Silica SBA-15 Research Articles

Effect of various culinary treatments on the glycoalkaloid content of potato peel

Potatoes are one of the most consumed foods worldwide. During germination, glycoalkaloids (GAs) with potential bioactive properties are produced, which, at high concentrations, may have adverse health effects. Potato peels, a byproduct generated in large quantities but increasingly used in contemporary cuisine, contain significant levels of these GAs. This paper examines GA levels in potato peels after various culinary treatments (boiling, steaming, baking, air frying, conventional deep frying, and double frying) to provide new data and ensure food safety. An optimized extraction method using ultrasound-assisted extraction (UAE) was employed, followed by purification with mesostructured SBA-15 silica functionalized with octadecylsilane (C18) chains as sorbent in solid-phase extraction, prior to HPLC-DAD determination of α-solanine and α-chaconine levels in the samples. The method was validated, obtaining excellent recovery values (88 – 96 %) and low detection and quantification limits (0.3 and 1 mg/L, respectively). Upon application of the validated analytical method to the samples culinarily treated using the most common cooking techniques (boiling, steaming, baking, air frying, conventional deep frying, and double frying) at various times and temperatures, the obtained results demonstrated significant reductions (between 52 % and 84 %) in GAs content in the treated potato peels, compared to fresh samples. Statically significant degradation of these compounds was observed through baking at elevated times and temperatures (74 – 84 %), as well as both conventional deep frying and double frying (76 – 83 %).

Enhanced selective extraction of biogenic amines using carboxyl-functionalized SBA-15 and SBA-16 mesoporous silica

Enhanced selective extraction of biogenic amines using carboxyl-functionalized SBA-15 and SBA-16 mesoporous silica

Optimization of surface silanol groups in mesoporous SBA-15 and KIT-6 materials: Effects on APTES functionalization and CO2 adsorption

Hybrid mesoporous silicas are potentially reusable promising adsorbents for CO2 capture. Here SBA-15 and KIT-6 mesoporous silicas were synthetized by the sol-gel technique using a lower calcination temperature than the conventional one: 300 °C vs. 550 °C. This strategy aimed to maximize the surface hydroxyl group density and consequently, to improve functionalizing agent-loading performed by the post-synthesis grafting method. The as-obtained silica-based samples were then characterized and applied to CO2 capture. A correlation between chemical-textural properties and adsorption capacities of pure and modified materials was discussed. The calcined at 300 °C silica supports, SBA-15-300-1 and KIT-6-300-1, with high silanol group densities showed better adsorption capacities overall pressure range. It is worth highlighting that the KIT-6-300-1: APTES adsorbent had a good stability performance, showing a drop of around 8 % over the aging time of a year. While, the SBA-15-300-1: APTES solid presented an excellent recycled performance after 10 adsorption-desorption cycles, maintaining about 95 % of its initial capacity.

Cu-trimesate and mesoporous silica composite as adsorbent showing enhanced CO2/CH4 and CO2/N2 selectivity for biogas and flue gas separation

Due to their diverse structure, high porosity, and tunable functionality, Metal-Organic Frameworks (MOFs) hold great potential as materials for diverse applications, including gas separation. Material science researchers are focusing on creating flexible materials that have special properties. Most of the latest research mainly concentrates on fabricating composite materials of MOFs and other functional materials. These MOF-based composites can mitigate the limitations of pure MOFs and may even perform better than the individual components. Here, we present a systematic study on the effect of solvent in synthesising a composite (Cu-BTC@SBA-15) of Cu-trimesate MOF (aka CuBTC) and ordered mesoporous silica SBA-15, showing considerable improvement in selectivity for CO2 adsorption from the flue gas and biogas. The pristine Cu-BTC, SBA-15 and the composites with different content of Cu-BTC were characterized by PXRD, BET, FT-IR, SEM, TEM and TGA techniques. The pure gas adsorption isotherms were measured for CO2, CH4, and N2 gases. Ideal Adsorbed Solution Theory (IAST) is used for the binary selectivity calculations for gas systems such as CO2/CH4 and CO2/N2 in the context of biogas and flue gas separation. The composite exhibited an increase in CO2/CH4 selectivity by 39 % compared to pure Cu-BTC and 85 % compared to pure SBA-15. For the CO2/N2 system, the composite showed 38 % higher selectivity than Cu-BTC. The work has significance in the design of effective MOF-based composites for CO2 separation. Our work might open up a new route to design multifunctional materials for worldwide applications through an adsorptive and or mixed matrix membrane route.

