Walls Of Mesoporous Silica Research Articles

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

Dihydropyrano quinoline derivatives functionalized nanoporous silica as novel fluorescence sensor for Fe3+ in aqueous solutions(aq)

A novel nanoporous silica-based fluorescence sensor with high selectivity and sensitivity was successfully prepared via grafting of 3-isocyanatopropyltriethoxysilane and dihydropyrano [3, 2-c] quinoline derivatives (DPQ) onto the pore walls of mesoporous silica. The attachment of fluorophore groups onto the surface of the SBA-15 was approved via TGA and FT‐IR spectroscopy. TGA analysis indicates a large weight loss about 49%, which is attributed to the binding of a large number of organic groups on the pores surface, which functional groups appeared in the FT-IR spectra. Structural characterization techniques have proved the type IV for N2 adsorption-desorption isotherm, which revealed the preservation of the mesoporous structure. Also, low-angle XRD, FESEM and TEM analyses demonstrate the formation of ordered and well-defined 2D hexagonal mesoporous structure (space group p6mm). Whereas, Fe3+ ions caused discernible fluorescence quenching of the fluorescence sensor, the other cations used did not significantly changed fluorescence emission of SBA-Si-DPQ. The fluorescence quenching of the sensor is attributed to the paramagnetic properties of Fe3+ ions that appear by complex formation between the urea group of the probe and Fe3+ ions. It is noteworthy that, the excitation at 310 nm caused an emission with a maximum at 478 nm wavelength. By the increasing concentration of the analytes, the emission intensity was decreased dramatically and good linearity observed between analytes concentrations and the fluorescence intensity quenching of the sensor. The measured detection limits for Fe3+ ions was 2.0 × 10−6 M.

Study on the morphological regulation mechanism of hollow silica microsphere prepared via emulsion droplet template

The morphology regulation of hollow silica microspheres is significant for their properties and applications. In this paper, hollow silica microspheres were formed through the hydrolysis and condensation reaction of tetraethyl orthosilicate (TEOS) at the interface of the emulsion droplet templates composed of liquid paraffin and TEOS, followed by dissolving paraffin with ethanol. The effects of various factors including the emulsifier structure and content, TEOS content, catalyst type, and the ethanol content in the continuous water phase on the particle size, shell thickness and morphology of the prepared hollow silica microspheres were studied in detail. The results show that the diffusion and contact of TEOS and water molecules as well as the hydrolysis condensation reaction of TEOS at the oil-water interface are two critical processes for the synthesis and morphological regulation of hollow silica microspheres. Cationic emulsifier with a hydrophobic chain of appropriate length is the prerequisite for the successful synthesis of hollow silica microspheres. The ethanol content in water phase is the dominant factor to determine the average diameter of hollow microspheres, which can vary from 96 nm to 660 nm with the increase of the volume ratio of alcohol-water from 0 to 0.7. The silica wall thickness varies with the content and the hydrophobic chain length of the emulsifier, TEOS content, and the activity of the catalyst. The component of the soft template will affect the morphology of the silica wall. When the liquid paraffin is replaced by cyclohexane, hollow microspheres with fibrous mesoporous silica wall are fabricated. This work not only enriches the basic theory of interfacial polymerization in the emulsion system, but also provides ideas and methods for expanding the morphology and application of hollow silica microspheres.

Synthesis of bifunctional groups-integrated mesoporous silica hybrid adsorbent for simultaneous removal of Hg2+ and Cu2+ ions from aqueous solution

A mesoporous organosilica hybrid integrated with disulfide and amine groups was synthesized in a sol-gel co-condensation method using Pluronic P123 as structural directing surfactant. In the initial silane mixture, the organic functional groups content of disulfide and amine groups along with tetraethyl orthosilicate incorporated into the pore walls of mesoporous silica is approximately 30 mol/g (BDSTES: AAPTES is 15:15 mol/g). The surface area, pore volume and pore size of the prepared disulfide bridged and amine groups integrated mesoporous silica hybrid adsorbent (MSHA@SS-NH2) materials are approximately 462 m2/g, 0.58 cm3/g, and 2.6 nm, respectively. The MSHA@SS-NH2 adsorbent materials demonstrated that adsorption equilibrium could be achieved in 30 min and the adsorbed amount of Hg2+ and Cu2+ ions calculated to be about 166 mg/g and 153 mg/g, respectively, with the ∼ 90% of Hg2+ ions and ∼ 84% of Cu2+ ions removal capacity from the mixture of initial metal ions solutions (100 mg/L). By washing with 0.1 M HCl solution and regenerating with aqueous ammonia (3%) solution, the MSHA@SS-NH2 adsorbent demonstrated recyclable and reusable ability up to 5 times. As a result, the MSHA@SS-NH2 material developed could be used as an effective adsorbent for the simultaneous removal of Hg2+ and Cu2+ ions from wastewater.

