Synthesis,structural and optical characterization of Ni-doped ZnO nanoparticles

Nanocrystalline Zn_1−x Ni _x O (x = 0.00, 0.02, 0.04, 0.06, 0.08) powders were synthesized by a simple sol–gel autocombustion method using metal nitrates of zinc, nickel and glycine. Structural and optical properties of the Ni-doped ZnO samples annealed at 800 °C are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis using X-rays (EDAX), UV–visible spectroscopy and photoluminescence (PL). X-ray diffraction analysis reveals that the Ni-doped ZnO crystallizes in a hexagonal wurtzite structure and secondary phase (NiO) was observed with the sensitivity of XRD measurement with the increasing nickel concentration (x ≥ 0.04). The lattice constants of Ni-doped ZnO nanoparticles increase slightly when Ni²⁺ is doped into ZnO lattice. The optical absorption band edge of the nickel doped samples was observed above 387 nm (3.20 eV) along with well-defined absorbance peaks at around 439 (2.82 eV), 615(2.01 eV) and 655 nm (1.89 eV). PL measurements of Ni-doped samples illustrated the strong UV emission band at ~3.02 eV, weak blue emission bands at 2.82 and 2.75 eV, and a strong green emission band at 2.26 eV. The observed red shift in the band gap from UV–visible analysis and near band edge UV emission with Ni doping may be considered to be related to the incorporation of Ni ions into the Zn site of the ZnO lattice.     

Synthesis of well dispersed, regular shape ZnO nanorods: effect of pH, time and temperature

In this paper we presented a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution, reaction time and reaction temperature via cetyl trimethylammonium bromide-assisted hydrothermal method. The phase and structural analysis was carried out by X-ray diffraction, showed the formation of single phase ZnO with hexagonal wurtzite structure in all the specimens. Morphological and structural analysis was carried out by scanning electron microscopy and transmission electron microscopy showed that the shape of ZnO nanorods were greatly influenced by pH of precursor precipitate while size was affected by reaction time as well as temperature. The selected area diffraction pattern showed that the as synthesized ZnO nanorods were single crystalline in nature and preferentially grow along [0001] direction. A plausible growth mechanism of as prepared ZnO nanostructures was discussed in detail. Furthermore, the optical property of as prepared ZnO nanostructures was studied by photoluminescence spectroscopy.     

Synthesis and characterization of ZnO/SiO2 core/shell nanocomposites and hollow SiO2 nanostructures

In this paper, we prepared the ZnO nanoparticles by a simple hydrothermal method and fabricated the ZnO/SiO₂ core/shell nanostructures through a sol-gel chemistry process successfully. The hollow SiO₂ nanostructures were obtained by selective removal of the ZnO cores. The structure, morphology and composition of the products were determined by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicated that the ZnO nanoparticles were sphere-like shape with the average size of 60 nm and belonged to hexagonal wurtzite crystal structure. With the coating of SiO₂, the vibration modes of Si-O-Si and Si-OH were found. Furthermore, the measurement results of optical properties showed that spectra of bare ZnO nanoparticles and ZnO/SiO₂ core/shell nanocomposites exhibited similar emission features, including a blue emission peak and an orange emission band.     

Synthesis and characterization of ZnO with hexagonal dumbbell-like bipods microstructures

High crystalline ZnO with hexagonal dumbbell-like bipods morphology was successfully synthesized via N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-assisted hydrothermal microemulsion route. X-ray diffraction, scanning electron microscopy, photoluminescence spectrum and Ultraviolet and Visible absorption spectroscopy were used to characterize the structure, morphologies and properties of the as-prepared samples. The results demonstrated that the hydrothermal reaction time had obvious influence on the shape and size of the ZnO products. The Ultraviolet and Visible absorption spectra indicated that the as-prepared ZnO had a strong and broad absorption band from ultraviolet to visible region. The photoluminescence spectra of the synthesized ZnO exhibited a very strong UV emission at ～380 nm, indicative of their high crystal quality. Meanwhile, the possible growth mechanism for the formation of hexagonal dumbbell-like ZnO microstructures was proposed.     

