NMR and IR spectroscopy of silica aerogels with different hydrophobic characteristics

El-Rassy, Houssam; Pierre, Alain C.

doi:10.1016/j.jnoncrysol.2005.03.048

Cited by 151 publications

(104 citation statements)

References 20 publications

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“…The hydrophobic character of such glasses has been verified by several means including contact angle measurements [43], solid-state 29 Si MAS NMR, and Fourier transform infrared spectroscopy [17,44]. Although most enzymes prefer an aqueous environment, it is rational to place lipases in a hydrophobic environment because these enzymes mediate reactions at lipid-water interfaces and because the substrates of these enzymes are highly nonpolar molecules.…”

Section: Discussionmentioning

confidence: 99%

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

et al. 2008

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Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol-gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′) 3 , featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0-15%. At a fixed molar content of 5% RSi(OR') 3 , the helical structure of apomyoglobin increased with the chain length of the R-group, i.e. methyl < ethyl < n-propyl < n-butyl < n-hexyl. This trend also was observed for the tertiary structure of ribonuclease A, suggesting that protein folding and biological activity are sensitive to the hydrophilic/hydrophobic balance of neighboring surfaces. The observed changes in protein structure did not correlate with total surface area or the average pore size of the modified glasses, but scanning electron microscopy images revealed an interesting relationship between surface morphology and alkyl chain length. The unexpected benefit of incorporating a low content of hydrophobic groups into a hydrophilic surface may lead to materials with improved biocompatibility for use in biosensors and implanted devices.

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Section: Discussionmentioning

confidence: 99%

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

et al. 2008

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“…As shown in Figure 3 A, there is a peak at 3400.72 cm -1 related to the hydroxyl functional group (-OH) before phenol adsorption (25). The peak that appeared around 1600 to 1700 cm -1 is related to stretching vibration of OH groups as a result of physical absorption of water on the particles (26 be assigned to phenolic C-OH stretching (27). The peak around wave number of 619 cm -1 is due to the phenol ring (28).…”

Section: Silica Aerogel Characteristicsmentioning

confidence: 97%

“…In the NMR spectra, illustrated in Figure 4, a chemical shift around 2.2δ appeared, which can be referenced to Si-OH (27). lic -OH group and the chemical shift in the region of 7.2δ can be attributed to phenolic aromatic ring (32).…”

Section: Characterization Of Silica Aerogelmentioning

confidence: 99%

Preparation, Characterization, and Application of Silica Aerogel for Adsorption of Phenol: An In-Depth Isotherm Study

et al. 2018

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This study evaluated silica aerogel as an adsorbent for phenol removal from aqueous solutions. Silica aerogel was prepared through the sol-gel process and characterized by different analyses. Then, it was used for phenol removal under various conditions of operational parameters. Also, twelve isotherm parameters were employed to describe the behavior of phenol-silica aerogel adsorption system. The chemical structural analysis confirmed -OH functional groups in amorphous SiO2 and proved the adsorption of phenol onto the surface of silica aerogel. The findings of the adsorptive behavior of silica aerogel toward phenol showed increasing pH, up to 8.5, and contact time, and adsorbent dose increased the phenol removal. The removal efficiency reached over 90% when phenol concentration was below 50 mg L -1 . The reaction kinetics followed the pseudo-first order model. The isotherm study showed that equilibrium adsorption data were well-described by Freundlich and Halsey equations, among two-parameter isotherms, and Hill, Sips, and Koble-Corrigan, among three-parameter isotherms. Jovanovic and BET were the worst isotherm models for prediction of experimental equilibrium data. The maximum adsorption capacity of 75.23 mg.g -1 was calculated in phenol-silica aerogel adsorption system. The study showed silica aerogel as an efficient adsorbent to remove phenol from phenol-containing solutions.

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“…The mean peak is associated with the stretching vibration of Si-O-Si [11-12 different bending vibrations attributed to Si are indicated in the figure. The bands located at 555 cm and 950 cm -1 are associated with Si-O bending vibrations of no bridging Si-OH bonds and stretching vibration respectively Si [13][14][15].…”

Section: Cmss-2017mentioning

confidence: 99%

“…The mean peak is associated with the 12]. In addition, different bending vibrations attributed to Si-O-Si [13][14][15] are indicated in the figure. The bands located at 555 cm -1 O bending vibrations OH bonds and stretching vibration In addition, we can notice that the mean band of SiO2-1 spectra after reaction with and without the presence of 1 before reaction as This pronounced shift may be connected to the ].…”

Section: Cmss-2017mentioning

confidence: 99%

Study of structural short order and surface changes of SiO₂ compounds

et al. 2018

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Abstract. In this work dependence between structure, surface and reactivity of SiO 2 is investigated. Different samples are prepared with and without the presence of calcium cations and are characterized by different techniques. The FTIR frequency shifting of the bridging oxygen stretching vibration Si-O-Si and the binding energy shiftingof the Si2p and O1s photoelectron peaks have been observed and discussed. Results show the effect of presence of calcium on the structural change, surface and reactivity of SiO 2 aggregate. After reaction, a structural and SiO 2 surface changes occur, as the FTIR spectra illustrate depending on the presence of the calcium cations.

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NMR and IR spectroscopy of silica aerogels with different hydrophobic characteristics

Cited by 151 publications

References 20 publications

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Preparation, Characterization, and Application of Silica Aerogel for Adsorption of Phenol: An In-Depth Isotherm Study

Study of structural short order and surface changes of SiO₂ compounds

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NMR and IR spectroscopy of silica aerogels with different hydrophobic characteristics

Cited by 151 publications

References 20 publications

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

Preparation, Characterization, and Application of Silica Aerogel for Adsorption of Phenol: An In-Depth Isotherm Study

Study of structural short order and surface changes of SiO2 compounds

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Study of structural short order and surface changes of SiO₂ compounds