ZnO Powders Research Articles

Thermal conductivity suppression in ZnO with AlZn2O4and ZnP2for thermoelectric applications.

In this study, intrinsic ZnO powder was sintered and intercalated with particles. The resulting powder, along with a commercial p-type product, was consolidated into bulk materials, and their thermal conductivity was measured across a temperature range of 350 K to 700 K. The thermal conductivity of the commercial p-type ZnO was found to be lower than that of intrinsic ZnO, attributed to controlled doping. Notably, our demonstration illustrated that the thermal conductivity can be reduced by a factor of 5-10 in the presence of AlZn2O4 and ZnP2 precipitates. This methodology presents a feasible approach for the future design of ZnO-based thermoelectric materials, particularly for thermal heat scavenging applications.&#xD.

Nano-reusable CuO-ZnO Catalyzed One-Pot Synthesis of 1-Amidoalkyl-2-Naphthols under Green Condition

Introduction: The Developed CuO-ZnO nanocomposite has been demonstrated as a new and environmentally friendly catalyst for one-pot multicomponent reaction between aldehydes, 2- naphthol and amides in the synthesis of 1-amidoalkyl-2-naphthols. Method: The new catalyst was synthesized by a ball-milling method by mixing a mixture of CuO and ZnO powder in various proportions and characterized by different spectroscopic methods such as powder X-ray diffraction (pXRD), Scanning Electron Microscopy (SEM), UV-Visible analysis, EDAX elemental analysis and mapping. The advantages of the devised protocol include a green approach, simple work-up procedures, avoidance of hazardous solvents, and good to excellent yields. RE Sult: Evaluation of the catalyst performance in the synthesis of some 1-amidoalkyl-2-naphthols showed presentable results. Sixteen derivatives were synthesized in desirable yield by our new method (4a-4p). CuO-ZnO nanocomposite as a safe and efficient catalyst could be reused up to 5 runs for the synthesis of naphthol derivatives without any significant decrease in its potency. Conclusion: The High purity of the products and desirable yields are other points that make the present work more attractive.

Effect of Electron Irradiation on the Optical Properties of Zinc Oxide Powder Modified by Magnesium Oxide Nanoparticles

The effect of modifying ZnO powders with MgO nanoparticles (with a concentration of 0.1–10 wt. %) on their diffuse reflectance spectra in the region of 0.2–2.5 μm before and after irradiation with 30 keV electrons was studied. Modification of ZnO powder was carried out by MgO nanopowder with concentrations from 0.1 to 10 wt. % using a solid-state method at 650°C heating temperature. X-ray diffraction analysis showed that this method of modification there is no formation of additional phases. It has been established that zinc oxide structure symmetry belongs to the P63mc space group, magnesium oxide – to the Fm–3m space group. The spectral reflectance of such powders in the visible region is over 90%. Under irradiating by 30 keV electrons of initial and modified ZnO powders, as well as MgO nanopowder, a decrease in their reflectance recorded in the entire studied region of the spectrum. It has been established that modification with MgO nanoparticles at a concentration of 3 wt. % leads to an increase in radiation resistance by a factor of 1.32 compared to unmodified samples. This effect is determined by the sink of radiation defects on the large specific surface area of nanoparticles.

Enhanced Tribodegradation of a Tetracycline Antibiotic by Rare-Earth-Modified Zinc Oxide.

Tribocatalysis is an emerging advanced oxidation process that utilizes the triboelectric effect, based on friction between dissimilar materials to produce charges that can initiate various catalytic reactions. In this study, pure and rare-earth-modified ZnO powders (La2O3, Eu2O3, 2 mol %) were demonstrated as efficient tribocatalysts for the removal of the tetracycline antibiotic doxycycline (DC). While the pure ZnO samples achieved 49% DC removal within 24 h at a stirring rate of 100 rpm, the addition of Eu2O3 increased the removal efficiency to 67%, and La2O3-modified ZnO powder exhibited the highest removal efficiency, reaching 80% at the same stirring rate. Additionally, increasing the stirring rate to 300 and 500 rpm led to 100% DC removal in the ZnO/La case within 18 h, with the pronounced effect of the stirring rate confirming the tribocatalytic effect. All tribocatalysts exhibited excellent recycling properties, with less than a 3% loss of activity over three cycles. Furthermore, a scavenger assay confirmed the importance of superoxide radical generation for the overall reaction rate. The results of this investigation indicate that the rare-earth-modified ZnO tribocatalysts can effectively utilize mechanical energy to decompose pollutants in contaminated water.

