ZnO Lattice Research Articles

Electron promoted ZnO for catalytic synthesis of higher alcohols from syngas

Direct conversion of syngas from those non-petroleum carbon resources to higher alcohols are very attractive due to the process simplicity with low energy consumption. However, the reaction always suffers from low yield as well as low selectivity. Herein, effective increase of higher alcohols proportion in the product is realized by direct conversion of syngas over electronically-modulated ZnO semiconductor via Cu doping. It is considered that the lower Fermi level and narrower band gap of catalysts by embedding Cu2+ into ZnO lattice could facilitate donor reaction by boosting the process for the reactants to obtain electrons on the catalyst surface for the formation of CHx species and carbon chain growth, in which the Cu doping on ZnO lattice play important role in the promotion of CO adsorption. As a result, 4 mol% Cu doped ZnO exhibits a highest C2+OH/ROH fraction of 48.1%. Selectivity of catalysts from straight chain alcohol is better than from branch chain alcohol, which is different from promoted Cu/ZnO based catalyst. However, over-doping of Cu (7 mol%) on ZnO results in the aggregation Cu species on ZnO surface, leading to a sharp decrease of higher alcohols proportion to 3.2%. The results shed light on the nature that a direct correlation between semiconductor Fermi level and synthesis of higher alcohols, and the semiconductor-based catalysts mainly accelerate the hydrogenation reactions by enhancing thermally excited electron transfer.

Efficient photocatalytic degradation of organic dyes with Ag doped ZnO nanoparticles under UV light irradiation

Semiconductor based photocatalyst for degradation of cationic and anionic dye pollutants under UV light was demonstrated for wastewater treatment. In the present work, un-doped and Ag (mol% = 0, 0.05, 0.075 and 0.1)-doped ZnO nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD) pattern confirms that the samples are found to be of highly crystalline hexagonal wurtzite structure. Scanning electron microscopy (SEM) image reveals that the morphology of the doped ZnO nanoparticles are highly affected by the addition of silver (Ag). Fourier transform infra-red (FTIR) and energydispersive spectra (EDS) demonstrates the presence of Ag in the ZnO lattice. UV–Vis absorption spectra shows that the Agdoped ZnO nanoparticles exhibit a red-shift with reduced bandgap energy compared with un-doped ZnO nanoparticles. Hence, our aim is to find the effect of Ag- doping in ZnO nanoparticles for the improvement of photocatalytic degradation. The photocatalytic activities of these Ag-doped nanoparticles were evaluated by measuring the rate of photo-degradation reaction of hazardous methylene blue (MB) and methyl orange (MO) dye under UV-light irradiation. Photocatalytic efficiency in the degradation of MB and MO dyes was compared with the efficiency of un-doped ZnO. The effects of various factors like solution pH, photocatalytic dosage and UV irradiation time with concentration of MB and MO on photocatalytic degradation were studied. It was found that cationic dyes shows better photo-degradation than the anionic dyes. The main objective of the present work was optimizing the various factor for better photocatalytic activity, complete mineralization and evaluating the photocatalytic-degradation mechanism.

Efficient photocatalytic degradation of organic dyes with Ag doped ZnO nanoparticles under UV light irradiation

