Tuning ZnO nanorods photoluminescence through atmospheric plasma treatments

Room temperature atmospheric plasma treatments are widely used to activate and control chemical functionalities at surfaces. Here, we investigated the effect of atmospheric pressure plasma jet (APPJ) treatments in reducing atmosphere (Ar/1 parts per thousand H-2 mixture) on the photoluminescence (PL) properties of single crystal ZnO nanorods (NRs) grown through hydrothermal synthesis on fluorine-doped tin oxide glass substrates. The results were compared with a standard annealing process in air at 300 degrees C. Steady-state photoluminescence showed strong suppression of the defect emission in ZnO NRs for both plasma and thermal treatments. On the other side, the APPJ process induced an increase in PL quantum efficiency (QE), while the annealing does not show any improvement. The QE in the plasma treated samples was mainly determined by the near band-edge emission, which increased 5-6 fold compared to the as-prepared samples. This behavior suggests that the quenching of the defect emission is related to the substitution of hydrogen probably in zinc vacancies (V-Zn), while the enhancement of UV emission is due to doping originated by interstitial hydrogen (H-i), which diffuses out during annealing. Our results demonstrate that atmospheric pressure plasma can induce a similar hydrogen doping as ordinarily used vacuum processes and highlight that the APPJ treatments are not limited to the surfaces but can lead to subsurface modifications. APPJ processes at room temperature and under ambient air conditions are stable, convenient, and efficient methods, compared to thermal treatments to improve the optical and surface properties of ZnO NRs, and remarkably increase the efficiency of UV emission. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

Nanoscale characterization of an all-oxide core-shell nanorod heterojunction using intermodulation atomic force microscopy (AFM) methods

The electrical properties of an all-oxide core-shell ZnO-Co3O4nanorod heterojunction were studied in the dark and under UV-vis illumination. The contact potential difference and current distribution maps were obtained utilizing new methods in dynamic multifrequency atomic force microscopy (AFM) such as electrostatic and conductive intermodulation AFM. Light irradiation modified the electrical properties of the nanorod heterojunction. The new techniques are able to follow the instantaneous local variation of the photocurrent, giving a two-dimensional (2D) map of the current-voltage curves and correlating the electrical and morphological features of the heterostructured core-shell nanorods

An early Little Ice Age brackish water invasion along the south coast of the Caspian Sea (sediment of Langarud wetland) and its wider impacts on environment and people

Caspian Sea level has undergone significant changes through time with major impacts not only on the surrounding coasts, but also offshore. This study reports a brackish water invasion on the southern coast of the Caspian Sea constructed from a multi-proxy analysis of sediment retrieved from the Langarud wetland. The ground surface level of wetland is >6 m higher than the current Caspian Sea level (at -27.41 m in 2014) and located >11 km far from the coast. A sequence covering the last millennium was dated by three radiocarbon dates. The results from this new study suggest that Caspian Sea level rose up to at least -21.44 m (i.e. >6 m above the present water level) during the early Little Ice Age. Although previous studies in the southern coast of the Caspian Sea have detected a high-stand during the Little Ice Age period, this study presents the first evidence that this high-stand reached so far inland and at such a high altitude. Moreover, it confirms one of the very few earlier estimates of a high-stand at -21 m for the second half of the 14th century. The effects of this large-scale brackish water invasion on soil properties would have caused severe disruption to regional agriculture, thereby destabilizing local dynasties and facilitating a rapid Turko-Mongol expansion of Tamerlane’s armies from the east.N Ghasemi (INIOAS), V Jahani (Gilan Province Cultural Heritage and Tourism Organisation) and A Naqinezhad (University of Mazandaran), INQUA QuickLakeH project (no. 1227) and to the European project Marie Curie, CLIMSEAS-PIRSES-GA-2009-24751

Dye adsorption on TiO2 electrodes studied using modulated photocurrent measurements

