Bulk Zinc Oxide Research Articles

Exploring the Anti-Corrosion, Photocatalytic, and Adsorptive Functionalities of Biogenically Synthesized Zinc Oxide Nanoparticles

This study reported the synthesis of ZnO nanoparticles (ZnO NPs) using Cucurbita pepo L. seed extract and explored their multifunctional properties such as anti-corrosion, photocatalytic, and adsorption capabilities. The synthesized ZnO NPs were characterized by Fourier-transform infrared spectroscopy (FTIR) to identify their functional groups, thermogravimetric analysis (TGA) to assess their thermal stability, transmission electron microscopy (TEM), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) to determine their size, morphology, and elemental composition. The characterization of biofabricated ZnO NPs revealed an average particle size of 32.88 nm; however, SEM displayed a tendency for the particles to agglomerate. Furthermore, the X-ray diffraction (XRD) and EDX analysis confirmed the NPs as ZnO, matching patterns reported in the literature. In this study, the potential of the biogenic ZnO NPs was explored for multifunctional applications. Zinc oxide nanoparticles exhibited a higher capacity for adsorbing hydrogen sulfide (H2S) compared to bulk zinc oxide, mostly because of their larger surface area. In addition, electrochemical studies demonstrated a substantial enhancement in the corrosion resistance of mild steel in a 1.0 M HCl solution. ZnO NPs also demonstrated remarkable photodegradation effectiveness, reducing 75% of methyl orange in 60 min under sun-light irradiation. This implies that they could be used to remediate organic pollutants (organic dyes) from wastewater.

Enhancing zinc biofortification and mitigating cadmium toxicity in soil–earthworm–spinach systems using different zinc sources

Cadmium (Cd) pollution poses significant threats to soil organisms and human health by contaminating the food chain. This study aimed to assess the impact of various concentrations (50, 250, and 500 mg·kg–1) of zinc oxide nanoparticles (ZnO NPs), bulk ZnO, and ZnSO4 on morphological changes and toxic effects of Cd in the presence of earthworms and spinach. The results showed that Zn application markedly improved spinach growth parameters (such as fresh weight, plant height, root length, and root-specific surface area) and root morphology while significantly reducing Cd concentration and Cd bioconcentration factors (BCF-Cd) in spinach and earthworms, with ZnO NPs exhibiting the most pronounced effects. Earthworm, spinach root, and shoot Cd concentration decreased by 82.3 %, 77.0 %, and 75.6 %, respectively, compared to CK. Sequential-step extraction (BCR) analysis revealed a shift in soil Cd from stable to available forms, consistent with the available Cd (DTPA-Cd) results. All Zn treatments significantly reduced Cd accumulation, alleviated Cd-induced stress, and promoted spinach growth, with ZnO NPs demonstrating the highest Cd reduction and Zn bioaugmentation efficiencies compared to bulk ZnO and ZnSO4 at equivalent concentrations. Therefore, ZnO NPs offer a safer and more effective option for agricultural production and soil heavy metal pollution management than other Zn fertilizers.

Evaluation of the teratogenic potency of bulk zinc oxide and its nanoparticles on embryos of the freshwater snail, Helisoma duryi