Semiconductor based photocatalyst for degradation of cationic and anionic dye pollutants under UV light was demonstrated for wastewater treatment. In the present work, un-doped and Ag (mol% = 0, 0.05, 0.075 and 0.1)-doped ZnO nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD) pattern confirms that the samples are found to be of highly crystalline hexagonal wurtzite structure. Scanning electron microscopy (SEM) image reveals that the morphology of the doped ZnO nanoparticles are highly affected by the addition of silver (Ag). Fourier transform infra-red (FTIR) and energy-dispersive spectra (EDS) demonstrates the presence of Ag in the ZnO lattice. UV–Vis absorption spectra shows that the Ag-doped ZnO nanoparticles exhibit a red-shift with reduced bandgap energy compared with un-doped ZnO nanoparticles. Hence, our aim is to find the effect of Ag- doping in ZnO nanoparticles for the improvement of photocatalytic degradation. The photocatalytic activities of these Ag-doped nanoparticles were evaluated by measuring the rate of photo-degradation reaction of hazardous methylene blue (MB) and methyl orange (MO) dye under UV-light irradiation. Photocatalytic efficiency in the degradation of MB and MO dyes was compared with the efficiency of un-doped ZnO. The effects of various factors like solution pH, photocatalytic dosage and UV irradiation time with concentration of MB and MO on photocatalytic degradation were studied. It was found that cationic dyes shows better photo-degradation than the anionic dyes. The main objective of the present work was optimizing the various factor for better photocatalytic activity, complete mineralization and evaluating the photocatalytic-degradation mechanism.

Enhanced photocatalytic and antifungal activity of ZnO–Cu2+and Ag@ZnO–Cu2+ materials

Zinc oxide is one of the most versatile nanostructured materials with a broad range of applications. Besides, its physicochemical properties can be tuned easily by synthesis conditions to be optimal for a specific application. In our group, we aim for the production of visible light-active materials with enhanced antimicrobial activity. Thus, we synthesize ZnO–Cu2+and Ag@ZnO–Cu2+ by using a fast and robust microwave solvothermal reaction. We investigate the limit of solubility of Cu2+into ZnO lattice producing Cu doped ZnO materials with different doping levels (1, 2, 3, 4, and 5 at. %, Cu/Zn). We also investigate the role of the copper precursor, using copper(II) acetate or copper(II) sulfate as model precursors. Copper acetate incorporates more efficiently into ZnO lattice by decreasing the Eg value of the doped materials at low doping levels. Furthermore, we study the composites Ag@ZnO–Cu2+ aiming to reduce doping levels and to improve antimicrobial activity. Characterization of the materials by different techniques demonstrates their uniform size, purity, crystallinity, and visible light activity. In this study, we evaluate airborne fungal contamination and demonstrate the capacity of ZnO–Cu2+ and Ag@ZnO–Cu2+ to inhibit fungal growth. We studied the microbiological quality of indoor air (vivarium) by sampling air under different conditions. By sampling air with a photocatalytic prototype, the amount of fungi in the air decreases considerably, particularly fungi that can enter the lung. In addition, ZnO–Cu2+ shows excellent antifungal activity against Candida sp at low doses. We use Atomic force microscopy (AFM) and holotomographic microscopy (HTM) to provide further evidence on the capacity of the prepared materials to achieve effective damage to fungal cells and to inhibit biofilm formation.

Relaxation of residual stress-controlled thermopower factor in transparent-flexible Ti-doped ZnO thin films

Transparent-flexible thermoelectric materials are attractive for future small-sized consumer electronics, the internet of things, and wearable devices. The microstructural evolution and subsequent thermoelectric properties of Ti 1%.at-doped ZnO thin films, grown on polyimide flexible substrates, are presented. The thin films were grown using radio frequency a magnetron sputtering method followed by annealing for 60 min at temperatures of 200–400 °C under vacuum atmosphere. Post-annealed films demonstrate a hexagonal Wurtize structure. It is found that the annealing helped to relax residual stresses in the thin films, subsequently leading to enhanced charge concentration, carrier mobility, mean free path, and density-of-states effective mass. The thin film, annealed at 300 °C, illustrates the highest power factor of the films measured at room temperature at 19.10 μW m−1 K−2. Further increases in the annealing temperature suggest Ti2+ diffuses into the ZnO lattice and in turn disturbs the crystalline structure; this results in a reduction of the power factor to 9.32 μW m−1 K−2 at an annealing temperature of 350 °C.

