Co-doped ZnO Research Articles

First Principles Study of Electronic and Optical Properties of Al-P Co-Doped ZnO in the Presence of Zn Vacancies.

The BP neural network optimized by the Adam algorithm was used to predict the defect formation energy of Al-P co-doped ZnO systems with different concentrations of P replacing O under the presence of different concentrations of VZn. It was found that the easily formed AlZnPo-1VZn, AlZnPO-2VZn, and AlZn2PO-1VZn systems. The first principles of density function were used to study the geometric, electronic, and optical properties of each system. The simulation results show that the bandgap values of the three systems have decreased relative to the intrinsic ZnO, among which AlZnPO-1VZn and AlZnPO-2VZn is still a p-type conductive system, AlZnPO-2VZn has the highest conductivity. From the analysis of reflectivity, absorption rate, and light transmittance, AlZn2PO-1VZn has the most relatively excellent optical properties, followed by AlznPo-2VZn.

Coral-like Co-doped ZnO nanostructures for enhanced triethylamine detection

In this work, coral-like Co-doped ZnO nanostructures were obtained using simple precipitation and hydrothermal methods. Co-doping reduced the composite particle size to 20 nm, and the controlled growth direction formed a larger adsorption area. The gas sensor results suggest that the maximum response to triethylamine at 200 °C was achieved at 5 mol% doping content. The sensor also performed well for the 30-day stability test, displaying excellent selectivity and repeatability. Besides, 5CZO showed a response-recovery time of 52/70 s and a good response to different gas concentrations. The doping mechanism for the improved gas sensing performance with triethylamine was thoroughly investigated.

Ab Initio Study of the Influence of Spin and Orbital Magnetic Moments on the Stability of Magnetic and Charge Distribution in Co:ZnO Monolayer.

The development of ultrathin magnets with tunable magnetic properties is essential for advancing quantum computing technologies. In this study, density functional theory (DFT) calculations were employed to investigate the atomic and electronic structures of a ZnO monolayer embedded with cobalt atoms. The impact of spin dynamics on charge transfer within the Co:ZnO system was thoroughly examined. Results revealed that the orbital magnetic moment of the cobalt atoms plays a crucial role in stabilizing the magnetic and charge distributions across the system. These findings offer valuable insights for the design and fabrication of quantum devices, thereby highlighting the potential of Co-doped ZnO monolayers in quantum computing applications.

Co-doped ZnO nanofibers fabricated via electrospinning for rapid and ppb-level detection of listeria biomarker 3-hydroxy-2-butanone

Listeria monocytogenes, a food-borne pathogen capable of releasing biomarker 3-hydroxy-2-butanone (3H-2B), generally causes a serious threat to human health. Developing 3H-2B gas sensor with excellent performance is of great significance in the diagnosis and prevention of Listeria. Here, we have successfully fabricated Co-doped ZnO nanofibers gas sensor via an electrospinning method, which can be well used for real-time monitoring of Listeria. The results show that the Co-doped ZnO nanofibers have a wurtzite crystal structure and a nanofiber-like morphology with a diameter of 62 nm. The band gap (3.15 eV) of the Co-doped ZnO is significantly narrower than that of the pure ZnO (3.25 eV). The response (168) of the 0.5%Co-doped ZnO based sensor to 100 ppm 3H-2B at 305 °C is 5.37 times greater than that of the pure ZnO (31.3), with a high selectivity, a lower detection limit (100 ppb) and a short response time of 1 s. The enhanced gas sensing mechanism is ascribed to the depletion layer on the ZnO surface, a superposition effect of interface barrier, and the narrowed band gap of the ZnO.

