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Background: Zinc oxide nanoparticles (ZnO NPs) are increasingly being used in industry., Objective: To evaluate the acute toxicology of ZnO NPs in Mice., Methods: ZnO NPs were intratracheally instilled into mice at different dose (200, 400, 800 μg/kg), which was 1, 2, or 4 times of accumulative intake in one week according to the threshold limit value. Acute toxicity was assessed by animal mortality, organ/body weight ratios, hematology, blood biochemistry, and histopathology as well as by the determination of cells, proteins, and lactate dehydrogenase activity in bronchoalveolar lavage fluid., Results: Exposure to ZnO NPs also resulted in bodyweight loss and a higher level of total cell number, total protein, and hydroxyproline content in BALF. Nitric oxide and malondialdehyde levels in the lung homogenates were also increased. In addition, inflammatory and hyperplastic changes in the lungs were observed., Conclusion: Threshold limit value (5 mg/m 3 ) may unfit for ZnO NPs.

A visible-light-active ZnO photocatalyst system in the presence of manganese ions (Mn/ZnO) was prepared via a simple and rapid approach. XRD, XPS, Raman scattering and UV-Vis DRS confirmed the manganese exists in multivalent forms (Mn(3+)/Mn(2+)) in the ZnO lattice, furthermore, ZnO light absorption is extended to the visible region. The photocatalytic activities of the catalysts were evaluated by measuring the photodegrading efficiency of 2,4-dichlorophenol (DCP) under visible light irradiation. With an optimal molar ratio of 5% in Mn/ZnO the highest rate photodegradation was achieved under the experimental conditions. We have characterized the separation and transfer behavior of the photogenerated charges in the visible region by means of surface photovoltage (SPV), surface photocurrent (SPC) and transient photovoltage (TPV) techniques. Based on the comprehensive investigation of the photovoltaic properties of Mn/ZnO photocatalyst, we illustrate the behavior of photogenerated charges have distinct effects on the photocatalytic activity. It is demonstrated that the incorporation of multivalent Mn in ZnO promoted the separation of photogenerated charges, inhibited the recombination of photogenerated carriers, and thus prolonged the charges lifetime to participate in the photocatalytic reaction, resulting in highly efficient photocatalytic activity, which is attributed to the formation of a strong electronic interaction between the multivalent Mn and ZnO.

With the purpose of high-efficiency separation of photo-generated charges and an improved photocatalytic performance, herein we report novel heterojunctions of p-type BiOBr and n-type ZnO constructed by loading amounts of BiOBr nanoflakes onto the surface of ZnO nanoflowers via a two-step hydrothermal/solvothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) are employed to characterize the as-synthesized nanomaterials. The results indicate that p–n heterojunctions formed between BiOBr and ZnO. When evaluated as a photocatalyst for methyl orange (MO) decolorization, BiOBr–ZnO-40 shows excellent photocatalytic activity, superior to that of pristine BiOBr and ZnO. Notably, the photochemical process for the MO decolorization is elucidated by reactive species trapping and hydroxyl radical quantification experiments, suggesting that ṖOH and O2Ṗ− are the main oxygen active species for BiOBr–ZnO heterojunctions in the MO decolorization. Moreover, the separation and transfer process of photo-generated charges at the surface or interface of the BiOBr–ZnO composites is also investigated by means of surface photovoltage (SPV). On the basis of experimental and theoretical results, the enhanced photocatalytic activity mechanism for the BiOBr–ZnO heterojunctions is proposed. The effective separation and transfer of photo-generated charges are responsible for an improved photocatalytic performance due to the existence of the interfacial electric field located between BiOBr and ZnO. [ABSTRACT FROM AUTHOR]

Abstract: Ag–ZnO nanorods with enhancement in UV light photoelectric gas-sensing response properties were synthesized by a facile two-step process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution electron microscope (HRTEM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The results revealed that Ag nanoparticles have decorated the surface of ZnO nanorods successfully. Formaldehyde (HCHO) sensing properties of sensors based on the Ag–ZnO nanorods were also investigated under 370nm light irradiation at room temperature with the assistance of surface photocurrent technique. It was found that the as-prepared Ag–ZnO nanorods showed excellent gas-sensing property that the gas response to 5 and 40ppm formaldehyde can reach to 9.4% and 119.8% under 370nm light irradiation at room temperature, respectively. To better understand the reason for the enhanced gas-sensing properties of Ag–ZnO, the separation and transfer behavior of the photogenerated charges were characterized by means of surface photovoltage and phase spectra. The results indicated that an electronic interaction between Ag and ZnO formed. Ag, as electron acceptor, effectively promoted the charge separation and transfer ability and, at the same time, inhibited the recombination of photogenerated charge carriers in ZnO, thus the Ag–ZnO nanorods had a high gas-sensing response to HCHO at room temperature. [Copyright &y& Elsevier]

