PEGylated Luminescent Gold Nanoclusters: Synthesis,Characterization, Bioconjugation,and Application to One‐ and Two‐Photon Cellular Imaging

Biocompatible, near‐infrared luminescent gold nanoclusters (AuNCs) are synthesized directly in water using poly(ethylene glycol)‐dithiolane ligands terminating in either a carboxyl, amine, azide, or methoxy group. The ≈1.5 nm diameter AuNCs fluoresce at ≈820 nm with quantum yields that range from 4–8%, depending on the terminal functional group present, and display average luminescence lifetimes approaching 1.5 μs. The two‐photon absorption (TPA) cross‐section and two‐photon excited fluorescence (TPEF) properties are also measured. Long‐term testing shows the poly(ethylene glycol) stabilized AuNCs maintain colloidal stability in a variety of media ranging from saline to tissue culture growth medium along with tolerating storage of up to 2 years. DNA and dye‐conjugation reactions confirm that the carboxyl, amine, and azide groups can be utilized on the AuNCs for carbodiimide, succinimidyl ester, and Cu^I‐assisted cycloaddition chemistry, respectively. High signal‐to‐noise one‐ and two‐photon cellular imaging is demonstrated. The AuNCs exhibit outstanding photophysical stability during continuous‐extended imaging. Concomitant cellular viability testing shows that the AuNCs also elicit minimal cytotoxicity. Further biological applications for these luminescent nanoclustered materials are discussed.     

纳米铜团簇在常温和升温过程中能量特征的分子动力学研究

采用分子动力学方法和F-S多体势函数，模拟研究纳米铜团簇常温下能量特征及其在升温直到熔化过程中的变化，确定了常温下纳米铜团簇的表面原子厚度和表面能，给出在不同温度下纳米铜团簇能量大小分布比例和能量的概率密度，细致描述了团簇升温过程团簇内部原子和表面原子之间不同的变化特征. 关键词： 铜团簇 分子动力学 能量特征 温度     

铜、银和铂原子纳米团簇负热容现象的分子动力学模拟研究

本文采用微正则分子动力学方法模拟研究了铂、铜和银原子纳米团族从固态到液态的熔化过程,得到热容量随温度变化关系,结果表明这三种金属纳米团簇在熔化过程中均出现了负热容现象,并通过对团簇热能随温度的变化关系以及团簇原子数径向分布的分析,探讨了产生负热容现象的微观机制.     

Bestimmung von Brom und Silber in metallorganischen Komplexen durch potentiometrische Titration

Zusammenfassung Nach Zersetzung des Komplexes wird das gebildete unlösliche Silberbromid mit metallischem Zink zu festem Silber und gelösten Bromidionen umgesetzt. Beide Komponenten werden potentiometrisch titriert. Die Standardabweichung beträgt 0,5 bzw. 1%.Teil eines Vortrags anläßlich der Tagung Euroanalysis I, 28. 8.–1.9. 1972 in Heidelberg.     

Interaction of humic and fulvic acids with nanoclusters of aluminum hydroxo cations on the surface of kaolinite according to IR spectroscopy data

We chemically modified the surface of kaolinite with nanoclusters of aluminum hydroxo cations. We have determined their composition and sizes. We have used IR spectroscopy to establish the interaction between the carbonyl and -diketone groups of fulvic and humic acids with the Lewis acid sites: coordination unsaturated Al³⁺ cations of the Al₁₃ nanoclusters. We have obtained spectral evidence for hydrogen bond formation between the carboxyl groups of fulvic acid and the hydroxyl groups of the aluminum hydroxo cations.__________Translated from Teoreticheskaya i Éksperimentalnaya Khimiya, Vol. 41, No. 1, pp. 45–49, January–February, 2005.     

