Zinc Oxide Samples Research Articles

Lu modified ZnO/CNTs composite: A promising photocatalyst for hydrogen evolution under visible light illumination

We report high photocatalytic hydrogen evolution from water-glycerol mixture under visible light illumination using sol–gel method synthesized zinc oxide (ZnO), Lutetium (Lu) modified ZnO and Lu modified ZnO/CNTs composite. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET), UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), photocurrent transient response and electrochemical impedance spectroscopy (EIS) Nyquist studies were used to determine the reason for improved photocatalytic hydrogen evolution. The highest hydrogen evolution rate of 380 µmolh−1 was obtained for Lu modified ZnO/CNTs composite, 3.11 times the amount generated over Lu modified ZnO and 10.5 times than using pure ZnO sample. This efficient enhancement in the photocatalytic hydrogen evolution was apparently attributed to the red shift in the optical absorption, increased charge separation, high surface area, cleavage of glycerol by Lu and synergistic effect between Lu and CNTs. Moreover, the effect of Lu and CNTs loading on the photocatalytic hydrogen evolution activity of Lu modified ZnO/CNTs was also studied under analogous experimental conditions. A mechanism of photocatalytic hydrogen evolution by Lu modified ZnO/CNTs composite was also proposed. Additionally, synthesized samples showed prolonged photostability with steady hydrogen evolution in successive cycle runs. This report might attract much attention to design highly efficient and inexpensive photocatalyst for hydrogen evolution under visible light illumination.

Synthesis and characterization of Sr-doped ZnO nanoparticles for photocatalytic applications

The use of semiconductors that respond to the visible light as a photocatalyst is an effective way to remove pollution resulting from the chemical industries. In this project, with the aim of increasing its photocatalytic activity, zinc oxide (ZnO) was doped with 1, 3, 5 and 7 M% strontium (Sr) by mechanical milling method. Characterization of the synthesized powders was done by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The optical behavior was evaluated using UV–Vis diffuse reflectance spectra (UV–Visible DRS) and photoluminescence. The XRD results showed successful doping of Sr in ZnO. The results of microscopic characterization revealed that the size of Sr-doped particles was in the range of 20–60 nm. Just about all results showed that the 3% Sr-doped ZnO sample (ZnO–Sr3) revealed the best performance. Its band gap decreased from 3.34 to 3.17 eV. Investigated by radiation of the HMI lamp for degradation of methylene blue (MB) dye, the photocatalytic efficiency of ZnO–Sr3 sample increased from 56 to 97%. Also, the results of chronoamperometry test showed a 3-fold increase in the photocurrent of ZnO–Sr3. Antibacterial studies of the samples on Escherichia coli (E. coli) bacterium also revealed that the ZnO–Sr3 sample had the highest antibacterial property.

Room temperature ferromagnetism in ZnS and ZnO nanoparticles

This article deals with the structural and optical properties of zinc oxide and zinc sulfide nanoparticles synthesized by chemical precipitation method. X-ray diffraction study confirmed the wurtzite structure of zinc oxide and the cubic structure of zinc sulfide. The average crystallite size, the lattice constant, and unit cell volume were calculated from the x-ray diffraction study. The ultraviolet-visible absorption spectra and the Tauc’s plot were confirmed the energy gap of zinc sulfide and zinc oxide samples to be 5.1 eV and 3.73 eV, respectively. Fourier Transformation Infrared spectra confirmed the formation of zinc oxide and zinc sulfide through the appearance of peaks between 618 cm−1- 439 cm−1. The photoluminescence spectra confirmed the violet emission from ZnO and UV from ZnS. The transmission electron microscope study also confirmed the existence of particles in nanometer size. Composition analysis confirmed the existence of zinc, sulfur, and oxygen. The vibrating sample magnetometer results depict that the zinc sulfide and zinc oxides are ferromagnetic at room temperature. Electron paramagnetic resonance spectra also confirmed the ferromagnetic nature of zinc sulfide and zinc oxide samples.