An in-situ modulated photocurrent technique to study kinetics of dye adsorption and to determine binding constants of dye molecules on the TiO 2 surface is presented. An AC-photocurrent signal is measured, when a TiO2 electrode is in contact with the dye bath, containing an inert salt for increased conductivity, upon excitation with on/off modulated light. This method provides relatively rapid results and is very useful for comparative studies. Organic dyes (D149, D5, D35) and ruthenium complexes (N719, Z907, black dye) were investigated and the effect of a coadsorbant in the dye bath (deoxycholic acid) was also analyzed. © 2013 Elsevier B.V. All rights reserved

The 100 most-cited articles on malaria: a bibliometric analysis

Purpose: The use of citation analysis to identify the first 100 articles on malaria offers unique insights into understanding the disease and subsequent follow-up treatment innovations over time. In this study, the 100 most-cited articles on malaria were analyzed, and key studies were highlighted. Design/methodology/approach: The data of the most-cited articles for the period of four decades were extracted from the Web of Science database. The search terms malaria, plasmodium infection and remittent fever were used to identify the related articles for the study. Findings: The preliminary data of the 100 most-cited articles were recorded and analyzed. The total number of retrieved articles was 55,517. Dondrop and colleagues wrote the most-cited articles focusing on a new treatment for falciparum malaria resistant to existing medications. The author, with the most publications, was N. J. White. The most-cited articles on malaria were published in 35 journals. The USA had published most of the influential articles, while the Mahidol Oxford Tropical Medicine Research Unit was the leading institute active in malaria research. The experimental method was the most frequent method used by the most-cited articles. There was a significant relationship between the number of authors, the presence of the corresponding author on Research Gate, the availability of the full text of the article on Research Gate, the impact factor of the journal in which the article was published and the international collaboration of authors and the number of citations on malaria. The most influential authors, countries, institutes, journals and articles were specified. Most of the notable articles on malaria were published in journals with high impact factors. A group of journals was introduced as the core journals. Originality/value: It was found that having co-authors, the presence of the corresponding author on Research Gate, the availability of the full text of the article on Research Gate, the impact factor of the journal in which the article was published and international collaboration contributed to the publication of high-quality scientific products. Updated information on malaria is needed to present and expand the screening strategies to improve health and reduce burden of malaria. © 2021, Emerald Publishing Limited

A new design for electrospinner collecting device facilitates the removal of small diameter tubular scaffolds and paves the way for tissue engineering of capillaries

Electrospinning is a technique widely used for tissue engineering. Despite hurdles, electrospun vascular tissue scaffolds has shown great promise in in vitro studies. One problem is the removal of tubular scaffolds from a electrospinning collection device with no unwanted crumpling or tearing, especially for small diameter scaffolds. To tackle this problem we designed a collection device for simple removal of the scaffold from the collector while no chemical pretreatment was required. The scaffolds fabricated on this collecting device maintained their tubular structure and showed favorable surface properties, mechanical strength and biocompatibility. The device offers a new opportunity for tissue engineering researchers to fabricate tubular scaffolds from materials which have not been possible to date and help them improve the quality of synthesized scaffolds. © 2016 Elsevier Inc

Adaptive nanolaminate coating by atomic layer deposition

Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 degrees C (room temperature, RT), 200 degrees C, 300 degrees C, and 400 degrees C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 degrees C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 degrees C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 degrees C

Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions

Self-powered photodetectors operating in the UV-visible-NIR window made of environmentally friendly, earth abundant, and cheap materials are appealing systems to exploit natural solar radiation without external power sources. In this study, we propose a new p-n junction nanostructure, based on a ZnO-Co3O4 core-shell nanowire (NW) system, with a suitable electronic band structure and improved light absorption, charge transport, and charge collection, to build an efficient UV-visible-NIR p-n heterojunction photodetector. Ultrathin Co3O4 films (in the range 1-15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al2O3 buffer layer between ZnO and Co3O4 was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO-Al2O3-Co3O4 system at zero bias is 6 times higher compared to that of ZnO-Co3O4. The responsivity (R) and specific detectivity (D) of the best device were 21.80 mA W-1 and 4.12 × 1012 Jones, respectively. These results suggest a novel p-n junction structure to develop all-oxide UV-vis photodetectors based on stable, nontoxic, low-cost materials