Organic-inorganic Hybrid Mesoporous Silica Research Articles

Pd(II)/Pd(0) Anchored on Magnetic Organic–Inorganic Hybrid Mesoporous Silica Nanoparticles: A Nanocatalyst for Suzuki–Miyaura and Heck–Mizoroki Coupling Reactions

Pd(II)/Pd(0) Anchored on Magnetic Organic–Inorganic Hybrid Mesoporous Silica Nanoparticles: A Nanocatalyst for Suzuki–Miyaura and Heck–Mizoroki Coupling Reactions

Functionalized mesoporous silica as a fluorescence sensor for selective detection of Hg2+ in aqueous medium.

We combined the virtues of mesoporous silica and organic functional groups to develop a hybrid fluorescent sensor, PyU-SBA-15, with excellent ability to detect Hg2+ in aqueous medium with high selectivity. In this sensor, the pyrene fluorophore acts as the reporter and the urea unit acts as the receptor during Hg2+ determination. The control material, PyH-SBA-15, which lacks a carbonyl group in the receptor portion, did not display metal-ion selectivity, thereby demonstrating that introducing an additional metal-chelating unit is necessary to improve the metal-ion selectivity of the hybrid sensor. When the concentration of Hg2+ was increased, the fluorescence emission intensities of PyU-SBA-15 at 379, 398, and 476nm gradually decreased. The emission intensity at 379nm was linearly proportional to Hg2+ concentrations in the range of 0-1.0×10-4M, and the sensor was determined to have a detection limit of 9.92×10-8M. This work provides an effective strategy for improving or modulating the metal-ion selectivity of fluorescent sensors based on organic-inorganic hybrid mesoporous silica systems.

Hypoxia-responsive, organic-inorganic hybrid mesoporous silica nanoparticles for triggered drug release

Hypoxia is a manifestation of various diseases with an ischemic component, including cancer. Tumor hypoxia is a hallmark of cancer, creating an opportunity to exploit hypoxia to ensure delivery of anticancer drugs to cancer cells. Here, we describe the development of nanoparticles that specifically release drugs under hypoxic conditions. To this end, we prepared a hybrid mesoporous silica nanoparticle, modified to contain 4-(phenylazo)benzoic acid (4-PA, SNA) and β-cyclodextrin (β-CD, SNAC) on the external surface. 4-PA and β-CD act through host-guest interactions to serve as gatekeepers to block the pores of mesoporous sililica nanoparticles (SN), and subsequent selective cleavage of the azo group of 4-PA by intracellular nitroreductases under hypoxic conditions allows the release of entrapped drugs. Under normoxic conditions, doxorubicin (DOX)-loaded SNAC (DOX@SNAC) showed low cytotoxicity, reflecting inhibition of premature release of DOX from SNAC by 4-PA and β-CD. In contrast, under hypoxic conditions, DOX@SNAC showed significant cytotoxicity, similar to that of free DOX. Collectively, these results show that SNAC can function as effective drug-delivery systems in hypoxic conditions. Moreover, these SNACs, hypoxia-responsive hybrid mesoporous silica nanoparticles, could be effective not only in cancer, but also other diseases characterized by ischemic conditions.

Biodegradable hybrid mesoporous silica nanoparticles for gene/chemo-synergetic therapy of breast cancer.

Mesoporous silica nanoparticles have been extensively explored in anticancer nanomedicine due to their excellent biodegradability, which is one important focus in their further clinical translations. However, the traditional design concepts based on the functional modification with active groups cannot significantly improve the controlled drug release efficiency and anticancer effect. Herein, a molecularly organic-inorganic hybrid mesoporous silica nanoparticle (HMSN) nanocarrier coated with hyaluronic acid (HA) and polyethyleneimine (PEI) was constructed for the gene/chemo-synergetic therapy of breast cancer. Notably, HMSN with tumor-sensitive disulfide bond and targeting ligand HA can be decomposed when it encounters high concentration of glutathione (GSH) and hyaluronidase (HAase). The biodegradability of host molecules and the fast disintegration of the framework in tumor microenvironment can also accelerate the stimuli responsive release of cargos inside the pore space. Furthermore, the grafting of polyethyleneimine (PEI) could increase gene loading efficiency. From the above, the smart approach involves a combination of biodegradability and biological effect and results in synergetic antitumor effect of gene and chemical drug on breast cancer. All these findings demonstrated that HMSN/HA/PEI nanocarriers can be suitable for biomedical application, paving the way to fast development of multi-functional nano-biomedicine.