Bulk zinc oxide (ZnO-BPs) and its nanoparticles (ZnO-NPs) are frequently used in various products for humans. Helisoma duryi embryos can serve as effective model organisms for studying the toxicity of NPs. This study aimed to compare the teratogenic potency of ZnO-BPs and ZnO NPs in the embryonic stages of H. duryi to evaluate the utility of this snail as a bioindicator for ZnO-NPs in the aquatic environment. The mechanisms of teratogenesis were evaluated by determination of the LC50, studying the effect of sub-lethal concentrations of both ZnO forms on the embryos, and studying their enzyme activity, oxidative stress, and biochemical analysis. The SDS-PAGE electrophoresis was undertaken to assess the effect of ZnO-BPs and ZnO NPs on protein synthesis. The results revealed that the veliger stage of H. duryi is the specific stage for bulk and nano ZnO. ZnO-NPs proved to be more toxic to snails’ embryos than ZnO-BPs. Exposure to ZnO influences specific types of defects in development, which in the case of BPs are far less drastic than those caused by NPs. Thus, the toxicity of ZnO-NPs in embryonic development is due to their unique physicochemical properties. The observed malformations include mainly hydropic malformation, exogastrulation, monophthalmia, shell misshapen, and cell lyses. Almost all tested oxidative biomarkers significantly changed, revealing that ZnONPs display more oxidative stress than ZnO-BPs. Also, the low concentration of ZnO induces many disturbances in the organic substances of veliger larvae, such as a decrease in the total protein and total lipid levels and an increase in the glycogen level. The results indicated that ZnO-BPs increase the number of protein bands. Conversely, ZnO-NPs concealed one band from treated egg masses, which was found in the control group. Embryos of snail are an appropriate model to control freshwater snails. This study demonstrates that H. duryi embryos can serve as effective model organisms to study the toxicity of ZnO-NPs.

Reproductive performance of freshwater snail, Helisoma duryi under the effect of bulk and nano zinc oxide.

Nanotechnology has been used to apply nanoparticle essential elements to enhance the ability of animals to absorb these elements and consequently improve their reproductive performance. High concentrations of nanoparticles (NPs) can directly harm a range of aquatic life forms, ultimately contributing to a decline in biodiversity. Helisoma duryi snails are a good model for studying the toxicological effects of bulk zinc oxide (ZnO-BPs) and nano zinc oxide (ZnO-NPs) on freshwater gastropods. This study aimed to compare the toxic effects of ZnO-BPs and ZnO-NPs on H. duryi snails and explore how waterborne and dietary exposure influenced the reproductive performance of this snail. ZnO-BPs and ZnO-NPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder (XRD). This study revealed that the size of ZnO-BPs and ZnO-NPs were 154 nm and 11-31 nm, respectively. The results showed that exposure of adult snails to sub-lethal concentrations of both ZnO forms (bulk and nano) for 24 h/week for 4 weeks markedly changed their reproductive performance in a concentration-dependent manner, where fecundity was negatively affected by high concentrations. It was concluded that dietary exposure to the lowest tested concentration of ZnO-NPs (1 ppm) has a positive effect as the number of eggs and egg masses/snails increased and the incubation period decreased. Also, poly-vitelline eggs (The formation of twins) were observed. ZnO-NPs at low concentrations positively affect the reproductive performance of snails, especially after dietary exposure. The results revealed that 1 ppm ZnO-NPs could be supplementary provided to snails to improve their fertility, reduce the developmental time course, increase hatchability percentage, and produce poly-vitelline eggs.

ZnO nanoparticles: A key ingredient of sunscreen shows absence of adverse effects on Drosophila melanization pathway

The rapid development of zinc oxide nanoparticle (ZnO NP) based sunscreens, shampoos and other skin care products has raised a concern about their safety at the cellular level. The melanization pathway, being an important pathway of skin cells, is prone to being affected by ZnO NPs. Therefore it is necessary to understand the ZnO NP mediated effect on the melanin synthetic pathway. Our previous study on bulk zinc oxide has shown that large sized zinc oxide particles did not have any adverse effect on melanization in Drosophila, hence it would be interesting to study the behavior of ZnO when present in the nano-form by virtue of the changed size and thereby changed properties. The present study was undertaken to investigate ZnO NP mediated effects on key metabolites of the Drosophila melanin pathway. Spectrophotometric analysis of melanin was performed. followed by a study of the enzyme activity of phenol oxidase and HPLC quantification of dopa and tyrosine. FTIR spectroscopy was carried out to examine the interaction of the ZnO NPs and precursor amines of the melanin synthetic pathway. Pigmentation mutants of Drosophila were also investigated for validation of the results under a different genetic background. The ZnO NPs did not show any decrement in the levels of melanin after the treatment. Moreover there was no adverse effect on the phenol oxidase activity, Tyrosine and L-Dopa. The FTIR studies showed minimal interaction between the ZnO NPs and the metabolites of the melanin pathway. The results of the present study have clearly indicated the absence of any adverse effects on key metabolites of the melanin pathway after ZnO NP treatment in both wild-type and mutant Drosophila. This is the first report of a detailed analysis of ZnO NP mediated effects on key constituents of the Drosophila melanization pathway, providing information about its safety for the usage in cosmetics.

