Study of the Acidic Sites and Their Modifications in Mesoporous Silica Synthesized in Acidic Medium under Quiescent Conditions

Ramírez, Alejandro; López, Betty L.; Sierra, Ligia

doi:10.1021/jp0351472

Cited by 59 publications

(63 citation statements)

References 20 publications

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“…[24,25] Secondly, silica species are less-condensed, linear oligomers in acidic conditions (M1 synthesis), while in alkaline solution (M2 synthesis), they contain more crosslinked clusters. [26] The 29 Si MAS-NMR (MAS: magic-angle-spinning) spectra of the samples synthesized in acidic conditions have a Q 3 /Q 4 ratio above unity accompanied with clear Q 2 peaks, [27] implying incomplete polymerization and condensation of the silanol groups. However, the Q 2 peaks disappeared in the spectra of the analogue sample synthesized under basic conditions and the Q 3 and Q 4 peak areas seemed very similar, which indicates the relative complete condensation between the silanol groups.…”

Section: Full Papermentioning

confidence: 99%

Fabrication of Metal Oxides Occluded in Ordered Mesoporous Hosts via a Solid‐State Grinding Route: The Influence of Host–Guest Interactions

Wang

et al. 2006

Adv Funct Materials

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Solid‐state grinding is a simple and effective method to include guest species into the channels of ordered mesoporous materials with a different degree of filling. After calcination, a monolayer or several monolayers of guest species can not only form highly dispersed oxide species and other surface species on the hosts whether the template is occluded in the channels or not, but the guest species can also fill the mesoporous channels in the host and thus lead to nanowires or nanoarrays. Solid‐state salt inclusion is faster and more convenient than other inclusion routes. The absence of a solvent not only saves the time otherwise needed for evaporation but also leads to a higher degree of filling through a simple inclusion step as the void space in the pores is not occupied by the solvent. Also, the lack of competitive adsorption of solvent molecules enhances the interaction between the guest species included and the silica wall, which facilitates the high dispersion of oxide species. However, host–guest interactions that are too strong may disturb the self‐crystallization of guest species in the mesopores leading to imperfect nanocasting of the mesostructure.

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Section: Full Papermentioning

confidence: 99%

Fabrication of Metal Oxides Occluded in Ordered Mesoporous Hosts via a Solid‐State Grinding Route: The Influence of Host–Guest Interactions

Wang

et al. 2006

Adv Funct Materials

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“…These bands are due to pyridine interacting with hydrogen-bonded and free weakly acidic silanol groups, respectively (Bronsted groups). 33,34 The signal around 1633 cm -1 for S-Al samples is assigned to pyridine interacting with tetrahedral or octahedral Al in Bronsted and Lewis sites, respectively. 34 The 27 Al NMR was used to differentiate the coordination of the aluminium atom in the structure (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…33,34 The signal around 1633 cm -1 for S-Al samples is assigned to pyridine interacting with tetrahedral or octahedral Al in Bronsted and Lewis sites, respectively. 34 The 27 Al NMR was used to differentiate the coordination of the aluminium atom in the structure (Figure 2). The 27 Al NMR spectrum shows just a signal at 53 ppm typically assigned to tetrahedral aluminium atoms suggesting the formation of Bronsted groups, because of the formation of Al-O-Si bonds in the structure.…”

Section: Resultsmentioning

confidence: 99%

Polymerization of Aniline in Different Sba-16 Silica Hosts

Giraldo¹,

Vélez²,

Mesa³

2016

Química Nova

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publicado na web em 06/06/2016Polyaniline-silica composites made with mesoporous silica have been reported to improve the mechanical properties of the free polymer. However, there are not many studies about the effect of the chemical and physical properties of the inorganic material used as hosts over the final properties of polyaniline and the composites. Here, polyaniline-silica composites, exhibiting electrical conductivity, were synthesized using different types of SBA-16 mesoporous silica as hosts. The effects of the characteristics of the hosts in the polymerization kinetic, molecular weight and electrical conductivity of the final polymer were studied. The composites showed higher electrical conductivity in comparison with polyaniline synthesized under similar conditions of this work but in the absence of silica. The use of silica allowed to obtain composites with defined morphology, which did not occur in the absence of these hosts. From the results of this work, it can be concluded that SBA-16 mesoporous silica hosts have a bifunctional role in the formation of polyaniline-silica composites: the hosts behaved like nucleation sites, which favors polymerization of high molecular weight polyaniline and they catalyzed the polymerization reaction, especially when aluminum is present in the structure of the host.

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“…The high temperature treatment of silica induces the following condensation reaction between associated silanol (SiOH) groups to form siloxane (SiOSi) moieties: [20,25,26,[39][40][41][42][43][44] …”

Section: Ftir Analysismentioning

confidence: 99%

Hydroxylation of the silica in microfabricated thin layer chromatography plates as probed by time-of-flight secondary ion mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

Kanyal

Singh

Cushman

et al. 2014

Surf. Interface Anal.

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Microfabricated silica thin layer chromatography (TLC) plates have previously been prepared on patterned carbon nanotube forests. The high temperatures used in their fabrication reduce the number of hydroxyl groups on their surfaces. Fortunately, silica can be rehydroxylated. In diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), a silanol peak below 3740 cm À1 indicates a well-hydroxylated silica surface that is fit for chromatography. Hydroxylations of our materials with HF are so effective that it is not possible to discern the position of this peak. In contrast, this signal is discernable when the plates are treated with NH 4 OH. To find a more convenient method for studying the surfaces of TLC plates, time-of-flight secondary ion mass spectroscopy (ToF-SIMS) was considered. ToF-SIMS is advantageous because multiple microfabricated TLC plates must be scraped to obtain enough silica for one DRIFT analysis, while static SIMS can be performed on very small regions (500 × 500 μm 2 or less) of individual plates. Ratios of the SiOH + and Si + ToF-SIMS signals for microfabricated TLC plates correlated well with~3740 cm À1 silanol peaks from DRIFT. Thus, SIMS allows direct analysis of all of our treated and untreated plates, including those hydroxylated with HF. The best hydroxylation condition for HF, which was better than any studied for NH 4 OH, was around 150 ppm at room temperature. The best hydroxylation condition for NH 4 OH was 50°C for 72 h. ToF-SIMS versus DRIFT results of commercial TLC plates were also obtained and evaluated.

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Study of the Acidic Sites and Their Modifications in Mesoporous Silica Synthesized in Acidic Medium under Quiescent Conditions

Cited by 59 publications

References 20 publications

Fabrication of Metal Oxides Occluded in Ordered Mesoporous Hosts via a Solid‐State Grinding Route: The Influence of Host–Guest Interactions

Fabrication of Metal Oxides Occluded in Ordered Mesoporous Hosts via a Solid‐State Grinding Route: The Influence of Host–Guest Interactions

Polymerization of Aniline in Different Sba-16 Silica Hosts

Hydroxylation of the silica in microfabricated thin layer chromatography plates as probed by time-of-flight secondary ion mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

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