Modification Of Mesoporous Silica Research Articles

Adsorption removal of copper(II) from water by zero valent iron loaded dendritic mesoporous silica

The object of research is synthesized dendritic mesoporous nanoscale silica (DMSN) modified with zero-valent iron (Fe0@DMSN). This material exhibits a high adsorption capacity for heavy metal ions, in particular copper, whose increased content in the aquatic environment poses a threat to living organisms. In this regard, the main physicochemical features of the removal of copper cations from the aqueous medium using the obtained sample were investigated. The morphology of the obtained dendritic silicas was studied by electron microscopy and the presence of a layer of zero-valent iron was confirmed by X-ray diffraction analysis and infrared spectroscopy. The parameters of the porous structure of the synthesized materials were determined. It was found that after modification of mesoporous silica with particles of zero-valent iron, the value of its specific surface area decreased from 504 m2/g to 312 m2/g. This may be due to the formation of a Fe0 layer not only on their surface but also in the channels of the inorganic matrix, which has a unique dendritic structure characteristic of this type of particles. At the same time, the number of active centers increases due to the enrichment of the silica surface with functional modifier groups that show a high affinity for metal cations. The adsorption capacity of Fe0@DMSN towards Cu2+ ions has been studied and it has been shown that the maximum adsorption value is 39.8 mg/g, which is significantly higher than that of the initial synthesized DMSN sample (0.7 mg/g). The experimental data obtained indicate that the obtained sorption material based on dendritic mesoporous silica nanoparticles with a layer of reactive zero-valent iron can be used for the purification of water contaminated with metal ions. In addition, the magnetic properties of such materials, known and proven by various scientists, will make it easy to separate the solid phase in the processes of sorption water purification using magnetic separation.

Alkaline Modified Mesoporous Silica Supported Ruthenium Catalyst for Improved α-Amino Acid Synthesis.

Amino acids are a class of compounds with wide-ranging applications. The synthesis of amino acids from biomass-derived α-keto acids and ammonia is a sustainable way but the unstable primary imine intermediates (R-C=NH) easily form oligomers. Herein, targeting this problem, alkaline modified mesoporous silica was employed as a support for ruthenium (Ru/M-MCM-41), which could be used as a bifunctional catalyst in the reductive amination of α-keto acids to synthesize α-amino acids. The incorporation of Sr improved the dispersion of Ru nanoparticles and enhanced metal-support interactions via electron transfer from Sr to Ru, and the active Ru sites could efficiently hydrogenate primary imine intermediates to α-amino acids, thus prohibiting the formation of oligomers. Moreover, the Sr-dopant introduces base sites that could catalyze the hydrolysis of oligomers back to primary imine intermediates and finally hydrogenated to α-amino acids. As a result, >99 % yield of glycine was achieved from glyoxylic acid over Ru/Sr-MCM-41, which is nearly three times that achieved over Ru/MCM-41 (32.2 %).

Utilization of Deoxycholic Acid Terminated L-cysteine Modified Mesoporous Silica Nanoparticles as a Nanoadsorbent for Removing Rhodamine B from Contaminated Water: Adsorption Equilibrium and Kinetic Studies

Utilization of Deoxycholic Acid Terminated L-cysteine Modified Mesoporous Silica Nanoparticles as a Nanoadsorbent for Removing Rhodamine B from Contaminated Water: Adsorption Equilibrium and Kinetic Studies

A high surface area mesoporous silica adsorbent for uranium uptake from lean uranium solutions: Template assisted preparation of mesoporous silica and its functionalization with iminodiacetic acid

