Annealed Zinc Oxide Research Articles

Sustainable synthesis of zinc oxide nanoparticles using Terminalia chebula extract: Effect of concentration and temperature on properties and antibacterial efficacy

Nanotechnology has revolutionized various fields, offering promising applications in medicine, catalysis, electronics and environmental remediation. One of the key challenges in nanoparticle synthesis is the development of environmentally friendly methods. A fruit extract of Terminalia chebula was used to make zinc oxide nanoparticles (ZnONPs), which were then annealed at temperatures ranging from 400 to 800 °C. The structural and optical properties of the annealed zinc oxide nanoparticles were investigated using different characterization techniques, such as FTIR, XRD, UV–visible spectroscopy, HR-TEM, SEM and EDX. The crystallinity, shape and size of the as-prepared ZnONPs showed a change when the annealing temperature was increased to 800 °C. A small red shift in the UV–vis absorption spectra was clearly observed with an increase in the annealing temperature. The antibacterial activity of the as-synthesised annealed ZnONPs was further tested against Salmonella enterica, Staphylococcus aureus and Escherichia coli. The antibacterial properties of the as-synthesised ZnONPs were synergistic. Formulation of ZnONPs at 400 and 600 °C showed the most effective antibacterial activity against gram negative strains.

Zinc Oxide Nanoparticles-Solution-Based Synthesis and Characterizations.

Zinc oxide (ZnO) nanoparticles have shown great potential because of their versatile and promising applications in different fields, including solar cells. Various methods of synthesizing ZnO materials have been reported. In this work, controlled synthesis of ZnO nanoparticles was achieved via a simple, cost-effective, and facile synthetic method. Using transmittance spectra and film thickness of ZnO, the optical band gap energies were calculated. For as-synthesized and annealed ZnO films, the bandgap energies were found to be 3.40 eV and 3.30 eV, respectively. The nature of the optical transition indicates that the material is a direct bandgap semiconductor. Spectroscopic ellipsometry (SE) analysis was used to extract dielectric functions where the onset of optical absorption of ZnO was observed at lower photon energy due to annealing of the nanoparticle film. Similarly, X-ray diffraction (XRD) and scanning electron microscopy (SEM) data revealed that the material is pure and crystalline in nature, with the average crystallite size of ~9 nm.

Measuring the Response of Annealed Zinc Oxide Thin Films to Ethanol Gas

Measuring the Response of Annealed Zinc Oxide Thin Films to Ethanol Gas

Effect of non-annealed and annealed ZnO on the optical properties of PVC/ZnO nanocomposite films

The goal of this study was to investigate the optical properties of the prepared polyvinyl chloride (PVC)/zinc oxide (ZnO) nanocomposite films. The PVC/ZnO nanocomposite films consist of the addition of different concentrations with both non-annealed ZnO nanoparticles and ZnO nanoparticles annealed at temperature of 700°C. The PVC/ZnO nanocomposite films by weight concentrations of (0 wt.%, 2.5 wt.%, 5 wt.% and 10 wt.%) have been prepared by the casting method. The optical absorbance and transmittance values of the composites films were measured in the wavelength range between (250 to 1100 nm) at room temperature by using the UV-1800 Shimadzu spectrophotometer. The optical properties (absorption coefficient, dielectric constant, refractive index, and optical conductivity) have been investigated by the ultraviolet (UV) spectrophotometer. The optical parameters (direct optical energy gap, excitation energy for electronic transitions, the dispersion energy, static refractive index, static dielectric constant, optical oscillator strengths, the moments of optical spectrum, linear optical susceptibility, third-order nonlinear optical susceptibility, nonlinear refractive index, high-frequency dielectric constant, the carrier concentration to the effective mass ratio, the long wavelength refractive index and the plasma frequency) were calculated. The results showed that the optical properties behavior of the PVC/ZnO nanocomposite films was found to be dependent on the ZnO concentration, and photon wavelength. In addition, the results of the study show that the optical parameters can be influenced by alter the concentration of the nonannealed and annealed a ZnO nanoparticle in the PVC polymer matrix.

