Comparing amorphous silica, short-range-ordered silicates and silicic acid species by FTIR

Abstract

There is increased interest in the terrestrial silicon cycle in the last decades as its different compounds and species have large implications for ecosystem performance in terms of soil nutrient and water availability, ecosystem productivity as well as ecological aspects such as plant–microbe and plant-animal feedbacks. The currently existing analytical methods are limited. Fourier-transform infrared spectroscopy (FTIR) analysis is suggested being a promising tool to differentiate between the different Si species. We report here on the differentiation of varying Si-species/Si-binding (in synthetic material) using FTIR-analyses. Therefore, we collected FTIR-spectra of five different amorphous silica, Ca-silicate, sodium silicate (all particulate), a water-soluble fraction of amorphous silica and soil affected by volcanic activity and compared their spectra with existing data. A decrease of the internal order of the materials analyzed was indicated by peak broadening of the Si–O–Si absorption band. Peak shifts at this absorption band were induced by larger ions incorporated in the Si–O–Si network. Additionally, short-range ordered aluminosilicates (SROAS) have specific IR absorption bands such as the Si–O–Al band. Hence, SROAS and Si phases containing other ions can be distinguished from pure amorphous Si species using FTIR-analyses.

Synthesis and Characterization of Novel Thiosalicylate-based Solid-Supported Ionic Liquid for Removal of Pb(II) Ions from Aqueous Solution

“…In activated silica gel, the silanol group was observed by the presence of broad -OH stretch at 3425 cm −1 . The siloxane group (Si-O-Si) asymmetric stretching was appeared at 1081 cm −1 and the corresponding symmetric stretching was observed at 793 cm −1 [ 23 ].…”

“…For Si-TS-SSIL, which contains the combination of activated silica gel and [MTMSPI][TS] ionic liquid, stretching vibrations of the Si-O-Si groups were observed at 1030 cm −1 [ 23 ]. The peaks observed in the range of 1550–1650 cm −1 were related to the C-N stretching of the imidazolium ring.…”

Hierarchical Porous SiO2 Cryogel via Sol-Gel Process

“…The simple interpretation of the fractal theory for the Porod-region was not carried out for the SAXS data of the cryogels owing to the “S” shape of the curve. The SAXS curve of the cryogel could be evaluated by Freltoft approximation results in unit sizes of 40–50 nm in the cryogel prepared from TEOS [ 24 ]. The dimension (slope) obtained by the Freltoft evaluation was 2.75.…”

“…The silicate units are usually represented by Q n , which refers to a silicon with n bridging oxygens to other silicon atoms. The different Q species have resonances in separate regions of the 29 Si MAS NMR spectrum [ 19 , 20 , 21 , 22 , 23 , 24 ]. The deconvolution of the NMR spectra was performed to obtain Q n distribution, using a regular assumption of Lorentzian functions for each type of Q n units.…”

Investigation on the influence of crosslinking and swelling properties of modified silica-chitosan films for the controlled removal of Alexandrium minutum

“…The crosslinking between chitosan and silica can take place when the silanol group of the silica reacted with the hydroxyl groups of the chitosan through condensation reaction to form Si-O-C bond (indicated in red line). The IR peak related to Si-O-C bond is normally can be seen around 1252 cm -1 [42]. However, it is di cult to distinguish due to the overlapping of different band structures.…”