The feasibility of uranium recovery from lean uranium solutions (like seawater) having extremely low concentrations has been explored using an iminodiacetic acid (ImDAc) modified mesoporous silica (MPS) adsorbent (MPS-ImDAc). Foremost, synthesis of the MPS, its chemical modification using ImDAc and characterization were emphasized. The MPS was prepared by a template assisted preparative route, and the incorporation of ImDAc moiety to the MPS was accomplished through chemical functionalization. Subsequently, the adsorption efficacy of the MPS-ImDAc has been investigated as a function of the pH of the aqueous medium, kinetics of adsorption, uranium loading to the adsorbent, and the effect of interfering elements. Zeta potential analyses were also conducted to investigate the role of ImDAc functional groups and charges at different pH values, and the study suggested that the negatively charged acetate moiety is likely responsible for adsorption above pH.The adsorption has been modeled using pseudo-first and second order kinetic and the Langmuir adsorption isotherm models. Superior adsorption of uranium above pH 4, based on cation exchange mechanism that leads to an adsorption capacity of approximately 110 mg/g was observed. Adsorption characteristics have been investigated from a synthetic seawater composition with all possible interfering elements, and the study confirmed that though sodium is significantly present in sea water, it has negligible adsorption to ImDAc and thus pose no competition to uranium adsorption. Small pore size and massive surface area of MPS in combination with uranium selective ImDAc functional group offer excellent uranium adsorption.

An Immobilized Amine with Improved Cyclic Performance Prepared from Carboxyl Modified Mesoporous Silica for CO2 Capture

AbstractImmobilized amines adsorbents have excellent CO2 adsorption capacity and low regeneration energy consumption, which have broad application prospect, but poor reusability. To improve the cyclic adsorption performance of immobolized amines for CO2 capture, the mesoporous silica A‐MSU‐J with carboxyl groups on the surface was synthesized, and immobilized amine A‐MSU‐J‐TEPA was prepared by introducing tetraethylenepentamine (TEPA) by impregnation method. The introduction of carboxyl groups onto the carrier surface can form stronger hydrogen bonds with TEPA than the initial hydroxyl groups, thus achieving stable loading of TEPA. When the TEPA load was 50 wt %, the adsorption capacity of 4A‐65MSU‐J‐50TEPA declined by only 13.7 % (from 2.58 to 2.23 mmol ⋅ g−1, at 70 °C, 0.1 Mpa) after 10 cycles, while the adsorption capacity of 65MSU‐J‐50TEPA decreased by 23.6 % (from 2 to 1.53 mmol ⋅ g−1). Furthermore, carrier pore size also affects the adsorption capacity of immobilized amines for CO2. The adsorption capacity of 4A‐65MSU‐J‐50TEPA with larger pore size (2.95 mmol ⋅ g−1, at 55 °C) is much higher than that of 4A‐25MSU‐J‐50TEPA with smaller pore size (2.17 mmol ⋅ g−1). In conclusion, improving the interaction between organic amines and the carrier surface and using carriers with larger pore size can enhance the adsorption capacity and reusability of immobolized amines adsorbents.

Preparation and Characterization of a Novel Additive for Elastomeric Polymer from Oligoisoprene Modified Mesoporous Silica

This manuscript presents a novel instant additive for elastomeric polymers, specifically focusing on the modification of synthesized mesoporous silica using carbonyl telechelic natural rubber (CTNR). The surface of mesoporous silica particles was modified using a two-step approach. In the first step, a strategy involving the grafting of 3-aminopropyltriethoxysilane (APTES) onto the silica particles was employed. Subsequently, in the second step, a Schiff's base reaction was carried out between the aldehyde functional group of CTNR and the amines on the modified silica surface. The grafting percentage achieved through this process was determined to be 4.70%. This novel instant additive has the potential to enhance the properties and performance of elastomeric polymers by leveraging the unique characteristics of CTNR and the mesoporous silica surface. Further investigations and applications of this additive can contribute to advancements in the field of elastomeric polymer materials.

