Type Mesoporous Silica Research Articles

Predictive modeling and simulation of wastewater treatment process using nano-based materials: Effect of pH and adsorbent dosage

A machine learning simulation via artificial neural network was implemented in this work to analyse adsorption removal of cadmium ions from aqueous solutions. The considered solid adsorbent in this work was a nanocomposite of mesoporous silica type and a polymer. To separate ions from water the mesoporous nanocomposite was selected due to its large pores. The simulation runs were carried out to correlate the adsorption parameters including solution pH and adsorbent dosage to the equilibrium concentration of ions in the liquid phase. The training and validation of the neural network indicated agreement with the experimental data for adsorption of cadmium ions, with high accuracy. The statistical evaluation of the data indicated great accuracy with R2 greater than 0.999 for the fitting. The findings of the modelling indicated that the effect of adsorbent dosage is not significant compared to the solution’s pH. The adsorption removal was increased with enhancing the solution pH due to the interaction between the ions and the surface of adsorbent. The results revealed that the developed neural network simulation is robust for prediction of ions removal from water using nanocomposite adsorbents.

Enhancement of thermal and mechanical properties of PMMA composites by incorporating mesoporous micro-silica and GO

The application of polymer-based composite materials is on the rise due to their enhanced thermal and mechanical properties compared to polymers themselves. For the first time in this study, the combination of graphene oxide (GO) and mesoporous micro-silica particles (with varying pore sizes) was used as fillers into PMMA matrices via in-situ bulk polymerization with ultrasonication. Two types of mesoporous silica were used at a fixed amount of 3 wt% with varying GO composition from 0.1 wt% to 1.2% to investigate the synergistic effect of GO and silica and increment of pore size of silica filler on the thermomechanical properties of the composites. The glass transition temperature Tg, thermal stability (the temperature at 10% and 60% weight loss) Td10 and Td60 of the same composite were increased by 21.5 °C, 46.5 °C, and 32.3 °C, respectively, compared to that of neat PMMA. Its tensile strength was increased remarkably by 329% compared with the PMMA. This work offers the possibility of further enhancement of thermal and mechanical properties of polymer-based composites by incorporating more than one filler with diverse properties.

Functionalization of SBA-15 mesoporous silica with bis-schiff base for the selective removal of Pb(II) from water

The SBA-15 type mesoporous silica functionalized by the bis-Schiff base was designed and prepared through three surface modification steps. The obtained nanohybrid, MS-AP, was systematically characterized by a series of analytical techniques, and these thereby confirmed that the bis-Schiff ligand was successfully immobilized and the hexagonal pore structure of SBA-15 was well kept after the modification. Once modified, adsorption tests for Pb(II) were carried out in a bath under various conditions. Kinetic analyses demonstrated that adsorption kinetic was better represented by the pseudo-second-order model and besides this, the adsorption isotherms were well-fitted to the Freundlich model. Under optimal conditions, the theoretical maximum amount of Pb(II) that could be adsorbed by the MS-AP was measured to be 151.5 ​mg ​g−1, which suggested an excellent ions removal performance by the adsorbent. The thermodynamic study confirmed the spontaneous and endothermic nature of Pb(II) sorption with enhanced randomness. In the binary or the multiple mixed ions solutions, the MS-AP exhibited enhanced selectivity for Pb(II) with respect to Cu(II), Cd(II), Mn(II), Mg(II), Co(II) and Ni(II), when compared with the commonly used amine-grafted SBA-15. Furthermore, the ionic strength of the solution had no significant inhibition effect on Pb(II) sorption. Considering the good regeneration ability and reusability of the adsorbent, MS-AP could be promising for the selective removal of Pb(II) from water.

