Doped ZnO Research Articles

Variation in band gap of antimony doped ZnO nanostructures with doping concentration

ZnO nanostructures were doped with antimony and characterized for structural and optical properties. ZnSbO thin films were fabricated by sol–gel spin coating technology. Structural properties of ZnSbO thin films were investigated by X-ray analysis and FESEM. For determination of transmittance and band gap, UV spectrophotometer characterization was done. XRD reveals single crystal wurtzite structure of ZnSbO thin films. Also results decrease in grain size with doping concentration of antimony in zinc oxide thin films. FESEM and EDAX shows the incorporation of antimony in ZnO. UV spectrophotometer shows increase in transmittance and band gap with doping concentration of antimony in zinc oxide.These results can explore in optoelectronics field.

ZnO-doped PFPAMA: a novel transparent conducting polymer for fast photodiodes

In this article, a new Schottky diode based on a transparent conducting polymer 2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate (PFPAMA) that is doped up to 5% with ZnO is presented. PFPAMA is a promising transparent polymer that is inclined towards n-type behavior with the potential to be used as an electron transport layer. Each device had the Al/p-Si:(PFPAMA:ZnO)/Al structure. The diode ideality factor was found to depend on bias and illumination but the calculated interface state density is lower by 3 orders of magnitude than for most reported Al/p-Si diodes, suggesting that the presence of the polymer suppresses interface states. The measured electrical and photoresponse characteristics confirm that the resulting diodes are suitable for fast photodiodes over the intensity range of dark to 100 mW/cm2 whose performance can be optimized by ZnO doping. The application of functionalized polymers on p-silicon for sensing applications is an emerging field.

Understanding of mobility limiting factors in solution grown Al doped ZnO thin film and its low temperature remedy

The solution grown doped ZnO based transparent electrode has shown great potential in future generation flexible and smart devices due to its abundance in earth, low cost, simple and low temperature synthesis process. But solution grown doped ZnO possesses one major drawback, its mobility decreases rapidly with an increase in doping concentration. To eliminate this issue, the understanding of factors that limiting mobility is a prerequisite. But till date, there are very limited resources with detailed understanding of mobility limiting factors in solution grown TCO. Here in this report, with the morphological, optical and electrical investigations, the mobility limiting factor comes out to be surface related property and assigned to be the defects related to surface adsorbed oxygen and oxygen species at the surface. Furthermore, we have modified the surface to remove the surface adsorbed oxygen species by a low temperature (70 °C) simple solution process. Surface modified sample shows more than two orders of improvement in resistivity without any significant change in the transparency in visible range.

Enhancing the structural, optical and electrical conductivity properties of ZnO nanopowders through Dy doping

• Doping ZnO nanopowders with different Dy percentages was successfully achieved with the co-precipitation method. • XRD analysis reveals a decrease in the lattice parameters and cell volume of the ZnO lattice due to stress relaxation induced by the formation of Dy 2 O 3 secondary on the surface of the nanoparticles. • Crystalline quality was improved on Dy doping. • The optical band gap was decreased on Dy doping where the disorder increased. • Electrical conductivity of ZnO was enhanced by increasing Dy doping concentration up to an optimum doping concentration of 4% and then lowered significantly. In this work, pure ZnO and Dy-doped ZnO nanopowdres (NPs) with varying doping concentration of Dy from 1 to 5 % were successfully synthesized by the co-precipitation method. The effect of Dy doping on the structure, morphology, optical and electrical conductivity of ZnO has been studied. XRD analysis shows that Dy-doped ZnO nanostructures exhibit primary wurtzite structure and a cubic Dy 2 O 3 secondary phase. The average crystallite sizes were found to be 20.14 nm for pure ZnO and in the range of 24–33 nm for Dy-doped NPs. Crystallite size of Dy-doped ZnO NPs increases with increasing Dy concentration from 1 % to 3 % and then decreases as Dy increases. The decrease in crystallite size was explained by the formation of Dy - O - Z n bonds on the surface of ZnO. Lattice parameters ( a and c ) and unit cell volume ( V ) decrease as Dy content is initially increased up to 2 % then increase for further increase in Dy content. The initial decrease in a , c and V is due to strain relaxation stresses resulting from the formation of Dy 2 O 3 secondary phase. FTIR spectra indicate the formation of the secondary phase and confirm the successful incorporation of Dy 3 + ions into Zn 2 + sites in ZnO structure. Optical band gap of pure and Dy-doped ZnO nanoparticles was evaluated from diffuse reflectance spectroscopy (DRS) spectra and found to be reduced in Dy-doped samples. Optical band gap decreases from 3.269 eV to 3.226 eV for the 1 % Dy-doped sample then increases on further increasing Dy concentration up to 4 % (3.252 eV) and slightly decrease again at 5 % (3.247 eV). PL emission spectra of Dy-doped samples, show the enhancement of the orange-red emission and the appearance of emission band at around 580 nm which may be assigned to the electrical dipole transition of Dy 3 + ions. The electrical conductivity was enhanced by increasing Dy concentration up to an optimum doping concentration of 4 %, then decreases significantly due to scattering of charge carriers caused by the excess of the secondary phase on the surface of ZnO nanoparticles.