Effect of carbon-doping on structural and dielectric properties of zinc oxide

In this paper, Carbon-doped Zinc Oxide (C-ZnO) samples were prepared using the solid-state reaction method. The influence of carbon-doping on the structural and dielectric properties of ZnO samples was studied. The shift in the highest peak position (101) in XRD patterns of carbon-doped samples was observed. The Raman peak at 581[Formula: see text]cm[Formula: see text] in undoped ZnO was shifted and broadened in carbon-doped ZnO samples. The ZnO samples doped with carbon show higher values of dielectric constant ([Formula: see text] at 1[Formula: see text]kHz) compared to pure ZnO([Formula: see text] at 1[Formula: see text]kHz) which was due to increase in native point defects in the samples. The ac conductivity ([Formula: see text]) value of the carbon-doped sample was enhanced by 103 times for ((ZnO)[Formula: see text] [Formula: see text]) sample.

Structural and Dielectric Properties of Zn1-xMoxO Nanoparticles

Abstract: In this work, samples of zinc oxide nanoparticles doped by molybdenum (Zn1-xMoxO with 0 ≤ x ≤ 0.1) were prepared by using the wet co-precipitation method. The characterization of the prepared samples was carried out by means of X-ray powder diffraction (XRD). The samples reserved their hexagonal wurtzite structure with Mo doping and showed a decrease in the crystallite size up to x = 0.04 followed by a further increase. On the other hand, dielectric measurements were performed using an LCR meter. The effect of frequency and temperature on the dielectric properties such as the real and imaginary parts of dielectric constant (ε^' and ε'', respectively), dielectric loss (tanδ) and ac-conductivity (σ_ac) of Mo-doped zinc oxide samples, was studied in the frequency range (100 Hz - 1 MHz) and at temperatures (300 - 773 K). The values of room temperature dielectric parameters were found to be strongly dependent on the Mo-doping. However, the increase in temperature caused an enhancement in the values of the dielectric parameters, particularly at 773 K. Keywords: Zinc oxide, XRD, Dielectric constants, Ac-conductivity.

Effect of magnesium dopant on the structural, morphological and electrical properties of ZnO nanoparticles by sol–gel method

The undoped Zinc Oxide (ZnO) nanoparticles and Magnesium doped Zinc Oxide nanoparticles were produced by sol–gel method and the obtained nanoparticles were annealed at 400 °C. The effect of magnesium as dopant at various molar concentrations (Zn1-x Mgx O; x = 0, 0.2, 0.4) on the Structural, Optical, Morphological and Electrical properties were studied using X-ray diffraction (XRD), UV-Vis spectrophotometer, Photo luminescence, Field Emission Scanning Electron Microscope (FESEM) and Electron Impedance Spectroscopy. The XRD pattern confirms wurtzite structure without secondary phase in Mg substituted ZnO samples. Magnesium substitution decreases the crystallite size as the percentage of Magnesium is increased. Electrochemical impedance spectroscopy (EIS) was carried out to analyze the electrical properties of undoped ZnO and Magnesium doped Zinc Oxide nanoparticles.

Synthesis and characterization of zinc oxide nanostructures and its assessment on enhanced bacterial inhibition and photocatalytic degradation

In the present study, chemical reaction method is used to synthesis zinc oxide (ZnO) nanostructures concurrently doped with tin and fluorine and investigated for the enhanced bacterial inhibition and photocatalytic degradation. The optical, structural, compositional morphological, photocatalytic and antibacterial activities of ZnO nanostructures by the influence of doping were also studied. The exciton absorption of ZnO spectrum observed at 370 nm is being blue shifted to 364 nm in doped ZnO confirms the increase in incorporation of Sn and F. As the doping levels of F and Sn are increased, the size of the nanoparticles decreases. This can be observed in the transmission electron microscopic images and XRD results. ZnO is showing the presence of spherical nanoparticles whereas doped samples showing nanosheets structures. The surface morphology of the prepared samples was once again confirmed with SEM pictures. The time-dependent photo-catalytic activities of pure and doped samples of ZnO were studied separately under irradiation of UV–visible and visible light by degradation of methylene blue. The antimicrobial and photocatalytic activities of the prepared samples increased with the increasing doping level of Sn and F. Especially, the nanomaterial was noted with better antimicrobial activity against Staphylococus aureaus and Escherichia coli respectively. This study showed the tuning capabilities by doping level of tin and flourine in ZnO nanostructures.