Myricetin-loaded SBA-15 silica nanoparticles for enhanced management of pyrexia, pain, and inflammation through modulation of MAPK/NF-κB and COX-2/PGE-2 pathways: Evidence from the biochemical, histological, and metabolomic analysis

Myricetin (MYR) is a natural flavonoid that has several biological functions. However, some of its beneficial effects are diminished due to low water solubility, stability, and bioavailability. Herein, several kinds of silica nanoparticles (MCM-41 and SBA-15) were loaded with MYR to improve its biological activity as an analgesic, antipyretic, and anti-inflammatory component, thereby overcoming its drawbacks. The nanoparticles (MYR@SBA-15) were formulated optimally, transforming MYR into an amorphous state. This transformation was confirmed via several strategies, including differential scanning calorimetry, Fourier transform infrared spectroscopy, and powder x-ray diffraction. As a result, there was a significant enhancement in the solubility and rate of dissolution in water. The anti-inflammatory benefits as an innovative strategy and the underlying mechanism of action of MYR and its SBA-15 silica nanoparticles (MYR@SBA-15) were investigated based on the biochemical, histological, immunohistochemical, and metabolomic assays alongside their antipyretic and analgesic characteristics. Compared to the usage of raw MYR, the administration of MYR@SBA-15 at doses of 25, 50, and 100 mg/kg significantly decreases pain perception by inhibiting the body’s writhing motions induced by acetic acid. Furthermore, it helps regulate increased body temperature caused by baking yeast and effectively stabilizes it. It reduces the release of NO and PGE-2 in a concentration-dependent manner by down-regulating iNOS and COX-2 expression in the inflammatory model. MYR and MYR@SBA-15 also inhibit the nuclear translocation of NF-κB, downregulate the expression of mitogen-activated protein kinases (MAPKs), such as p38, ERK1/2, and JNK protein, and reduce the generation of proinflammatory cytokines, such as TNF-α. In addition, inflammatory cardinal signs like paw edema caused by carrageenan in rats are greatly suppressed by MYR and MYR@SBA-15 treatment when compared to the untreated group. More noteworthy outcomes are shown in the MYR@SBA-15, particularly at a dose of 100 mg/kg. These results of biochemical and immuno-histochemistry suggest that MYR@SBA-15 may be a useful analgesic antipyretic and may also help reduce inflammation by altering MAPKs/NF-κB and COX-2/PGE-2 signaling cascades. Serum metabolomics study demonstrated modifications in various low molecular weight metabolites with arthritis development. These metabolite levels were restored to normal when MYR@SBA-15 was administered via modulating several metabolic pathways, i.e., pyrimidine, energy metabolism, and proteins. Overall, MYR-loaded SBA-15 silica nanoparticles have demonstrated significant promise in enhancing the disturbed metaboloic pathways and providing a substantial capacity to regulate several oxidative stress and inflammatory mediators.

A novel strategy to produce spherical SBA-15 by polymeric macrospheres as a template for drug delivery

AbstractMesoporous silica SBA-15 has been a material widely studied for drug delivery due to its high biocompatibility and chemical stability, its ordered mesoporous cavities allow drug loading. However, it has a non-spherical particle shape, making it difficult to use in solid dosage forms, where spherical particles are preferred for better flow and distribution. In this regard, this study presented a novel strategy to produce spheric SBA-15 using polymeric macrospheres of a pharmaceutical grade acidic-resistant copolymer (Eudragit®S) stabilized with Pluronic® 123, as a template. The macrospheres of Eudragit®S were fabricated using the double emulsion (W1/O/W2) solvent-diffusion technique and then were used as a template to synthesize macrospheres of SBA-15 following acidic hydrolysis. The physicochemical analysis revealed that the SBA-15 has a spherical morphology (SEM) with pores arranged in a hexagonal lattice (TEM). The XRD showed signals at 0.71, 0.88 y 2.03 °2θ, that were indexed at the Miller indices (100), (110), (200). Nitrogen adsorption-desorption isotherms (type IV, H3) demonstrated mesoporous characteristics with a pore size of 9.3 nm, a wall thickness of 3 nm, a pore volume of 0.7538 cm³g−1, and a surface area of 640 m²g−1. These SBA-15 macrospheres also showed a zero-order release of ibuprofen. The SBA-15 formation using Eudragit®S macrospheres suggests that P123 on the macrosphere acts as a spherical core, as shown by FT-IR analysis. The acid-resistant copolymer maintained macrosphere integrity, enabling the assembly of the SBA-15 mesostructure in a 24-hour manufacturing time under acidic conditions.