Optical properties analysis of gelatin-based prepared Co, Ni, and Mn-doped ZnO nanoparticles in infrared and UV–vis region using Kramers-Kronig methods

This study investigates the structural, optical, and morphological properties of ZnO nanoparticles doped with Ni, Mn, and Co (Zn0.97A0.03O where A = Ni, Mn, and Co, designated as ZN, ZM, and ZC, respectively). X-ray diffraction (XRD) analysis confirms the successful incorporation of dopants into the ZnO lattice without altering its wurtzite structure. Field emission scanning electron microscopy (FESEM) images reveal that doping results in larger and more uniformly distributed particles. Energy-dispersive X-ray spectroscopy (EDX) verifies the presence of Ni, Mn, and Co in the respective samples. Fourier transform infrared (FTIR) spectroscopy indicates an increase in average phonon energies due to doping, as evidenced by the shift in the Zn-O vibration peak. Ultraviolet–visible (UV–vis) spectroscopy shows that doping causes a blue shift in the absorbance peak and increases the optical band gap from 3.17 eV for pure ZnO to 3.22 eV for Co-doped ZnO. Transmission electron microscopy (TEM) and corresponding EDX results further confirm the presence of dopants and illustrate that doped ZnO nanoparticles are larger than pure ZnO particles. These findings provide valuable insights into the impact of doping on ZnO nanoparticles, potentially enhancing their suitability for various technological applications.

A Comparative Study of Congo Red Textile Dye Photodegradation Using ZnO Al and ZnO Al+Mn Nanoparticles

Photodegradation of Congo Red textile dye was successfully carried out using ZnO Al and ZnO Al+Mn nanoparticles synthesized using the bottom-up coprecipitation method. Powder X-ray diffraction provides information that Al and Mn doping successfully inserted in the host crystal structure while maintaining the Hexagonal Wurtzite crystal structure. However, a shift in the diffraction peak caused by the lattice distance changes with the addition of doping. FE-SEM EDS provides information that both nanoparticles are nonuniform sphere-like due to the addition of dopping, and each dopping is detected through EDS spectra. There is a decrease in the gap energy in each sample. ZnO Al nanoparticles have a gap energy of 3.29 eV, and ZnO Al+Mn nanoparticles have a gap energy of 3.28 eV. However, the decrease in the gap energy is not directly related to the percentage and kinetic rate of Congo Red photodegradation. Adding 5 mg of ZnO Al Nanoparticles powder could degrade Congo Red up to 97.9 % within 120 min using UV A radiation or 0.03504/min. At the same time, adding ZnO Al+Mn Nanoparticles powder with the same parameters could only degrade 67.6 % or 0.00759/min. HIGHLIGHTS Energy Bandgap Modification of ZnO Nanoparticles The incorporation of Al single dopants and Al, Mn co-dopants into ZnO nanoparticles synthesized via a bottom-up coprecipitation method significantly alters the energy bandgap. Al single doping resulted in a bandgap of 3.29 eV, while Al, Mn double doping yielded a bandgap of 3.28 eV. Enhanced Photocatalytic Activity of Al-Doped ZnO Al-doped ZnO nanoparticles exhibited superior photocatalytic activity toward the degradation of Congo Red textile dye. With a photodegradation rate constant of 0.03504 min⁻¹, these nanoparticles achieved 97.9 % degradation of Congo Red within 120 minutes. Comparative Photocatalytic Performance of Al, Mn Co-Doped ZnO While Al, Mn co-doped ZnO nanoparticles were synthesized using the same method, their photocatalytic performance for Congo Red degradation was notably lower than that of Al-doped ZnO. The calculated photodegradation rate constant was 0.00759 min⁻¹, resulting in 67.6 % degradation within the same timeframe. GRAPHICAL ABSTRACT

Preparation, characterization and biological activity of Co-doped ZnO nanostructured thin film: A comprehensive study on its photo-physical properties and antimicrobial efficacy against food-borne pathogen

