Raman and infrared spectroscopic study of the anhydrous carbonate minerals shortite and barytocalcite

The Raman spectra of shortite and barytocalcite complimented with infrared spectra have been used to characterise the structure of these carbonate minerals. The Raman spectrum of barytocalcite shows a single band at 1086cm(-1) attributed to the (CO(3))(2-) symmetric stretching mode, in contrast to shortite where two bands are observed. The observation of two bands for shortite confirms the concept of more than one crystallographically distinct carbonate unit in the unit cell. Multiple bands are observed for the antisymmetric stretching and bending region for these minerals proving that the carbonate unit is distorted in the structure of both shortite and barytocalcite.     

Kosmotropic and chaotropic behavior of hydrated ions in aqueous solutions in terms of expansibility and compressibility parameters

Hydrated ions have fundamental applications in chemical and biological processes. Kosmotropic and chaotropic nature of hydrated ions affect the water structure in solutions depending upon their hydrophobicity or hydrophilicity nature. In present study Kosmotropic and chaotropic behavior of hydrated ions have been explained in terms of volumetric and acoustic parameters like apparent molar volume (V_ϕ), expansibility and compressibility factors for aqueous electrolytic solutions provide useful information about interactions among ions and water molecules. Results of V_ϕ showed that SO₄²⁻ ions due to stronger H-bonding with water molecules are termed as kosmotropes while Cl⁻ and HCO₃^– are chaotropes due to their weaker H-bonding with water molecules. More compressible structure of solutions in the presence of SO₄²⁻ ions indicated its kosmotropic behavior and comparatively less compressible structure of solutions in the presence of Cl⁻¹ and HCO₃^– ions renders them chaotropes. Results obtained from expansibility factor showed the dominance of electrostatic interactions over hydrophobic hydration of ions at higher temperatures. Greater values of expansibility factor for SO₄²⁻ ions as compared to Cl⁻¹ and HCO₃^– ions renders them kosmotropic ion while later are termed as chaotropes. Hence, thermo-acoustic parameters could be effectively used to describe the hydrogen bonding character of ionic solutions in terms of kosmotropic and chaotropic behavior of solutions.     

New sonochemiluminescence involving solvated electron in Ce(III)/Ce(IV) solutions

The moving single-bubble sonoluminescence of Ce³⁺ in water and ethylene glycol solutions of CeCl₃ and (NH₄)₂Ce(NO₃)₆ was studied. As found, a significant part of intensity of the luminescence (100% with cerium concentration less than 10^–4 M) is due to the sonochemiluminescence. A key reaction of sonochemiluminescence is the Ce⁴⁺ reduction by a solvated (or hydrated in water) electron: Ce⁴⁺ + e_s (e_aq) → *Ce³⁺. Solvated electrons are formed in a solution via electrons ejection from a low-temperature plasma periodically generated in deformable moving bubble at acoustic vibrations. Reactions of heterolytic dissociation of solvents make up the source of electrons in the plasma. In aqueous CeCl₃ solutions, the Ce⁴⁺ ion is formed at the oxidation of Ce³⁺ by OH radical. The latter species originates from homolytic dissociation of water in the plasma of the bubble, also penetrating from the moving bubble into the solution. The sonochemiluminescence in cerium trichloride solutions are quenched by the Br⁻ (acceptor of OH) and H⁺ ions (acceptor of e_aq). In water and ethylene glycol solutions of (NH₄)₂Ce(NO₃)₆, the sonochemiluminescence also quenched by the H⁺ ion. The sonochemiluminescence in CeCl₃ solutions is registered at [Ce³⁺] ≥ 10^–5 M. Then the sonochemiluminescence intensity increases with the cerium ion concentration and reaches the saturation plateau at 10^–2 M. It was shown that sonophotoluminescence (re-emission of light of bubble plasma emitters by cerium ions) also contributes to the luminescence of Ce³⁺ in solutions with [Ce³⁺] ≥ 10^–4 M. If the cerium concentration is more than 10^–2 M, a third source contributes to luminescence, viz., the collisional excitation of Ce³⁺ ions penetrating into the moving bubble.     

基于Taylor弥散理论的纳米粒子与蛋白质相互作用研究

在微流控芯片中将Taylor弥散分析(TDA)与激光诱导荧光检测(LIF)结合,测定了荧光素钠标记狗血清蛋白(FITC-DSA)的水合半径为(6.12±1.21)nm,扩散系数为(4.11±0.78)×10-11m2/s;然后,初步研究了FITC-DSA与不同粒径金纳米粒子(AuNPs)的相互作用.研究结果表明,不同粒径的AuNPs与蛋白质的作用不同;50 nm的AuNPs与FITC-DSA作用会导致其荧光信号增强.本研究为高通量测定纳米粒子与蛋白质相互作用提供了一种新方法.本方法具有简单快速、耗样量极少等优点,有助于深入了解纳米材料的毒性,推动安全纳米药物的发展.     