Structural and optical behavior of gallium and cobalt co-doped ZnO thin films fabricated by a sol-gel spin coating technique

In this study, the ZnO thin films with varying Ga/Co co-doping concentrations were produced on the quartz substrates by spin-coating technique. The structural and optical behavior of the films were analyzed by X-ray diffraction (XRD) and UV–Vis spectroscopy, respectively. XRD results reveal that all the films possess a hexagonal wurtzite structure of ZnO and have crystallite sizes in the range 8–24 nm. The prominent peaks (relative intensity greater than 10%) observed in the XRD profiles correspond to (100), (002), (101) and (103) planes, whereas the most preferred orientation of crystal growth in all the films is (002) plane. A small variation in the lattice constant values has been found owing to the inclusion of dopants and co-dopants in the ZnO lattice, as well as defects created in the crystal lattice at the time of film growth. Compared to the undoped ZnO film, the optical transmittance improves beyond the 430 nm wavelength upon 1 at% Ga doping, while in (1 at% Ga + 1 at% Co) and (3 at% Ga + 1 at% Co) co-doped films, it improves beyond the 600 nm wavelength. The UV–Vis spectroscopy results show the optical band gap value of 3.28 eV for the undoped ZnO film, which changes by a small amount in the doped and co-doped films.

Fabrication of zinc-aluminum layer double hydroxide thin films and their anionic adsorption performance

Layered double hydroxides (LDHs) are also known as hydrotalcite-like compounds or anionic clays. In this work, ZnAl-LDH films were prepared on aluminium (Al) plates by a hydrothermal technique using zinc nitrate solution as the precursors. ZnAl-LDHs films were characterized by SEM, EDX, XRD and FT-IR. The SEM analysis revealed that the ZnAl-LDH films with hierarchical nanoarchitectures on the surface of Al plates. EDX mapping and elemental analysis also showed that Zn, Al, and O dispersed uniformly on the aluminium substrates. XRD results were used to confirm the presence of ZnAl-LDH films as they appeared purely with the typical (003) and (006) peaks of LDH diffraction. The characteristic bands of bending vibrations due to the intercalating water, stretching vibration due to the overlapping signal of carbonate anion and nitrate anion were measured by FT-IR spectroscopy. The brucite structure also exhibited the OH-stretching vibration as well as the ZnO lattice vibration in the spectra. These ZnAl-LDH forms were evaluated for their removal performance against orange II dye solutions.

Ab initio calculations of electronic properties and charge transfer in Zn-=SUB=-1-x-=/SUB=-Cu-=SUB=-x-=/SUB=-O with wurtzite structure

The results of studying the electronic structure and the influence of the local environment of the copper impurity on the properties and magnetic moment in supercells in Zn1-xCuxO are presented. DFT calculations were carried out in the local electron density (LDA) and generalized gradient approximation (GGA). The band structure of in Zn1-xCuxO was calculated taking into account the correction for spin polarization and the strong electronic interaction. DFT LSDA + U and SGGA + U (U is the Coulomb interaction) calculations made it possible to take into account the contributions of the 3d shells of the Zn and Cu cations to the band spectrum of in Zn1-xCuxO. The introduction of copper into the ZnO lattice leads to a change in the impurity and valence bands of in Zn1-xCuxO. In this case, the bottom of the in Zn1-xCuxO conduction band shifts towards low energies. The total density of electronic states of in Zn1-xCuxO near the Fermi level is mainly determined by the 3d states of Zn and Cu and the 2p state of oxygen. ZnO doped with copper acquires a magnetic moment. The introduction of a vacancy into a supercell in Zn1-xCuxO noticeably changes the local magnetic moment. As the copper concentration in Zn1-xCuxO (x=0, 0.01, and 0.02) increases, the conductivity of the samples in both constant and alternating current increased, and the activation energy of conduction decreased. Keywords: ZnO, copper doping, density functional theory, band calculations, electronic structure, localized magnetic moment, defect formation energies, Zn1-xCuxO, charge transfer, parameters of localized states.

