用金纳米粒子修饰硅纳米线及复合结构的光谱性质研究

在溶液中以正己硫醇作稳定剂, 利用HAuCl4与HF处理后的硅纳米线(SiNWs)的氧化还原反应, 在SiNWs表面负载金纳米粒子(AuNPs). 通过调整HAuCl4的浓度, 得到了AuNPs粒径从3.2到7.0 nm的AuNPs/SiNWs复合结构, 并对这种复合结构进行了紫外-可见吸收光谱和荧光光谱研究. 紫外-可见吸收光谱研究表明, 负载不同粒径的AuNPs的SiNWs在530～580 nm间有明显的由AuNPs表面等离子体共振引起的吸收, 且随着AuNPs粒径的增加, 该吸收峰发生红移. 负载前后的荧光光谱表明, 在红光和绿光区负载AuNPs的SiNWs的荧光峰与HF处理后SiNWs的荧光峰峰形相当, 峰位变化不大; 但在蓝光区, 不同于HF处理前后SiNWs的发射峰(464 nm左右), 负载了AuNPs的SiNWs在423 nm的位置处出现了强荧光峰, 这个峰是AuNPs费米能级的电子与sp或d带的空穴辐射复合产生的.     

The Inhibition Effect of Graphene Oxide Nanosheets on the Development of Streptococcus mutans Biofilms

Bacterial biofilms play a critical role in dental pathogenic mechanisms due to their ability to tolerate many traditional antibacterial agents. Thus, it is crucial to find effective methods to inhibit the occurrence and development of biofilms. Recently, graphene oxide (GO) nanosheets have become a promising antibacterial nanomaterial for use in various applications. This study focuses on the effect of GO nanosheets on the development of Streptococcus mutans biofilms. It is found that GO nanosheets are highly effective at inhibiting the formation of bacterial biofilms at concentrations ranging from low to high in early development stages. After GO treatment, the ratio of living cells in the biofilm decreases significantly, and the biofilm structure is destroyed. In contrast, GO has a minimal effect on mature biofilms.     

直流等离子体离子化检测器的研究：管道煤气中可燃气体的测定

本文提出一种改进的直流等离子体离子化检测器（ＤＣＰＩＤ），用于管道煤气中可燃气体Ｈ２、ＣＨ４和ＣＯ的测定。采用氢气作工作气体，对该检测器的工作参数和响应特性进行了优化。本法结果与微波诱导等离子体离子化检测器（ＭＩＰＩＤ）的结果作了比较，结果满意。     

Synthesis and characterization of ordered hexagonal and cubic mesoporous tin oxides via mixed-surfactant templates route

Ordered hexagonal and cubic mesoporous tin oxides were synthesized for the first time in the presence of mixed cationic and neutral surfactants (a mixture of cetyltrimethylammonium bromide cationic surfactant and dodecylamine neutral surfactant) with different alkali and simple inorganic precursors at room temperature. In the synthesis systems, the dodecylamine neutral surfactant may function as a polar organic cosolvent and cosurfactant. The formation of the tin oxide mesostructured material was proposed to be due to the presence of hydrogen-bonding interactions between the supramolecular template and inorganic precursors Sn4+ and OH-, which were assumed to self-assemble around the cationic surfactant molecules. The materials are characterized by X-ray powder diffraction, transmission electron microscopy, thermogravimetric analysis, and N2 adsorption/desorption isotherm. The surface areas of materials evaluated from the N2 sorption isotherms are about 248 m(2)/g for hexagonal mesoporous tin oxide (SnH) and 281 m(2)/g for cubic mesoporous tin oxide (Sn-C) for calcination at 350 degrees C.     

Effects of gamma-irradiation and air annealing on Yb-doped Y3Al5O12 single crystal

The effects of gamma-irradiation on the air-annealed 10at.% Yb:Y(3)Al(5)O(12) (YAG) and air annealing on the gamma-irradiated 10at.% Yb:YAG have been studied by the difference absorption spectra before and after treatment. The gamma-irradiation and air annealing led to opposite changes of the absorption properties of the Yb:YAG crystal. After air annealing, the gamma-irradiation induced centers were totally removed and the concentration of Fe(3+) and Yb(3+) were lightly increased. For the first time, the gamma-irradiation induced valence changes between Yb(3+) and Yb(2+) ions in Yb:YAG crystals have been observed.     