Silica-based organic-inorganic hybrid nanoparticles and nanoconjugates for improved anticancer drug delivery.

After the introduction of first generation MSNs for drug delivery with some challenges such as large particle sizes, irregular morphologies and aggregations, second generation provided uniform spherical morphologies, tunable pore/particle sizes and compositions. Henceforth, organic-inorganic hybrid mesoporous silica nanosystems have grown rapidly and utilized for active and passive targeting of tumorigenic cells especially conjugated with organic polymers followed by third generation counterparts with improved functionalities for cancer therapy. The aim of this review article is to focus on the advancements in mesoporous silica based organic-inorganic hybrid nanoparticles developed as drug carriers targeting cancer cells. Brief introduction to the state-of-the-art in passive and active targeting methods is presented. Specifically, therapeutic, diagnostic and theranostic applications are discussed with emphases on triggered and ligand conjugated organic-inorganic hybrid mesoporous silica nanomaterials. Although mesoporous silica nanoparticles perform well in preclinical tests, clinical translation progresses slowly as appropriate doses needs to be evaluated for human use along with biocompatibility and efficiency depending on surface modifications.

Direct conversion of xylose to furfuryl alcohol on single organic–inorganic hybrid mesoporous silica-supported catalysts

One-step conversion of xylose to furfuryl alcohol was investigated over Pt catalysts supported on ordered mesoporous SBA-15 bearing SO3H acid groups. Samples were characterized by SAXRD, FTIR, 29Si CP-NMR, XRF, FE-SEM and TG-MS, and they were all tested in aqueous-phase conversion of xylose in a semi-batch reactor. It was found that the presence of acid sites enhances catalytic activity, confirming that they are also playing a role in xylose conversion. A coupled activity of both metal and acid surface centres was thus suggested. The distribution of products was also found to be significantly modified by grafting organosulfonic groups on catalyst surface; while xylitol was the main product on unmodified Pt/SBA-15 catalyst (selectivity of 45%), a remarkable selectivity of 83–87% to furfuryl alcohol was accomplished over the catalysts supported on organic–inorganic hybrid mesoporous silica. Additionally, no furfural was detected along the aqueous-phase reaction, evidencing that no remote surface acid sites were playing a sole role. It was suggested that direct highly chemoselective conversion of xylose to furfuryl alcohol takes place on vicinal acid–metal surface sites. Finally, the hybrid catalysts were found to be stable regarding their mesostructure framework upon aqueous-phase processing but acid groups resistance to leaching is still the major challenge for one-pot conversion.

Organic–Inorganic Hybrid Metal Phosphonates as Recyclable Heterogeneous Catalysts

AbstractSuccessful incorporation of a suitable organic moiety in a porous inorganic metal phosphate network can not only make the corresponding organic–inorganic framework more flexible and robust, but it introduces more hydrophobicity at the surface of the resulting nanostructured material, which is highly desirable for their catalytic application in liquid‐phase chemical transformations. Following the success of organic–inorganic hybrid mesoporous silicas, a wide range of analogous hybrid metal phosphonates have been designed. This has opened up a wide diversity of open framework porous nanomaterials, which show excellent catalytic activities in many organic transformations that are not possible with their corresponding inorganic counterparts. Here, we have summarized the recent developments in designing organic–inorganic hybrid porous metal phosphonates in this brief review with a special emphasis on their catalytic potential in liquid‐phase organic transformations.

