Mixture Of ZnO Research Articles

Development of a new carbon xerogel/ZnO/BaSnO3 photocatalyst for solar and visible light photodegradation of salicylic acid

A novel carbon xerogel/ZnO/BaSnO3 photocatalyst was developed, characterized, and evaluated for the photodegradation of salicylic acid (SA) under solar and visible radiation. The development of the proposed photocatalyst involved the investigation of multiple synthesis parameters, aiming to optimize the photocatalytic activity of the ternary system. The best photocatalytic efficiency was obtained at 5 % w/w BaSnO3, 0.375 g of added tannin, and calcination temperature of 600 °C, yielding the 0.375CX/ZnO/BaSnO3 5 % 600 °C photocatalyst. After thorough characterization, it was concluded that the ternary materials are composed of a mixture of crystalline ZnO and BaSnO3 structures and carbon xerogel (CX). Additionally, the ternary materials displayed significant capacity to absorb visible radiation, mostly due to CX addition. Morphology-wise, the 0.375CX/ZnO/BaSnO3 5 % 600 °C was composed of nodular and polyhedral nanometric particles, displaying higher surface area when compared to materials without CX. Through chronoamperometry and electrochemical impedance spectroscopy, it was determined that the optimized ternary material achieved the highest photocurrent generation and lowest charge transfer resistance among the materials evaluated, indicating a superior photocatalytic activity. Photocatalytic tests demonstrated the superiority of the ternary system in the degradation of SA under solar and visible light irradiation, achieving 93 % and 52.3 % degradation after 5 h, respectively. The superior mineralization of SA (72.2 %) achieved by the optimized ternary material under solar radiation further demonstrated its increased efficacy. The suppression methodology allowed for the identification of the hydroxyl radical as the major active species in the SA degradation. A Z-type heterojunction was proposed for the ternary system, based on the staggered band alignment between ZnO and BaSnO3 and the role of CX as a solid-state mediator, possibly leading to effective charge separation and enhanced redox activity. Phytotoxicity tests showed favorable Lactuca sativa growth in SA solutions treated with 0.375CX/ZnO/BaSnO3 5 % 600 °C (especially under solar radiation), indicating reduced toxicity.

Effect of proteins as constituents of island-nanomatrix structure on vulcanization of natural rubber

Effect of proteins, constituents of the island-nanomatrix structure, on dispersion of zinc to natural rubber was investigated by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) and focused ion beam-scanning electron microscopy-energy dispersive X-ray spectroscopy (FIB-SEM-EDX). Films of natural rubber and deproteinized natural rubber (DPNR) prepared with urea were embedded in a mixture of ZnO, vulcanization accelerator and sulfur, and they were heated at 150 °C for 5 h. Migration of Zn from surface to inside of the films was observed by FIB-SEM-EDX. The Zn migrated from the surface to 14 μm for natural rubber, but not for DPNR. The optimum vulcanization time for natural rubber was short, i.e., about 4 min, whereas it was long for DPNR, i.e., about 15 min. To confirm the effect of the proteins, a latex-mixed rubber compound was prepared by mixing the latex with sulfur, ZnO and vulcanization accelerator followed by drying with a hotplate at 150 °C for 45 s since the proteins are segregated on the surface of natural rubber particles in the latex stage. Vulcanization was accelerated for the latex-mixed natural rubber compared with mechanically mixed natural rubber compound that was prepared by mixing natural rubber with ZnO, vulcanization accelerator and sulfur with a two-roll mill. The resulting latex-mixed natural rubber vulcanizate was superior in mechanical properties to the mechanically mixed natural rubber vulcanizate. It was found by rubber-state NMR spectroscopy that the difference in mechanical properties was attributed to the difference in the cis-1,4-average sequence length of the vulcanizates, which came from the difference in the dispersion of Zn.

