An Overview and Future Perspectives of Rechargeable Zinc BatteriesShi, Yuchuan; Chen, Ye; Shi, Lei; Wang, Ke; Wang, Biao; Li, Long; Ma, Yaming; Li, Yuhan; Sun, Zehui; Ali, Wajid; Ding, Shujiang
doi: 10.1002/smll.202000730pmid: 32406195
Aqueous rechargeable zinc‐based batteries have sparked a lot of enthusiasm in the energy storage field recently due to their inherent safety, low cost, and environmental friendliness. Although remarkable progress has been made in the exploration of performance so far, there are still many challenges such as low working voltage and dissolution of electrode materials at the material and system level. Herein, the central tenet is to establish a systematic summary for the construction and mechanism of different aqueous zinc‐based batteries. Details for three major zinc‐based battery systems, including alkaline rechargeable Zn‐based batteries (ARZBs), aqueous Zn ion batteries (AZIBs), and dual‐ion hybrid Zn batteries (DHZBs) are given. First, the electrode materials and energy storage mechanism of the three types of zinc‐based batteries are discussed to provide universal guidance for these batteries. Then, the electrode behavior of zinc anodes and strategies to deal with problems such as dendrite and passivation are recommended. Finally, some challenge‐oriented solutions are provided to facilitate the next development of zinc‐based batteries. Combining the characteristics of zinc‐based batteries with good use of concepts and ideas from other disciplines will surely pave the way for its commercialization.
Constructing Pure Phase Tungsten‐Based Bimetallic Carbide Nanosheet as an Efficient Bifunctional Electrocatalyst for Overall Water SplittingChen, Jianpo; Ren, Bowen; Cui, Hao; Wang, Chengxin
doi: 10.1002/smll.201907556pmid: 32378323
Carbides are commonly regarded as efficient hydrogen evolution reaction (HER) catalysts, but their poor oxygen evolution reaction (OER) catalytic activities seriously limit their practical application in overall water splitting. Here, vertically aligned porous cobalt tungsten carbide nanosheet embedded in N‐doped carbon matrix (Co6W6C@NC) is successfully constructed on flexible carbon cloth (CC) as an efficient bifunctional electrocatalyst for overall water splitting via a facile metal–organic framework (MOF) derived method. The synergistic effect of Co and W atoms effectively tailors the electron state of carbide, optimizing the hydrogen‐binding energy. Thus Co6W6C@NC shows an enhanced HER performance with an overpotential of 59 mV at a current density of −10 mA cm−2. Besides, Co6W6C@NC easily in situ transforms into tungsten actived cobalt oxide/hydroxide during the OER process, serving as OER active species, which provides an excellent OER activity with an overpotential of 286 mV at a current density of −10 mA cm−2. The water splitting device, by applying Co6W6C@NC as both the cathode and anode, requires a low cell voltage of 1.585 V at 10 mA cm−2 with the great stability in alkaline solution. This work provides a feasible strategy to fabricate bimetallic carbides and explores their possibility as bifunctional catalysts toward overall water splitting.
DNA‐Driven Two‐Layer Core–Satellite Gold Nanostructures for Ultrasensitive MicroRNA Detection in Living CellsMeng, Dan; Ma, Wei; Wu, Xiaoling; Xu, Chuanlai; Kuang, Hua
doi: 10.1002/smll.202000003pmid: 32374494
It is a significant challenge to achieve controllable self‐assembly of superstructures for biological applications in living cells. Here, a two‐layer core–satellite assembly is driven by a Y‐DNA, which is designed with three nucleotide chains that hybridized through complementary sequences. The two‐layer core–satellite nanostructure (C30S5S10 NS) is constructed using 30 nm gold nanoparticles (Au NPs) as the core, 5 nm Au NPs as the first satellite layer, and 10 nm Au NPs as the second satellite layer, resulting in a very strong circular dichroism (CD) and surface‐enhanced Raman scattering. After optimization, the yield is up to 85%, and produces a g‐factor of 0.16 × 10−2. The hybridization of the target microRNA (miRNA) with the molecular probe causes a significant drop in the CD and Raman signals, and this phenomenon is used to detect the miRNA in living cells. The CD signal has a good linear range of 0.011–20.94 amol ngRNA−1 and a limit of detection (LOD) of 0.0051 amol ngRNA−1, while Raman signal with the range of 0.052–34.98 amol ngRNA−1 and an LOD of 2.81 × 10−2 amol ngRNA−1. This innovative dual‐signal method can be used to quantify biomolecules in living cells, opening the way for ultrasensitive, highly accurate, and reliable diagnoses of clinical diseases.