Vertically aligned Nd substituted ZnO nanorods: Morphology, optical characteristics and room temperature ferromagnetism

Zn1-xNdxO (x = 0.00, 0.01, 0.03, 0.05, 0.07) nanorods (NRs) are grown vertically, perpendicular to the glass substrate using a hydrothermal method. Nd3+ ions are successfully substituted into the crystal lattice of ZnO. The crystal structure, morphology, optical, and magnetic properties are comprehensively studied by various techniques. Significant changes are observed in the morphological and optical properties of the Nd substituted ZnO NRs. According to the magnetic measurements, the maximum Hc value is observed to be 39.04 Oe at a concentration of 3% Nd and the maximum Ms value is observed to be 20.52 x 10−6 emu at 7% Nd, whereas the maximum Mr value is measured as 1.86 x 10−6 emu at 5% Nd, confirming that the magnitude of magnetic parameters are independent of Nd concentration. An opposing correlation is found between the Hc value and the morphological properties (including crystallite size, average roughness, and aspect ratio) of Nd substituted ZnO NRs.

Dopant inculcated ZnO based photoelectrodes for revitalizing photoelectrochemical water splitting

In this present work, Sn and Al co-doped ZnO nanorods (NRs) were prepared for photoelectrochemical water splitting (PEC) application. Inspite of having a great deal of optoelectronic properties, the wide bandgap of ZnO semiconductor confines its photoelectrochemical performance supressing the charge separation efficiency. Modification of charge separation efficiency requires band engineering of the semiconductor. For bandgap modulation, introduction of dopants was found to be an effective method. X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) study revealed that the grown NRs showed a hexagonal wurtzite structure. The UV–Vis absorption spectroscopy manifested the enhancement of absorbance in the visible region with the introduction of dopants in ZnO lattice structure, while diminishing the bandgap from 3.26 eV to 2.87 eV for Sn0.05Al0.03Zn0.92O. Under visible light illumination (20 mW/cm2) the (Sn,Al) doped samples exhibited augmented photocurrent densities. The results of linear sweep voltammetry (LSV) showed that a photocurrent density of 1.87 mA/cm2 was achieved at 1.2 V vs Ag/AgCl for Sn0.05Al0.03Zn0.92O which is approximately 10 times intensified than that of ZnO NRs (0.18 mA/cm2). It also posess highest photoconversion efficiency (PCE) among all the doped samples due to its enhanced light absorption and rapid charge transfer property. Moreover, the Mott-Schottky (M-S) and Electrochemical Impedance Spectroscopy (EIS) assesments suggests that the n-type doped semiconductor had highest charge carrier density facilitated by huge separation of electron-hole pairs. The results obtained clearly gives an indication that the synthesised photocatalysts can meticulously act as an effective photoelectrode for an enhanced photoelectrochemical performance.

Analysis of the Nd dopant on optical, dielectric and biological properties of ZnO nanostructures

The effect of neodymium (Nd+3) on ZnO thin films has been studied with varying Nd doping percentage ranging from 1 to 5 wt%. XRD graphs confirmed that Nd ions have incorporated into the ZnO lattice without any structural modification. The increase of crystallite size was observed to vary from 27.5 to 31.90 nm with the increment in Nd amount. The optical spectra exhibited transparency in the visible region. The higher transmission was possessed at 1 wt at% Nd concentration. The band gap of Nd-doped ZnO thin films showed variation with the increase in Nd dopant concentration. The increment in dielectric constant and tangent loss was observed with the increase in Nd doping. The change in DC conductivity with frequency was measured by using Jonscher's power law while AC conductivity was explained with the hopping-barrier mechanism. The effects of Nd concentration on antibacterial efficiency against four different bacterial strains Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella Pneumonia (K. Pneumonia), and Staphylococcus aureus (S. aureus) were investigated whereas antifungal activity of Nd-ZnO was done against Aspergillus fumigate by using agar disc-diffusion method. ZnO with 4 wt % Nd demonstrated the best photo-catalytic property.