Investigation on the blooming behavior of additives in nitrile butadiene rubber at elevated temperature

AbstractThe degradation of rubber performance in service environments is closely associated with the blooming behavior of additives in the rubber. This study investigates surface precipitates and changes in tensile properties of nitrile butadiene rubber (NBR) after storage at 85°C in air. The morphology, elemental composition, phase composition, and functional groups of the precipitates were analyzed by scanning electron microscopy, energy dispersion spectroscopy, X‐ray diffraction, and fourier transform infrared spectroscopy. Based on the morphology of internal rubber particles and precipitates and variations in the Zn/C mass ratio (ERZn), the reaction between zinc oxide and stearic acid in rubber under long‐term thermal environment was determined. Four stages of blooming for the mixture of zinc oxide and zinc stearate were inferred, and the impact of the blooming on the degradation of tensile properties of NBR was established. A dramatic decrease in the elongation at break (δk) of NBR was correlated with the blooming of zinc stearate and its correspondingly weakened plasticizing effect.Highlights The core‐shell structured mixture of ZnO and Zn(St)2 bloomed onto the surface of nitrile butadiene rubber. The ratio of mass percentages of Zn to C evaluated the blooming process of additives. The migration and blooming process of precipitates were divided into four stages. The decrease in elongation of the rubber was attributed to the blooming of Zn(St)2.

Construction of Z-scheme ZnO/g-C3N4 photocatalytic systems for degradation of dyeing wastewater

A novel heterogeneous nanocomposite photocatalyst ZnO/g-C3N4 was fabricated by secondary high-temperature calcination using g-C3N4 and ZnO as raw materials and characterized by XRD, SEM, TEM, EDS, FT-IR, Zeta potential, UV-Vis and XPS. The results displayed that the ZnO/g-C3N4 components were tightly bound, evenly distributed and significantly reduced in size, which could provide more active sites. The heterogeneous types, photocatalytic performance, degradation mechanism of ZnO/g-C3N4 for dyeing wastewater were speculated by REDOX potential, heterojunction, and quenching experiments. The degradation efficiency of ZnO/g-C3N4 on MB was much higher compared with that of single ZnO, g-C3N4 and the mechanical mixture of ZnO and g-C3N4, which can reach more than 95% at 60 min. The degradation rate was also significantly improved, with the degradation rate exceeding 50% at 20 min. The composite ZnO/g-C3N4 could degraded 90% MB after 5 cycles. The quenching experiment showed that hydroxyl (·OH) and photogenerated hole (h+) played the main role in the reaction process. It was confirmed that the prepared ZnO/g-C3N4 formed a Z-scheme photocatalytic system by examining the transfer paths of e- and h+ in various types of heterojunction and contrasting the CB and VB energy levels with the REDOX potentials of ZnO and g-C3N4. The Z-Scheme ZnO/g-C3N4 photocatalyst has the characteristics of stability, reusability, and no by-product, making it an ideal choice for environmental purification.

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Modified Cu–ZnO Catalysts Supported on the Mixture of ZnO and Zn–Al Oxide for Methanol Production via Hydrogenation of CO and CO2 Gas Mixture

Evaluation of the antibacterial activity of CuO and ZnO nanoparticles against uropathogenic Escherichia coli

E. coli responsible for urinary tract infections (UTI) became resistant to obtainable therapies. So, nanotechnology appears currently as promising innovation among various strategies under development. In the present study we evaluate the antimicrobial effects of CuO and ZnO nanoparticles against E. coli isolated from UTI. Biofilm production and expression of quorum sensing genes luxS and motA were performed on E. coli treated with the nanoparticles. luxS and motA genes were detected in the tested E. coli. All isolates produced strong, moderate and weak biofilm. All isolates had a weak biofilm formation and decreased gene expression for luxS and motA genes after treatment with CuO, ZnO and their mixture. Besides, CuO and ZnO had non-toxic effects on Human Dermal Fibroblasts and neonatal normal cells. In conclusion, the mixture of CuO and ZnO had a role in decreasing the gene expression of luxS and motA genes more than each alone.