Characterization of ZnWO4, MgWO4, and CaWO4 Ceramics Synthesized in the Field of a Powerful Radiation Flux

This paper presents the results of a study on the morphology, structure, and luminescent properties of ceramics synthesized in the radiation field of MeWO4 compositions (where Me is Mg, Ca, and Zn). The synthesis of ceramics was carried out by the direct action of the electron flux on an initial mixture of powders of the given stoichiometric composition. WO3, ZnO, MgO, and CaO powders with particle sizes in the range of 1–50 microns were used for the synthesis of the samples. It was found that the yield of the radiation synthesis reaction (the ratio of the mass of the sample and the charge used), when treated with an electron flux with an energy of 1.4 MeV and a flux power density of 15–18 kW/cm2, was in the range of 75–99%. The synthesis of all compositions was carried out under the same radiation treatment modes, although the melting temperatures of the starting materials varied significantly and ranged from 1473 °C (WO3) to 2825 °C (MgO). The study of the ceramic structure showed that under the radiation effect of powerful radiation fluxes on the charge, a crystalline phase of the appropriate composition formed, regardless of the synthesis modes. The results of XRD studies show that during the radiation treatment of the charge, ceramics are formed mainly with the crystalline phases ZnWO4, MgWO4, and CaWO4. These resulting MeWO4 ceramics can be used for the same purposes as crystals. Photoluminescence (PL) and cathodoluminescence (CL) were studied under excitation using stationary ultraviolet radiation and nanosecond pulses of electron flux. In general, the PL and CL of synthesized ceramic samples ZnWO4, MgWO4, and CaWO4 showed that their luminescent properties are similar to those of luminescence in corresponding crystalline materials. This indicates the formation of a crystalline phase in synthesized ceramic samples.

Insights for Precursors Influence on the Solar-Assisted Photocatalysis of Greenly Synthesizing Zinc Oxide NPs towards Fast and Durable Wastewater Detoxification

Herein, this study has examined the influence of Zn2+ sources during a biogenic-mediated pathway to synthesize ZnO nanoparticles with highly desirable solar-responsive catalytic properties. Salts of nitrate, acetate and chloride have been utilized. The ZnO powders underwent characterization using diverse analytical tools, including XRD, FTIR, Raman, BET, SEM, TEM with EDS/elemental mapping and UV-vis absorption/emission spectroscopic analyses. Accordingly, precursors have proved to affect crystallinity, morphology, surface characteristics, optical properties and the photocatalytic degradation of methylene blue (MB) model pollutant. It was observed that ZnO derived from zinc acetate precursor (Z-AC NPs) exhibits very fast photocatalytic degradation of MB at pH 11 with superior kinetic estimates of 0.314 min−1 and t1/2 = 2.2 min over many of recent reports. In contrast, the chloride precursor is not recommended along with the employed biogenic route. The intriguing findings could be directly correlated to the decreased crystal size, augmented surface area, the hexagonal morphology of the crystals, high potency in absorbing visible photons, high efficacy in separating photogenerated charge carriers and producing high amounts of •OH radicals. Further testing of Z-AC NPs in photocatalytic remediation of water samples from Dumat Aljandal Lake in Aljouf, Saudi Arabia, contaminated with MB and pyronine Y (PY) dyestuffs, showed high dye photodegradation. Therefore, this work could lead to an extremely fast avenue for decontaminating wastewater from hazmat dyestuff.

