Encapsulation of Coumarin 151 into the mesopores of modified rodlike SBA-15

Dye Coumarin 151 was postgrafted into the rodlike SBA-15 mesoporous materials, which were synthesized by a direct hydrothermal synthesis method and further modified by an organic silane with a terminal amino group. Characterization by powder X-ray diffraction, N₂ adsorption-desorption, transmission electron microscopy, photoluminescence and scanning electron microscopy were carried out. Small-angle X-ray diffraction and N₂ adsorption-desorption characterizations showed that these dye containing materials remained as ordered mesostructures and the pore size was from 6 nm for blank sample to 3.6 nm for postgrafting sample. PL characterization of composite samples exhibited optical properties with different dye concentrations. The characterization showed the existence of Coumarin 151 in the channels of SBA-15 and the composite materials with novel optical properties enabled possible applications in optical sensing and electron acceptors.     

Synthesis of core–shell structured FAU/SBA-15 composite molecular sieves and their performance in catalytic cracking of polystyrene

Abstract

Composite molecular sieves, FAU/SBA-15, having core-shell structure were synthesized. The synthesized composite sieves were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), pyrolysis fourier transform infrared (Py-FTIR) spectroscopy, temperature programmed desorption spectra (NH₃-TPD), UV Raman spectroscopy, nuclear magnetic resonance (NMR) and other techniques. XRD, SEM, TEM, N₂ adsorption-desorption, mass spectrometry, NMR and EDS results showed that the composite molecular sieve contained two pore channels. Py-FTIR results showed that the addition of HY molecular sieves improved the acidity of the composite zeolite. The crystallization mechanism during the growth of FAU/SBA-15 shell was deduced from the influence of crystallization time on the synthesis of FAU/SBA-15 core-shell structured composite molecular sieve. HY dissociated partially in H₂SO₄ solution, and consisted of secondary structural units. This framework structure was more stable than its presence in the isolated form on the same ring or in the absence of Al. Thus it played a guiding role and connected with SBA-15 closely through the Si-O bond. This resulted in the gradual covering of the exterior surface of FAU phase by SBA-15 molecular sieves. The presence of SBA-15 restricted the formation of the other high mass components and increased the selectivity towards ethylbenzene.     

TiO2 supported on rod-like mesoporous silica SBA-15: Preparation, characterization and photocatalytic behaviour

TiO₂ nanoparticles have been successfully incorporated in the pores of mesoporous silica SBA-15 with different morphologies by a wet impregnation method. The composites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) emission spectroscopy, transmission electron microscopy (TEM), N₂-sorption and UV-Vis diffuse reflectance spectroscopy. The photodegradation of methyl orange (MO) was used to study their photocatalytic property. It is indicated that the morphology of SBA-15 had a great influence on the photocatalytic activity of the composites. When TiO₂/SBA-15 composite was prepared by loading TiO₂ nanoparticles on uniform rod-like SBA-15 of 1 μm length, it showed higher photocatalytic degradation rate than that on less regular but much larger SBA-15 support. This difference was rationalized in terms of the homogeneously distributed and shorter channels of rod-like SBA-15, which favored mass transport and improved the efficient utilization of the pore surface.     

Controlled synthesis of semiconductor PbWO4 nanocrystals inside silica SBA-15 materials

A new flexible approach is developed to synthesize PbWO₄ nanoparticles inside the channels of mesoporous silica SBA-15. Mesoporous SBA-15 silica with 7 nm pores was produced by a hydrothermal process and used as a hard template. PbWO₄ nanoparticles were synthesized and incorporated into the mesoporous silicate support in a low-power ultrasonication condition. The as-synthesized samples were characterized by Raman spectroscopy, diffuse reflectance UV–vis spectroscopy (UV–vis), powder X-ray diffraction (XRD), small-angle X-ray diffraction (SAXRD), nitrogen adsorption and transmission electron microscopy (TEM). It was found that PbWO₄ nanoparticles appeared among the channels of SBA-15. Blue shift was observed in UV–vis absorption spectra due to the quantum size effect of PbWO₄ nanoparticles. This preparation method is also capable of synthesis of various semiconductor nanoparticles with controlled size and morphology inside the channels of mesoporous materials.     