The Co@ZnO thin film deposited on glass substrate with dopant contents of cobalt ranging from 0 to 10 % were fabricated using spray pyrolysis coating method. The prepared nanocomposite thin film was characterized by scanning electron microscopy, X-ray diffraction, UV–vis and Raman spectroscopy. Some surfaces structural probing of the deposited samples confirmed nanolamination of hexagonal wurtzite phase of ZnO with no other impurity phases and high adherence on the soda lime glass substrate. Average grain sizes (56–43 nm) and lattice strain of the films were found to be tailored with the variation of Co-dopant content, signifying phonon confinement or defect/disorder caused by the Co-dopant impurity on the ZnO host particle owing to the impurity levels and oxygen vacancy states. The film demonstrated high optical transmittance with enhanced photoabsorbtion and narrow optical band gap (3.24–2.64 eV) with increasing Co-dopant content. In evaluating its antibacterial efficacy, the Co@ZnO thin film was tested at different dopant concentration against Bacillus cereus (foodborne pathogen). The result revealed that the films exhibits excellent inhibitory effect on the pathogen, with highest activity obtained at 10 % Co@ZnO. Furthermore, a more improved inhibitory activity was recorded when at 10 % Co@ZnO dopant was exposed to UV irradiation.

Synergistic impact of lanthanum and cerium co-doping ZnO for improved photocatalytic rhodamine B degradation efficiency under UV light

In this study, the influence of different La and Ce co-doping amounts on the structural, morphological, optical, and photodegradation properties of ZnO nanostructures was evaluated. Zn1-2xLaxCexO nanoparticles (NPs) were prepared using sol-gel auto-ignition process, where x = 0.00 (pure ZnO), 0.01 (LC1), 0.03 (LC3), and 0.05 (LC5). The X-ray diffraction (XRD) and Raman results revealed that the prepared ZnO NPs crystallize in the hexagonal wurtzite structure. The size of crystallites is affected by the increment of La and Ce and it decreased from 24.29 nm to 10.40 nm with the increase in the concentration of La and Ce. Transmission electron microscopy (TEM) showed that the samples exhibit an irregular distribution of NPs with a dominant spherical shape morphology. The simultaneous incorporation of La and Ce in ZnO NPs led to a slight variation in the absorption edge and a slight shift in the values of the band gap energy from 3.20 to 3.24 eV. Furthermore, a reduction in the recombination rate of photogenerated charge carriers and the creation of fewer additional defects upon the appropriate insertion of Ce and La ions are highlighted by the analysis of photoluminescence spectra, Nyquist plots, and transient photocurrent measurements. The photocatalytic activity of samples was evaluated against rhodamine B organic dye under UV light irradiation. The analysis showed that LC1 sample exhibited superior photocatalytic performance with 99.1% degradation efficiency and a degradation rate constant of 0.0762 min-1. This enhancement has been ascribed to the surface defects and the optimized crystallite size achieved, which help to generate reactive entities such as •OH and O2•− in addition to the great role of holes (h+) and impede the recombination of charge carriers e-/h+.

Enhancing Efficiency of Dye-Sensitized Solar Cell using Mn or Ce Doped and Co-doped ZnO Photoanodes with Lawsonia Inermis Natural Dye

Abstract In the present research paper, Mn (transition metal) and Ce (rare earth metal) doped and co-doped ZnO nanoparticles were synthesized using a cost-effective sol-gel technique. As synthesized samples were characterized using X-ray diffraction and field emission scanning electron microscope to examine the structure and morphology respectively. The optical properties were examined by UV-Visible and photoluminescence spectroscopic techniques. The synthesized samples were used as photoanode for the fabrication of dye-sensitized solar cell (DSSC). The utilization of a photoanode, containing Mn and Ce doped and co-doped in ZnO, in DSSC leads to a significant enhancement in photovoltaic conversion efficiency with natural dye lawsonia inermis. Different combinations of Mn or Ce doped and co-doped ZnO nanoparticles were used for testing their effectiveness as photoanode in DSSC. It was observed that the efficiency for Mn and Ce co-doped ZnO photoanode-based DSSC was found to be 0.2118%, which is approximately a 750% increase as compared to bare ZnO photoanode based DSSC. The enhancement in the efficiency of DSSCs was due to the formation of a blocking layer by Mn ions which helps to stop the flow of electrons backward and the broadening of the spectrum region with the help of Ce ions using up/down conversion process also helps to achieve higher efficiency. This enhancement in the efficiency of DSSC may be attributed to the synergic effect of Mn and Ce.