Treatment of Paracetamol in Water with Different Salinities over Powder and Supported TiO2 and ZnO Photocatalysts

ABSTRACT. Paracetamol's (PCT) Paracetamol's (PCT) presence in water bodies poses a risk to both aquatic life and humans. This study aims to examine the effect of salinities on PCT removal in water using powder and supported photocatalysts. ZnO powder is a superior photocatalyst to TiO2, where the rate constant can be 18 times higher. Salinity boosted the PCT removal up to 2.7 times for TiO2 at lower concentrations but decreased the PCT removal for TiO2 and ZnO at higher values. Immobilizing the powder photocatalysts on a nonwoven polyester support (NPS) dropped the photocatalytic activity, especially for ZnO, whose performance was 36 times lower than its powder counterpart. The passivation of the photocatalysts by the silica binder necessary for attaching the photocatalyst to the support can be linked to the decline in the performance of TiO2 and ZnO composites. The silica and TiO2 formed homogeneous layers on the NPS, unlike the silica and ZnO layers. High salinity reduced the performance of TiO2 composites by 20 times but showed no significant effect on ZnO composites. The performance of the ZnO composite was further reduced when real seawater was used as feed. Keywords: Titanium dioxide, zinc oxide, polyester, paracetamol, salinity.

Study of the electronic transport performance of ZnO-SiO2 film: the construction of grain boundary barrier

Purpose The purpose of this study is to adjust the electronic transport performance of zinc oxide–silicon dioxide (ZnO-SiO2) film by the construction of a grain boundary barrier. Design/methodology/approach ZnO-SiO2 thin films were prepared on glass substrates by a simple sol-gel method. The crystal structure of ZnO and ZnO-SiO2 powders were tested by X-ray diffraction with copper (Cu) Kα radiation. The absorption spectra of ZnO and ZnO-SiO2 films were recorded by a ultraviolet-visible spectrophotometer. The micro electrical transport performance of ZnO-SiO2 thin films were investigated by conductive atomic force microscope and electrostatic force microscope. Findings The results show that the current of ZnO-SiO2 film decrease, indicating that the mobility of ZnO-SiO2 film is greatly decreased, owing to the formation of the grain boundary barrier between ZnO and SiO2. The phase variation of ZnO-SiO2 film increases due to the electron accumulation at grain boundaries. Originality/value ZnO and ZnO-5SiO2 thin films prepared on glass substrates by a simple sol-gel method were first studied by CAFM and EFM. The band gaps of ZnO and ZnO-5SiO2 is ∼3.05 eV and 3.15 eV, respectively. The barrier height of ZnO-5SiO2 film increased by ∼0.015 eV after introducing SiO2. The phase variation intensity increased to a certain extent after doping SiO2, due to the increased GB barrier. ZnO-5SiO2 film will be a promising ETL candidate in the application of QLEDs field.

Conformal zinc sulfide coating of vertically aligned ZnO nanorods by two-step hydrothermal synthesis on wide bandgap seed layers for lead-free perovskite solar cells

Vertically aligned ZnO nanorods (NRs) were grown hydrothermally on the wide bandgap (∼3.86 – 4.04 eV) seed layers (SLs) of grain size ∼162 ± 35 nm, prepared using ball-milled derived ZnO powder. The synthesized ZnO NRs were further decorated with ZnS nanocrystals to achieve a ZnO NR-ZnS core–shell (CS)-like nano-scaffolds by a subsequent hydrothermal synthesis at 70 °C for 1 h. UV-Vis-NIR spectroscopy, x-ray diffractometry (XRD), Raman spectroscopy and Field emission scanning electron microscopy (FESEM) coupled with Energy dispersive x-ray spectroscopy (EDX) analyses confirmed the formation of ZnS atop the vertically aligned ZnO NR arrays of ∼1.79 ± 0.17 µm length and ∼165 ± 27 nm diameter. Transmission electron microscopy (TEM)/EDX analyses revealed that vertically aligned ZnO NRs (core dia. ∼181 ± 12 nm) arrays are conformally coated by an ultrathin ZnS (∼25 ± 7 nm) shell layer with a preferential ZnS{111}/ZnO{10-10}-like partial epitaxy. The ZnO NRs exhibited a sharp band edge near ∼384 nm having optical bandgap energy (E g) of ∼3.23 eV. However, the ZnO NR-ZnS CS exhibited double absorption bands at E g ∼ 3.20 eV (ZnO-core) and E g ∼ 3.78 eV (ZnS-shell). The ZnS{111}/ZnO{10-10}-nano-scaffolds could be utilized to facilitate the enhanced absorption of UV photons as well as the radial junction formation between the Pb-free perovskite absorber and ZnS/ZnO NRs layers.