Examining the Influence of Zinc Oxide Nanoparticles and Bulk Zinc Oxide on Rat Brain Functions: a Comprehensive Neurobehavioral, Antioxidant, Gene Expression, and Histopathological Investigation

The study aimed to assess the impact of zinc oxide nanoparticles (ZnONPs) on rats’ neurobehavior compared to bulk zinc oxide (BZnO). Thirty male Sprague-Dawley rats were randomly assigned to five groups. The control group received Tween 80 (10%), while the ZnONP groups were given ZnONPs at 5 and 10 mg/kg body weight dosages, and the bulk zinc oxide (BZnO) groups received BZnO at the same dosages. Behavioral observations, neurobehavioral examinations, and assessments of brain tissue oxidative markers, neurotransmitter levels, and histopathological changes were performed. The results indicated that ZnONP at a dosage of 5 mg/kg improved general behavior, locomotor activity, memory, and recognition and reduced fearfulness in rats. Conversely, the higher dosage of 10 mg/kg and the bulk form had adverse effects on general behavior, locomotor activity, and learning ability, with the bulk form demonstrating the most severe impact—znONP-5 treatment increased antioxidant enzyme levels and decreased inflammatory markers. BZnO-5 exhibited lower oxidative stress markers, although still higher than BZnO-10. Furthermore, ZnONP-5 and BZnO-5 increased neurotransmitter levels compared to higher dosages. ZnONP-5 upregulated the expression of brain-derived neurotrophic factor (BDNF) mRNA, while BZnO-5 showed increased BDNF mRNA expression and decreased expression of genes related to apoptosis and inflammation. In summary, ZnONPs at 5 mg/kg demonstrated positive effects on rat brain function and behavior, while higher dosages and the bulk form had detrimental effects. In conclusion, the studies emphasized the importance of further assessing various doses and forms of zinc oxide on brain health, highlighting the significance of dosage considerations when using nanomaterials.

Physical Properties of ZnO-NPs Induced by the Thermal Annealing of Hydrozincite Derived from Adansonia Digitata Leaves Extract

In this study, we investigated the effects of the annealing temperatures on the physical properties of zinc oxide nanoparticles produced by the decomposition of the hydrozincite obtained from Adansonia digitata leaves. The results of the X-ray diffraction revealed the formation of well-crystallised hexagonal zinc oxide with an average crystallite size of 11.80 nm, 11.90 nm, 11.97 nm and 15.28 nm for the samples annealed at 400 °C, 500 °C, 600 °C and 700 °C, respectively. The crystallite size of the hydrozincite constituting the unannealed sample was 22 nm. In the spectra of the Fourier transform infrared spectroscopy, the appearance of the peaks at 520 cm-1 for all synthesised materials confirms the formation of pure wurtzite zinc oxide. The band gap determined from diffuse reflectance ultraviolet-visible spectroscopy was found to be 3.19 eV, 3.21 eV, 3.23 eV and 3.24 eV for the samples annealed at 400 °C, 500 °C, 600 °C and 700 °C, respectively. These values increase with the annealing temperature and are still lower than the band gap of pure bulk zinc oxide (3.3 eV) owing to the structural defects as confirmed by the broad emission bands in the visible depicted from the photoluminescence analysis.

