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1.
以结构化学指导新型金属 有机纳米器件的合理合成和物理性能研究,探索它们的自组装规律,共设计合成了 1 2个含N、S及COO- 基团的具有不同对称性和立体选择性的新颖大骨架多官能团柔性配体,以及由它们与金属离子自组装合成了 1 8个新型金属 有机纳米笼、纳米管和配位聚合物,开辟了一条合成金属 有机纳米器件的新途经。其中,一个具有Oh对称的金属纳米笼,笼内体积超过 1 0 0 0 A3,可以同时容纳多种离子和小分子,是目前已测定单晶结构的金属纳米笼中容量最大的一个。而用金属离子把纳米管串联成的金属 有机纳米管则是国际上首例报道的结构有序无机 有机纳米管阵列;并创新性的采用低温溶剂热法合成了一个新颖的具有半导体和顺磁性质的Ni 巯基嘧啶二维层状聚合物和两个二维折叠格子状化合物;另外,用巯基嘧啶作为难溶盐CuCN的溶解模板,得到了国际上首例六角形CuCN大环化合物和另外一个新颖的类石墨层状CuCN化合物. 过渡金属与多官能团配体通过配位键来驱动和引导自组装,形成具有均一尺寸和特定形状的金属 有机纳米器件,是当今化学与材料领域研究的前沿之一。而通过设计合成具有特定对称性和立体选择性的有机配体,并把它们与金属离子自组装形成具有纳米尺寸和特殊功能的纳米球和纳米管,更是在纳米科技、 相似文献
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Complexation of π-conjugated ligands by metal or semimetal ions leads to the enhancement of the planarity and rigidity of π-conjugated systems. Boron, especially, has played a central role in the design of luminescent main-group complexes. However, these complexes still suffer the disadvantage of aggregation-caused quenching as well as typical organic fluorophores. It has recently been reported that some types of boron complexes exhibit the aggregation-induced emission (AIE) property. Moreover, AIE behavior from complexes and organometallic compounds composed of the other group 13 elements, such as aluminum and gallium, has emerged in this decade. These observations greatly encourage us to develop advanced functional materials based on the group 13 elements. Indeed, recent research has demonstrated that these classes of materials are potentially versatile scaffolds for constructing chromic luminophores, efficiently emissive π-conjugated polymers and so on. This review mainly describes AIE-active group 13 complexes with four-coordinate structures and their application as photo-functional materials. Proposed mechanisms of the origins of AIE behavior are briefly discussed. 相似文献
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Qing-Fang Guan Zi-Meng Han Tong-Tong Luo Huai-Bin Yang Hai-Wei Liang Si-Ming Chen Guang-Sheng Wang Shu-Hong Yu 《国家科学评论(英文版)》2019,6(1):64
Although a variety of nanoparticles with better-than-bulk material performances can be synthesized, it remains a challenge to scale the extraordinary properties of individual nanoscale units to the macroscopic level for bulk nanostructured materials. Here, we report a general and scalable biosynthesis strategy that involves simultaneous growth of cellulose nanofibrils through microbial fermentation and co-deposition of various kinds of nanoscale building blocks (NBBs) through aerosol feeding on solid culture substrates. We employ this biosynthesis strategy to assemble a wide range of NBBs into cellulose nanofibril-based bulk nanocomposites. In particular, the biosynthesized carbon nanotubes/bacterial cellulose nanocomposites that consist of integrated 3D cellulose nanofibril networks simultaneously achieve an extremely high mechanical strength and electrical conductivity, and thus exhibit outstanding performance as high-strength lightweight electromagnetic interference shielding materials. The biosynthesis approach represents a general and efficient strategy for large-scale production of functional bulk nanocomposites with enhanced performances for practical applications. Industrial-scale production of these bulk nanocomposite materials for practical applications can be expected in the near future. 相似文献
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岩石脆性破裂时破裂发射的机理 总被引：1，自引：0，他引：1
本文运用量子化学中的CNDO方法(Complete Neglect of Differential Overlap——全略微分重叠)以单晶硅和地壳岩石的典型构造——硅氧四面体为研究对象对脆性破裂时破裂发射的机理提出了一种理论解释,认为是破裂前晶体受外力作用发生构型变化使得电子能量增加成为自由电子的结果。利用这一理论,地震发生前的电导率增加、电磁辐射和地震时的地光等现象都可以得到解释。 相似文献
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This paper reviews our work on the application of ultrafast pulsed laser micro∕nanoprocessing for the three-dimensional (3D) biomimetic modification of materials surfaces. It is shown that the artificial surfaces obtained by femtosecond-laser processing of Si in reactive gas atmosphere exhibit roughness at both micro- and nanoscales that mimics the hierarchical morphology of natural surfaces. Along with the spatial control of the topology, defining surface chemistry provides materials exhibiting notable wetting characteristics which are potentially useful for open microfluidic applications. Depending on the functional coating deposited on the laser patterned 3D structures, we can achieve artificial surfaces that are (a) of extremely low surface energy, thus water-repellent and self-cleaned, and (b) responsive, i.e., showing the ability to change their surface energy in response to different external stimuli such as light, electric field, and pH. Moreover, the behavior of different kinds of cells cultured on laser engineered substrates of various wettabilities was investigated. Experiments showed that it is possible to preferentially tune cell adhesion and growth through choosing proper combinations of surface topography and chemistry. It is concluded that the laser textured 3D micro∕nano-Si surfaces with controllability of roughness ratio and surface chemistry can advantageously serve as a novel means to elucidate the 3D cell-scaffold interactions for tissue engineering applications. 相似文献