Synthesis and characterization of zinc-titanium oxide nanoparticles blended methylcellulose derived from Albizia tree as an antibacterial natural polymer composite

This paper seeks to synthesize antibacterial green polymeric composites utilizing extracted cellulose, a natural polymer sourced from biomass. The cellulose was obtained from local agricultural waste. Subsequently, the polymeric composites were synthesized, incorporating blends of nano zinc oxide and nano titanium dioxide in varying proportions. All synthesized samples undergo comprehensive characterization and examination through a range of tests encompassing structural and thermal testes. Furthermore, the antibacterial activity of the samples was assessed using the disc diffusion method, enabling the identification of the most effective formulations. The ultimate selection of the optimal composite was based on the collective outcomes of all tests, facilitating its potential utilization across diverse applications. In conclusion, the Albizia tree demonstrates a notable potential for efficient cellulose extraction, making it a viable candidate for such purposes. The cellulose extracted from Albizia tree holds the capability to yield methylcellulose. The bacterial activity assessment of Nano materials highlighted a distinct efficacy in the case of the 75% Nano TiO2 and 25% Nano ZnO mixture. However, it is worth noting that an excessive increment in Nano ZnO content exhibited adverse effects. Thorough thermal analyses verified the thermal stability of methylcellulose.

Optimizing the structural and photocatalytic performance of Ag‐decorated ZnO/Zn(OH)2 nanoparticles for RhB degradation

AbstractIn this study, as‐prepared and Ag‐decorated ZnO/Zn(OH)2 composite nanoparticles (NPs) were obtained using the sol–gel technique. First, the effect of aging on the structural, optical, and morphological features was examined. Ag NPs can interact with the electronic structure of ZnO/Zn(OH)2 NPs, resulting in changes in their energy levels. It was found that the composite NPs obtained after 6 h solution aging increased in full width at half maximum and good crystallinity of the structures from the X‐ray diffraction (XRD) measurements. The Raman spectrum supports the experimental data obtained from XRD and Fourier transform infrared, a material containing a mixture of ZnO and Zn(OH)2. From the morphological study, Ag NPs were successfully decorated on the ZnO/Zn(OH)2 surface, and composite NPs did not change the morphological appearance of the structure. Second, the photocatalytic performance of the samples was investigated. In the experimental setting, ultra‐violet A light was employed as the irradiation source, whereas rhodamine B (RhB) was used as the dyestuff. The photo‐degradation of the RhB dyestuff on composite NPs was observed to be 98.5% and 92.5% for 6 and 2 h aged samples, respectively. On Ag NPs, the catalytic performance of the sample was increased up to 95% after 180 min.

Effect of long-term exposure of mixture of ZnO and CuO nanoparticles on Scenedesmus obliquus.

The present study investigated the possible toxic effect of ZnO and CuO nanoparticles (NPs) on freshwater microalgae, Scenedesmus obliquus at environmentally- relevant nanoparticle concentration (1 mg/L) and high concentration (10 mg/L) in BG-11 medium under white light LED-illumination over 35 days. The effect of time on the stability of media, nanoparticles, and their relation to toxicity to algae was also studied. The transmission electron microscopy indicated structural damage to algae due to the presence of a mixture of nanoparticles (at 10 mg/L). FTIR (Fourier Transform infrared) analysis of a sample containing a mixture of nanoparticles showed an addition of bonds and a difference in the peak location and its intensity values. The inhibition time for biomass was observed between 14 days and 21 days at 10 mg/L NPs. At 1 mg/L, the order of toxicity of NPs to algae was found to be: CuO NPs (highest toxicity) > ZnO NPs>ZnO + CuO NPs (least toxicity). During exposure of algae cells to a mixture of NPs at 10 mg/L NP concentration, a smaller value of metal deposition was observed than that during exposure to individual NPs. Antagonistic toxic effects of two NPs on dry cell weight of algae was observed at both concentration levels. Future work is needed to understand the steps involved in toxicity due to mixture of NPs to algae so that environmental exposures of algae to NPs can be managed and minimized.

