Doped ZnO Nanopowders Research Articles

Eco-friendly green synthesis of (Cu, Ce) dual-doped ZnO nanoparticles with Colocasia esculenta plant extract using microwave assisted technique for antioxidant and antibacterial activity

In the realm of biomedical applications, the inclusion of plant-derived components stands out as a critical consideration due to their non-toxic nature and antioxidant properties. In our research, we opt for Colocasia esculenta plant extract, utilizing microwave technology to create dually doped ZnO nanopowder with copper (Cu) and cerium (Ce). Authors employ XRD analysis to explore the structural attributes and crystallite size of the nanoparticles, which are found to be within the range of 16–19 nm. The surface and internal characteristics of these nanoparticles are precisely scrutinized using SEM-EDS and TEM characterization techniques. Additionally, ultraviolet-visible spectroscopy is utilized to determine the forbidden energy gap of the samples, providing insights into their potential applications in UV-protected devices. The synthesized nanoparticles exhibit significant antibacterial and antioxidant properties, highlighting their adaptability for various biomedical uses.

Effect of Bi doping on the opto-electronic properties of ZnO nanoparticles for photodetector applications

Bi (0, 1, 3 and 5 wt%) doped ZnO nanopowders were generated in this study using a simple and inexpensive wet chemical method. X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy, photoluminescence spectroscopy, UV–Vis-DRS, studies are used to evaluate the effect of dopants in ZnO sample. Crystallite size and grain size of the samples were reduced and enhanced the surface to volume ratio due to Bi doping. Oxygen vacancies and shrinkage of bandgap plays a significant role in enhancement of photosensing property. Bi doped ZnO nanopowders had better photosensing activity than pristine ZnO nanopowders. Also, the doped metal ions improved the photosensing efficiency by increasing electromagnetic wave absorption and inhibiting the recombination rates of charge carriers resulting raise of hole-electron pair production. The significant photosensing parameters responsivity (R), detectivity (D*) and external quantum efficiency (EQE) of the 3 % of Bi doped ZnO sample exhibited maximum values such as 0.163 AW−1, 1.26 × 1010 Jones and 53% respectively. The findings of this present study show that the3 % Bi doped ZnO can be an excellent photosensing material.

Effect of Thermal Treatment on the Structure and Morphology of Vanadium Doped ZnO Nanostructures Obtained by Microwave Assisted Sol-Gel Method.

In this paper, we conducted a fundamental study concerning the effect of thermal treatment on the structure and morphology of 2 mol% vanadium doped ZnO nanopowders obtained by microwave assisted sol-gel method (MW). The samples were analyzed by DTA, FTIR, XRD, SEM, and UV-Vis spectroscopy. The DTA results showed that above 500 °C, there was no mass loss in the TG curves, and ZnO crystallization occurred. The XRD patterns of the thermally treated powders at 500 °C and 650 °C showed the crystallization of ZnO (zincite) belonging to the wurtzite-type structure. It was found that in the 650 °C thermally treated powder, aside from ZnO, traces of Zn3(VO4)2 existed. FTIR spectra of the annealed samples confirmed the formation of the ZnO crystalline phase and V-O bands. The micrographs revealed that the temperature influenced the morphology. The increase in the annealing temperature led to the grain growth. The SEM images of the MW powder thermally treated at 650 °C showed two types of grains: hexagonal grains and cylindrical nanorods. UV-Vis spectra showed that the absorption band also increased with the increasing temperature of thermal treatment. The MW sample annealed at 650 °C had the highest absorption in ultraviolet domain.