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《Information processing & management》2023,60(4):103351
Existing 2D image-based 3D model retrieval (IBMR) methods usually use the pseudo labels as semantic guidance to reduce the domain-wise and class-wise feature distribution difference across annotated 2D images and unlabeled 3D models. However, they cannot entirely guarantee the quality of pseudo labels, which will decrease prediction discriminability and diversity to affect feature distribution alignment. Therefore, we propose a novel unsupervised self-training correction learning (USTCL) network for the IBMR task. Specifically, we first utilize a CNN to encode 2D images and 3D models (described as multi-view images). Then, we design a noise-corrected self-training learning module (NCST) to denoise pseudo labels in an adversarial manner to make the predicted categories more easily discriminated to improve prediction discriminability. Besides, we employ a target-guided pseudo label refining strategy (TPLR) to progressively refine generated pseudo labels to prevent minority categories from being pushed into majority categories, thereby enhancing prediction diversity. Comprehensive experiments on popular IBMR benchmarks validate the effectiveness and robustness of USTCL, e.g., it can achieve the average gains of 54.20%/22.30%, 62.17%/43.21%, 54.21%/31.18%, 63.48%/43.28%, 59.87%/44.49% in terms of NN, FT, ST, F-measure, DCG and the decrease of 29.50%/35.15% corresponding to ANMRR on MI3DOR (21,000 2D images and 7,690 3D models) and MI3DOR-2 (19,694 2D images and 3,982 3D models), respectively. 相似文献
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《国家科学评论(英文版)》2015,(2)
The expression of chirality in 2D molecular assemblies on solid surfaces has unique features compared to the analogous process in 1D and 3D supramolecular assemblies. Understanding the formation of chiral molecular assemblies on surfaces not only provides insight into the origin and transfer of chirality in many enantioselective processes, but also aids rational design and construction of chiral architectures and materials. his present contribution reviews recent studies on how chirality is induced and expressed on the surface at diferent levels, both from intrinsically chiral and achiral molecules. Furthermore, we discuss the regulation efect of some pivotal factors, for example, the chemical structure, the chiral auxiliary molecules,and the assembled environments, on the expression of chirality in molecular assembly. 相似文献
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Sheng-Nan Sun Ning Li Jiang Liu Wen-Xin Ji Long-Zhang Dong Yi-Rong Wang Ya-Qian Lan 《国家科学评论(英文版)》2021,8(3)
Identification of the real catalytic site in CO2 reduction reaction (CO2RR) is critical for the rational design of catalysts and the understanding of reactive mechanisms. In this study, the catalytic activity of pyridine-containing materials was for the first time structurally demonstrated in CO2RR by crystalline supramolecular coordination compounds model system. The system consists of three stable supramolecular coordination compounds (Ni-TPYP, Ni-TPYP-1 and Ni-TPP) with different numbers (4, 2 and 0) of active pyridine groups (i.e. uncoordinated pyridine nitrogen atoms). The electrocatalytic test results show that with the decrease of the number of active pyridine groups, the CO2RR performance is gradually reduced, mainly showing the reduction of highest FECO (99.8%, 83.7% and 25.6%, respectively). The crystallographic, experimental and theoretical evidences prove that the CO2RR activity is more likely derived from uncoordinated pyridine nitrogen than the electrocatalytic inert metal nickel in porphyrin center. This work serves as an important case study for the identification of electrocatalytic activity of pyridine-containing materials in CO2RR by simple supramolecular model system. 相似文献
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《Information processing & management》2022,59(2):102821