Sintering mechanism and electrical conductivity of ZnO added BaCe0.8Zr0.1Y0.1O3-δ proton conducting perovskites

The sintering mechanism and electrical conductivity of ZnO added BaCe0.8Zr0.1Y0.1O3-δ (BCZY) proton conducting perovskites were investigated. The additions of 0.1 to 3 wt% ZnO to BCZY promoted the sintering of the BCZY pellet samples, and the samples with ZnO showed impermeable bodies with relative densities ≥90% after firing at 1400 °C for 6 h. First-principles calculations suggest that Ba in BaZnO2 is more stable than in perovskites, and Zn is hardly soluble in BCZY. These theoretical results indicate that ZnO reacts with Ba in the BCZY perovskites. The melting points of the BaO and ZnO mixtures were approximately 1100 °C. Because their liquid phase should react with excess Y component in the perovskite, the liquid phase containing Y component enhances the densification of the doped perovskite by the liquid phase sintering. The electrical conductivities of BCZY perovskites with ZnO content ranging between 0.1 wt% and 3 wt% varied from 1.3 × 10−2 to 1.5 × 10−2 S/cm at 600 °C in an atmosphere of 3.0% H2O, 19.4% H2 and 77.6% N2. The electrical conductivities of BCZY perovskites with ZnO were comparable to those of the dense BCZY perovskite without ZnO. The present result suggests that addition of a small amount of ZnO is appropriate for enhancing the sintering and retaining the high electrical conductivity of BCZY.

Introducing Mn into ZIF-8 nanozyme for enhancing its catalytic activities and adding specific recognizer for detection of organophosphorus pesticides.

In order to design and establish a highly efficient and selective nanozyme-based sensing platform for the UV-vis detection of organophosphorus pesticides (OPs), Mn was introduced into ZIF-8 nanozyme for enhancing its catalytic activities and adding specific recognizer. The Mn-doped ZIF-8 (Mn-ZIF-8) nanocomposites were synthesized with a very facile one-pot method by heating the mixture of ZnO, 2-methylimidazole (Hmin) and Mn(CH3COO)2·4H2O in a solvent-free system at 180°C for 8h. The Mn-ZIF-8 nanocomposite showed a higher peroxidase activity and an additional thiocholine (TCh)-degradable property compared to the pristine ZIF-8. OPs could inhibit acetylcholinesterase (AChE) to catalyze the hydrolysis of acetylthiocholine (ATCh) to produce TCh, thus blocking the degradation of Mn-ZIF-8 and protecting the catalysis of the oxidation of colorless 3,3',5,5'-tetramethylbenzydine (TMB) to blue oxidized TMB (ox-TMB). Accordingly, a detection method for OPs with high sensitivity and selectivity was designed and established on the basis of the Mn-ZIF-8 nanozyme with a linear range of 0.1-20nM and a limit of detection (LOD) as low as 54pM.

An exploration of the physical, optical, mechanical, and radiation shielding properties of PbO–MgO–ZnO–B2O3 glasses

Abstract This study presents the results of an investigation into the physical, optical, and mechanical characteristics of glasses prepared from a mixture of ZnO, MgO, B2O3, and PbO. It was found that increasing the concentration of PbO in the glasses led to an increase in both the density (ρ) and molar mass (M). The addition of PbO also affected the packing arrangement of oxygen atoms in the glass network, resulting in changes to the oxygen molar volume (V o) and oxygen packing density. Furthermore, the investigation found that the optical basicity (Ʌ th) of the glass elevated with increasing PbO concentration. Finally, the behavior of the average electronegativity (χav) and electronic polarizability ( α o − 2 {\alpha }_{{\rm{o}}}^{-2} ) with respect to the concentration of PbO in the glasses is discussed, whereby the addition of PbO affected the glasses’ mechanical characteristics as follows: (i) the addition of PbO increased the complexity of the glass network by enhancing the average cross-link density ( n c ̅ \bar{{n}_{{\rm{c}}}} ) and the number of bonds per unit volume of the glasses (n b); (ii) the glasses’ Young’s modulus (E), bulk modulus (B), and shear modulus (G) declined as the mol percent of the PbO increased; (iii) the longitudinal modulus (L) reduced but remained greater than G; (iv) the glass network cross-linking reduced the Poisson ratio (σ); (v) the glasses’ fractal bond connectivity (d) values indicated a three-dimensional network; and (vi) lead oxide hardened the glass, suggesting that a stronger structure manifests. These findings collectively demonstrate that PbO improves the rigidity and interconnectivity of glass. The gamma radiation-shielding characteristics of the glasses were evaluated using the Phy-X software in the 0.015–15 MeV energy range. The radiation-shielding properties of the studied glasses can be compared with other materials by introducing a new parameter known as the radiation coefficient ratio (R). It is observed that Q4 glass sample had superior shielding performance.