Amphiphilic ionic liquid assembly route for the synthesis of polymer/Ag spheres and Ag-decorated bimodal porous silica

The multifunctional assembly of amphiphilic ionic liquids (AILs) can play an important role in the synthesis of various composite nanomaterials. In this work, we developed a novel strategy to steer the generation of polymer/AIL16/Ag spheres by using amphiphilic ionic liquid, 1-hexadecyl-3-methylimidazolium chloride (AIL16) as a “bridge”. Two kinds of polymer spheres (poly(methyl methacrylate), PMMA or polystyrene, PS) were used to assemble of the PMMA/AIL16/Ag (or PS/AIL16/Ag) microspheres. Subsequently, the PMMA/AIL16/Ag (or PS/AIL16/Ag) microspheres and AIL16 were used as templating agents of macropores and mesoporores respectively to prepare Ag-decorated bimodal porous silica. The effects of mass ratios of m(Ag)/m(PMMA, or PS) and amount of AIL16 on the formation of the PMMA (or PS)/AIL16/Ag microspheres and the Ag-decorated bimodal porous silica structure were investigated in detail. It was found that the dispersity and loading capacity of Ag nanoparticles onto the polymer spheres and the structures of the bimodal porous silica can be easily manipulated by changing the mass ratios of m(Ag)/m(PMMA, or PS) and the amount of adding AIL16. The obtained Ag-decorated bimodal porous silica exhibited three dimensional ordered spherical macroporous array with an ordered mesoporous silica walls, in which Ag-NPs with good dispersibility were immobilized onto the inner walls of the macroporous holes. Furthermore, the synthesized Ag-decorated bimodal porous silica displayed a better catalytic activity for the reduction reaction of 4-nitrophenol by using NaBH4 as reducer.

Highly selective fluorescence detection of Cu2+ based on Schiff base functionalized periodic mesoporous organosilicas.

A novel copper ion sensing periodic mesoporous organosilica (SCN-PMO) was obtained by incorporating a Schiff base-based fluorescent receptor into the pore walls of mesoporous silica, which exhibited a well ordered mesoporous structure and excellent optical properties demonstrated by various characterization results. SCN-PMO possessed high selectivity and sensitivity towards Cu2+ based on its specific fluorescence response. The detection limit of SCN-PMO could be as low as 6.7 × 10-7 M. Due to protection of the silica network, SCN chromophores in PMOs exhibited higher photostability and the resulting material possessed great repeatability. Additionally, the fluorescence changes of SCN-PMO towards copper ions in vivo (zebrafish) showed that SCN-PMO has potential application as a nanoprobe in biological fields.

Synthesis of functionalized mesoporous Ni-SBA-16 decorated with MgO nanoparticles for Cr (VI) adsorption and an effective catalyst for hydrodechlorination of chlorobenzene

In this research work the impact of MgO promoter tested on Ni-SBA-16 efficiency in aqueous media as an adsorbent for Cr(VI) and an effective catalyst for hydrodechlorination of chlorobenzene. New hydrothermal procedures were applied for the synthesis of Ni-SBA-16 and MgO/Ni-SBA-16 respectively. Results revealed that nanocomposites containing Ni nanocrystals of an average size distributed homogeneously within the pores of the amorphous silica matrix and also MgO was effectively coated on Ni-SBA-16 mesoporous silica walls, and that the mesoporous Ni-SBA-16 structure has been well preserved upon modification of MgO. The catalyst analysis results showed high interaction of unpromoted and MgO promoted catalyst Ni-SBA-16 as hydrodechlorination of chlorobanzene (≈ 96%) remained stable for 6 hours. The synthesized nanostructures were tested against Cr(VI) removal. 100% Cr(VI) adsorption was noted using 4 g/L and 200 mg/L of nanostructure and Cr(VI) respectively at temperature 75 °C, contact time 100 min and pH 3.