GW electronic structure calculations of cobalt defects in ZnO

Recently the point defect responsible for the emission of cobalt in doped zinc oxide (ZnO) samples has been identified [24]. In this work we extend our investigation to other point defects in Co-doped ZnO. We use density-functional theory and GW calculations to obtain the orbital-resolved band structure of cobalt doped ZnO. We show that mainly O-p and Co-d orbitals take part in the process and confirm that an oxygen interstitial nearby a cobalt atom is a likely defect to occur in ion beam Co-doped ZnO samples. We also rule out that other common point defects in ZnO can be responsible for the observed d-d transition. Finally, we suggest that defect complexes involving oxygen interstitials could be used to promote ferromagnetism in cobalt doped ZnO samples.

Enhancement of ZnO Nanorods Properties Using Modified Chemical Bath Deposition Method: Effect of Precursor Concentration

In this study, the effects of different precursor concentrations on the growth and characteristics properties of the zinc oxide (ZnO) nanorods (NRs) synthesized by using modified and conventional chemical bath deposition (CBD) methods were investigated. The morphologic, structural and optical properties of synthesized ZnO NRs with different precursor concentrations were studied using various characterization techniques. The experimental results show that the varying precursor concentration of the reactants has a remarkable and significant effect on the growth and characteristics properties of ZnO NRs. In addition, the characteristic properties of ZnO NRs grown using the modified method showed significantly improved and enhanced properties. The average length of grown ZnO NRs increased with increased precursor concentration; it can be seen that longer ZnO NRs have been investigated using the modified CBD methods. The ZnO NRs synthesized at 0.05 M using the modified method were grown with high aspect ratios than the ZnO NRs grown using conventional means which were 25 and 11, respectively. The growth rate increased with increased precursor concentration; it can be observed that a higher growth rate was seen using the modification CBD method. Furthermore, XRD results for the two cases reveal that the grown ZnO samples were a nanorod-like in shape and possessed a hexagonal wurtzite structure with high crystal quality. No other phases from the impurity were observed. The diffraction peaks along (002) plane became higher, sharper and narrower as precursor concentration increased, suggesting that the crystalline quality of ZnO NRs grown using the modified method was more enhanced and better than conventional methods. However, optical studies show that the transmittance at each concentration was more than two times higher than the transmittance using the modified CBD method. In addition, optical studies demonstrated that the ZnO NRs grown by using modified and conventional methods had a direct Eg in the range of (3.2–3.26) eV and (3.15–3.19) eV, respectively. It was demonstrated in two methods that ZnO NRs grown at a precursor concentration 0.05 M gave the most favorable result, since the NRs had best characteristic properties.

Synthesize of gadolinium-doped ZnO nano particles for energy applications by enhance its optoelectronic properties

In recent research, the zinc oxide (ZnO) semiconductor nano particles have received a lot of attention due to its unique physical, chemical, magnetic and optoelectronic properties. The present study focuses on the photo physical and optoelectronic properties of ZnO nanostructures. To attain better optical and optoelectronic properties for light emitting diodes, solar cells and photo detectors, the rare earth transition metal ions, specifically gadolinium (Gd) were doped into ZnO nano material. Gadolinium-doped ZnO nano materials have been synthesized by a simple chemical deposition method. The structural, morphological, optical properties of synthesized samples have been investigated by various techniques, including x-ray diffraction (XRD), UV-absorption spectroscopy, and photo luminescence spectroscopy. X-ray diffraction analysis confirmed the formation of pure single phase with a particle size in the range of 30–42 nm. Optical absorption studies demonstrates that the absorption edge of the Gd:ZnO appeared to shift towards the longer wavelength due to the charge transfer between the ZnO valence or conduction band and rare earth ion 4f energy level. The band gap of the doped ZnO samples was found to be decreases and it varies from 3.2 eV to 3.1 eV due to the quantum confinement of the charge carriers in ZnO. These results provide a new approach to design ZnO nano particles with enhanced photochemical properties, light emitting electronics and solar cells.

