Loading of Exponentially Grown LBL Films with Silver Nanoparticles and Their Application to Generalized SERS Detection

Feature film : Thin films made by exponential layer‐by‐layer growth display high diffusivity and can be readily infiltrated with inorganic nanoparticles. They can sequestrate molecular systems from solution as a function of the composition of their layers, while providing intense surface‐enhanced Raman scattering (SERS) signals (see picture).

     

一类求解抛物型方程侧边值问题的最优滤波方法

该文考虑一类特殊的抛物型方程侧边值问题,即一类含有对流项的非标准逆热传导问题. 给定在x=1处的温度测量值来确定区间(0,1)上的未知解u(x, t). 这是一类不适定问题,即问题的解(如果解存在)不连续依赖于数据.为了求解这一问题, 必须采用某些正则化技巧. 该文给出了一种最优滤波方法, 使得问题的真实解和近似解之间的误差估计达到了Hölder型最优. 同时还证明了问题的解在x=0处的收敛性.     

Spontaneous CdTe --> alloy --> CdS transition of stabilizer-depleted CdTe nanoparticles induced by EDTA

CdTe nanoparticles stabilized by l-cysteine are chemically transformed into CdS nanoparticles of the same diameter via an intermediate CdTeS alloy without any auxiliary source of sulfur. The reaction is induced by ethylenediaminetetraacetic acid dipotassium salt dehydrate (EDTA), which was demonstrated experimentally to act as a catalyst by partially removing thiol stabilizers from the nanoparticle surface. It is hypothesized that addition of EDTA facilitates Te(2-) release, and oxidation of Te(2-) drives the nanoparticle transition process. Unlike many reports on reactions catalyzed by nanocolloids, this is likely to be the first observation of a catalytic reaction in which nanoparticles function as a substrate rather than a catalyst. It opens new pathways for the synthesis of novel nanoscale II-VI and other semiconductors and represents an interesting case of chemical processes in nanocolloids with reactivity increased by depletion of the surface layer of thiol stabilizers. This includes but is not limited to accurate control over the particle composition and crystallization rate. The slow rate of the CdTe --> alloy --> CdS transition is important for minimizing defects in the crystal lattice and results in a substantial increase of the quantum yield of photoluminescence over the course of the transition.     

The radical-cation salt (DOEO)4[HgBr4] · TCE: Synthesis, structure and conductivity

Crystals of a new radical-cation salt (DOEO)₄[HgBr₄] · TCE (I) (DOEO = (1,4-dioxanediyl-2,3-dithio)ethylenedioxotetrathiafulvalene, TCE = 1,1,2-trichloroethane) were synthesized by electrocrystallization method at constant current (i=5×10^?6 A/cm²). Crystal structure was studied at room (293 K) and low (30 K) temperatures and was found to consist of the radical-cation layers alternating along the z-axis with tetrahedral HgBr ₄ ^2? anions and TCE molecules. The anion is disordered over three positions at room and over two positions at low temperatures with occupancy factors 87, 11, 2 and 98, 2%, respectively. The poorly occupied positions of the anion are overlapped with positions of the TCE molecule disordered over two equally occupied positions. The DOEO ethylene groups disordered at 293 K were found ordered at 30 K. The conductivity of I exhibits the following peculiarity: in a temperature interval of 120–140 K, the temperature dependence of resistivity has a pronounced maximum.     

Sphaleron Transition Rate in Lattice Gluodynamics

The sphaleron transition rate in gluodynamics at the temperature T /T_c = 1.24 has been calculated by lattice simulation. The calculations involve the Kubo formula, which relates the sphaleron transition rate to the correlation function of the topological charge density. The gradient flow method has been used to calculate the correlation function of the topological charge density. The Kubo formula has been inverted by the Backus–Gilbert method. The results have been compared to those obtained by other methods.     

Anomalously strong relaxation of the polarization of muons in the magnetically ordered and paramagnetic states of the TbMnO<Subscript>3</Subscript> multiferroic

An anomalously strong relaxation of the muon polarization in a magnetically ordered state in the TbMnO₃ multiferroic has been revealed by the method below the μSR Néel temperature (42 K). Such a relaxation is due to the muon channel of relaxation of the polarization and the interaction of the magnetic moment of the muon with inhomogeneities of the internal magnetic field of an ordered state in the form of a cycloid. Above the Néel temperature, beginning with temperatures depending on the applied magnetic field, a two-phase state has been revealed where one phase has an anomalously strong relaxation of the muon polarization for a paramagnetic state. These features of the paramagnetic state are due to short-range magnetic order domains that appear in strongly frustrated TbMnO₃. A true paramagnetic state has been observed only at T ≥ 150 K.     

氩氧流量比对CeOx-SnOx膜微观结构及光学性能的影响

采用磁控反应共溅射的方法,以金属Ce和Sn为金属源,成功地制备出CeOx-SnOx薄膜.利用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等测试手段对薄膜的结构、表面形貌及成分进行了分析和表征.结果表明薄膜以岛状模式生长,随氩氧比降低,结晶性增强,出现CeO2和SnO相.此外,利用紫外-可见分光光度计对薄膜的光学性能进行了研究,测试结果表明薄膜对紫外光有极强的吸收作用.当氩氧流量比为3∶1时,紫外光平均透过率仅为5.80;,而可见光平均透过率为81.48;.     

Gallium vacancy ordering in Ga<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin layers on Si(100), Si(111), and Si(123) substrates

Thin Ga₂Se₃ layers deposited on silicon substrates with the (100), (111), and (123) orientations are studied by transmission electron microscopy and X-ray microanalysis. Some features and regularities of the stoichiometric gallium vacancy ordering at different substrate orientations are discussed. The Ga₃Se₄(100)с(2 × 2) and Ga₂Se₃(111)(√3 × √3)-R30° ordered structures are formed on the Si(100) and Si(111) surfaces, respectively.     

Effect of Sulfonation Degree on Performance of Proton Exchange Membranes for Direct Methanol Fuel Cells

A series of proton exchange membranes based on sulfonated polyarylene ether ketones(SPAEKs) was used to study the effect of sulfonation degree on proton conductivity, methanol permeation and performance of direct methanol fuel cells(DMFCs). Dependences of physical characteristics of the membranes, i. e., proton conductivity, water uptake, swelling ratio, methanol permeability and ion exchange capacity(IEC) were systematically studied. Both methanol permeability and proton conductivity of the SPAEK membrane grow rapidly as the increase in sulfonation degree since methanol molecules and protons share the same transfer channel. However,the methanol permeability plays more important role comparing to proton conductivity. As a result, the SPAEK membrane with a medium sulfonation degree(60%) was found to yield the best performance in a DMFC due to the acquirement of balanced conductivity and methanol permeability.     

The Modern Problems of Ultrafast Magnetoacoustics (Review)

Acoustical Physics - A review of modern lines of research in the field of ultrafast magnetoacoustics is presented. Effects of interaction of ultrashort (picosecond) acoustic pulses with a magnetic...