Preparation of Long-Term Antibacterial SiO2-Cinnamaldehyde Microcapsule via Sol-Gel Approach as a Functional Additive for PBAT Film

The mesoporous silica wall materials can achieve controlled load and sustained-release of active agents. An antimicrobial nanoscale silica microcapsule containing cinnamaldehyde (CA) was prepared by the sol-gel method and applied in poly (butyleneadipate-co-terephthalate) (PBAT) film. The surface morphology, physical and chemical properties, and antibacterial properties of microcapsules and films were studied. The effects of different temperatures and humidities on the release behavior of microcapsules were also evaluated. Results showed that CA was successfully encapsulated in silica microcapsule which had a diameter of 450–700 nm. The antibacterial CA agent had a long-lasting release time under lower temperature and relative humidity (RH) environment. At low temperature (4 °C), the microcapsules released CA 32.35% in the first 18 h, and then slowly released to 56.08% in 216 h; however, the microcapsules released more than 70% in 18 h at 40 °C. At low humidity (50%RH), the release rates of microcapsules at the 18th h and 9th d were 43.04% and 78.01%, respectively, while it reached to equilibrium state at 72 h under 90% RH. The sustained release process of CA in SiO2-CA microcapsules follows a first-order kinetic model. Physicochemical properties of PBAT films loaded with different amounts of microcapsules were also characterized. Results showed that the tensile strength and water vapor transmission rate (WVTR) of the composite film containing 2.5% microcapsules were increased by 26.98% and 14.61%, respectively, compared to the raw film, while the light transmittance was slightly reduced. The crystallinity of the film was improved and can be kept stable up to 384.1 °C. Furthermore, microcapsules and composite film both exhibited distinctive antibacterial effect on Escherichia coli and Listeria monocytogenes. Therefore, SiO2-CA microcapsules and composite films could be a promising material for the active packaging.

Pt/Ga-SBA-15 composites synthesis and characterization

Pt (0.5, 1 and 1.5 wt%) was impregnated by incipient wetness on SBA-15 and corresponding Ga-modified (3, 5, 10 and 20 wt%) composites. Gallium nitrate was incorporated directly during the mesoporous siliceous network synthesis. Materials were characterized by N2 physisorption, X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. SBA-15 had surface area greater than 800 m²/g that decreased by Ga incorporation in binary materials. It seemed that tetrahedral gallium was well-incorporated into mesoporous silica walls. Pt dispersion slightly diminished (as to that on SBA-15) by augmenting Ga concentration in composites. Corresponding pore size maxima shifted to lower diameters (as to that of non-impregnated supports) after platinum loading suggesting Pt crystals inside pores of SBA-15 and Ga-modified carriers. Large cubic platinum crystals were observed over all prepared materials probably due to sintering (during calcining at 500 °C) of metallic particles weakly interacting with the carriers surface. After materials annealing (500 °C under static air) metallic platinum was evidenced (by XRD) pointing out to noble metal reduction that could be facilitated by decomposition of organic remains from Si alkoxide used during supports synthesis which presence was ascertained by FTIR.

Controlled Synthesis of Manganese Oxide Nanoparticles Encaged in Hollow Mesoporous Silica Nanoreactors and Their Enhanced Dye Degradation Activity.

In this study, controlled synthesis of hollow mesoporous silica nanoreactors with small manganese oxide nanoparticles in their cavities (MnxOy@HMSNs) is reported, and the dye degradation performance in the presence of hydrogen peroxide over MnxOy@HMSNs is investigated. Specifically, triple ligands (a compound with three dipicolinic acid groups) were used to coordinate manganese ions to form negatively charged coordination complex networks, which further combine with positively charged copolymers to obtain metal ion-containing polymer micelles. Following silica deposition onto micellar coronas and calcinations simultaneously result in hollow mesoporous silica nanoreactors and manganese oxide nanoparticles in their cavities. In this work, the influences of synthetic parameters on the structures are studied in detail. The obtained MnxOy@HMSNs show greatly enhanced activity and stability for a series of dye degradations. The performance enhancement is ascribed to their unique nanostructures, where mesoporous silica walls provide protection to the inner MnxOy nanoparticles and the small size of the manganese oxide nanoparticles greatly enhances the dye degradation activity.