Influence of RE (Pr3+, Er3+, Nd3+) doping on structural, vibrational and enhanced persistent photocatalytic properties of ZnO nanostructures

Rare earth (RE- Pr, Er and Nd) doped ZnO nanostructures were prepared through simple wet chemical precipitation route. The RE doping induced interesting morphological transition from spherical to flower like structures were analyzed. The X-ray diffraction (XRD) measurements revealed that the prepared materials were of highly crystalline in nature and RE dopant ions did not altered the crystal structure of ZnO. The microstrain of ZnO was altered with respect to the nature of dopants. In the case of the Pr doped ZnO, X-ray photoelectron spectroscopy (XPS) analysis confirmed that the dopant (Pr) ions successfully substituted in the ZnO lattice. Raman spectra revealed RE doping induced lower energy side shift and variation in intensity of the peaks related to the characteristic phonon modes of ZnO. In the case of Nd doped ZnO nanostructures, dopant induced suppression in classical Raman modes and evolution of multiphonon related modes were identified. Optical diffuse reflectance spectral (DRS) measurements, along with the characteristic excitonic band of ZnO, other bands associated to the transitions of 4f energy levels related to the RE ions were observed. The partially filled 4f orbitals led to the enhanced photocatalytic activity in RE doped ZnO nanostructures. The observed enhanced photocatalytic activity in RE doped ZnO when compared to bare ZnO was discussed. The decolorization efficiency of MB ensued the following order 96 > 94 > 86 > 78% for ZnErO, ZnNdO, ZnPrO and ZnO, respectively.

The role of size-controlled CeO2 nanoparticles in enhancing the stability and photocatalytic performance of ZnO in natural sunlight exposure

In order to enhance the photocatalytic performance and stability, the various proportions of the size controlled cerium oxide (CeO2) nanoparticles were dispersed at the pre-synthesized ZnO. Although, the expected dual absorption onsets, probably due to the diminutive difference between the bandgaps of CeO2 (∼2.9 eV) and ZnO (∼3.1 eV), were not observed however, a blue shift in the bandgap energy of ZnO was witnessed with the increasing surface density of CeO2 particles. The delayed excitons recombination process with the increasing concentration of CeO2 nanoparticles was verified by the PL spectra. The structural investigation by Raman and XRD analysis revealed the surface attachment of CeO2 particles without altering the rock-salt lattice of ZnO. The morphological and fine microstructural analysis established the uniform distribution of evenly sized CeO2 particles at the surface of ZnO with the discrete fringe patterns of both the entities whereas the XPS analysis confirmed the majority of Ce4+ in dispersed CeO2. In comparison to pure ZnO, cyclic voltammetric (CV) analysis, under illumination, exposed the supportive role of surface residing CeO2 particles in eradicating the photo-corrosion of ZnO whereas the chronopotentiometry (CP) predicted the prolonged life-span of the excitons. Compared to pure ZnO, an appreciably high activity was revealed for 10% CeO2 loading as compared to pure ZnO for the removal of mono and di-nitrophenol derivatives and their mixtures under natural sunlight exposure. The variations in the removal rates in the mixture as compared to individual nitrophenol exposed the structure-based priority of ROS for the respective phenol. The significantly enhanced photocatalytic activity of the composite catalysts revealed the incremental role of surface-mounted CeO2 entities in boosting the generation of ROS under sunlight irradiation. The experimental observations were correlated and compiled to establish the mechanism of the removal process.