A comparison of Structure–Activity of Cu-Modified Over Different Mesoporous Silica Supports for Catalytic Conversion of Levulinic Acid

Catalytic hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was investigated over four different types of mesoporous silica (SBA-15, MCM-48, MCM-41, and KIT-6) supported copper (5 wt.%) catalysts. The Cu was incorporated into mesoporous silica supports by a sequential impregnation method. A detailed investigation of the support structure–activity correlation and the performance of the catalysts in LA conversion was studied. Detailed characterisation techniques were used to evaluate the physical and catalytic properties of the studied catalysts. The structure type and physicochemical properties of the silica support had a significant effect on the overall performance of the catalysts. Among them, over Cu/SBA-15 catalyst, a complete levulinic acid (LA) conversion with ~ 98% gamma valerolactone (GVL) selectivity was achieved at 265 °C under ambient H2 pressure. The superior performance of Cu/SBA-15 catalyst was attributed to the high surface acidity, reducibility of Cu oxides species, and highly dispersed Cu particles over SBA-15 structure. The results confirmed that the activity of the catalysts is significantly influenced by the textural properties, surface acidity and copper dispersion. Durability of all the catalysts were also tested for 50 h time on stream and over SBA-15 catalyst, only a small drop in the activity was observed.

Preparation of SBA-15 mesoporous silica grafted with bis-salicylaldehyde Schiff base for uptake of Pb(II) and Cu(II) from water

SBA-15 type mesoporous silica modified with bis-salicylaldehyde Schiff base (SBA-DSA) was developed for the Pb(II) and Cu(II) ions removal from water. The adsorption properties of SBA-DSA were also compared with SBA-15 decorated with mono-Schiff base (SBA-SA). Sorption of Pb(II) and Cu(II) on SBA-DSA and SBA-SA was pH-dependent and the optimum pH for adsorption was selected at pH 5.0. The pseudo-second-order kinetic model described the sorption process well. Besides, adsorption isotherm data were better represented by the Langmuir model, confirming the adsorption processes occurred on the monolayer. Maximum adsorption capacities of SBA-DSA were 60.9 mg g−1 for Pb(II) and 36.6 mg g−1 for Cu(II), which were higher than adsorption performance of SBA-SA. The synthesized SBA- DSA showed excellent adsorption selectivity for Pb(II) in mixed metal ions solution. Considering the good reusability and regeneration of the adsorbent, SBA-DSA prepared here is promising for decontamination of water solutions from heavy metal ions.

Hydroamination of Phenylacetylene on Gold-Containing Catalytic Systems Supported on Substrates Modified with Ionic Liquids under Conditions of Microwave Activation

It is established that catalytic systems based on gold nanoparticles stabilized in ionic liquids and supported on an MCM-41–type mesoporous silica show a high activity and selectivity in hydroamination of phenylacetylene with aniline, obeying Markovnikov’s rule. It is shown that the activity of the synthesized gold-containing systems grows substantially under conditions of microwave activation, which also shortens the time required to achieve full conversion.

The nonlinear optical properties of silver nanoparticles decorated glass obtained from sintering mesoporous powders

ABSTRACTSilver nanoparticles (Ag NPs) have excellent third‐order nonlinear optical properties but it is still difficult to obtain silica glass containing Ag NPs with homogenous dispersion and small particle size. Herein, silica glass with homogenously distributed Ag NPs in its matrix was derived from sintering a famous type of mesoporous silica (FDU‐12) encapsulated with Ag NPs (Ag NPs/FDU‐12) through Spark Plasma Sintering (SPS) technique. Benefited from the low‐temperature sintering property of the Ag NPs/FDU‐12 powders (~930°C within 5 min), the Ag NPs can be directly trapped in the derived silica glass with small particle size (<3.0 nm) and without mass loss. The as‐prepared Ag NPs/glass showed a typical reverse saturable absorption curve, which is measured via the Z‐scan method by using a 532 nm nanosecond laser. The nonlinear coefficient and imaginary third‐order susceptibility were calculated as 11.46 cm/GW and 2.22 × 10−12 esu, respectively, indicating the excellent third‐order nonlinear optical properties of the Ag NPs/glass. This study demonstrates a great potential for preparing silica glasses functionalized with well dispersed ultrafine functional particles, which is appealing in photonic field.