Recombinant Esterase (BaCEm) Immobilized on Polyethyleneimine-Impregnated Mesoporous Silica SBA-15 Exhibits Outstanding Catalytic Performance.

A recombinant esterase, BaCEm, derived from Bacillus aryabhattai and heterologously expressed in Escherichia coli, was successfully immobilized on polyethyleneimine-impregnated mesoporous silica SBA-15. This immobilization utilized glutaraldehyde as a crosslinker. Optimal conditions were established with a PEI/SBA-15 ratio of 25% (w/w), a pH of 7.5, and a glutaraldehyde concentration of 0.5% (w/w), resulting in a loading capacity of 76.4mg/g, a recovery activity of 43.5%, and a specific activity of 7917 U/g for BaCEm. The immobilized BaCEm demonstrated high enantioselectivity, with an "E" value of 203.92, in the resolution assay of (R,S)-ethyl indoline-2-carboxylate. Notably, the immobilized enzyme, compared to its free counterpart, exhibited enhanced thermostability, maintaining 95.4% of its activity after 3h at 30°C. It also showed significant tolerance to organic solvents, retaining 48.4% and 28.7% residual activity in 10% v/v acetonitrile and acetone, respectively. Moreover, its storage stability was confirmed, with 68.5% residual activity preserved after 30days at 4°C. Remarkably, the immobilized BaCEm retained 58.1% of its activity after 10 reuse cycles, underscoring the potential of polyethyleneimine-impregnated mesoporous silica SBA-15 as an effective support for enzyme immobilization, promising for industrial applications.

Shedding reduction and immunity modulation in piglets with an inactivated Mycoplasma hyopneumoniae vaccine encapsulated in nanostructured SBA-15 silica

Mycoplasma (M.) hyopneumoniae is a primary etiological agent of porcine enzootic pneumonia (PEP), a disease that causes significant economic losses to pig farming worldwide. Current commercial M. hyopneumoniae vaccines induce partial protection, decline in preventing transmission of this pathogen or inducing complete immunity, evidencing the need for improving vaccines against PEP. In our study, we aimed to test the effectiveness of the SBA-15 ordered mesoporous silica nanostructured particles as an immune adjuvant of a vaccine composed of M. hyopneumoniae strain 232 proteins encapsulated in SBA-15 and administered by intramuscular route in piglets to evaluate the immune responses and immune-protection against challenge. Forty-eight 24-day-old M. hyopneumoniae-free piglets were divided into four experimental groups with different protocols, encompassing a commercial vaccine against M. hyopneumoniae, SBA-15 vaccine, SBA-15 adjuvant without antigens and a non-immunized group. All piglets were challenged with the virulent strain 232 of M. hyopneumoniae. Piglets that received the SBA-15 and commercial vaccine presented marked immune responses characterized by anti-M. hyopneumoniae IgA and IgG antibodies in serum, anti-M. hyopneumoniae IgA antibodies in nasal mucosa and showed an upregulation of IL-17 and IL-4 cytokines and downregulation of IFN-γ in lungs 35 days post-infection. Piglets immunized with SBA-15 vaccine presented a reduction of bacterial shedding compared to piglets immunized with a commercial bacterin. In addition, piglets from SBA-15 adjuvant suspension group presented increased IL-17 gene expression in the lungs without involvement of Th1 and Th2 responses after challenge. These results indicated that SBA-15 vaccine induced both humoral and cell-mediated responses in the upper respiratory tract and lungs, first site of replication and provided protection against M. hyopneumoniae infection with a homologous strain with reduction of lung lesions and bacterial shedding. Finally, these results enhance the potential use of new technologies such as nanostructured particles applied in vaccines for the pig farming industry.