Combined effects of electron doping and surface polarity on the ferromagnetism in Gd implanted polar ZnO wafers

The microstructural, electrical and magnetic properties of Gd-doped and (Al, Gd) codoped Zn-polar and O-polar ZnO wafers manufactured by the ion implantation method are systematically and comparatively investigated. We report an intrinsic ferromagnetic behaviour of Gd-implanted polar ZnO wafers enhanced by Al codoping. It was found that the saturation magnetization for the doped O-polar ZnO wafer is stronger than that of the implanted Zn-polar ZnO wafer. The introduction of Al ions into Gd-implanted polar ZnO enables a further improvement in the ferromagnetism that is directly relevant to the carrier concentration. This finding suggests that the carrier-mediated exchange mechanism may account for the establishment of the long-range ferromagnetic order in the doped ZnO wafers. First-principles calculations confirm that the interaction between the Gd-4 f state and the O-2p state is stronger in oxygen polar ZnO, producing a higher magnetic moment. The increase in the magnetic moment of (Al, Gd) co-implanted ZnO is mainly derived from hybridization of the Al and O orbitals. Our results confirm that larger ferromagnetism can be obtained in Gd-doped O-polar ZnO wafers and that the magnetization can be effectively improved by controlling the electron doping concentration, which highlights the viability of developing spintronic devices based on polar ZnO by codoping magnetic ions and group Ⅲ elements.

Photocatalytic and antimicrobial activities of pure and Mn doped ZnO nanoparticles synthesised by Annona Muricata leaf extract

ABSTRACT The present work aim to investigate the photocatalytic, antibacterial and antifungal activities of Zn1-xMnxO (x = 0.0, 0.03, 0.05 and 0.07) nanoparticles synthesised using the leaf extract of Annona Muricata via green synthesis method. The effect of Mn doping in the obtained nanopowder were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and UV-visible spectroscopy techniques. XRD pattern confirms hexagonal wurtzite structure of ZnO nanoparticles. Incorporation of Mn into the ZnO host lattice was confirmed by XPS measurement. Morphology of nanoparticles shows irregular, spherical shapes with agglomeration. Presence of Zn, Mn and O elements in the EDAX reveals the perfect nature of nanostructures. The synthesised pure and Mn-doped ZnO nanoparticles were found to be significant antibacterial activity against gram positive Bacillus subtilis, Staphylococcus aureus and gram negative Pseudomonas aeruginosa bacterial pathogens as well as the fungal strain of Candida albicans and Aspergillus Niger. The minimum zone of inhibition observed for bacterial and fungal pathogens confirms better antimicrobial activity of ZnO nanoparticles. The Mn-doped nanoparticle shows comparatively enhanced removal of methylene blue (MB), malachite green (MG) and Congo red (CR) dye under sunlight. These results indicates the green synthesised pure and Mn-doped ZnO nanoparticles have valuable applications in environmental and biomedical fields.