Effect of ammonia water on the morphology of monoethanolamine-assisted sonochemicaly synthesized ZnO nanostructures

In the present work, ZnO nanostructures were synthesized by monoethanolamine (MEA)-assisted ultrasonic method at low temperature. Structural analysis was carried out by X-ray diffraction (XRD) confirmed the formation of hexagonal wurtzite structure of ZnO. The effect of ammonia water on the molecular structure of MEA, and its effect on the morphology of ZnO nanostructures were monitored by electron microscopy. Scanning electron microscopy (SEM) results suggest that ZnO nanoparticles with 100 nm in diameter were produced in case of MEA-assisted ultrasonic method. However, as ammonia water was added into the reaction system the morphology of ZnO nanoparticles changed into nanorods, flower-like nanostructures and finally microrods. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies showed that as prepared ZnO nanostructures were single crystalline in nature and grew in different directions resulted in the formation of various structures. The growth mechanism of as prepared ZnO nanostructures was discussed in detail. It was proposed that the addition of ammonia water into the reaction system resulted into the formation of ethylene diamine (EDA) which directed the growth of ZnO. The optical property was studied by photoluminescence (PL) spectroscopy showed only UV emission and no defects mediated visible emission.     

Synthesis, characterization and optical properties of sheet-like ZnO

Sheet-like ZnO with regular hexagon shape and uniform diameter has been successfully synthesized through a two-step method without any metal catalyst. First, the sheet-like ZnO precursor was synthesized in a weak alkaline carbamide environment with stirring in a constant temperature water-bath by the homogeneous precipitation method, then sheet-like ZnO was obtained by calcining at 600 °C for 2 h. The structures and optical properties of sheet-like ZnO have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and UV-vis-NIR spectrophotometer. The results reveal that the product is highly crystalline with hexagonal wurtzite phase and has appearance of hexagon at (0 0 0 1) plane. The HRTEM images confirm that the individual sheet-like ZnO is single crystal. The PL spectrum exhibits a narrow ultraviolet emission at 397 nm and a broad visible emission centering at 502 nm. The band gap of sheet-like ZnO is about 3.15 eV.     

The structural and optical properties of ZnO nanorods via citric acid-assisted annealing route

ZnO nanorods with diameters ranging from 25 to 88 nm and with length up to 1 μm were obtained via citric acid-assisted annealing route. The sample was characterized by X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), Raman spectrometer, FTIR spectrophotometer, ultraviolet visible (UV–VIS) spectroscopy, and photoluminescence (PL) spectroscopy. It demonstrates that the sample is composed of ZnO with hexagonal structure and the ZnO nanorods are of excellent optical quality.     

Structural,optical and magnetic characterization of Cu-doped ZnO nanoparticles synthesized using solid state reaction method

Polycrystalline undoped and Cu-doped Zinc oxide (Zn_0.98Cu_0.02O) nanocrystals were successfully synthesized by solid-state reaction method. The micro structural, optical and magnetic properties have been characterized using powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis using X-rays (EDAX), UV–Visible spectroscopy, Photoluminescence, Vibrating sample magnetometer and Electron paramagnetic resonance spectroscopy. XRD pattern reveals that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after copper doping. Optical absorption analysis of the samples showed a red shift in absorption band edge with copper doping in ZnO. Photoluminescence spectra of the samples shows prominent peaks corresponding to near band edge UV emission and defect related green emission in the visible region at room temperature and their possible mechanism have also been discussed. Magnetic measurements using VSM showed that the nanocrystalline copper doped ZnO exhibits ferromagnetic behaviour at 300 K. EPR analysis also confirms the substitution of Zn site by Cu²⁺.     

热处理温度对溶胶-凝胶法制备ZnO薄膜晶体结构和发光特性的影响

采用溶胶-凝胶(Sol-Gel)旋涂法在Si(100)衬底上制备ZnO薄膜,利用X射线衍射(XRD)、光致发光谱(PL)、扫描电子显微镜(SEM)等手段分析制得的ZnO薄膜的晶体结构和发光特性。着重考察了热分解温度对ZnO薄膜晶体结构和发光特性的影响。结果表明,溶胶-凝胶旋涂法制备的ZnO薄膜样品厚度约为220nm,属六方纤锌矿结构,其c轴取向度与热分解温度有很大关系;ZnO薄膜在室温下均有较强的紫外带边发射峰,且紫外带边发射峰与样品c轴取向度没有直接关系,与缺陷有关的可见发射带很弱。     

Rapid synthesis of ZnO ellipsoidal nanostructures in large scale and their photoluminescence properties

ZnO ellipsoidal nanostructures with uniform ellipsoidal morphologies have been synthesized using different hydroxide anion precursors by an ultra-fast, facile (90 °C) solution-phase method without the assistance of sonication or any surfactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements. Based on the experimental results, a growth mechanism of ZnO nanostructures was proposed. The obtained ZnO nanostructures exhibit a weak UV emission band at ~ 385 nm and a relatively stronger orange emission band at ~ 615 nm. The solution-phase method is simple, convenient for large-scale fabrication of ZnO ellipsoidal nanostructures.     