Palladium oxide nanoparticles intercalated mesoporous silica for solvent free acceptorless dehydrogenation reactions of alcohols

Abstract Aggregation-free well-dispersed palladium oxide nanoparticles intercalated into the walls of mesoporous silica (PdOMS) were prepared by using thioether groups during the sol-gel preparation of mesoporous silica. The PdOMS material was characterized by N2 adsorption-desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV–Vis spectroscopy. The material retains mesoporous structure with narrow pore size distribution with an average pore diameter of 6.8 nm and possesses high surface area of 683 m2g–1. The PdOMS catalyst was employed as an efficient heterogeneous catalyst in the acceptor- and oxidant-free dehydrogenation of neat alcohols to corresponding carbonyl compounds in very good to excellent yields (72–95%) at 80 °C under inert atmosphere. The catalytic efficacy of PdOMS has also been evaluated for the acceptorless dehydrogenative coupling reactions of alcohols with o-diamino benzene and o-amino phenol to yield azole-based heterocycles. The stability of PdOMS was assessed by investigating its recyclability and reusability in the dehydrogenation of neat alcohol for up to five cycles.

Rerouting engineered metal-dependent shapes of mesoporous silica nanocontainers to biodegradable Janus-type (sphero-ellipsoid) nanoreactors for chemodynamic therapy

In recent times, the fabrication of versatile mesoporous silica walls by incorporating various metal species has attracted enormous interest as they significantly enrich the functionalities of mesoporous silica nanoparticles (MSNs) by offering numerous advantages in diverse fields. Herein, we demonstrate the generation of mesoporous silica-based, dual-metal doped, biodegradable Janus-type (sphero-ellipsoid) nanoreactors using modified Stöber process by arranging two different transition metals in the silica walls, which facilitated the change of MSN’s shape, attributing to their similar charge as well as the distribution of intrinsic siliceous bonds in the confined architectures. As a proof-of-concept, the doped metal species in the silica walls have significantly augmented the loading efficiency of doxorubicin (Dox) through pH-responsive metal-ligand interactions, which specifically released Dox in the tumor endosomal acidic environment and synergized the antitumor efficacy by augmenting the intracellular levels of cytotoxic reactive oxygen species (ROS) through copper/iron(II)-catalyzed Fenton-like reaction. This innovative one-step approach for synthesizing Janus-type nanoreactors would be a conducive strategy and has great potential as a delivery system in diverse biomedical applications for treating various ailments. We also believe that the nanodevices in association with metals resulting in different shapes could significantly alter the therapeutic effects.

Palladium Intercalated into the Walls of Mesoporous Silica as Robust and Regenerable Catalysts for Hydrodeoxygenation of Phenolic Compounds.

Nanostructured noble-metal catalysts traditionally suffer from sintering under high operating temperatures, leading to durability issues and process limitations. The encapsulation of nanostructured catalysts to prevent loss of activity through thermal sintering, while maintaining accessibility of active sites, remains a great challenge in the catalysis community. Here, we report a robust and regenerable palladium-based catalyst, wherein palladium particles are intercalated into the three-dimensional framework of SBA-15-type mesoporous silica. The encapsulated Pd active sites remain catalytically active as demonstrated in high-temperature/pressure phenol hydrodeoxygenation reactions. The confinement of Pd particles in the walls of SBA-15 prevents particle sintering at high temperatures. Moreover, a partially deactivated catalyst containing intercalated particles is regenerated almost completely even after several reaction cycles. In contrast, Pd particles, which are not encapsulated within the SBA-15 framework, sinter and do not recover prior activity after a regeneration procedure.

Long chain ionic liquid-assisted synthesis of PS/Pd beads and hierarchical porous Pd-SiO2.

Long-chain ionic liquid, 1-hexadecyl-3-methylimidazolium chloride (C16mimCl), was firstly used as a linking agent to construct polystyrene (PS)/C16mimCl/palladium (Pd) beads. Subsequently, the PS/C16mimCl/Pd beads were used as a macroporous templating agent and C16mimCl was used as a mesoporous templating agent to prepare Pd-loaded hierarchical porous silica. A systematic study was carried out addressing the influence of the amount of C16mimCl and the mass ratios of m(Pd)/m(PS) on the PS/C16mimCl/Pd beads and the Pd-loaded hierarchical porous structures. The samples were characterized by electrophoresis experiments, SEM, TEM, small-angle XRD, and N2 adsorption–desorption experiments. It was found that the coverage of citrate-coated Pd nanoparticles (Pd NPs) onto the PS beads can be simply tailored by changing the amount of C16mimCl and the mass ratios of m(Pd)/m(PS). The resultant Pd-loaded hierarchical porous silica possessed a 3D ordered macroporous skeleton with a specific surface area of up to 967 m2 g−1, ordered mesoporous silica walls (SBA-3 type) and well-dispersed Pd NPs anchored on the inner walls of the spherical macroporous hollow. Importantly, the obtained Pd-loaded hierarchical porous silica exhibited an enhanced catalytic activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2.

