An integrated computational tool for the study of the optical properties of nanoscale devices: application to solar cells and molecular wires

We present a combined computational strategy for the study of the optical properties of nanoscale systems, using a combination of codes and techniques based on Density Functional Theory (DFT) and its Time Dependent extension (TDDFT). In particular, we describe the use of Car–Parrinello molecular dynamics simulations for the study of nanoscale devices and show the integration of the obtained results with available quantum chemistry codes for the calculation of TDDFT excitation energies, including solvation effects by continuum solvation models. We review some prototypical applications of this integrated computational strategy, ranging from the interaction of dye sensitizers with TiO₂ nanoparticles, of interest in the field of dye-sensitized solar cells, to transition metal molecular wires exceeding 3 nm length.     

熔点标准物质的定值

介绍凝固点下降薄层比较法测量熔点标准物质熔点的测量装置的构成与工作原理。用该装置对5种标准物质的凝固点或熔点进行了测量，给出了定值结果和不确定度。     

铁合金厂回收的硅微粉在不同温度下晶相结构的研究

铁合金厂冶炼过程产生的大量硅微粉烟尘, 可以作为耐火材料和窑具材料的结合剂, 活性剂和矿化剂, 可促进耐火材料固相反应和烧结, 有利于晶型的转变, 提高耐火材料的高温性能。硅微粉在高于或等于1100 ℃不析晶。1200和1300 ℃析晶规律是:首先α-石英转变为α-方石英, 然后转变为α-鳞石英。在1400～1450 ℃首先析出卡片号为290085的石英变体, 然后转变为α-方石英。 而常规转化过程是α-方石英很难形成α-鳞石英, 而且不形成290085的变体, 因此其转化规律与常规不同。在液相存在情况下, 少量α-方石英转变为α-鳞石英, 不同温度下析晶结构探讨为实际生产提供适宜的升温曲线。     

Self-Organization and Dynamics of Nanoparticles in Chemically Active Plasmas for Low-Temperature Deposition of Silicon and Carbon-Based Nanostructured Films

Self-organization and dynamic processes of nano/micron-sized solid particles grown in low-temperature chemically active plasmas as well as the associated physico-chemical processes are reviewed. Three specific reactive plasma chemistries, namely, of silane (SiH₄), acetylene (C₂H₂), and octafluorocyclobutane (c—C₄F₈) RF plasma discharges for plasma enhanced chemical vapor deposition of amorphous hydrogenated silicon, hydrogenated and fluorinated carbon films, are considered. It is shown that the particle growth mechanisms and specific self-organization processes in the complex reactive plasma systems are related to the chemical organization and size of the nanoparticles. Correlation between the nanoparticle origin and self-organization in the ionized gas phase and improved thin film properties is reported. Self-organization and dynamic phenomena in relevant reactive plasma environments are studied for equivalent model systems comprising inert buffer gas and mono-dispersed organic particulate powders. Growth kinetics and dynamic properties of the plasma-assembled nanoparticles can be critical for the process quality in microelectronics as well as a number of other industrial applications including production of fine metal or ceramic powders, nanoparticle-unit thin film deposition, nanostructuring of substrates, nucleating agents in polymer and plastics synthesis, drug delivery systems, inorganic additives for sunscreens and UV-absorbers, and several others. Several unique properties of the chemically active plasma-nanoparticle systems are discussed as well.     

Iodine binding by amylopectin and stability of the amylopectin–iodine complex

The iodine binding capacity (IBC) of amylopectin (AP, from potatoes) is determined to be around 0.38% (w/w) of the total AP in the solution. The mass of iodine bound comprises about 13.6% of the mass of AP involved with the complex, suggesting that with every four iodine atoms bound there are 23 anhydroglucose residues (AGU). Since our previous study indicates that four iodine atoms within the helix of 11 AGUs form a chromophore unit in the API complex, only 48% of the AGUs (11 out of 23) in the AP molecule are directly involved with the iodine. The heat of reaction for the API complex formation is determined to be around ?47 kJ/mol of I–I units bound and is significantly lower in magnitude than that of the amylose-iodine (AI) complex [Biopolymers, 31 , 57 (1991)]. A possible mechanism has been proposed for the formation of AI and API complexes with fixed compositions. © 1994 John Wiley & Sons, Inc.     

基于磷光发射的有机电致白光器件的研究进展

由于旋轨偶合作用，磷光材料可以同时利用单线态和三线态激子，将其应用于电致白光器件的制作，能够显著提高器件的效率。本文根据磷光电致白光器件结构的不同，综述了国内外在磷光白光电致发光器件领域研究的主要进展。     

Synthesis and electropolymerization of 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline and its electrochromic properties

Synthesis of a new thiophene-based monomer; 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline (DDQ), was realized. The chemical structure of the monomer was characterized by ¹H NMR, FTIR and mass spectroscopy techniques. Electrochemical polymerization of DDQ and characterization of the resulting polymer [P(DDQ)] was performed. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. P(DDQ) has a low oxidation potential (0.9 V) and low band gap (1.73 eV) compared to polythiophene. In addition, dual-type polymer electrochromic device (ECD) based on P(DDQ) with poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, electrochromic switching, stability and open-circuit stability of the device were studied. It was observed that polymer have good switching time, reasonable contrast and optical memory.     

The local adsorption geometry and electronic structure of alanine on Cu{1 1 0}

The adsorption of alanine on Cu{1 1 0} was studied by a combination of near edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Large chemical shifts in the C 1s, N 1s, and O 1s XP spectra were found between the alanine multilayer and the chemisorbed and pseudo-(3 × 2) alaninate layers. From C, N, and O K-shell NEXAFS spectra the tilt angles of the carboxylate group (≈26° in plane with respect to and ≈45° out of plane) and the C-N bond angle with respect to could be determined for the pseudo-(3 × 2) overlayer. Using this information three adsorption geometries could be eliminated from five p(3 × 2) structures which lead to almost identical heats of adsorption in the DFT calculations between 1.40 and 1.47 eV/molecule. Due to the small energy difference between the remaining two structures it is not unlikely that these coexist on the surface at room temperature.     

Chemical locomotion

Research into the autonomous motion of artificial nano- and microscale objects provides basic principles to explore possible applications, such as self-assembly of superstructures, roving sensors, and drug delivery. Although the systems described have unique propulsion mechanisms, motility in each case is made possible by the conversion of locally available chemical energy into mechanical energy. The use of catalysts onboard can afford nondissipative systems that are capable of directed motion. Key to the design of nano- and micromotors is the asymmetric placement of the catalyst: its placement in an environment containing a suitable substrate translates into non-uniform consumption of the substrate and distribution of reaction products, which results in the motility of the object. These same principles are exploited in nature to effect autonomous motion.