Mechanical, gamma rays and neutron radiation transmission properties for some ZnO–TeO2–P2O5-ZnX glasses

Oxyhalide glasses are utilized in the process of immobilizing nuclear waste and function as scintillating agents for the purpose of radiation detection. The objective of this study is to examine the enhanced mechanical and radiation attenuation characteristics of newly developed oxyhalide glasses by incorporating zinc-iodide. This study investigates the synthesis process, mechanical properties, and experimental gamma-neutron radiation transmission properties. A halogen-free base glass, consisting of an oxide mixture of P2O5, TeO2, and ZnO, was synthesized. Following that, the initial glass composition was further strengthened by the addition of zinc bromide (ZnBr2), zinc chloride (ZnCl2), zinc fluoride (ZnF2), and zinc iodide (ZnI2) in a successive manner. The experimental configuration entailed positioning circular glass samples between a 133Ba radioisotope and a Canberra High Purity Germanium (HPGe) detector. The determination of attenuation coefficients is achieved through the measurement of individual attenuation properties. Afterwards, theoretical approaches are utilized to determine the mechanical characteristics of halogenated glasses, including Young's modulus (Y), Bulk modulus (K), Shear modulus (G), Longitudinal modulus (L), and Poisson's modulus (v). The results of the study suggest that the implementation of the halogenation process on the P2O5–TeO2–ZnO base composition led to a significant enhancement in the examined properties. The incorporation of zinc-iodide in the halogenation process resulted in a significant improvement in the gamma absorption properties. The utilization of zinc in the halogenation process demonstrates multifunctional capabilities, which involve the potential to enhance various glass properties, including durability and gamma-ray absorption properties. It can be concluded that zinc-iodide demonstrates enhanced halogenation capabilities in comparison to zinc bromide, zinc chloride, and zinc fluoride.

The effect of non-equimolar doping on the preparation and electrical conductivity of Sr(Ti,Zr,Zn,Sn,Hf)O3-σ high entropy perovskite oxide

A series of high entropy oxides (HEOSs) with non-isomolar ratios of perovskite structures were prepared by ball milling a mixture of SrO, TiO2, ZrO2, ZnO, SnO2 and HfO2 followed by sintering using a high-temperature solid-phase method. Both XRD and TG-DSC results indicate that single-phase Sr(Ti0.2Zr0.2Zn0.2Sn0.2Hf0.2)O3-σ is formed at 1500 °C. According to the SEM-EDS pictures, the elements in the oxide are uniformly distributed with no significant segregation or accumulation. The TEM results show that the polycrystalline ceramic powders can be classified as orthogonal Pbnm perovskite structure. The electrical conductivity (σ) was measured by the EIS technique and the activation energy (Ea) of HEOSs is calculated. In the temperature range of 300–750 °C, Sr(Ti0.28Zr0.18Zn0.18 Sn0.18 Hf0.18)O3-σ exhibits the highest conductivity (2.41 × 10−3 S/cm) and the lowest activation energy (Ea = 0.57 eV) due to lattice distortion and oxygen vacancy concentration.

Fabrication of Glutaraldehyde Vapor Treated PVA/SA/GO/ZnO Electrospun Nanofibers with High Liquid Absorbability for Antimicrobial of Staphylococcus aureus.