Abstract: Fe-doped ZnO are fabricated by hydrothermal method. The influence of the annealing temperature on structural and photoelectric property was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (UV–vis DRS). Visible light-illumination room-temperature gas sensing to formaldehyde based on Fe-doped ZnO annealed at different temperatures was subsequently investigated by the surface photocurrent spectra and gas sensor characterization system, respectively. Accompanying with increasing annealing temperature from 400°C to 600°C, the response to formaldehyde was enhanced due to the increase in crystal quality and active sites on the surface of Fe-doped ZnO. However, when the annealing temperature goes over 700°C, the phase of ZnFe2O4 was observed from XRD pattern. The existence of ZnFe2O4 hindered the transfer of photo-generated carriers and decreased the amount of surface active sites. As a result, the photoelectric gas response for formaldehyde was weaken to some extent. Our results demonstrated that annealing temperature is a very important parameter in the determination of the sensitivity of photoelectric gas sensing based on Fe-doped ZnO. [Copyright &y& Elsevier]

Abstract: A visible-light-induced gas sensing element based on the heterostructures of CdS nanoparticles (NPs)/ZnO microcrystals has been successfully developed. Commercial ZnO microcrystals were coated with CdS nanoparticles by a sonochemical method to form the heterostructures. Compared with native CdS NPs, the as-obtained CdS NPs/ZnO showed enhanced photocurrent intensity. And the heterostructures-based element exhibited an excellent performance of photoelectric gas sensing to formaldehyde induced by visible-light. Moreover, the photocurrent intensity and sensitivity to formaldehyde were controllable by tuning the amount of CdS NPs attached on the surface of ZnO microcrystals. A possible explanation on the sensing mechanism has been proposed. In addition, the gas sensing element possessed good reproducibility. Our results demonstrate that the heterostructures of CdS NPs/ZnO is an efficient and promising material for visible-light-induced photoelectric gas sensors working at room temperature. [Copyright &y& Elsevier]

Abstract: A well-aligned nanorods array of ZnO was chemically grown on conductive ITO substrate at low temperature. The photogenerated charges at surface and interface were examined by surface photovoltage techniques based on both Kelvin probe and lock-in amplifier with dc bias. The photovoltage response bands related to band-to-band transition and bound excitons were discriminated. We demonstrated the spectrum-dependent transfer characteristic of photogenerated charges at the surface of ZnO nanorods array and the interface between ZnO and ITO. [Copyright &y& Elsevier]

Abstract: The photoelectric properties of ZnO microspheres, ZnO/Ag2S heterogeneous microspheres and Ag2S hollow microspheres were investigated systematically by surface photovoltage, transient photovoltage and surface photocurrent techniques. The ZnO/Ag2S heterostructure shows superior photoelectric properties in visible-light region compared with pure Ag2S. Transient photovoltage results reveal the separation processes of photo-generated charge carriers in the samples. The photoelectric ethanol sensing property induced by visible light for the ZnO/Ag2S heterostructure has been found, which should be valuable for the practical application of semiconductor gas sensors at room temperature. [Copyright &y& Elsevier]

Abstract: Carbon-doped ZnO microspheres were prepared through a facile hydrothermal process. The characterizations for the physicochemical properties of prepared samples under different calcination temperatures were carried out on X-ray diffraction analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, Raman spectroscopy and photocurrent spectra. C-doped ZnO under 500°C calcination exhibited the superior UV-activated room-temperature gas sensing activity for the detection of ethanol. The result of transient photovoltage suggested that the presence of sp2 carbon-type structures could improve the separation extent and restrain the recombination of the photoinduced electron–hole pairs, which increase the number of photoinduced oxygen ions on the surface of C-doped ZnO and enhancing of gas sensing activity. [Copyright &y& Elsevier]

