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  • Controllable synthesis of hollow porous silica nanotubes/CuS nanoplatform for targeted chemo-photothermal therapy
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-15
    Shanshan Huang, Ping’an Ma, Yi Wei, Ziyong Cheng, Bei Liu, Xiaoran Deng, Zhongxi Xie, Bengang Xing, Jun Lin

    Abstract The design and synthesis of multifunctional nanocarriers for efficient synergistic cancer therapy have drawn great research interests in recent years. In this work, a nanoplatform for chemo-photothermal therapy with targeting ligand was developed. Hollow porous structured silica nanotubes (SNTs) with controllable lengths decorated with CuS nanoparticles (NPs) on the surface as photothermal agents were prepared and further conjugated with lactobionic acid groups as a cancer cell target. SNTs with average lengths of 40, 55 and 150 nm were obtained and further functionalized as drug carriers. The smallest bifunctional SNTs with targeting groups show good biocompatibility and highest cellular uptake for HepG2 cells. The release of doxorubicin hydrochloride (DOX) from the SNTs was dependent on the pH of the buffer solution and 808-nm near infrared (NIR) light irradiation. The integration of photothermal therapy (PTT) of CuS NPs and chemotherapy of anticancer drug leads to a better tumor inhibition effect than the individual therapy alone in vitro and in vivo. These results demonstrate potential applications of the nanocomposites as vector for efficient chemo-photothermal therapy.

  • Reversible multiplexing for optical information recording, erasing, and reading-out in photochromic BaMgSiO 4 :Bi 3+ luminescence ceramics
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-14
    Youtao Ren, Zhengwen Yang, Yuehui Wang, Mingjun Li, Jianbei Qiu, Zhiguo Song, Jie Yu, Asad Ullah, Imran Khan

    Optical data storage technology has many advantages over the traditional solid-state and magnetic storage technology, such as low cost, multi-dimensional storage, and rewritable capability. Therefore, the optical data storage technology has been in increasing demand for optical storage media. Herein, the photochromic and photoluminescence properties of BaMgSiO4:Bi3+ ceramics were investigated. The BaMgSiO4:Bi3+ ceramics showed reversible photochromism from gray to pink upon alternating the 254 nm ultraviolet light and 532 nm laser irradiation. This is caused by the electron trapping and de-trapping in the oxygen vacancies of the BaMgSiO4:Bi3+ host. This reversible behavior of photochromism was applied to fabricate different patterns on the surface of the BaMgSiO4:Bi3+ ceramics, which exhibited the reversible dual-mode optical information recording and erasing abilities. The photoluminescence reversible modulation of the BaMgSiO4:Bi3+ ceramics was obtained through the photochromic phenomenon. This modification behavior of luminescence could be applied to read-out the recording information in the BaMgSiO4:Bi3+ ceramics. The coloration and bleaching of BaMgSiO4:Bi3+ ceramics were dependent on the time of light stimulation, which facilitated multiplexing encoding. This photoluminescence and photochromism multiplexing of the BaMgSiO4:Bi3+ ceramics enhanced the optical data storage capability.

  • An all-in-one supercapacitor working at sub-zero temperatures
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-14
    Yanfang Wang, Huimin Yuan, Youhuan Zhu, Zhiqiang Wang, Ziwei Hu, Jiwei Xie, Chengzhu Liao, Hua Cheng, Fucai Zhang, Zhouguang Lu

    具有低温工作性能是超级电容器应对特殊工作环境(高海拔/高纬度)的重要保障, 也有利于其在更多领域中的应用. 本文首先制备了一种可在低温下保持柔韧性和离子传导性能的碱性凝胶电解质, 并利用其制备了一种一体式超级电容器, 其可在零点温度以下(−36°C)仍具有稳定的工作能力.

  • Polymorphism and superconductivity in the V-Nb-Mo-Al-Ga high-entropy alloys
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-10
    Jifeng Wu, Bin Liu, Yanwei Cui, Qinqing Zhu, Guorui Xiao, Hangdong Wang, Siqi Wu, Guanghan Cao, Zhi Ren

    High-entropy alloys (HEAs) are the focus of current research for their diverse properties, including superconductivity and structural polymorphism. However, the polymorphic transition has been observed only in non-superconducting HEAs mostly under high pressure. Here we report the discovery of the superconductivity and temperature-driven polymorphism in (V0.5Nb0.5)3−xMoxAl0.5G0.5 (0.2 ≤ x ≤ 1.4) HEAs, which are of a single body-centered cubic (bcc) structure for x = 0.2 and a mixture of the bcc and A15 structures for higher x values. Upon annealing, the bcc structure undergoes a polymorphic transformation to the A15 one and all HEAs exhibit bulk superconductivity. For the sample with x = 0.2, the bcc polymorph is not superconducting down to 1.8 K, whereas the A15 polymorph has a superconducting transition temperature Tc of 10.2 K and estimated zero-temperature upper critical field Bc2(0) of 20.1 T, both of which are the highest among HEA superconductors. With increasing Mo content x, both Tc and Bc2(0) of the A15-type HEAs decrease, yet the large ratio of Bc2(0)/Tc signifies a disorder-induced enhancement of the upper critical field over a wide x range. The decrease in Tc is attributed to the decrease in both the electronic specific-heat coefficient and electron-phonon coupling strength. Furthermore, the valence electron count dependence of Tc, which is different from both the binary A15 and other structurally different HEA superconductors, suggests that Tc may be increased further by reducing the number of valence electrons. Our results not only uncover HEA superconductors of a new structural type, but also provide the first example of polymorphism-dependent superconductivity in HEAs.

  • Gold immunochromatographic assay for simultaneous detection of sibutramine and sildenafil in slimming tea and coffee
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-08
    Steven Suryoprabowo, Liqiang Liu, Hua Kuang, Gang Cui, Chuanlai Xu

    本文建立了一种方便、快速、高特异性的胶体金免疫层析检测方法, 用于同时检测减肥茶和咖啡中的西布曲明(SB)和西地那非(SID). 我们首先制备了胶体金纳米粒子(CG), 然后使之与单抗结合形成CG-mAb, 将CG-mAb与抗原分别喷涂到基板上形成结合垫和检测条带, 其中所需的抗原和抗体均由本实验室制备. 经过条件优化, 该方法在PBS缓冲溶液(0.01 mol L−1, pH 7.4), 以及三种减肥茶和三种咖啡样本中, 对SB和SID的消线值均为500 ng mL−1; 检测时间仅需5 min. 该方法对减肥茶和咖啡样本中SB和SID的快速检出具有实际应用价值.

  • Near-infrared absorbing 2D/3D ZnIn 2 S 4 /N-doped graphene photocatalyst for highly efficient CO 2 capture and photocatalytic reduction
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-08
    Yang Xia, Bei Cheng, Jiajie Fan, Jiaguo Yu, Gang Liu

    Abstract Hierarchical heterostructure photocatalysts with broad spectrum solar light utilization, particularly in the near-infrared (NIR) region, are emerging classes of advanced photocatalytic materials for solar-driven CO2 conversion into value-added chemical feedstocks. Herein, a novel two-demensional/three-demensional (2D/3D) hierarchical composite is hydrothermally synthesized by assembling vertically-aligned ZnIn2S4 (ZIS) nanowall arrays on nitrogen-doped graphene foams (NGF). The prepared ZIS/NGF composite shows enhancement in photothermal conversion ability and selective CO2 capture as well as solar-driven CO2 photoreduction. At 273 K and 1 atm, the ZIS/NGF composite with 1.0 wt% NGF achieves a comparably high CO2-to-N2 selectivity of 30.1, with an isosteric heat of CO2 adsorption of 48.2 kJ mol−1. And in the absence of cocatalysts and sacrificial agents, the ZIS/NGF composite with cyclability converts CO2 into CH4, CO and CH3OH under simulated solar light illumination, with the respective evolution rates about 9.1, 3.5, and 5.9 times higher than that of the pristine ZIS. In-depth analysis using in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) in conjunction with Kelvin probe measurements reveals the underlying charge transfer pathway and process from ZIS to NGF.

  • Programmable starving-photodynamic synergistic cancer therapy
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-08
    Leli Zeng, Kai Huang, Yilin Wan, Jing Zhang, Xikuang Yao, Chao Jiang, Jing Lin, Peng Huang

    Synergistic therapy combines multiple therapeutic approaches in one shot, thus could significantly amplify the therapeutic effects. However, how to design the desirable combination to maximize the synergistic effect is still a big challenge in cancer management. Herein, a nano-agent composed of glucose oxidase (GOx) and upconversion nanoparticles (UCNPs) were constructed for programmable starving-photodynamic synergistic cancer therapy through cascade glucose oxidation and hydrogen peroxide photolysis. In this nanoagent, GOx modulated the tumor glucose metabolism and consumed the β-D-glucose to produce H2O2. The glucose depletion induced “starvation” in cancer cells and caused cell death. Afterwards, the generated H2O2 was photolyzed by the invisible ultraviolet emission of UCNPs under near-infrared light excitation at 980 nm. The toxic hydroxyl radicals produced by photolysis further induced cancer cell death. Both in vitro and in vivo experiments confirmed that this starving-photodynamic synergistic therapy significantly outran any single therapy. This study paves an avenue to design programmable starving-photodynamic synergistic therapy for cancer management.