Visible light-activated cadmium-doped ZnO nanostructured photocatalyst for the treatment of methylene blue dye

An attempt was made to prepare Cd-doped ZnO photocatalyst for visible light assisted degradation of a textile dye (methylene blue, MB) in aqueous solutions by a traditional sol–gel process. The as-prepared nanoparticles were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, and photoluminescence spectra techniques. The results showed that the Cd-doped ZnO possess the single-phase hexagonal wurtzite structure. The photocatalytic activity of the nanoparticles under visible light was investigated by measuring the photodegradation of MB in aqueous dispersion. The effects of key operation parameters such as initial dye concentration, catalyst loading as well as initial pH value on the decolorization extents were investigated. The results indicate that the decolorization of the organic molecule followed a pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Under the optimum operation conditions, approximately 85.0% dye removal was achieved within 3.5 h.     

Visible photoluminescence of zinc oxide films electrochemically deposited on silicon substrates

Continuous crystalline films of zinc oxide (ZnO) with thicknesses of 6–10 μm were obtained by electrochemical deposition from aqueous zinc nitrate solutions on silicon substrates with a buffer nickel layer. X-ray diffraction measurements showed that the polycrystalline films possess a hexagonal crystal lattice with predominant (0002) orientation. The obtained ZnO films exhibit strong photoluminescence in the visible spectral range at room temperature.     

Rapid growth of nanotubes and nanorods of würtzite ZnO through microwave-irradiation of a metalorganic complex of zinc and a surfactant in solution

Large quantities of single-crystalline ZnO nanorods and nanotubes have been prepared by the microwave irradiation of a metalorganic complex of zinc, in the presence of a surfactant. The method is simple, fast, and inexpensive (as it uses a domestic microwave oven), and yields pure nanostructures of the hexagonal würtzite phase of ZnO in min, and requires no conventional templating. The ZnO nanotubes formed have a hollow core with inner diameter varying from 140–160 nm and a wall of thickness, 40–50 nm. The length of nanorods and nanotubes varies in the narrow range of 500–600 nm. These nanostructures have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The ZnO nanorods and nanotubes are found by SAED to be single-crystalline. The growth process of ZnO nanorods and nanotubes has been investigated by varying the surfactant concentration and microwave irradiation time. Based on the various results obtained, a tentative and plausible mechanism for the formation of ZnO nanostructures is proposed.     

Preparation and photoluminescence of ZnO with nanostructure by hollow-cathode discharge

Without the use of a metal catalyst in the process, ZnO with nanostructures was successfully prepared on Si (100) substrate by simple chemical vapor-deposition method. In our work, Ar was used as the plasma forming gas, O₂ was the reactive gas and metal zinc powder (99.99% purity) vaporized by cylinder hollow-cathode discharge (HCD) acted as the zinc source. The crystal structures of the as-synthesized ZnO nanostructures were characterized by X-ray diffraction (XRD); the ZnO sample growing on the wall of the crucible showed a ‘comb-like’ nanostructure, while the other one at the bottom of the crucible showed a ‘rod-like’ structure, which can be attributed to the difference of the oxygen content. The measurement on the photoluminescence (PL) performance of the ZnO nanostructures was carried out at room temperature. The results indicated that the ‘comb-shape’ ZnO nanomaterial possessed a remarkably strong ultraviolet emission peak centered at 388 nm, while ZnO nanorods, except better ultraviolet emission, also had relatively strong blue-green emission ranging from 470 to 600 nm due to the existence of oxygen vacancies. The growth mechanism of ZnO with nanostructures is also discussed in this paper.     

Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.     

ZnO nanoparticles: hydrothermal synthesis and 4-nitrophenol sensing property

In this paper reports a facile hydrothermal synthesis, characterization and sensing application of zinc oxide (ZnO) nanostructures. ZnO nanostructures were synthesized by mixing triethylamine (TEA) with zinc nitrate at 60?°C followed by calcination at 650?°C for 6 h. The detailed characterizations conformed the synthesized ZnO nanostructures. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Raman spectral analysis confirmed the formation of hexagonal ZnO. Band gap of the ZnO nanoparticles was determined by UV–visible absorption spectroscopy. Morphology and size of the sample was examined by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). It shows that the sample has rod and hexagonal morphology. Elemental composition was determined by energy dispersive X-ray (EDX) spectroscopy. The ZnO was coated on glassy carbon electrode (ZnO/GCE) and it was utilized as an electrochemical sensor for 4-nitrophenol (4-Np). Sensitivity and detection limit of ZnO/GCE towards 4-Np was found to be 0.04 µA/mM and 2.09?×?10^?5 M. The result suggests that ZnO has suitable sensor detection of 4-Np.     