In this study, we aim to develop organic-inorganic hybrid nanofibers containing high moisture retention and good mechanical performance as an antimicrobial dressing platform. The main theme of this work focuses on several technical tasks including (a) the electrospinning process (ESP) to produce organic polyvinyl alcohol/sodium alginate (PVA/SA) nanofibers with an excellent diameter uniformity and fibrous orientation, (b) the fabrication of inorganic nanoparticles (NPs) as graphene oxide (GO) and ZnO NPs to be added to PVA/SA nanofibers for enhancement of the mechanical properties and an antibacterial function to Staphylococcus aureus (S. aureus), and then (c) the crosslinking process for PVA/SA/GO/ZnO hybrid nanofibers in glutaraldehyde (GA) vapor atmosphere to improve the hydrophilicity and moisture absorption of specimens. Our results clearly indicate that the uniformity nanofiber with 7 wt% PVA and 2 wt% SA condition demonstrates 199 ± 22 nm in diameter using an electrospinning precursor solution of 355 cP in viscosity by the ESP process. Moreover, the mechanical strength of nanofibers was enhanced by 17% after the handling of a 0.5 wt% GO nanoparticles addition. Significantly, the morphology and size of ZnO NPs can be affected by NaOH concentration, where 1 M NaOH was used in the synthesis of 23 nm ZnO NPs corresponding to effective inhibition of S. aureus strains. The PVA/SA/GO/ZnO mixture successfully performed an antibacterial ability with an 8 mm inhibition zone in S. aureus strains. Furthermore, the GA vapor as a crosslinking agent acting on PVA/SA/GO/ZnO nanofiber provided both swelling behavior and structural stability performance. The swelling ratio increased up to 1.406%, and the mechanical strength was 1.87 MPa after 48 h of GA vapor treatment. Finally, we successfully synthesized the hybrid nanofibers of GA-treated PVA/SA/GO/ZnO accompanied with high moisturizing, biocompatibility, and great mechanical properties, which will be a novel multi-functional candidate for wound dressing composites for patients receiving surgical operations and first aid treatments.

Sustainable and energy-efficient photocatalytic degradation of textile dye assisted by ecofriendly synthesized silver nanoparticles

In this study, we have touched on two goals of sustainable development, namely, the provision of clean water and sanitation and clean energy at acceptable prices, hoping for good health for all ages. A green economical method was used to prepare silver nanoparticles from chitosan biopolymer. AgNPs were fully characterized using UV–Vis, FTIR, XRD, HR-TEM, and EDX analysis. Different concentrations (0.02–0.18 g/L) of the nanoparticles were integrated into a mixture of heterogeneous nano photocatalysts TiO2 and ZnO (1:1 weight ratio) under UV irradiation for the photocatalytic degradation of Acid Red 37 textile dye to obtain clean water. The kinetic description of the performed photocatalytic process was presented assuming a pseudo-first-order reaction. The data revealed that increasing the concentration of AgNPs in the catalytic mixture showed a high apparent rate constant (kapp) accompanied by an increase in the apparent quantum yield (%Qapp), followed by dye destruction after a very short time (t0.5 = 3 min). Since the photocatalytic degradation process consumes electrical energy, the electrical energy per order (EE/O) was calculated, showing a low value of 20 kWh/m3/order, using 0.18 g/L AgNPs, indicating that the elicited photocatalytic degradation method is a sustainable one for the mineralization of the targeted dye.

Characterization and Growth of TiO2/ZnO on PTFE Substrates at Different Volumetric Ratios Using Chemical Bath Deposition

Developing non-toxic, semiconductor-doped heterojunction materials for optoelectronic applications on the surface of a flexible substrate is a viable strategy for meeting the world’s energy needs without introducing any environmental issues. In this paper, Ti:TiO2/ZnO nanocomposites were prepared by heat treatment and utilized as an active layer in UV photodetectors. First, a ZnO seed layer was deposited by radio frequency (RF) sputtering on polytetrafluoroethylene (PTFE) substrates. Then, TiO2/ZnO thin films (TFs) were successfully grown by combining volumetric mixtures of TiO2 and ZnO at the ratios of 1:7, 1:3, 3:5, and 1:1 via the chemical bath deposition (CBD) method. The morphological, elemental, and topographical analyses of the grown TFs were investigated through SESEM, EDX, and AFM spectroscopy, respectively. XRD patterns illustrated the presence of the unified (002) peak of the Ti/ZnO hexagonal wurtzite structure in all prepared samples, with intensities indicating a very strong preferential crystallinity with increasing TiO2 ratios. Enhanced diffuse reflectance curves were obtained by UV–Vis spectroscopy, with allowed indirect energy bandgaps ranging from 3.17 eV to 3.23 eV. FTIR characterization revealed wider phonon vibration ranges indicating the presence of Ti–O and Zn–O bonds. Metal–semiconductor–metal (MSM) UV photodetectors were fabricated by thermally evaporating Ag electrodes on the grown nanocomposites. The volumetric ratio of TiO2/ZnO impacted the photodetector performance, where the responsivity, photosensitivity, gain, detectivity, rise time, and decay time of 0.495 AW−1, 247.14%, 3.47, 3.68 × 108 jones, 0.63 s, and 0.99 s, respectively, were recorded at a ratio of 1:1 (TiO2:ZnO). Based on the results, the heterostructure nanocomposites grown on PTFE substrates are believed to be highly promising TF for flexible electronics.