表面氧钝化碳化硅纳米团簇电子结构和光学性质的第一性原理研究

基于密度泛函理论(DFT)和广义梯度近似(GGA),对氧钝化条件下4H-SiC纳米团簇的电子结构和光学性质进行了研究。计算了不同直径的4H-SiC纳米球氧钝化后的能带结构、电子态密度和光学性质。团簇的尺度在0.4~0.9 nm之间,构建表面仅存在硅氧双键和表面仅存在碳氧双键的两种模型。研究表明硅氧双键和碳氧双键所引起的缺陷态位于原4H-SiC的价带和导带之间,并且缺陷态与价带顶的能量差随纳米团簇颗粒直径的增大而减小;缺陷态主要是由Si原子外层电子和氧原子外层电子轨道杂化引起的。同时,由于氧的存在,对碳化硅的结构产生一定的影响,这也是缺陷态形成的一个原因。另外,碳氧双键和硅氧双键钝化对4H-SiC纳米团簇的光学性质有着不同的影响。在表面仅存在C=O的情况下,4H-SiC纳米团簇表现出各向同性的性质。在表面仅存在Si=O的情况下,4H-SiC纳米团簇表现出各向异性的性质。     

Point defect and diffusion properties in oxides from high temperature creep

A study of high temperature creep properties of non-stoichiometric CU₂O, CoO and NiO has been performed at various temperatures and oxygen activities (Po ₂). Creep rates are directly related to point defects responsible for the diffusion of the slowest species. These point defects have been tentatively identified by the Po₂ dependence of creep rate which does not depend on the detailed mechanism of deformation.     

The second-order elastic constants of an AgBr-(56.6%) AgCl mixed crystal from 20°C to 400°C

Abstract

Initial measurements of the second-order elastic constants of an AgBr-(56.6%) AgCl mixed crystal have been made from 20—400°C. Over this temperature range, C'₁₁ decreased by 44%, C' by 71%, C₄₄ by 22%, C₁₁ by 53%, C₁₂ by 40%, and B _s by 46%. The decreases in the elastic constants are linear until approximately 280°C, whereupon all but C' begin to decrease more rapidly than linearly with variations from linearity of 4—20% at 400°C and C' remains linear at all temperatures. This anomalous behavior is similar to other silver halide physical properties and may be attributed to the unusually high defect concentration at high temperatures. Similar elastic constant changes are seen in superionic conductors near the superionic transition, indicating that the silver halides may be starting the transition to a superionic state when the halide sublattice melts and the transition is frustrated.     

Lüders deformation and superplastic flow of metals extruded by KOBO method

The work brings the results of the study on mechanical properties of some metallic materials subjected to very large plastic deformation by KOBO extrusion. The unexpected features of the KOBO products like Lüders deformation in pure metals and superplastic flow in coarse grain materials are discussed in terms of micro- and nano-scale elements of their structure. The choice to the experiment materials having different crystallographic and phase structure (commercial purity aluminium, multiphase aluminium 7075 alloy, pure zinc and multiphase magnesium AZ91 alloy) and different history (extrusion, casting) allowed to identify the common nano-size elements of the structure generated during the KOBO deformation which seems to be responsible for the mechanical behaviour of these materials. In particular, clusters of point defects (self-interstitials) formed under the KOBO extrusion conditions (cyclic change in the deformation path, high hydrostatic pressure) were found in these materials regardless of grain size and material early history. They correlate with appearance of unstable Lüders-like or even Portevin–LeChatelier deformation at ambient and superplastic flow at elevated temperatures.     

Predicting absorption spectra of silver-ligand complexes

The detailed structures of most of ligand-stabilized metal nanoclusters (NCs) remain unknown due to the absence of crystal structure data for them. In such a situation, quantum-chemical modeling is of particular interest. We compared the performance of different theoretical methods of geometry optimization and absorption spectra calculation for silver-thiolate complexes. We showed that the absorption spectra calculated with the ADC(2) method were consistent with the spectra obtained with CC2 method. Three DFT functionals (B3LYP, CAM-B3LYP, and M06-2X) failed to reproduce the CC2 absorption spectra of the silver-thiolate complexes.