Morphology and Optical Properties Analysis of Cu2+ Doped ZnO for Preparation Dye Sensitized Solar Cell (DSSC)

This research reported Cu2+ un-doped (pure) and doped ZnO semiconductors with variations in Cu2+ concentrations of 3%, 4% and 5% through the sol gel method which aims to determine the morphology and optical properties of ZnO has been investigated. In addition, ZnO film was coated using the doctor blade method with the addition of chlorophyll as a dye sensitizer. Morphological and elemental content tests were carried out using SEM and EDS. The optical properties were analyzed by taking Transmittance data using a UV-Vis Spectrophotometer. SEM analysis with 9900X magnification showed that all samples had small grain sizes and the pores formed were uneven (heterogeneous). The EDS analysis showed that all samples had a higher concentration of zinc by weight than oxygen. UV-Vis Spectrophotometer analysis shows that the transmittance value without dye is lower than using Dye. The addition of Cu2+ concentration affects the morphology and optical properties of ZnO. The higher the addition of Cu2+ added chlorophyll, the higher the absorbance value, so that the transmittance value decreases. The addition of 4% concentration showed the maximum value of chlorophyll as a sensitizer.

Study of the Glycerol Hydrogenolysis Reaction on Cu, Cu-Zn, and Cu-ZnO Clusters.

Quantum chemistry calculations have been performed to access the efficacy of Cu-based catalysts in various mechanistic steps of the glycerol hydrogenolysis reaction. Calculations are first performed for reactants in the gas phase (noncatalyzed system) and reactants in the gas phase with a 3-atom Cu cluster (catalyzed system). We demonstrate that the glycerol to ethylene glycol conversion is preferred in the noncatalyzed system but glycerol conversion to 1,2-propanediol via the 2-acetol intermediate is preferred in the catalyzed system. We next analyze the adsorption energies of the reactant and product species involved in the glycerol to 1,2-PDO reaction on an 8-atom Cu cluster and Cu cluster doped with a Zn atom or a ZnO molecule. Finally, we study the effects of Zn or ZnO doping on the activation barriers of the two steps of the glycerol to 1,2-PDO reaction.

Characterization and antibacterial activity of Ti doped ZnO nanorods prepared by hydrazine assisted wet chemical route

In this study, a simple hydrazine assisted wet chemical method was used to prepare pure and Ti doped ZnO nanorods . The structural properties of pure and Ti doped ZnO nanorods were investigated by XRD analysis. Williamson-Hall (W–H) method was used to determine the crystallite size , strain and dislocation density of the samples. TEM analysis revealed rod like morphology for Ti doped ZnO nanoparticles . The presence of elements such as Zn, Ti and O of the doped sample was confirmed by EDS. XPS spectrum suggests that Ti 4+ ions well substitute Zn 2+ ions in doped nanocrystal . The Raman study further established the formation of ZnO wurtzite structure in both pure and Ti doped ZnO nanorods. The band gap of pure and Ti doped ZnO nanorods were estimated by the Tauc relation as 3.03 eV and 2.91 eV respectively. From the PL spectra, it is observed that the intensity of the polychromatic defect emissions of Ti doped ZnO nanorods is higher than pure ZnO, with some additional defect emissions. The antibacterial activity of Ti doped ZnO nanorods slightly decreased against gram-positive and gram-negative bacteria when compared to pure ZnO. • Synthesis of pure and Ti doped ZnO nanorods by a facile hydrazine assisted wet chemical method. • Confirmation of substitution of Ti 4+ ions into Zn 2+ ions in doped nanocrystal from XPS spectrum. • The band gap of pure and Ti doped ZnO nanorods were estimated by the Tauc relation as 3.03 eV and 2.91 eV. • Intensity of the polychromatic defect emissions of Ti doped ZnO nanorods is higher than pure ZnO. • The antibacterial activity of Ti doped ZnO nanorods is slightly lower than pure ZnO and higher than certain doped ZnO nanostructures.