芘四磺酸钠水溶液激光闪光光解机理

采用激光闪光光解-瞬态吸收光谱技术研究了355nm激光作用下芘四磺酸钠(PyTS)水溶液的光化学反应机理及其产生水合电子的动力学行为.研究首次发现PyTS水溶液激发单线态(PyTS1*)在260nm、激发三线态(PyTS3*)在300nm及阴离子自由基(PyTS-?)在330nm处的特征吸收峰;分析了生成的水合电子(e-aq)的主要反应途径包括自猝灭反应及与PyTS的反应,得到水合电子与PyTS反应的准一级速率常数为2.7′105s-1;并计算得到在此实验条件下,PyTS水溶液经双光子吸收产生的水合电子量子产率为3.2′10-2.     

Hydrated electrons in water-in-oil microemulsion: a pulse radiolysis study

Half-life and yield of hydrated electron in water-in-oil microemulsion of cetyl trimethylammonium bromide-water-1-pentanol-cyclohexane system has been studied. Dose distribution calculation suggests scavenging of electrons that are generated in cyclohexane by water pools and hydroxyl radical generation by direct water radiolysis only. Dose distribution, half-life of e_aq⁻, generation and solvation of e_aq⁻ in this system and its comparison with other systems have been discussed.     

Zn(Ⅱ)在TiO2表面上的微观吸附模式研究

用延展X射线吸收精细结构(EXAFS)技术并结合密度泛函理论(DFT)研究了Zn(Ⅱ)在锐钛型TiO2表面上微观吸附结构。EXAFS结果表明, Zn(Ⅱ)在吸附时由自由水合状态下的Zn—O六配位八面体结构向四配位四面体结构转化, 中心Zn原子的第二配位层存在两种不同的Zn—Ti距离(R1=0.371和R2=0.332 nm). 用DFT方法对四配位水合Zn离子在簇Ti2O11H14上进行优化后发现, 四配位的Zn—O平均距离为0.200 nm; 外层Zn—Ti结合存在两种稳定的吸附模式: 单角吸附模式和更加稳定的双角吸附模式, 其Zn—Ti距离分别为0.369和0.335 nm. EXAFS结果与DFT计算结果吻合, 说明Zn(Ⅱ)在锐钛型TiO2表面上存在不同的亚稳平衡态吸附结构.     

Comparison of surface properties between kaolin and metakaolin in concentrated lime solutions

The surface adsorption of calcium hydroxide onto kaolin and metakaolin was investigated by monitoring with atomic emission spectroscopy and pH measurements the amounts of ions left in solution after exposing clays to calcium hydroxide solutions of various concentrations. Both clays adsorb calcium and hydroxyl ions but differently. Kaolin adsorbs calcium hydroxide not only at the edges of the clay particles but also onto the basal faces. The adsorbed hydrated calcium ions form a layer on the clay particle surfaces, preventing further dissolution of the clay mineral platelet. Metakaolin shows high pozzolanic activity, which provides the quick formation of hydrated phases at the interfaces between metakaolin and lime solutions. The nature of the hydration products has been investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA). The most important hydrated phases like CSH (hydrated calcium silicate) and C₂ASH₈ (gehlenite) have been identified.     

Path-integral molecular dynamics simulations of hydrated hydrogen chloride cluster HCl(H2O)4 on a semiempirical potential energy surface

Path-integral molecular dynamics simulations for the HCl(H₂O)₄ cluster have been performed on the ground-state potential energy surface directly obtained on-the-fly from semiempirical PM3-MAIS molecular orbital calculations. It is found that the HCl(H₂O)₄ cluster has structural rearrangement above the temperature of 300 K showing a liquid-like behavior. Quantum mechanical fluctuation of hydrogen nuclei plays a significant role in structural arrangement processes in this cluster.     

水合高氯酸盐+有机溶剂体系中氢氧化物电沉积的EQCM研究

采用电化学石英晶体微天平(EQCM)定量研究了含水合高氯酸盐的丙酮、DMF、DMSO、C2H5OH或CH3OH有机溶液中LiOH(或NaOH)的电沉积过程. 这种电沉积现象可归因于有机溶液中的溶解氧和共存水在负电位下电还原产生OH−, OH−与溶液中金属阳离子结合生成在非水溶剂中溶解度很小的氢氧化物而沉淀在电极表面, 从而引起压电参数的响应, 而使用四丁基溴化铵为支持电解质时这种现象不明显. 讨论了不同支持电解质、不同溶剂、支持电解质浓度和外加水浓度对氢氧化物电沉积的影响, 估算了氢氧化物沉淀的电极收集效率.