Cobalt(II)-dianthracene Frameworks: Assembly,Exfoliation and Properties

Metal-organic frameworks containing responsive organic linkers are attractive for potential applications in sensors and molecular devices. Herein we report three cobalt(II) phosphonates incorporating responsive dianthracene linkers, namely, Co₂(amp₂H₂)₂(H₂O)₄ ⋅ 6H₂O ( MDAF-1 ), Co₂(amp₂)(H₂O)₄ ⋅ 2H₂O ( MDAF-2 ) and Co(amp₂H₂) ⋅ 2H₂O ⋅ 0.5DMF ( MDAF-3 ), where amp₂H₄ is pre-photodimerized 9-anthrylmethylphosphonic acid. MDAF-1 shows a layer structure in which dinuclear Co₂(PO₃H)₂ units are inter-connected by dianthracene ligands. In MDAF-2 and MDAF-3 , inorganic chains of corner-sharing {CoO₄} (or {CoO₆}) and {PO₃C} are cross-linked by dianthracene ligands into 3D frameworks. All compounds underwent thermo-induced phase transitions, first the de-solvation and then the de-dimerization of dianthracene (as well as the release of the remaining solvent molecules for MDAF-2 and -3 ), associated with magnetic changes. MDAF-1 can be exfoliated into single-layer nanosheets in water which show light-triggered luminescent changes.     

光沉积制备pSi@CoOx高性能锂离子电池负极材料

选用微米级商业硅铝合金粉末作为原料,采用酸刻蚀、光沉积和后续的还原过程制备了 CoO_x纳米片原位包覆的多孔硅复合材料。探究了不同光沉积时间对pSi@CoO_x材料形貌及其储锂性能的影响。CoO_x纳米片的引入有效改善了材料的导电性并提高了材料的结构稳定性,即使在1 A·g~(-1)的电流密度下循环200圈后,pSi@CoO_x-5的比容量仍能保持774.2 mAh·g~(-1)。     

二维纳米片用于快速高效膜法气体分离

膜法气体分离作为一类低能耗先进分离技术, 在化工分离中具有广阔的应用前景. 然而商业气体分离膜在实际应用过程中存在选择性和渗透性此消彼长的问题. 以二维纳米片材料为膜构筑基元, 有望突破这一瓶颈. 最具代表性的二维纳米片膜材料当属石墨烯及其衍生物、 二维沸石分子筛、 层状双金属氢氧化物、 二维过渡金属硫化物、 Mxene、 二维共价有机骨架和金属有机骨架材料. 本文对这些二维材料在超薄气体分离膜领域的成果与进展进行介绍, 展现了各类材料在实际分离应用过程中的优势及弊端, 探讨了二维纳米片膜材料在气体分离领域的挑战与发展前景.     

A double quantum dot defined by top gates in a single crystalline InSb nanosheet

We report on the transport study of a double quantum dot (DQD) device made from a freestanding, single crystalline InSb nanosheet. The freestanding nanosheet is grown by molecular beam epitaxy and the DQD is defined by the top gate technique. Through the transport measurements, we demonstrate how a single quantum dot (QD) and a DQD can be defined in an InSb nanosheet by tuning voltages applied to the top gates. We also measure the charge stability diagrams of the DQD and show that the charge states and the inter-dot coupling between the two individual QDs in the DQD can be efficiently regulated by the top gates. Numerical simulations for the potential profile and charge density distribution in the DQD have been performed and the results support the experimental findings and provide a better understanding of fabrication and transport characteristics of the DQD in the InSb nanosheet. The achieved DQD in the two-dimensional InSb nanosheet possesses pronounced benefits in lateral scaling and can thus serve as a new building block for the developments of quantum computation and quantum simulation technologies.     

Synthesis of SiC/graphene nanosheet composites by helicon wave plasma

We report an approach to the rapid, one-step, preparation of a variety of wide-bandgap silicon carbide/graphene nanosheet(Si C/GNSs) composites by using a high-density helicon wave plasma(HWP) source. The microstructure and morphology of the Si C/GNSs are characterized by using scanning electron microscopy(SEM), Raman spectroscopy, x-ray diffraction(XRD), x-ray photoelectron spectroscopy(XPS), and fluorescence(PL). The nucleation mechanism and the growth model are discussed. The existence of Si C and graphene structure are confirmed by XRD and Raman spectra.The electron excitation temperature is calculated by the intensity ratio method of optical emission spectroscopy. The main peak in the PL test is observed at 420 nm, with a corresponding bandgap of 2.95 e V that indicates the potential for broad application in blue light emission and ultraviolet light emission, field electron emission, and display devices.     

