Peak separation by derivative spectroscopy applied to ftir analysis of hydrolized silica

Abstract

A análise espectral só se torna confiável se o espectro é detalhadamente analisado quanto a todos os picos sobrepostos e ocultos. Neste trabalho são descritas as etapas para revelar e separar esses picos na faixa de 3000-4000 cm -1 em três espectros de absorção de infravermelho colhidos na superfície vítrea de fibras ópticas de sílica hidrolizada. A revelação dos picos foi feita com a análise da segunda e quarta derivada dos dados experimentais digitalizados, juntamente com o conhecimento disponível de espectroscopia de infravermelho da interação sílica-água na faixa espectral investigada. A separação de picos foi realizada com ajuste de curva usando quatro modelos distintos. O melhor ajuste foi alcançado com um modelo que descrevia os espectros com uma soma de picos do tipo Gaussiano. Mapas descrevendo os limites de ombro ("shoulder limits") e de detecção foram utilizados para validar os detalhes espectrais revelados.Reliable spectral analysis is only achieved if the spectrum is thoroughly investigated in regard to all hidden and overlapped peaks. This paper describes the steps undertaken to find and separate such peaks in the range of 3000 to 4000 cm -1 in the case of three different infrared absorption spectra of the glass surface of hydrolyzed silica optical fibers. Peak finding was done by the analysis of the second and fourth derivatives of the digital data, coupled with the available knowledge of infrared spectroscopy of silica-water interaction in the investigated range. Peak separation was accomplished by curve fitting with four different models. The model with the best fit was described by a sum of pure Gaussian peaks. Shoulder limit and detection limit maps were used to validate the revealed spectral features.

Pore Size-Dependent Structure of Confined Water in Mesoporous Silica Films from Water Adsorption/Desorption Using ATR–FTIR Spectroscopy

“…O-H stretching vibrations and the less intense overtone of water's bending vibration between 3000 and 3800 cm -1 provide rich information about the structure of silica as well as the adsorbed water 44,45 Figure 3 shows a close-up of the normalized bands in this spectral region corresponding to the adsorption branch in Figure 1B. With increased filling of the pores, a clear shift in the maximum of the spectra from 3230 cm -1 to 3400 cm -1 is visible.…”

Universal self-assembly of one-component three-dimensional dodecagonal quasicrystals

“…2b). To determine effective parameters in this case, we use the method of peak separation widely used in spectroscopy 41,42 . The method is based on using high order (2th and 4th) derivatives to separate overlapped peaks.…”

FTIR study of the relation, between extra-framework aluminum species and the adsorbed molecular water, and its effect on the acidity in ZSM-5 steamed zeolite

“…The gradual disappearance of the signals at 3785 and 3700-3642 cm -1 ( Figure 3) with the increase of the temperature during hydrothermal treatment, reveals small signals at 3640 cm -1 and 3683 cm -1 (zeolite sample HT760) that finally disappears in HT960. Most likely, the peak around 3640 cm -1 comes from O-H stretching vibrations of silanols (Si-OH), hydrogen bonded with other silanols or water molecules, inside the zeolite channels 45,46 . Theoretical studies made by Jungsuttiwong and coworkers 40 , allowed assigning the signal at 3683 cm -1 to "free O-H" stretching vibrations, pertaining to H 5 O 2 + ions adsorbed inside the ZSM-5 zeolite channels.…”