Photovoltaic performance and physical characterization of Cu doped ZnO nanopowders as photoanode for DSSC

In this study, the effects of two fabrication factors, the Cu doping and the dye adsorption time on the ZnO-DSSC, were systematically investigated. ZnO nanostructures were obtained by hydrothermal synthesis method at different Cu doping ratio (0%, 0.1%, 1%, 3%) and used as photoanode in DSSC. The effects of Cu incorporation to ZnO on the morphological, structural, and optical properties were examined. As a result of XRD analysis, it was determined that all samples have highly crystallized hexagonal wurtzite structure. The doping process has caused the formation of protruding surfaces in the ZnO nanostructure and increased the surface area, which has been observed using SEM images. X-ray photoelectron spectroscopy (XPS) study demonstrated Cu-O and Zn-O bonding in the synthesized flake-shaped Cu doped ZnO nanostructures, which confirmed the Zn substitution by the Cu-ions. The maximum cell efficiency of 2.03% was achieved in DSSC when photoanode was fabricated by using %0.1 Cu doped ZnO nanopowder dipped in N719 solution for only one hour. The efficiency of DSSC with Cu doped ZnO photoanode has improved by 20%, and the dye adsorption time has been decreased by three times, obviously.

Combustion synthesis, characterization and antibacterial properties of pristine ZnO and Ga doped ZnO nanoparticles

Herein, undoped and Ga doped ZnO nanoparticles were prepared using a combustion method. The effect of Ga doping on the structural, optical, surface morphological and antibacterial properties was explored. The hexagonal wurtzite structure and the preferential (101) plane orientation were confirmed by powder X-ray diffraction (PXRD) studies. The Raman active modes of ZnO phase were found using Raman spectral analysis. The occurrence of the functional groups and chemical bonding was affirmed by FTIR spectra. HRSEM images revealed that the spherical shaped particles are agglomerated and contained several voids. The antibacterial efficacy of the prepared nanoparticles was examined against different bacteria viz. Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. From this analysis, it is found that the undoped and Ga doped ZnO nanopowders remarkably enhances the antibacterial activity.

Synthesis and comparative study on the structural and optical properties of ZnO doped with Ni and Ag nanopowders fabricated by sol gel technique

In this work we have tried to prepare Ni and Ag doped ZnO nanopowders using the sol gel technique. The influence of Ni and Ag (1, 3 and 5 mol.%) on the crystalline structure and optical properties of ZnO was investigated. The samples were characterized by XRD, FTIR and UV–visible spectrophotometer. XRD patterns confirmed the wurtzite formation of doped and undoped ZnO nanopowders. The average crystallite sizes of the prepared samples found from XRD were 19 nm for undoped ZnO, from 17 to 22 nm for Ni-ZnO and from 19 to 26 nm for Ag-ZnO. The average crystallite size of Ag-ZnO increased with increasing Ag contents. Different optical properties of Ni-ZnO and Ag-ZnO nanopowders were observed for different Ni and Ag content. The band gaps of Ni-ZnO and Ag-ZnO nanopowders were lower than that of the undoped ZnO (3.1 eV). The band gaps of Ag-ZnO were lower than that of Ni-ZnO. The optical properties of ZnO were enhanced by Ni (mol.%) in the UV region and by Ag (3 and 5 mol.%) in the visible region.

Antibacterial and Optical Properties of Mn Doped ZnO Nanopowders Synthesized via Spray Drying and Subsequent Thermal Decomposition

Mn doped ZnO nanopowders with homogenous particle distribution were synthesized using spray drying and thermal decomposition dual methods. Synthesis was carried out in spray drying slurry containing zinc acetate powders followed by calcining the as-prepared powders at 300, 400, and 500oC. Mn doping was achieved by adding manganese (II) acetate at different concentrations between 0.01-0.05 M during the synthesis. The obtained powders were characterized by a variety of characterization techniques. The results of phase analysis revealed that Mn-doped ZnO nanopowders having a single hexagonal structured ZnO phase. According to the results of microstructural and UV-vis characterizations; morphologies and optical properties of the Mn-doped ZnO nanopowders were affected by Mn doping. Furthermore, the results of this study exhibited that the addition of Mn have a significant influence on the antibacterial performance of the synthesized ZnO nanopowders.

