ratio, the difference in the deposition rate is probably based on the argon ion density available to sputter titanium atoms that would eventually contribute to the titanium oxide film deposition.     

Diamond films by the excimer laser photoablation of polymers

The chemical vapor deposition of diamond films on silicon and various other substrates from a methane/hydrogen mixture, as well as from other gas compositions, uses plasma, a hot filament, or an acetylene torch to generate the reactive species. Although the attempt to produce diamond films from polymers is not new, crystalline diamond structures have yet to be obtained; only diamond-like carbon has been reported. The technique described here features the excimer laser ablation of polymers and the formation of crystalline diamond. A Raman peak at 1,330 cm^?1 clearly identifies diamond, but its shape also reveals the presence of graphite. Peaks at 1,350 ^?1 and 1,597 cm^?1 identify glassy carbon. Scanning electron microscopy micrographs reveal the crystalline structure. Cubic blocks are formed, as well as grains of about 1 μ size showing facets of all kinds reported for diamonds.     

Nanobeads of zinc oxide with rhodamine B dye as a sensitizer for dye sensitized solar cell application

Cost effective, ruthenium metal free rhodamine B dye has been chemically adsorbed on ZnO films consisting of nanobeads to serve as a photo anode in dye sensitized solar cells. These ZnO films were chemically synthesized at room temperature (27 °C) on to fluorine doped tin oxide (FTO) coated glass substrates followed by annealing at 200 °C. These films consisting of inter connected nanobeads (20-40 nm) which are due to the agglomeration of very small size particles (3-5 nm) leading to high surface area. The film shows wurtzite structure having high crystallinity with optical direct band gap of 3.3 eV. Optical absorbance measurements for rhodamine B dye covered ZnO film revealed the good coverage in the visible region (460-590 nm) of the solar spectrum. With poly-iodide liquid as an electrolyte, device exhibits photon to electric energy conversion efficiency (η) of 1.26% under AM 1.5G illumination at 100 mW/cm².     

湿法炼锌置换柱式净化装置传质过程(英文)

浸出液中铜、镉的净化是湿法炼锌中的重要步骤。提出一种置换柱式净化装置,并对其净化规律及传质系数进行实验研究。结果表明,净化效率随着锌粉粒径的减小及浸出液流速的减小而增大,若结构参数和操作参数使用恰当,净化率可达99%,但所使用的锌粉粒径必须大于0.45 mm。当流速范围为0.05~0.7 cm/s时,置换柱内传质系数kc为3.94×10-7~2.76×10-6 m/s,且kc随着锌粉粒径的减小及浸出液流速的增大而增大,满足传质准数方程:Sh=0.1069Re0.5Sc0.33(0.3相似文献   

Synthesis of cadmium oxide doped ZnO nanostructures using electrochemical deposition

Ternary ZnCdO alloy semiconductor nanostructures were grown using electrochemical deposition. Crystalline nanostructures/nanorods with cadmium concentration ranging from 4 to 16 at% in the initial solution were electrodeposited on tin doped indium oxide (ITO) conducting glass substrates at a constant cathodic potential −0.9 V and subsequently annealed in air at 300 °C. X-ray diffraction measurements showed that the nanostructures were of wurtzite structure and possessed a compressive stress along the c-axis direction. The elemental composition of nanostructures was confirmed by energy dispersive spectroscopy (EDS). ZnO nanostructures were found to be highly transparent and had an average transmittance of 85% in the visible range of the spectrum. After the incorporation of Cd content into ZnO the average transmittance decreased and the bandgap tuning was also achieved.     

Effect of ammonia solution on properties of sprayed ZnO thin films consisting of nano-pyramids

Hexagonal wurtzite zinc oxide (ZnO) thin films were deposited at substrate temperatures from 300 to 500 °C with surfactant of ammonia solution. The effect of ammonia on the structural, surface morphology, compositional, optical and electrical properties of ZnO thin films was studied. X-ray diffraction shows that the all films are polycrystalline in nature and have a hexagonal wurtzite structure with a high preferential orientation (002) plane for ammonia solution. High-resolution SEM studies reveal the formation of ZnO films consisting of nano-pyramids with uniformly distributed grains over the entire surface of the substrates. Photoluminescence studies indicate the presence of two emission peaks: (a) a sharp ultra-violet near band edge ～392 nm, (b) a sharp visible deep-level green emission peak ～564 nm. The optical properties show that the direct band gap energy values increase with increasing substrate temperatures.     

Recent progress in silicon molecular-beam epitaxy

Traditional concepts of epitaxial growth assume that for growth of a film with a finite thickness in finite time there is a temperature (T_epi) separating the regime of epitaxial, single-crystalline growth of the film from the regime of amorphous growth. Recent progress in the understanding of epitaxial growth shows that this concept is not applicable for silicon molecular-beam epitaxy. Instead, growth at a given temperature always proceeds epitaxially for a certain limiting thickness (h_epi) before the film becomes amorphous. Thus, a finite thickness can be grown at any temperature and, in particular, at temperatures low enough to suppress the surface segregation of dopants present at traditional growth temperatures. The growth of arbitrarily complex doping profiles by thermal, coevaporative doping becomes possible. Unity incorporation and activation of antimony with thermal, coevaporative doping up to dopant concentrations of ～10²¹ cm^?3 without any post-growth annealing have been achieved.     

One-pot synthesis of highly stable silver nanoparticles-conducting polymer nanocomposite and its catalytic application

Herein, we report the preparation of highly stable Ag_nano–PEDOT nanocomposite by one-pot fashion in acidic condition using 3,4-ethylenedioxythiophene (EDOT) as a reductant and polystyrene sulfonate (PSS^?) as a dopant for PEDOT as well as particle stabilizer for silver nanoparticles (AgNPs). The above nanocomposite denoted as Ag_nano–PEDOT/PSS^? nanocomposite. The formation of AgNPs with concomitant EDOT oxidation was followed by UV–visible (UV–vis) spectroscopy at different time intervals. Ag_nano–PEDOT/PSS^? nanocomposite shows absorption bands at 380 and above 700 nm, which correspond to surface plasmon resonance (SPR) peak of AgNPs and oxidized PEDOT, respectively. Ag_nano–PEDOT/PSS^? nanocomposite was characterized by infrared (IR) spectroscopy, transmission electron microscopy (TEM), and XRD. TEM study reveals that AgNPs are distributed uniformly around PEDOT polymer with an average particle size diameter of 10–15 nm. In addition, Ag_nano–PEDOT/PSS^? nanocomposite was tested for the catalytic reduction of 4-nitrophenol. For comparing stability, we were also synthesized AgNPs in the absence of PSS^? (denoted as Ag_nano–PEDOT) using EDOT as reductant. UV–vis spectrum of Ag_nano–PEDOT nanocomposite revealed that AgNPs prepared in the absence of PSS^? was not stable.