基于核酸外切酶Ⅲ诱导的双重信号放大与MoS2纳米片荧光碎灭性质的核酸检测方法

将核酸外切酶Ⅲ诱导的双重信号放大技术与MoS2纳米片的荧光猝灭性质结合,构建了一种高灵敏高选择性的DNA检测方法.首先设计两条末端修饰荧光基团的探针核酸(HP1和HP2).由于两条探针核酸具有3'粘性末端,使其不会被核酸外切酶Ⅲ降解,因而被吸附于MoS2纳米片而猝灭其荧光.当目标DNA存在时,会促使核酸外切酶Ⅲ启动双重信号放大反应,并将探针核酸降解成大量的不能吸附于MoS2纳米片表面的荧光碎片.在优化条件下,目标DNA浓度在0.5~6.0 pmol/L范围内与荧光信号变化呈良好的线性关系,检出限为0.28 pmol/L.与单重信号放大技术相比,本方法极大改善了分析灵敏度和检出限,且具有良好的单碱基错配区分能力.     

介质和力场协同作用对纳米纤维素形貌结构的调控

纤维素是一种由直链多聚糖通过糖苷键连接而成的巨型线性高分子,纤维素分子链通过氢键紧密排列形成纤维素晶体.由于纤维素晶体具有优良的化学可修饰性和机械性能等优点,纳米化加工的纤维素可广泛应用于日常生活和工业生产的各个领域.本文主要介绍了本课题组在机械剪切力作用下,实现纤维素纳米化并同时进行亲水或疏水改性的研究进展,重点介绍了介质极性对纤维素分子链之间相互作用的影响,并通过改变分子链之间的相互作用来调控纳米化纤维素的形貌和亲、疏水性.提出机械外力和环境极性协同作用下,晶面导向剥离纤维素的理论.     

A DFT study on the healing of N‐vacancy defects in boron nitride nanosheets and nanotubes by a methylene molecule

In the present work, density functional theory calculations are used to investigate the healing mechanism of a N‐vacancy defect in boron nitride nanosheet (BNNS) or nanotube (BNNT) with a CH₂ molecule. The healing process starts with the chemisorption of CH₂ at the defect site, followed by its dehydrogenation over the surface. Next, a H₂ molecule is produced which can be easily released from the surface due to its small adsorption energy. For the dehydrogenation of CH₂ molecule over the defective BNNS or BNNT, the first C? H bond dissociation is the rate determining step. Our results indicate that the dehydrogenation of CH₂ over BNNS is both thermodynamically and kinetically more favorable than over BNNT. Besides, this study proposes a novel method for achieving C‐doped BNNSs and BNNTs. Given that the healing process proceeds without using a metal catalyst, therefore, no any purification is needed to remove the catalyst.     

Chemical Vapor Deposition of FeOCl Nanosheet Arrays and Their Conversion to Porous α‐Fe2O3 Photoanodes for Photoelectrochemical Water Splitting

FeOCl nanosheet arrays were deposited on fluorine‐doped tin oxide glass substrates through a chemical vapor deposition method and further converted to hematite porous nanosheet arrays. A much enhanced photocurrent was obtained for such hematite films, which was three times higher than that of a planar hematite film at 1.23 V versus a reversible hydrogen reference electrode.     

A sensitive fluorescence turn-on assay of bleomycin and nuclease using WS2 nanosheet as an effective sensing platform

As an important antitumor drug, bleomycin (BLM) is widely used in the treatment of a variety of cancers. In addition, nucleases play a crucial role in DNA replication, recombination and repair which are associated with cancer development. Thus, the development of BLM and nuclease detection methods is of great significance in cancer therapy and related biological mechanism research. Here, a WS₂ nanosheet-based turn-on fluorescent sensing platform for simple, fast and sensitive detection of BLM and nuclease was reported. WS₂ nanosheet exhibits different affinity toward ssDNA with different length and excellent fluorescence quenching ability. A fluorescein (FAM)-labeled long ssDNA could be adsorbed on the surface of WS₂ nanosheet and the fluorescence was therefore quenched. In the presence of BLM·Fe(II) or S1 nuclease (a ssDNA-specific nuclease which was used as a model enzyme), an irreversible scission of long ssDNA was underwent through the BLM-induced oxidation cleavage or S1 nuclease-induced enzymatic hydrolysis. Short FAM-linked oligonucleotide fragments which could not be adsorbed on the nanosheet surface were then produced, resulting in a weak fluorescence quenching after mixing WS₂ nanosheets. Thus, the fluorescence signal was restored. The proposed sensor displays a wide linear range and a high sensitivity with a detection limit of 0.3 nM for BLM and 0.01 U mL⁻¹ for S1 nuclease. It also exhibits a good performance in complex biological samples. This method not only provides a strategy for BLM or S1 nuclease assay but also offers a potential application in biomedical and clinical study.