二维材料的一维纳米带

自石墨烯被发现以来,二维材料研究成为一个新的研究热点。当二维材料制备成一维纳米带结构后,由于宽度方向上的限域效应和边缘结构的差异,导致其具有区别于二维材料的独特的电学、光学和磁学性质,因此逐步成为科学家关注的焦点。本文主要介绍了石墨烯、石墨炔、联苯烯、氮化硼、黑磷、过渡金属二硫族化合物等二维材料的一维纳米带的结构、制备方法和性能研究。首先讨论了二维材料制备成一维纳米带后的结构与性能的改变;其次,着重阐述了典型的纳米带制备方法,包括“自上而下”和“自下而上”两种策略,如二维片层刻蚀、打开纳米管、化学合成、化学气相沉积、外延生长及碳纳米管限域生长等方法,实现可控制备指定纳米宽度与具有特定边缘结构的纳米带,最终获得不同于其二维材料本体的特殊性能。最后,总结了不同方法制备纳米带的优缺点,提出了需要克服的困难和挑战,并展望了未来的研究方向,希望能引起国内外同行的广泛关注。     

Exploring Group 14 Structures: 1D to 2D to 3D

Various one‐, two‐ and three‐dimensional Group 14 (C, Si, Ge, Sn, and Pb) element structures at P=1 atm are studied in this work. As expected, coordination number (CN)—not an unambiguous concept for extended structures—plays an important part in the stability of structures. Carbon not only favors four‐coordination, but also is quite happy with π‐bonding, allowing three‐ and even two‐coordination to compete. Highly coordinated (CN>4) discrete carbon molecules are rare; that “saturation of valence” is reflected in the instability of C extended structures with CN>4. Si and Ge are quite similar to each other in their preferences. They are less biased in their coordination than C, allowing (as their molecular structures do) CN=5 and 6, but tending towards four‐coordination. Sn and Pb 3D structures are very flexible in their bonding, so that in these elements four‐ to twelve‐coordinate structures are close in energy. This lack of discrimination among ordered structures also points to an approach to the liquid state, consistent with the low melting point of Sn and Pb. The Group 14 liquid structures we simulate in molecular dynamics calculations show the expected, effective, first coordination number increase from 5.1 for Si to 10.4 for Pb. A special point of interest emerging from our study is the instability of potential multilayer graphene structures down Group 14. Only for C will these be stable; for all the other Group 14 elements pristine, unprotected, bi‐ and multilayer graphenes should collapse, forming “vertical” bonds as short as the in‐plane ones.     

Rigid optically-active D2 and D3 macrocycles

The synthesis and characterization of novel optically-active macrocycles, obtained by esterification reaction from a binaphthyl-containing diol and phthalic or terephthalic acids, and possessing overall D2 or D3 symmetry, is described.     

Solvent-controlled structural variation from 1D+2D→3D network with coexistence of polycatenation and polythreading to the 2D→3D polythreaded array

This article represents two types of entanglements, [Co₂(bibp)(BTB)₂][Co(bibp)₂(H₂O)₂] (1) and [Co₃(bibp)₂(H₂O)₂(BTB)₂]·2H₂O·2DMF (2) (bibp = 4,4′-bis(1-imidazolyl)biphenyl and H₃BTB = 1,3,5-tris(4-carboxyphenyl)benzene), which are 2-D→3-D polycatenated frameworks formed by parallel catenation of 1-D+2-D→2-D polythreaded motifs based on the double-layered sheet penetrated by ribbons of rings (1) and a 2-D→3-D mutual polythreading of three double-layered sheets with dangling arms (2), which is assembled by the same initial materials by simply changing the volume ratio of water/DMF medium.     

Vitamin D

Ohne Zusammenfassung     

Total synthesis of cryptomoscatones D1 and D2: stereochemical assignment of cryptomoscatone D1

The first total synthesis and structural elucidation of cryptomoscatone D1, and a novel synthetic approach for cryptomoscatone D2 were achieved in 30% and 29% overall yield, respectively. The synthesis relied on the use of a key Mukaiyama aldol reaction followed by a diastereoselective carbonyl reduction that allowed the preparation of four cryptomoscatone isomers in a stereochemically divergent manner. Comparison of NMR data and CD curves of the synthetic stereoisomers and natural products confirmed the stereochemical nature of cryptomoscatone D2, and led to establishing the absolute configuration of cryptomoscatone D1.     

光调控一维/二维纳米组装体的可逆转换

正控制生物分子组装成具有特定形貌和功能的纳米组装体是当今材料化学和超分子化学的研究热点~1。目前,科学家通过分子自组装构筑了大量形貌各异的超分子组装体,并对其性能进行了探究;其研究重点主要集中在控制组装体的组装和解组装。如何有效的控制分子组装成特定的组装体面临着重大挑战,但对拓宽超分子材料的应用具有重要的促进意义~2。最近,南开大学元素有机国家重点实验室刘育教授课题组构筑了能够可逆转换的一维纳米管     

Dimension Engineering of Stimuli-Responsive 1D Molecular Crystals into Unusual 2D and 3D Zigzag Waveguides