Ionic Exchange of Metal−Organic Frameworks for Constructing Unsaturated Copper Single‐Atom Catalysts for Boosting Oxygen Reduction ReactionMa, Shenghua; Han, Zheng; Leng, Kunyue; Liu, Xiaojie; Wang, Yi; Qu, Yunteng; Bai, Jinbo
doi: 10.1002/smll.202001384pmid: 32363699
Regulating the coordination environment of atomically dispersed catalysts is vital for catalytic reaction but still remains a challenge. Herein, an ionic exchange strategy is developed to fabricate atomically dispersed copper (Cu) catalysts with controllable coordination structure. In this process, the adsorbed Cu ions exchange with Zn nodes in ZIF‐8 under high temperature, resulting in the trapping of Cu atoms within the cavities of the metal−organic framework, and thus forming Cu single‐atom catalysts. More importantly, altering pyrolysis temperature can effectively control the structure of active metal center at atomic level. Specifically, higher treatment temperature (900 °C) leads to unsaturated Cu–nitrogen architecture (CuN3 moieties) in atomically dispersed Cu catalysts. Electrochemical test indicates atomically dispersed Cu catalysts with CuN3 moieties possess superior oxygen reduction reaction performance than that with higher Cu–nitrogen coordination number (CuN4 moieties), with a higher half‐wave potential of 180 mV and the 10 times turnover frequency than that of CuN4. Density functional theory calculation analysis further shows that the low N coordination number of Cu single‐atom catalysts (CuN3) is favorable for the formation of O2* intermediate, and thus boosts the oxygen reduction reaction.
Autonomous Biohybrid Urchin‐Like Microperforator for Intracellular Payload DeliverySun, Mengmeng; Liu, Qi; Fan, Xinjian; Wang, Yuefei; Chen, Weinan; Tian, Chenyao; Sun, Lining; Xie, Hui
doi: 10.1002/smll.201906701pmid: 32378351
A magnetic urchin‐like microswimmer based on sunflower pollen grain (SPG) that can pierce the cancer cell membrane and actively deliver therapeutic drugs is reported. These drug loaded microperforators are fabricated on a large scale by sequentially treating the natural SPGs with acidolysis, sputtering, and vacuum loading. The microswimmers exhibit precise autonomous navigation and obstacle avoidance in complex environments via association with artificial intelligence. Assemblies of microswimmers can further enhance individual motion performance and adaptability to complicated environments. Additionally, the experimental results demonstrate that microswimmers with nanospikes can accomplish single‐cell perforation for direct delivery under an external rotating magnetic field. Drugs encapsulated in the inner cavity of the microperforators can be accurately delivered to a specific site via remote control. These dual‐action microswimmers demonstrate good biocompatibility, high intelligence, precision in single‐cell targeting, and sufficient drug loading, presenting a promising avenue for many varieties of biomedical applications.
Freestanding 1T‐MnxMo1–xS2–ySey and MoFe2S4–zSez Ultrathin Nanosheet‐Structured Electrodes for Highly Efficient Flexible Solid‐State Asymmetric SupercapacitorsPan, Uday Narayan; Sharma, Vikas; Kshetri, Tolendra; Singh, Thangjam Ibomcha; Paudel, Dasu Ram; Kim, Nam Hoon; Lee, Joong Hee
doi: 10.1002/smll.202001691pmid: 32374526
Fabrication of hierarchical nanosheet arrays of 1T phase of transition‐metal dichalcogenides is indeed a critical task, but it holds immense potential for energy storage. A single‐step strategy is employed for the fabrication of stable 1T‐MnxMo1–xS2–ySey and MoFe2S4–zSez hierarchical nanosheet arrays on carbon cloth as positive and negative electrodes, respectively. The flexible asymmetric supercapacitor constructed with these two electrodes exhibits an excellent electrochemical performance (energy density of ≈69 Wh kg−1 at a power density of 0.985 kW kg−1) with ultralong cyclic stability of ≈83.5% capacity retention, after 10 000 consecutive cycles. Co‐doping of the metal and nonmetal boosts the charge storage ability of the transition‐metal chalcogenides following enrichment in the metallic 1T phase, improvement in the surface area, and expansion in the interlayer spacing in tandem, which is the key focus of the present study. This study explicitly demonstrates the exponential enhancement of specific capacity of MoS2 following intercalation and doping of Mn and Se, and Fe2S3 following doping of Mo and Se could be an ideal direction for the fabrication of novel energy‐storage materials with high‐energy storage ability.