Structural and optical characteristics of pure and 5%RE (Tb, Y and Eu) doped ZnO

In the present work, RE doped ZnO nano-powder has been successfully prepared by solid-state reaction. The products were obtained by doping commercial ZnO with 5% of three different rare earth elements; Europium Eu, Terbium Tb and Yttrium Y. The investigation results showed that the prepared materials exhibit predominant hexagonal wurtzite structure and have grain size between 20–65 nm. The band gap of the doped samples decreased from 3.212 to 3.137 eV; whereas, the optical absorption increased from 35% to 70%. The photoluminescence investigation showed that ZnO samples exhibit violet, blue and green emission that red shifts upon increasing structural distortion. Overall, the findings demonstrated the possibility of controlling ZnO visible light emission and control it to emit at a desired region that is beneficial for light emitting diodes and screen displays.

Peculiarities of photoluminescence in gas ambient of doped ZnO nanopowders

Investigation of the peculiarities of photoluminescence in different gas ambients of Si- and Ge-doped ZnO nanopowders was carried out. Nanopowders were obtained and doped by means of pulsed laser reactive technology. X-ray diffractometry, scanning, and transmission electron microscopy were conducted to determine the structure, shape, and size of the nanoparticles. Changing the gas environment leads to a significant change in the intensity of the photoluminescence spectra and its deformation; this is a result of the redistribution of existing luminescence centers and the emergence of additional luminescence centers caused by the adsorption on the nanopowders surface. The decomposition of luminescence spectra into elementary bands shows the presence of four elementary peaks at 430, 480, 515, and 555 nm. The influence of the impurity and the gas medium on the redistribution of elementary luminescence band intensities was investigated. The investigated nanopowders can be effectively used as sensitive materials for the construction of gas sensor systems.

Electrical conductivity improvement of Fe doped ZnO nanopowders

The chemical co-precipitation process was used for the synthesis of Fe-doped ZnO nanopowders (ZnO:Fe) with varying doping concentrations from 0% to 10 %. Doping with iron caused significant alterations in the physical properties of ZnO nanopowders. The XRD analysis revealed that Fe introduction forms a secondary phase of spinel ZnFe2O4 for doping concentration higher than 1%. The average crystallite size was proven to decrease with the increase in Fe concentration. SEM images showed the formation of spherical nanoparticles, where the average grain size decreased with doping. The Fe incorporation into the ZnO host lattice was also confirmed by FTIR and Raman spectroscopy. The optical properties were strongly influenced by Fe doping. The dielectric parameters were subsequently investigated as a function of frequency and composition. The observed dielectric dispersion was interpreted on the basis of Maxwell-Wagner interfacial model and Koops phenomenological theory. Overall, Fe doping improved the electrical conductivity of ZnO nanopowders.

Li doped ZnO based DSSC: Characterization and preparation of nanopowders and electrical performance of its DSSC

Abstract In this study, microwave-assisted hydrothermal method (MW-HT) has been used to synthesize the nanopowders of Li doped ZnO, which are used in fabrication of dye-sensitized solar cell (DSSC). XRD examinations have shown that Li doped ZnO nanopowders synthesized in different concentration have highly crystallized hexagonal structure. To investigate the morphology of nanopowders, scanning electron microscopy (SEM) has been used and the results have revealed the nanoflower morphology of Li doped ZnO powders. Kubelka-Munk function has been utilized to determine the band gap of bare and dye loaded Li doped ZnO samples and an increase from 3.21 eV to 3.24 eV has been observed in the band gap as increasing Li content. The results of solar cell performance of the fabricated Li doped ZnO based DSSC samples have been exhibited that the efficiency of cells increases as the Li doping ratio is boosted and it has been observed the highest efficiency value of 1.23% for LZ10-DSSC.

