The Role Played by Salts in the Formation of SBA-15, an in Situ Small-Angle X-ray Scattering/Diffraction Study

Teixeira, Cilâine Verônica; Amenitsch, Heinz; Linton, Peter; Lindén, Mika; Alfredsson, Viveka

doi:10.1021/la1043798

Cited by 39 publications

(51 citation statements)

References 53 publications

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“…The salt-induced increase in the size of the micelles and dehydration were also observed in recent smallangle neutron scattering (SANS) [51] and small-angle X-ray scattering (SAXS) [52] studies. This increase in size has been attributed to dehydration and counterion condensation.…”

Section: Discussionsupporting

confidence: 62%

Effect of NaCl on ESPT‐Mediated FRET in a CTAC Micelle: A Femtosecond and FCS Study

et al. 2012

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Femtosecond upconversion, single-molecule fluorescence resonance energy transfer (sm-FRET) and fluorescence correlation spectroscopy (FCS) are applied to study the competition between excited-state proton transfer (ESPT) and FRET [to rhodamine 6G (R6G)] of 8-hydroxypyranine-1,3,6-trisulfonate (HPTS) in cetyltrimethylammonium chloride (CTAC) micelles. Pyranine exhibits dual emission at λ(em)=430 nm for ROH and 520 nm for RO(-). The absorption spectrum of R6G (acceptor) has very good overlap with the RO(-) emission and poor overlap with ROH emission. It is observed that FRET occurs readily from the RO(-)* state of HPTS (donor) to R6G (acceptor). Multiple timescales of FRET were detected from the rise time of acceptor emission. The different timescales correspond to different donor-acceptor distances. The ultrafast components (8.5 and 13 ps) are assigned to FRET at a close contact of donor and acceptor (≈20 Å). The longer components (500 and 800 ps) arise from long-distance FRET from the donor to the acceptor (≈40 Å) located in different regions of the CTAC micelle. The larger donor-acceptor distances agree with those obtained from an sm-FRET study. On addition of 4 M NaCl to CTAC, the rate of proton transfer (k(PT)) slowed by about eight and two times, respectively, for the fast and slow sites of the CTAC micelle. As a result, the intensity of the ROH emission increases and that of RO(-) decreases. The decrease in the intensity of the RO(-) emission causes a decrease in the efficiency of FRET.

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Section: Discussionsupporting

confidence: 62%

Effect of NaCl on ESPT‐Mediated FRET in a CTAC Micelle: A Femtosecond and FCS Study

et al. 2012

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“…Addition of inorganic salts, such as NaCl, KCl, and K 2 SO 4 , increases the pore size [131,139,170,171]. As discussed in Section 3.3.3, addition of salts cause dehydration of ethylene oxide units from hydrated PEO from the side of the PPO core.…”

Section: Salt Additions and Acidic Sourcementioning

confidence: 99%

“…The formation rate of the material depends on several parameters, such as the choice of silica precursor [105], ions from salts or acids [102,105,131], and temperature [132]. By altering these parameters, a deeper understanding of the formation mechanism for SBA-15 can be found.…”

Section: Kineticsmentioning

confidence: 99%

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Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

Björk¹

2013

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On the cover, the structure of SBA-15 is illustrated. Inside the pores SEM micrographs have been inserted showing (clockwise from the top): rods, fibers, a film consisting of rods grown on a substrate, a film consisting of platelets grafted on a substrate, short rods, and platelets. In the center the sheet morphology is presented.© Emma Björk, unless otherwise stated.ISBN: 978-91-7519-516-2 ISSN: 0345-7524 Printed by LiU-tryck, Linköping, Sweden, 2013 Research is formalized curiosity. It is poking and prying with a purposeZora Neale Hurston (1903Hurston ( -1960 i ABSTRACTCatalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material's morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter.In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH 4 F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method.It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH 4 F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH 4 F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants.ii T...

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“…26,30 They can be tailored to offer large specific surface area, large specific pore volume, uniform pore size distribution, and chemical and mechanical stability compatible with almost any enzyme reactor design in principle. Properties of OMSM can be fine-tuned by the synthesis conditions [31][32][33] : the temperature and time of the key synthesis steps (hydrolysis, condensation and hydrothermal treatment) [34][35][36] ; the organic co-solvents, the co-surfactant and/or the organic swelling agents employed [37][38][39][40][41] ; the addition of salts to the synthesis medium 36,42 ; and the type of silica precursor used. 43 A difficult problem of immobilization on silica is to find a proper way of fixing the enzyme on the solid surface.…”

Section: Introductionmentioning

confidence: 99%

Oriented Coimmobilization of Oxidase and Catalase on Tailor-Made Ordered Mesoporous Silica

et al. 2017

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Mesoporous silica materials are promising carriers for enzyme immobilization in heterogeneous biocatalysis applications. By tailoring their pore structural framework, these materials are designable for appropriate enzyme binding capacity and internal diffusivity. To supply O 2 efficiently to solid-supported immobilized enzymes represents a core problem of heterogeneously catalyzed oxidative biotransformations. In this study, therefore, we synthesized and compared three internally well-ordered and two amorphous silica materials as enzyme carriers, each of those with pore sizes of ≥10 nm, to enable the co-immobilization of D-aminoacid oxidase (93 kDa) and catalase (245 kDa). Both enzymes were fused to the silica-binding module Z basic2 to facilitate their selective and oriented immobilization directly from crude protein mixtures on native silica materials. Analyzing the effects of varied pore architecture and internal surface area on the performance of the immobilized bienzymatic system, we showed that a uniform pore structural framework was beneficial for enzyme loading (≥ 70 mg protein/g carrier), immobilization yield (≥ 90%), surface and pore volume filling without hindered adsorption, and catalytic effectiveness (≥ 60%) of the co-immobilizate. Using the best carrier LP-SBA-15, we obtained a solid oxidase-catalase preparation with an activity of 2000 µmol/(min g_material) that was recyclable and stable during oxidation of D-methionine. These results affirm a strategy of optimizing immobilized O 2 -dependent enzymes via tunable internal structuring of the silica material used as carrier. They thus make a significant advance towards the molecular design of heterogeneous oxidation biocatalysts on mesoporous silica supports.

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The Role Played by Salts in the Formation of SBA-15, an in Situ Small-Angle X-ray Scattering/Diffraction Study

Cited by 39 publications

References 53 publications

Effect of NaCl on ESPT‐Mediated FRET in a CTAC Micelle: A Femtosecond and FCS Study

Effect of NaCl on ESPT‐Mediated FRET in a CTAC Micelle: A Femtosecond and FCS Study

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

Oriented Coimmobilization of Oxidase and Catalase on Tailor-Made Ordered Mesoporous Silica

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