扫描探针显微镜的发明，使人们了解纳米、分子和原子尺度的超微结构，探测原子、分子间的力、电、磁及其复杂的物理和化学性质，以及进行单原子、单分子操纵成为现实。本文从探针技术与表面化学物理力学耦合的角度出发，首先对针尖的化...扫描探针显微镜的发明，使人们了解纳米、分子和原子尺度的超微结构，探测原子、分子间的力、电、磁及其复杂的物理和化学性质，以及进行单原子、单分子操纵成为现实。本文从探针技术与表面化学物理力学耦合的角度出发，首先对针尖的化学物理力学研究领域进行了概述，接着介绍了针尖的几种重要的化学修饰方法，包括金属薄膜、自组装单分子膜、胶体粒子及碳纳米管修饰；然后以理论与实验结合的方式介绍了几个研究活跃的领域：表面力及分子间力(主要包括Van der Vqaals力，双电层力，憎水亲合力，Casimir力和单键力等)的理论描述与测量，针尖的化学物理力学在化学力滴定和表面化学识别等研究中的应用。讨论了针尖与基底材料对测量力的影响。而这些复杂的原子、分子相互作用和物理、化学、力学及生物特性的实现均发生于小小针尖上，由此我们提出了“针尖力学”的概念。并且指出多场(如电场、磁场、超声、微波等)作用下，针尖的化学物理力学研究将成为力学交叉学科研究的重点和热点。展开更多
A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first sev...A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.展开更多
Cavity ring-down spectroscopy(CRDS)was utilized in combination with chemical titration with sulfur dioxide(SO_2)to quantify stabilized Criegee intermediates(s CIs)produced at low pressures(4–20 Torr)in ozonolysis rea...Cavity ring-down spectroscopy(CRDS)was utilized in combination with chemical titration with sulfur dioxide(SO_2)to quantify stabilized Criegee intermediates(s CIs)produced at low pressures(4–20 Torr)in ozonolysis reactions of cis-2-butene,2-methyl-2-butene,cyclopentene,and cyclohexene.The yield of stabilized s CI,acetaldehyde oxide(CH_3CHOO),from cis-2-butene ozonolysis decreased with decreasing pressure and reached to 0.05±0.04 at the zero-pressure limit.The nonsymmetric alkene 2-methyl-2-butene produced two stabilized s CIs,CH_3CHOO and acetone oxide((CH_3)_2COO),and their total yield decreased with decreasing pressure and reached 0.01±0.03 at the zero-pressure limit.For cyclopentene and cyclohexene,the s CI yields were essentially constant near zero,as expected of endocyclic alkenes.The nascent yields of s CI of various alkenes are compared.展开更多
文摘扫描探针显微镜的发明，使人们了解纳米、分子和原子尺度的超微结构，探测原子、分子间的力、电、磁及其复杂的物理和化学性质，以及进行单原子、单分子操纵成为现实。本文从探针技术与表面化学物理力学耦合的角度出发，首先对针尖的化学物理力学研究领域进行了概述，接着介绍了针尖的几种重要的化学修饰方法，包括金属薄膜、自组装单分子膜、胶体粒子及碳纳米管修饰；然后以理论与实验结合的方式介绍了几个研究活跃的领域：表面力及分子间力(主要包括Van der Vqaals力，双电层力，憎水亲合力，Casimir力和单键力等)的理论描述与测量，针尖的化学物理力学在化学力滴定和表面化学识别等研究中的应用。讨论了针尖与基底材料对测量力的影响。而这些复杂的原子、分子相互作用和物理、化学、力学及生物特性的实现均发生于小小针尖上，由此我们提出了“针尖力学”的概念。并且指出多场(如电场、磁场、超声、微波等)作用下，针尖的化学物理力学研究将成为力学交叉学科研究的重点和热点。
基金Project supported by the National Natural Science Foundation of China (Nos. 49971046 and 49831005).
文摘A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.
基金supported by the US National Science Foundation (CHE-1566636)UCMEXUS-CONACYT Doctoral Fellowship
文摘Cavity ring-down spectroscopy(CRDS)was utilized in combination with chemical titration with sulfur dioxide(SO_2)to quantify stabilized Criegee intermediates(s CIs)produced at low pressures(4–20 Torr)in ozonolysis reactions of cis-2-butene,2-methyl-2-butene,cyclopentene,and cyclohexene.The yield of stabilized s CI,acetaldehyde oxide(CH_3CHOO),from cis-2-butene ozonolysis decreased with decreasing pressure and reached to 0.05±0.04 at the zero-pressure limit.The nonsymmetric alkene 2-methyl-2-butene produced two stabilized s CIs,CH_3CHOO and acetone oxide((CH_3)_2COO),and their total yield decreased with decreasing pressure and reached 0.01±0.03 at the zero-pressure limit.For cyclopentene and cyclohexene,the s CI yields were essentially constant near zero,as expected of endocyclic alkenes.The nascent yields of s CI of various alkenes are compared.
