Dec 2019, Volume 13 Issue 4

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    Timur Sh. ATABAEV, Anara MOLKENOVA

    Upconversion (UC) lanthanide nanomaterials have attracted enormous attention in the last two decades thanks to their unique ability to convert low-energy infrared photons into high-energy photons. In this mini-review, we briefly discussed the recent achievements related to the direct utilization of UC optical nanomaterials for photocatalysis and photovoltaic applications. In particular, selected examples of UC-containing devices/nanocomposites with improved performance were covered. In addition, we outlined some challenges and future trends associated with the widespread usage of UC nanomaterials.

    Liuxin YANG, Zhou CHEN, Jian ZHANG, Chang-An WANG

    Heterostructure is an effective strategy to facilitate the charge carrier separation and promote the photocatalytic performance. In this paper, uniform SrTiO3 nanocubes were in-situ grown on TiO2 nanowires to construct heterojunctions. The composites were prepared by a facile alkaline hydrothermal method and an in-situ deposition method. The obtained SrTiO3/TiO2 exhibits much better photocatalytic activity than those of pure TiO2 nanowires and commercial TiO2 (P25) evaluated by photocatalytic water splitting and decomposition of Rhodamine B (RB). The hydrogen generation rate of SrTiO3/TiO2 nanowires could reach 111.26 mmol·g−1·h−1 at room temperature, much better than those of pure TiO2 nanowires (44.18 mmol·g−1·h−1) and P25 (35.77 mmol·g−1·h−1). The RB decomposition rate of SrTiO3/TiO2 is 7.2 times of P25 and 2.4 times of pure TiO2 nanowires. The photocatalytic activity increases initially and then decreases with the rising content of SrTiO3, suggesting an optimum SrTiO3/TiO2 ratio that can further enhance the catalytic activity. The improved photocatalytic activity of SrTiO3/TiO2 is principally attributed to the enhanced charge separation deriving from the SrTiO3/TiO2 heterojunction.


    Nitrogen-doped titanium dioxide (N/TiO2) nanophotocatalysts were successfully synthesized in the presence of environmentally benign nitrogen dopant source, guanidinium chloride, by the sol–gel method. The effect of calcination temperature (300–600 °C) on their physicochemical properties was investigated by means XRD, XPS, FESEM, HRTEM, Raman spectroscopy, UV-vis DRS, PL and BET. Moreover, their photocatalytic activities were evaluated against rhodamine B (RhB) degradation under direct sun light. Results showed that the crystal phase of spheroidal N/TiO2 nanoparticles was changed from anatase (300 °C) to rutile (600 °C) via an intermediate anatase/rutile (A/R) mixed phase (400–500 °C), and the RhB photodegradation performance was increased with the decrease of the calcination temperature. Notably, N/TiO2 prepared at 400 °C demonstrated the best degradation performance (99%) after 5 h irradiation. The enhanced performance with high photostability was mainly attributed to its higher surface area and pore volume, stronger light absorption, and lower recombination rate. Such nanomaterials have practical applications for environmental remediation.

    Yanlin JIA, Zhiyuan MA, Zhicheng LI, Zhenli HE, Junming SHAO, Hong ZHANG

    Despite the high specific capacities, the practical application of transition metal oxides as the lithium ion battery (LIB) anode is hindered by their low cycling stability, severe polarization, low initial coulombic efficiency, etc. Here, we report the synthesis of the NiO/Ni2N nanocomposite thin film by reactive magnetron sputtering with a Ni metal target in an atmosphere of 1 vol.% O2 and 99 vol.% N2. The existence of homogeneously dispersed nano Ni2N phase not only improves charge transfer kinetics, but also contributes to the one-off formation of a stable solid electrolyte interphase (SEI). In comparison with the NiO electrode, the NiO/Ni2N electrode exhibits significantly enhanced cycling stability with retention rate of 98.8% (85.6% for the NiO electrode) after 50 cycles, initial coulombic efficiency of 76.6% (65.0% for the NiO electrode) and rate capability with 515.3 mA·h·g−1 (340.1 mA·h·g−1 for the NiO electrode) at 1.6 A·g−1.

    Wei SUN, Rui ZHAO, Tian WANG, Ke ZHAN, Zheng YANG, Bin ZHAO, Ya YAN

    The homogenous dispersion of graphene in Al powders is a key challenge that limits the development of graphene-reinforced metal matrix composites with high performance. Here, uniform distribution of graphene oxide (GO) coated on flake Al powders were obtained by a simply stirring and ultrasonic treatment in the water/alcohol solution. The effect of water volume content on the formation of GO/Al composite powders was investigated. The results showed that GO adsorbed with synchronous reduction on the surface of Al powders, but when the water content was higher than 80% in the solution, Al powders were totally changed into Al(OH)3. With optimizing the water content of 60% in the solution, reduced GO was homogenously coated onto the surface of flake Al powders. The formation mechanism can be ascribed to the balance control between the liquid/solid interaction and the hydrolysis reaction.

    Jun ZHAO, Hang ZHAN, Hai Tao CHEN, Jian Nong WANG

    A floating-catalyst spray pyrolysis method was used to synthesize carbon nanotube (CNT) thin films. With the use of ammonium chloride as a pore-former and epoxy resin (EP) as an adhesive, CNT/EP composite films with a porous structure were prepared through the post-heat treatment. These films have excellent thermal insulation (0.029--0.048 W·m−1·K−1) at the thickness direction as well as a good thermal conductivity (40--60 W·m−1·K−1) in the film plane. This study provides a new film material for thermal control systems that demand a good thermal conductivity in the plane but outstanding thermal insulation at the thickness direction.