Conductivity features of ZnO and NiO nanofiber composites

In this work, composites of ZnO and NiO nanofibers with n- and p-type conductivity, respectively, were studied. It is shown that the conductivity of the studied composites strongly depends on the arrangement of ZnO and NiO nanofibers. In the case of a mixture of ZnO and NiO nanofibers (with their random arrangement relative to each other and electrical contacts), conduction can occur only along ZnO fibers, which have a higher conductivity compared to NiO. However, the presence of the ZnO/NiO p-n heterojunction leads to the formation of depleted regions in ZnO, as a result, the conductivity of the mixture becomes several orders of magnitude lower than the conductivity of ZnO nanofibers. In the case of a two-layer composite, in which one layer consists of NiO nanofibers and the other layer consists of ZnO nanofibers, charge carriers move through the p-n NiO/ZnO heterojunction, which leads to a rectifying current-voltage characteristic and opens up broad prospects for the use of such systems in electronic devices. Keywords: metal oxides, zinc oxide, nickel oxide, heterostructures, conductivity.

Особенности проводимости композитов нановолокон ZnO и NiO

In this work, composites of ZnO and NiO nanofibers with n- and p-type conductivity, respectively, were studied. It is shown that the conductivity of the studied composites strongly depends on the arrangement of ZnO and NiO nanofibers. In the case of a mixture of ZnO and NiO nanofibers (with their random arrangement relative to each other and electrical contacts), conduction can occur only along ZnO fibers, which have a higher conductivity compared to NiO. However, the presence of the ZnO/NiO p-n heterojunction leads to the formation of depleted regions in ZnO, as a result, the conductivity of the mixture becomes several orders of magnitude lower than the conductivity of ZnO nanofibers. In the case of a two-layer composite, in which one layer consists of NiO nanofibers and the other layer consists of ZnO nanofibers, charge carriers move through the p-n NiO/ZnO heterojunction, which leads to a rectifying current-voltage characteristic and opens up broad prospects for the use of such systems in electronic devices.

Facile synthesis of uniformly coated ZnO@Bi2O3 composites anode for long-cycle-life zinc–nickel battery

Zinc–nickel battery attracts much attention because of their excellent rate performance and high operating voltage. However, their applications are strongly restricted by the poor cycling performance, which is caused by the degradation of the zinc anode during battery cycling. To overcome such limitation, a facile strategy to prepare homogeneously Bi2O3 coated ZnO composites is proposed. The reaction is conducted in the liquid phase based on redox reaction of Bi3+ and I− to directly grow BiOI on commercial ZnO powders, which are then converted to ZnO@Bi2O3 by further heat treatment. Benefiting from the uniform Bi2O3 coating, the solubility of ZnO is effectively reduced. The well-connected metallic Bi network is formed, which serves as the conductive substrate for uniform zinc deposition and hence inhibits the dendrites growth. The assembled zinc–nickel battery based on ZnO@Bi2O3 composites exhibits significantly prolonged cycling life. Even under a high discharge current of 10 A (~ 138 mA cm−2), the battery can keep cycling during 400 cycles with discharge voltage higher than 1.1 V, which is extended by 3 and 1.7 times compared with that of electrodes based on pure ZnO and physical mixture of Bi2O3 and ZnO. This work provides a facile strategy for synthesizing uniformly Bi2O3 coated ZnO composites, which is helpful for large-scale synthesis of high-performance zinc anodes in practical application.