Abstract: ZnO nanostructures materials with two-dimensional (2D) plate-like and three-dimensional (3D) flower-like morphologies have been synthesized via facile hydrothermal process. Scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD) have been used to characterize the samples. We have compared the surface photoelectric properties of flower-like ZnO with that of plate-like ZnO by means of surface photovoltage (SPV), field-induced surface photovoltage (FISPV), transient photovoltage (TPV) and surface photocurrent (SPC) techniques. Based on the photovoltage responses, the influence of the morphology on transfer characteristics of photogenerated charge carriers was discussed. The synthesized flower-like ZnO exhibited more efficient separation and transfer properties of photogenerated charge carriers than that of plate-like ZnO in the UV region due to the special flower-like hierarchical nanostructures. We have also evaluated the photocatalytic activity of the ZnO samples by photodegradation efficiency of RhB. The experiments demonstrated that RhB in aqueous solution was more efficiently photodegraded using flower-like ZnO than plate-like ZnO. The results also show the consistency between the carrier dynamics of photogenerated electron–hole pairs and photocatalytic activity. [Copyright &y& Elsevier]

Abstract: The ZnO nanorods with different diameters (∼300, 100, 40nm) and nanoparticles (∼6nm) were prepared, and their sensitivities to formaldehyde at room temperature were measured with and without the UV light irradiation (the intensity of light is 0.155mW/cm2). The XRD, TEM and SEM were utilized to examine the size of crystal and the morphology of material. The transient photovoltage and photoluminescence spectra were utilized to investigate the photoelectric properties of ZnO. The ZnO nanorods with diameter of ∼40nm own the highest response to formaldehyde with the UV light illumination than that of other samples. It is attributed to the large surface-to-volume ratio and high photo-generated charge efficiency, which are two key parameters to determine the gas response. The transient photovoltage results further demonstrate that the photo-generated charge efficiency of gas sensing element decreases as the surface-to-volume ratio increases (i.e. the size of crystal decreases). Therefore, the particles with highest sensitivity are of a certain size, neither the largest nor the smallest tested. Our work may supply a direction to fabricate the high performance gas sensor with UV light illumination. [Copyright &y& Elsevier]

Abstract: Zinc oxide nanorods were synthesized using a simple hydrothermal method. Formaldehyde-sensing characteristics were investigated without and with ultraviolet (UV) light irradiation. The gas response of nanorods to 110ppm formaldehyde with UV light irradiation was about 120 times higher than that without UV light irradiation. The detection limit was as low as 1.8ppm at room temperature. This high gas response under the UV light is attributed to photocatalytic oxidation. Furthermore, the significant improvements of the selectivity and recovery time were obtained after irradiating the nanorods with UV light. Our results demonstrated that applying UV light irradiation on the zinc oxide nanorods is an effective approach to achieve higher response and excellent selectivity to formaldehyde at room temperature. [Copyright &y& Elsevier]

In this work, the ZnO/Cu 2−x S composite material is prepared based on Al doped zinc oxide glass substrate and applied as counter electrode (CE) in quantum dot sensitized solar cell. The ZnO/Cu 2−x S CEs with the different Cu/S ratios of Cu 2−x S (2-x = 1.73–1.48) can be controlled by immersing Cu/ZnO in different concentrations of S2- solution. As a result, the solar cell fabricated by Cu 1.62 S/ZnO CE exhibits the best photoelectric conversion efficiency of 5.35% under 1 sun illumination, which is higher than that of Cu 1.62 S CE (4.22%). On the basis of the result of solid-state current density–voltage test and transient photovoltage measurements, the formation of p-n heterojunction and the improving electrocatalytic activity in composite CEs accounts for the enhanced photoelectric conversion efficiency. These results are coincide with the outcomes of the impedance analysis, Tafel polarization measurement and cyclic voltammetry test for the symmetrical cell. Consequentially, the ZnO/Cu 2−x S composite counter electrode is a promising material and the applications in solar cells. • Cu 2−x S/ZnO CEs are fabricated by in-situ inward etching method. • The QDSCs based on the Cu 1.62 S/ZnO CE achieves the PCE of 5.35%. • The formation of heterojunction accounts for the enhanced Photovoltaic performance. • The energy band structures of heterojunction is investigated in composite CE. • The Cu 2−x S/ZnO CEs show excellent stability in polysulfide electrolyte. [ABSTRACT FROM AUTHOR]

