Small

Zhang, Jian; Liu, Yongchang; Liu, Hui; Song, Yuzhu; Sun, Shengdong; Li, Qiang; Xing, Xianran; Chen, Jun

doi: 10.1002/smll.202000504pmid: 32510849

Transition metal chalcogenides have received great attention as promising anode candidates for sodium‐ion batteries (SIBs). However, the undesirable cyclic life and inferior rate capability still restrict their practical applications. The design of micro–nano hierarchitectures is considered as a possible strategy to facilitate the electrochemical reaction kinetics and strengthen the electrode structure stability upon repeated Na+ insertion/extraction. Herein, urchin‐like Fe3Se4 hierarchitectures are successfully prepared and developed as a novel anode material for SIBs. Impressively, the as‐prepared urchin‐like Fe3Se4 can present an ultrahigh rate capacity of 200.2 mAh g‐1 at 30 A g‐1 and a prominent capacity retention of 99.9% over 1000 cycles at 1 A g‐1, meanwhile, a respectable initial coulombic efficiency of ≈100% is achieved. Through the conjunct study of in situ X‐ray diffraction, ex situ X‐ray absorption near‐edge structure spectroscopy, as well as cyclic voltammetry curves, it is intriguing to reveal that the phase transformation from monoclinic to amorphous structure accompanied by the pseudocapacitive Na+ storage behavior accounts for the superior electrochemical performance. When paired with the Na3V2(PO4)3 cathode materials, the assembled full cell enables high energy density and decent cyclic stability, demonstrating potential practical feasibility of the present urchin‐like Fe3Se4 anode.

Li, Xiaodong; Wang, Ning; He, Jianjiang; Yang, Ze; Zhao, Fuhua; Wang, Kun; Huang, Changshui

doi: 10.1002/smll.201907013pmid: 32390323

This study proposes a one‐step method for growing superhydrophobic carbon nanothorn arrays (NTAs) directly on various substrates. The fabricated carbon material (named methyl‐substituted graphdiyne (MGDY)) comprises sp and sp2 carbons in a conjugated‐backbone form, as well as methyl groups introduced into the framework as hydrophobic‐enhanced functional groups. MGDY NTAs exhibit excellent hydrophobicity (contact angle ≥152°), substantial long‐period hydrophobic durability (the contact angle decreased by only 3.2% over 800 days), and acid/alkali tolerance. Owing to the enhanced durability and specific stability of carbon, a superhydrophobic interface can easily be constructed using MGDY NTAs, which can be applied to achieve successful long‐term metal‐corrosion protection and efficient oil–water separation.

Mukherjee, Prithvijit; Berns, Eric J.; Patino, Cesar A.; Hakim Moully, Elamar; Chang, Lingqian; Nathamgari, S. Shiva P.; Kessler, John A.; Mrksich, Milan; Espinosa, Horacio D.

doi: 10.1002/smll.202070144pmid: N/A

Liang, Yaru; Xiong, Xiang; Xu, Zhuijun; Xia, Qingbing; Wan, Liyang; Liu, Rutie; Chen, Guoxin; Chou, Shu‐Lei

doi: 10.1002/smll.202000030pmid: 32510816

Lithium‐ion batteries (LIBs) have been widely applied and studied as an effective energy supplement for a variety of electronic devices. Titanium dioxide (TiO2), with a high theoretical capacity (335 mAh g−1) and low volume expansion ratio upon lithiation, has been considered as one of the most promising anode materials for LIBs. However, the application of TiO2 is hindered by its low electrical conductivity and slow ionic diffusion rate. Herein, a 2D ultrathin mesoporous TiO2/reduced graphene (rGO) heterostructure is fabricated via a layer‐by‐layer assembly process. The synergistic effect of ultrathin mesoporous TiO2 and the rGO nanosheets significantly enhances the ionic diffusion and electron conductivity of the composite. The introduced 2D mesoporous heterostructure delivers a significantly improved capacity of 350 mAh g−1 at a current density of 200 mA g−1 and excellent cycling stability, with a capacity of 245 mAh g−1 maintained over 1000 cycles at a high current density of 1 A g−1. The in situ transmission electron microscopy analysis indicates that the volume of the as‐prepared 2D heterostructures changes slightly upon the insertion and extraction of Li+, thus contributing to the enhanced long‐cycle performance.

