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Reduced graphene oxide (RGO) coupled CdS/ZnO core/shell nanorods have been synthesized using a soft chemical route. The photocatalytic activity of CdS/ZnO/RGO nanostructure has been examined for the degradation of methylene blue dye under solar irradiation at room temperature. The CdS/ZnO/RGO nanostructure exhibits five times enhanced photocatalytic activity as compared to CdS nanostructures which is attributed to the formation of heterojunction between the CdS and ZnO and its coupling with the reduced graphene oxide which facilitates the efficient transport of photogenerated charge carriers. Also, CdS/ZnO core/shell nanostructure exhibits very good photostability due to the presence of stable ZnO as cap layer. [ABSTRACT FROM AUTHOR]

P-type polyaniline (PANI)/n-type ZnO based heterojunction is fabricated and the effect of continuous ultraviolet (UV) exposure on its current–voltage (I–V) characteristics is investigated. The I–V characteristics of PANI/ZnO showed diode-like behavior under dark condition and its ideality factor and barrier height were obtained as 1.54 and 1.35 eV, respectively. For immediate UV exposure the diode showed photo-characteristics, however, during continuous UV exposure diode characteristics started to change with exposure time. After sufficient exposure time characteristics became stable and the ideality factor and barrier height after UV exposure were obtained as 7.94 and 0.92 eV, respectively. It is proposed that the permanent physical changes in PANI film during UV exposure are responsible to change the rectifying behavior. It is found that after 10 min of continuous exposure the PANI film stabilizes and the PANI/ZnO junction shows stable characteristics. [ABSTRACT FROM AUTHOR]

Abstract: ZnO nanostructures synthesized by chemical solution method were observed to exhibit a shape transition from nanoparticle to nanorod when the growth temperature was varied from 130 to 200°C. At the intermediate growth temperatures (150–170°C), nanoparticles start getting attached to form nanorods and exhibit enhanced strain and defects which seems to be due to the presence of interface between attached nanoparticles at these growth temperatures. The difference between valence band maxima and Fermi energy level at intermediate growth temperatures get increases which has been attributed to the enhancement of defects. [Copyright &y& Elsevier]

Abstract: In this paper we report the effect of deposition temperature on the structural and optical properties of ZnO thin films prepared by rf magnetron sputtering. The films grown at lower deposition temperatures were in a state of large compressive stress, whereas the films grown at higher temperature (450°C) were almost stress free. In the absorption spectra, the ZnO excitonic and the Zn surface plasmon resonance (SPR) peaks have been observed. A redshift in the optical band gap of ZnO films has also been observed with the increase in the deposition temperature. The shift in the band gap calculated from the size effect did not match with the observed shift values and the observed shift has been attributed to the compressive stress present in the films. [Copyright &y& Elsevier]

Abstract: ZnO and Co-doped ZnO thin films have been deposited on the sapphire substrate by ultrasonic assisted chemical vapor deposition technique. The films were annealed in vacuum at 450 °C. All the films were highly c-axis orientated and contained no impurity phase. The temperature dependence of the electrical conductivity has been measured in order to identify the dominant conduction mechanism. In the higher temperature region the dominance of thermally activated band conduction was observed whereas in the low temperature region the hopping conduction was found to dominate. The hopping conduction mechanism in the lower temperature range in the film was Mott''s Variable Range Hopping and not the Nearest Neighbor Hopping. The temperature region, where hopping conduction was dominant found to increase by Co doping in ZnO film. The localization length was found to be larger in the Co-doped ZnO film. [Copyright &y& Elsevier]

Hierarchical nanoflowers (NFs) of zinc oxide (ZnO) have been synthesized in the hexagonal wurtzite structure by a facile hydrothermal method. Polyaniline (PANI) has been prepared by the chemical oxidative polymerization method and incorporated with ZnO NFs by the chemisorption method. The potential of the synthesized nanostructures has been demonstrated for efficient photocatalytic degradation of methylene blue (MB) and photoelectrochemical water splitting. The PANI/ZnO nanocomposite has exhibited the enhanced photocatalytic activity which is ∼9 fold higher in comparison to pristine ZnO NFs and enhanced photocurrent density which is ∼16 fold higher than the ZnO photoanode. Importantly, ∼4 fold increment in the incident photon-to-current conversion efficiency (IPCE) is exhibited by PANI/ZnO, than that of ZnO photoanode. The remarkably enhanced photocatalytic and photoelectrochemical performance of PANI/ZnO nanocomposite is attributed to the availability of more interfacial sites facilitated by the hierarchical ZnO NFs, improved overall photoresponse due to its photosensitization with PANI and the resulting type-II heterojunction between them, which helps in the efficient separation of photogenerated charge carriers at the interface. A plausible reaction mechanism for the substantially improved performance of nanostructured PANI/ZnO towards MB degradation and water splitting has also been elucidated. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) coupled Zinc oxide (ZnO) nanocomposite has been synthesized by the chemisorption method and demonstrated its potential applications for photocatalytic degradation of methylene blue dye and photoelectrochemical (PEC) water splitting. A ∼7 fold enhancement in the photodegradation activity and ∼3 fold enhancement in the incident photon-to-electron conversion efficiency is observed for PANI/ZnO nanocomposite as compared to bare ZnO nanorods. The observed enhancement in the photocatalytic and photoelectrochemical activity is attributed to the photosensitization effect of visible light responsive PANI and the formation of type-II heterojunction between ZnO and PANI leading to the efficient separation and faster transfer of photoinduced charge carriers at the interface. A possible mechanism for the enhanced photocatalytic activity and photoelectrochemical water splitting for PANI/ZnO nanocomposite has been proposed. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we report fabrication and current–voltage characteristics of ZnO/α-NPD:F4-TCNQ based inorganic–organic hybrid junction. Current–voltage characteristics of hybrid junctions show diode like behavior. The effect of organic layer doping on the diode like characteristics of the junction has been investigated. The diode parameters viz. barrier height, ideality factor and rectification ratio have been calculated from the current–voltage semi-log plots. The improvement of diode parameters i.e. increase in rectification ratio and decrease in barrier height as well as improvement in ideality factor has been observed with doping. The improvement of the diode parameters has been attributed to the modification at ZnO/α-NPD interface. The current is also found to increase with the increase in doping concentration which has been attributed to the increased conductivity of α-NPD and interface barrier lowering after doping of α-NPD with F4-TCNQ. [ABSTRACT FROM AUTHOR]

