Ethane-bridged Periodic Mesoporous Organosilicas Research Articles

Antibacterial and anticancer activities of asymmetric lollipop-like mesoporous silica nanoparticles loaded with curcumin and gentamicin sulfate

Asymmetric mesoporous silica nanoparticles with anisotropic geometry and dual-compartments are highly desired for loading and release of dual-drugs in separated storage spaces. In this study, an asymmetric lollipop-like mesoporous silica nanoparticle Fe3O4@SiO2&EPMO (EPMO = ethane bridged periodic mesoporous organosilica) was successfully developed via an anisotropic epitaxial growth strategy. The asymmetric nanoparticles show a uniform lollipop shape with a head of spherical Fe3O4@SiO2 core-shell that is 200 nm in diameter and a tail of EPMO nanorods with a length of ∼90 nm, and a specific surface area of ∼650.3 m2 g−1. Most importantly, the asymmetric nanoparticles possess the unique dual independent (hydrophilic/hydrophobic) spaces with good loading capacities and are significantly more efficient for cancer cell killing than pure drug based on in vitro studies. Additionally, the dual-drug-loaded nanoparticles exhibited excellent antibacterial activity.

Periodic mesoporous organosilicas as porous matrix for heterogeneous lyophobic systems

Periodic mesoporous organosilicas (PMO) have been studied for the first time as a porous matrix for heterogeneous lyophobic systems (HLS) for absorption and storage of mechanical energy by high pressure intrusion-extrusion of electrolyte solutions. It has been shown that the intrusion of LiCl aqueous solutions in ethane-bridged PMO material is irreversible that corresponds to a bumper behavior. The intrusion pressure increases strongly with the salt concentration - from 13 MPa for 5 M LiCl aqueous solution to 37 MPa for 20 M one. Such a pressure rise of 2.8 times is the highest observed for HLS based on mesoporous materials. Due to high intruded volume (0.63–0.72 mL/g) specific absorbed energy achieves 27 J/g, which is close to the best values ever obtained for HLS based on zeosils and mesoporous silica. The characterization shows that after the intrusion-extrusion experiments the ordered pore arrangement largely stays intact, but a slight increase of the mesopore volume is observed.

Uniform and ordered periodic mesoporous organosilica thin films by a facile solution growth approach

We demonstrate a novel solution growth method for synthesis of uniform and ordered periodic mesoporous organosilica (PMO) thin films on substrate. The approach is simple and facile, in which a substrate is immersed into a solution containing 1,2-bis(triethoxysilyl)ethane (BTSE) precursor, cetyltrimethylammonium bromide (CTAB) surfactant template, ammonia catalyst, ethanol, and decane. The precursors are hydrolyzed, cross-linked by ammonia catalyst, and assembled with the surfactant on the substrate to form highly ordered hexagonal mesostructures. The obtained mesoporous silica films possess substrate-size-dependent dimension, uniform and tunable thickness (30–100 nm), and ethane group incorporated frameworks. The obtained PMO films have been characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and grazing incidence small-angle X-ray scattering (GISAXS). The film thickness can be easily controlled by adjusting the reaction temperature. A formation mechanism of the ethane-bridged PMO films via CTAB directed sol–gel process is further proposed.

Degradation-Restructuring Induced Anisotropic Epitaxial Growth for Fabrication of Asymmetric Diblock and Triblock Mesoporous Nanocomposites.

A novel degradation-restructuring induced anisotropic epitaxial growth strategy is demonstrated for the synthesis of uniform 1D diblock and triblock silica mesoporous asymmetric nanorods with controllable rod length (50 nm to 2 µm) and very high surface area of 1200 m2 g-1 . The asymmetric diblock mesoporous silica nanocomposites are composed of a 1D mesoporous organosilicate nanorod with highly ordered hexagonal mesostructure, and a closely connected dense SiO2 nanosphere located only on one side of the nanorods. Furthermore, the triblock mesoporous silica nanocomposites constituted by a cubic mesostructured nanocube, a nanosphere with radial mesopores, and a hexagonal mesostructured nanorod can also be fabricated with the anisotropic growth of mesopores. Owing to the ultrahigh surface area, unique 1D mesochannels, and functionality asymmetry, the obtained match-like asymmetric Au-NR@SiO2 &EPMO (EPMO = ethane bridged periodic mesoporous organosilica) mesoporous nanorods can be used as an ideal nanocarrier for the near-infrared photothermal triggered controllable releasing of drug molecules.