Theoretical and experimental study of effects of Co2+ doping on structural and electronic properties of ZnO

In this study, we theoretically investigated the electronic structure of Zn1-xCoxO using different approaches for the exchange-correlation potential comprising GGA with the on-site Coulomb correlation interaction U to the Zn d orbital (GGA + UZn), GGA with modified Becke–Johnson exchange potential (GGA + mBJ), and (GGA + mBJ + UZn). To support the theoretical results, a Co2+-doped ZnO sample was obtained experimentally by using the microwave–hydrothermal method. Changes in the structural, vibrational, electronic, and magnetic properties induced by the insertion of the Co2+ impurities in the ZnO lattice were determined based on first principles calculations. The theoretical results showed that the 3d orbitals derived from Co2+ appear in the deep region of the band gap. These orbitals are responsible for the magnetic behavior of cobalt doped materials. The energy levels introduced by the Co2+ dopant ions reduced the theoretical band gap value, which was also observed experimentally. The addition of Co2+ ions weakened the Raman mode E2H intensity, which was attributed to the increasing distortion induced by doping. Photoluminescence spectroscopy results indicated a reduction in the visible emission region after adding Co2+ ions, thereby indicating the formation of alternative pathways for the recombination process.

Electrical properties of ZnO films implanted with rare earth and their relationship with structural and optical parameters

ZnO implanted with Rare Earth (RE) ions has a potential application as phosphor or in white light sources. The paper discusses the structural, optical and electrical changes caused by Yb, Dy and Pr ions implanted into thin ZnO films grown by Atomic Layer Deposition (ALD). Using channeling Rutherford Backscattering Spectrometry (RBS/c), room temperature photoluminescence (RT PL) technique and Hall effect measurements, it has been shown that the initial damages of the ZnO crystal lattice caused by the rare earth (RE) ion implantation can to a certain extent be removed via post-implantation thermal treatment, provided the fluence is lower than 1.5 × 1015 at.cm−2.A comparison of the structural optical and electrical properties of annealed ALD–ZnO:RE layers with the results of analogous studies performed on thermally untreated RE-implanted films allows us to conclude that properly selected annealing steps allow for a substantial improvement in the conductivity of the layers as well as the intensity of luminescence, which can be attributed to the appearing recrystallization phenomena in the ZnO lattice.

Tuning of Photoluminescence and Antibacterial Properties of ZnO Nanoparticles through Sr Doping for Biomedical Applications

Sr-doped ZnO nanoparticles have been synthesized using a soft chemical method. The doping ratio of Sr is varied in the range of 0 at.%, 3 at.%, and 5 at.% to 7 at.%. X-ray diffractograms revealed that the samples had hexagonal (wurtzite) structure without a trace of any mixed phase. The average crystallite size of the nanoparticles (NPs) ranged from 39 to 46 nm. The average crystallite size was increased for the initial doping (3 at.%) of Sr ions, and further increase in the doping ratio reduced the particle size due to some distortion produced in the lattice. The surface morphology of the samples and structure of the NPs were investigated using FESEM (Field Emission Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) pictures, respectively. EDX (energy-dispersive X-ray) spectroscopy confirmed the presence of strontium (Sr) in the host lattice. Photoluminescence and X-ray diffraction confirmed that the dopant ions replace some of the lattice zinc ions and that Sr2+ and Sr3+ ions coexist in the ZnO lattice. The Sr-doped ZnO exhibited violet and blue luminescence spectra at 408 nm and 492 nm, respectively. ZnO : Sr nanoparticles showed increased antibacterial activity against one gram-positive as well as one gram-negative bacteria.

Multifractal analysis of Mg-doped ZnO thin films deposited by sol-gel spin coating method.

A multifractal analysis has been performed on the 3D (three-dimensional) surface microtexture of magnesium-doped zinc oxide (ZnO:Mg) thin films with doping concentration of 0, 2, 4, and 5%. Thin films were deposited onto the glass substrates via the sol-gel spin coating method. The effect of magnesium doping, on the crystal structure, morphology, and band gap for ZnO:Mg thin films has been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis spectroscopy. It has been observed that the surface of ZnO thin films is multifractal in nature. However, multifractality and complexity observed to decrease with increasing content of Mg in ZnO thin films due to formation of islands on the surface in accordance with Volmer-Weber growth mechanism. The investigations revealed that crystallinity, microtexture, morphology, and optical properties of the thin films can be tuned by controlling the Mg content within the ZnO lattice. In particular, their optical band gap energies were 3.27, 3.31, 3.34, and 3.33 eV at 0, 2, 4, and 5%, respectively. The prepared thin films of ZnO:Mg with tuned characteristics would have promising applications in optoelectronic devices.

