Quantitative measurement of the deformation of ultra-thin platinum foils during adsorption and reaction of CO and O2

An ultra-thin self-supporting Pt-foil with a thickness of 300 nm and 4 mm diameter has a heat capacity of only 10 μJ/K. Thus, even small amounts of heat deposited within the thin metal foil cause a significant temperature increase. During the adsorption of, for example, CO heat in the order of 30 μJ/ML is released into the metal. If the rim of a Pt(1 1 0) single crystal foil is rigidly mounted on a substrate, a temperature increase of the foil induced by adsorption and reaction of CO and O₂ causes thermo-elastic stress. This will lead to macroscopic deformations of the metal foil. To quantify these deformations an imaging Michelson-interferometer was set up, capable to detect small deflections of the ultra-thin Pt catalyst down to 10-20 nm. Adsorption of CO and O₂ causes a clear mechanical response of the Pt foil. Depending on sample temperature and partial pressures of the reactants fronts and pulses of deformation were found. The system can be calibrated by using continuous and chopped laser light. The optical properties of the catalytic surface change in the presence of adsorbates. This complicates the analysis, but can be avoided in an improved setup.     

Anti-microbial Activities of Protic Ionic Liquids Studied with Microcalorimetry Method

The anti-microbial activities of seven protic ionic liquids(ILs) against Escherichia coli and Staphylococcus aureus were studied by a micro-calorimetric method at 310 K.The bacterial growth rate constants were determined based on the bacterial growth power-time curves,andminimum biocidal concentrations were estimated.The results indicate that the protic ILs studied show inhibitory activities on the bacteria,implying a potential eco-toxicity to the microorganisms in the water system.Moreover,the inhibition e...     

不同条件下离体大鼠肝脏线粒体能量代谢微量热分析

为了探究线粒体的能量代谢过程,本文以离体大鼠肝脏线粒体为模型,利用多通道、高灵敏度的热活性检测仪TAM Ⅲ,实时监测了不同线粒体浓度、不同底物、不同缓冲液、几种呼吸抑制剂以及Ca²⁺和线粒体渗透转换孔抑制剂CsA存在时线粒体的能量代谢,获得了完整的热功率―时间曲线,并通过计算得到了线粒体能量代谢的热动力学参数。通过分析发现：（1）线粒体浓度越大,代谢越快;（2）直接底物琥珀酸钠使线粒体代谢更快;（3）高浓度Ca²⁺能够刺激线粒体快速产热,且在长期代谢进程中,线粒体渗透转换孔抑制剂CsA并不能改变Ca²⁺造成的影响;（4）不同缓冲液对线粒体代谢的影响基于其组分的不同,缓冲液中含有呼吸底物;（5）呼吸抑制剂都能抑制线粒体的能量代谢,尤其是复合物IV的抑制剂NaN₃,高浓度下使代谢停止。     

细菌变异株生长热谱研究

用微量热法研究微生物的生长与代谢,是生物热力学一个新的研究领域.我们已经测得细菌生长的完整热谱,这种热谱具有良好的重现性和明显的特征性,可以作为细菌的“指纹图”对其进行种的分类和鉴定[1～5].但在研究中发现,同种细菌不同变异株的生长图谱略有差异,若培养基选择?..     

微量热法研究漆酶和3,4,5-三羟基苯甲酸的反应

用LKB－2107型微量热系统,在不同的温度(pH＝7.4)条件下,测定了3,4,5－三羟基苯甲酸与漆酶反应的摩尔反应烙、米氏常数、反应速率常数、漆酶的活性并计算了结合能、活化自由能、活化能和活化烟等.在此基础上,应用过渡态理论,从能量变化的角度,对其催化过程进行了分析.由活化摘(△S_≠^T＜0)得出酶－底物过渡态的结构较酶－底物复合物更为有序的结论.     

Entropic Contributions to Sodium Solvation and Solvent Stabilization upon Electrochemical Sodium Deposition from Diglyme and Propylene Carbonate Electrolytes

The formation of an appropriate solid electrolyte interphase (SEI) at the anode of a sodium battery is crucially dependent on the electrochemical stability of solvent and electrolyte at the redox potential of Na/Na⁺ in the respective system. In order to determine entropic contributions to the relative stability of the electrolyte solution, we measure the reaction entropy of Na metal deposition for diglyme (DG) and propylene carbonate (PC) based electrolyte solutions by electrochemical microcalorimetry at single electrodes. We found a large positive reaction entropy for Na⁺ deposition in DG of Δ_R 234 J mol⁻¹ K⁻¹ (c.f.: Δ_R 83 J mol⁻¹ K⁻¹), which signals substantial entropic destabilization of Na⁺ in DG by about 0.73 eV, thus increasing the stability of solvent and electrolyte relative to Na⁺ reduction. We attribute this strong entropic destabilization to a highly negative solvation entropy of Na⁺, due to the low dielectric constant and high freezing entropy of DG.