Tailoring Sb-F doped ZnO nanoparticles for dual-functionality: Photocatalytic and supercapacitor applications

In the present work, pure zinc oxide nanoparticles (ZnO NPs), antimony doped ZnO nanoparticles (Sb-ZnO NPs), fluorine doped ZnO nanoparticles (F-ZnO NPs), and antimony and fluorine co-doped ZnO nanoparticles (Sb/F-ZnO NPs) with various dopant concentrations are synthesized by co-precipitation method. The optical, structural, morphological, photocatalytic, and electrochemical activities of ZnO nanostructures by the influence of Sb and F doping were investigated. XRD showed crystallite size decreased with increasing Sb/F content, while BET showed 64.25 m2/g surface area for ZnO-5 %Sb-10 %F. SEM and TEM images suggesting Sb/F doping changed the ZnO morphology from spherical to bricks-built and nanorod-built flower structures. XPS verified Sb (+3) and F (−1) oxidation states, while absorption spectroscopy showed increased energy bandgap with 5 % Sb and 10 % F doping in ZnO. The photocatalytic activity for mixture of congo red, rhodamine B, and methylene blue are closer to real polluted water. All the samples exhibited good photocatalytic activity for the methylene blue with degradation efficiency reaching to 99 %. At a constant current density of 1 A/g, symmetric supercapacitors utilizing Sb/F-ZnO electrodes exhibited a specific capacitance of 762 Fg−1, underscoring their superior electrochemical performance and potential for advancing energy storage technologies. Further, physiochemical and electrochemical properties of ZnO can be perfectly tuned by the optimal setting for co-doping in ZnO up to 5 % Sb and 10 % F by the co-precipitation approach.

Stepwise-Induced Synthesis and Excellent Corrosion Protection of Ce/Eu Codoped ZnO Solid Solution Materials.

Under purely inorganic conditions, a synthesis route was devised wherein elements were introduced stepwise via coprecipitation based on differences in compound solubility. This synthesis method can change the microscopic morphology of the material without relying on a templating agent, resulting in the formation of the multilayered lamellar Ce/Eu codoped zinc oxide solid solution (ZCEOSS) with a self-assembled nested imbrication structure. The study improves the critical matter of corrosion by focusing on the electron and energy transfer mechanisms. By introduction of the bandgap modulator cerium element and fluorescence enhancer europium element into the ZnO material, the anticorrosion material has been successfully endowed with both photocathodic protection and luminescent initiative/stress dual corrosion defense functions. Due to the energy level staircase protection mechanism synergistically generated by the 4f electron shell of rare-earth elements in concert with semiconductor zinc oxide, the energy band positions were modulated to progressively guide the direction of electron flow, thereby suppressing corrosion reactions. In particular, the ZCEOSS material synthesized by doping 1% cerium and 7% europium and adding rare-earth elements at pH 7 exhibited the best corrosion inhibition performance. After immersion in simulated seawater for 96 h, Tafel polarization test results showed that compared to epoxy resin and ZnO anticorrosion systems, the ZCEOSS anticorrosion system exhibited significantly improved corrosion inhibition efficiency with enhancements of 1028.3 and 402.9%, respectively. This study provides new insights into the development of highly efficient inorganic anticorrosion materials.