Zinc Oxide Films with High Transparency and Crystallinity Prepared by a Low Temperature Spatial Atomic Layer Deposition Process.

Zinc oxide (ZnO) attracts much attention owing to its remarkable electrical and optical properties for applications in optoelectronics. In this study, ZnO thin films were prepared by spatial atomic layer deposition with diethylzinc and water as precursors. The substrate temperature was varied from 55 to 135 °C to investigate the effects on the optical, electrical, and structural properties of the films. All ZnO samples exhibit an average transmittance in visible and near-infrared light range exceeding 80% and a resistivity in the range of (3.2–9.0) × 10−3 Ω·cm when deposited on a borosilicate glass with a refractive index of ≈1.52. The transmittance, band gap, refractive index, and extinction coefficient are rarely affected, while the resistivity only slightly decreases with increasing temperature. This technique provides a wide process window for depositing ZnO thin films. The results revealed that the films deposited at a substrate of 55 °C were highly crystalline with a preferential (1 0 0) orientation. In addition, the grains grow larger as the substrate temperature increases. The electrical properties and reliability of ZnO/PET samples are also studied in this paper.

A comprehensive investigation on Ag-doped ZnO based photodiodes with nanofibers

The morphological, optical and electrical properties of undoped Zinc Oxide (ZnO) and 0.5% and 2% Ag-doped ZnO based Photodiodes were investigated. ZnO samples, which were deposited on p-type Si semiconductor substrates using spin a coating method, were produced by sol–gel method. The morphological properties of the ZnO films were investigated by atomic force microscopy. The results revealed that thin films are in nanofiber like structure that nanofiber spread homogeneously on the substrate. Additionally, the permittivity, absorbance, reflectivity and bandgap energy values were calculated by using the UV measurement results. The optic bandgaps of the films were also calculated by the optical absorption method. Each sample shows permittivity properties in the visible region; samples show absorption properties in the region where the applied wavelength is smaller than 400 nm. Reflecting boundaries were shift to higher boundaries with increased dopant effect. The transmittance of samples was found low in the UV region, but it shows higher characteristics which are between 78 and 88% in the visible region. To investigate the electrical properties of produced thin films, Current–Voltage, Capacitance–Voltage, Conductance–Voltage characteristics and Current–Time measurements were obtained in different illumination intensities. It was seen that the samples show photoconductive performance.

Physical and nuclear shielding properties of newly synthesized magnesium oxide and zinc oxide nanoparticles

Magnesium oxide (MgO) and Zinc oxide (ZnO) nanoparticles (NPs) have been successfully synthesized by solid–solid reaction method. The structural properties of ZnO and MgO NPs were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results indicated a formation of pure MgO and ZnO NPs. The mean diameter values of the agglomerated particles were around to be 70 and 50 nm for MgO and ZnO NPs, respectively using SEM analysis. Further, a wide-range of nuclear radiation shielding investigation for gamma-ray and fast neutrons have been studied for Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. FLUKA and Microshield codes have been employed for the determination of mass attenuation coefficients (μm) and transmission factors (TF) of Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. The calculated values for mass attenuation coefficients (μm) were utilized to determine other vital shielding properties against gamma-ray radiation. Moreover, the results showed that Zinc oxide (ZnO) nanoparticles with the lowest diameter value as 50 nm had a satisfactory capacity in nuclear radiation shielding.