Facile synthesis and excellent microwave absorption performance of ultra-small ZnO-doped onion-like carbon nanoparticles

Ultra-small ZnO-doped onion-like carbon (ZnO-OLC) nanoparticles (NPs) were synthesized by metal organic chemical vapour deposition, and OLC NPs were subsequently obtained by HCl treatment of the as-synthesized ZnO-OLC NPs. For the ZnO-OLC NPs, an optimal reflection loss of −58.7 dB and a wide effective bandwidth of 7.0 GHz were achieved at a very low filler weight loading ratio of 5%; superior to those of OLC NPs. Experimental results and theoretical analyzes indicated that the ZnO dopant could degrade the permittivity and polarization loss of the OLC NPs due to interaction between Zn, O and C atoms, and thus improve their impedance matching and microwave absorption performance. This work provides a new insight into how the ZnO doping affects the microwave absorption performance of OLC NPs from a theoretical point of view, and is expected to be a useful reference for the future design of related microwave absorbers.

Tuning the workfunction of ZnO through surface doping with Mn from first-principles simulations

Surface doping of ZnO allows for the tailoring of the surface chemistry of the material while preserving the superb electronic structure of the bulk. Apart from obvious changes in adsorption energies and activation energies for catalysis, surface doping can alter the workfunction of the material and allow it to be tuned for specific photocatalytic and optoelectronic applications. We present first-principles electronic structure calculations for surface doping of Mn on the ZnO (0001) surface. Various dopant concentrations have been considered at the out-most (surface) layer of Zn atoms, while the interior of the material is kept at the ideal wurtzite structure. For each system, the surface energy and surface workfunction have been calculated. Both workfunction and surface energy drop with increasing Mn concentration for O-terminated surfaces, while more complex behaviour is observed in metal-terminated ones. We discuss trends in surface stability and surface electronic structure of this material and how they affect its properties.

Enhanced ferro magnetism of (Cu, Fe/Mn) dual doped ZnO nanoparticles and assessment of in-vitro cytotoxicity and antimicrobial activity for magnetically guided immunotherapy and hyperthermia applications

Cu and Fe/Mn dual doped ZnO magnetic nanoparticles (MNPs) had been synthesized by sol-gel method. Characterization of synthesized MNPs showed the fine and significant size of MNPs, it had ferromagnetism property at room temperature, and (Cu, Fe) dual doped MNPs were found to have maximum saturation magnetization with larger hysteresis area. In-vitro cytotoxic assessment of these MNPs revealed that 20 ng of Cu doped ZnO MNPs are nontoxic to human PBMC with 60% viable cell count, whereas Fe dopant increases cell viability by 5% in the same concentration. These MNPs showed a significant (20–25 mm ZOI) antimicrobial activity against Pseudomonas putida and Bacillus subtilis bacteria. Particularly Fe dopant showed increased antimicrobial activity against gram-positive (B. subtilis), whereas Mn dopant doesn't have considerable antimicrobial activity. Having known that these MNPs are biocompatible with the ferromagnetic property they may be considered for magnetic guided immunotherapy and hyperthermia applications.

Effect of rGO support on Gd@ZnO for UV–visible-light driven photocatalytic organic pollutant degradation

In this manuscript, we report the hydrothermally prepared rGO/Gd@ZnO nanocomposite for the utilization of photocatalytic Rh B (rhodamine B) dye degradation. The required characterization techniques were carried out to analyse the structural, morphological, chemical, environmental and optical behaviour of the prepared nanoparticles. Photocatalytic efficiency of the prepared nanoparticles was studied by Rh B dye degradation upon UV–Vis-light illumination which reveals that composite catalyst degrades the dye molecule about 91% after 40 min of irradiation. On comparing the higher degradation efficiency of the rGO/Gd@ZnO nanocomposite with that of ZnO and Gd doped ZnO, it reveals a greater reduction of charge carriers’ recombination, higher visible-light utilization and higher adsorption efficiency. Elemental trapping experiment and recycling test were conducted to study the influence of active radicals for the degradation reaction and to know the stability of the prepared nanocomposite, respectively. Hence, this rGO supported Gd doped ZnO nanocomposite can provide a new path way in preparing a highly efficient photocatalyst for organic pollutant degradation at large.