Quinine Derivative Bonded the Hybrid Mesoporous Silicas Chiral Stationary Phase: Preparation and Application in Liquid Chromatography

AbstractA novel chiral stationary phase (QN‐APEPMOs) was synthesized by immobilizing quinine derivative (QN) onto spherical ammoniapropyl‐functionalized ethane‐bridged periodic mesoporous organosilicas (APEPMOs). The mesoporous material was prepared by a one‐step co‐condensation of 1,2‐bis (triethoxysilyl) ethane (BTSE) and 3‐ammoniapropyl triethoxysilane (KH‐550) using cetyltrimethyl‐ammoniumchlorine (C18TACl) as a template with the aid of ethanol (co‐solvent) in basic medium. And O‐9‐(tert‐butyl carbamoyl) quinine derivative was immobilized on APEPMOs particles through the vinylic double bond. All of the products were characterized. The results showed that APEPMOs were perfect substrates for chiral stationary phase (CSP) and quinine moieties have been successfully immobilized onto the silica gel. To evaluate the chiral discrimination ability of the synthesized CSP, some analytes have been investigated on QN‐APEPMOs in high performance liquid chromatography (RP‐HPLC) in reversed phase. Three acidic compounds were baseline separated. The results demonstrated that QN‐APEPMOs had high selectivity for acidic compounds such as: carboxylic and sulfonic acids. And the reproducibility of the chiral column was good, while the stability was not very good.

A Facile Multi-interface Transformation Approach to Monodisperse Multiple-Shelled Periodic Mesoporous Organosilica Hollow Spheres.

The synthesis of well-defined and complex hollow structures via a simple method is still a major challenge. In this work, a facile and controllable "multi-interface transformation" approach for preparation of monodisperse multi-shelled periodic mesoporous organosilica (PMO) hollow spheres has been established by a one-step hydrothermal treatment of successively grown organosilica particles. The multi-shelled PMO hollow spheres have inorganic-organic hybrid frameworks, controllable number (1-4) of shells, high surface area (∼805 m(2)/g), accessible ordered mesochannels (∼3.2 nm), large pore volume (1.0 cm(3)/g), and uniform and tunable diameter (300-550 nm), chamber size (4-54 nm), and shell thickness (10-30 nm). In addition, various organic groups (alkyl, aromatic, and heteroelement fragments) are successfully incorporated into the multi-shelled PMO hollow spheres by successively adding different bridged organosilica precursors. Notably, the distribution of different kinds of organic groups in the multi-shelled PMO hollow spheres can be precisely controlled, showing great potential for future applications. We propose that the formation of the multi-shelled PMO hollow structures is ascribed to the creation of multiple highly cross-linked organosilica interfaces, providing a new and interesting fundamental principle for PMO materials. Due to their unique structure and frameworks, triple-shelled ethane-bridged PMO hollow spheres were successfully loaded with an anti-cancer drug doxorubicin and perfluoropentane gas, which present excellent effects in the killing of cancer cells and ultrasound imaging. It is expected that the multi-interface transformation strategy provides a simple, controllable, versatile, and template-free method for preparation of various multifunctional PMOs for different applications.

Clickable Periodic Mesoporous Organosilicas: Synthesis, Click Reactions, and Adsorption of Antibiotics

Pharmaceutical antibiotics are not easily removed from water by conventional water-treatment technologies and have been recognized as new emerging pollutants. Herein, we report the synthesis of clickable azido periodic mesoporous organosilicas (PMOs) and their use as adsorbents for the adsorption of antibiotics. Ethane-bridged PMOs, functionalized with azido groups at different densities, were synthesized by the co-condensation of 1,2-bis(trimethoxysilyl)ethane (BTME) and 3-azidopropyltrimethoxysilane (AzPTMS), in the presence of nonionic-surfactant triblock-copolymer P123, in an acidic medium. Four different alkynes were conjugated to azide-terminated PMOs by means of an efficient click reaction. The clicked PMOs showed improved adsorption capacity (241 μg g(-1)) for antibiotics (ciprofloxacin hydrochloride) compared with azido-functionalized PMOs because of the enhanced π-π stacking interactions. These results indicate that click reactions can introduce multifunctional groups onto PMOs, thus demonstrating the great potential of PMOs for environmental applications.