ZnO modified by urea–hydrogen peroxide adduct as photocatalyst for 2-propanol photooxidation in the gas phase under different irradiations

Zinc oxide nanoparticles were synthesized via sol–gel process using zinc acetate dihydrate, ethanol and oxalic acid as precursor, solvent and complexing agent, respectively. Urea-hydrogen peroxide (UHP) and urea were added as modification agents. UHP played, simultaneously, the role of nitrogen precursor and oxygen donor. Structural, morphological, textural and optical properties of zinc oxide samples were studied using XRD, SEM, BET, UV–Vis–DRS and Raman techniques. The XRD patterns and Raman spectroscopy results showed that the products consisted of ZnO and revealed that nitrogen was doped in the lattice of ZnO. SEM images revealed the occurrence of agglomeration and aggregation of ZnO nanoparticles. The photocatalytic activity of ZnO samples was estimated based on the photooxidation of 2-propanol in gaseous phase under UV and solar irradiations. Under both UV and solar irradiations, ZnO doped with UHP showed higher photocatalytic activity in comparison with bare ZnO and ZnO doped with only urea. The results showed that increasing the crystallite size has a direct effect on the improvement of the photocatalytic activity of ZnO.

Effect of Benzalkonium Chloride on Properties of Zinc Oxide Nanoparticles Synthesized through Sol-Gel Technique

In the present study, to synthesize controllable sized metal oxide particles, benzalkonium chloride (BAK) as cationic surfactant was added to zinc oxide (ZnO) nanostructures synthesis at room temperature using sol–gel method. The effect of cationic surfactant BAK concentrations, on the optical properties, size, and morphology of ZnO nanoparticles synthesized through sol–gel method was studied. The characterization of ZnO nanostructures was occurred using transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet–visible near infrared (UV-Vis) spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). ZnO nanostructures shape and size were revealed by SEM and TEM. The hexagonal (wurtzite structure) of ZnO was confirmed by an X-ray diffractogram. The bandgap energy of the prepared ZnO samples was determined by UV-Vis spectrophotometer. FTIR analyzed the presence of functional groups.

Hierarchical porous Ga doped ZnO films synthesized by sol-electrophoretic deposition

In this study, Ga-doped zinc oxide (GZO) branched nanoparticles are synthesized by sol-electrophoretic deposition to investigate structural, morphological, size distribution, and optical properties evolution induced by Ga content. By selecting the optimum conditions in electrophoretic deposition (voltage = 10 V and time = 10 min) that provide the most uniform morphology, undoped zinc oxide (UZO) sample with hierarchical shape is obtained. For finding the optimum GZO sample for higher crystallinity and surface uniformity, different concentrations of Ga dopant are added to the system in predetermined voltage and time. Impurities increase the crystal energy and cause sizeable structure variation in formation of nanoparticles. This phenomenon causes Ga-doped samples in proper concentration have more fine particles rather than UZO. Ga dopant in a concentration of 1 mol% of Ga/Ga+Zn shows the most proper morphological and structural results. At this concentration, XRD peaks elucidate the highest crystallinity and a peak shift to higher angle due to appropriate Ga doping. HRXPS results show the efficient doping process at this chosen concentration of Ga. DRS spectra demonstrate a higher light trapping in the concentration of 1 mol% of Ga in comparison to UZO. Resistivity diagram shows Ga in concentration of 1 mol% have highest conductivity.

ZnO Nanosheets Exhibiting High UV Blocking Efficiency for Effective Application in Sunscreen

Zinc oxide (ZnO) nanopowder has been prepared by wet chemical method and tested for its effective UV blocking property coated on photosensitive paper/fabric samples. Zinc acetate dihydrate and ammonium hydroxide were adopted as synthesis precursors. Phase and crystallographic analysis of the samples have been carried out by X-ray diffraction (XRD) and show that ZnO sample belong to hexagonal wurtzite phase without any impurity. Surface morphology of ZnO samples studied by field emission scanning electron microscopy (FESEM) shows the formation of nanosheets with porous structure. These porous nanosheets have surface area varying from 5000-30000 nm2 with thickness 10-15 nm. ZnO nanosheets on the photosensitive paper show UV absorbance around 300 nm as observed from the absorption spectrum. The reflectance spectrum of ZnO also shows its effectiveness in reflecting UV light in the region of 350-400 nm. The sun protection factors (SPF) and ultraviolet protection factors (UPF) calculated from the above studies are also encouraging implicating the use of ZnO in sunscreen. The above experiment is carried out by preparing a photosensitive layer similar to human skin. Similar experiment has also been carried out by treating ZnO nanosheets on fabric samples and studying its effectiveness for protection from UV rays.

