Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and ...Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.展开更多
Zinc oxide uniform nanostructures with novel morphologies were synthesized through simple and fast ammonia based controlled precipitation method in aqueous media and in the absence of any additive. Selected batches of...Zinc oxide uniform nanostructures with novel morphologies were synthesized through simple and fast ammonia based controlled precipitation method in aqueous media and in the absence of any additive. Selected batches of the synthesized solids were characterized by SEM, XRD, FTIR and TG/DTA. FTIR analysis revealed that the morphology of nanostructures had little effect on their IR spectral profile of the synthesized material. The as-prepared, calcined and commercial ZnO nanostructures (ZnO-AP, ZnO-Cal and ZnO-Com) were then employed as gas sensors for the detection of ammonia, acetone and ethanol. ZnO-AP and ZnO-Cal based sensors showed superior and reproducible performance towards 1×10^-6 ammonia with gas response of 63.79% and 66.87% and response/recovery time of 13 and 3 s, respectively, at room temperature (29℃). This was attributed to the unique morphology and remarkable uniformity in shape and size of the synthesized nanostructures. In contrast, the ZnO-Com based sensor did not respond to ammonia concentration less than 200×10^-6. In addition, ZnO-Cal showed high selectivity to ammonia as compared to acetone and ethanol at room temperature. Moreover, the lowest detection limit was 1×10^-6, which demonstrates excellent ammonia sensing characteristics of the synthesized ZnO.展开更多
The robust porous architectures of active materials are highly desired for oxygen electrodes in lithium–oxygen batteries to enable high capacities and excellent reversibility. Herein, we report a novel three-dimensio...The robust porous architectures of active materials are highly desired for oxygen electrodes in lithium–oxygen batteries to enable high capacities and excellent reversibility. Herein, we report a novel three-dimensional replication strategy to fabricate three-dimensional architecture of porous carbon for oxygen electrodes in lithium–oxygen batteries. As a demonstration, ball-flower-like carbon microspheres assembled with tortuous hollow carbon nanosheets are successfully prepared by completely replicating the morphology of the nanostructured zinc oxide template and utilizing the polydopamine coating layer as the carbon source.When used as the active material for oxygen electrodes, the three-dimensional porous architecture of the prepared ballflower-like carbon microspheres can accommodate the discharge product lithium peroxide and simultaneously maintain the ions and gas diffusion paths. Moreover, their high degrees of defectiveness by nitrogen doping provide sufficient active sites for oxygen reduction/evolution reaction.Thus the prepared ball-flower-like carbon microspheres demonstrate a high capacity of 9,163.7 mA h g-1 and excellent reversibility. This work presents an effective way to prepare three-dimensional architectures of porous carbon by replicating the controllable nanostructures of transition metal oxide templates for energy storage and conversion applications.展开更多
基金Supported by the RU Top-Down under Grant No 1001/CSS/870019
文摘Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.
文摘Zinc oxide uniform nanostructures with novel morphologies were synthesized through simple and fast ammonia based controlled precipitation method in aqueous media and in the absence of any additive. Selected batches of the synthesized solids were characterized by SEM, XRD, FTIR and TG/DTA. FTIR analysis revealed that the morphology of nanostructures had little effect on their IR spectral profile of the synthesized material. The as-prepared, calcined and commercial ZnO nanostructures (ZnO-AP, ZnO-Cal and ZnO-Com) were then employed as gas sensors for the detection of ammonia, acetone and ethanol. ZnO-AP and ZnO-Cal based sensors showed superior and reproducible performance towards 1×10^-6 ammonia with gas response of 63.79% and 66.87% and response/recovery time of 13 and 3 s, respectively, at room temperature (29℃). This was attributed to the unique morphology and remarkable uniformity in shape and size of the synthesized nanostructures. In contrast, the ZnO-Com based sensor did not respond to ammonia concentration less than 200×10^-6. In addition, ZnO-Cal showed high selectivity to ammonia as compared to acetone and ethanol at room temperature. Moreover, the lowest detection limit was 1×10^-6, which demonstrates excellent ammonia sensing characteristics of the synthesized ZnO.
基金supported by grants from the National Natural Science Foundation of China (21673169 and 51672205)the National Key R&D Program of China (2016YFA0202602)+1 种基金the Research Start-Up Fund from Wuhan University of Technologythe Fundamental Research Funds for the Central Universities (WUT: 2017IB005, 2016IVA083)
文摘The robust porous architectures of active materials are highly desired for oxygen electrodes in lithium–oxygen batteries to enable high capacities and excellent reversibility. Herein, we report a novel three-dimensional replication strategy to fabricate three-dimensional architecture of porous carbon for oxygen electrodes in lithium–oxygen batteries. As a demonstration, ball-flower-like carbon microspheres assembled with tortuous hollow carbon nanosheets are successfully prepared by completely replicating the morphology of the nanostructured zinc oxide template and utilizing the polydopamine coating layer as the carbon source.When used as the active material for oxygen electrodes, the three-dimensional porous architecture of the prepared ballflower-like carbon microspheres can accommodate the discharge product lithium peroxide and simultaneously maintain the ions and gas diffusion paths. Moreover, their high degrees of defectiveness by nitrogen doping provide sufficient active sites for oxygen reduction/evolution reaction.Thus the prepared ball-flower-like carbon microspheres demonstrate a high capacity of 9,163.7 mA h g-1 and excellent reversibility. This work presents an effective way to prepare three-dimensional architectures of porous carbon by replicating the controllable nanostructures of transition metal oxide templates for energy storage and conversion applications.