Influence of Synthesis Conditions on Properties of Ethane-Bridged Periodic Mesoporous Organosilica Materials as Revealed by Spin-Probe EPR

A thorough investigation of the formation mechanism and surface properties of periodic mesoporous organosilicas (PMOs) is of crucial importance for further tuning and improving of the structural characteristics and applications of these promising meso-structured materials. In the present paper, the effects of the synthesis conditions on the properties of ethane-bridged PMOs were studied by means of spin-probe electron paramagnetic resonance (EPR) spectroscopy complemented with standard characterization techniques for porous materials. When spin probes were dissolved in the synthesis mixture, the influence of the precursor type on the formation kinetics of ethane-bridged PMOs could be tested. The use of the precursor 1,2-(tris(triethoxysilyl)ethane instead of bis(trimethoxysilyl)-ethane significantly slows the pore formation, leading to materials with larger pore diameters. Furthermore, different spin probes with varying sizes and polarities were adsorbed onto two types of ethane-bridged PMOs synthesized a...

Structural and Optical Properties of Titanium Functionalized Periodic Mesostructured Organosilica Framework via Evaporation-Induced Self-Assembly Method

We describe an evaporation-induced self-assembly method for incorporating Ti into framework of ethane-bridged periodic mesoporous organosilica (PMO). The X-ray diffraction (XRD), transmission electron microscopy (TEM), solid-state 29Si and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and UV-vis spectroscopy were used to elucidate the optical and structural properties of Ti-incorporated PMO materials. The degree of mesopore ordering and the structural properties were found to be dependent on the loading of Ti into the framework of PMO materials, as confirmed by XRD, and surface structural properties. UV-vis spectra also support the incorporation of Ti into framework of PMO. TEM analyses suggested the formation of mesopores for the pure PMO and Ti-incorporated PMO samples. The solid-state NMR and FT-IR spectra have confirmed the presence of organic fragment in the final PMO framework.

Highly Carboxylic‐Acid‐Functionalized Ethane‐Bridged Periodic Mesoporous Organosilicas: Synthesis, Characterization, and Adsorption Properties

Functionalization of periodic mesoporous organosilicas (PMOs) with high loadings of pendant organic groups to form bifunctional PMOs with ordered mesostructures remains a challenging objective. Herein, we report that well-ordered ethane-bridged PMOs functionalized with exceptionally high loadings of pendant carboxylic acid groups (up to 80 mol % based on silica) were synthesized by the co-condensation of 1,4-bis(trimethoxysilyl)ethane (BTME) and carboxyethylsilanetriol sodium salt (CES) with Pluronic P123 as the template and KCl as an additive under acidic conditions. The bifunctional materials were characterized by using a variety of techniques, including powder X-ray diffraction, nitrogen-adsorption/desorption, TEM, and solid-state (13)C and (29)Si NMR spectroscopy. Zeta-potential measurements showed that the surface negative charges increased with increasing the CES content. This property makes them potential candidates for applications in drug adsorption. The excellent adsorption capacity of these bifunctional PMOs towards an anticancer drug (doxorubicin) was also demonstrated.

Hydrothermally Stable Periodic Mesoporous Ethane-Silica and Bimodal Mesoporous Nanostructures

We report the hydrothermally stable organized periodic mesoporous organosilicas (PMOs) and bimodal mesoporous structures by using mixed templates of oligomeric alkyl-ethylene oxide and ionic surfactants under basic conditions. Oligomeric alkyl-ethylene oxide surfactant [(Polyoxyethylene (2) cetyl ether, structure is C16H33(OCH2CH2)nOH, n-2, hereafter known as B52) and ionic surfactant (cethyltrimethylammonium bromide (CTAB)) templating systems form mixed micelles that self-assemble into well-ordered hexagonal and bimodal mesostructures. The X-ray diffraction (XRD), transmission electron microscopy (TEM), BET, NMR and hydrothermal study have been used to investigate the effects of B52 on the formation of various PMOs. It is found that surface structural properties of mesostructures largely depend on the concentration of the B52 in the surfactant solution. The addition of B52 in the surfactant solution is not only improves mesostructural ordering and also enables to produces mesostructures with tuned surface structural properties. The final PMO structure shows good hydrothermal stability and can withstand for 72 h in boiling water, due to the hydrophobic pore wall chemistry in ethane-bridged PMO framework (triple bond Si-CH2-CH2-Si triple bond) and relatively more condensed framework such T3 supported by NMR spectrum. So, the lacking affinity for water through the favorable hydrophobic framework chemistry enhances the hydrothermal stability.