Host–guest-recognition-based polymer brush-functionalized mesoporous silica nanoparticles loaded with conjugated polymers: A facile FRET-based ratiometric probe for Hg2+

This article reports a new strategy for constructing a fluorescence resonance energy transfer (FRET) based ratiometric sensor for Hg2+ detection with organic-inorganic hybrid mesoporous silica nanoparticles (MSNs) as the scaffolds. The fluorescent conjugated polymer of poly(p-phenylenevinylene) (PPV) as the donor is encapsulated into the MSNs and a spirolactam rhodamine-linked adamantane (AD-SRhB) as mercury ion-recognition element is introduced to cyclodextrin (CD) functionalized polymer brush on the shell of MSNs via the host–guest interaction. Upon the addition of Hg2+, the rhodamine spirocyclic ring opens, and the fluorescence (578 nm) of rhodamine is observed due to the FRET. This novel nanosensor can selectively detect Hg2+ ions with a detection limit of 4.2 μM. On the other hand, compared with pure AD-SRhB as probe, the novel ion probe fabricated by us can selectively detect Hg2+ from other correlative metal ions, especially Fe3+ and Al3+.

Improved dielectric and mechanical properties of silica/epoxy resin nanocomposites prepared with a novel organic–inorganic hybrid mesoporous silica: POSS–MPS

The novel organic–inorganic particles (denoted POSS–MPS) were synthesized by the reaction of amino-functionalized mesoporous silica (NH2-MPS) with a wormhole framework structure and glycidyl polyhedral oligomeric silsesquioxane (G-POSS), and were employed as reinforcing agents to prepare POSS–MPS/epoxy resin (EP) nanocomposites. The retaining mesoporous structure of POSS–MPS was verified by TEM and N2 adsorption–desorption. The excellent improvement in dielectric properties, thermal properties and mechanical properties of the POSS–MPS/EP nanocomposites is ascribed to increase of voids volume and reinforcement of interfacial interaction between organic and inorganic phase in the composites. The POSS–MPS/EP nanocomposites containing 5wt% of POSS–MPS showed a lower dielectric constant (κ=3.66) and loss factor (tanδ=0.017) in comparison to pristine EP with the value of 4.03 and 0.031, respectively. Moreover, the composites exhibited 23.8%, 43.5%, 159.8% and 59.8% enhancement in tensile strength, tensile modulus, elongation at break and glass transmission temperature (Tg) in comparison to pristine EP, respectively. The results manifested that introduction of POSS–MPS improved the mechanical properties, heat resistance and dielectric properties of EP.

Kinetic and equilibrium studies of lead(II) adsorption from aqueous media by KIT-6 mesoporous silica functionalized with –COOH

Abstract An organic–inorganic hybrid mesoporous silica was synthesized via post-grafting of KIT-6 with 4-(triethoxysilyl)butyronitrile. All samples were characterized using their N2 adsorption–desorption isotherms, XRD, FT–IR, TEM, SEM, and PT. The adsorption potential of this material for removing Pb(II) from aqueous solutions was investigated via the batch technique, and the effects of pH and contact time were studied. Experimental data showed that the maximum Pb(II) adsorption, 76%, occurred in the pH range around 6. The adsorption equilibrium was reached within 40 min for 10 wt.%COOH/KIT-6. The adsorption data were fitted using the Langmuir and Freundlich isotherms, and the obtained modeling equilibrium adsorption data suggested that the 10 wt.%COOH/KIT-6 sample contained homogeneous adsorption sites that fit the Langmuir adsorption model well. The pseudo-second-order model described well the 10 wt.%COOH/KIT-6 adsorption process. The desorption and regeneration experiments indicated that ≈95% of the metal desorbed and the adsorbent could be regenerated via an acid treatment without altering its properties.