Ab Initio Study of Structural and Magnetic Properties of Cobalt Doped Zinc Oxide

Abstract.In this study, we have investigated the electronic and magnetic properties of Cobalt doped zinc oxide (ZnO) bulk materials using density functional theory (DFT) calculations. The substitution of Co atoms into the ZnO lattice is systematically explored to understand its impact on the electronic band structure, magnetic moments and stability of the material. It is observed that Co doping introduces localized magnetic moments of 3.073 μB associated with Co atoms. The electronic band structure exhibits the semi-metallic nature after the Co doping with a majority spin (↑) and a minority spin (↓) magnetic configuration hybridization between Co 3d and 2p orbitals of O, indicating the potential for spin-polarized transport in Co-doped ZnO. We have also analyzed the formation energies to assess the thermodynamic stability. It is observed that the binding energy per atom slightly decreased to -3.563 eV, indicating stable Co incorporation. From the obtained results it can be concluded that, through controlled doping strategies the electronic and magnetic properties in ZnO-based materials can be altered for desired properties.

Evaluating the Effectiveness of Vitamins E and C in Mitigating the Toxic Effects of Zinc Oxide Bulk and Nanoparticles on Fish: A Review

Evaluating the Effectiveness of Vitamins E and C in Mitigating the Toxic Effects of Zinc Oxide Bulk and Nanoparticles on Fish: A Review

Effects of nanoscale zinc oxide treatment on growth, rhizosphere microbiota, and metabolism of Aconitum carmichaelii.

Trace elements play a crucial role in the growth and bioactive substance content of medicinal plants, but their utilization efficiency in soil is often low. In this study, soil and Aconitum carmichaelii samples were collected and measured from 22 different locations, followed by an analysis of the relationship between trace elements and the yield and alkaloid content of the plants. The results indicated a significant positive correlation between zinc, trace elements in the soil, and the yield and alkaloid content of A. carmichaelii. Subsequent treatment of A. carmichaelii with both bulk zinc oxide (ZnO) and zinc oxide nanoparticles (ZnO NPs) demonstrated that the use of ZnO NPs significantly enhanced plant growth and monoester-type alkaloid content. To elucidate the underlying mechanisms responsible for these effects, metabolomic analysis was performed, resulting in the identification of 38 differentially expressed metabolites in eight metabolic pathways between the two treatments. Additionally, significant differences were observed in the rhizosphere bacterial communities, with Bacteroidota and Actinobacteriota identified as valuable biomarkers for ZnO NP treatment. Covariation analysis further revealed significant correlations between specific microbial communities and metabolite expression levels. These findings provide compelling evidence that nanoscale zinc exhibits much higher utilization efficiency compared to traditional zinc fertilizer.

Charge-trap memory effect in spray deposited ZnO-based electrolyte-gated transistors operating at low voltage

Charge-trap memory phenomena were demonstrated in an electrolyte-gated transistor (EGT) using a spray-coated zinc oxide (ZnO) active layer and a cellulose-based electrolyte. The EGT exhibited efficient programming and erasing characteristics at low voltages, shifting the threshold voltage and the magnitude of the on-current. This behavior is discussed in terms of the influence of charged trapping states at the ZnO/electrolyte interface and within the ZnO bulk. The presence of these traps leads to a shift in the mobility from 0.57 ± 0.16 cm2 V−1 s−1 in the initial state to 0.02 ± 0.01 cm2 V−1 s−1 when programmed. Retention experiments revealed improved stability of the memory state when a low positive voltage is applied to the gate, indicating that the device's characteristics are extremely sensitive to the trapping/detrapping of charges at the semiconductor/electrolyte interface. Capacitance spectroscopy measurements using planar and metal-insulator-semiconductor configurations within the same device were used to analyze the charging dynamics of the trap states at different programming states.

