Analysis of the Aggregation of an Anionic Porphyrin with a Cationic Surfactant at the Supercritical Carbon Dioxide–Water Interface using UV–Visible External Reflection Spectrometry
Analysis of the Aggregation of an Anionic Porphyrin with a Cationic Surfactant at the Supercritical Carbon Dioxide–Water Interface using UV–Visible External Reflection Spectrometry
复制标题
使用紫外可见外反射光谱法分析阴离子卟啉与阳离子表面活性剂在超临界二氧化碳-水界面的聚集
作者：
A. Ohashi;A. Yamagata;H.-B. Kim
研制了一种直接测量超临界二氧化碳(SC-CO2) -水界面吸附物的外反射（ER）光谱测量装置。用该装置研究了经十六烷基三甲基铵离子（CTA+）吸附制备的5,10,15,20-四苯基- 21h， 23h -卟啉四磺酸（H4tpps2 -）双质子化产物在带正电的sc - co2 -水界面上的聚集。利用s-和p-极化外反射（ER）光谱评估了h4tpps2单体和j -聚集体在sc - co2 -水界面上的取向。结果表明，h4tpps2 -单体的卟啉面与sc - co2 -水界面几乎平行，棒状h4tpps2 - j -聚集体的长轴也与sc - co2 -水界面几乎平行。研究了CTA+浓度和co2压力对ER谱的影响，发现CTA+浓度会引起界面h4tpps2物质的变化。随着co2压力的增加，界面CTA+浓度增加，界面物质由h4tpps2单体转变为h4tpps2 - j -聚集体。这表明通过控制SC-CO2的压力和温度可以改变其界面化学物质。据我们所知，这是第一份直接测量sc - co2 -水界面化学物质的报告。
An external reflection (ER) spectrometric device was developed to directly measure adsorbates at the supercritical carbon dioxide (SC–CO2)–water interface. The aggregation of diprotonated species of 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid (H4tpps2–) at the positively charged SC–CO2–water interface, prepared by adsorption by the cetyltrimethylammonium ion (CTA+), was studied using this device. Orientations of the H4tpps2–monomers and J-aggregates at the SC–CO2–water interface were assessed using s- and p-polarized external reflection (ER) spectra. It appeared that the porphyrin plane of the H4tpps2–monomer was nearly parallel to the SC–CO2–water interface, and that the long axis of the rod-like H4tpps2–J-aggregate was also nearly parallel to the interface. Dependence of the ER spectra on CTA+concentration and CO2pressure were investigated, and the interfacial CTA+concentration was found to cause changes in the interfacial H4tpps2–species present. Increasing the CO2pressure changed the interfacial species from the H4tpps2–monomer to the H4tpps2–J-aggregate because the interfacial CTA+concentration increased as the pressure increased. This suggests that the interfacial chemical species can be changed by controlling the pressure and temperature of the SC–CO2. This is the first report of direct measurements of the chemical species at the SC–CO2–water interface, as far as we know.