Facile fabrication of superhydrophobic ZnO powders coated on polyurethane sponge for effective oil/water separation application

Oil spills pose significant challenges to the environment, wildlife, and local economies, thus an effective method for cleaning up an oil spill is urgent. Here, superhydrophobic ZnO powder particles were synthesized using a simple and efficient method and investigated their coating on polyurethane sponge for oil/water separation application. Initially, ZnO particles were prepared through a hydrothermal reaction of Zn(CH3COO)2 and NaOH solution in an autoclave. Subsequently, superhydrophobic ZnO particles were obtained through hydrophobic modification using either stearic acid or 1H, 1H, 2H, 2H-Perfluorooctyltriethoxysilane. The results demonstrate that the ZnO particles exhibited excellent superhydrophobic properties, with contact angle of 153o. After coating superhydrophobic ZnO particles on the polyurethane sponge, the surface became superhydrophobic/oleophilic and could adsorb oil with a capacity measured up to more than 40 times its own weight. Results demonstrate the promising application of superhydrophobic/oleophilic polyurethane sponge for oil/water separation.

Preparation of ZnO Thick Films Activated with UV-LED for Efficient H2S Gas Sensing

In this work, ZnO thick films were synthesized via two simple and easy methods, mechanochemical synthesis and screen-printing deposition. The ZnO powders were obtained through milling at low temperature with milling times of 20, 40, and 60 min. The ZnO thick films were fabricated by depositing 10 cycles of ZnO inks onto glass substrates. The characterization of ZnO thick films revealed a thickness ranging from 4.9 to 5.4 µm with a surface roughness between 85 and 88 nm. The structural analysis confirmed a hexagonal wurtzite crystalline structure of ZnO, both in powders and in thick films, with a preferred orientation on the (002) and (101) planes. Nanostructures with sizes ranging from 36 to 46 nm were observed, exhibiting irregular agglomerated shapes, with an energy band found between 2.77 and 3.02 eV. A static experimental set up was fabricated for gas sensing tests with continuous UV-LED illumination. The ZnO thick films, well adhered to the glass substrate, demonstrated high sensitivity and selectivity to H2S gas under continuous UV-LED illumination at low operating temperatures ranging from 35 to 80 °C. The sensitivity was directly proportional, ranging from 3.93% to 22.40%, when detecting H2S gas concentrations from 25 to 600 ppm.

Li/La and Cu modified ZnO semiconductor: Highly boosted of dielectric and sunlight-treatment of thiamethoxam and brilliant green contaminants

Solving the global environmental problem which related to the dissolved organic pollutants into water systems is an essential issue for human-health and aquatic life. This study represents the simple synthesis of new Li/La and Cu modified ZnO compositions as active photocatalysts and proper dielectric materials for electrical energy storage devices. The synthesized powders have one phase nature with hexagonal lattice indexed to ZnO structure. The field emission scanning electron microscopy (FESEM) clearly showed that (Li, La) modified ZnO powder consist of a mixture of particles having open hexagonal tube and spherical shapes. The FESEM picture of (Li, Cu, La) modified ZnO powder revealed lumps like cabbage shape mainly composed of pieces like sheets or papers. The purity and elemental composition were also verified by energy dispersive spectroscopy (EDS) analysis. The addition of (Li, La) and (Li, Cu, La) ions to ZnO semiconductor extremely improved the dielectric constant which is a benefit for application in solid state energy storage systems. (Li, Cu, La) modified ZnO sample is a suitable catalyst for removal of organic waste owing to its high response to visible light spectrum with measured band gap energy of 2.76 eV. The synergistic effect of Li+, Cu2+ and La3+ dopants induced high visible light photodegradation activities against thiamethoxam pesticide and brilliant green dye with measured efficiencies of 92 and 96 % after reaction time of 50 min, respectively. The high stability and mineralization properties of (Li, Cu, La) modified ZnO catalyst leads to the conclusion that this composition has a potential use in wastewater treatment.