Zero-valent iron particles embedded on the mesoporous silica–carbon for chromium (VI) removal from aqueous solution

Nanoscale zero-valent iron (nZVI) particles were embedded on the walls of mesoporous silica–carbon (MSC) under the conditions of high-temperature carbonization and reduction and used to remove chromium (VI) from aqueous solution. The structure and textural properties of nZVI–MSC were characterized by the powder X-ray diffraction, transmission electron microscopy and N2 adsorption and desorption. The results show that nZVI–MSC has highly ordered mesoporous structure and large surface area, indistinguishable with that of MSC. Compared with the support MSC and iron particles supported on the activated carbon (nZVI/AC), nZVI–MSC exhibited much higher Cr(VI) removal efficiency with about 98 %. The removal process obeys a pseudo first-order model. Such excellent performance of nZVI–MSC could be ascribed to the large surface and iron particles embedded on the walls of the MSC, forming an intimate contact with the MSC. It is proposed that this feature might create certain micro-electrode on the interface of iron particles and MSC, which prevented the formation of metal oxide on the surface and provided fresh Fe surface for Cr(VI) removal.

Porosity of SBA-15 after functionalization of the surface with aminosilanes

Functionalization of the mesoporous silica walls by organic species results in formation of porous hybrid materials. Combination of organic and inorganic components leads to the materials whose properties differ considerably from those of their individual, isolated components, especially with respect to their surface chemistry, hydrophilicity/hydrophobicity and/or pore connectivity and size distribution. In this paper a detailed porosity characterization of SBA-15 silica before and after its surface functionalization with (R2O)3-Si-R1-NH2 molecules is reported. The results obtained from nitrogen sorption were compared to those derived from quasi-equilibrated thermodesorption of n-nonane and from water and n-heptane thermoporosimetry. A small decrease of the pores size and pore volume upon the modification was detected for all amine functionalities, the largest in the case of N-(2-aminoethyl)-3-(trimethoxysilyl) propylamine. Water thermoporosimetry was found to be the most sensitive method, allowing to quantify these differences.

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica.

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

Synthesis of mesoporous carbons using silica templates impregnated with mineral acids

The pore walls of SBA-15, SBA-16 and KIT-6 mesoporous silica were acidified via the impregnation of phosphoric acid or sulfuric acid prior to their use as a template for mesoporous carbon synthesis with furfuryl alcohol. The effect of acid functionalization on carbon synthesis was investigated using X-ray powder diffraction, N2 adsorption, transmission electron microscopy, and solid-state 13C and 31P NMR spectroscopy. The results indicated that a significant portion of the impregnated mineral acid formed an ester with the surface silanol group. Therefore, the impregnated acid could lead to the selective formation of carbon frameworks inside the template pores, preventing external carbon deposition even when furfuryl alcohol was used excessively. The mineral acid impregnation yielded highly faithful carbon replicas of the mesoporous silica.

Simultaneous determination of carcinoembryonic antigen and α-fetoprotein using an ITO immunoelectrode modified with gold nanoparticles and mesoporous silica

We report on an electrochemical immunoassay for simultaneous detection of the tumor markers carcinoembryonic antigen (CEA) and α-fetoprotein (AFP). Gold nanoparticles (AuNPs) were synthesized inside the internal pore walls of mesoporous silica (MPS). Then, Methylene blue (MB) and 6-ferrocenylhexanethiol (FeC), which act as electrochemical substrates, were incorporated into the channels via the formation of Au-S bonds. Finally, monoclonal antibodies against CEA (anti-CEA) and AFP (anti-AFP) were immobilized in the channels of MB-AuNPs-MPS and FeC-AuNPs-MPS, respectively. Suspensions of anti-CEA/MB-AuNPs-MPS and of anti-AFP/FeC-AuNPs-MPS were deposited on two different sites of the ITO electrode. When incubated with samples containing the two analytes, the formation of electrically nonconductive immunoconjugates blocks electron transfer. Simultaneous detection of CEA and AFP was accomplished by monitoring the current change before and after an immunoreaction has occurred. The AuNPs confined inside the channels are promoting the electron transport and thus improve detection limits. The immunoelectrode responds to CEA in the 0.5–50 ng mL−1 concentration range, and to AFP in concentrations between 0.5 and 100 ng mL−1. The detection limits (at an S/N of 3) are 0.1 ng mL−1 in both cases.