Study of structural, morphological and optical properties of ZnO and Mg-doped ZnO thin films synthesized by evaporation technique

Un-doped ZnO and Mg-doped ZnO thin films (TFs) are synthesized by evaporation technique. The synthesized un-doped ZnO TFs are exposed to evaporated Mg contents for different times. XRD patterns reveal the development of (100), (002), (101) planes related to ZnO phase. The shifting of diffraction planes and shrinking of lattice parameters confirms the doping of Mg contents into ZnO lattice. The crystallite size of (100), (101) and (002) planes lies in the range from (12.43-14.51 nm), (14.28-19.08 nm) and (14.78- 19.19 nm) respectively. SEM analysis indicates that the formation of nano-fibers and nano-chains of rounded nanoparticles. EDX analysis confirms the presence of Zn, O and Mg whose amount is increased with increasing exposure time. The energy band gap (Eg) of un-doped ZnO (⁓ 3.05 eV) is increased to  3.08,  3.19 and  3.29 eV) with increasing exposure time in Mg contents.

The role of Co in doping ZnO nano-particles in enhancement the structural, optical and magnetic properties for spintronics

Zn1−xCoxO (0 ≤ x ≤ 0.10) nano-particles were fabricated successfully via ball milling procedure. The influence of [Co]/[Zn] on the properties of nano-particles was examined employing X-ray diffraction, the energy dispersion of the X-ray (EDX), Scan Electron Microscope (SEM), these measurements exhibit the growth hexagonal wurtzite crystal phase Zn1−xCoxO nano-particles with the successfully incorporation of Co+2 ions in the ZnO lattice. The optical characterization investigated utilizing Ultraviolet-Visible (UV) absorption spectroscopy for Zn1−xCoxO nano-particles refers to a red-shift in the optical bandgap with increasing Co ion inside ZnO matrix, this result confirm the bandgap is considerably narrowed with increasing Co ratio. The measurements of magnetization applying vibrating sample magnetometer illustrated a hysteresis loop in Co-doped ZnO nano-particles. Thanks to the variation values of bandgap Eg opt and magnetic measurements of ZnO nano-particles doped Co% plays a major role for selective coatings of optoelectronics; use as antireflective coating materials, and fabrication of optoelectronic devices.

A comparative study of different rare-earth (Gd, Nd, and Sm) metals doped ZnO thin films and its room temperature ammonia gas sensor activity: Synthesis, characterization, and investigation on the impact of dopant

Zinc oxide and rare earth (Gd, Nd, and Sm) doped zinc oxide thin film has been synthesized chemically by facile and cost-effective SILAR method. The impact of rare-earth doping on structural, morphological, and optical properties of ZnO films has been investigated using various characterization techniques. The stylus profiler method is employed to find the thickness of the films. The doping of rare earth elements reduces the thickness of the films. The XRD and SEM results suggest that the rare-earth metal is successfully incorporated into the ZnO lattice. The elemental mapping and EDS results show that homogeneous scatter of zinc (Zn), oxygen (O), gadolinium (Gd), neodymium (Nd), and samarium (Sm) compounds are found in the doped films. The transmission and bandgap of the films are enhanced due to doping. The doped ZnO films have exhibited significant enhancement in ammonia gas sensors at room temperature. Nd doping is effective than the Sm doped ZnO and Gd doped ZnO to sense the ammonia in terms of recovery time, response time, and sensitivity.