Probing the Distribution and Mobility of Aminopolymers after Multiple Sorption-Regeneration Cycles: Neutron Scattering Studies.

Solid-supported amines are effective CO2 adsorbents capable of capturing CO2 from flue gas streams (10-15 vol % CO2) and from ultradilute streams, such as ambient air (∼400 ppm CO2). Amine sorbents have demonstrated promising performance (e.g., high CO2 uptake and uptake rates) with stable characteristics under repeated, idealized thermal swing conditions, enabling multicycle application. Literature studies suggest that solid-supported amines such as PEI/SBA-15 generally exhibit slowly reducing CO2 uptake rates or capacities over repeated thermal swing capture-regeneration cycles under simulated DAC conditions. While there are experimental reports describing changes in supported amine mass, degradation of amine sites, and changes in support structures over cycling, there is limited knowledge about the structure and mobility of the amine domains in the support pores over extended use. Furthermore, little is known about the effects of H2O on cyclic applications of PEI/SBA-15 despite the inevitable presence of H2O in ambient air. Here, we present a series of neutron scattering studies exploring the distribution and mobility of PEI in mesoporous silica SBA-15 as a function of thermal cycling and cyclic conditions. Small-angle neutron scattering (SANS) and quasielastic neutron scattering (QENS) are used to study the amine and H2O distributions and amine mobility, respectively. Applying repeated thermal swings under dry conditions leads to the thorough removal of water from the sorbent, causing thinner and more rigid wall-coating PEI layers that eventually lead to slower CO2 uptake rates. On the other hand, wet cyclic conditions led to the sorption of atmospheric water at the wall-PEI interfaces. When PEI remains hydrated, the amine distribution (i.e., wall-coating PEI layer thickness) is retained over cycling, while lubrication effects of water yield improved PEI mobility, in turn leading to faster CO2 uptake rates.

CO2 Adsorption by CMK-3 at Low Temperatures and High Pressure to Reduce the Greenhouse Effect.

In this study, the maximum CO2 capture capacity of an ordered mesoporous carbon (CMK-3) was evaluated at high pressure (35 atm) and several temperatures (0, 10, 20, and 35 °C). CMK-3 was synthesized with the hard template method (silica SBA-15) using furfuryl alcohol and toluene as carbon sources. The CO2 adsorption isotherms were fitted to the following adsorption theories: Freundlich, Langmuir, Sips, Toth, Dubinin-Radushkevich, and Temkin. The maximum capture capacity (726.7 mg·g-1) was achieved at 0 °C and 34 atm. The results of the study of successive adsorption-desorption cycles showed that multi-cycle reversible gas capture processes could be used in optimal temperature and pressure conditions. It was determined that 0.478 g of CMK-3 would be required to reduce the CO2 concentration in 1 m3 of air to pre-industrial levels (280 ppm). The obtained results may contribute to technological developments for the mitigation of human impacts on the environment through the capture of atmospheric CO2.

Advancing Adsorption and Separation with Modified SBA-15: A Comprehensive Review and Future Perspectives.

Mesoporous silica SBA-15 has emerged as a promising adsorbent and separation material due to its unique structural and physicochemical properties. To further enhance its performance, various surface modification strategies, including metal oxide and noble metal incorporation for improved catalytic activity and stability, organic functionalization with amino and thiol groups for enhanced adsorption capacity and selectivity, and inorganic-organic composite modification for synergistic effects, have been extensively explored. This review provides a comprehensive overview of the recent advances in the surface modification of SBA-15 for adsorption and separation applications. The synthesis methods, structural properties, and advantages of SBA-15 are discussed, followed by a detailed analysis of the different modification strategies and their structure-performance relationships. The adsorption and separation performance of functionalized SBA-15 materials in the removal of organic pollutants, heavy metal ions, gases, and biomolecules, as well as in chromatographic and solid-liquid separation, is critically evaluated. Despite the significant progress, challenges and opportunities for future research are identified, including the development of low-cost and sustainable synthesis routes, rational design of SBA-15-based materials with tailored properties, and integration into practical applications. This review aims to guide future research efforts in developing advanced SBA-15-based materials for sustainable environmental and industrial applications, with an emphasis on green and scalable modification strategies.