Self-assembled highly ordered ethane-bridged periodic mesoporous organosilica and its application in HPLC

Monodisperse spherical periodic mesoporous organosilicas (PMOs) with ethane integrated in the framework were synthesized and their application as stationary phase for chromatographic separation is demonstrated. The ethane-PMOs were prepared by condensation of 1,2-bis(triethoxysilyl)ethane (BTSE) in basic condition using octadecyltrimethylammonium chloride (C(18)TMACl) as template and ethanol as co-solvent. The morphology and mesoporous structure of ethane-PMOs were controlled under different concentrations of sodium hydroxide (NaOH) and EtOH. The results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), nitrogen sorption measurement, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis showed that ethane-PMOs have spherical morphology, uniform particle distribution, highly ordered pore structure, high surface area and narrow pore-size distribution. The column packed with these materials exhibits good permeability, high chemical stability and good selectivity of mixtures of aromatic hydrocarbons in normal phase high-performance liquid chromatography (HPLC).

Carboxylic groups in mesoporous silica and ethane-bridged organosilica: effect of the surface on the reactivity

Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15.

Aminopropyl-functionalized ethane-bridged periodic mesoporous organosilica spheres: Preparation and application in liquid chromatography

A synthetic approach for synthesizing spherical aminopropyl-functionalized ethane-bridged periodic mesoporous organosilicas (APEPMOs) is reported. The mesoporous material was prepared by a one-step co-condensation of 1,2-bis(triethoxysilyl)ethane (BTSE) and 3-aminopropyltriethoxysilane (APTES) using cetyltrimethylammonium chlorine (C18TACl) as a template with the aid of a co-solvent (methanol) in basic medium. The APEPMOs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), nitrogen sorption measurement, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. It was shown that this material exhibited spherical morphology, ordered cubic mesostructure and good mechanical strength. The APEPMOs were tested as a potential stationary phase for liquid chromatography (LC) because the column exhibited reduced back pressure. Moreover, they exhibited good chemical stability in basic mobile phase, which can be ascribed to the ethane groups in the mesoporous framework.

Covalent Incorporation of Ethylenediamine Ligands in the Framework of Periodic Mesoporous Organosilica Nanostructure

The covalent incorporation of ethylenediamine ligands in the framework of periodic mesoporous organosilica (PMO) nanostructure via mixed surfactants self-assembly process has been described. Propyl ethylenediamine group was employed to functionalize the pore channels of ethane-bridged PMO by co-condensation of 1,2-Bis(triethoxysilyl)ethane (BTSE) and (trimethoxysilyl)propyl]ethylenediamine (EDA-TES) in the presence of mixed surfactants (cetyltrimethylammonium bromide and fluorosurfactant (FSN100)) under basic conditions. In order to elucidate the effect of EDA-TES concentration on their mesoscopic organization and pore structure of the final PMO structures, the morphology of PMO nanostructures was investigated in detail by using X-ray diffraction (XRD), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption. FTIR and NMR results have confirmed that ethane bridging groups in the final framework have not been cleaved and EDA-TES functions have been covalently anchored to the pore wall of PMO. The structural regularity of mesopore decreases with increasing concentration of EDA-TES in the initial mixtures except for the samples with 15 and 30 wt% EDA-TES concentrations, which exhibits a highly ordered two-dimensional hexagonal symmetry, supported by XRD patterns and TEM. Overall, the increase of EDA-TES contents results in the decreased surface area and total pore volume, indicating that the framework of PMO is covalently functionalized with EDA-TES function.

Ordered and Hydrothermally Stable Cubic Periodic Mesoporous Organosilicas with SBA-1 Mesostructures: Synthesis, Characterization, Solid-State NMR Spectroscopy, and DFT Calculations

Periodic mesoporous organosilicas (PMOs) based on the cubic SBA-1 mesostructure (Pm3n mesophase) were synthesized by co-condensation of tetraethoxysilane (TEOS) and 1,2-bis(triethoxysilyl)ethane (BTEE) under acidic conditions using cetyltriethylammonium bromide (CTEABr) as a structure-directing agent. The ethane-bridged PMO materials thus obtained were characterized by powder X-ray diffraction (XRD), solid-state 13C and 29Si NMR spectroscopy, thermogravimetric analysis (TGA), and nitrogen sorption measurements. The maximum BTEE contents that can be incorporated into the pore wall without degrading the Pm3n mesostructure were up to 60% (based on silica). The resulting materials were hydrothermally stable up to 120 h in boiling water with only a slight decrease in their structural properties, whereas the structure of the pure silica counterpart SBA-1 material was completely collapsed after such treatment. The presence of the ethane groups in the mesoporous wall led to a more hydrophobic environment and thus enhancement of hydrothermal stability, as revealed by water adsorption. The combined results of 2D 29Si{1H} heteronuclear correlation (HETCOR) NMR and density functional theory calculations suggested that the T3−T2−Q4−Q3 motif could be the favorable framework building unit in PMOs.

