光谱学与光谱分析, 2009, 29 (12): 3315, 网络出版: 2010-01-04
共聚焦拉曼光谱研究ZnSO4 微液滴的风化过程
Confocal Raman Study on ZnSO4 Droplets in the Efflorescence Process
摘要
通过共聚焦拉曼原位光谱技术在分子水平上研究了沉积在聚四氟乙烯基底上的ZnSO4微液滴的风化过程。根据获得的高信噪比的Raman光谱,详细探讨了湿度降低时ZnSO4微液滴中Zn2+和SO离子的缔合行为,即经由单齿、双齿最终转化为复杂的链状或网状接触离子对。利用曲线拟合技术对其光谱的ν1-SO峰进行分峰,获得了不同湿度下ZnSO4微液滴中各组分的量化信息:高湿度时,液滴中主要包含自由的水合SO;随着湿度降低,自由SO逐渐向单齿、双齿接触离子对转化,并在湿度为66%和34%时分别达到其最大值;继续降低湿度,复杂的链状或网状接触离子对逐渐成为液滴中的主要成分。
Abstract
Confocal Raman technique was used to investigate the structure changes of the ZnSO4droplets deposited on Teflon substrate in the efflorescence process at the molecular level. Upon decreasing the relative humidity(RH), the symmetric stretching band(ν21/sub>-SO)of ZnSO4droplet blue shifted from 981 cm-1gradually to 987,998 and 1008 cm-1, respectively, indicating that the free SO ion associates with Zn2+ ion as the solution concentration increases and forms various contact ion pairs (CIPs), i. e., monodentate,bidentate and complicated multidentate chain-structured or web-structured CIPs. Accordingly, two obvious transition points were also observed in the hygroscopic curveof ZnSO4droplet, implying the structure transformations in thedroplet. In order to obtain the information about the contents and evolutions of variouscomponents in the droplets, curve fitting technique was used to extract the components at positions of 981,987,998 and 1008 cm-1in the spectral range of 945-1065 cm-1re-presenting the free SO ion, monodentate, bidentate and complicated CIPs, respectively. The results indicated that the main component in droplets was free hydrated SO ion at high RHs. With decreasing the RH, monodentate and bidentate CIPs were formed by Zn2+ and SO and achieved their highest contents at RHs of 66% to 34%, respectively. Further decreasing the RH, the monodentate and bidentate CIPs gradually changed into multidentate chain-structured CIPs or complicated CIPs webs, which became the main components in supersaturated ZnSO4 droplets as the RH decreased below 34%.
肖寒霜, 王良玉, 张韫宏. 共聚焦拉曼光谱研究ZnSO4 微液滴的风化过程[J]. 光谱学与光谱分析, 2009, 29(12): 3315. XIAO Han-shuang, WANG Liang-yu, ZHANG Yun-hong. Confocal Raman Study on ZnSO4 Droplets in the Efflorescence Process[J]. Spectroscopy and Spectral Analysis, 2009, 29(12): 3315.
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