Influence of CaO doping on phase, microstructure, electrical and dielectric properties of ZnO varistors

In present study, impact of CaO doping on microstructure and phase electrical properties of a ZnO varistor is being reported. The doped ZnO nanopowders were prepared by solution combustion followed by conventional sintering. The ZnO particle size of powders decreased from 22 to 17 nm with CaO doping was noted. Decrease in grain size of the sintered samples from 4.54 to 1.19 μm with CaO doping was observed. This is attributed to Ca4Bi6O13 and Ca0.89Bi3.11O5.58 secondary phase formations apart from pyrochlore and spinel phases. A breakdown field as high as 21 kVcm−1 in X = 1.00 sample was obtained. The Coefficient of nonlinearity (α) decreased from 95 to 42 is due to decrease in carrier concentrations. Increase in resistivity with CaO doping and decrease in resistivity beyond X = 2.5 were noted. The electric modulus plots yielded two relaxations at a temperature in the range 100–300 °C and frequency in the range 0.1 Hz-1MHz. Activation energy (Ea) decreased from 0.65 to 0.50 eV for a region I and from 0.89 to 0.75 eV for region II with CaO doping was observed.

Controlling of surface morphology of ZnO nanopowders via precursor material and Al doping

In this paper, the optimization studies on the structural, morphological and electrical properties of undoped and Al doped ZnO nanopowders by microwave assisted hydrothermal method were performed. The ZnO nanopowders were prepared in different zinc acetate and NaOH molarities and after the determination of the best powder conditions, Al doped ZnO powders were obtained under these conditions. The surface morphology of ZnO nanoparticles is influenced by the starting solution type and molarity. Different morphologies of ZnO microstructures were obtained by adjusting the concentration of Zn2+ and OH−. The structural, morphological, electrical and optical properties of these nanopowders were investigated using X-ray diffractometer, scanning electron microscopy, DC electrical measurements and reflectance measurements. The incorporation of Al in ZnO nanopowder was also changed the morphology of these powders. The presence of Al+3 ions in ZnO nanopowder was determined by XPS measurements. Conductivity and resistivity values of ZnO nanopowders varied with Al incorporation. As the amount of Al in ZnO increases, their resistivities have decreased and their conductivities have increased. The optical band values of Al doped ZnO nanopowders were found via reflectance measurements using kubelka-munk function. As a result of Burstein-moss effect, the optical band values increased with the increase of the Al dopant.

Electronic processes in doped ZnO nanopowders

ZnO nanocrystals, undoped and doped with Iridium or Indium were prepared by solar irradiation in Heliotron reactor in PROMES CNRS facilities, France. The comparative analysis of the excitonic spectra of ZnO single crystal and ZnO nanocrystals (NCs) doped with In and Ir was performed. It is shown that the excitonic processes in Ir doped nanocrystals coincide well with electronic processes in undoped NC and single crystal; however, the electronic processes in In-doped nanocrystals are significantly different from those in single crystal. The radioluminescence spectra of ZnO:In was analysed and additional luminescence band at ∼3.18 eV was detected due to In-doping. The luminescence decay time depends on In concentration in nanocrystals and is significantly less in ZnO:In compared with undoped nanocrystals. The fast scintillation of ZnO:In makes this material promising for application

COMPARISON OF EFFECT OF NICKEL CONCENTRATION ON CRYSTALLOGRAPHIC STRUCTURE AND MORPHOLOGY OF ZINC OXIDE NANOPOWDERS

In this study, we work on the effect of Ni doping on the crystallographic structure, morphology, and optical properties of ZnO nanoparticles. ZnO and Ni doped ZnO nanopowders were synthesized by sol-gel technique with different Ni concentration (5%, 10%, and 15%). The crystallographic structure was characterized by conventional X-ray Diffraction (XRD) technique. The results confirm that Ni doping does not change the single hexagonal phase existing in pure ZnO whereas in high Ni doping concentration (10% and 15%) causes to grow a secondary phase due to presence of NiO. FE-SEM, EDX, FTIR techniques are used for morphology, elemental, and chemical analyses of the samples. Optical properties of the samples are investigated by using UV-VIS spectrophotometer.