Humidity-induced synaptic plasticity of ZnO artificial synapses using peptide insulator for neuromorphic computing

Neuromorphic devices inspired by the human brain have attracted significant attention because of their excellent ability for cognitive and parallel computing. This study presents ZnO-based artificial synapses with peptide insulators for the electrical emulation of biological synapses. We demonstrated the dynamic responses of the device under various environmental conditions. The proton-conducting property of the tyrosine-rich peptide enables time-dependent responses under ambient conditions such that various aspects of synaptic behaviors are emulated by the devices. The transition from short-term memory to long-term memory is achieved via electrochemical doping of ZnO by protons. Furthermore, we demonstrate an image classification simulation using a multi-layer perceptron model to evaluate the potential of the device for use in neuromorphic computing. The neural network based on our device achieved a recognition accuracy of 87.47% for the MNIST handwritten digit images. This work proposes a novel device platform inspired by biosystems for brain-mimetic hardware systems.

Enhancing the electrochemical performance of graphene supercapacitors by coating their electrodes with a slurry-paste of ZnO:Al, ZnO:Ga and ZnO:In

This investigation reports the morphological and structural properties of ZnO doped with the Al, In and Ga elements and its utilization as redox material to improve the capacitance and energy density of graphene supercapacitors (SCs). All the ZnO nanoparticles doped with these elements presented a plate-like morphology with irregular edges and had hexagonal wurtzite phase. Moreover, the values of band gap were obtained for the ZnO nanoparticles and they are reduced with the order of: ZnO:Ga (3.2 eV)>ZnO:In (3.0 eV)>ZnO:Al (2.95 eV). The results of electrochemical characterization revealed that the graphene SCs made without ZnO presented a maximum capacitance and energy density of 97.2 F g−1 and 19.4 Wh kg−1, respectively. After the deposition of the Al, In or Ga-doped ZnO nanoparticles to the SC electrodes, the capacitance and energy density are enhanced by 22–193%. The maximum values of capacitance and energy density of 284.6 F g−1 and 56.9 Wh kg−1 were observed for the SC made with ZnO:Al. Moreover, the analysis by Raman and photoluminescence demonstrated the presence of Zinc interstitials, oxygen vacancy and oxygen interstitials defects, which served as redox centers for the charge storage in the solid state SCs. In general, this research confirmed that adding doped ZnO into the SCs is a good strategy to increment their performance, which is of interest for energy storage applications.

Fast UV photoresponse from Aluminum doped zinc oxysulphide composite nanowires by efficient charge-exchange interactions

For the development of technologically advanced material for the next-generation smart electronic devices, we prepared zinc oxysulphide (ZnOS) composite nanowires (NWs) through a two-step process. The electronic and optical properties of this system are further influenced by doping with aluminium. First, 2 at.% Al-doped ZnO NWs were prepared on Si and then it is subjected to sulphidation process for different time durations. Sulphidation for short duration results in a core-shell structure and ZnOS composite structure was achieved after 4 h of sulphidation. We systematically studied the structural, photoluminescence and UV photoresponse properties of the ZnOS composite NWs to investigate the superiority of this kind of semiconducting composite material. Structural characterization of the ZnOS NWs confirms hexagonal crystalline composite structure with small clusters of ZnS phase. Interestingly, these ZnOS composite NWs emit three different colours of emission in UV, blue and green regions. UV photoluminescence (PL) intensity is found to gradually increase with the increased duration of the sulphidation process. We obtained a significant improvement in the UV photoresponse behaviour of the ZnOS composite NWs compared to the bare doped ZnO NWs. The obtained photoresponse time is much faster (200 ms) than the case of virgin ZnO NWs (∼ several seconds) as well as with high responsivity (0.29 A/W). The observed improved PL and fast UV photoresponse are explained based on hoping charge transfer through the interface and modification of defects that is supported by x-ray photoelectron spectroscopy data. Therefore, prepared ZnOS composite NWs is found to be a technologically advanced material for the application as an efficient UV photosensor.