We demonstrate an innovative technique to achieve organic 2D and 3D waveguides with peculiar shapes from an acicular, stimuli-responsive molecular crystal, (2Z,2′Z)-3,3′-(anthracene-9,10-diyl)bis(2-(3,5-bis(trifluoromethyl)phenylacrylonitrile), Ant-CF₃. The greenish-yellow fluorescent (FL) Ant-CF₃ molecular crystals exhibit laser power-dependent permanent mechanical bending in 2D and 3D. Investigation of a single-crystal using spatially-resolved Raman/FL/electron microscopy, and theoretical calculations revealed photothermal (Z,E)/(E,E) isomerization-assisted transition from crystalline to amorphous phase at the laser-exposed regions. This phenomenon facilitates the dimension engineering of a 1D crystal waveguide into 2D waveguide on a substrate or a 3D waveguide in free space. The bends can be used as interconnection points to couple different optical elements. The presented technique has broader implications in organic photonics and other crystal-related photonic technologies.     

基于一维和二维纳米材料的神经界面构筑

Neural interfaces have contributed significantly to our understanding of brain functions as well as the development of neural prosthetics. An ideal neural interface should create a seamless and reliable link between the nervous system and external electronics for long periods of time. Implantable electronics that are capable of recording and stimulating neuronal activities have been widely applied for the study of neural circuits or the treatment of neurodegenerative diseases. However, the relatively large cross-sectional footprints of conventional electronics can cause acute tissue damage during implantation. In addition, the mechanical mismatch between conventional rigid electronics and soft brain tissue has been shown to induce chronic tissue inflammatory responses, leading to signal degradation during long-term studies. Thus, it is essential to develop new strategies to overcome these existing challenges and construct more stable neural interfaces. Owing to their unique physical and chemical properties, one-dimensional (1D) and two-dimensional (2D) nanomaterials constitute promising candidates for next-generation neural interfaces. In particular, novel electronics based on 1D and 2D nanomaterials, including carbon nanotubes (CNTs), silicon nanowires (SiNWs), and graphene (GR), have been demonstrated for neural interfaces with improved performance. This review discusses recent developments in neural interfaces enabled by 1D and 2D nanomaterials and their electronics. The ability of CNTs to promote neuronal growth and electrical activity has been proven, demonstrating the feasibility of using CNTs as conducting layers or as modifying layers for electronics. Owing to their good mechanical, electrical and biological properties, CNTs-based electronics have been demonstrated for neural recording and stimulation, neurotransmitter detection, and controlled drug release. Different from CNTs-based electronics, SiNWs-based field effect transistors (FETs) and microelectrode arrays have been successfully demonstrated for intracellular recording of action potentials through penetration into neural cells. Significantly, SiNWs FETs can detect neural activity at the level of individual axons and dendrites with a high signal-to-noise ratio. Their ability to record multiplexed intracellular signals renders SiNWs-based electronics superior to traditional intracellular recording techniques such as patch-clamp recording. Besides, SiNWs have been explored for optically controlled nongenetic neuromodulation due to their tunable electrical and optical properties. As the star of the 2D nanomaterials family, GR has been applied as biomimetic substrates for neural regeneration. Transparent GR-based electronics combining electrophysiological measurements, optogenetics, two-photon microscopy with multicellular calcium imaging have been applied for the construction of multimodal neural interfaces. Finally, we provide an overview of the challenges and future perspectives of nanomaterial-based neural interfaces.     

Analysis of five rare alleles at the STR loci D1S1656, D12S391, D13S317, Penta D,and D2S441

Short tandem repeat (STR) automatic typing technology is extensively used in forensic laboratories with commercial kits, in rare cases genotyping misinterpretations or mislabeling may occur due to unexpected rare alleles. This study refers to the investigation of several rare alleles observed from routine cases. Besides cross-kit verification with Goldeneye 25A (Beijing PeopleSpot Inc, China) and Huaxia platinum (Thermo Fisher Scientific, USA) kits, the next-generation sequencing technology by MiSeq FGx System (Illumina, USA) was applied to further validation. To solve the inconsistent outcomes reached by the above mentioned approaches at D2S441 locus, single gene amplification, gene cloning, and genetic sequencing was also performed. As a result, five rare alleles were detected. Two novel alleles of allele 3 at the D13S317 locus and allele 5 at the D2S441 locus were found; three previously reported alleles of allele 9 at D1S1656 locus, allele 19 at Penta D locus, and allele 28 at D12S391 locus in STRBase were initially supplemented with sequence information. We, therefore, propose that such uncommon observations with rare events should be carefully investigated and interpreted.     

Ensuring homology between 2D and 3D molecular crystals

Integrated studies using scanning tunneling microscopy and X-ray crystallography have established that 4,5,9,10-tetrahydropyrene-2,7-dicarboxylic acid and pyrene-2,7-dicarboxylic acid crystallize in 2D and 3D with striking homology. Different behavior is shown by related biphenyls that lack the planarizing conformational constraints of the pyrenyl core and the directing effects of intermolecular hydrogen bonding. The results of these studies show that molecules specifically designed to engage in multiple strong directional interadsorbate interactions are promising tools for imposing particular nanopatterns on surfaces and for revealing subtle aspects of crystallization.