Drug removal and release studies of mesoporous and modified silica

ABSTRACT The synthesis, characterization and modification of mesoporous silica (MS) were carried out and, drug removal and release studies were also performed. The synthesized MS has an ordered structure with high surface area and homogeneous pore size distribution, which was then modified with a Schiff base (S) ligand. The characterization of MS and Schiff base modified MS (S-MS) was accomplished with scanning electron microscopy (SEM), nitrogen gas adsorption, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) analyses. The adsorption of diclofenac sodium (DS) and metformin HCl (MF), which were preferred as model drugs, onto MS and S-MS, was investigated in an aqueous solution with respect to pH, the amount of adsorbent and contact time. The maximum calculated values from the pseudo-second-order model for the adsorption of MF and DS were determined as 625.5 and 675.0 mg g‒ 1 for MS and 558.5 and 765.7 mg g‒ 1 for S-MS, respectively. In addition, the hybrid structures of MS and S-MS were prepared for use in the drug release studies, and their efficiencies in releasing drugs were then investigated. The releases of DS and MF from silica hybrid structures after 4 h were determined to be at around 30% and 70%, respectively.

Superhydrophobic Pt@SBA-15 catalyst for tritium separation in liquid phase catalytic exchange

Through the modification of mesoporous silica (SBA-15), a hydrophobic microscopic reaction environment was constructed, which was beneficial to improve the catalytic activity of the LPCE reaction. The Pt@SBA-15-tetramethyldisilazane catalyst is prepared by the modification of the SBA-15 carrier and the loading of metal Pt, with a water contact angle of 158°. This superhydrophobic structure can enhance the catalytic performance and can prevent the deactivation of the catalyst. By measuring the actual catalytic performance of tritium water under different conditions, we found that it has good catalytic activity, and the catalyst can still maintain a high catalytic activity after 30 days in tritium water environment.

A pH/temperature responsive nanocomposite for chemo-photothermal synergistic cancer therapy

To optimize synergistic breast cancer treatment, a nanocomposite was fabricated with pH-temperature responsive and chemo-photothermal combination therapy. Herein, gold nanorods (AuNRs) are coated with [poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (p(NIPAM-co-MAA)) modified mesoporous silica (MS) for Doxorubicin (DOX) delivery (AuNR@DOX-MS@p(NIPAM-co-MAA)). Upon NIR radiation, the AuNR core induced hyperthermia via generating heat. Simultaneously, the polymer layer collapsed in response to high temperature/low pH, which allowed the triggering of DOX release from the MS shell at the tumor site. With this nanocomposite, nearly zero premature release of DOX at physiological pH/temperature was detected, while effective DOX release was reported at higher temperature/lower pH values. In addition, in vitro studies demonstrated that the nanocomposite has a substantial uptake efficiency of MDA-MB-231 breast cancer cells, with a significant increase in suppressing MDA-MB-231 ​cell proliferation in response to laser irradiation. The in vivo experiments further verified the high efficiency of the fabricated nanocomposite in accumulating at the tumor site and the good capability in suppressing tumor growth in the mice upon intravenous injection, while exhibiting good biosafety in relation to major organs in the body. Thus, the synthesized nanocomposite could be a potential nanocarrier for breast cancer treatment with synergistic chemo-photothermal therapeutic capability.

Engineering Modified Mesoporous Silica Catalysts through Porosity and Surface Acidity Control for Selective Production of DME

DME has been received the attention as a renewable energy due to its thermal efficiencies equivalent to diesel fuel, lower NOx emission, near-zero smoke and non-toxic. DME can be obtained by methanol dehydration over solid acid catalysts or directly from syngas over bifunctional catalysts. The catalytic dehydration of methanol to DME has been widely studied in the literature over pure or modified γ -aluminas (γ-Al2O3) and zeolites. Mesoporous silica has obtained much consideration due to its well-defined structural order, high surface area, and tunable pore diameter. In this work, sulfonic acid and aluminium modified mesoporous silica were synthesized and tested as catalysts for production of dimethyl ether from methanol. The modified silicas were studied utilizing XRD, N2 physisorption, pyridine adsorption, and scanning electronic microscopy. The effects of reaction temperature and water deactivation on the methanol selectivity and conversion to dimethyl ether were investigated. Sulfonic acid modified mesoporous silica showed higher selectivity and stability of DME than that of aluminosilicate. The grafting of mesoporous silica with sulfonic groups displayed much more enhanced hydrothermal stability than Al-MCM-41 and γ-Al2O3.