Samarium-doped ZnO nanoparticles (1%, 3%, and 5%) were synthesized by a gel-combustion route and their application as an efficient photocatalyst for the degradation of Malachite green (MG) dye is demonstrated. These nanoparticles were characterized by spectroscopic techniques (UV-vis and photoluminescence), micrograph techniques (SEM and TEM), X-ray diffraction, and energy dispersive X-ray, in order to evaluate their optical and structural properties, particle size distribution, and morphology. The UV-vis spectroscopic studies indicated that Sm doping increased the visible light absorption ability of the Sm-doped ZnO nanoparticles and a redshift for the Sm-doped ZnO nanoparticles appeared when compared to ZnO nanoparticles. An enhancement in the optical absorption of the Sm-doped ZnO nanoparticles indicated that it can be used as an efficient photocatalyst under a visible light irradiation. The effect of tert-butyl alcohol and disodium salt of ethylenediaminetetraacetic acid as the scavengers in the photocatalysis process revealed that hydroxyl radicals (ṖOH) and holes (h+) were the reactive species responsible for the degradation of MG. The degradation mechanism has been proposed for the degradation of MG dye under the visible light irradiation. The recyclability of the Sm-doped ZnO nanoparticles for the MG dye degradation is also demonstrated. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of ZnO/MWCNT nanocomposite, and their potential application in photoelectrochemical (PEC) water splitting for hydrogen generation and photocatalytic degradation of methylene blue dye. For the synthesis of nanocomposite, ZnO nanoparticles were grown on the MWCNT surface by a simple chemical route. Microscopic studies showed that ZnO nanoparticles were well dispersed on the MWCNT surface and Raman study confirmed the intimate integration between ZnO and MWCNT. The nanocomposite exhibit higher photocatalytic degradation of methylene blue dye as compared to bare ZnO. The ZnO/MWCNT photoanode shows ∼5 times increase in photocurrent density in comparison to pure ZnO, at an applied potential of +1 V vs. Ag/AgCl. The enhanced photocurrent density of ZnO/MWCNT photoanode is attributed to the decrease in band-bending and effective interfacial electron transfer due to the conducting CNT scaffold, which facilitates the charge collection and charge transport in the ZnO/MWCNT nanocomposite. The Electrochemical impedance spectroscopy measurements confirmed the faster charge transfer at the interface in the case of nanocomposite. These results suggest substantial potential of ZnO/MWCNT nanocomposite in dye degradation and PEC water splitting applications. [ABSTRACT FROM AUTHOR]

A superhydrophobic coating material (PA-ZnO) with a static water contact angle (WCA)>160° has been synthesized by modifying zinc oxide (ZnO) nanoparticles with room temperature stable palmitic acid (PA). ZnO nanoparticles (size ~ 24 nm) with hexagonal wurtzite structure are prepared by hydrothermal method. FTIR study and TEM images confirms the grafting of palmitic acid on ZnO surface. This superhydrophobic nature of PA-ZnO has been attributed to the grafting of palmitic acid on ZnO surface which is confirmed by conducting the WCA measurement of PA-ZnO samples after heating at different temperatures. Surface morphology and roughness were observed as a function of temperature and it was observed that films morphology is changing to smoother films with low air entrapment for higher temperatures. On the same time the root mean square roughness (Rrms) is also reducing. It is observed that the superhydrophobic nature of PA-ZnO nanoparticles reduces with heating at higher temperatures and surface became like hydrophilic for heating temperature of ~ 230 °C. The decrease in the WCA is attributed to the thermal decomposition of palmitic acid from ZnO surface and the same has been confirmed by thermal analysis of PA and PA-ZnO samples. [ABSTRACT FROM AUTHOR]