Effect of moisture adsorption on the broadband dielectric response of SiO2-based nanoporous glass

Abstract

Atmospheric water adsorbed by porous materials may significantly change its electrodynamic response in a wide frequency range. Mechanical and chemical stabilities of silicon dioxide along with a proven manufacturing method of porous SiO2 samples made it convenient for studying the effects of moisture adsorption on various parameters of the porous media. We report the dielectric properties of SiO2-based nanoporous glass in the frequency range of 20 Hz–400 THz at ambient atmospheric conditions and at a low residual pressure of ≤1 mbar. We observed a significant low-frequency dispersion of the complex dielectric permittivity and enhancement of dielectric loss for the porous sample exposed to the ambient moisture. In the terahertz range, the change in dielectric response is smaller and correlates with the moisture saturation of the sample.

Dielectric permittivity of organosilicate glass thin films on a sapphire substrate determined using time-domain THz and Fourier IR spectroscopy

“…The same band in the p-OSG10 film is the sum of the contributions from the Boson peak and the trapped water. The increase in the dielectric permittivity of the bulk porous vitreous SiO 2 sample in the THz range as a result of the adsorption of moisture from the atmosphere is approximately 10%-20% [35]. The concentration of trapped water in the isolated pores was much lower.…”

“…The measurements were performed at a residual pressure of less than 10 −2 mbar. The evacuation time was at least 30 min, which was sufficient to remove the weakly bound water from the pores of the sample [35]. Transmissivity spectra of two-layer samples of p-OSG films on sapphire substrates, as well as substrates without films, were obtained relative to the reference transmission measured with an empty aperture (a spectrometer hardware function).…”

Terahertz technology in intraoperative neurodiagnostics: A review

“…64 , TPS was applied to study the THz dielectric response of gelatin-embedded intact tissues, edematous tissues, and WHO Grades I -IV gliomas of the human brain ex vivo. To preserve tissues from hydration/dehydration, retain their original molecular properties during the THz measurements, and, thus, sustain their THz response unaltered (as compared to the freshly-excised tissues), gelatin slabs were used for the tissue fixation 158 . In Fig.…”

Температурная эволюция диэлектрического отклика alpha-лактозы моногидрата в терагерцовом диапазоне частот

“…Процессы гидратации и дегидратации лактозы активно изучаются с использованием различных подходов, включая методы ТГц импульсной спектроскопии [11][12][13][14], поскольку они чувствительны к влагонасыщенности пористых сред [15]. Изучению трансформации молекулярной структуры органических кристаллов методами ТГц спектроскопии также посвящен ряд работ [16,17], из которых, в частности, следует, что методы ТГц спектроскопии обладают достаточной чувствительностью к регистрации трансформации колебательного спектра при изменениях молекулярной структуры.…”