Evaluation of Chitosan Derivatives Modified Mesoporous Silica Nanoparticles as Delivery Carrier

Chitosan is a non-toxic biological material, but chitosan is insoluble in water, which hinders the development and utilization of chitosan. Chitosan derivatives N-2-Hydroxypropyl trimethyl ammonium chloride (N-2-HACC) and carboxymethyl chitosan (CMCS) with good water solubility were synthesized by our laboratory. In this study, we synthesized mesoporous SiO2 nanoparticles by the emulsion, and then the mesoporous SiO2 nanoparticles were modified with γ-aminopropyltriethoxysilane to synthesize aminated mesoporous SiO2 nanoparticles; CMCS and N-2-HACC was used to cross-link the aminated mesoporous SiO2 nanoparticles to construct SiO2@CMCS-N-2-HACC nanoparticles. Because the aminated mesoporous SiO2 nanoparticles with positively charged can react with the mucous membranes, the virus enters the body mainly through mucous membranes, so Newcastle disease virus (NDV) was selected as the model drug to evaluate the performance of the SiO2@CMCS-N-2-HACC nanoparticles. We prepared the SiO2@CMCS-N-2-HACC nanoparticles loaded with inactivated NDV (NDV/SiO2@CMCS-N-2-HACC). The SiO2@CMCS-N-2-HACC nanoparticles as delivery carrier had high loading capacity, low cytotoxicity, good acid resistance and bile resistance and enteric solubility, and the structure of NDV protein encapsulated in the nano vaccine was not destroyed. In addition, the SiO2@CMCS-N-2-HACC nanoparticles could sustain slowly released NDV. Therefore, the SiO2@CMCS-N-2-HACC nanoparticles have the potential to be served as delivery vehicle for vaccine and/or drug.

Indocyanine Green Loaded Modified Mesoporous Silica Nanoparticles as an Effective Photothermal Nanoplatform.

Photothermal therapy possesses great advantages for the treatment of drug-resistant tumors. Herein, Near Infrared (NIR)-triggered photothermal nanoparticles were developed through loading indocyanine green (ICG), a kind of NIR dye, into amino group-modified silica nanoparticles (SiO2-NH2 NPs). SiO2-NH2 NPs were prepared with immobilization of the amino groups into the framework of silica nanoparticles (SiO2 NPs) by employing (3-aminopropyl)-triethoxysilane (APTES). Before and after the modification of the amino group, the particle sizes of SiO2 NPs showed similar value, around 100 nm. ICG was further adsorbed into SiO2-NH2 NPs by electrostatic attraction to enable SiO2-NH2@ICG NPs as a kind of photothermal agent. The loading rate of ICG to SiO2-NH2 was greatly increased compared to unmodified SiO2, and the stability of ICG was also improved. Moreover, the SiO2-NH2@ICG NPs exhibited efficient photothermal effects due to ICG transforming laser power into local heat through the connected ICG, when NIR laser irradiation turned on for a couple of minutes. Finally, the in vitro antitumor efficacy of SiO2-NH2@ICG NPs was investigated by recording cell proliferation rate and further chronicled the apoptotic morphology evidence by a Calcein-AM/PI fluorescent staining assay, indicating the efficient photothermal targeted therapy for the HepG2 tumor cells.

Erratum: Sun, X.; et al. Folic Acid and PEI Modified Mesoporous Silica for Targeted Delivery of Curcumin. Pharmaceutics, 2019, 11, 430.

The authors wish to make the following corrections to this paper [1]: [...].