Growth and optical and field emission properties of flower-like ZnO nanostructures with hexagonal crown

Flower-like zinc oxide (ZnO) nanostructures with hexagonal crown were synthesized on a Si substrate by direct thermal evaporation of zinc power at a low temperature of 600 °C and atmospheric pressure. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence were applied to study the structural characteristics and optical properties of the product. The result indicated that the flower-like product with many slender branches and hexagonal crowns at the ends were single-crystalline wurtzite structures and were preferentially oriented in the <001> direction. The photoluminescence spectrum demonstrated a strong UV emission band at about 386 nm and a green emission band at 516 nm. The field emission of the product showed a turn-on field of 3.0 V/µm at a current density of 0.1 μA/cm², while the emission current density reached about 1 mA/cm² at an applied field of 5.9 V/μm.     

Presence of intrinsic defects and transition from diamagnetic to ferromagnetic state in Co<Superscript>2+</Superscript> ions doped ZnO nanoparticles

In this paper, we report the structural, morphological and magnetic properties of pure and Co²⁺ doped ZnO nanoparticles synthesized using sol–gel auto combustion method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area diffraction pattern (SAED), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy. The analysis of XRD pattern shows the single phase nature with a hexagonal wurtzite structure for the prepared nanoparticles. The average crystallite sizes of the prepared nanoparticles were found in the range 18–19 nm. SEM images showed that pure and Co²⁺ doped nanoparticles have different morphology. The shape of the prepared nanoparticles is approximately hexagonal shown by TEM image. SAED pattern also confirms the wurtzite structure with single crystalline nature. FTIR spectra showed the characteristic vibrations frequency band of Zn–O. Photo luminescence spectrum showed that two emission peaks, which are ascribed to near band edge transitions and broadened intensive green emission associated with oxygen-vacancy defects. The magnetic properties were measured by vibrating sample magnetometer (VSM) and superconducting quantum interference device with field dependant magnetization at 300 K and temperature dependant magnetization from 0 to 300 K. From VSM analysis, pure ZnO nanoparticles show diamagnetic behavior while Co²⁺ doped ZnO nanoparticles revealed ferromagnetic behaviour at room temperature. The significant changes in M–H loop from diamagnetic behavior to ferromagnetic behavior are due to the intrinsic defects such as oxygen vacancies (Vo) and zinc vacancies (Vz_n). The RTFM has been presented in terms of vacancies in the frame of bound magnetic polaron model.     

Synthesis of violet light emitting single crystalline ZnO nanorods by using CTAB-assisted hydrothermal method

ZnO nanorods were grown by cetyl trimethylammonium bromide assisted hydrothermal technique from a single molecular precursor. The phase and structural analysis were carried out by X-ray diffraction technique and Raman spectroscopy, respectively. The phase and structural analysis has suggested that as prepared nanorods have hexagonal wurzite structure. Morphology of the nanorods was investigated by electron microscopy techniques which showed the formation of well dispersed nanorods of 100 ± 10 nm in diameter and 900 ± 100 nm in length. Optical properties were investigated by photoluminescence spectroscopy. As prepared ZnO nanorods have shown intense room temperature photoluminescence peak in the violet region at 403 nm. Absence of defect mediated green luminescence peak suggests the formation of well crystalline ZnO nanorods without any impurities or structural defects.     

Structural and optoelectronic characterization of prepared and Sb doped ZnO nanoparticles

This paper briefly reports the structural and optoelectronics properties of prepared pure and Sb doped ZnO nanoparticles. Doping with suitable elements offers an efficient method to control and enhance the optical properties of ZnO nanoparticles, which is essential for various optoelectronics applications. Sb doped ZnO nanoparticles have significant concern due to their unique and unusual electrical and optical properties. In the present work, we report the synthesis of Sb doped ZnO successfully with average particle size range from 26 to 29 nm via direct precipitation method. The phase purity and crystallite size of synthesized ZnO and Sb doped nano-sized particles were characterized and examined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The elemental analyses of undoped and doped ZnO nanoparticles were examined by using energy-dispersive X-ray spectroscopy (EDAX).We investigated and measured the optoelectronics properties of synthesized ZnO and Sb doped ZnO nanoparticles by employing photoluminescence and UV–Visible spectroscopy. The influence of Sb doping on photoluminescence (PL) spectra of ZnO nanoparticles, which consists of UV emission and broad visible emission band, is found to be strongly dependent upon the Sb concentration for all the Sb doped ZnO nanoparticles samples under investigation. The UV–Visible absorption study shows an increase in band gap energy as Sb is incorporated on the ZnO nanoparticles.