  • In situ assembly of MnO 2 nanosheets on sulfur-embedded multichannel carbon nanofiber composites as cathodes for lithium-sulfur batteries
    Sci. China Mater. (IF 5.636) Pub Date : 2020-01-07
    Jing Hu, Zhenyu Wang, Yu Fu, Linlong Lyu, Zhouguang Lu, Limin Zhou

    Rechargeable lithium-sulfur batteries have been regarded as the promising next generation energy storage system due to their overwhelming advantages in energy density. However, their practical implementations are hindered by severe capacity fading and low sulfur utilization, which are caused by polysulfide shuttling and the insulating nature of sulfur. Herein, sulfur-embedded porous multichannel carbon nanofibers coated with MnO2 nanosheets (CNFs@S/MnO2) are rationally designed and fabricated as cathode for lithium-sulfur battery. The high conductivity of porous multichannel carbon nanofibers facilitates the kinetics of electron and ion transport in the electrodes, and the porous structure encapsulates and sequesters sulfur in its interior void space to physically retard the dissolution of high-order polysulfides. Moreover, the MnO2 shell exhibits a combination of physical and chemical adsorption for high-order polysulfides, which could sequester polysulfides leaked from the carbon matrix after long-time charge/discharge cycles, resulting in enhanced cyclic stability. As a result, the electrode delivers a specific capacity of 1286 mA h g−1 at 0.1 C and 728 mA h g−1 at 3 C. And the capacity could remain 774 mA h g−1 after 600 cycles at 1 C.

  • Construction of layered h-BN/TiO 2 hetero-structure and probing of the synergetic photocatalytic effect
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-25
    Qun Li, Xinmei Hou, Zhi Fang, Tao Yang, Junhong Chen, Xiangzhi Cui, Tongxiang Liang, Jianlin Shi

    A novel layered hexagonal boron nitride/titanium dioxide (h-BN/TiO2) composite photocatalyst has been constructed by anchoring TiO2 nanoflakes on the surface of h-BN flakes via a solvothermal method. The morphology and dispersion of TiO2 can be tuned by controlling the amount of flake h-BN. Benefiting from the unique hetero-structure, the photocatalytic performance of the obtained composite toward rhodamine B (RhB) degradation is greatly enhanced, among which 12 wt% h-BN/TiO2 composites show 3.5 and 6.9 times higher degradation rate than the synthesized TiO2 and commercial TiO2 (P25), respectively, and an excellent cycling stability has also been obtained. Moreover, the first-principles calculation reveals the synergetic catalytic effect between TiO2 and h-BN flake, which is found to be responsible for the significantly enhanced photocatalytic performance of h-BN/TiO2 composites.

  • 3D ordered mesoporous cobalt ferrite phosphides for overall water splitting
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-17
    Yarong Huang, Menggang Li, Weiwei Yang, Yongsheng Yu, Sue Hao

    Developing low-cost and earth-abundant electrocatalysts with high performance for electrochemical water splitting is a challenging issue. Herein, we report a facile and effective way to fabricate three-dimension (3D) ordered mesoporous Co1−xFexP (x=0, 0.25, 0.5, 0.75) electrocatalyst. Benefiting from 3D ordered mesoporous pore channels and composition optimization, the Co0.75Fe0.25P exhibits excellent electrocatalytic activities with low overpotentials of 270 and 209 mV at 10 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, in the alkaline electrolyte along with a durable electrochemical stability. In addition, as both the cathode and anode, the Co0.75Fe0.25P also exhibits superior electrolysis water splitting performance with only an applied voltage of 1.63 V to attain a current density of 10 mA cm−2 without obvious decay for 18 h, indicating that the Co0.75Fe0.25P is an efficient electrocatalyst for overall water splitting.

  • Hierarchical iridium-based multimetallic alloy with double-core-shell architecture for efficient overall water splitting
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-26
    Jie Zhang, Zelin Chen, Chang Liu, Jun Zhao, Siliang Liu, Dewei Rao, Anmin Nie, Yanan Chen, Yida Deng, Wenbin Hu

    Abstract The overall water splitting for hydrogen production is an effective strategy to resolve the environmental and energy crisis. Here, we report a facile approach to synthesize the Ir-based multimetallic, hierarchical, double-coreshelled architecture (HCSA) assisted by oil bath reaction for boosting overall water splitting in acidic environment. The IrNiCu HCSA shows superior electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which are comparable to commercial Pt/C and better than IrO2. The IrNiCu HCSA exhibits remarkably catalytic efficiency as bifunctional catalyst for overall water splitting where a low cell voltage of 1.53 V is enough to drive a current density of 10 mA cm−2 and maintains stable for at least 20 h. The presented work for the design and synthesis of novel Ir-based multimetallic architecture paves the way for highperformance overall water splitting catalysis.

  • CALPHAD aided design of high entropy alloy to achieve high strength via precipitate strengthening
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-17
    Lin Guo, Ji Gu, Xing Gong, Song Ni, Min Song

    Abstract Designing high entropy alloys (HEAs) with high strength and excellent ductility has attracted extensive scientific interest. In the present work, the CALPHAD (calculation of phase diagrams) method was applied to guide the design of an (FeCoNi)92Al2.5Ti5.5 HEA strengthened by precipitation hardening. The grain size as well as the size and volume fraction of the precipitates was tailored via a thermomechanical process to optimize the mechanical properties. The uniformly dispersed nano-precipitates are Ni3(Al,Ti)-type precipitates with an L12 ordered structure presenting a fully coherent interface with the face-centered cubic (FCC) matrix. The yield strength of the alloy increases from 338.3 to 1355.9 MPa and the ultimate tensile strength increases from 759.3 to 1488.1 MPa, while the elongation maintains a reasonable value of 8.1%. The striking enhancement of strength is mainly caused by the precipitate’s hardening mechanism, which is evaluated quantitatively by various analytical models. The deformation-induced microbands and the coherent precipitates sheared by dislocations are the deformation and strengthening mechanisms contributing to the superior combination of ductility and strength in the present HEA. This investigation demonstrates that the CALPHAD method is beneficial to the design and optimization of HEAs.

  • Structure-induced hollow Co 3 O 4 nanoparticles with rich oxygen vacancies for efficient CO oxidation
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-22
    Zhijie Chen, Yajing Wang, Qiannan Liang, Liyu Chen, Weiteng Zhan, Yingwei Li

    Co3O4 has been considered as one kind of promising catalysts for the oxidation of CO. According to the Mars-van Krevelen mechanism, oxygen vacancies of Co3O4 play a significant role in catalytic activity. Herein, we report a novel structure-induced strategy to develop hollow Co3O4 with rich oxygen vacancies for efficient oxidation of CO. Through a reduction-oxidation pyrolysis process, the metal-organic frameworks (MOFs) precursor (i.e., ZIF-67) is transformed into H-Co3O4@H-C, in which hollow Co3O4 (H-Co3O4) nanoparticles (NPs) are embedded in hollow carbon (H-C) shell. The hollow Co3O4 NPs feature rich oxygen vacancies and finish a complete conversion of CO at 130°C, which is much lower than that of solid Co3O4 (the temperature of full CO conversion T100=220°C). Besides, the hollow carbon shell could also reduce the diffusion resistance during the oxidation process. Benefiting from the unique hollow structures, H-Co3O4@H-C even shows comparable activity to noble metal catalysts under high weight hourly space velocities (WHSVs) up to 240,000 mL h−1 gcat.−1. Furthermore, the H-Co3O4@H-C catalyst also shows good durability with only a slight decline after the reaction has been operated for 24 h.

  • Miracles of molecular uniting
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-16
    Qianqian Li, Zhen Li

    摘要 有机材料的宏观性质是分子聚集效应的客观体现, 不仅取决于单个分子的结构, 而且与整个分子的聚集形式密切相关. 通过对分子聚集态行为的有效调控, 科学家们发现了一些完全不同于单个分子特性的聚集态发光现象, 包括发光强度、 颜色、 形式以及激发过程的差异. 本文对这些有趣的聚集态发光材料进行了简要的综述, 系统分析了分子聚集模式和分子间相互作用对材料发光性能的影响, 并介绍了“MUSIC”的理念, 以音乐创作形象化材料设计, 强调分子聚集态行为的重要性.

  • A novel GSH responsive poly(alpha-lipoic acid) nanocarrier bonding with the honokiol-DMXAA conjugate for combination therapy
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-21
    Zhilin Liu, Zhaohui Tang, Dawei Zhang, Jiatan Wu, Xinghui Si, Na Shen, Xuesi Chen

    The key to improve the therapeutic efficacy for cancer treatment is to increase the delivery of drugs to tumors. For this purpose, tumor-microenvironment stimuli-responsive materials have great potential. Here, we prepared a new nanomedicine by bonding the conjugate of honokiol (HNK) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) to a glutathione (GSH)-responsive nanocarrier, poly(α-lipoic acid) polyethylene glycol. The nanomedicine would disintegrate due to the high level of GSH at the tumor sites, achieving the co-delivery of HNK and DMXAA, and realizing the combination therapy through close-range killing by HNK and long-range striking by DMXAA together. In a murine 4T1 breast tumor model, this strategy exhibited high tumor inhibition rate of 93%, and provided a valuable therapeutic choice for cancer therapy.