Design and synthesis of Alq3-functionalized SBA-15 mesoporous material

A luminescent organic molecule aluminum tris(8-hydroxyquinoline) (Alq₃) has been successfully introduced in the pores of amino-functionalized mesoporous SBA-15 (APS-SBA-15). An obvious blue-shifted photoluminescence (PL) of Alq₃ was observed. In the pores of APS-SBA-15, the Alq₃ organic molecules exhibited efficient and intense PL as monomers and the emission intensities increased with increasing Alq₃ concentration.     

The morphology and size of nanostructured Au in Au/SBA-15 affected by preparation conditions

Template-free mesoporous silica SBA-15 was reacted with TPTAC to generate positively charged functional groups PTA⁺ on the pore surface. Through ion exchange, a uniform distribution of anionic metal complexes on the intrachannel surface of host silica was achieved. In this study, ethanol and water were used as solvent for HAuCl₄ precursor solutions impregnated on SBA-15 mesoporous silica. The solvent used can affect the size and location of the resulting nanoparticles. Large Au nanoparticles (15–43 nm) were found on the as-prepared Au/SBA-15 as observed by PXRD, XAS, UV–vis and TEM. This may have originated through Si–OH reduction of chloroaurate complexes generated in the aqueous solution of HAuCl₄, and such particles were not present when ethanolic solution was used. After NaBH₄ and H₂ reduction, the average size of Au nanoparticles, which was incorporated into the channels of SBA-15, was found to be limited to ≤  7 nm.     

Synthesis,characterization and optical properties of CdS nanoparticles confined in SBA-15

A novel and dexterous in situ method is introduced to load CdS nanocrystals into SBA-15, which uses the acid–base reaction of mercaptoacetic acid with 3-aminopropyltriethoxysilane, the modifier of internal surface of mesoporous materials to facilitate loading of sulfur precursor, followed by adsorption of Cd²⁺ and calcination at 300 °C in N₂ atmosphere for 2 h. XRD, N₂ adsorption–desorption isotherms, HRTEM, EDS, FT-IR, UV–vis absorption spectrum and PL spectrum were used to characterize the composite material. It was found that the CdS nanocrystals were confined in the channel of SBA-15 with an average size of 6 nm. The mesoporous silica-supported CdS composites showed a room temperature photoluminescence property.     

Effect of SBA-15 microporosity on the inserted TiO2 crystal size determined by Raman spectroscopy

The effect of SBA-15 microporosity on the crystal size of TiO₂ was investigated employing SBA-15 materials with high (SBA-15-HM) and low (SBA-15-LM) microporosities (14.2% and 4.7% of microporous volume, respectively). TiO₂ phase was incorporated inside SBA-15 using internal hydrolysis method over a wide range of loadings (7–63 wt%). At all loadings, TiO₂ inside SBA-15 pores was in the form of anatase nanocrystals as found in characteristic Raman spectra. The crystal size of TiO₂ anatase phase was determined by Raman spectroscopy using a correlation between Raman peak position and peak width and TiO₂ crystal size. The correlation was established based on the set of unsupported TiO₂ samples with the crystals size in the range 5–120 nm (BET and XRD). Using this correlation, it was found that the crystal size of TiO₂ inside SBA-15 with high microporosity was lower than inside SBA-15 with low microporosity. This is a direct proof of the effect of wall microporosity on the dispersion of TiO₂ inside SBA-15. Due to the higher TiO₂ dispersion, TiO₂/SBA-15-HM adsorbed more vanadia than TiO₂/SBA-15-LM at the same TiO₂ loadings. As a result, V₂O₅/TiO₂/SBA-15-HM displayed higher activity than V₂O₅/TiO₂/SBA-15-LM in NO SCR with ammonia.     

Template synthesis of boron nitride nanotubes in mesoporous silica SBA-15

Nitride nanotubes (BN-NTs) was synthesized by chemical vapor deposition (CVD) using BCl₃ and NH₃ at relatively low temperature within the channels of mesoporous silica SBA-15. TEM images confirmed the existence of BN-NTs. The BN-NTs were of uniform diameter about 7 nm, which was consistent with the channel diameter of the template SBA-15. Using this approach, it is easy to control the diameter of BN-NTs by adjusting the diameter of the channel of mesoporous silica host.     

