ZnO Powders Research Articles

Green synthesis of zinc oxide nanoparticles using the root hair extract of Phoenix dactylifera: antimicrobial and anticancer activity

Zinc oxide nanoparticles (ZnO NPs) were produced using the root hair extract of Phoenix dactylifera, and characterized by UV–Vis absorbance spectrophotometer, X-ray diffraction, particle size analyzer, and Fourier-transform infrared spectroscopy. Their antimicrobial activity and anticancer cytotoxicity were studied. An optimal nano-size range of 30.87–47.89 nm was obtained using 0.6 M of dihydrating zinc acetate salt and the root hair extract in a ratio of 1:2, respectively. ZnO NPs were observed to be around 45% more cytotoxic than doxorubicin (DOX) alone. Particularly, triple-negative breast cancer (TNBC) cells were observed to be more vulnerable to ZnO NPs than DOX alone which significantly reduced the viability of cancer cells to 9.01%. In addition, ZnO NPs were noticed to be 82.26% cytotoxic to lung cancer cells (A549). While testing ZnO powder did not cause any cytotoxicity on cancerous cells. Moreover, ZnO NPs showed promising antibacterial activity against different pathogenic organisms including Klebsiella pneumonia, Pseudomonas aeruginosa, Escherichia coli, Salmonella, and Staphylococcus aureus. Their activity was higher than the penicillin, gentamycin, and tetracycline based on the microbial inhibition zone. Generally, ZnO NPs demonstrate great potential for the chemotherapy of breast and lung cancer cells and bacterial infection.

Structural, nonlinear electrical characteristics, and stability against DC-accelerated aging stress behavior of Er-doped 20 nm ZnO-Bi2 O3 -Mn2 O3 -based varistors.

In this research, ZnO-Bi2 O3 -Mn2 O3 varistors manufactured from 20 nm ZnO powder and doped with different amounts of Er2 O3 were fabricated via the conventional ceramic processing method. The effect of various Er2 O3 concentrations (0.5-2.0mol%) on the sintered density, structural improvement, and nonlinear behavior of the 20 nm ZnO-Bi2 O3 -Mn2 O3 varistors was discussed. Different Er2 O3 concentrations exerted considerable influence on the varistors. The addition of large amounts of Er2 O3 led to the inhibition of grain growth by increasing the amount of the Er2 O3 -rich spinel phase. X-ray diffraction analysis showed that the addition of Er2 O3 to the varistor systems led to the development of Er2 O3 -rich phases during sintering. During sintering, the considerable surface area of the nanoparticle powder resulted in numerous interactions in the surfaces of the ceramics manufactured from 20 nm ZnO powder. The electrical behaviors of the varistors were substantially influenced by Er2 O3 . E1 mA evidently increased from 2,144.7 to 5,482.2V/mm with the increment in doping amount. The nonlinear coefficient also dramatically increased with the increase in Er2 O3 content. The ZnO nanoparticle-Bi2 O3 -Mn2 O3 varistors doped with 1.0-2.0mol% Er2 O3 possessed high voltage and nonlinearity and were stable against DC-accelerated aging stress.

Photocatalytic properties of ZnO powder sensitized by ZnTPP

In this study, ZnTPP-ZnO composite photocatalyst was prepared by impregnation method, and the samples prepared were characterized and analyzed by UV-Vis technology and TEM technology. The effects of light duration and ZnTPP loading on the photocatalytic degradation of methyl orange by ZnO were investigated. The experimental results show that ZnTPP is mainly loaded on the surface of ZnO particles in the form of surface adsorption, and plays the role of generating excited electrons and transferring electrons in photocatalysis. The degradation of methyl orange by the composite photocatalyst is mainly due to the photodegradation and the absorption peak is blue shift. The longer the light duration, the more degradation of methyl orange; The photocatalytic activity of ZnO is the highest when the sensitizer loading is 6 µmol.