The polyporous SnO 2 -ZnO composites were synthesized by a water-bath method. The 3D center-hollow architecture and polyporous surface were also confirmed by field-emission scanning electron microscope (FE-SEM) and the Brunauer-Emmett-Teller (BET) specific surface area. Meanwhile, structural properties of SnO 2 -ZnO have been investigated by trans-mission electron microscopy (TEM) in 1 mol% SnO 2 -ZnO. The results of photoelectric gas-sensing demonstrated that the 1 mol% SnO 2 -ZnO gas-sensor exhibits not only an excellent response to formaldehyde (HCHO) but also superior sensitivity to low HCHO concentration. The response of 1 mol% SnO 2 -ZnO for the 1 ppm HCHO has reached 30% at room temperature (25 °C), and a detection limit of 0.1 ppm HCHO was achieved. The behavior of photogenerated charge is discussed in detail by means of the surface photovotage (SPV) and the transient photovoltage (TPV) techniques. It was found that the as-prepared 1 mol% SnO 2 -ZnO composites showed excellent separation and transfer efficiency of photogenerated charges carriers. What's more, the TPV spectrum analysis provides convincing evidence that the addition of excess SnO 2 is unfavorable to the transfer of electrons so as to reduce the sensitivity of SnO 2 -ZnO for target gas. This result offers a new window to explain the effect of SnO 2 concentration on the gas sensing characteristics, and provide more information on the fabricating composite materials for gas sensors. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) and iron doped zinc oxide (Fe/ZnO) nanoflowers were successfully synthesized via a simple hydrothermal process. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering, ultraviolet–visible (UV–vis) diffuse spectroscopy and scanning electron microscopy (SEM), and it was found that the dopant ions replaced some of the crystal lattice zinc ions, and furthermore, Fe 3+ and Fe 2+ ions coexist. Photocatalytic activities of the catalysts were assessed based on the degradation of rhodamine B (RhB) in aqueous solution under both UV and visible light irradiation ( λ > 420 nm), respectively. All Fe/ZnO samples showed enhanced photocatalytic activity under the irradiation of visible light. On the contrary, Fe/ZnO products displayed poorer performance than that of pure ZnO in the presence of UV light. This phenomenon can be attributed to the coexistence of Fe 3+ and Fe 2+ in the ZnO host. The photophysical mechanism of the UV and visible photocatalytic activity was investigated with the help of surface photovoltage (SPV) and PL measurements, respectively. The results indicated the influence of coexistence of Fe 3+ and Fe 2+ in ZnO host on the separation and transfer behavior of the photogenerated charges in the UV and visible regions, which are distinctly different: under the irradiation of UV light, the recombination of the photogenerated electrons and holes was promoted, whereas the separation and transfer of photogenerated electrons and holes was facilitated under the visible light irradiation. The detailed photocatalytic mechanism and the role of Fe on the photodegradation process are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The ZnO microrods modified by Cu2O nanocrystals were prepared in aqueous solution. ZnO microrods acted as carrier to immobilize the Cu2O nanocrystals and improved the recovery rate from solution. The ZnO/Cu2O compounds promoted the separation of photo-induced electrons and holes, which was proved by surface photovoltage spectroscopy (SPS). Therefore, the compounds showed an enhanced photocatalytic activity than pure ZnO and pure Cu2O under both UV–vis light and visible light. [Copyright &y& Elsevier]

Abstract: The ZnO nanorods (diameter of 40nm and 100nm) were modified with Ru(dcbpy)2(NCS)2 (RuN3), and their responses to formaldehyde were measured at room temperature. All the results showed that the responses to formaldehyde of modified ZnO were higher than that of bare ZnO; especially the responses of modified ZnO nanorods with diameter of 40nm–5ppm formaldehyde was about 200% higher than that of bare ZnO. The UV–vis absorption spectrum and transient photovoltage analysis showed that the high responses of modified ZnO mainly arose from the strong photocatalytic oxidizing effect induced by the increasing of the absorption and photo-generated electron–hole separation. Our results demonstrate that the modification of RuN3 is a promising approach on improving the formaldehyde responses of ZnO nanorods. [Copyright &y& Elsevier]