Preparation and characterization of periodic mesoporous organosilica terminally functionalized with fluorocarbon groups by a direct synthesis

Fluorocarbon groups were used to modify the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation of 1,2-Bis(triethoxysilyl)ethane (BTESE) and trifluoropropyltrimethoxysilane (TFPTMS) in the presence of Poly(ethylene glycol)-B-Poly(propylene glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The functionalized materials were investigated in detail by means of XRD, TEM, FT-IR, solid-state NMR, and N2 adsorption. The effect of fluorocarbon groups concentration on the mesoscopic order and pore structure of the functionalized materials was also studied. The results show that bridging groups in the framework do not cleave and fluorocarbon groups are attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The samples functionalized with 20% TFPTMS remain desired mesoporous architecture, with a narrow pore size distribution centered at 4.1 nm, a large surface of 834 m2/g and a pore volume of 0.91 cm3g−1, without pronounced change compared to the pure periodic mesoporous organosilica. Unfortunately the functionalized materials become structurally disordered with increasing amount of fluorocarbon groups.

Functionalization of periodic mesoporous organosilica with ureidopropyl groups by a direct synthesis method

Ureidopropyl groups were used to functionalize the pore channels of ethane-bridged periodic mesoporous organosilica by the co-condensation of 1,2-Bis(triethoxysilyl)ethane (BTESE) and ureidopropyltriethoxysilane (UPTES) in the presence of Poly(ethylene glycol)-B-Poly(propylene glycol)-B-Poly(ethylene glycol) (P123) surfactants under acidic conditions. The final materials were investigated in detail by means of XRD, TEM, solid-state NMR, FT-IR and N 2 adsorption, in order to study the effect of ureidopropyl groups concentration on their mesoscopic order and pore structure. The results show that bridging groups in the framework do not cleave and ureidopropyl groups are attached covalently to the pore wall of periodic mesoporous organosilica after functionalization. The mesoscopic order decreases with increasing amount of UPTES except for the sample with 20 mol% UPTES concentration, which exhibits a highly ordered two-dimensional hexagonal symmetry. The surface area and pore size decrease as the concentration of UPTES increases, but the materials with 20 mol% UPTES still preserve a desirable pore structure, with a surface area of 565 m 2/g, a pore volume of 1.1 cm 3/g and a mean pore size of 10.1 nm.

Assembly of hydrothermally stable ethane-bridged periodic mesoporous organosilicas with spherical and wormlike structures

Hydrothermally stable periodic mesoporous organosilicas with spherical as well as wormlike frame structures were synthesised by two different synthesis routes using the silsesquioxane precursor, 1,2-bis (triethoxy silyl) ethane (BTEE) and surfactant octadecyl trimethyl ammonium (ODTA), under basic conditions. The materials were characterized by PXRD, SEM, TEM, N 2 adsorption–desorption, FT-IR, 29Si MAS NMR, 13C CP MAS NMR and TG-DTA techniques. Characterization techniques revealed that the morphology of the hybrid material prepared from pure silsesquioxane precursor resulted in spherical particles while a combination of tetra ethyl orthosilicate and 1,2-bis (triethoxy silyl) ethane (90:10 ratio) resulted in materials having wormlike structures. Hydrothermal stability of the hybrid material was evaluated by refluxing the sample under boiling water for various time periods and was compared with that of a periodic mesoporous silica material, Si-MCM-41. Results showed that the hybrid material is stable up to 100 h in boiling water, with the existence of d 100 peak, while the mesopore structure of Si-MCM-41 get destroyed even after a 12 h reflux time. The improved hydrothermal stability of the hybrid material is related to the more hydrophobic environment induced inside the pore channels, due to the presence of integrating ethane groups in the wall channels.

Synthesis and characterization of organic–inorganic hybrid mesoporous silica materials with new templates

1-Hexadecane-3-methylimidazolium bromide and 1-hexadecane-2,3-dimethylimidazolium bromide were used as new templates for the syntheses of periodic mesoporous organosilica (PMO) materials; using these new templates, ethane-bridged PMO materials were successfully synthesized and characterized under basic conditions.