Zhao, Yan; Li, Chenglong; Jiang, Jizhong; Wang, Boming; Shen, Liang

doi: 10.1002/smll.202070146pmid: N/A

doi: 10.1002/smll.202070145pmid: N/A

Zhao, Yan; Li, Chenglong; Jiang, Jizhong; Wang, Boming; Shen, Liang

doi: 10.1002/smll.202001534pmid: 32419331

Tin(Sn)‐based perovskite is currently considered one of the most promising materials due to extending the absorption spectrum and reducing the use of lead (Pb). However, Sn2+ is easily oxidized to Sn4+ in atmosphere, causing more defects and degradation of perovskite materials. Herein, double‐sided interface engineering is proposed, that is, Sn‐Pb perovskite films are sandwiched between the phenethylammonium iodide (PEAI) in both the bottom and top sides. The larger organic cations of PEA+ are arranged into a perovskite surface lattice to form a 2D capping layer, which can effectively prevent the water and oxygen to destroy bulk perovskite. Meanwhile, the PEA+ can also passivate defects of iodide anions at the bottom of perovskite films, which is always present but rarely considered previously. Compared to one sided passivation, Sn‐Pb hybrid perovskite photodetectors contribute a significant enhancement of performance and stability, yielding a broadband response of 300–1050 nm, a low dark current density of 1.25 × 10–3 mA cm–2 at –0.1 V, fast response speed of 35 ns, and stability beyond 240 h. Furthermore, the Sn‐Pb broadband photodetectors are integrated in an infrared up‐conversion system, converting near‐infrared light into visible light. It is believed that a double‐sided passivation method can provide new strategies to achieving high‐performance perovskite photodetectors.

Xiang, Xianglin; Zhu, Bicheng; Cheng, Bei; Yu, Jiaguo; Lv, Hongjin

doi: 10.1002/smll.202001024pmid: 32484310

Herein, oil‐soluble CdS quantum dots (QDs) are first prepared through a solvent‐thermal process. Then, oil‐soluble CdS QDs are changed into water‐soluble QDs via ligand exchange using mercaptopropionic acid as capping agent at pH 13. The photocatalytic performance is investigated under the visible light irradiation using glycerol as sacrificial agent and Sn2+ as cocatalyst. No H2‐production activity is observed for oil‐soluble CdS QDs. Water‐soluble CdS QDs exhibit significantly enhanced hydrogen evolution rate. When the concentration of cocatalyst Sn2+ increases to 0.2 × 10−3 m, the rate of hydrogen evolution reaches 1.61 mmol g−1 h−1, which is 24 times higher than that of the pristine water‐soluble CdS QDs. The enhanced H2‐production efficiency is attributed to the adsorption of Sn2+ ions on the surface of CdS QDs that are further reduced to Sn atoms by photogenerated electrons. The in situ generated Sn atoms serve as photocatalytic cocatalyst for efficient hydrogen generation.

Gao, Theodore Z.; Sun, Zehao; Yan, Xuzhou; Wu, Hung‐Chin; Yan, Hongping; Bao, Zhenan

doi: 10.1002/smll.202000923pmid: 32500637

Supramolecular polymer sorting is a promising approach to separating single‐walled carbon nanotubes (CNTs) by electronic type. Unlike conjugated polymers, they can be easily removed from the CNTs after sorting by breaking the supramolecular bonds, allowing for isolation of electronically pristine CNTs as well as facile recycling of the sorting polymer. However, little is understood about how supramolecular polymer properties affect CNT sorting. Herein, chain stoppers are used to engineer the conformation of a supramolecular sorting polymer, thereby elucidating the relationship between sorting efficacy and polymer conformation. Through NMR and UV–vis spectroscopy, small‐angle X‐ray scattering (SAXS), and thermodynamic modeling, it is shown that this supramolecular polymer exhibits ring–chain equilibrium, and that this equilibrium can be skewed toward chains by the addition of chain stoppers. Furthermore, by controlling the stopper–monomer ratio, the sorting yield can be doubled from 7% to 14% without compromising the semiconducting purity (>99%) or properties of sorted CNTs.

Guo, Zhihe; Qin, Yingchun; Chen, Peizong; Hu, Jinliang; Zhou, Yi; Zhao, Xuyang; Liu, Zhiran; Fei, Yiyan; Jiang, Xiaoshun; Wu, Xiang

doi: 10.1002/smll.202000239pmid: 32510822

Whispering gallery mode (WGM) microresonators have been used as optical sensors in fundamental research and practical applications. The majority of WGM sensors are passive resonators that require complex systems, thereby limiting their practicality. Active resonators enable the remote excitation and collection of WGM‐modulated fluorescence spectra, without requiring complex systems, and can be used as alternatives to passive microresonators. This paper demonstrates an active microresonator, which is a microdisk laser in a hyperboloid‐drum (HD) shape. The HD microdisk lasers are a combination of a rhodamine B‐doped photoresist and a silica microdisk. These HD microdisk lasers can be utilized for the detection of label‐free biomolecules. The biomolecule concentration can be as low as 1 ag mL−1, whereas the theoretical detection limit of the biosensor for human IgG in phosphate buffer saline is 9 ag mL−1 (0.06 aM). Additionally, the biosensors are able to detect biomolecules in an artificial serum, with a theoretical detection limit of 9 ag mL−1 (0.06 aM). These results are approximately four orders of magnitude more sensitive than those for the typical active WGM biosensors. The proposed HD microdisk laser biosensors show enormous detection potential for biomarkers in protein secretions or body fluids.