Transmission and Reflection Spectra of Zinc Oxide Implanted with a High Dose of Cobalt Ions

Optical transmission and reflection spectra of monocrystalline zinc oxide (ZnO) plates implanted with 40 keV Co+ ions to high doses of (0.5–1.5)·1017 cm–2 are presented. With increasing dose, the transmission value decreases and the optical transmission edge shifts towards the long-wavelength region in transmission spectra. Also, in the transmission spectra, three absorption bands are observed in the range of 550–680 nm. The bands and their positions are typical of optically active Co2+ ions in the zinc cation substitution positions in the ZnO matrix. The reflection coefficient of the implanted side of the ZnO plate increases monotonically with increasing dose values. In both the initial and implanted ZnO plates, when reflection spectra are recorded from the reverse (nonirradiated) side, a characteristic structure at l = 375 nm is observed due to exciton reflection. Modeling of light transmission and reflection in cobalt-implanted ZnO samples was carried out within the framework of a three-layer model, in which the first surface layer contains cobalt nanoinclusions, the second, deeper layer is a solid solution of cobalt ion substitution in the ZnO matrix, the third layer is the unirradiated part of the ZnO plate. Modeling was used to determine effective refractive indices of two ZnO layers containing implanted cobalt admixture in different phase states.

Temperature Effect of Chemical Bath Deposition (CBD) to Fabrication and Characterization of Zinc Oxide Nanorods Thin Films Based Gas Sensing: Ethanol

Fabrication of zinc oxide (ZnO) nanorods thin films based gas sensing ethanol have been done. Ethanol belongs to volatile organic compound (VOC) that are dangerous if inhaled by humans in high concentrations, so that its detection is necessary. Temperature as kinetic controller of chemical bath deposition (CBD) process take effect to ZnO fabrication and characterization. ZnO nanorods thin films was synthesized onto glass substrate by dip-coating technique. ZnO nanorods was grown using Zn(NO3)2.4H2O and HMTA with ratio 1:1 under CBD condition at temperature 75°C, 83°C, and 87°C. Result of SEM showing ZnO CBD 83°C has nanorods shape with diameter size is 95.56 nm, furthermore at 75°C the formation of the nanorods was not completed yet while at nanorods became deconstructed. XRD result showed all of ZnO sample have hexagonal wurzite which are match well with ICDS-094004 card. Ethanol gas sensing tested at 100°C, 150°C, 200°C showed high sensitivity of the sensor up to 77.31% for ZnO CBD 75°C at 100°C. ZnO CDB 83°C sample at test 200°C have highest response on 2.22 min (tres) and 0.45 min (trec). Time respond and recovery will increase along with increasing of test temperature.

Effect of Cationic Surfactants on Properties of Zinc Oxide Nanoparticles Synthesized through Sol-gel Technique

Zinc oxide (ZnO) is an important metal oxide which participates in lots of applications, including gas sensors, catalysis, and optoelectronic devices. For nanostructured materials, agglomeration is problematic in the chemical production processes. In surfactant-free chemical reactions, aggregation occurs immediately as particles are generated. Therefore, the synthesis of controllable size nanoparticles is of great fundamental and technological interest. In the present study, the effect of cationic surfactants such as cetyltrimethylammonium bromide and benzalkonium chloride concentrations, on the optical properties, size, and morphology of ZnO nanoparticles synthesized through sol-gel method were studied. The characterizing tools were X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible (UV-Vis-near-infrared) spectrophotometer. X-ray diffractogram confirmed the hexagonal (wurtzite structure) of ZnO. FTIR analyzed the presence of functional groups. The shape and size of the ZnO nanostructures were revealed by SEM and TEM. The band gap energy of the prepared ZnO samples was determined by UV-Vis spectrophotometer.