  • NiCoSe 2 /Ni 3 Se 2 lamella arrays grown on N-doped graphene nanotubes with ultrahigh-rate capability and long-term cycling for asymmetric supercapacitor
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-20
    Alan Meng, Tong Shen, Tianqi Huang, Guanying Song, Zhenjiang Li, Shuqin Tan, Jian Zhao

    In this paper, we report a one-step electro-deposited synthesis strategy for directly growing NiCoSe2/Ni3Se2 lamella arrays (LAs) on N-doped graphene nanotubes (N-GNTs) as advanced free-standing positive electrode for asymmetric supercapacitors. Benefiting from the synergetic contribution between the distinctive electroactive materials and the skeletons, the as-constructed N-GNTs@NiCoSe2/Ni3-Se2 LAs present a specific capacitance of ∼1308 F g−1 at a current density of 1 A g−1. More importantly, the hybrid electrode also reveals excellent rate capability (∼1000 F g−1 even at 100 A g−1) and appealing cycling performance (∼103.2% of capacitance retention over 10,000 cycles). Furthermore, an asymmetric supercapacitor is fabricated by using the obtained N-GNTs@NiCoSe2/Ni3Se2 LAs and active carbon (AC) as the positive and negative electrodes respectively, which holds a high energy density of 42.8 W h kg−1 at 2.6 kW kg−1, and superior cycling stability of ∼94.4% retention over 10,000 cycles. Accordingly, our fabrication technique and new insight herein can both widen design strategy of multicomponent composite electrode materials and promote the practical applications of the latest emerging transition metal selenides in next-generation high performance supercapacitors.

  • Two-dimensional conjugated polymers synthesized via on-surface chemistry
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-28
    Chenguang Li, Yongshuai Wang, Huanli Dong, Xiaotao Zhang, Wenping Hu

    二维共轭聚合物具有平面共轭结构和分子中离域的π电子体 系, 因而具有很强的平面内电荷传输能力, 表现出独特的物理和化 学性质, 在光学、电学、传感等领域具有广阔的应用前景. 但如何 获得分子结构及形貌符合二维特征、且尺寸满足制作电子器件需 求的分子非常困难, 是广大科研人员急需解决的问题. 本文总结了 界面合成二维共轭聚合物的方法, 讨论了这个领域目前面临的问 题和挑战, 并指出了未来的研究方向.

  • Recent progress and future prospects of sodium-ion capacitors
    Sci. China Mater. (IF 5.636) Pub Date : 2019-11-04
    Rui Jia, Guozhen Shen, Di Chen

    Abstract To satisfy the requirements for various electric systems and energy storage devices with both high energy density and power density as well as long lifespan, sodium-ion capacitors (SICs) consisting of battery anode and supercapacitor cathode, have attracted much attention due to the abundant resources and low cost of sodium source. SICs bridge the gap between the batteries and the supercapacitors, which can be used as competitive candidates for large-scale energy storage. In this review, the battery-type anode materials and the capacitor-type cathode materials are classified and introduced in detail. The advantages of various electrolytes including organic electrolytes, aqueous electrolytes and ion liquid electrolytes are also discussed sequentially. In addition, from the perspective of practical value, the presentations of the SICs at the current situation and the potential application in urban rail are displayed. Finally, the challenge, future research and prospects towards the SICs are put forward.

  • Biocompatible metal-free organic phosphorescent nanoparticles for efficiently multidrug-resistant bacteria eradication
    Sci. China Mater. (IF 5.636) Pub Date : 2019-11-07
    Shan Wang, Miao Xu, Kaiwei Huang, Jiahuan Zhi, Chen Sun, Kai Wang, Qian Zhou, Lingling Gao, Qingyan Jia, Huifang Shi, Zhongfu An, Peng Li, Wei Huang

    Abstract Organic phosphorescence materials with longlived triplet excitons that can highly generate active singlet oxygen (1O2) through the energy transfer with the molecular oxygen under photoexcitation, serve as highly efficient antibacterial agent. Herein, we report bright red-emissive organic phosphorescent nanoparticles (PNPs) based on a metal-free organic phosphor encapsulated with biocompatible block copolymers. The obtained PNPs with an ultra-small particle size of around 5 nm and a long emission lifetime of up to 167 µs showed effective 1O2 generation ability under visible light (410 nm) excitation in aqueous media, which can efficiently eradicate multi-drug resistant bacteria both in vitro and in vivo. This is the first demonstration of metal-free organic PNPs for photodynamic antimicrobial therapy, expanding the application scope of metal-free organic room temperature phosphorescent materials.

  • A low-temperature TiO 2 /SnO 2 electron transport layer for high-performance planar perovskite solar cells
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-18
    Nan Li, Jin Yan, Yuqian Ai, Ershuai Jiang, Liujin Lin, Chunhui Shou, Baojie Yan, Jiang Sheng, Jichun Ye

    Conventional titanium oxide (TiO2) as an electron transport layer (ETL) in hybrid organic-inorganic perovskite solar cells (PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperature-processed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO2/tin oxide (SnO2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO2/SnO2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO2/SnO2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO2 and SnO2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency (PCE) of 19.11% with an open-circuit voltage (Voc) of 1.15 V, a short-circuit current density (Jsc) of 22.77 mA cm−2, and a fill factor (FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO2/SnO2 ETL in the device, a high Voc of 1.18 V is achieved. It has been proven that the TiO2/SnO2 bilayer is a promising alternative ETL for high efficiency PSCs.

  • Bioinformation transformation: From ionics to quantum ionics
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-30
    Xiqi Zhang, Markus Antonietti, Lei Jiang

    传统的神经记录技术是基于从离子学到电子学的生物信息 转换, 虽被广泛研究, 但其在神经科学和脑科学领域进展很小. 最 近, 生物离子通道中的离子和分子流动被看作是量子限域超流体, 即离子和分子的量子态可作为生物信息载体, 其吸收光谱在太赫 兹范围内, 因此太赫兹光可以作为一个工具来实现生物信号的非 接触检测. 我们提出两种研究方案: 一种是利用太赫兹响应研究生 物体系的神经信号, 另一种是利用太赫兹响应研究人工体系的量 子限域离子超流体, 并为生物体系中神经信号的检测提供优化参 数. 通过把量子离子学引入生物信息学领域, 将为神经信号研究提 供一个新的技术手段, 推动神经科学和脑科学的发展, 并发展量子 离子学技术.

  • High-entropy alumino-silicides: a novel class of high-entropy ceramics
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-19
    Tongqi Wen, Honghua Liu, Beilin Ye, Da Liu, Yanhui Chu

    Abstract High-entropy ceramics (HECs) are gaining significant interest due to their huge composition space, unique microstructure, and adjustable properties. Previously reported studies focus mainly on HECs with the multi-cationic structure, while HECs with more than one anion are rarely studied. Herein we reported a new class of HECs, namely high-entropy alumino-silicides (Mo0.25Nb0.25Ta0.25V0.25)(Al0.5Si0.5)2 (HEAS-1) with multi-cationic and -anionic structure. The formation possibility of HEAS-1 was first theoretically analyzed from the aspects of thermodynamics and lattice size difference based on the first-principles calculations and then the HEAS-1 were successfully synthesized by the solid-state reaction at 1573 K. The as-synthesized HEAS-1 exhibited good single-crystal hexagonal structure of metal alumino-silicides and simultaneously possessed high compositional uniformity. This study not only enriches the categories of HECs but also will open up a new research field on HECs with multi-cationic and -anionic structure.

  • Ni 3 S 2 @S-carbon nanotubes synthesized using NiS 2 as sulfur source and precursor for high performance sodium-ion half/full cells
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-11
    Hongcheng He, Changmiao Chen, Zhi Chen, Pengchao Li, Shuangshuang Ding, Mengqiu Cai, Ming Zhang

    Nickle sulfides are attractive anode materials for sodium-ion batteries (SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2 (abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source. No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g-1 at 0.1 A g-1 after 100 cycles with exceptional capacity retention of 98.6%. Furthermore, they maintained excellent rate capability of 318 mA h g-1 even at elevated current density of 5 A g-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3 (NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte, enhanced surface ion storage performance (capacitive effect), and improved structural stability of electrode materials.

  • 5 nm NiCoP nanoparticles coupled with g-C 3 N 4 as high-performance photocatalyst for hydrogen evolution
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-24
    Bo Ma, Jinping Zhao, Zhenhua Ge, Yantao Chen, Zhihao Yuan

    Abstract Graphitic carbon nitride (g-C3N4) coupled with NiCoP nanoparticles with sizes around 5 nm have been fabricated via a controllable alcohothermal process. NiCoP is an excellent electron conductor and cocatalyst in photocatalytic reactions. The coupling between tiny NiCoP nanoparticles and g-C3N4 through in-situ fabrication strategy could be a promising way to eliminate the light screening effect, hinder the recombination of photo-induced charge carriers, and improve the charge transfer. The NiCoP/g-C3N4 nanohybrids exhibit an excellent photocatalytic activity in the hydrogen generation, with a significantly improved performance compared with original g-C3N4, CoP/g-C3N4 and Ni2P/g-C3N4, respectively. This study paves a new way to design transition metal phosphides-based photocatalysts for hydrogen production.