Structural, optical and magnetic properties of Cd doped ZnO nanomaterials for optoelectronic device application

Cd-doped ZnO nanopowder is synthesized by solid-state reaction. XRD pattern shows a sharp pinnacle at θ = 36° which corresponds to (101) plane. Cd-doped ZnO powder shows a little aggleromation indicating that each grain is made of semicrystalline nature with little humps. FTIR shows a high intense broad IR band at 4350 cm−1 corresponding to the O–H stretching vibration. Raman studies clearly shows that the relays of two different peaks which are observed at 315 and 531 cm−1. Impedance plots state that the decrement in Z′ with expanding recurrence might be because of the increment of the AC conductivity. Dielectric behaviour occurs due to the large formation of grains associated with host lattice. Photosensitivity is found to be as high as 86% at input power of 120 mW. From the optical studies, the bandgap energy is measured and it is found to be 3.15 eV. Photoluminescence studies reveal that the sharp peak tends to move so wide as luminescent range changes from red to blue. The peak which has been seen at 631 nm indicates the green. EPR range demonstrates that Cd particles are in mutilated octahedral sties. The magnetic properties lie in the sample with the Cd fixation expands and the molecules can come close to each other and forms the clusters. These results suggest that these materials can be used for optoelectronic and luminescent device applications.

Structural, optical, cytotoxicity, and antimicrobial properties of MgO, ZnO and MgO/ZnO nanocomposite for biomedical applications

In this study, MgO nanoparticles were successfully fabricated and incubated inside ZnO NPs to form MgO/ZnO nanocomposite for biomedical applications. The x-ray diffraction analysis of MgO, ZnO, and MgO/ZnO has shown the single-phase x-ray diffraction patterns through X'pert High score. The crystallite sizes were calculated as 18 nm, 42 nm, and 53 nm, respectively. The average particle size of MgO, ZnO, and MgO/ZnO nanopowders depicted from secondary electron images of field emission electron microscopy were 56 nm, 400 nm, and 450 nm, respectively. The presence of MgO NPs inside ZnO NPs was confirmed by transmission electron microscopy. The elemental dispersive spectroscopy of MgO, given the peaks of oxygen and magnesium, also showed only zinc and oxygen peaks in ZnO, which confirms no other impurities in MgO and ZnO powders. The elemental analysis of MgO/ZnO nanocomposite showed the peaks of Zinc and Oxygen, along with a tiny peak of Mg. The photoluminescence and UV–vis spectroscopy revealed the absorbance fluorescence limit of the nanomaterials. Fourier transform infrared spectroscopy confirmed the several groups present in the nanocomposite. The biocompatibility of MgO, ZnO, and MgO/ZnO was observed with human peripheral blood mononuclear cells. The cytotoxicity studies were also performed against human cancer (liver and breast) cell lines. The MgO, ZnO, and MgO/ZnO exhibited the antimicrobial properties against Escherichia coli and Staphylococcus aureus.

Effect of atmosphere on recovery of diffuse reflection spectra of ZnO powder modified with nanoparticles upon irradiation in vacuum

Abstract The changes of diffuse reflection spectra (ρλ) in the range 0.2–2.2 μm and the integral absorption coefficient of solar radiation (as) of ZnO powder modified with SiO2 nanoparticles were studied. These changes were recorded in vacuum at the site of irradiation of the samples (in situ) after irradiation (30 keV electrons, 5 keV protons, and solar spectrum quanta (SSQ)), as well as upon exposure the samples to the atmosphere. It was found that for all types of irradiation, a significant recovery of the ρλ spectra in the near-IR region in the atmosphere is recorded. The recovery is 1.5 times for the samples irradiated with electrons and solar spectrum quanta, and 1.1 times for the sample irradiated with protons. In the visible region, absorption is due to the intrinsic point defects of ZnO, the reflection coefficient is not only not restored in the atmosphere, but it even decreases (1–3%). Mechanism of formation of photo- and radiation defects under these types and parameters of irradiation is explained; the processes of restoration of the ρλ spectra of the modified ZnO powder are considered.