Auto-combustion Fabrication and Optical Properties of Zinc Oxide Nanoparticles for Degradation of Reactive Red 195 and Methyl Orange Dyes

A new preparation method has been successfully utilized for the fabrication of zinc oxide nanoparticles using the auto-combustion technique and fuels (tartaric acid: TA, citric acid: CA and a mix between them) with molar ratio (Zn:TA; Zn:CA and Zn:CA:CA = 1:1:0, 1:0:0.55 and 1:0.5:0.275). The as-fabricated zinc oxide powder (ZTA, ZCA and ZCTA samples) annealed at 500 °C. The annealed zinc oxide powder was tested by different techniques like DRS, UV–Vis, FT-IR, HR-TEM and XRD. The Crystallite size of the annealed zinc oxide was estimated to be 24, 39 and 26 nm for ZTA, ZCA and ZCTA samples, respectively. The direct band gap, lattice parameters, unit cell volume (V), the dislocation density (D) and the Zn–O bond length (L) of the prepared zinc oxide powder (ZTA, ZCA and ZCTA samples) were determined. The synthesized zinc oxide nanoparticles are used as nanocatalyst for photodegradation of reactive red 195 and methyl orange as anionic dyes utilizing UV light irradiation. The degradation of reactive red 195 dye was 91–94% after 70 min over the synthesized zinc oxide and the values of degradation increased to be 99–99.8% in 50 min with H2O2 under UV light irradiation. Also, the degradation of methyl orange dye was 57.55–70.57% after 300 min over the synthesized zinc oxide (ZTA, ZCA and ZCTA samples) and the values of degradation increased to be 81–95% in 70 min with H2O2 under UV light irradiation. Finally, the appeared rate constant (Kapp) is determined and the mechanism of the photocatalysis process is suggested for the degradation of the dyes over the synthesized zinc oxide nanoparticles.

Ag/AgCl sensitized n-type ZnO and p-type PANI composite as an active layer for hybrid solar cell application

Acceptor annealed Zinc oxide (ZnO) based donor polyaniline (PANI) composite was synthesized via in-situ polymerization and sensitized with silver/silver chloride (Ag/AgCl) particles for enhancing the optoelectronic response. The sensitized composite is characterized, and the electron transfer mechanism is explained in detail. The absorbance wavelength enhanced for the sensitized composite is the result of a synergistic combination of annealing and sensitization. Elemental composition revealed the formation of sensitized composite inferred via energy dispersive spectroscopy (EDAX) using high-resolution transmission electron microscopy (HRTEM) and filed-emission scanning electron microscopy (FESEM). Selected area diffraction (SAED) pattern unveiled the coexistence of the amorphous and crystalline phase. The change in dipole moment and polarizability of molecules was evaluated using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, respectively. Current-voltage (I–V) characteristics proved annealing of ZnO and sensitization of polyaniline composite with annealed ZnO beneficial for current enhancement, which was further validated via cyclic voltammetry in the form of redox reaction current response.

Enhancement in structural, morphological and optical features of thermally annealed zinc oxide nanofilm

This paper presents the study of surface morphological, optical and microstructural features of zinc oxide (ZnO) nanofilm layered upon p-type Si substrate of <100> orientation by employing conventional RF magnetron sputtering system at different annealing temperatures. The effect of annealing on the nano-film is examined using different characterization techniques such as Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), FTIR (Fourier Transform Infrared Spectroscopy), UV-vis spectroscopy and Raman spectroscopy. The sharp diffraction peak at (002) orientation is seen by the XRD spectra which signifies a better growth of single crystalline thin film along the z-axis with the hexagonal wurtzite crystal structure. The surface morphological study shows that the grain size of the thin film intensifies from 22.06 nm to 36.77 nm when the annealing temperature is increased whereas there is a decrease in the values of lattice constants (a=b, c), FWHM (full width at half maximum), residual stress, lattice strain and dislocation density by increasing annealing temperature. The enhancement in the grain size makes the thin film appropriate for MEMS device applications including piezoelectric energy harvesters, gas sensors, etc. The optical bandgap of the ZnO thin film is estimated using Kubelka-Munk (KM) approach and it decreases from 3.23 to 3.16 eV for As-deposited, 400 °C, 600 °C and 800 °C respectively which makes the annealed thin film apposite for optoelectronic device applications. The intensity of the Raman peaks strengthens with the annealing temperature. These results prove that the annealing extensively enhances the crystallinity, structural, morphological and optical features of ZnO thin film and hence becomes suitable for nanoelectronic device applications.