  • Post-annealing tailored 3D cross-linked TiNb 2 O 7 nanorod electrode: towards superior lithium storage for flexible lithium-ion capacitors
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-30
    Bohua Deng, Haoyang Dong, Tianyu Lei, Ning Yue, Liang Xiao, Jinping Liu

    Abstract TiNb2O7 anode materials (TNO) have unique potential for applications in Li-ion capacitors (LICs) due to their high specific capacity of ca. 280 mA h g−1 over a wide anodic Li-insertion potential window. However, their high-rate capability is limited by their poor electronic and ionic conductivity. In particular, studies on TNO for LICs are lacking and that for flexible LICs have not yet been reported. Herein, a unique TNO porous electrode with cross-linked nanorods tailored by post-annealing and its application in flexible LICs are reported. This binder-free TNO anode exhibits superior rate performance (~66.3% capacity retention as the rate increases from 1 to 40 C), which is ascribed to the greatly shortened ion-diffusion length in TNO nanorods, facile electrolyte penetration and fast electron transport along the continuous single-crystalline nanorod network. Furthermore, the TNO anode shows an excellent cycling stability up to 2000 cycles and good flexibility (no capacity loss after continuous bending for 500 times). Model flexible LIC assembled with the TNO anode and activated carbon cathode exhibits increased gravimetric and volumetric energy/power densities (~100.6 W h kg−1/4108.8 W kg−1; 10.7 mW h cm−3/ 419.3 mW cm−3), more superior to previously reported hybrid supercapacitors. The device also efficiently powers an LED light upon 180° bending.

  • SnSe 2 nanocrystals coupled with hierarchical porous carbon microspheres for long-life sodium ion battery anode
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-30
    Hui Chen, Zijie Mu, Yiju Li, Zhonghong Xia, Yong Yang, Fan Lv, Jinhui Zhou, Yuguang Chao, Jinshu Wang, Ning Wang, Shaojun Guo

    Abstract Tin selenides have been attracting great attention as anode materials for the state-of-the-art rechargeable sodium-ion batteries (SIBs) due to their high theoretical capacity and low cost. However, they deliver unsatisfactory performance in practice, owing to their intrinsically low conductivity, sluggish kinetics and volume expansion during the charge-discharge process. Herein, we demonstrate the synthesis of SnSe2 nanocrystals coupled with hierarchical porous carbon (SnSe2 NCs/C) microspheres for boosting SIBs in terms of capacity, rate ability and durability. The unique structure of SnSe2 NCs/C possesses several advantages, including inhibiting the agglomeration of SnSe2 nanoparticles, relieving the volume expansion, accelerating the diffusion kinetics of electrons/ions, enhancing the contact area between the electrode and electrolyte and improving the structural stability of the composite. As a result, the as-obtained SnSe2 NCs/C microspheres show a high reversible capacity (565 mA h g−1 after 100 cycles at 100 mA g−1), excellent rate capability, and long cycling life stability (363 mA h g−1 at 1 A g−1 after 1000 cycles), which represent the best performances among the reported SIBs based on SnSe2-based anode materials.

  • Lanthanide near-infrared emission and energy transfer in layered WS 2 /MoS 2 heterostructure
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-27
    Gongxun Bai, Yongxin Lyu, Zehan Wu, Shiqing Xu, Jianhua Hao

    Abstract Lanthanide ions have attracted great attention due to their distinct photonic properties. The optoelectronic properties and device performance are greatly affected by the interfacial coupling between the layered van der Waals heterostructure, fabricated with two or more transition metal dichalcogenide (TMD) layers. In this work, lanthanide-doped WS2/MoS2 layered heterostructures have been constructed through two synthesis steps. The doped thin films are highly textured nanosheets on wafers. Importantly, the as-prepared heterostructure exhibits efficient near-infrared emission in the range of the telecommunication window, owing to energy transfer between lanthanide ions in the two TMD layers. The use of the layered heterostructure allows the decrease of deleterious cross-relaxation due to homogeneous doping or concentration quenching. The energy transfer process was further elaborated in this work. The results suggest that lanthanide ions can effectively extend the emission band of TMD thin films and their heterostructures. The doped TMD heterostructure is highly favourable for constructing atomically thin near-infrared photonic devices.

  • Endosomal escape of protein nanoparticles engineered through humanized histidine-rich peptides
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-27
    Hèctor López-Laguna, Rafael Cubarsi, Ugutz Unzueta, Ramón Mangues, Esther Vázquez, Antonio Villaverde

    Abstract Poly-histidine peptides such as H6 (HHHHHH) are used in protein biotechnologies as purification tags, protein-assembling agents and endosomal-escape entities. The pleiotropic properties of such peptides make them appealing to design protein-based smart materials or nanoparticles for imaging or drug delivery to be produced in form of recombinant proteins. However, the clinical applicability of H6-tagged proteins is restricted by the potential immunogenicity of these segments. In this study, we have explored several humanized histidine-rich peptides in tumor-targeted modular proteins, which can specifically bind and be internalized by the target cells through the tumoral marker CXCR4. We were particularly interested in exploring how protein purification, self-assembling and endosomal escape perform in proteins containing the variant histidine-rich tags. Among the tested candidates, the peptide H5E (HEHEHEHEH) is promising as a good promoter of endosomal escape of the associated full-length protein upon endosomal internalization. The numerical modelling of cell penetration and endosomal escape of the tested proteins has revealed a negative relationship between the amount of protein internalized into target cells and the efficiency of cytoplasmic release. This fact demonstrates that the His-mediated, proton sponge-based endosomal escape saturates at moderate amounts of internalized protein, a fact that might be critical for the design of protein materials for cytosolic molecular delivery.

  • Converting biomass into efficient oxygen reduction reaction catalysts for proton exchange membrane fuel cells
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-16
    Xingdong Wang, Jinjie Fang, Xuerui Liu, Xiangqian Zhang, Qingqing Lv, Zhaoxiang Xu, Xuejiang Zhang, Wei Zhu, Zhongbin Zhuang

    It is urgent to develop low-cost but efficient oxygen reduction reaction (ORR) catalysts for the emerging clean energy devices of fuel cells based on proton exchange membrane. Herein, we report a facile method to covert the biomass of black fungus into an efficient ORR catalyst. The black fungus undergoes hydrothermal and pyrolysis processes to transform into carbon-based materials. The as-obtained BF-N-950 catalyst shows prominent ORR catalytic activities in both acidic and alkaline electrolytes with a half-wave potential reaching 0.77 and 0.91 V, respectively. A membrane electrolyte assembly was fabricated with the as-obtained BF-N-950 as the cathode catalyst which shows a high peak power density of 255 mW cm-2. The study shows the potential of converting conventional biomass into low-cost ORR catalyst, which is promising for the fuel cell technology.

  • First principles study on methane reforming over Ni/TiO 2 (110) surface in solid oxide fuel cells under dry and wet atmospheres
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-16
    Wenqiang Yang, Zhenbin Wang, Wenzhou Tan, Ranran Peng, Xiaojun Wu, Yalin Lu

    Understanding the carbon-tolerant mechanisms from a microscopic view is of special importance to develop proper anodes for solid oxide fuel cells. In this work, we employed density-functional theory calculations to study the CH4 reaction mechanism over a Ni/TiO2 nanostructure, which experimentally demonstrated good carbon tolerance. Six potential pathways for methane reforming reactions were studied over the Ni/TiO2(110) surface under both dry and wet atmospheres, and the main concerns were focused on the impact of TiO2 and Ni/TiO2 interface on CO/H2 formation. Our calculations suggest that the reaction between carbon and the interfacial lattice oxygen to form CO* is the dominant pathway for CH4 reforming under both dry and wet atmospheres, and intervention of steam directly to oxidize C* with its dissociated OH* group is less favorable in energy than that to wipe off oxygen vacancy to get ready for next C* oxidation. In all investigated paths, desorption of CO* is one of the most difficult steps. Fortunately, CO* desorption can be greatly promoted by the large heat released from the previous CO* formation process under wet atmosphere. H2O adsorption and dissociation over the TiO2 surface are found to be much easier than those over Ni, yttria stabilized zirconia (YSZ) and CeO2, which should be the key reason for the greatly depressed carbon deposition over Ni-TiO2 particles than traditional YSZ-Ni and CeO2-Ni anode. Our study presents the detailed CO* formation mechanism in CH4 reforming process over the Ni/TiO2 surface, which will benefit future research for exploring new carbon-tolerant solid oxide fuel cell anodes.

  • A facile grinding approach to embed red phosphorus in N,P-codoped hierarchical porous carbon for superior lithium storage
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-06
    Zhuzhu Du, Wei Ai, Chenyang Yu, Yujiao Gong, Ruyi Chen, Gengzhi Sun, Wei Huang

    Despite red phosphorous (P)-based anodes hold great promise for advanced lithium-ion batteries due to their high theoretical capacity, their practical application is hindered by poor electronic conductivity and drastic volume changes during charge-discharge processes. In order to tackle these issues, herein, a facile grinding method was developed to embed sub-micro- and nano-sized red P particles in N,P-co-doped hierarchical porous carbon (NPHPC). Such a unique structure enables P@NPHPC long-cyclic stability (1120 mA h g−1 after 100 cycles at 100 mA g−1) and superior rate performance (248 mA h g−1 at 6400 mA g−1). It is believed that our method holds great potential in scalable synthesis of P@carbon composites for future practical applications.