Synthesis of Mn doped ZnO nanopowders by MW-HTS and its structural, morphological and optical characteristics

In this study, undoped and Mn doped ZnO nanopowders were synthesized by using the microwave assisted hydrothermal (MW-HTS) method. Doping ratio of Mn in the ZnO was set to 1, 5 and 10%. The effect of Mn concentration on the structural and morphological properties of ZnO nanopowders was investigated using XRD, SEM, XPS and FTIR. XRD results showed that the nanopowders have hexagonal wurtzite structure. The lattice parameters increased with increasing Mn incorporation. SEM images showed that all the samples were formed in nanorod structure and the average diameter of the rods decreased with the Mn concentration. XPS results verified the presence of Mn as a doping element into ZnO crystal lattice and the oxidation states of Mn and Zn. The chemical interactions of ZnO and ZnO:Mn nanopowders were determined for using FTIR spectrum.

Thermal studies of Mn2+-doped ZnO powders formation by sol–gel method

In the present contribution, the study of nanostuctured powders of Mn2+-doped ZnO with different doping concentration (1, 2, 5 at%) was approached. The samples were synthesized by sol–gel method, and the influence of the Mn content on the thermal behavior of the resulted gels was established by thermogravimetric and thermodifferential analysis. Based on the results obtained by thermal analysis, the gels were isothermally treated at 500 °C, 1 h. The XRD powder measurements revealed that all samples had hexagonal wurtzite structure and no other secondary phases were observed suggesting that the Mn2+ ions have substituted Zn sites. Moreover, the incorporation of Mn2+ into ZnO lattice was also confirmed by Infrared and Raman spectroscopy. Energy-dispersive X-ray analysis indicates the existence of Mn2+ in all samples, even in that with 1 at% Mn. The morphology of the samples depends on Mn2+ concentrations. A decrease in the grain size with the increase in Mn2+ concentration was observed. Mn2+-doped ZnO nanopowders with desired structure and properties as promising materials in potential piezoelectric applications, were obtained.

A novel economical grain boundary engineered ultra-high performance ZnO varistor with lesser dopants

A varistor having ultra-high performance was developed from doped ZnO nanopowders using a novel composition consisting of only three (Bi, Ca and Co oxides) dopants. Improved varistor properties were obtained (breakdown field (Eb) 27.5 ± 5 kVcm−1, coefficient of nonlinearity (α) 72 ± 3 and leakage current density (Lc) 1.5 ± 0.06 μAcm−2) which are attributed to the small grain size and grain boundary engineering by phases such as Ca4Bi6O13 and Ca0.89Bi3.11O5.56 along with Co+2 doping in the ZnO lattice. Complex impedance data indicated three relaxations at 25 °C and two relaxations at high temperature (>100 °C). The complex impedance data were fitted into two parallel RC model to extract electrical properties. Two stages of activation energy for DC conductivity were observed in these varistor samples where region I (<150 °C) is found to be due to shallow traps and region II (<225 °C) is due to deep traps. The novel composition is useful for commercial exploitation in wide range of surge protection applications.

Elaboration and nanostructural study of pure and Al doped ZnO nanopowders

Elaboration and nanostructural study of pure and Al doped ZnO nanopowders

High performance multi-layer varistor (MLV) from doped ZnO nanopowders by water based tape casting: Rheology, sintering, microstructure and properties

In this work, we report the fabrication of a high performance multi-layer varistor (MLV) via water based tape casting method using novel compositions of nanomaterials. Bi2O3, CaO and Co3O4 doped ZnO nanopowders were prepared by solution combustion synthesis (SCS) route, calcined at different temperatures (550, 650, 750 and 850 °C) and characterized by TEM, XRD, SEM and AFM. The nanopowder (crystallite size ~30 nm) calcined at 650 °C for 1 h was used as the starting material for MLV fabrication. Compositions of the slurry containing doped ZnO nanopowders, binder and plasticizer in water solvent were optimized for the fabrication of thick film. The rheological properties of the slurries having different solid loadings were analysed and thick films of various thicknesses (50–500 µm) were prepared by varying the feeding rate of tape casting. The film roughness of 38.3 nm for the thick film made from 40 wt% solid slurry was found to be superior compared to other samples due to the presence of reduced crack and shrinkage. MLV fired at 950 °C for 1.5 h exhibited a coefficient of nonlinearity of 18 and breakdown voltage of 291.5 V that yields superior properties compared to commercial MLVs.