Synthesis and characterization of ordered mesoporous silicas for the immobilization of formate dehydrogenase (FDH)

This work studied the influence of the pore size and morphology of the mesoporous silica as support for formate dehydrogenase (FDH), the first enzyme of a multi-enzymatic cascade system to produce methanol, which catalyzes the reduction of carbon dioxide to formic acid.Specifically, a set of mesoporous silicas was modified with glyoxyl groups to immobilize covalently the FDH obtained from Candida boidinii. Three types of mesoporous silicas with different textural properties were synthesized and used as supports: i) SBA-15 (DP = 4 nm); ii) MCF with 0.5 wt% mesitylene/pluronic ratio (DP = 20 nm) and iii) MCF with 0.75 wt% mesitylene/pluronic ratio (DP = 25 nm). As a whole, the immobilized FDH on MCF0.75 exhibited higher thermal stability than the free enzyme, with 75% of residual activity after 24 h at 50 °C. FDH/MCF0.5 exhibited the best immobilization yields: 69.4% of the enzyme supplied was covalently bound to the support. Interestingly, the specific activity increased as a function of the pore size of support and then the FDH/MCF0.75 exhibited the highest specific activity (namely, 1.05 IU/gMCF0.75) with an immobilization yield of 52.1%. Furthermore, it was noted that the immobilization yield and the specific activity of the FDH/MCF0.75 varied as a function of the supported enzyme: as the enzyme loading increased the immobilization yield decreased while the specific activity increased. Finally, the reuse test has been carried out, and a residual activity greater than 70% was found after 5 cycles of reaction.

Short-Term Oral Administration of Mesoporous Silica Nanoparticles Potentially Induced Colon Inflammation in Rats Through Alteration of Gut Microbiota.

PurposeMesoporous silica (MSNs) have attracted considerable attention for its application in the field of drug delivery and biomedicine due to its high surface area, large pore volume, and low toxicity. Recently, numerous studies revealed that gut microbiota is of critical relevance to host health. However, the toxicological studies of MSNs were mainly based on the degradation, biodistribution, and excretion in mammalian after oral administration for now. Here in this study, we explored the impacts of oral administration of three kinds of MSNs on gut microbiota in rats to assess its potential toxicity.MethodsForty rats were divided into four groups: control group; Mobil Composition of Matter No. 41 type mesoporous silica (MCM-41) group; Santa Barbara Amorphous-15 type mesoporous silica (SBA-15) group, and biodegradable dendritic center-radial mesoporous silica nanoparticle (DMSN) group. Fecal samples were collected 3 days and 7 days after the intake of MSNs and analyzed with high throughput sequencing. Gastric tissues in rats were obtained after dissection for the histological study.ResultsThree different MSNs (MCM-41, SBA-15, and DMSN) were successfully prepared in this study. The pore size of three MSNs was calculated similarly as (3.54 ± 0.15) nm, (3.48 ± 0.21) nm, and (3.45 ± 0.17) nm according to the BET & BJH model, respectively, while the particle size of MCM-41, SBA-15 and DMSN was around 209.2 nm, 1349.56 nm, and 244.4 nm, respectively. In the gene analysis of 16S rRNA, no significant changes in the diversity and richness were found between groups, while Verrucomicrobia decreased and Candidatus Saccharibacteria increased in MCM-41 treated groups. Meanwhile, no inflammatory and erosion symptoms were observed in the morphological analysis of the colons, except the MCM-41 treated group.ConclusionThree different MSNs, MCM-41, SBA-15, and DMSN were successfully prepared, and this study firstly suggested the impact of MSNs on the gut microbiota, and further revealing the potential pro-inflammatory effects of oral administration of MCM-41 was possibly through the changing of gut microbiota.

Synthesis, molecular dynamics simulation and adsorption study of different pollutants on functionalized mesosilica

Experimental and computational works were carried out on a new type of mesoporous silica. In the experimental section, functionalized hollow mesosilica spheres were prepared via a facile technique and then evaluated using some analytical techniques (FESEM, TEM, L-XRD, FTIR, BET-BJH, and TGA). The obtained results revealed that the synthesized material had hollow structure with a diamino-grafted porous shell. The molecular separation of crystal Violet (CV) and neutral Red (NR) dyes from water were investigated by adsorption process using the synthesized powder. Influence of adsorbent loading was evaluated as adsorption ability and dyes removal efficiency. Also, the obtained modeling results revealed appropriate fitting of data with non-linear Langmuir model. The theoretical studies were employed to study the adsorption and removal mechanism of cationic (CV and NR) and anionic (orange II (OII)) dyes using molecular dynamics calculations. Moreover, the simulation outcomes provided valuable information about quantum chemical properties including the HOMO–LUMO maps, chemical reactivity, global softness (σ) and hardness (η) for silica-linker-water-dyes components.