EFFECT OF LOW-ENERGY OXYGEN ION BEAM TREATMENT ON THE STRUCTURAL AND PHYSICAL PROPERTIES OF ZnO THIN FILMS

In this paper, we report the influence of low-energy oxygen ion irradiation with fluence ranging from [Formula: see text][Formula: see text][Formula: see text] to [Formula: see text][Formula: see text][Formula: see text] on the structural, optical, and electrical properties of fresh and annealed (400∘C, 3[Formula: see text]h) zinc oxide (ZnO) thin films. These films were grown on soda-lime glass (SLG) substrates using the spin-coating method as a low-cost depositing technique. X-ray diffraction (XRD) study showed the formation of the hexagonal phase of ZnO thin films with preferred orientation along the (002) plane. The crystallite size for fresh and annealed ZnO thin films was in nanoscale and it increased with the annealing temperature. Also, the crystallite size increased with the ion beam irradiation fluence in the case of annealed ZnO films, while it slightly decreased for the fresh ZnO films. The transmittance and absorbance spectra for the ZnO films were investigated in a wide wavelength range. The optical bandgap was specified by using Tauc’s relation. The electrical properties of the ZnO films (fresh and annealed at 400∘C for 3[Formula: see text]h) were studied before and after the oxygen ion beam irradiation. Also, the dielectric properties were investigated with respect to frequency at different ion beam irradiation fluences. The comprehensive results showed the dielectric and optical properties are improved due to the induced conductive networks by oxygen ion irradiation.

Development of organic/inorganic PANI/ZnO 1D nanostructured hybrid thin film solar cell by soft chemical route

Polyaniline (PANI)/zinc oxide (ZnO) nanorods hybrid solar cell device was fabricated via a two-step process. The first step involved soft chemical synthesis of ZnO nanorods thin film on the indium-doped tin oxide (ITO) substrate and subsequent annealing in air at 300 °C. The second step of involved chemisorption of PANI on the surface of the ZnO nanorods by Doctor Blade Method. The fabricated heterojunction films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), fourier transform infrared (FT-IR), and Raman spectra. The results confirmed chemical interactions between PANI and ZnO and thus the formation of the heterojunction. Both the PANI coated pristine and annealed ZnO nanorods thin films were studied for their solar cell characteristics. The results of solar cell measurements showed that the overall light-conversion efficiency of PANI coated pristine ZnO thin film to be ~ 80% higher than for PANI coated annealed ZnO thin film. This is attributed to more effective charge separation and faster interfacial charge transferring occurred in the pristine ZnO thin films.

Enhancement of gas response of annealed ZnO film for hydrogen gas detection

&#x0D; &#x0D; &#x0D; &#x0D; The mechanism of hydrogen (H2) gas sensor in the range of 50-200 ppm of RF-sputtered annealed zinc oxide (ZnO) and without annealing was studied. The X-ray Diffraction( XRD) results showed that the Zn metal was completely converted to ZnO with a polycrystalline structure. The I–V characteristics of the device (PT/ZnO/Pt) measured at room temperature before and after annealing at 450 oC for4h, from which a linear relationship has been observed. The sensors had a maximum response to H2 at 350 oC for annealing ZnO and showed stable behavior for detecting H2 gases in the range of 50 to 200 ppm. The annealed film exhibited higher response than the film without annealing.. The sensing mechanism was modeled according to the oxygen–vacancy model.&#x0D; &#x0D; &#x0D; &#x0D;

Annealed zinc oxide films for controlling the alignment of liquid crystals

It is observed that the anchoring of LC molecules aligned on the ZnO film depends on the surface wettability. We demonstrate that the surface wettability of ZnO films fabricated by sol–gel process can be modified by annealing. The observations using the scanning electron microscope, photoluminescence and X-ray photoelectron spectroscopy for ZnO films have shown that the annealing can modify both the morphologies and chemical compositions of ZnO films, which in turn produces influences on the surface wettability. The surface wettability of as-prepared ZnO film can be controlled from 102° to 60° (contact angle (CA) of water) as the annealing temperature increases from 190 to 250 °C. Our experimental results show that the pretilt angles of LCs on ZnO films can be modified over a wide range from 89.5° to 0.5° as the CA of water on the ZnO films changes from 102° to 60°.

