Terahertz Time-Domain Spectroscopy Study of Silica Aerogels and Adsorbed Molecular Vapors

Autor:	Daniel R. Grischkowsky, Jiangquan Zhang
Rok vydání:	2004
Předmět:	Heavy water Analytical chemistry Aerogel Surfaces Coatings and Films chemistry.chemical_compound Adsorption chemistry Materials Chemistry Physical and Theoretical Chemistry Absorption (chemistry) Spectroscopy Terahertz time-domain spectroscopy Fluoride Water vapor
Zdroj:	The Journal of Physical Chemistry B. 108:18590-18600
ISSN:	1520-5207 1520-6106
Popis:	We report the terahertz time-domain spectroscopy (THz-TDS) study of hydrophobic and hydrophilic silica aerogels, and the adsorption of several molecular vapors in the hydrophilic silica aerogel. The hydrophobic and hydrophilic samples have similar but discernible indices of refraction in the frequency range of 0.2−3.0 THz. Below 1.0 THz, the two samples have the same absorption, but starting from 1.0 THz, the absorption of the hydrophilic sample increases more rapidly with frequency. For the hydrophilic aerogel, a strong effect on adsorption is observed by THz-TDS for the vapors of water, heavy water, ammonia, methyl chloride, and methyl fluoride. The surface −OH groups can be replaced by −OD groups by dosing with heavy water, causing the change in the index of refraction and absorption. This replacement can be reversed by dosing the hydrophilic aerogel with water vapor. The volumetric method is used to determine the adsorption amount, which shows that the adsorbed molecules are in the submonolayer form. ...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::9bda558cfbf26de3a1a3bf114a988cb3 https://doi.org/10.1021/jp046869b Zobrazit plný text záznamu