  • Controlling self-assembling and tumor cell-targeting of protein-only nanoparticles through modular protein engineering
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-19
    Eric Voltà-Durán, Olivia Cano-Garrido, Naroa Serna, Hèctor López-Laguna, Laura Sánchez-García, Mireia Pesarrodona, Alejandro Sánchez-Chardi, Ramón Mangues, Antonio Villaverde, Esther Vázquez, Ugutz Unzueta

    Modular protein engineering is suited to recruit complex and multiple functionalities in single-chain polypeptides. Although still unexplored in a systematic way, it is anticipated that the positioning of functional domains would impact and refine these activities, including the ability to organize as supramolecular entities and to generate multifunctional protein materials. To explore this concept, we have repositioned functional segments in the modular protein T22-GFP-H6 and characterized the resulting alternative fusions. In T22-GFP-H6, the combination of T22 and H6 promotes self-assembling as regular nanoparticles and selective binding and internalization of this material in CXCR4-overexpressing tumor cells, making them appealing as vehicles for selective drug delivery. The results show that the pleiotropic activities are dramatically affected in module-swapped constructs, proving the need of a carboxy terminal positioning of H6 for protein self-assembling, and the accommodation of T22 at the amino terminus as a requisite for CXCR4+ cell binding and internalization. Furthermore, the failure of self-assembling as regular oligomers reduces cellular penetrability of the fusions while keeping the specificity of the T22-CXCR4 interaction. All these data instruct how multifunctional nanoscale protein carriers can be designed for smart, protein-driven drug delivery, not only for the treatment of CXCR4+ human neoplasias, but also for the development of anti-HIV drugs and other pathologies in which CXCR4 is a relevant homing marker.

  • Revealing hidden supercooled liquid states in Al-based metallic glasses by ultrafast scanning calorimetry: Approaching theoretical ceiling of liquid fragility
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-28
    Qun Yang, Jing Huang, Xiao-Hui Qin, Fa-Xi Ge, Hai-Bin Yu

    铝基非晶合金具有密度低、强度高、耐腐蚀等诸多优异性 能; 然而, 铝基非晶合金形成能力差, 一般需要非常高的冷却速率, 这限制了铝基非晶合金应用. 玻璃形成理论认为形成能力与过冷 液体密切相关. 但在一般升温测量时, 铝基非晶合金不显示玻璃转 变或过冷液体, 而是直接变成晶态. 目前为止, 关于铝基非晶合金的 玻璃转变和过冷液体属性仍然是未知的. 本文采用超快速差热分 析方法(Flash DSC)使得升温速度达到10000 K s−1, 测量了20余种 常见铝基非晶合金的玻璃转变行为和过冷液体特征. 发现铝基非 晶合金普遍具有很高的液体脆度系数(m), 其中某些成分m>160, 已经接近理论上预测的脆度系数上限m∼175. 通过系统研究这些成 分的形成能力, 发现铝基非晶合金的玻璃形成能力与脆度系数成 反相关, 而且这种相关不是线性的. 只有m>100时, 降低m才会对玻 璃形成能力有明显影响; 相反, m>100的玻璃形成力普遍较弱, 而且 随m变化不显著. 因此, 过高的液体脆度系数可能是铝基非晶合金 形成能力差的一个重要原因.

  • High-temperature interface superconductivity in bilayer copper oxide films by pulsed laser deposition
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-06
    Jia-hao Den, Tian-shuang Ren, Le-le Ju, Hong-rui Zhang, Ji-rong Sun, Bao-gen Shen, Yan-wu Xie

    In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La2CuO4 and metallic La2−xSrxCuO4 (x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La2CuO4 and La2−xSrxCuO4 by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present 1.70 (the nominal Sr content in the targets). X-ray diffraction result indicates that our La2−xSrxCuO4 films with x≤0.60 have very high crystalline quality; but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x∼0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.

  • Two-dimensional organic single-crystalline p-n junctions for ambipolar field transistors
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-04
    Lu Wang, Cong Wang, Xixia Yu, Lei Zheng, Xiaotao Zhang, Wenping Hu

    Two-dimensional single-crystalline p-n junctions of organic semiconductors (pn-2DCOSs) show great potential in organic logic circuits due to their single crystal nature and excellent ambipolar charge transport. However, there are only few reports on pn-2DCOSs because it is difficult to obtain such highly ordered structure in pn-junction. Herein, a novel and effective solution processing method of secondary transfer technology based on the facile drop casting is used to fabricate devices of pn-2DCOSs based on C8-BTBT (p-type) and TFT-CN (n-type) successfully. The high-performance ambipolar field transistors based on such ultrathin pn-2DCOSs with several molecular layers thickness show well-balanced ambipolar charge transport behaviors with hole mobility as high as 0.43 cm2 V−1 s−1 and electron mobility up to 0.11 cm2 V−1 s−1, respectively. This work is essential for studying the intrinsic properties of organic p-n junctions and achieving high performance in organic complementary circuits.

  • High-efficiency colorful perovskite solar cells using TiO 2 nanobowl arrays as a structured electron transport layer
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-02
    Wenhui Wang, Yutong He, Limin Qi

    The rapid development of perovskite solar cells (PSCs) has stimulated great interest in the fabrication of colorful PSCs to meet the needs of aesthetic purposes in varied applications including building integrated photovoltaics and wearable electronics. However, it remains challenging to prepare high-efficiency PSCs with attractive colors using perovskites with broad optical absorption and large absorption coefficients. Here we show that high-efficiency PSCs exhibiting distinct structural colors can be readily fabricated by employing TiO2 nanobowl (NB) arrays as a nanostructured electron transport layer to integrate with a thin overlayer of perovskite on the NB arrays. A new crystalline precursor film based on lead acetate was prepared through a Lewis acid-base adduct approach, which allowed for the formation of a uniform overlayer of high-quality CH3NH3PbI3 crystals on the inner walls of the NBs. The PSCs fabricated using the TiO2 NB arrays showed angle-dependent vivid colors under light illumination. The resultant colorful PSCs exhibited a remarkable photovoltaic performance with a champion efficiency up to 16.94% and an average efficiency of 15.47%, which are record-breaking among the reported colorful PSCs.

  • Reversible enhanced upconversion luminescence by thermal and electric fields in lanthanide ions doped ferroelectric nanocomposites
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-02
    Er Pan, Gongxun Bai, Bingrong Ma, Lei Lei, Lihui Huang, Shiqing Xu

    Luminescence modification of lanthanide ions has attracted great attention due to its applications in sensing, colorful display, information transmission and anti-counterfeiting. Traditional methods of tuning fluorescence typically employ tuning compositions that are not conducive to the development of multi-environment detection and anti-counterfeiting. In this study, lanthanide ions doped ferroelectric nanocomposite was exploited with external stimuli. The upconversion luminescence modification was preformed via both the thermal and electric fields. The anti-thermal quenching phenomenon was observed in the prepared nano-composite, which could effectively enhance the upconversion luminescence of lanthanide ions. Based on the electromechanical softness of the ferroelectric lattice, exceptional luminescence modification was realized through electric polarization. The luminescence modifications by thermal and electric fields exhibited excellent reversibility and non-volatility. These results provide unique insights into the development of integrated stimulus responsive smart devices, colorful display and advanced multi-mode sensing materials.

  • Self-assembled nanostructured photosensitizer with aggregation-induced emission for enhanced photodynamic anticancer therapy
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-22
    Wenkun Han, Song Zhang, Rong Deng, Yangyang Du, Jingyu Qian, Xiaohua Zheng, Bin Xu, Zhigang Xie, Fei Yan, Wenjing Tian

    Three nanostructured photosensitizers with aggregation-induced emission (AIE) characteristics based on 2,3-bis(4′-(diphenylamino)-[1,1′-biphenyl]-4-yl) fumaronitrile (BDBF) were prepared for image-guided photodynamic therapy (PDT). BDBF was encapsulated with Pluronic F-127 (F127) to form usual spherical nanoparticles (F127@BDBF NPs) with a red fluorescence emission and 9.8% fluorescence quantum yield (FQY). Moreover, BDBF self-assembled into nanorods (BDBF NRs) in water. Compared with F127@BDBF NPs, BDBF NRs exhibited stronger orange fluorescence with a higher FQY of 23.3% and similar singlet oxygen (1O2) generation capability. BDBF NRs were further modified with F127 to form BDBF@F127 NRs with the same 1O2 generation ability as BDBF NRs. The three nanostructures exhibited a higher 1O2 production capacity than BDBF molecule in dissolved state and favorable stability in an aqueous solution as well as under physiological condition. In vitro photocytotoxicity experiments indicated that the three nanostructures inhibited tumor cell proliferation effectively. Therefore, to construct eligible nanostructures with a high FQY and 1O2 generation ability, simple self-assembly can serve as a valuable method to prepare photosensitizers with enhanced PDT.