A Solvent Free Approach for the Preparation of Silver Modified Mesoporous Silica for Iodine Entrapment

A green solvent-free approach, using a heating/grinding method, was employed to produce grey colored Ag functionalized mesoporous silica (here SBA-15). This material consisted of Ag0 nanoparticles with diameters of around 1.5 ± 0.45 nm inside the pores of SBA-15, and aggregated silver nanoparticles on the outside of the SiO2. Indeed due to a lack of a strong stabilizer the degree of particle aggregation is high. This easy to handle powder was then used to extract molecular Iodine. The resulting yellow powder was examined by Ultraviolet–Visible (UV–Vis) and Fourier-transform Infrared spectroscopies, X-rays diffraction, thermogravimetric analysis (TGA) and scanning and transmission electron microscopy (SEM/TEM). It was found that the aggregates of individual Ag nanoparticles disaggregate as AgI quantum dots are formed, explaining the high I2 capacity exhibited by these materials, almost 1:1 Ag to I. Despite numerous washing steps with a range of solvents (ranging from cyclohexane to water) no leaching was observed. Finally, TGA demonstrated an increased melting point for the AgI dots indicating a degree of protection from the silica support.

Synthesis and modification of mesoporous silica with sulfated titanium dioxide as a heterogeneous catalyst for biodiesel production from palm fatty acid distillate

This study synthesizes fatty acid ethyl ester (FAEE) through esterification reaction of palm fatty acid distillate (PFAD) using SO42−/TiO2 supported by mesoporous silica as a catalyst. The steps of this study were a synthesis of mesoporous silica, catalyst preparation by impregnation and catalyst activity test through esterification reaction of PFAD by using ethanol. The variables of study on the esterification reaction were the weight ratio of catalyst and PFAD as 3%, 5%, 7%. Based on BET characterization, it shows that synthesized silica material is mesoporous silica. The characterization result of silica and catalyst using X-Ray of wide-angle powder (WAXRD) and SEM gives information that the existence of silica as support of SO42−/TiO2 active site. At the catalyst activity test through esterification reaction, it was obtained the best weight ratio of catalyst and PFAD was 5% with the conversion of ethyl ether formation as 98.9 %. Analysis data and physical properties were viscosity at a temperature of 40 °C and density at the temperature of 15 °C, it shows that the value fit a biodiesel standard of ASTM, meanwhile analysis data of GC-MS toward product of ethyl ester and PFAD has shown that most of the fatty acid in PFAD had been converted into ethyl ester.

Folic Acid and PEI Modified Mesoporous Silica for Targeted Delivery of Curcumin.

Nano anti-cancer drug carriers loaded with antineoplastic drugs can achieve targeted drug delivery, which enriches drugs at tumor sites and reduces the toxic side effects in normal tissues. Mesoporous silica nanoparticles (MSN) are good nano drug carriers, as they have large specific surface areas, adjustable pore sizes, easily modifiable surfaces, and good biocompatibility. In this work, polyethyleneimine (PEI) grafted MSN were modified with folic acid (FA) as an active target molecule using chemical methods. The product was characterized by SEM, TEM, Zetasizer nano, FTIR, and an N2 adsorption and desorption test. MSN-PEI-FA are porous nano particles with an average particle size of approximately 100 nm. In addition, the loading rate and release behavior of MSN-PEI-FA were studied with curcumin as a model drug. The results show that when loading curcumin to MSN-PEI-FA at 7 mg and 0.1 g, respectively, the encapsulation efficiency was 90% and the cumulative release rate reached more than 50% within 120 h at pH = 5. This drug delivery system is suitable for loading fat-soluble antineoplastic drugs for sustained release and pH sensitive delivery.

Modification of mesoporous silica with phosphotungstic acid and its effects on the combustion and thermal behavior of polylactic acid composites

Highly ordered mesoporous silica (SiO2) modified with phosphotungstic acid (PWA), was successfully prepared by vacuum impregnation. The chemical structure of as-designed PWA-mesoporous silica (PWA-SiO2) was characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra and small-angle X-ray scattering. PWA-SiO2, in association with intumescent flame retardant (IFR), was introduced into polylactic acid (PLA) by melt blending to obtain flame resistant composites. The flammability evaluation indicated that the presence of 19.0 wt% IFR and 1.0 wt% PWA-SiO2 in PLA achieved the maximal LOI value of 47.2%, passed the UL-94 V-0 rating, and significantly decreased the peak heat release rate from 622.4 kW m−2 of neat PLA to 182.3 kW m−2. The introduction of PWA-SiO2 could also slightly improve the mechanical properties of PLA composites. It is proposed that PWA-SiO2, which exhibits excellent catalytic effect, can play roles together with IFR in both condensed phase through promoting the formation of continuous dense char layer and gas phase through releasing non-flammable gas.