Direct synthesis of silver nanoparticles modified spherical mesoporous silica as efficient antibacterial materials

The development of new antimicrobial agents that can overcome antibiotic-resistance and possess improved antibacterial activity is of important global need. A one-step process is demonstrated to prepare silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles (AgMSN, average diameter ~ 200–500 nm) using a novel cationic surfactant that does not lead to precipitation of AgBr. The resulting nanostructure was characterized using powder X-ray diffraction, nitrogen physisorption and chemisorption analyses, electron microscopy techniques, and UV–vis spectroscopy. Together, these data demonstrated the silver nanoparticles were uniformly dispersed on the MSN. Gram-negative E. coli K12 and Gram-positive B. subtilis were used to study the antibacterial properties of these nanocomposites by both the plate count method and optical density measurements. In the antibacterial tests for E. coli K12 and B. subtilis , the AgMSN exhibited low minimum inhibitory concentrations of 85 μg mL −1 AgMSN (Ag content 6.1 μg mL −1 ) and 90 μg mL −1 (Ag content is 6.4 μg mL −1 ), respectively, revealing the high antibacterial activity. Additionally, >95% growth reduction in continuous re-culturing tests (6 cycles, 25 days) at minimum bactericidal concentration demonstrate excellent long-term antibacterial activity of AgMSN. The nanocomposites showed excellent antibacterial activity against both. These results demonstrate that AgMSN composites possess great potential as an antibacterial material. Silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles (AgMSN) have been synthesized by a one-step process which exhibits excellent long-term antibacterial activity against E. coli K12 and B. subtilis . • Silver nanoparticle decorated MCM–41 type mesoporous silica nanoparticles. • A one-step process of synthesis without using any reducing agent. • Excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. • Re-culturing test to prove long-term antibacterial property. • Study of antibacterial mechanism.

Study on the influence of technological factors on drug loading of poorly water-soluble drug on MCM-41 mesoporous carrier

The present study explored solvent impregnation drug loading process of the poorly soluble non-steroid anti-inflammatory drug indomethacin on MCM-41 type mesoporous silica carrier. Different technological factors that can influence drug-loading process as time of reaction, temperature, use of non-solvent as well as different ratios between drug and MCM-41 were studied. TEM and DLS were used to characterize physicochemical properties of obtained particles. The influence of drug-loading rate on dissolution process were studied using in-vitro release tests. Our results established that changes in explored technological factors could lead to different indomethacin loading. Moreover, the in-vitro release tests proved that drug loading rate had a direct influence on indomethacin release from MCM-41 particles. Our finding suggested that by tuning the main technological factors it would be possible different drug delivery systems with different drug loading rate to be obtained.

Mesoporous Silica-Supported Ionic Liquids as Catalysts for Styrene Carbonate Synthesis from CO2

Various types of mesoporous silica were used as carriers to synthesize a series of immobilized imidazolium-based ionic liquids. Their activity was tested in the synthesis of styrene carbonate from CO2 and styrene. This is one-pot process, whereby two stages are carried out in one reactor and there is no need to isolate the intermediate product, epoxide. A systematic study on the influence of parameters such as temperature, the reaction time, CO2 pressure, as well as the amount and type of catalyst used was carried out. A strong synergistic catalytic effect of ionic liquid and Lewis acid was observed in promoting this reaction. The addition sequence of regents and amount of immobilized catalyst were considered crucial for the synthesis of styrene carbonate from CO2 and styrene. The tested silica-supported ionic liquids gave an easily-recyclable system which under the most favorable conditions ([mtespim]Cl/@SiO2; ZnBr2, 0.1 mol%; 110 °C, 4 h, 1 MPa) can be reused without a significant loss of catalytic activity nor selectivity.