Microwave Performance, Microstructure, and Crystallization of (Mg0.6Zn0.4)1−yNiyTiO3 Ilmenite Ceramics

The sintering behavior, microstructure analysis, crystallization, and microwave performance of (Mg0.6Zn0.4)1−yNiyTiO3 (y = 0.01–0.2) ceramics, processed with raw powders of MgO, NiO, ZnO, and TiO2 via the conventional solid-state method, are investigated. The main phases of (Mg0.6Zn0.4)1−yNiyTiO3 ceramics were obtained. With partial replacement by Ni2+, the (Mg0.6Zn0.4)0.95Ni0.05TiO3 could be well sintered at 1200 °C, and the microwave performance was shown to be positively correlated with sintering temperature. The permittivity (εr) saturated at 18.7–19.3, and the quality factor (Qf) values approached 72,000–165,000 (GHz) as the sintering temperatures increase from 1125 to 1250 °C. The temperature coefficient of resonance frequency (τf) falls in a stable range of −62.9 to −66 ppm/°C as sintering temperature rising. A permittivity (εr) of 19.3, a maximum Qf value of 165,000 (GHz), and a temperature coefficient (τf) of −65.4 ppm/°C were measured for the samples at 1200 °C/4 h. (Mg0.6Zn0.4)0.95Ni0.05TiO3 material system shows high potential for applications of high frequency-selection components in satellite communication and 5G wireless telecommunication systems.

Terahertz Permittivity of Pressed ZnO and CuO Powder in Polyethylene Pellets: Effect of Porosity

Terahertz (THz) spectroscopy is used to measure permittivity (100 GHz-2.5 THz) of ZnO and CuO powders with low fill factor pressed into pellets in a polyethylene binder. We show that porosity (air) of such pressed pellets has a large effect on effective pellet permittivity (~10%) and on the extracted permittivity of the oxide constituent (~150%). We explore a two-step analysis based on sequential application of different effective medium models, first to account for the air, and subsequently to extract the oxide's dielectric properties. We show that the combination of Vegard's law and the Maxwell-Garnett model is the best combination to account, respectively, for the air and the oxide powders. In this regard, the capacity that this approach has to adapt to each phase's physical characteristics by using multiple EMMs is an advantage. The resulting oxide permittivities are significantly larger than previously reported for such pellets as a consequence of the porosity. We find for the real relative permittivities of CuO and ZnO ~12.1 and ~8.9, respectively, in the THz range.

Facile one-step deposition of ZnO-graphene nanosheets hybrid photoanodes for enhanced photoelectrochemical water splitting

ZnO-graphene nanosheets photoanodes were deposited at room temperature by a one-step kinetic spray process on a titanium sheet from micro-sized ZnO and graphite powders. ZnO-graphene nanosheet hybrid photoanodes with varying graphite contents were utilized for studying photoelectrochemical (PEC) water splitting. The Raman spectra revealed the direct transformation of micro-sized graphite powder to graphene nanosheets in all hybrid photoanodes after the deposition process, without any post-treatment. Surface morphology analysis revealed the fragmentation of the micro-sized flake morphology to morphology composed of mixed nanorods and nanosheets. The optical properties of the ZnO-graphene nanocomposites were investigated by the diffuse reflectance and photoluminescence (PL) emission spectroscopy, which revealed the decrease of the optical band gap and quenching of PL intensity. The hybrid photoanode with 50 wt% graphite content revealed the smallest bandgap of 2.6 eV and the lowest emission intensity compared with other hybrid photoanodes, which demonstrated the inhibition of photogenerated charge carrier recombination rate as well as an improvement in the visible-light-harvesting. The PEC results exhibited an improvement of the photocurrent with the incorporation of graphene nanosheets due to the improved photogenerated charge transfer kinetics and separation. The hybrid photoanode with 50 wt% graphite content revealed the highest photo-response current of 4.82 mAˑcm−2 corresponds to photoconversion efficiency of 3.25% @1.23 V vs. RHE.