The relationship between the hydrophobic capacity and extraction efficiency of organic–inorganic hybrid mesoporous silicas for the determination of dibutyl phthalate by SPME–HPLC

Three kinds of organofunctionalized mesoporous silicas, including methyl-MCM-41, propyl-MCM-41 and octyl-MCM-41, were synthesized via one-step co-condensation and for the first time employed as the coatings of solid-phase microextraction fibers coupled with HPLC to extract dibutyl phthalate (DBP). The samples were characterized by fourier transform infrared, small-angle X-ray diffractometer, transmission electron microscope, thermogravimetry analysis and N2 adsorption–desorption. The results showed that the organofunctionalized mesoporous silicas still preserve a desirable two-dimensional P6mm hexagonal structure with large pore volume, good thermal stability and strong hydrophobicity after introducing alkyl groups of various carbon chains to the framework of MCM-41. When the concentration of DBP in standard solution is 1.0 × 10−9 mol L−1, the extraction efficiency of octyl-MCM-41, propyl-MCM-41 and methyl-MCM-41 is 5.7, 4.6 and 4.1 times higher than that of the pure MCM-41, respectively.

Multifunctional Periodic Mesoporous Organosilicas for Biomolecule Recognition, Biomedical Applications in Cancer Therapy, and Metal Adsorption

AbstractThis paper reports a new approach towards the construction of a multifunctional periodic mesoporous organosilica (PMO), which integrates a range of advantages, such as mesoporous structural order, selective nucleobase‐recognition properties, stimuli‐responsive site‐specific delivery of anticancer agents to cancer tissues, and Cu2+ adsorption, into a single entity. First, the appropriate organic‐functional‐receptor precursor was synthesized by a chemical process and used to fabricate a multifunctional pyridine‐containing PMO material (DMPy‐PMO) by a hydrolysis and condensation route. The designed organic–inorganic hybrid mesoporous silica chemosensor showed an intrinsic selective recognition of nucleobase, specifically thymidine, through multipoint hydrogen‐bonding interactions with suitably arrayed receptor sites loaded into the rigid silica framework. An in vitro cytotoxicity test showed that the designed chemosensor materials have good biocompatibility and, therefore, could be promising candidates for the delivery of a range of therapeutic agents. Confocal laser scanning microscopy (CLSM) confirmed that the material can be internalized effectively by cancer cells (MCF‐7 cells). In addition, the DMPy‐PMOs showed efficient Cu2+ ion removal capacity at pH 5.0 with significantly high levels of adsorption (0.95 mmol g–1). These results suggest that the prepared multifunctional PMO hybrid has potential use as a smart material for a range of applications, such as biomolecule recognition, biomedical applications, and as an efficient adsorbent for the removal of metal ions.

Synthesis of a novel organic-inorganic hybrid mesoporous silica and its flame retardancy application in PC/ABS

In this paper, a novel hybrid organic–inorganic mesoporous silica was synthesized through co-condensation of vinyltriethoxysilane (VTES) and tetraethyl orthosilicate (TEOS) in the presence of poly(ethylene glycol)-B-poly(propylene glycol)-B-poly(ethylene glycol) (P123) surfactants, followed by DOPO modification via the reaction between vinyl groups and P–H bond in DOPO. The mesoscopic order and pore structure of the hybrid mesoporous silica was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD) and N2 isothermal sorption. The effect of DOPO-grafted hybrid mesoporous silica (DM) and triphenyl phosphate (TPP) on the fire retardancy in polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) was examined by limiting oxygen index (LOI), UL-94 test, thermalgravity analysis (TGA) and cone calorimeter. Composite PC/ABS with loading of 2 wt% DM and 6 wt% TPP reached LOI value of 28% and V0 rating in UL-94 test. Present high residual weight in TGA and low heat release rate (HRR) in the cone calorimeter. It also indicated that DM is a synergistic agent with TPP, which improved the thermal stability and promoted the system giving dense char layer at high temperature.

