Covalence reduction factors of four-coordinated pseudo-tetrahedral paramagnetic compounds inD 2d symmetry

Theoretical expressions for the covalence reduction factors of orbital angular momentum and spin-orbit coupling in pseudo-tetrahedral four-coordinated paramagnetic complexes withD _2d symmetry, denoted ask's andR's respectively, have been derived. p ]The mixing coefficients in the antibonding MO's for the CuCl ₄ ^2- ion in three complexes are estimated using suitable approximations. It is shown thatk's must be less thanR's in Tinkham's approximation. Certain misconceptions existing in the literature regarding the value of the integral 〈p _u |???u|s〉 have been clarified.     

二甲基铍中铍原子的共价

根据共价的新定义,以自然键轨道法研究了二甲基铍中铍原子的共价情况.结果表明,在二甲基铍的单体、二聚体和多聚体中,铍的共价分别为2、4和6.     

A novel photoelectrochemical immunosensor by integration of nanobody and TiO2 nanotubes for sensitive detection of serum cystatin C

Cystatin C (CysC) is a sensitive marker for the estimation of the glomerular filtration rate and the clinical diagnosis of different diseases. In this paper, CysC-specific nanobodies (Nbs) were isolated from a phage display nanobody library. A simple and sensitive photoelectrochemical immunosensor based on TiO₂ nanotube arrays (TNAs) was proposed for the sensitive detection of CysC. The TiO₂ nanotube arrays deposited by electrochemical anodization displayed a high and stable photocurrent response under irradiation. After coupling CysC-specific nanobody to TNA (Nb/TNA), the proposed immunosensor for CysC can be utilized for tracking the photocurrent change of Nb/TNA caused by immunoreactions between CysC and the immobilized CysC-specific Nb. This allowed for the determination of CysC with a calibration range from 0.72 pM to 7.19 nM. The variation of the photocurrent was in a linear relationship with the logarithm of the CysC concentration in the range of 0.72 pM–3.6 nM. The immunosensor had a correlation coefficient of 0.97 and a detection limit of 0.14 pM at a signal-to-noise ratio of 3. The proposed immunosensor showed satisfactory intra- and inter-assay accuracy, high selectivity and good stability. As a result, this proposed strategy would offer a novel and simple approach for the detection of immunoreactions, provide new insights in popularizing the diagnosis of CysC, and extend the application of TiO₂ nanotubes.     

二维材料“遇见”生物大分子:机遇与挑战

二维材料的超薄原子层结构使其具有独特的力学性能、导热导电性以及巨大的比表面积,在能源存储、催化、传感和生物医学等领域引起了国内外学者的广泛关注。将二维材料与具有生物活性的生物大分子相结合可以为开发具有优异电学、力学和生物学功能的特种功能材料提供新的方法和途径。近年来,科研工作者针对这一方向展开了广泛的研究,取得了一系列重要的成果,使二维材料与生物大分子的结合与应用成为了新的研究热点。本文综述了近年来二维材料和生物大分子之间的相互作用及应用的研究进展,重点介绍了二维材料与生物大分子在分子水平上的相互作用机理,还总结了基于二维材料与生物大分子之间的相互作用在工程、疾病治疗和抗菌中的应用,并对其未来的研究趋势提出了展望。     

铬的羰基络合物及其碳炔衍生物中铬原子的共价

用ＤＶ－Ｘα方法和自然轨道法研究了Ｃｒ（ＣＯ）_６和（ＣＯ）_４ＩＣｒＣＣＨ_３的电子结构和成键情况，并根据共价新定义讨论了其中铬原子的共价。结果表明：在（ＣＯ）_４ＩＣｒＣＣＨ_３中，Ｃｒ－Ｃ_（ｃａｒｂｙｎｅ）之间存在三重键，但其中只有σ键定域在Ｃｒ－Ｃ_（ｃａｒｂｙｎｅ）两原子之间，而两个π键已部分离域到各ＣＯ上；另外，中心铬原子上的价电子未能反馈到Ｃ_（ｃａｒｂｙｎｅ）上。两个因素同时作用，结果使Ｃ_（ｃａｒｂｙｎｅ）上的电荷密度较同一分子中的Ｃ_（ＣＯ）和Ｃ_（Ｍｅ）小．这一计算结果从理论上解释了该分子的~（１３）ＣＮＭＲ谱化学位移Ｃ_（ｃａｒｂｙｎｅ）大于Ｃ_（ＣＯ）和Ｃ_（Ｍｅ）的原因。由于在Ｃｒ（ＣＯ）_６和（ＣＯ）_４ＩＣｒＣＣＨ_３分子中铬原子均接受了１２个有效共享成键电子，根据共价新定义，铬原子共价均为１２。     

On the covalence in coinage-metal halides M3X3 (M = Cu,Ag and Au,X = F – I)

Systematic theoretical investigations have been performed to understand the periodicity, structures and interactions of the coinage-metal halide series, M₃X₃(M = Cu, Ag and Au, X = F – I) at MP2 theoretical level with extended basis sets. Mechanisms of M–X and M–M interactions were investigated by natural bond orbital analyses, natural resonance theory, electron localisation function, electron density deformation, atoms in molecules and visualised by reduced density gradient analyses. Periodic trends are found in the bond length, stability and covalent nature of the M–X and M–M interactions. As expected, increased covalence when halogens become heavier and Au–Au and Au–X interactions contain enhanced covalence in comparison with lighter congeners Cu₃X₃ and Ag₃X₃.     

炔烃桥和氢桥铍化合物中铍原子的共价

根据作者之一提出的共价的新定义，用DV－X_αSCC和自然健轨道法研究了[MeBe(C≡CMe)NMe_3]_2，[Be(C≡CR)_2]_n，[MeBeH·NMe_3]及(BeH_2)_n等化合物中铍原子的共价．结果表明，在这几种化合物中铍原子的共价都是6．     

Comparative analysis of crystal field effects and energy level scheme of six-fold coordinated Cr ion in the pyrochlores, Y2B2O7 (B=Ti, Sn)

The electronic energy levels of the six-fold coordinated Cr⁴⁺ ion in the pyrochlores Y₂B₂O₇ (B=Sn⁴⁺, Ti⁴⁺), have been computed using the exchange charge model of crystal field theory. The calculated Cr⁴⁺ energy levels and their trigonal splitting are in good agreement with experimental spectra. Calculations of the crystal field parameters show that the higher crystal field strength in Y₂Sn₂O₇ (in comparison with Y₂Ti₂O₇) arises from increased orbital overlap effects between the Cr⁴⁺ ion and the nearest oxygen ions, which are located at the 48f crystallographic position of the pyrochlore lattice. The increased overlap in Y₂Sn₂O₇ occurs despite the fact that the Cr⁴⁺-O^2- bond distance in Y₂Sn₂O₇ is longer than in Y₂Ti₂O₇. This is attributed to a lack of hybridization (covalent bonding) between the filled 2p orbital of oxygen ion occupying the 48f site of the pyrochlore lattice and the filled Sn⁴⁺ 4d¹⁰ orbital. As a result, a stronger crystal field is experienced by Cr⁴⁺ ions in Y₂Sn₂O₇, even if the Cr⁴⁺-O²⁻ distances are greater in this case, when compared to those in Y₂Ti₂O₇.