A Study on Sebum Hardening Effect of ZnO Powder

Zinc oxide is transparent inorganic UV absorber and widely used as a sunscreen. But sunscreen on the skin is easily erased by sebum, so zinc oxide with a sebum curing function was studied. In this study, a zinc oxide powder was prepared using zinc chloride and sodium hydroxide via a hydrothermal synthesis method. The process conditions including reaction temperature and sodium hydroxide ratio were determined. Particle size was determined using XRD and SEM, and process tendencies were checked using the gelling test method. When the sodium hydroxide ratio was lower than 58.7 wt%, the gelling time was reduced, and when the temperature was lower than 60 <sup>o</sup>, the gelling time decreased. ZnO and Simonkolleite confirmed that the gelling time was reduced when the mixture comes out.

ZnO:Al thin films from (Al2O3)x(ZnO)(1-x) powder targets by magnetron sputtering

In the present work we prepared Aluminum doped Zinc Oxide (AZO) thin films from powder targets. Various concentrations (W/W percentages) of Al2O3 such as1%, 2%, 3%, 4%, 5%, 6%, 7% and 8% were mixed in ZnO powder and made in the form of a 3 inch disc target. These ceramic targets are sputtered in RF magnetron sputtering unit for the deposition of AZO thin films. Optical and electrical properties are analyzed to get an optimized percentage of mixing for achieving high transparency and low resistivity. At Al2O3 percentage of 3% there is a considerable decrement in the resistivity, and at 7% there is a considerable decrease in the optical transmittance. Mobility and carrier concentration are increasing with Al2O3 percentage. Bandgap of the films is observed to be decreasing with increasing the Al2O3 percentage.

Preparation and Characterization of Planar-Type ZnO Powder with High Aspect Ratio for Application in Ultraviolet- and Heat-Shield Cosmetics.

In this study, a [0001]-plane planar-type ZnO ceramic powder material with a high aspect ratio ranging from 20:1-50:1 is synthesized using the electrolyte collected from zinc air battery power generation. This high aspect ratio may be due to the Zn(OH)2-₄ anion dissolved in the electrolyte. The obtained planar-type ZnO exhibits excellent formulation stability and applicability, even when formulated as a cosmetic with a single inorganic ingredient. Compared to commercial ZnO or TiO₂ powders, relatively better protection against infrared and ultraviolet (UV) radiation is realized due to its asymmetric characteristics, with a width of approximately 1 μm and thickness of tens of nm. The synthesized planar-type ZnO is mixed with nanosized ZnO or TiO₂ commercial powders and formulated into various combinations to achieve a high UV protection rate and heat-blocking effect. In particular, the addition of planar-type ZnO to nanosized TiO₂ powders increases the heat-blocking effect, and improves the applicability and formulation stability of the cosmetic formulation, despite the decrease in turbidity. Among all the ceramic powder combinations examined in this study, the best UV protection rate and heat-blocking effect are obtained when the synthesized planar-type ZnO is mixed with microsized and nanosized TiO₂.

Photocatalytic Decolorization Simulated Textile Dyebath Effluent under Solar Light and Reuse it for Industrial Propose

In this work, the photocatalytic is related to simulated wastewater as well as recycling for industrial uses. Photocatalytic degradation of simulated wastewater content (Eosin Yellowish, Eriochrom Black T, Methyl Violet, EDTA, FeSO4.7H2O, NaCl, and NaOH) was utilized as a treatment approach in batch reactors within solar light in a heterogeneous slurry with the use of many concentrations regarding the commercial powder ZnO as photocatalysts semiconductors. We have tested many operation conditions like (catalyst concentration, pH, initial dye concentration and final water treated properties). The water quality related to treated wastewater is based on the nature of waste added during usage, the industrial water supply quality, and the treatment degree which is received via wastewater. After that, the quality data of wastewater is evaluated and indicated at waste-water treatment plant majorly for the disposal of the treated effluents or discharge requirements with regard to gross pollution parameter.