Synthesis and characterization of SBA-15 silica containing cyclam inside pores for capturing iron chloride: Analysis of interactions between ferrous chloride and cyclam in a system with strongly dispersed functional groups on the SiO2 surface

The use of the spatial structure of mesoporous silica combined with organic molecules opens up a wide range of possibilities in the field of separation of single atoms and the precise creation of their environment. Materials obtained in this way can find applications as single-atom catalysts (SAC) and in environmental applications in ion and molecule trapping processes. An example of such a material is silica of the SBA-15 type functionalized with cyclam (1,4,8,11-tetraazacyclotetradecane) anchored inside the pores with propyl chains. In this work, we present such a material containing 5% functional groups, additionally activated with iron(II) chloride, which was chelated by cyclam anchored inside the pores of silica. The presented nanocomposite has been thoroughly tested for its assumed molecular structure and stability. We compared it to a material containing only cyclam. The obtained results showed the high efficiency of the silica matrix with cyclam in the separation of single FeCl2 molecules and the correct molecular structure of the obtained material. The nanocomposite containing chelated molecules with iron showed good stability, while the structure of the material with cyclam alone collapsed with time.

Effective amine solvent regeneration over NiO-modified SBA-15 catalysts for energy-saving CO2 capture

Catalytic amine regeneration can decrease the energy required for regeneration; therefore, high economic and energy efficiency can be expected for CO2 capture. These factors necessitate the development of an inexpensive and easily synthesizable catalyst that can exhibit a high desorption efficiency. When selecting a catalyst, its physicochemical properties must be considered, because they markedly affect the chemical reaction between CO2–amine–catalyst. In this study, mesoporous silica SBA-15, particularly, rod-type SBA-15, wrinkled SBA-15 (modified from rod-type SBA-15), and NiO-impregnated rod-type and wrinkled SBA-15 catalysts were investigated in terms of the CO2 desorption rate and heat duty in a CO2–rich 5 M monoethanolamine (MEA) solution at 86 ℃. The physicochemical properties of the catalysts were compared to investigate their effect on the CO2 desorption efficiency. The performance of wrinkled SBA-15 impregnated with 10 wt% NiO in a CO2–rich MEA solution was optimal, exhibiting a 12 % higher CO2 desorption rate and 19.9 % lower heat duty than the MEA solution without a catalyst. Furthermore, the stability and reproducibility of the catalysts were confirmed through repeated experiments under identical conditions. Based on the experimental results and analysis, a plausible desorption mechanism for CO2–MEA–catalyst was proposed. It is expected that the regeneration heat duty during the CO2 regeneration can be effectively reduced by a catalyst, eventually applied to the CO2 capture.

Synthesis of TiO2/SBA-15 Nanocomposites by Hydrolysis of Organometallic Ti Precursors for Photocatalytic NO Abatement

The development of advanced photocatalysts for air pollution removal is essential to improve indoor air quality. TiO2/mesoporous silica SBA-15 nanocomposites were synthesized using an organometallic decoration method, which leverages the high reactivity of Ti precursors to be hydrolyzed on the surface water groups of silica supports. Both lab-made Ti(III) amidinate and commercial Ti(IV) amino precursors were utilized to react with water-rich SBA-15, obtained through a hydration process. The hydrated SBA-15 and the TiO2/SBA-15 nanocomposites were characterized using TGA, FTIR, 1H and 29Si NMR, TEM, SEM, N2 physisorption, XRD, and WAXS. This one-step TiO2 decoration method achieved a loading of up to 51.5 wt.% of approximately 9 nm anatase particles on the SBA-15 surface. This structuring provided excellent accessibility of TiO2 particles for photocatalytic applications under pollutant gas and UV-A light exposure. The combination with the high specific surface area of SBA-15 resulted in the efficient degradation of 400 ppb of NO pollutant gas. Due to synergistic effects, the best nanocomposite in this study demonstrated a NO abatement performance of 4.0% per used mg of TiO2, which is 40% more efficient than the reference photocatalytic material TiO2 P-25.