People often search for information in order to learn something new. In recent years, the “search-as-learning” movement has argued that search systems should be better designed to support learning. Current search systems (especially Web search engines) are largely designed and optimized to fulfill simple look-up tasks (e.g., navigational or fact-finding search tasks). However, they provide less support for searchers working on complex tasks that involve learning. Search-as-learning studies have investigated a wide range of research questions. For example, studies have aimed to better understand how characteristics of the individual searcher, the type of search task, and interactive features provided by the system can influence learning outcomes. Learning assessment is a key component in search-as-learning studies. Assessment materials are used to both gauge prior knowledge and measure learning during or after one or more search sessions. In this paper, we provide a systematic review of different types of assessments used in search-as-learning studies to date. The paper makes the following three contributions. First, we review different types of assessments used and discuss their potential benefits and drawbacks. Second, we review assessments used outside of search-as-learning, which may provide insights and opportunities for future research. Third, we provide recommendations for future research. Importantly, we argue that future studies should clearly define learning objectives and develop assessment materials that reliably capture the intended type of learning. For example, assessment materials should test a participant’s ability to engage with specific cognitive processes, which may range from simple (e.g., memorization) to more complex (e.g., critical and creative thinking). Additionally, we argue that future studies should consider two dimensions that are understudied in search-as-learning: long-term retention (i.e., being able to use what was learned in the long term) and transfer of learning (i.e., being able to use what was learned in a novel context). 相似文献
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Supramolecular chemistry provides a means to integrate multi-type molecules leading to a dynamic organization. The study of functional nanoscale drug-delivery systems based on supramolecular interactions is a recent trend. Much work has focused on the design of supramolecular building blocks and the engineering of supramolecular integration, with the goal of optimized delivery behavior and enhanced therapeutic effect. This review introduces recent advances in supramolecular designs of nanoscale drug delivery. Supramolecular affinity can act as a main driving force either in the self-assembly of carriers or in the loading of drugs. It is also possible to employ strong recognitions to achieve self-delivery of drugs. Due to dynamic controllable drug-release properties, the supramolecular nanoscale drug-delivery system provides a promising platform for precision medicine. 相似文献
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The supramolecular chemistry of nanoclusters is a flourishing area of nano-research; however, the controllable assembly of cluster nano-building blocks in different arrays remains challenging. In this work, we report the hierarchical structural complexity of atomically precise nanoclusters in micrometric linear chains (1D array), grid networks (2D array) and superstructures (3D array). In the crystal lattice, the Ag29(SSR)12(PPh3)4 nanoclusters can be viewed as unassembled cluster dots (Ag29–0D). In the presence of Cs+ cations, the Ag29(SSR)12 nano-building blocks are selectively assembled into distinct arrays with different oxygen-carrying solvent molecules―Cs@Ag29(SSR)12(DMF)x as 1D linear chains (Ag29–1D), Cs@Ag29(SSR)12(NMP)x as 2D grid networks (Ag29–2D), and Cs@Ag29(SSR)12(TMS)x as 3D superstructures (Ag29–3D). Such self-assemblies of these Ag29(SSR)12 units have not only been observed in their crystalline state, but also in their amorphous state. Due to the diverse surface structures and crystalline packing modes, these Ag29-based assemblies manifest distinguishable optical absorptions and emissions in both solutions and crystallized films. Furthermore, the surface areas of the nanocluster crystals are evaluated, the maximum value of which occurs when the cluster nano-building blocks are assembled into 2D arrays (i.e. Ag29–2D). Overall, this work presents an exciting example of the hierarchical assembly of atomically precise nanoclusters by simply controlling the adsorbed molecules on the cluster surface. 相似文献
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能源消费量大、能源效率低以及环境问题突出已经成为中国发展面临的严峻挑战。由于工业部门能源消耗占中国能源消耗总量的70%左右,因此,本文基于工业36个子行业2006-2012年的数据,采用结合自然处置性和管理处置性概念的DEA模型将固定资产、能源消费及劳动力作为自然处置性下的投入,研发（R&D）投资额作为管理处置性下的投入,评价各子行业能源和环境综合效率以及R&D投资对各子行业减少非期望产出的有效性,最后,采用Truncated回归模型分析中国工业能源和环境综合效率的影响因素。研究结果表明：除烟草制品业等4个行业外,其余32个行业的综合效率均有改善空间,煤炭开采和洗选业、化学原料和化学制品制造业以及非金属矿物制品业等的综合效率值均在0.800以下,其中非金属矿物制品业效率值最低仅为0.472;2012年,研发投资对煤炭开采和洗选业等16个行业减少非期望产出是有效的;能源结构、技术创新和市场竞争对综合效率具有显著影响,其中煤炭在能耗中占比的提高对综合效率有抑制作用,而研发投资比例的提高对其则有促进作用。 相似文献