  • Facile microwave approach towards high performance MoS 2 /graphene nanocomposite for hydrogen evolution reaction
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-29
    Shatila Sarwar, Amit Nautiyal, Jonathan Cook, Yifei Yuan, Junhao Li, Sunil Uprety, Reza Shahbazian-Yassar, Ruigang Wang, Minseo Park, Michael J. Bozack, Xinyu Zhang

    Low-cost, highly efficient catalysts for hydrogen evolution reaction (HER) are very important to advance energy economy based on clean hydrogen gas. Intensive studies on two-dimensional molybdenum disulfides (2D MoS2) have been conducted due to their remarkable catalytic properties. However, most of the reported syntheses are time consuming, complicated and less efficient. The present work demonstrates the production of MoS2/graphene catalyst via an ultra-fast (60 s) microwave-initiated approach. High specific surface area and conductivity of graphene delivers a favorable conductive network for the growth of MoS2 nanosheets, along with rapid charge transfer kinetics. As-produced MoS2/graphene nanocomposites exhibit superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of 62 mV, high cathodic currents and a Tafel slope of 43.3 mV/decade. Beyond excellent catalytic activity, MoS2/graphene reveals long cycling stability with a very high cathodic current density of around 1000 mA cm−2 at an overpotential of 250 mV. Moreover, the MoS2/graphene-catalyst exhibits outstanding HER activities in a temperature range of 30 to 120°C with low activation energy of 36.51 kJ mol−1, providing the opportunity of practical scalable processing.

  • Transition metal oxides for water oxidation: All about oxyhydroxides?
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-03
    Zhichuan J. Xu

    本文首先简单回顾了电解水的发展历史以及碱性和酸性条 件下电解水的电极材料特点. 对于碱性条件下的电解水, 电极材料 以过渡金属氧化物为主. 近年来, 人们对于过渡金属氧化物的析氧 反应开展了大量的研究, 特别关注钙钛矿、尖晶石、氧氢氧化物 等催化剂. 析氧反应条件苛刻, 一些氧化物催化剂会发生表面重构, 转化为过渡金属氧氢氧化物. 因此, 对这些氧化物来讲, 真正的催化 剂表面是一个氧氢氧化物的表面. 另一方面, 一些氧化物在析氧反 应中表现出较强的稳定性, 一般认为这些氧化物的表面不会发生 重构, 因而没有氧氢氧化物的生成. 一些已知的基于氧化物结构的 活性描述参数也对该观点提供了实验和理论支持. 最后, 本文提出 尚待回答的一个问题: 在析氧反应中是否所有的过渡金属氧化物 都会发生表面重构而生成一个氧氢氧化物的表面? 不管以上问题 的答案是什么, 该如何设计预催化剂实现重构后的高活性表面将 成为未来关注的热点之一.

  • Synthesis of ultrathin Co 2 AlO 4 nanosheets with oxygen vacancies for enhanced electrocatalytic oxygen evolution
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-13
    Jiayang Wang, Yongli Shen, Guijuan Wei, Wei Xi, Xiaoming Ma, Weiqing Zhang, Peipei Zhu, Changhua An

    In this work, we reported the synthesis of two-dimensional spinel structure of ultrathin Co2AlO4 nanosheets via dealloying and subsequent annealing processes. Oxygen vacancy defects were further introduced into Co2AlO4 nanosheets by a mild solvothermal reduction method, resulting in large electrochemical surface area and high active site densities, making the related Co atoms get electrons, and producing more empty orbitals. The positive charge of Co and Al atoms adjacent to the O vacancies in VO-rich Co2AlO4 reduced significantly, that is, more electrons are concentrated on the Co and Al atoms. Those electrons closed to the Fermi level have a promoting effect during the H2O activation. As a result, the obtained ultrathin Co2AlO4 nanosheets with oxygen vacancies show a low overpotential of 280 mV at the current density of 10 mA cm−2 and a small Tafel slope of 70.98 mV dec−1. Moreover, it also displays a remarkable stability in alkaline solution, which is superior to most of the reported Co3O4 electrocatalysts. The present work paves a new way to achieve efficient new energetic materials for sustainable community.

  • Quaternary chalcogenides: Promising thermoelectric material and recent progress
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-17
    Teng Wang, Taichang Huo, Hongchao Wang, Chunlei Wang

    热电材料利用Seebeck与Pelitier效应可以实现热能和电能的相互转化, 是颇具潜力的新型功能材料. 本文聚焦四元硫属化合物 Cu2BIICIVSe4 (其中, B位为Zn, Cd, Mn, Hg, C位为Si, Ge, Sn)的热电性能. 此类材料具有复杂的晶格结构, 导致其具有较低的晶格热导率, 是一类具有本征低热导的热电材料. 本文系统地总结了各类优化四元硫属化合物电学及热学的方法. 首先, 非化学计量法、 元素掺杂和η=1定理用于改善其电学性能. 然后, 纳米结构工程可用于进一步降低其热导率. 最后, 基于文中的论述, 我们提出通过多种实验方法的结合使用, 协同调控四元硫属化合物的电、 热性能, 以期进一步提高其热电性能.

  • Carbon nanotube: Controlled synthesis determines its future
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-09
    Shuchen Zhang, Liu Qian, Qiuchen Zhao, Zequn Wang, Dewu Lin, Weiming Liu, Yabin Chen, Jin Zhang

    Carbon nanotubes (CNTs) have received broad attention in the past decades due to their excellent physical and chemical properties and thus been regarded as a powerful candidate for future star-materials. Although various CNT products and their related applications have been demonstrated recently, their performance can hardly meet the researchers’ expectations compared with their theoretical properties. The current predicament is caused by the immature synthesis method, including the basic science and the producing technology. As the synthesis with controlled structures determines its future, this review summarizes the progress on the basic research and industrialization of CNTs in the past decades, including the fine structure control, aggregation status design and scale-up production, and further points out the way for the future development of CNTs combining with specific applications.

  • Ambient stable FAPbI 3 -based perovskite solar cells with a 2D-EDAPbI 4 thin capping layer
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-11
    Ya-Han Wu, Yong Ding, Xiao-Yan Liu, Xi-Hong Ding, Xue-Peng Liu, Xu Pan, Song-Yuan Dai

    Two-dimensional (2D) lead halide perovskite materials are emerging as one of promising light-absorbing materials in perovskite solar cells (PSCs), which show outstanding stability and defect passivation. Unfortunately, the power conversion efficiency (PCE) of those stable 2D PSCs is still far behind that of 3D PSCs. Herein, we reported a simple in-situ growth technique for the ethylenediamine lead iodide (EDAPbI4) layer on the top of formamidinium lead iodide (FAPbI3) layer. The rationally designed layered architecture of 2D-3D perovskite film could improve the PCE of the PSCs. In addition, benefiting from the high moisture resistance and inhibited ion migration of EDAPbI4 layer, the 2D-3D-based devices showed obviously enhanced long-term stability, keeping the initial PCE value for 200 h and 90% of its initial PCE even after 500 h.

  • Unique Cd 1−x Zn x S@WO 3−x and Cd 1−x Zn x S@WO 3−x /CoO x /NiO x Z-scheme photocatalysts for efficient visible-light-induced H 2 evolution
    Sci. China Mater. (IF 5.636) Pub Date : 2019-09-27
    Yanyan Li, Qinqin Ruan, Haifeng Lin, Yanling Geng, Jiefei Wang, Hui Wang, Yu Yang, Lei Wang

    Artificial Z-scheme photocatalytic systems have received considerable attention in recent years because they can achieve wide light-absorption, high charge-separation efficiency, and strong redox ability simultaneously. Nevertheless, it is still challenging to exploit low-cost and stable Z-scheme photocatalysts with highly-efficient H2 evolution from solar water-splitting so far. Herein, we report a novel all-solid-state Z-scheme photocatalyst Cd1−xZnxS@WO3−x consisting of Cd1−xZnxS nanorods coated with oxygen-deficient WO3−x amorphous layers. The Cd1−xZnxS@WO3−x exhibits an outstanding H2 evolution reaction (HER) activity as compared with Pt-loaded Cd1−xZnxS and most \({\bf{W}}{{\bf{O}}_{{3^{-}}}}\) and CdS-based photocatalysts, due to the generation of stronger reducing electrons through the appropriate Zn-doping in Cd1−xZnxS and the enhanced charge transfer by introducing oxygen vacancies (W5+/OVs) into the ultrathin WO3−x amorphous coatings. The optimal HER rate of Cd1−xZnxS@WO3−x is determined to be 21.68 mmol h−1 g−1, which is further raised up to 28.25 mmol h−1 g−1 (about 12 times more than that of Pt/Cd1−xZnxS) when Cd1−xZnxS@WO3−x is hybridized by CoOx and NiOx dual cocatalysts (Cd1−xZnxS@WO3−x/CoOx/NiOx) through in-situ photo-deposition. Moreover, the corresponding apparent quantum yield (AQY) at 420 nm is significantly increased from 34.6% for Cd1−xZnxS@WO3−x to 60.8% for Cd1−xZnxS@WO3−x/CoOx/NiOx. In addition, both Cd1−xZn−-S@WO3−x and Cd1−xZnxS@WO3−x/CoOx/NiOx demonstrate good stability towards HER. The results displayed in this work will inspire the rational design and synthesis of high-performance nanostructures for photocatalytic applications.