Synthesis of Composite Sorbents with Chitosan and Varied Silica Phases for the Adsorption of Anionic Dyes.

In this work, various types of silica materials were used for the synthesis of chitosan-silica composites. The composites were obtained using the chitosan (Ch) immobilization process from an aqueous solution on various silica phases, i.e., amorphous diatomite (ChAD), crystalline diatomite (ChCD), mesoporous silica MCM-41 (ChMCM), and mesoporous silica SBA-15 (ChSBA). Textural, structural, morphological, and surface properties of the materials were determined by using various measurement techniques, i.e., low-temperature adsorption/desorption isotherms of nitrogen, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), potentiometric titration, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The adsorption properties towards various anionic dyes, i.e., acid red 88 (AR88), acid orange 8 (AO8), and orange G (OG), were evaluated based on kinetic and equilibrium measurements. The ChSBA, ChAD, and ChMCM composites were characterized by relatively high adsorption capacities (am) for AR88, with values equal to 0.78, 0.71, and 0.69 mmol/g, respectively. These composites were also distinguished by the rapid AR88 adsorption rate, with the values of half-time parameter t0.5 equal to 0.35, 2.84, and 1.53 min, respectively. The adsorption equilibrium and kinetic data were analyzed by applying the generalized Langmuir isotherm and the multi-exponential equation (m-exp), respectively. An interaction mechanism between the dyes and the obtained materials was proposed.

Impact of nanoconfinement on the physical state and conductivity mechanisms of a 2-picolinium ionic liquid crystal

Hybrid solid-like materials prepared from the incorporation of liquid-like ionic conductors into nanoporous matrices could represent an advantage for a variety of electronic applications. Aiming to obtain such materials, three composites of the polymorphic ionic liquid crystal (ILC) 1-hexadecyl-2-methylpyridinium bromide ([C16-2-Pic][Br]), loaded in the mesoporous inorganic silica SBA-15 (∼6.8 nm in pore diameter), were prepared at guest–host weight fractions of ∼ 40, 60 and 80% (w/w) and investigated by different techniques: ATR-FTIR, BET, TGA, XRD and DSC. Complete amorphisation was achieved for the 40 and 60% composites, while the 80% preparation was stabilised in the low-T morph of native C16, being in the liquid state at room temperature. Furthermore, through Dielectric Relaxation Spectroscopy, the ionic conductivity of the three hybrid materials was characterised, allowing to deconvolute this property in a pure ohmic contribution (conductivity I) and the overlapping of ac − dc transition with interfacial polarisation resulting from the coexistence of the ionic liquid and the quasi-insulating inorganic matrix (conductivity II). From –20 to 20 °C, the conductivity and the corresponding charge migration are faster in all composites relative to the neat ILC, as deduced from the inferior radii of Nyquist arcs. The 60% preparation stood out from the other materials, exhibiting direct conductivity unaffected by electrode polarisation over a larger T-range, leading to the assumption of a nearly continuous silica-mediated charge migration pathway, which is never reached for the 40% composite, while, in the 80% preparation, some C16 deposits on the outer surface of the pores. Incorporation into the silica matrix proved to be a good strategy for the production of cost-efficient materials with long-term stabilisation of the ionic liquid in a single phase over a large range of temperatures, enabling the prediction of flow and conductive properties.

Carboxyl-functionalized mesoporous silica-coated solid-phase microextraction Arrow for the determination of six biogenic amines in animal-derived meat

Mesoporous silica materials, SBA-15 and SBA-16, that functionalized with the carboxyl, vinyl and amino groups were synthesized in this study. The spectroscopic analysis evaluated the physicochemical characteristics of these materials. These materials were coated on the arrow-typed solid phase microextraction (SPME Arrow) to extract biogenic amines (BAs). The influences of these materials' functional groups and spatial structure on their extraction efficiency were studied. Carboxyl group modified SBA-15 (SBA-15-C) exhibited the highest extraction capacity to BAs because of the size exclusion effect and the electrostatic interaction. The extraction and desorption parameters of the SPME Arrow method were optimized. The SBA-15-C-SPME Arrow was coupled with a gas chromatography-mass spectrometry (GC-MS) system for the determination of BAs in animal-derived meat samples, which showed good repeatability (RSD<15%), satisfactory linear range (0.01–1 mg kg–1), low limit of detection (0.001–0.004 mg kg–1), and high recovery (84–129%). This method showed excellent applicability for the quantitative and qualitative detection of six BAs in animal-derived meat samples. This study provides new insight into the development of new sorbents with high extraction capacity to BAs for the selective and sensitive determination of BAs in complex meat samples.