Pb (II) removal from aqueous media by EDTA-modified mesoporous silica SBA-15

An organic–inorganic hybrid mesoporous silica material was synthesized by two-step post-grafting method of SBA-15 with 3-aminopropyltrimethoxy-silane (APTES) and thionyl dichloride (SOCl2) activated ethylenediaminetetraacetic acid (EDTA) in sequence and measured by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), elemental analysis (EA), transmission electron microscopy (TEM), nitrogen (N2) adsorption–desorption analysis and back titration. The material was found having the beneficial properties of mesoporous silica SBA-15 and EDTA. Adsorption potential of the material for Pb (II) removal from aqueous solution was investigated by varying experimental conditions such as pH, contact time and initial metal concentration. The removal efficiency of Pb2+ was high under studied experimental conditions. The adsorption equilibrium could be reached within 20min and the kinetic data were fitted well by pseudo-second-order and intraparticle diffusion model. The adsorbent exhibited a favorable performance and its maximum adsorption capacity calculated by the Langmuir model was 273.2mgg−1. Recycling experiments showed the adsorbent could be regenerated by acid treatment without altering its properties. The chemical states of the elements involved in the adsorption were analyzed by X-ray photoelectron spectroscopy (XPS). The results demonstrated that the adsorption mechanism of the material involved Na Pb ion-exchange and carboxyl group dominated surface complexation.

Selective adsorption of bisphenol A by organic–inorganic hybrid mesoporous silicas

Organic–inorganic hybrid mesoporous material (Ph-MS) was synthesized by co-condensation of phenyltriethoxysilane and tetraethoxysilane. Ph-MS, which had pore size of 0.96 nm and surface area of 750 m 2/g, exhibited mesoscopic orderness and suitable textural properties to act as a potential adsorbent for bisphenol A (BPA), which is one of the endocrine disrupting chemicals. Ph-MS adsorbed most amount of BPA faster than powder activated carbon (PAC), and the kinetic adsorption data for Ph-MS was fitted well with the pseudo-second-order kinetic model. Maximum adsorption capacities of adsorbents were estimated from isotherm data using Langmuir model. Ph-MS exhibited high adsorption affinity to BPA showing large adsorption capacity of 351 mg/g, while showing little adsorption affinity to phenol (40 mg/g). PAC, which is one of the general adsorbents for organic compounds, showed large adsorption capacity for both BPA (337 mg/g) and phenol (253 mg/g). Adsorption selectivity of Ph-MS, defined as a relative equilibrium distribution coefficient, K RD, for BPA against phenol, was at least 5 times larger than that of PAC, showing high adsorption selectivity for BPA. The selective adsorption behavior of Ph-MS was discussed using the results of material characterizations including X-ray diffraction, N 2 adsorption/desorption measurements, and Fourier transform infrared spectroscopy, and the results of adsorption experiments.

Task-specific basic ionic liquid immobilized on mesoporous silicas: Efficient and reusable catalysts for Knoevenagel condensation in aqueous media

N-(3-aminopropyl), N(3)-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium bromide hydrobromide was prepared and successively grafted onto mesoporous silicas of MCM-41 and SBA-15. Finally, the protonated amine groups in the resultant organic–inorganic hybrid mesoporous silicas were neutralized by treating with potassium bicarbonate, leading to the immobilized basic amino-containing task-specific ionic liquids (TSILs). Using Knoevenagel condensation as test reaction, the immobilized basic TSILs showed higher efficiency (particularly reusability) than that of similar pure basic TSIL of N-(3-aminopropyl), N(3)-(methyl)-imidazolium tetrafluoroborate or amino-functionalized mesoporous silicas in aqueous media. Much higher catalytic performance of the immobilized basic TSILs, as compared with the pure basic TSIL, could be due to the depressed reaction between amine groups and the hydrogen at C2 of imidazolium derivative cations in the immobilized basic TSILs and to the acid–base cooperativity between the silanols on the pore surface of the siliceous supports and amine groups. On the other hand, that amine groups nucleophilically attack the Si O Si bonds on the pore surface was suppressed due to steric hindrance resulted from the existence of dihydroimidazolium cations in the organic structure of the immobilized basic TSILs, leading to low leaching level of the active species in the immobilized TSILs during the reuse process. As such, the immobilized basic TSILs showed much better reusability in comparison with the amino-functionalized mesoporous silicas.