Ultrafast Charge Dynamics in Bulk Zinc Oxide under Intense Photoexcitation

The photo-induced charge dynamics of textbook wide-bandgap semiconductor ZnO have been investigated on the picosecond time-scale. We performed optical Pump-THz Probe experiments in order to measure the dielectric constant of the material after high-fluence photo-excitation of charge carriers. The technique allows access to both carrier lifetime and scattering rates, and it provides direct access to the intrinsic dielectric function changes upon excitation. A complex dynamic is unveiled in the high-fluence pumping regime, where the relaxation time is in the hundreds of picoseconds range and increases with increasing Pump fluence, while the onset of photoconductivity takes place in a few picoseconds. The plasma frequency and the relaxation time dependence on the Pump fluence are discussed.

Bulk ZnO, nanoparticles, nanorods and thin film: A comparative study of structural, optical and photocatalytic properties

Zinc oxide (ZnO) nanostructures, including nanoparticles, nanorods, and thin film, were prepared using thermal decomposition, hydrothermal and sputtering methods, respectively. Structural and optical properties of the nanostructures were compared with bulk ZnO. X-ray diffraction patterns of the samples show the formation of the wurtzite structure. XRD pattern demonstrates that the nanorods have grown along the [002] direction. Particle size obtained by FESEM shows that the nanoparticles, nanorods, and thin film, with different grain size were prepared. Atomic force microscopy (AFM) images of the thin film confirmed the uniformity of the ZnO layer, and a more significant peak-to-valley height than the thickness of the sputtered zinc layer (300 nm) was obtained. Band gap of the bulk sample was higher than the nanostructures, which was due to fewer defects in the bulk sample. Photoluminescence spectrum confirmed the presence of defects and emissions due to near absorption edge in the nanostructures and bulk sample. Finally, the photocatalytic activity of the samples was evaluated for degradation of oxytetracycline antibiotic. The high degradation rate of nanoparticles was attributed to the high surface/volume ratio and inherent defects. With the high photocatalytic efficiency, the prepared ZnO nanoparticles sample can be considered as potential candidate for water treatment and removal of environmental pollutants.

The defect-state-assisted enhancement of high harmonic generation in bulk ZnO

Optical modulation of high harmonic generation (HHG) at ultrashort timescales is of fundamental interest and central importance for emerging photonic applications. Traditionally, this modulation is realized by injecting incoherent electrons into the conduction band, which can only result in the suppression of HHG intensity. In this work, we have proposed and demonstrated an all-optical route to amplify a specific order of high harmonic generation in (11-20)-cut wurtzite zinc oxide (ZnO) based on the pump-probe configuration. Specifically, intensity enhancement is demonstrated by tuning the wavelength of the generation middle-infrared pulse when the wavelength of HHG matches the energy of a specific defect state. The maximum enhancement factor is observed to be 1.8, while the modulation speed varies with different defect states, which are 0.1 ps for the 5th HHG and 1.5 ps for the 4th HHG. This work might enlighten a new path for ultrafast modulation of HHG in solids for the future development of all-optical devices.

Towards a Highly Efficient ZnO Based Nanogenerator.

A nanogenerator (NG) is an energy harvester device that converts mechanical energy into electrical energy on a small scale by relying on physical changes. Piezoelectric semiconductor materials play a key role in producing high output power in piezoelectric nanogenerator. Low cost, reliability, deformation, and electrical and thermal properties are the main criteria for an excellent device. Typically, there are several main types of piezoelectric materials, zinc oxide (ZnO) nanorods, barium titanate (BaTiO3) and lead zirconate titanate (PZT). Among those candidate, ZnO nanorods have shown high performance features due to their unique characteristics, such as having a wide-bandgap semiconductor energy of 3.3 eV and the ability to produce more ordered and uniform structures. In addition, ZnO nanorods have generated considerable output power, mainly due to their elastic nanostructure, mechanical stability and appropriate bandgap. Apart from that, doping the ZnO nanorods and adding doping impurities into the bulk ZnO nanorods are shown to have an influence on device performance. Based on findings, Ni-doped ZnO nanorods are found to have higher output power and surface area compared to other doped. This paper discusses several techniques for the synthesis growth of ZnO nanorods. Findings show that the hydrothermal method is the most commonly used technique due to its low cost and straightforward process. This paper reveals that the growth of ZnO nanorods using the hydrothermal method has achieved a high power density of 9 µWcm-2.