Highly CO2 selective mixed matrix membranes of polysulfone based on hetaryl modified SBA-16 particles

Mixed matrix membranes were prepared by incorporating pyrazole functionalized SBA-16 type mesoporous silica as filler in polysulfone (PSf) matrix. The structure, morphology, and porosity of functionalized filler were confirmed by Fourier transform infrared (FTIR) spectra, scanning electron microscope (SEM) images, 13C NMR spectra and N2 adsorption-desorption analysis. A good uniform interaction of filler with polymer matrix was observed for all membranes. The porosity of filler enhanced the CO2 gas diffusivity through the membrane leading to increased CO2 permeability of up to 14.43 Barrer (116% increase) at the highest filler loading of 30%. The presence of CO2-philic functional groups resulted in a simultaneous increase in both ideal and mixed gas CO2/N2 selectivity of 42.44 and 46.13 respectively (68.34% and 87.06% increase respectively), compared to non-functionalized filler).

Tumor-mesoporous silica nanoparticle interactions following intraperitoneal delivery for targeting peritoneal metastasis

The use of intraperitoneal administration of nanoparticles has been reported to facilitate higher concentrations of nanoparticles in metastatic peritoneal tumors. While this strategy is appealing for limiting systemic exposure of nanocarrier delivered toxic cargoes and increasing nanoparticle concentrations in avascular peritoneal tumors, little is known about the mechanism of nanoparticle accumulation on tumor tissues and currently, no nanoparticle-based product has been approved for intraperitoneal delivery. Here, we investigated the nanoparticle-specific characteristics that led to increased peritoneal tumor accumulation using MCM-41 type mesoporous silica nanoparticles as our model system. We also investigated the components of the peritoneal tumor stroma that facilitated nanoparticle-tumor interaction. The tumor extracellular matrix is the main factor driving these interactions, specifically the interaction of nanoparticles with collagen. Upon disruption of the collagen matrix, nanoparticle accumulation was reduced by 50%. It is also notable that the incorporation of targeting ligands did not increase overall tumor accumulation in vivo while it significantly increased nanoparticle accumulation in vitro. The use of other particle chemistries did not grossly affect the tumor targetability, but additional concerns arose when those tested particles exhibited significant systemic exposure. Mesoporous silica nanoparticles are advantageous for intraperitoneal administration for the treatment of peritoneal metastasis due to their physical stability, tumor targetability, strong interaction with the collagen matrix, and extended peritoneal residence time. Maximizing nanoparticle interaction with the tumor extracellular matrix is critical for developing strategies to deliver emerging therapeutics for peritoneal cancer treatment using nanocarriers.

Synthesis, Characterization and Use of Mesoporous Silicas of the Following Types SBA-1, SBA-2, HMM-1 and HMM-2.

Mesoporous silicas have enjoyed great interest among scientists practically from the moment of their discovery thanks to their unique attractive properties. Many types of mesoporous silicas have been described in literature, the most thoroughly MCM-41 and SBA-15 ones. The focus of this review are the methods of syntheses, characterization and use of mesoporous silicas from SBA (Santa Barbara Amorphous) and HMM (Hybrid Mesoporous Materials) groups. The first group is represented by (i) SBA-1 of three-dimensional cubic structure and Pmn symmetry and (ii) SBA-2 of three-dimensional combined hexagonal and cubic structures and P63/mmc symmetry. The HMM group is represented by (i) HMM-1 of two-dimensional hexagonal structure and p6mm symmetry and (ii) HMM-2 of three-dimensional structure and P63/mmc symmetry. The paper provides comprehensive information on the above-mentioned silica materials available so far, also including the data for the silicas modified with metal ions or/and organic functional groups and examples of the materials applications.

Protein adsorption on spark plasma sintered 2d-, 3d- and lamellar type mesoporous silicate compacts.