Expression of Concern: Solar light driven enhanced photocatalytic treatment of azo dye contaminated water based on Co-doped ZnO/ g-C3N4 nanocomposite

Expression of Concern: Solar light driven enhanced photocatalytic treatment of azo dye contaminated water based on Co-doped ZnO/ g-C3N4 nanocomposite

Impact of Pd2+ and Sn4+ co-doping ZnO nanoflakes toward high-performing Schottky diode based on the generation of intermediate bands within the energy gap

Pd:Sn/ZnO nanohybrid was prepared by chemical co-precipitation route and identified using XRD, EDX, SEM, and TEM techniques. The microstructure analysis emphasized the polycrystalline nature in which Pd and Sn ions were substituted inside ZnO framework to form the nanocomposite. The surface morphology was appeared in 2D nanoflakes with large specific surface area. The optical parameters including Eg, n, and k were deduced from T% and R% spectra through wavelength range 300–1400 nm. The thin film showed strong optical absorption inside the UV region with a value of Eg = 3.10 eV. The Ag/Pd:Sn/ZnO/p-Si/Al Schottky diode was fabricated by thermal evaporation technique, and its electronic and photodetector properties were investigated from I–V and C–V measurements. The fabricated device exhibited non-ideal behavior with high rectification ratio RR = 935 and a relatively small Rs lies between 2365 and 2755 Ω. Under illumination impacts, the photodiode exhibited high photosensitivity and responsivity attributed to the large photo-induced charge carriers.

Cobalt-doped ZnO nanoparticles and PLD-deposited thin film forms: structure, optical properties and nature of magnetic anisotropy.

Cobalt-doped zinc oxide nanoparticles (NPs) were synthesized using a modified sol-gel method. Thereafter, the obtained powder was deposited on a Suprasil glass substrate by employing a pulsed laser deposition (PLD) technique. X-ray diffraction analysis with Rietveld refinement confirmed a hexagonal wurtzite ZnO phase belonging to the P63 mc space group for both samples in the NP and thin film forms. In particular, the thin film exhibited an intensive (002) XRD peak, indicating that it had a preferred c-axis orientation owing to the self-texturing mechanism. No segregated secondary phases were detected. The crystallite structure, morphology, and size were investigated using high-resolution transmission electron microscopy (HRTEM). To study the crystalline quality, structural disorder, and defects in the host lattice, we employed Raman spectroscopy. UV-vis-NIR spectroscopy was performed to confirm the nature of the Co-doped ZnO NP powder and the film. The chemical states of oxygen and zinc in the thin film sample were also investigated via X-ray photoelectron spectroscopy (XPS). The M-T curve could be successfully fitted using both the three-dimensional (3D) spin-wave model and Curie-Weiss law, confirming the mixed state existence of weak ferromagnetic (FM) and paramagnetic (PM) phases. Magnetic interaction was quantitatively studied and explained by polaronic percolation of bound magnetic polarons (BMPs). Analysis of magnetic symmetry of the topological antiferromagnetic as-deposited thin film using torque measurements was performed. Based on a phenomenological model, it was revealed that the structure gives rise to uniaxial magneto-crystalline anisotropy (UMA) with the magnetic easy axis parallel to the c-axis.

The Influence of Defects on the Structural, Optical, and Antibacterial Properties of Cr/Cu Co-Doped ZnO Nanoparticles