Zinc Oxide Nanoparticles and Fe-Modified Activated Carbon Affecting the In Vitro Growth of Date Palm Plantlets cv. Medjool

The survival and growth of in vitro plantlets are still problematic for the date palm; thus, the application of nanotechnology may provide date palm plantlets that develop faster with enhanced growth and biochemical parameters. Moreover, the usage of Fe-modified activated carbon (Fe-AC) prepared from date palm pits instead of activated charcoal (AC) in tissue culture media during the current investigation can be considered an innovative approach. Furthermore, the effect of zinc oxide nanoparticles (ZnO-NPs) and bulk particles (ZnO-BPs) on the rooting and growth of date palm plantlets and on some physiological indices was also investigated. X-ray diffraction, dynamic light scattering, scanning electron microscopy, and transmission electron microscopy were used to characterize Fe-AC and ZnO-NPs. As detected from the characterization, the particle size was 720 nm for Fe-AC and 60 nm for ZnO-NPs. The obtained results indicated that AC significantly enhanced plantlet growth, plantlet height, number of leaves/plantlet, root length, number of roots/plantlet, and the concentrations of IAA, chlorophyll a and chlorophyll b compared with Fe-AC. On the other hand, sugars and phenols concentrations, and POD and PAL activities were highly increased with Fe-AC. There was no significant difference in terms of plant fresh weight (FW), leaf length, leaf width, protein, amino acids, and carotenoids. ZnO nanoparticles significantly improved plant height, leaf length, leaf width, root length, and the concentrations of IAA, chlorophylls a and b, and carotenoids; in contrast, the bulk form increased roots/plantlet, amino acids, and total sugars. Supplying the MS medium with combinations of ZnO-NPs or ZnO-BPs and AC or Fe-AC significantly increased all growth and physiological parameters. Plant height, leaf length, leaf width, root length, and the concentrations of IAA, protein, and chlorophylls a and b significantly increased when ZnO-NPs were combined with AC. Amino acids, total sugars, carotenoids, and phenols concentrations and the activities of POD and PAL increased when ZnO-BPs and Fe-AC were added together.

A comparative evaluation of the effects of seed invigoration treatments with precursor zinc salt and nano-sized zinc oxide (ZnO) particles on vegetative growth, grain yield, and quality characteristics of Zea mays

IntroductionThe zinc micronutrient fertilizers have a critical impact on the grain productivity and quality attributes of maize. However, the low use-efficiency issues of the applied Zn-fertilizers are required to be addressed through the development of novel formulations and alternative application techniques.ObjectivesThis field study investigates the comparative impact of seed invigoration (including seed priming and coating) treatments with bulk zinc and ZnO nanoparticles (ZnONPs).MethodsThe two seed treatments with two different zinc sources at three different concentrations of 0, 20, and 40 mg L−1 each, for a total of ten treatments, were evaluated for vegetative growth, photosynthetic pigments, grain yield, and quality traits in Zea mays.ResultsThe total chlorophyll content was improved by ZnONPs seed priming at the V8 stage. However, there were plants that grew tall, bearing longer ears with bulk ZnSO4 and the untreated control. Yield-contributing factors like number of seeds per cob, and 1000-grain weight were marginally improved by ZnONPs treatment. Overall, only cob weight, starch, total soluble protein, and soil nutrient (N, P, K, and Zn) content were significantly enhanced by ZnONPs treatment. Furthermore, no negative effect was recorded on the soil microbiological and enzymatic activities seed treatment with both the zinc sources.ConclusionThe seed treatment, i.e. coating and priming with ZnONPs, did not significantly alter the grain yield, but the seed starch and total soluble protein content were improved.