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In this paper, we study the algebraic connectivity of directed complex networks with scale-free property. Algebraic connectivity of a directed graph is the eigenvalue of its Laplacian matrix whose real part is the second smallest. This is known as an important measure for the diffusion speed of many diffusion processes over networks (e.g. consensus, information spreading, epidemics). We propose an algorithm, extending that of Barabasi and Albert, to generate directed scale-free networks, and show by simulations the relations between algebraic connectivity and network size, exponents of in/out-degree distributions, and minimum in/out degrees. The results are moreover compared to directed small-world networks, and demonstrated on a specific diffusion process, reaching consensus. 相似文献
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Shanshan Liu Ke Yang Wenqing Liu Enze Zhang Zihan Li Xiaoqian Zhang Zhiming Liao Wen Zhang Jiabao Sun Yunkun Yang Han Gao Ce Huang Linfeng Ai Ping Kwan Johnny Wong Andrew Thye Shen Wee Alpha T N&#x;Diaye Simon A Morton Xufeng Kou Jin Zou Yongbing Xu Hua Wu Faxian Xiu 《国家科学评论(英文版)》2020,7(4):745
Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC 2D FM Fe3GeTe2 (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that TC of 4-layer Fe3GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, TC can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices. 相似文献
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This paper examines the relationship between a firm's strategic framework and business environment and the probability of becoming the target of “copying”, differentiated into (i) unauthorized reproduction of its technological product elements or insignia, and (ii) patent and trademark infringement. Based on bivariate and multivariate analyses of survey data, we show patterns of the links between being (legally or illegally) imitated and IP protection (e.g., defensive publishing), general strategy (e.g., selling products abroad or off-shoring R&D activities) and organizational factors (e.g., firm size). Management implications for successful strategies against the different types of being copied are derived. 相似文献
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Tunable luminescent materials are becoming more and more important owing to their broad application potential in various fields. Here we construct a pillar[5]arene-based hybrid material with stimuli-responsive luminescent properties and ion-sensing abilities from a pyridine-modified conjugated pillar[5]arene and a planar chromophore oligo(phenylenevinylene) upon coordination of Cd (II) metal cores. This new material not only shows an optimized luminescence due to the minimized π–π stacking and efficient charge transfer properties benefitting from the existence of pillar[5]arene rings, but also exhibits tunable multicolor emission induced by different external stimuli including solvent, ions and acid, indicating great application potential as a fluorescent sensory material, especially for Fe3+. With this pillar[5]arene-based dual-ligand hybrid material, valid optimization and regulation on the fluorescence of the original chromophore have been achieved, which demonstrates a plausible strategy for the design of tunable solid-state luminescent materials and also a prototypical model for the effective regulation of fluorescent properties of planar π systems using synthetic macrocycle-based building blocks. 相似文献
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Tremendous efforts have been dedicated to developing high-performance energy storage devices based on the micro- or nano-manipulation of novel carbon electrodes, as certain nanocarbons are perceived to have advantages such as high specific surface areas, superior electric conductivities, excellent mechanical properties and so on. In typical electrochemical electrodes, ions are intercalated/deintercalated into/from the bulk (for batteries) or adsorbed/desorbed on/from the surface (for electrochemical capacitors). Fast ionic transport, significantly determined by ionic channels in active electrodes or supporting materials, is a prerequisite for the efficient energy storage with carbons. In this report, we summarize recent design strategies for ionic channels in novel carbons and give comments on the promising features based on those carbons towards tailorable ionic channels. 相似文献
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分子折叠体是一类由非共价键稳定的、采用有序构象的寡聚物或聚合物. 我们设计并合成了三类非天然的折叠体，包括：1）由疏溶剂作用驱动的并入萘环板块的寡聚乙二醇折叠体，2）由分子内氢键驱动的寡聚酰肼折叠体，3）由分子内氢键驱动的并入锌卟啉板块的寡聚苯酰胺折叠体. 定性和定量的研究揭示，在有机溶剂中这些折叠体可以作为非天然受体分子高效络合或识别结构匹配的有机分子和离子，并且氢键驱动的折叠体可以通过络合作用实现超分子体系的手性诱导或手性放大. 相似文献