  • A low-dimension structure strategy for flexible photodetectors based on perovskite nanosheets/ZnO nanowires with broadband photoresponse
    Sci. China Mater. (IF 5.636) Pub Date : 2019-06-12
    Shalong Wang, Zhengfeng Zhu, Yousheng Zou, Yuhang Dong, Shuting Liu, Jie Xue, Leimeng Xu, Yuhui Dong, Jizhong Song

    Flexible photodetectors (PDs) have huge potential for application in next-generation optoelectronic devices due to their lightweight design, portability, and excellent large area compatibility. The main challenge in the construction of flexible PDs is to maintain the optoelectronic performance during repetitive bending, folding and stretching. Herein, flexible PDs based on ZnO nanowires (NWs) and CsPbBr3 nanosheets (NSs) were constructed by an integrated low-dimensional structure strategy. Benefiting from the flexibility of unique sheet and wire structures, the PDs were able to maintain excellent operational stability under various mechanical stresses. For example, the PDs exhibited no obvious changes in optoelectronic performance after bending for 1000 times. Additionally, the PDs exhibited an integrated broadband response ranging from ultraviolet to visible region due to the combination of the intrinsic light absorption capability of ZnO and CsPbBr3. The PDs demonstrated high responsivities of 3.10 and 0.97 A W−1 and detectivities of 5.57×1012 and 1.71×1012 Jones under ultraviolet and visible light irradiation, respectively. The proposed construction strategy for highly flexible and performance-integrated PDs shows great potential in future smart, wearable optoelectronic devices.

  • Pseudocapacitive sodium storage of Fe 1−x S@N-doped carbon for low-temperature operation
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-13
    Honghong Fan, Bowen Qin, Zhiwei Wang, Huanhuan Li, Jinzhi Guo, Xinglong Wu, Jingping Zhang

    Constructing potential anodes for sodium-ion batteries (SIBs) with a wide temperature property has captured enormous interests in recent years. Fe1−xS, a zero-band gap material confirmed by density states calculation, is an ideal electrode for fast energy storage on account of its low cost and high theoretical capacity. Herein, Fe1−xS nanosheet wrapped by nitrogen-doped carbon (Fe1−xS@NC) is engineered through a post-sulfidation strategy using Fe-based metal-organic framework (Fe-MOF) as the precursor. The obtained Fe1−xS@NC agaric-like structure can well shorten the charge diffusion pathway, and significantly enhance the ionic/electronic conductivities and the reaction kinetics. As expected, the Fe1−xS@NC electrode, as a prospective SIB anode, delivers a desirable capacity up to 510.2 mA h g−1 at a high rate of 8000 mA g−1. Additionally, even operated at low temperatures of 0 and −25°C, high reversible capacities of 387.1 and 223.4 mA h g−1 can still be obtained at 2000 mA g−1, respectively, indicating its huge potential use at harsh temperatures. More noticeably, the full battery made by the Fe1−xS@NC anode and Na3V2(PO4)2O2F cathode achieves a remarkable rate capacity (186.8 mA h g−1 at 2000 mA g−1) and an impressive cycle performance (183.6 mA h g−1 after 100 cycles at 700 mA g−1) between 0.3 and 3.8 V. Such excellent electrochemical performance is mainly contributed by its pseudocapacitive dominated behavior, which brings fast electrode kinetics and robust structural stability to the whole electrode.

  • In-situ liquid cell TEM investigation on assembly and symmetry transformation of Pt superlattice
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-12
    Junyu Zhang, Shi-Gang Sun, Hong-Gang Liao

    Two dimensional (2D) nanocrystal functional superlattices with a well controlled structure are of significant importance in photonic, plasmonic and optoelectronic applications and have been well studied, but it remains challenging to understand the formation mechanism and development pathway of the superlattice. In this study, we employed in-situ liquid cell transmission electron microscopy to study the formation of 2D superlattice and its local phase transition from hexagonal-to-square nanocrystal ordering. When colloidal nanocrystals flowed in the solution, long-range ordered hexagonal superlattice could be formed either through shrinking and rearrangement of nanocrystal aggregates or via nanocrystal attachment. As the nanocrystals’ shape transformed from truncated octahedral to cube, the local superlattice rearranged to square geometry. Moreover, our observations and quantitative analyses reveal that the phase transition from hexagonal to square mainly originates from the strong van der Waals interactions between the vertical (100) facets. The tracking of 2D cube superlattice formation in real-time could provide unique insights on the governing force of superlattice assembling and stabilization.

  • Loss compensation of surface plasmon polaritons in organic/metal nanowire heterostructures toward photonic logic processing
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-06
    Yuanchao Lv, Fa Feng Xu, Kang Wang, Yong Jun Li, Yong Sheng Zhao

    Surface plasmon polaritons (SPPs) are crucial for the development of next generation information and communication technologies. However, the ohmic losses inherent to all plasmonic devices seriously limit their practical application in on-chip photonic communications. Here, loss compensation of SPPs and their application in photonic logic processing was demonstrated in rationally designed organic/silver nanowire heterostructures. The heterostructures were synthesized by inserting silver nanowires (AgNWs) into crystalline organic microwires, which served as a microscale optical gain medium. These heterostructures with large organic/metal interfacial areas ensured the efficient energy transfer from excitons to SPPs. Gain for subwavelength SPPs in the heterostructure was achieved through stimulated emission of strongly confined SPPs. Furthermore, cascade gain was performed to realize basic nanoscale photonic devices, such as Boolean logic units. The results would pave an alternative avenue to incorporating SPP-enhanced devices into hybrid photonic circuitry.

  • Capillary shrinkage of graphene oxide hydrogels
    Sci. China Mater. (IF 5.636) Pub Date : 2019-12-05
    Changsheng Qi, Chong Luo, Ying Tao, Wei Lv, Chen Zhang, Yaqian Deng, Huan Li, Junwei Han, Guowei Ling, Quan-Hong Yang

    Conventional carbon materials cannot combine high density and high porosity, which are required in many applications, typically for energy storage under a limited space. A novel highly dense yet porous carbon has previously been produced from a three-dimensional (3D) reduced graphene oxide (r-GO) hydrogel by evaporation-induced drying. Here the mechanism of such a network shrinkage in r-GO hydrogel is specifically illustrated by the use of water and 1,4-dioxane, which have a sole difference in surface tension. As a result, the surface tension of the evaporating solvent determines the capillary forces in the nanochannels, which causes shrinkage of the r-GO network. More promisingly, the selection of a solvent with a known surface tension can precisely tune the microstructure associated with the density and porosity of the resulting porous carbon, rendering the porous carbon materials great potential in practical devices with high volumetric performance.

  • Surface composition-tunable octahedral PtCu nanoalloys advance the electrocatalytic performance on methanol and ethanol oxidation
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-11
    Fengling Zhao, Qiang Yuan, Bin Luo, Chaozhong Li, Fang Yang, Xiaotong Yang, Zhiyou Zhou

    The synthesis of surface composition-tunable Pt-based octahedral nanoalloys is key to unravel the structure-property relationship in fuel cells. Herein, we report a facile route to prepare composition-tunable PtCu octahedral nanoalloys by using halogen ions (Br- or/and I-) as composition modulators. Among these PtCu octahedral nanoalloys, Pt59Cu41 octahedron exhibits the highest catalytic activity and durability in alkaline solution. The specific activity/mass activity of Pt59Cu41 octahedron is 20.25 mA cm-2/3.24 A mg-1Pt, which is 6.64/5.3 times higher than commercial Pt black in 0.5 mol L-1 CH3OH, respectively. In the case of using ethanol (0.5 mol L-1) as fuel source, Pt59Cu41 octahedron shows much better catalytic activity, that is 34.84 mA cm-2/5.58 A mg-1Pt for specific activity/mass activity, which is 9.16/7.34 times higher than commercial Pt black, respectively. In situ Fourier transform infrared spectroscopy is employed to detect the intermediate species and products for methanol/ethanol oxidation reaction and a plausible mechanism is proposed to explain the improved activity and durability of Pt59Cu41 octahedron toward methanol/ethanol oxidation in alkaline medium.

  • Vibration uncoupling of germanium with different valence states lowers thermal conductivity of Cs 2 Ge 3 Ga 6 Se 14
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-25
    Ni Ma, Lin Xiong, Ling Chen, Li-Ming Wu

    The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterization of a new compound, Cs2Ge3Ga6Se14, with a unique anisotropic structure simultaneously containing Ge3+ and Ge2+ that adopt (Ge1)3+2Se6 dimer or (Ge2)2+Se6 octahedron, respectively. The thermal conductivity was measured to be 0.57–0.48 W m−1 K−1 from 323 to 773 K, the lowest value among all the known Ge containing compounds, approaching its glass limit according to the Cahill’s formulation. More importantly, we discover for the first time that the vibration uncoupling of Ge with different valence states hinders the effective thermal energy transport between the (Ge1)3+2Se6 dimer and (Ge2)2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor fi = sin(180 − β) × dGe−Q/li (i = A, B), with which a structure map of the Cs2Ge3M6Q14 family is given.