Comparative toxic effect of bulk zinc oxide (ZnO) and ZnO nanoparticles on human red blood cells

Abstract Metal oxide nanoparticles (NPs) are a member of nanomaterials family that have been produced on a large scale and their toxicity affected by their high surface-to-volume ratio. The hemolytic toxic effects of metal oxide NPs may be completely different from those observed in their bulk counterparts. So, the main purpose of this research was to measure the difference between the hemolytic effects of ZnO (NPs and bulk) on isolated human red blood cells (RBCs). Hemolysis was measured after incubation of human RBCs with 0.01–1 mM of ZnO (bulk and NPs) for 6 h. For measurement of other variables, human RBCs were treated with 0.1 mM of ZnO (NPs and bulk) for 1, 2, and 3 h. Our results demonstrate that bulk ZnO did not show any toxic effects in the concentrations tested, while ZnO NPs caused toxic hemolytic effects through formation of ROS, lipid peroxidation, and glutathione depletion.

Proton-Ion Conductivity in Hexagonal Wurtzite-Nanostructured ZnO Particles When Exposed to a Reducing Atmosphere

Zinc oxide (ZnO), a direct wide band gap semiconductor (≥3.30 eV), has widespread potential for applications in energy devices and related industries. The initial physical demonstration of ZnO in ceramic fuel cells (CFCs) gave a new view of developing high ionic conductivity for multifunctional semiconductor technology. However, in the present work, we successfully synthesized highly textured nanoparticles of ZnO using a hydrothermal method followed by sintering in a reducing atmosphere. The resultant ZnO materials as electrolytes showed efficient ionic conductivity (5.28 × 10−2 S cm−1) and an excellent power density of 520 mW cm−2 ± 5% at 550 °C for low-temperature ceramic fuel cells (LT-CFCs). The achievement of enhanced ionic conductivity without any external ions or cation doping in the CFC was anticipated, since there was a rare possibility of vacancies in the bulk ZnO structure to conduct oxygen ions or protons. Therefore, we found that laterally the surfaces of the ZnO nanoparticles could be textured to become oxygen-deficient when sintered in an H2 atmosphere, which suggests a special mechanism for effective ionic transport. Furthermore, experimental analyses such as SEM, XPS, UV–visible, and EIS methods were performed to analyze the changes in the structural properties and mechanism of ionic transport in ZnO nanoparticles. The presented work provides insights into a novel approach for developing high ionic conductivity in electrolytes in low-cost semiconductor oxides such as ZnO for energy storage and conversion devices.

Ultrafast modulation of a high harmonic generation in a bulk ZnO single crystal.

Optical modulation of high harmonic generation (HHG) is of fundamental interest in science and technology, which can facilitate understanding of HHG generation mechanisms and expand the potential optoelectronic applications. However, the current established works have neither shown the advanced modulation performance nor provided a deep understanding of modulation mechanisms. In this work, taking wurtzite zinc oxide (ZnO) single crystal as a prototype, we have demonstrated an all-optical intensity modulation of high-order HHG with a response time of less than 0.2 ps and a depth of more than 95%, based on the pump-probe configuration with two different pumping wavelengths. Besides the achieved excellent modulation performance, we have also revealed that the modulation dynamics in ZnO single crystal highly depend on the excitation conditions. Specifically, the modulation dynamics with the near-bandgap or above-bandgap excitation are attributed to the non-equilibrium interband carrier relaxations, while for mid-gap excitation, the modulation dynamics are dominated by the nonlinear frequency mixing process. This work may enhance the current understanding of the HHG modulation mechanism and enlighten novel device designs.