Functionalized corn stalk carboxymethyl cellulose and mesoporous silica SBA-15 composite hydrogel-immobilized lipase for the resolution of racemic ibuprofen ethyl ester

ABSTRACT The immobilization of enzymes is an important strategy to improve their stability and reusability. However, it often comes with a trade off of reduced biological activity and catalytic efficiency. In this study, a composite hydrogel based on corn stalk carboxymethyl cellulose, acrylic acid, and mesoporous silica SBA-15 was developed as a support for the immobilization of lipase from Pseudomonas S.P. (PSL). The surface morphology and functional properties of the composite hydrogels were investigated by scanning electron microscopy, Fourier transform infrared, X-ray diffraction and simultaneous thermal analyzer, respectively. The composite hydrogel materials had a large number of mesopores and macropores were present in the wall of the hydrogel sheet. The hydrogel had a network structure that reduced the diffusion resistance of the substrate and improved the accessibility of the enzyme. The immobilized PSL exhibited high enantioselectivity (E value: 88.2) and enzyme activity (316.8 µmol/g/min) in the preparation of (S)-ibuprofen by enzymatic hydrolytic resolution of racemic ibuprofen ethyl ester. This prepared novel composite hydrogel is a promising supporting matrix for the immobilization of enzymes.

Composites of Poly(3-hydroxybutyrate) and Mesoporous SBA-15 Silica: Crystalline Characteristics, Confinement and Final Properties.

Several composites based on poly(3-hydroxybutyrate) (PHB) and mesoporous SBA-15 silica were prepared by solvent-casting followed by a further stage of compression molding. The thermal stability, phase transitions and crystalline details of these composites were studied, paying special attention to the confinement of the PHB polymeric chains into the mesopores of the silica. For that, differential scanning calorimetry (DSC) and real-time variable-temperature X-ray scattering at small angles (SAXS) were performed. Confinement was stated first by the existence of a small endotherm at temperatures around 20 °C below the main melting or crystallization peak, being later confirmed by a notable discontinuity in the intensity of the main (100) diffraction from the mesoporous silica observed through SAXS experiments, which is related to the change in the scattering contrast before and after the crystallization or melting of the polymer chains. Furthermore, the usual α modification of PHB was developed in all samples. Finally, a preliminary investigation of mechanical and relaxation parameters was carried out through dynamic-mechanical thermal analysis (DMTA). The results show, in the temperature interval analyzed, two relaxations, named α and β (the latest related to the glass transition) in order of decreasing temperatures, in all specimens. The role of silica as a filler is mainly observed at temperatures higher than the glass transition. In such cases, stiffness is dependent on SBA-15 content.

N-coordinated Ag sites on ordered mesoporous carbons for highly efficient electrolytic production of H2O2 in acidic electrolyte

N-coordinated Ag (Ag-Nx) sites embedded in ordered mesoporous carbon (Ag-Nx/C) were prepared by pyrolyzation of Ag-2, 2-bipyridine complexes in the confined channels of mesoporous SBA-15 silica. This nanocasting method allowed high dispersion state of Ag-Nx sites on carbons with ordered mesoporous channels and higher specific surface area. Ag-Nx/C was found to be very active electrocatalyst for two-electron oxygen reduction reaction (2e- ORR) in 0.1 M HClO4 acidic electrolyte. The bulk electrolytic production for hydrogen peroxides (H2O2) could be achieved with a high production rate of 1.67 mol h−1 gcat−1 together with high electrolysis Faraday efficiency of about 93%. Ag-Nx/C also revealed better acid-resistant durability during H2O2 electrolysis production. This work provided an efficient and durable Ag-Nx/C electrocatalyst for electrolytic H2O2 production in acids.