The preparation of lamellar type mesoporous silica (MPS) compact through the spark plasma sintering (SPS) and the adsorption/desorption of protein onto MPS compact are reported to be compared with those onto 2d‐hexagonal and 3d‐cubic type MPS compacts. A lamellar‐type MPS powder (MPS‐la) was prepared using triblock copolymer, PEO5 PPO68 PEO5, and was compacted in a carbon die and heated at 500°C for 5 min under uniaxial pressure. The products are referred to as MPS‐la‐500. The MPS compacts keep the lamellar type mesoporous configuration. The adsorbed amount of protein onto MPS‐la‐500 was 100 mg/g, while that on MPS‐la was 130 mg/g, and the former decreased by 23%. However, its decreasing ratio of the protein adsorption on MPS‐la‐500 was less than those of 2d‐hexagonal and 3d‐cubic type MPS compacts, which were 73 and 34%, respectively. The released amount of protein into PBS solution from MPS‐la‐500, which was soaked in the protein solution for 48 h, increased with the soaking time, while those from 2d‐ and 3d‐type MPS compacts reached to plateau for 4 h of soaking. The lamellar type MPS compact was found to be easier to absorb and release proteins, which may be due to the large aperture of the mesoporous configuration.

Functional Mesoporous Silica Nanomaterials for Catalysis and Environmental Applications

Abstract Silica materials are used in a wide range of applications such as catalysis, photocatalysis, CO2 capture, and environmental remediation. These nanomaterials (NMs) have been extensively investigated since the advent of Stöber silica. However, the absence of pores and small surface area of Stöber silica limits its applications. Later, the discovery of MCM-41 type mesoporous silica using surfactants as structural directing agents became revolutionary in the field of silica NMs. This review focuses on the methods used for synthesizing mesoporous silica nanomaterials (NMs), especially mesoporous nanoparticles (NPs), and their applications in various fields including catalysis (i.e., support for nanoparticle catalysts) and environmental remediation (CO to CO2 conversion, volatile organic compound (VOC) removal, and CO2 capture). The current issues/challenges in realizing the practical applications of these conventional materials are also highlighted. This review also compares the characteristics and applications of MCM-41, SBA-15, and KCC-1 to demonstrate the effect of the morphology and pore architecture of silica on the properties of silica-based NMs. The scope for future developments in the synthesis and applications of silica materials with different pore sizes and morphologies is discussed.

Enhancement in sintering driving force derived from in situ ordered structural collapse of mesoporous powders

AbstractIn this study, the sintering behaviors of a series of mesoporous silica (FDU‐12, SBA‐15, MCM‐41, and mesoporous silica nanoparticles) and microporous zeolite (ZSM‐5) using spark plasma sintering (SPS) technology were investigated. Highly transparent glass was prepared at a low temperature from all the powders. In particular, FDU‐12 type of mesoporous silica could be fully densified at an ultralow sintering temperature (910°C). It is suggested that the collapse of ordered mesostructures during SPS process dependents on the large pore size/pore wall thickness ratio, appropriate pore arrangement and amorphous frameworks of mesoporous silica, which implies that the enhancement in sinterability is possibly derived from the in situ collapse of ordered mesostructures. Such present findings pave a new way toward the construction of functional dense bulk materials from mesoporous powders.

Influence of modified mesoporous silica SBA-15 and compatibilizer on the properties and structure of ethylene-vinyl acetate copolymer-based nanocomposites

ABSTRACT Three series of poly(ethylene-co-vinyl acetate)/mesoporous silica type SBA-15 (EVA/SBA-15) nanocomposites, containing 1, 2, 3, and 4 wt% SBA-15 nanoparticles were prepared by melt blending in internal mixer. The mesoporous silica SBA-15 was synthesized by the sol-gel method and organomodified by Hexadecyltrimethoxysilane (HDTMS). The terpolymer of Ethylene-butyl acrylate-maleic anhydride (E-BA-MA) containing 6% butylacrylate, 3% maleic anhydride was added as compatibilizer at 2 wt% to nanocomposites including unmodified SBA-15. The chemical and physical properties of EVA/SBA-15 nanocomposites were characterized by infrared spectroscopy (FTIR), calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and rheology. The results confirmed that HDTMS was successfully incorporated into the surface of SBA-15. The crystallinity of the matrix decreased and Young’s modulus increased with the incorporation of the filler and in the presence of terpolymer as compatibilizer, whereas elongation at break and tensile strength kept almost the values of the matrix. The thermal stability of nanocomposites was enhanced as compared with the pure EVA matrix.