In this research, Cu/Cr codoped ZnO nanoparticles (Zn₀.₉₉₋ₓCu₀.₀₁CrxO) were prepared using the sol-gel technique. The dopant ratio was systematically varied, ranging from x = 0.01 to 0.05 in increments of 0.01. This variation allowed for an exploration of the impact of defects on the structural, microstructural, optical, and antibacterial properties of Cu/Cr-codoped ZnO nanoparticles. Structural analysis of the Zn₀.₉₉₋ₓCu₀.₀₁CrxO nanoparticles was conducted using X-ray diffraction. The findings confirmed the presence of a hexagonal wurtzite structure in the ZnCuCrO nanoparticles, as determined by the c/a ratios in the range of 1.6013 and 1.6039. The surface morphology, crystallite size, and nanoparticle shapes were determined through scanning electron microscopy. The nanoparticle elemental compositions were analyzed through electron dispersive spectroscopy. The optical characteristics of the samples were assessed using a UV spectrophotometer. The energy band gaps for the nanoparticles were computed, and we discussed how dopant elements and defects affected their optical properties. We determined the refractive index using five distinct models. Notably, the highest band gap was observed for Zn₀.₉4Cu₀.₀₁Cr₀.₀5O (Eg=3.27 eV).Positron annihilation lifetime spectroscopy was employed to investigate the defect type, defect density, and crystal quality of Cu/Cr-codoped ZnO nanoparticles. The shortest lifetime τ1 obtained the highest value (0.181 ns) for Zn0.97 Cu0.01Cr0.02O nanoparticles. Zn₀.₉₉₋ₓCu₀.₀₁CrxO NPs were assessed for their antibacterial effects on E. coli (gram-negative) and S. aureus (gram-positive). Cu/Cr codoped ZnO nanoparticles show potential as materials for optoelectronic and sensor applications due to their broad band gap (Eg > 3) and high refractive index (n > 2).

Influence of cobalt doping on structural, optical, and electrical properties of zinc oxide nanoparticles prepared by polymeric precursor method

Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR UV–Vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM/EDS), and impedance spectroscopy. The lattice parameters were determined at room temperature by Rietveld refinement, confirming single-phase composition with a hexagonal wurtzite structure. FTIR and Raman analyzes identified the characteristic vibrations of the synthesized system and the typical deformations of the wurtzite-type hexagonal structure, corroborating the results obtained from XRD. A redshift in the optical energy band gap (Egopt) was observed with increasing cobalt content compared to the ZnO sample. Considering the doping percentage, Egopt value varied between 3.13 eV and 3.04 eV for pure ZnO and Co-doped ZnO with 5 at. %., indicating that the optical properties of the nanoparticles were affected by dopant concentration. PL and SEM/EDS characterization were used to determine the associated defects for each sample and the morphology and composition of the nanoparticles. PL results showed a strong blue emission at around 439 nm (2.83 eV), which is redshift with cobalt content (ΔE between 0.05 eV and 0.01 eV), attributed to the surface defects present in the doped samples. Conductivity analysis to temperature revealed a semiconductor behavior for all samples, and their respective activation energies determined. The results provide an easy method to obtain Co-doped ZnO nanoparticles with interesting properties for optoelectronics devices.

Robust ferromagnetic V0.05-XCoxZn0.95O (x = 0.01, 0.02, 0.03, 0.04, 0.05) nano-compounds: New dilute magnetic-semiconductors with tailored optical activity

The development of diluted magnetic semiconductors (DMS) that combine magnetic properties with semiconducting behavior is a promising area of research that could lead to the creation of entirely new types of devices that are faster, more efficient, and potentially cheaper. In this investigation, DMS nanocompositions represented by V0.05-XCoxZn0.95O, (x = 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized via a modified Pechini-sol-gel process. X-ray analysis showed a successful incorporation of V and Co ions into ZnO structure. The size and shape of the nanoparticles changed depending on the V/Co doping percentage. The addition of the blend of 2 wt% V and 3 wt% Co ions significantly reduced the particle size from 21 nm to 14 nm. The X-ray photoelectron analysis identified complex interactions between vanadium/cobalt dopants and the surrounding ZnO lattice with significant influence of cobalt incorporation on vanadium's oxidation state. It further revealed a significant influence of cobalt incorporation on vanadium’s oxidation state. Vanadium primarily exists as V3+ upon vanadium-mono doping (ZV5). However, co-doping with Co/V leads to a shift towards the V5+ state. Enhanced absorption extending into the visible light region was observed in either mono or (V/Co) co-doped samples. Notably, the band gap energy decline was more pronounced in the 5 mol% Co-doped ZnO, recording a value of 2.58 eV. An additional band gap around 1.8 eV appeared in Co-doped samples, potentially due to transitions in Co2+ ions. The combination of V and Co induced a ferromagnetic behavior with fully saturated order. The ZV3C2 composition exhibits the most promising characteristics, boasting the highest saturation magnetization (1.037 emu/g). Accordingly, robust ferromagnetism of V0.05-XCoxZn0.95O, (x = 0.01, 0.02, 0.03, 0.04, 0.05) nano-particles is a promising approach for spintronic applications.