Zinc oxide based dye sensitized solar cell using eosin – Y as photosensitizer

A zinc oxide based Dye sensitized Solar Cell (DSSC) has been fabricated, using Eosin-Y as the dye adsorbed on a nanocrystalline zinc oxide - fluorine doped tin oxide electrode, for the sensitization of the large band gap semiconductor. The absorption spectrum of Eosin-Y showed high absorption of visible light between 450 and 600 nm wavelength. The SEM image of the annealed zinc oxide film revealed a uniform, porous and small round shaped grains. These are in favour of the solar energy conversion device. The short circuit photocurrent density (Jsc), the open circuit photovoltage (Voc) and the fill factor (FF) of the solar cell using Eosin-Y were obtained to be 7.243513 x 10 -2 mA/cm 2 , 4.325767 x 10 +2 mV and 3.769144 x 10 -1 . The efficiency of 1.2431 x 10 -2 % was achieved due to a high series resistance of 4.2175 x 10 2 Ohms cm -2 . Keywords: Dye sensitized, Eosin-Y, Absorption, Electrolyte, Photoanode, Zinc Oxide

Characterization of annealed zinc oxide nanotip array prepared by chemical bath deposition

We investigate the characteristics of thermally annealed ZnO nanotip in various ambient. AZO seed layer was first prepared on glass substrate by RF sputtering. A vertically oriented ZnO nanotip array was grown on AZO seed layer/glass by chemical bath deposition with precursors of zinc nitrate and ammonia at 70 °C. By thermal annealing in N2O ambient at 300 °C for 1 hour, the characteristics of ZnO nanotip array were improved and the ultraviolet sensor shows the best rise time of 50 s, decay time of 70 s and on/off current ratio of 26.04.

Low Temperature Annealed Zinc Oxide Nanostructured Thin Film-Based Transducers: Characterization for Sensing Applications.

The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH.

Luminance Behavior of Lithium-Doped ZnO Nanowires with &lt;I&gt;p&lt;/I&gt;-Type Conduction Characteristics

The present study describes the room-temperature cathodeluminescence (CL) and temperature-dependent photoluminescence (PL) properties of p-type lithium (Li)-doped zinc oxide (ZnO) nanowires (NWs) grown by hydrothermal doping and post-annealing processes. A ZnO thin film was used as a seed layer in NW growth. The emission wavelengths and intensities of undoped ZnO NWs and p-type Li-doped ZnO NWs were analyzed for comparison. CL and PL observations of post-annealed p-type Li-doped ZnO NWs clearly exhibited a dominant sharp band-edge emission. Finally, a n-type ZnO thin film/p-type annealed Li-doped ZnO NW homojunction diode was prepared to confirm the p-type conduction of annealed Li-doped ZnO NWs as well as the structural properties measured by transmission electron microscopy.

Structural and photoluminescence properties of Gd implanted ZnO single crystals

We present the structural and photoluminescence properties of 30 keV gadolinium implanted and subsequently annealed zinc oxide (ZnO) single crystals. Rutherford backscattering and channeling results reveal a low surface region defect density which was reduced further upon annealing. For low implantation fluence, around 85% of the Gd atoms are estimated to be in sites aligned with the ZnO lattice, while for higher fluences the Gd is largely disordered and likely forms precipitates. The Raman spectra of the implanted samples show defect-induced modes, which match the one-phonon density of states for the most heavily implanted samples. Annealing eliminates these features implying the removal of Gd-associated lattice disorder. Low temperature photoluminescence spectra revealed a red-shift in the defect emission, from green to orange/yellow, indicating the suppression of a deep level, which is thought to be due to oxygen vacancies. It is suggested that the orange/yellow emission is unmasked when the green emission is quenched by the presence of the implanted Gd atoms.