ZnO powders synthesized via sol–gel combustion method: Influence of the solvent on physical properties and antibacterial activity

ZnO powders were synthesized using the sol–gel combustion method, and their properties, along with their activity against microorganisms isolated in the oral cavity, were investigated based on the solvent used in the synthesis. Characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, and photoluminescence (PL) spectroscopies. The results revealed the synthesis of pure ZnO powders without secondary phases, albeit forming microaggregates. Changes in the density of point defects were suggested based on PL results. Despite their size, all the powders exhibited significant antibacterial activity against Streptococcus mutans and Staphylococcus epidermidis.

Magnetic zinc oxide/silica microbeads for the photocatalytic degradation of azo dyes

Photocatalysis is a promising technique for the complete degradation of azo dyes that are present in wastewater. In this work, a new photocatalyst in the form of ZnO/Fe3O4/SiO2 hybrid microbeads was fabricated for the photocatalytic degradation of methylene blue. The microbeads were synthesised through self-assembly and subsequent agglomeration of nanoparticles within an aqueous phase of a water-in-oil emulsion template. Photocatalytic degradation experiments were conducted through exposure of a methylene blue solution to UV light. The hybrid microbeads performed better than ZnO powder at the same initial dye and ZnO concentration because of higher adsorption and degradation. The initial concentration of dye solution and catalyst dosage have a significant impact on the degradation. Higher degradation is seen with lower initial dye concentration and higher catalyst dosage. The presence of magnetic nanoparticles within the beads allows for their full recovery and reuse for degradation experiments. Complete degradation of dye was achieved using the new ZnO/Fe3O4/SiO2 microbeads.

To check the antibacterial efficacy against Enterococcus faecalis by various ayurvedic oils used as a solvent in endodontic sealers - An in vitro study

Aim: The aim of the study is to check the antibacterial efficacy of various ayurvedic oils used as a solvent with zinc oxide for preparing endodontic sealers. Materials and Methods: Forty-five extracted premolars were taken and were cut coronally and apically such that 7 mm of tooth specimen was prepared. Teeth were sterilized by autoclaving inoculated with Enterococcus faecalis and incubated for 24 h. The specimens were divided into three groups of 15 each. Group 1 – ZnO powder + Eugenol, Group 2 – ZnO powder + Aremidadi Oil, and Group 3 – ZnO powder + Dashmool oil. Bacterial growth in each specimen was calculated before and after sealer application and noted as the initial and final colony count. The antimicrobial effect of each sealer was measured by calculating the percentage reduction in colony count (%). One-way analysis of variance and post hoc tests will be used for statistical analysis. Results: The Zn + Arimedadi oil group showed the maximum antibacterial effect among the sealers tested and the Zn + eugenol sealer showed the least antimicrobial effect In comparison, there was a statistically significant difference between all the groups. Conclusion: Ayurvedic oil-based root canal sealers showed better antibacterial efficacy than eugenol-based sealers. Arimedadi oil showed the highest antibacterial activity against E. faecalis and Eugenol showed the least when used as a solvent.

Composition, Morphology, and Structure of Ultrafine ZnS–ZnO Powders Alloyed with Transition Metal Oxides

Composition, Morphology, and Structure of Ultrafine ZnS–ZnO Powders Alloyed with Transition Metal Oxides

Simple two-step synthesis of Ag/ZnO nanoparticles with enhanced photocatalytic response