A fluorophore grafted 2D-hexagonal mesoporous organosilica: Excellent ion-exchanger for the removal of heavy metal ions from wastewater

Highly ordered 2D-hexagonal luminescent organic–inorganic hybrid mesoporous silica (LHMS-2) containing a fluorophore inside the pore walls has been synthesized hydrothermally by using a non-ionic triblock co-polymer surfactant F127 as template under strongly acidic synthesis condition. XRD and HR TEM image analyses suggest the formation of highly ordered 2D-hexagonal mesophase from a mixture of diimine organosilica and tetraethyl orthosilicate (TEOS) precursors. 13C CP MAS, 29Si MAS NMR, UV–visible absorption and PL spectroscopic data suggests the incorporation of bridging organic diimine fluorophore in the solid mesoporous material. N2 sorption data indicates high BET surface area together with type IV isotherm, characteristics of well-defined mesopores for this material. This fluorophore grafted mesoporous material shows very strong affinity for metal cations like Fe3+, Zn2+, Cd2+ and Hg2+, and thus can be very efficiently utilized for the removal of these heavy metal ions from wastewater.

Epoxidation of styrene over gold nanoparticles supported on organic–inorganic hybrid mesoporous silicas with aqueous hydrogen peroxide

A series of S-containing organic–inorganic hybrid mesoporous silicas were synthesized and used as supports for the fabrication of supported gold nanoparticle catalysts. It was found that the location and structure of organic moieties in these mesostructures played a crucial role in the dispersion level of gold nanoparticles, and thus, had a significant effect on the catalytic performance. Under optimum conditions, the gold nanoparticles supported on a periodic mesoporous organosilica with bridging disulfide-ionic liquid moieties showed excellent catalytic performance and reusability in epoxidation of styrene in the presence of H 2O 2-acetonitrile. Moreover, whole epoxidation process and role of gold nanoparticles were proposed.

Enhanced accumulation and visible light-assisted degradation of azo dyes in poly(allylamine hydrochloride)-modified mesoporous silica spheres

A new route for the economic and efficient treatment of azo dye pollutants is reported, in which surface-modified organic–inorganic hybrid mesoporous silica (MS) spheres were chosen as microreactors for the accumulation and subsequent photodegradation of pollutants in defined regions. The surface-modified silica materials were prepared by anchoring the polycationic species such as poly(allylamine hydrochloride) on MS spheres via a simple wet impregnation method. The as-synthesized spheres with well-defined porous structures exhibited 15 times of accumulating capacity for orange II and Congo red compared to that of the pure MS spheres. Diffuse reflectance UV–vis spectroscopy and confocal laser scanning microscopy demonstrated that the accumulated orange II and CR in defined MS spheres were rapidly degraded in the presence of Fenton reagent under visible radiation. Kinetics analysis in recycling degradation showed that the as-synthesized materials might be utilized as environment-friendly preconcentrators/microreactors for the remediation of dye wastewater.

Preparation and characterization of different alkyl-modified SBA-15 by a single-step synthesis

Organic–inorganic hybrid mesoporous silicas of SBA-15 with different sizes of organic functionalities of methyl, propyl, or octyl were prepared by the single-step co-condensation of inexpensive tetraethyl orthosilicate and organotrialkoxysilane using Pluronic P123 as a templating agent under acidic conditions. Samples were characterized by FT-IR, XRD, TEM and SEM. The results show that different alkyl groups are attached covalently to the pore wall of SBA-15 after modification, respectively. The functionalized materials still preserve a desirable ordered two-dimensional P6mm hexagonal structure although the organotrialkoxysilane molar ratio is as high as 20%.