Tuning of structural, magnetic, and optical properties of ZnO nanoparticles by Co and Cu doping

Undoped, Cu, and Co-doped ZnO nanoparticles were synthesized by a simple co-precipitation method. We studied the structural, chemical, magnetic, and optical properties of synthesized nanoparticles by using X-ray Diffraction, Fourier Transform Infrared, Scanning Electron Microscopy, Vibrating-Sample Magnetometer, and UV–VIS spectroscopy. The X-ray Diffraction analysis discovers the crystalline hexagonal wurtzite structure and confirms the incorporation of Cu2+ and Co2+ in the ZnO lattice. The SEM photographs show that the nanoparticles are agglomerated, and the grain size of pure ZnO is decreased upon doping, showing inhibition of grain growth through doping. From VSM the coercivity and saturation magnetization of Co-doped (0.0189 emu/g and 84.044Oe) is higher as compared to pure and Cu-doped ZnO. The energy gap of doped and un-doped nanoparticles determined from the absorption spectrum indicates that it increases by doping of Copper and cobalt.

Bryophyllum pinnatum mediated eco-friendly synthesized porous microstructures of self-assembled Co-doped ZnO nanoparticles for methylene blue removal

Cobalt-doped ZnO nanoparticles (Co-ZnO NPs) were synthesized using a phytoextract mediated technique with varying concentrations of Co (2.5, 5.0, and 7.5 at.%), employing Bryophyllum pinnatum leaf extract as the stabilizing/capping agent. XRD analysis revealed that the synthesized Co-ZnO crystallize in a wurtzite crystalline phase with P63mc space group. FE-SEM imaging depicted the self-assembly of nanoparticles, forming porous microstructures. UV–Visible spectra analysis indicated a gradual decrease in the bandgap energy of the ZnO lattice with increasing Co concentration. Additionally, by examining the photocatalytic removal of methylene blue (MB), the photocatalytic activity of the Co-ZnO NPs was assessed. Results showed that Co-ZnO NPs with 5 % Co exhibited the highest photocatalytic activity, suggesting an optimal Co dopant concentration that minimizes the recombination of photogenerated charge carriers compared to other samples. Under sunlight exposure, Co-ZnO NPs with 5 % Co demonstrated effective photocatalytic activity, achieving the degradation of 98.08 % of a 10 mg/L MB solution within 60 min using a 1.2 g/L dosage, with a rate constant of 0.0582 min−1.

High performance Bi–Co–Mn–Si–B-doped ZnO varistors with wide ranging breakdown voltage and high resistance to electrical degradation

A simple ZnO varistor with high resistance to electrical degradation and an adjustable breakdown voltage range of 100–3000 V/mm was developed by adding SiO2 and B2O3 to Bi–Mn–Co-doped ZnO. Samples were fabricated by sintering at 1150 ºC and doped with 0–55 mol% SiO2 to adjust breakdown voltage. High nonlinear index and low leakage current density were confirmed with addition of SiO2; however, severe electrical degradation occurred. Addition of 1 mol% B2O3 successfully improved the resistance to electrical degradation and long-term reliability, due to the formation of homogenous glass-phase Bi–B–O at grain boundaries inhibiting ion migration. A stabilized interface trap with ∼0.6 eV and 10−21 (m2) was found in samples with 1 mol% B2O3.