Nanocrystalline ZnO coated fiber optic sensor for ammonia gas detection

A cladding modified fiber optic sensor coated with nanocrystalline ZnO is proposed for ammonia gas detection. As-prepared and annealed zinc oxide (500 and 1200 °C) samples are used as the gas sensing media. The spectral characteristics of the fiber optic gas sensor are studied for various concentrations of ammonia (0–500 ppm). The sensor exhibits linear variation in the spectral peak intensity with the ammonia concentration. The characteristics of the sensor when exposed to ethanol and methanol gases are also studied for gas selectivity. The time response characteristics of the sensor are reported.

Growth of hierarchical based ZnO micro/nanostructured films and their tunable wettability behavior

Hierarchical zinc oxide (ZnO) micro/nanostructured thin films were grown onto as-prepared and different annealed ZnO seed layer films by a simple two step chemical process. A cost effective successive ionic layer adsorption and reaction (SILAR) method was employed to grow the seed layer films at optimal temperature (80 °C) and secondly, different hierarchical based ZnO structured thin films were deposited over the seed layered films by chemical bath deposition (CBD). The influence of seed layer on the structural, surface morphological, optical and wettability behavior of the ZnO thin films were systematically investigated. The XRD analysis confirms the high crystalline nature of both the seed layer and corresponding ZnO micro/nanostructured films with a perfect hexagonal structure oriented along (0 0 2) direction. The surface morphology revels a complex and orientated hierarchical based ZnO structured films with diverse shapes from plates to hexagonal rod-like crystal to tube-like structure and even much more complex needle-like shapes during secondary nucleation, by changing the seed layer conditions. The water contact angle (WCA) measurements on hierarchical ZnO structured films are completely examined to study its surface wettability behavior for its suitability in future self-cleaning application. Photoluminescence (PL) spectra of the ZnO structured film exhibit UV and visible emissions in the range of 420–500 nm. The present approach demonstrates its potential for low-temperature, large-scale, controlled synthesis of crystalline hierarchical ZnO nanostructures films.

Defects in a nitrogen‐implanted ZnO thin film

AbstractDefects in a nitrogen implanted and thermally annealed zinc oxide thin film (n‐type conducting) and reference samples were studied. Space charge regions realised by fabrication of semitransparent palladium Schottky contacts enabled the application of capacitance spectroscopic methods and photo ‐ current measurements. We report on the formation of a deep level, in the following labelled TN1. It is 580 meV below the conduction band edge, probably related to nitrogen, and must be distinguished from the well known intrinsic deep level E4 at almost equal energetical depth. Capacitance measurements in combination with optical excitation, conducted at different temperatures, as well as photo‐current measurements revealed the existence of two states approximately 60 meV and 100 meV above the valence band edge for the nitrogen implanted sample. These states cause an acceptor compensation degree larger than 0.9. The thermal emission of holes from these states into the valence band was observed by optical deep level transient spectroscopy.

X-ray peak broadening analysis in ZnO nanoparticles

Zinc oxide (ZnO) nanoparticles were synthesized by a hydrothermal process at 120 ∘C. XRD results reveal that the sample product is crystalline with a hexagonal wurtzite phase. TEM results confirm that the morphology of the annealed ZnO is rod shaped with an aspect ratio (length/diameter) of ∼3.2. We also investigate the crystallite development in nanostructured ZnO by X-ray peak broadening analysis. The individual contributions of small crystallite sizes and lattice strain to the peak broadening in as-prepared and annealed ZnO nanoparticles were studied using Williamson-Hall (W–H) analysis. All other relevant physical parameters including strain, stress and energy density value were calculated more precisely for all the reflection peaks of XRD corresponding to wurtzite hexagonal phase of ZnO lying in the range 20 ∘–65 ∘, from the modified form of W–H plot assuming the uniform deformation model (UDM), uniform stress deformation model (USDM) and uniform deformation energy density model (UDEDM). The root mean square (RMS) lattice strain 〈 ε R M S 〉 calculated from the interplanar spacing and the strain estimated from USDM and UDEDM are different due to consideration of anisotropic crystal nature. The results obtained show that the mean particle size of ZnO nanoparticles estimated from TEM analysis, Scherer’s formula and W–H method are highly inter-correlated. All the physical parameters from W–H plot are tabulated, compared, and found to match well with the value of bulk ZnO.