    Upconversion nanoparticles (UC NPs) in combination with plasmonic materials have great potential for cancer photothermal therapy. Recently, sodium holmium fluoride (NaHoF4) is being investigated for luminescence and magnetic resonance imaging (MRI) contrast agent. Here, we present successful synthesis of excellent quality doped NaHoF4 NPs for possible UC luminescence application and coated for possible photothermal therapy application. Synthesized NaHoF4 nanocrystals were doped with Yb/Er and coated with gold, gold/silica, silver and polypyrrole (PPy). XRD, XPS and TEM were used to determine structure and morphology of the NPs. Strong UC photoluminescence (PL) emission spectra were obtained from the NPs when excited by near-infrared (NIR) light at 980 nm. Cell viability and toxicity of the NPs were characterized using pancreatic and ovarian cancer cells with results showing that gold/silica coating produced least toxicity followed by gold coating.

    Qin LI, Min XING, Lan CHANG, Linlin MA, Zhi CHEN, Jianrong QIU, Jianding YU, Jiang CHANG

    In this study, a series of Er3+/Yb3+ co-doped Ca--Mg--Si glasses were prepared via the containerless processing. Phase composition and luminescent properties of the prepared materials were investigated through XRD and spectrometry, and bioactivity, biocompatibility and cytotoxicity were evaluated. The XRD patterns indicated that akermanite (AKT) ceramic powders were completely transformed into the glassy phase (AKT-G, EYA) through the containerless processing, which exhibit upconversion luminescence, and the luminescence intensity increased with the increase of the doping amount of Er3+ and Yb3+. High amount of Yb3+ doping and existence of Ca2+ in glasses resulted in more intensive red-light emission. The SEM observation, combined with EDS analysis, and cell culture experiments showed that the as-prepared glasses were nontoxic, biocompatible and bioactive. All these results demonstrated that the contai-nerless processing is a facile method for preparing homogeneous luminescent bioactive glasses. Furthermore, this luminescent Ca--Mg--Si glasses may be used as bone implant materials to study the in vivo distribution of degradation products of bone implants, which may be of great significance for the development and clinical application of new bone grafting materials.

    Junbo LI, Junting JIANG, Biyu ZHOU, Chaohuang NIU, Wendi WANG, Wenlan WU

    In this study, we describe a simple synthesis route to prepare triblock copolymers with disulfide-linkers, poly(ethylene glycol)-SS-poly(ε-caprolactone)-SS-poly(ethylene glycol) (PEG-SS-PCL-SS-PEG) for application in the reductively responsive release of doxorubicin (DOX). To synthesize PEG-SS-PCL-SS-PEG, two end-groups of PCL-diol were first modified with cystamine to introduce disulfide bonds and subsequently conjugated with PEG-NHS via carbodiimide chemistry. PEG-SS-PCL-SS-PEG fabricated into polymeric micelles with stable structure and different nanoscale sizes via adjusting the PCL chain length, showing obvious reductive responsiveness and fast drug release of encapsulated DOX in the presence of glutathione (GSH). Moreover, DOX-loaded PEG-SS-PCL-SS-PEG micelles exhibited higher therapeutic efficacy than reduction-insensitive PEG-b-PCL micelles in vitro. Thus, end-groups conjugation is a simple and straightforward strategy to introduce intelligent responsiveness in biocompatible block copolymers and improve their therapeutic efficacy.

    Wei WU, Fen ZHANG, Yu-Chao LI, Yong-Feng ZHOU, Qing-Song YAO, Liang SONG, Rong-Chang ZENG, Sie Chin TJONG, Dong-Chu CHEN

    The present work aimed at assessing the electrochemical behavior and the corrosion inhibition performance of Mg--Al-layered double hydroxide (LDH) coatings modified with methyltrimethoxysilane (MTMS) and cerium nitrate on AA5005 aluminum alloy. The chemical compositions and surface morphologies of the coatings were investigated by XRD, FT-IR and FE-SEM, while their corrosion resistance was evaluated by electrochemical and immersion tests. An optimum corrosion resistance of the composite coatings was obtained by adding 10−2 mol·L−1 cerium nitrate. An excess addition of cerium nitrate resulted in a loose structure and poor corrosion resistance of the coating. The corrosion mechanism of the composite coatings was proposed and discussed.

    Lei TANG, Tengfei LIU, Jinxu MA, Xiaowen ZHANG, Linan AN, Kepi CHEN

    Lead-free (K0.5−x/2Na0.5−x/2Lix)(Nb0.8Ta0.2)O3 (KNLNT) and (K0.49−x/2Na0.49−x/2- LixCa0.01)(Nb0.8Ta0.2)O3 (KNLNT-Ca) ceramics were prepared by a conventional ceramic processing. Structural analysis shows that the Ca2+ doping takes the A site of ABO3 perovskite and decreases the phase transition temperature. Property measurements reveal that as a donor dopant, the Ca2+ doping results in higher room-temperature dielectric constant, lower dielectric loss, and lower mechanical quality factor. In addition, the Ca2+ doping does not change the positive piezoelectric coefficient d33, but increases the converse piezoelectric coefficient d33* significantly. This is likely due to the increase in the relaxation, as well as the appearance of (CaNa/K--VNa/K′) defect dipoles.