混凝土黏塑性动力损伤本构关系

从静力弹塑性损伤本构关系的基本框架出发, 综合考虑塑性应变与损伤 演化的率敏感性, 建立了能够较为全面地描述混凝土在动力加载条件下非线性性能的混凝土 黏塑性动力损伤本构模型. 为了考虑塑性应变的率敏感性, 基于Perzyna理论推导了有效应 力空间黏塑性力学基本公式, 采用改进的Perzyna型动力演化方程, 将损伤静力演化方程推 广到动力加载情形. 基于并联弹簧模型, 从概率论的角度推导给出了一维损伤静力演化方程, 并基于能量等效应变的基本概念将其推广到多维损伤演化. 利用数值模拟, 计算得到了 混凝土在不同应变率下的应力应变全曲线, 同时得到了一维动力提高因子和二维动力强度包 络图, 数值结果与试验结果的对比表明了该模型的有效性.     

Oxidative Dissolution of Resoles: A Versatile Approach to Intricate Nanostructures

Resoles are resins obtained by base‐catalyzed phenol–formaldehyde condensation with a three‐dimensional cross‐linked framework. They are considered as highly chemical‐resistant, and calcination is thus generally used in the treatment of resole‐type resins, which significantly limits the diversity of nanostructured materials that can be derived from resole‐type resins. Herein, we report that selected metal nitrate solutions can be used to dissolve various types of nanostructured resoles through an oxidative dissolution process. This strategy not only enables the controlled dissolution of resoles, but more importantly provides a new approach to selectively etch resole‐based nanocomposites to give rise to a variety of nanostructured materials with unprecedented architectures and great potential in bioapplications.     

How rigid are conjugated non-ladder and ladder polymers?

Persistence length is commonly used to quantitatively describe the chain rigidity of macromolecules, which represents an important structural parameter governing many physical properties of polymers. Although the mathematical models and experimental measurements on the chain rigidity of conventional single stranded polymers have been well explored and documented, those of the more rigid yet highly intriguing multiple stranded polymers, especially conjugated ladder polymers, are yet not well established. This article introduces the fundamental concepts on macromolecular chain rigidity, as well as the corresponding experimental methods, models, and simulations. Subsequently, representative examples of works done on the chain rigidity of nonladder conjugated polymers and conjugated ladder polymers are reviewed. Last but not least, it provides outlooks on the challenges with respect to the less-investigated chain rigidity of conjugated ladder polymers, including new models to describe and predict chain conformation, synthetic control on structural defects, and insights into the correlation of rigidity and applications.     

Influence of embedded boron nitride nanosheets on Fe3+ diffusion in Fricke gel dosimeter and its response to γ rays

Journal of Radioanalytical and Nuclear Chemistry - The Fe3+ diffusion in Fricke gel dosimeter, widely used for the measurement of accurate dose distributions in radiotherapy, results in a gradual...     

N-Heterocyclic Carbene Stabilized Dicarbondiphosphides: Strong Neutral Four-Membered Heterocyclic 6π-Electron Donors

In contrast to cyclic π-conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N-heterocyclic carbenes (NHCs) NHC→C₂P₂←NHC ( 1 a , b ) (NHC=IPr or SIPr) contain a four-membered C₂P₂ ring with an aromatic 6π-electron configuration. These heterocycles coordinate to a variety of complex fragments with metals from groups 6, 9, and 10, namely [M⁰(CO)₃] (M=Cr, Mo), [Co^I(CO)₂]⁺, or [Ni^IIBr₂], through an η⁴-coordination mode, leading to complexes 2 a , b , 3 a , b , 5 a , b , and 6 a , b , respectively. These complexes were characterized by X-ray diffraction methods using single crystals, IR spectroscopy, and DFT calculations. In combination these methods indicate that 1 a , b behave as exceptionally strong 6π-electron donors.