Synthesis of Al-Doped ZnO Films Assisted with Hollow-Cathode Glow Discharge and Their Characterization

Transparent conductive oxides, such as aluminum-doped zinc oxide (AZO), are of substantial importance for use in a broad range of applications because of their excellent optical and electrical properties. AZO film can be deposited by using several conventional techniques, although they suffer from limitations such as long deposition time, high cost, and the requirement for complex deposition equipment. Here, we used hollow-cathode glow discharge, which produces a high-density plasma and achieves high deposition efficiency. Remarkably, instead of metallic target materials, we used Al2O3 and ZnO powders filled in the hollow cathode as a target, thus avoiding the need for specifically designed targets in this technique. The films were deposited using mixtures of argon and oxygen at various ratios (0% to 50% oxygen), to improve the film characteristics. The films deposited under all conditions exhibited hexagonal wurtzite ZnO structure, while the grain size increased with increasing oxygen content. The film was thick and porous when using low oxygen content, but became thin and dense with increasing oxygen content. The optical transmittance was found to be strongly dependent on the processing gases used, with the highest transmittance of 84% being attained when using 25% oxygen gas. The bandgap of the films lay between 3.27 eV and 3.33 eV. The highest carrier concentration and mobility were attained when using 25% oxygen, and the Hall resistivity decreased with increasing oxygen content. Besides the excellent transmittance and electrical properties of the deposited films, it is expected that the results of this study will be useful for solar cells and optoelectronic applications due to the relatively low cost of this technique and the lack of specific target requirements.

Biophysical Characterization of Thin Films of Zinc Oxide Prepared by Sol-Gel

In this research, ZnO nano-powder was used, and the work was in two biological and physical parts. Where the work of the first part was to examine the effect of ZnO powder on Staphylococcus aureus, and the result of inhibition was 100%. As for the second part, the preparation of a thin film by the Sol-Gel method, where thin films were deposited on glass, the structural properties and topography of the surface were studied. The prevailing trend (101). Also, the results of the atomic force microscopy (AFM) tests showed that the resulting granular size of the prepared and annealed films with a temperature (400 ° C) was less than 100 nm, wherein an anti-bacterial nanoscale S. aureus was made.

Optical, Microstructure, and Electromagnetic Properties of (1 − x)ZnO − xCuO Powders Prepared Using Two-Stage Sintering and Direct Synthesis

In this study, CuO, ZnO, and (1 − x)ZnO − xCuO (CZO) powders were synthesized through the aqueous solution method. Sintering (separate) and direct synthesis were conducted at 500°C and 700°C, respectively, to produce CuO, ZnO, and CZO powders in different proportions. Various proportions of (1 − x)ZnO−xCuO (x = 0.33, 0.5, 0.67) powders were analyzed and compared under various temperature and process conditions. The morphology, phase structure, and photoelectromagnetic properties of CZO were analyzed to determine the influence of ZnO, CuO, and their mutual doping on the photoelectromagnetic properties. The results revealed that direct synthesis was the most effective process and that CZO powder exhibited the best electromagnetic properties when the Cu doping ratio was high—when Cu:Zn was close to 1:1. When Cu was doped excessively (x = 0.67), it resulted in the formation of the cuprous oxide phase, which is detrimental to the electrical and magnetic properties of CZO powder.

Metal–Organic Framework for Efficient Electron Injection

AbstractA 3D metal–organic framework (MOF) [(H3O)Zn(HCOO)3]∞ is developed as a highly efficient and air‐stable solution‐processed electron injection layer (s‐EIL). The [(H3O)Zn(HCOO)3]∞ film can be easily obtained by annealing a spin‐coated [Zn(HCOO)2(H2O)2]∞ film at 120 °C in air, which is facilely prepared by the reaction of ZnO powder with formic acid and the aqueous solution of ammonium. The un‐encapsulated electron‐only device with [(H3O)Zn(HCOO)3]∞ as the s‐EIL exhibits significantly enhanced electrical property and air stability, compared to that with vacuum‐evaporated Cs2CO3 as EIL. Such improvements can also be observed in inverted organic light‐emitting diodes. The device with [(H3O)Zn(HCOO)3]∞ s‐EIL demonstrates an operating voltage of 6.8 V at 1000 cd m−2, much lower than that with Cs2CO3 EIL (8.4 V). And the power efficiency is increased about 18%. The enhanced electron injection property of [(H3O)Zn(HCOO)3]∞‐modified indium–tin oxide (ITO) is attributed to its reduced work function compared to bare ITO, which is confirmed by ultraviolet photoelectron spectroscopy analysis. This approach is anticipated to be applied in other optoelectronic devices for efficient electron injection.