This study presents a simple two-step synthesis method for the fabrication of Ag/ZnO nanocomposites to improve the photocatalytic response of ZnO. The synthesis involves ZnO nanoparticles that were fabricated from the thermal decomposition of commercial zinc acetate. In order to produce Ag/ZnO nanoparticles in a simple two-step process, ZnO nanoparticles were mixed with Ag nanoparticle suspensions previously obtained by the laser ablation of solids in liquids technique at three different fluences. Structural characterization of ZnO powders revealed the presence of single phase wurtzite ZnO nanoparticles with crystal sizes of 20 nm. On the other hand, XRD patterns for a composite sample revealed the presence of signals associated to both ZnO and Ag suggesting that silver nanoparticles were attached to the ZnO particles surface. Optical characterization of the ZnO powders, carried out by UV–vis spectroscopy, showed a strong absorption band centered at 380 nm, which is associated to excitonic transitions in ZnO nanoparticles, whilst absorption measurements of silver nanoparticles colloids revealed the presence of a strong band centered near 412 nm. This band shifts to shorter wavelengths with increasing fluence from 2.6 to 6.2 J cm−2, indicating changes in nanoparticles size. Photocatalytic degradation tests of methylene blue under UV irradiation were carried out using pure ZnO, Ag colloids and Ag/ZnO nanoparticles. After the first 30 min of irradiation, it was observed that the silver nanoparticles reached degradation percentages of 16, 22 and 29% for samples synthesized at 2.6, 4.2 and 6.2 J cm−2, respectively. Meanwhile the ZnO sample reached a value of 13% after 30 min. Regarding the Ag/ZnO composite sample, the percentage of degradation after 30 min was 36%, demonstrating a considerable enhanced photocatalytic activity as compared to ZnO. After 24 h irradiation, Ag/ZnO degraded 95% of the methylene blue solution. It was observed that decorating ZnO with laser produced silver nanoparticles accelerates the photocatalytic response of ZnO by enhancing the activity at short times.

The influence of varying Cu doping concentrations on the microstructure, phase evolution and surface wettability of ceramic glazes modified with nano Cu-ZnO

This study intended to develop nano Cu-doped nano ZnO-modified ceramic glazes. In this scope, nano-sized ZnO and nano Cu powders were incorporated into a commercial glaze composition and then the modified glaze was applied to the surface using the spraying method. The glazed tiles were sintered in a laboratory furnace at 1210oC for 10 min. The surfaces of the sintered samples were analyzed using scanning electron microscopy. X-Ray diffractometer, surface profilometer and contact angle goniometer. The study examined the influence of varying levels of Cu doping on the microstructural evolution and formation of phases, surface roughness, as well as the contact angle. Additionally, wettability conversion experiments were conducted under UV light. As a result, the addition of Cu increased the presence of Willemite crystals and also increasing the quantity and size of Plagioclase crystals. The contact angle of the sintered commercial glaze coated surface was measured to be 51.8o. However, when nano ZnO was added, the contact angle reduced to 44.4o. Likewise, the contact angle of the Cu doped nano ZnO coated surfaces decreased even further to approximately 33o. The inclusion of nano ZnO in commercial glaze resulted in a decrease in the Ra value, while doping Cu led to a modest increase in the Ra value. UV irradiation resulted in a reduction in the contact angles of all surfaces.

Master sintering curve analysis of ZnO densified by Cold Sintering Process

The Master Sintering Curve (MSC) model is traditionally used to describe the densification kinetics of a specific material and allows to determine the activation energy of the dominant mechanism. In this study, this approach is applied to the Cold Sintering Process (CSP) of ZnO with the addition of acetic acid. The result was compared with SPS sintered samples from the same dry powder. The apparent activation energy of the ZnO powder sintered by CSP with acetic acid is 4 times lower than the same dry powder (338 kJ/mol versus 83 kJ/mol). This low value confirms the low energy surface interactions between liquid and solid phases involved in mechanisms of ZnO. MSC model applied to CSP presents different interests to detect similarities or differences in sintering mechanism with different liquid phases. It allows to determine the densification trajectory of the material, then to select the optimum processing parameters to control its microstructure.

The effects of ZnO powder and different fiber types used in tuff/calcite-based geopolymers on electromagnetic shielding effectiveness

Electromagnetic (EM) shielding has become increasingly important in our modern world due to the growing use of electronic devices, which poses risks of EM pollution and its adverse effects on humans. Many studies have explored the incorporation of various additives into geopolymer mixes to enhance their EM shielding properties. This study investigates the impact of tuff/calcite-based geopolymers reinforced with three different types of fibers (Polypropylene, Steel, and Carbon) and varying percentages (2.5 %, 5 %, and 10 %) of ZnO powder on EM shielding effectiveness. Compressive strength, flexural strength, water absorption, length change tests, and EM shielding (900–6000 MHz at every 100MHz step) measurements were performed on geopolymer samples. Optimal shielding performance was achieved by the addition of 10 % ZnO by volume alongside carbon fiber. This combination resulted in a total shielding value of −78.92dB at a bandwidth of 2800MHz.