Experimental and theoretical investigations of novel synthesized organo-silane compounds and modified mesoporous silica materials

In this study, the novel compounds (2,5-dimethoxy-methanimine propyltriethoxysilane; S1 and 3-ethoxy-salicylaldimine propyltriethoxysilane; S2) derived from aminopropyltriethoxysilane (APTES) were synthesized by a simple and facile approach in order to modify mesoporous silica (MS) surface. Characterization of S1 and S2 was experimentally performed by FTIR, 1H13C NMR spectroscopic methods and elemental analysis. The IR frequencies, 1H and 13C NMR chemical shift values for the optimized molecular geometries of S1 and S2 were calculated by using Density Functional Theory (DFT with B3LYP/6-311 + G (d, p) basis set), and the theoretical results were compared to the obtained experimental data. The experimental and theoretical results confirmed the proposed molecular structures of the synthesized S1 and S2 compounds. After that, the mesoporous silica material (MS) was synthesized according to the Stöber procedure, and characterized by the elemental analysis, and the experimental and theoretical IR spectra. The surface of MS was successfully functionalized with S1 and S2 to produce more selective and effective adsorbent materials, and the structures of functionalized MSs (S1-MS and S2-MS) were investigated with FTIR spectroscopy and elemental analysis. The theoretical optimized molecular geometries, IR frequencies and 1H13C NMR chemical shift values were calculated to execute the structural analysis of S1-MS and S2-MS. In addition, the calculations of the sum of electronic and thermal free energy (SETFE), dipole moment, the HOMO-LUMO energies, the molecular electrostatic potential (MEP), the solvent accessible surface (SAS) and atomic charge for the synthesized S1, S2, MS, S1-MS and S2-MS were accomplished by using DFT/B3LYP/6-311 + G (d, p) level of theory.

Modification of mesoporous silica with molecular imprinting technology: A facile strategy for achieving rapid and specific adsorption

In order to improve the diffusion kinetics of molecularly imprinted materials (MIMs), applying imprinting technology to mesoporous materials is a promising strategy. In the present study, an imprinting approach based on the combination of mesoporous silica materials and molecular imprinting technology is reported. Molecularly imprinted material (MIM) for 2,4-dichlorophenoxyacetic acid (2,4-D) was prepared by using 2,4-D as the template molecule, alkyne-modified β-cyclodextrin and propargyl amine as the combinatorial functional monomers and SBA-15 as the supporter. The functional monomers were anchored to the azide-modified SBA-15 by azide–alkyne Click reaction. The synthesized MIM was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermal gravimetric analysis (TGA), low-angle X-ray diffraction (XRD) and N2 adsorption–desorption analysis. The interactions between template and functional monomers were studied by proton NMR analysis and UV–vis experiments. The results of the equilibrium binding experiments and selective tests showed that the prepared MIM has binding affinity and specificity for a group of analytes which have similar size and shape to those of template. Binding kinetic experiments demonstrated that the present imprinting approach can effectively enhance the mass transfer rate. The solid phase extraction of 2,4-D using MIM as the adsorbent was investigated. The extraction conditions for the processes of loading, washing and eluting were optimized. The recoveries of the molecularly imprinted solid phase extraction (MISPE) column for 2,4-D were 76.3–88.9% with relative standard deviations (RSD) of 3.48–7.64%.

Front Cover: Etherification of 5‐Hydroxymethylfurfural to Biofuel Additive Catalyzed by Aquivion® PFSA Modified Mesoporous Silica (Eur. J. Inorg. Chem. 33/2018)

Front Cover: Etherification of 5‐Hydroxymethylfurfural to Biofuel Additive Catalyzed by Aquivion® PFSA Modified Mesoporous Silica (Eur. J. Inorg. Chem. 33/2018)