Magnetic properties in randomly diluted magnetic systems: Co-doped ZnO polycrystalline ceramics

The influence of structural defects on the magnetic properties of Co-doped ZnO polycrystalline ceramics (Zn1−xCoxO) with 0.00 ≤ x ≤ 0.05 sintered by a pressure-less solid state reaction method were investigated in a broad range of temperatures (5 ≤ T ≤ 300 K) for applied magnetic fields up to 85 kOe. The hysteresis loops indicated the presence of diamagnetic behavior for undoped ZnO samples while both antiferromagnetic (AFM) and paramagnetic (PM) ordering for Co-doped ZnO. The saturation magnetization Ms values decrease with increasing Co concentration (x), being ~ 2.5 μB∕Co and ~ 1.6 μB∕Co for x = 0.005 and x = 0.05, respectively, T = 5 K. Also the fraction of the saturation magnetization values were found to be 0.83 (83 % PM), 0.66 (66 % PM) and 0.62 (62 % PM) for samples (x) 0.005, 0.02, and 0.05, respectively. The decrease of PM ordering with x, could be attributed to the shortening the distance between adjacent Co ions which favor the AFM coupling due to super-exchange interaction. In addition, the Jex∕kB values were found to be negative, being − 20, − 30, and − 31 for x = 0.005, 0.02, and 0.05, respectively, indicated the absence of FM coupling for all Co-doped ZnO samples. The reduction in Jex∕kB values are due to the increase of AFM ordering for Co ions homogeneously diluted in the ZnO structure during sintering process at high temperatures (≥1100 °C). Even though the presence of a large number of structural defects in both pure and doped ZnO ceramic samples reveled by Raman and UV-Vis spectroscopy analysis the ferromagnetic (FM) ordering was not present for the broad range of temperatures (5 ≤ T ≤ 300 K) studied.

Structural and antibacterial properties of doped zinc oxide and their composites with hydroxyapatite

ZnO nanoparticles (NPs) doped by Mn2+ and Cu2+ ions at various doping levels and their hydroxyapatite (HA) composites are prepared by a facile hydrothermal and sol-gel method. The resultant doped ZnO NPs are of wurtzite crystal structure and nanorod morphology. The doping of transition metals in ZnO lattice structure offers feasible means to prepare effective antibacterial agent. The antibacterial property against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus) shows that both Mn and Cu-doped ZnO NPs are more sensitive to S. aureus and revealed improved antimicrobial activity relative to pristine ZnO. 5% Mn and 10% Cu-doped ZnO NPs exhibited the best antibacterial property. Moreover, the composites by loading 10 wt% Mn-doped ZnO and 10 wt% Cu-doped ZnO on HA exhibit significant antibacterial activity. The CCK-8 experiments show that ZnO/HA composites are noncytotoxic and can promote osteosarcoma cell growth.

Physical investigations on Ni doping ZnO thin films along with ethanol response

Physical investigations on Ni doping ZnO thin films along with ethanol response

CdS Coated Mn Doped ZnO Nanospheres as Textile Catalyst: Fabrication, Physicochemical Techniques and Dye Removal Under Natural Light

ZnO as a promising photocatalyst has gained much attention for the removal of organic pollutants from water. However, the main drawbacks of the relatively low photocatalytic activity and high recombination rate of photo excited electronhole pairs, restrict its potential applications. Promoting the spatial separation of photo excited charge carriers is of paramount signi? cance for photocatalysis, because the dierence in the band positions make the potential gradient at the composite boundary. In this work, our aim is to enhance the photocatalytic efficiency of CdS coated Mn doped ZnO nanospheres under solar light irradiation. Objectives in this work are, to fabricate the CdS coated Mn doped ZnO nanospheres by a simple ethanolic dispersion method, and its applied for testing the photocatalytic activity of methylene blue (MB) dye. The fabricated binary composites were analyzed with different physicochemical techniques like PXRD, SEM with EDX, UV-DRS, PL and TEM. The photocatalytic degradation results have revealed that, the CdS coated Mn doped ZnO nanospheres exhibits admirable activity toward the photocatalytic degradation of the MB. The remarkably enhanced photocatalytic activity of CdS coated Mn doped ZnO nanospheres can be interpreted in terms of lots of active sites, which efficiently separate the photo generated electron and holes. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photo generated O2 -and. OH radicals play a crucial role in photo degradation reactions under visible light irradiation. This work suggests that, the rational design and construction of heterostructures is powerful for developing highly efficient, and reusable visible-light photocatalysts for environmental purification and energy conversion. The enhanced photo degradation activity indicates the potential of the nanocomposite for the treatment of organic pollutants from the textile wastewater.