  • Bimetallic phosphides embedded in hierarchical P-doped carbon for sodium ion battery and hydrogen evolution reaction applications
    Sci. China Mater. (IF 5.636) Pub Date : 2019-08-06
    Linjun Huang, Xinxin Cao, Anqiang Pan, Jing Chen, Xiangzhong Kong, Yongqiang Yang, Shuquan Liang, Guozhong Cao

    Transition metal phosphides have been explored as promising active materials for sodium-ion batteries (SIBs) and hydrogen evolution reaction (HER) applications owing to their unique physical and chemical characteristics. However, they suffer from the drawbacks such as severe agglomeration, and sluggish reaction kinetics. Herein, bimetallic phosphides (Ni2P/ZnP4) embedded in P-doped carbon hierarchical microspheres are demonstrated with robust structural integrity, fast charge transfer, and abundant active sites. As expected, the optimally structured Ni2P/ZnP4 composite exhibits good electrochemical performance as an anode material in SIBs, including high specific capacity, good cycling stability and rate capability. Meanwhile, the Ni2P/ZnP4 composite also exhibits excellent electrocatalytic performance for HER with a small overpotential of 62 mV, a Tafel slope of 53 mV dec−1, as well as excellent stability.

  • Ni@RuM (M=Ni or Co) core@shell nanocrystals with high mass activity for overall water-splitting catalysis
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-19
    Shan Zhang, Fan Lv, Xiaoyan Zhang, Yelong Zhang, Haishuang Zhu, Huanhuan Xing, Zijie Mu, Jing Li, Shaojun Guo, Erkang Wang

    Developing efficient water-splitting electro-catalysts with high mass activity is in urgent need for large-scale sustainable production of hydrogen but, still remains as a big challenge. Herein, we report a one-pot method to fabricate a series of core@shell Ni@RuM (M=Ni or Co) nanocrystals (NCs) with Ni as the core and tunable RuM (M=Ni or Co) as the alloy shell for efficient water-splitting catalysis. Among these core@shell NCs, the obtained Ni@RuNi NCs exhibit the highest intrinsic activity for hydrogen evolution reaction (HER) and possess an outstanding mass activity of 1590 mA mgRu−1 at 0.07 V vs. reversible hydrogen electrode (RHE), which is 1.7 times higher than that of commercial Pt/C (950 mA mgPt−1). As for oxygen evolution reaction (OER), the prepared Ni@Ru0.4Co0.6 NCs with optimized shell composition achieve more enhanced mass activity of 270 mA mgRu−1 at 1.56 V vs. RHE, approaching three times higher than that of commercial RuO2 (89 mA mgRu−1). The superb mass activity of these Ni@RuM (M=Ni or Co) NCs can be attributed to their core@shell structure and modulated electronic structure through alloying with Ni or Co metal in the shell.

  • Advanced 3D nanohybrid foam based on graphene oxide: Facile fabrication strategy, interfacial synergetic mechanism, and excellent photocatalytic performance
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-31
    Xiaoyuan Zhang, Wenfeng Wei, Shan Zhang, Bianying Wen, Zhiqiang Su

    Herein, a unique nanohybrid foam was fabricated with titanium dioxide (TiO2)-carbon quantum dots (CQDs) nanoparticles intercalated between graphene oxide (GO) layers via a facile and low-cost solvothermal method. Compared with pure GO foam, the fabricated GO-TiO2-CQDs foam displayed high degradation rate towards methyl orange (MO), methylene blue (MB), and rhodamine B (RhB), respectively, under the Xenon lamp irradiation. The composite foam can be used for several times and remain a high degradation rate without structural damage. The photochemical property was attributed to the 3D porous structure of GO-TiO2-CQDs foam, in which ultrafine hydrogenated TiO2-CQDs nanoparticles were densely anchored on the GO sheets. This paper provides an efficient strategy to tune the charge transport and thus enhance the photocatalytic performance by combining the semi-conductive GO and quantum dots.

  • Non-stoichiometry in Ca 2 Al 2 SiO 7 enabling mixed-valent europium toward ratiometric temperature sensing
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-23
    Tao Hu, Yan Gao, Maxim Molokeev, Zhiguo Xia, Qinyuan Zhang

    Eu2+/Eu3+ mixed-valence couple co-doped material holds great potential for ratiometric temperature sensing owing to its different electronic configurations and electron-lattice interaction. Here, the correlation of nonstoichiometry in chemical composition, phase structures and luminescence propertis of Ca2Al2Si1−xO7:Eu is discussed, and controlled Eu2+/Eu3+ valence and tunable emission appear with decreasing Si content. It is found that the 2Ca2+ + Si4+ ↔ Eu2+ + Eu3+ + Al3+ cosubstitution accounts for the structural stability and charge balance mechanism. Benefiting from the diverse thermal dependent emission behaviors of Eu2+ and Eu3+, Ca2Al2Si1−xO7:Eu thermometer exhibits excellent temperature sensing performances with the maximum absolute and relative sensitivity being 0.024 K−1 (at 303 K) and 2.46% K−1 (at 443 K) and good signal discriminability. We propose that the emission quenching of Eu2+ is ascribed to 5d electrons depopulation through Eu2+/Eu3+ intervalence charge transfer state, while the quenching of Eu3+ comes from multi phonon relaxation. Our work demonstrates the potential of Ca2Al2Si1−xO7:Eu for noncontact optical thermometry, and also highlights mixed valence europium containing com pounds toward temperature sensing.

  • Advanced partial nucleation for single-phase FA 0.92 MA 0.08 PbI 3 -based high-efficiency perovskite solar cells
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-24
    Pengju Shi, Yong Ding, Cheng Liu, Yi Yang, Zulqarnain Arain, Molang Cai, Yingke Ren, Tasawar Hayat, Ahmed Alsaedi, Songyuan Dai

    To date, extensive research has been carried out, with considerable success, on the development of high-performance perovskite solar cells (PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixed-cation perovskite FAxMA1−xPbI3 (formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1−xPbI3 films contain a high percentage of MA+ and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-PbI2-DMSO (DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ∼30% for 80 days in standard atmospheric conditions.

  • Controlled one step thinning and doping of two-dimensional transition metal dichalcogenides
    Sci. China Mater. (IF 5.636) Pub Date : 2019-07-09
    Jie Ren, Changjiu Teng, Zhengyang Cai, Haiyang Pan, Jiaman Liu, Yue Zhao, Bilu Liu

    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and optical properties. Controlling the thickness and doping of 2D TMDCs are crucial toward their future applications. Here, we report an effective HAuCl4 treatment method and achieve simultaneous thinning and doping of various TMDCs in one step. We find that the HAuCl4 treatment not only thins thick MoS2 flakes into few layers or even monolayers, but also simultaneously tunes MoS2 into p-type. The effects of various parameters in the process have been studied systematically, and an Au intercalation assisted thinning and doping mechanism is proposed. Importantly, this method also works for other typical TMDCs, including WS2, MoSe2 and WSe2, showing good universality. Electrical transport measurements of field-effect transistors (FETs) based on MoS2 flakes show a big increase of On/Off current ratios (from 102 to 107) after the HAuCl4 treatment. Meanwhile, the subthreshold voltages of the MoS2 FETs shift from −60 to +27 V after the HAuCl4 treatment, with a p-type doping behavior. This study provides an effective and simple method to control the thickness and doping properties of 2D TMDCs, paving a way for their applications in high performance electronics and optoelectronics.

  • Designing excellent mid-infrared nonlinear optical materials with fluorooxo-functional group of d 0 transition metal oxyfluorides
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-24
    Junben Huang, Siru Guo, Zhizhong Zhang, Zhihua Yang, Shilie Pan

    Exploration of new infrared (IR) nonlinear optical (NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formidable challenge is to balance the contradiction between wide band gaps and large second harmonic generation (SHG) effects in IR NLO materials. In the present work, we proposed new kinds of NLO active units, d0 transition metal fluorooxo-functional groups for designing mid-IR NLO materials. By studying a series of d0 transition metal oxyfluorides (TMOFs), the influences of fluorooxo-functional groups with different d0 configuration cations on the band gap and SHG responses were explored. The results reveal that the fluorooxo-functional groups with different d0 configuration cations can enlarge band gaps in mid-IR NLO materials. The first-principles calculations demonstrate that the nine alkali/alkaline earth metals d0 TMOFs exhibit wide band gaps (all the band gaps > 3.0 eV), large birefringence Δn (> 0.07), and two W/Mo TMOFs also exhibit large SHG responses. Moreover, by comparing with other fluorooxo-functional groups, it is found that introducing fluorine into building units is an effective way to enhance optical performance. These d0 TMOFs with superior fluorooxo-functional groups represent a new exploration family of the mid-IR region, which sheds light on the design of mid-IR NLO materials possessing large band gap.

  • Ag 4 Hg(SeO 3 ) 2 (SeO 4 ): a novel SHG material created in mixed valent selenium oxides by in situ synthesis
    Sci. China Mater. (IF 5.636) Pub Date : 2019-10-22
    Xiao-Xue Wang, Xiao-Bao Li, Chun-Li Hu, Fang Kong, Jiang-Gao Mao

    Explorations of new second harmonic generation materials in Ag+-Hg2+/Bi3+-selenites systems afforded three new silver selenium oxides, namely, Ag4Hg(SeO3)2(SeO4) (1), Ag2Bi2(SeO3)3(SeO4) (2) and Ag5Bi(SeO3)4 (3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3D open framework with 4-, 6- and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4 (KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 eV respectively. Theoretical calculations disclose that compounds 2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.

Contents have been reproduced by permission of the publishers.
上海纽约大学William Glover