Simple and scalable synthesis of urchin-like ZnO nanoparticles via a microwave-assisted drying process

The urchin-like nanoparticles of semiconducting oxides have been attracting considerable attention as they can significantly improve reactivity owing to their enlarged surface areas. Herein, we report a simple and scalable synthesis method of ZnO nanomaterials via a microwave-assisted drying process. Commercial ZnO powders (~300 nm) and expanded graphite were used as starting materials to prepare urchin-like ZnO nanoparticles with nanoscale legs (diameter ~20 nm) by triggering the rapid phase transformation, which was induced by a repeated microwave irradiation in an alumina crucible for a few minutes. The possible mechanisms to trigger this morphological and dimensional change are described in detail. The high-yield production and superior reproducibility completed in shortened processing times enable this synthetic route to be widely applicable for the massive production of nanostructured oxide particles.

Improving ZnO photoinitiation efficiency by surface reaction with 2-hydroxy-2-methylpropiophenone

ZnO was used as an inorganic photoinitiator in polymeric materials to reduce the pollutions of organic photoinitiators and their photolysis fragments. However, the ZnO photoinitiator suffered low monomer conversions and efficiencies. Therefore, a novel inorganic-organic hybrid ZnO photoinitiator (ZnO-TDI-1173) was prepared by the surface reaction of ZnO, on which OH groups reacted with one NCO group of toluene diisocyanate and then another NCO group reacted with 2-hydroxy-2-methylpropiophenone. The FTIR, scanning electron microscope, thermogravimetric analysis, and X-ray diffraction were characterized and proved the successful surface modification. The photoinitiated polymerization kinetics of ZnO-TDI-1173 in methyl methacrylate were studied. When the UV irradiation time was 220 s, the methyl methacrylate conversion with ZnO-TDI-1173 reached 32.14%, which was bigger than 18.26% of ZnO. This investigation demonstrated an improved photoinitiation efficiency of ZnO-TDI-1173 in comparison with that of ZnO, facilitating a new and easy method to upgrade the large ZnO powder to be an efficient photoinitiator.

Comparative Study of Cold Sintering Process and Autoclave Thermo-Vapor Treatment on a ZnO Sample

Analysis of scanning electron microscopy images was used to study the changes in the crystal size distribution of ZnO, which occurred during its processing in an aqueous medium at 220–255 °C and an equilibrium vapor pressure in an autoclave. The results were compared with those of ZnO placed in a die for treatment under similar conditions supplemented with mechanical pressure application in the cold sintering process. In both cases, ZnO was treated in the presence of an activating additive: either zinc acetate or ammonium chloride. During autoclaving, a powder consisting of fine ZnO monocrystals was obtained, while the cold sintering process led to ceramics formation. Under vapor pressure and mechanical pressure, the aqueous medium affected ZnO transformation by the same mechanism of solid-phase mobility activation due to the additives’ influence. The higher the content of additives in the medium, and the higher the mechanical pressure, the more pronounced activating effect was observed. Mass transfer during the cold sintering process occurred mainly by the coalescence of crystals, while without mechanical pressure, the predominance of surface spreading was revealed. In the initial ZnO powder, the average crystal size was 0.193 μm. It grew up to 0.316–0.386 μm in a fine-crystalline powder formed in the autoclave and to an average grain size of 0.244–0.799 μm in the ceramics, which relative density reached 0.82–0.96. A scheme explaining the influence of an aqueous medium on the solid-phase mobility of ZnO structure was proposed. It was found that the addition of 7.6 mol% ammonium chloride to the reaction medium causes the processes of compaction and grain growth similar to those observed in ZnO Cold Sintering Process with the addition of 0.925 mol% zinc acetate.