Synthesis and characterization of Co–Fe nanoparticles supported on mesoporous silicas

Co–Fe bimetallic samples containing 25 wt% total of metal content were prepared by incipient wetness impregnation of cobalt nitrate and iron nitrate salts over hexagonal mesoporous silica (HMS) and SBA-15 supports. Changes in the textural properties and reduction behavior were compared with monometallic cobalt/iron-based samples. The samples were characterized by N₂ physisorption, X-ray diffraction (XRD), H₂-temperature programmed reduction (TPR), transmission electron microscopy (TEM) and H₂ chemisorption. The amount of incorporated metal was estimated by atomic absorption spectroscopy (AAS). Morphological properties revealed that after introduction of the metal to the SBA-15 support, the specific area, pore volume and pore diameter decreased to a lesser extent for bimetallic samples. XRD measurements detected the formation of Co₃O₄ and CoFe₂O₄ phases for both bimetallic samples. TPR profiles indicated similar behavior for both the bimetallic and monometallic samples. Higher temperatures were observed for the reducibility of Co–Fe/HMS as compared to Co–Fe/SBA-15. Dispersion values of the bimetallic samples were higher than Fe monometallic samples and lower than Co monometallic samples according to hydrogen chemisorption. The particle size distribution of the bimetallic samples estimated by TEM microphotographs showed a smaller fraction of larger size particles for Co–Fe/SBA-15.     

Spaced-amine modified SBA-15: Synthesis and characterization

A novel kind of spaced-amine modified mesoporous silica (SBA-15-NH₂) was synthesized via the Diels-Alder reaction of fumaronitrile and cyclopentadienyl-modified SBA-15 (SBA-15-Cp), followed by the reduction of cyano groups using NaBH₄/I₂ as reductant and Diglyme as solvent. The synthesized materials were characterized by X-ray diffraction (XRD), N₂-sorption, transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR) and thermogravimetric analysis (TGA). The mesostructure was kept well after reaction with fumaronibrile and the reduction of cyano groups. SBA-15-NH₂ has an amine loading of 0.95 mmol NH₂/g and shows high activity, selectivity and reusability in the Knöevenagel condensation of benzaldehyde and malononitrile.     

Enhanced dehydrogenation of nanoscale MgH2 confined by ordered mesoporous silica

Nanoscale MgH₂ was synthesized through loading di-n-butylmagnesium (MgBu₂) solution into the pores of ordered mesoporous silicas (SBA-15) with a pore diameter in a range of 5–10 nm, followed by freeze drying and hydrogenation treatment. The MgBu₂ inside the pore channels of SBA-15 decomposed into MgH₂ upon hydrogenation at 493 K under 6 MPa hydrogen. The nanoconfined MgH₂ exhibited greatly decreased desorption temperature of 540 K, a reduction of 146 K in comparison with that of commercial MgH₂, or 65 K reduction relative to that of MgH₂ obtained from MgBu₂ without confinement. Moreover, lower desorption temperature for the MgH₂ supported by SBA-15 with smaller pore diameter. The improvement on the dehydrogenation properties of MgH₂ was attributed to the nanosizing effect induced by the nanoconfinement of mesoporous silica.     

超临界流体沉积法制备纳米Cu/SBA-15复合材料

采用超临界流体沉积法,以无机盐Cu(NO₃)₂为前驱物,超临界CO₂为溶剂,乙醇为共溶剂,在压力20 MPa左右、温度 50℃ 条件下将Cu(NO₃)₂沉积到SBA-15介孔分子筛的孔道中。反应完成后,用氢气对前驱物进行还原,得到纳米线和纳米颗粒Cu/SBA-15复合材料。用透射电镜(TEM)和X射线衍射(XRD)对Cu/SBA-15复合材料进行表征,发现在SBA-15孔道内部填充了Cu 纳米线和分散的Cu 纳米颗粒。Cu 纳米线平均直径为6nm,长度为几纳米到几微米,并且沿着孔道生长,能够随着孔道发生弯曲;Cu纳米粒子的平均尺寸为3.2nm,高度分散。同时,实验中还发现,通过控制反应条件,能够控制复合材料中纳米结构的形貌(纳米线或者纳米颗粒) 。实验结果表明,超临界流体沉积法是制备担载型复合材料的有效方法。选择合适的共溶剂可以用超临界CO₂溶解无机盐,并可以通过控制反应条件,控制所制备的复合材料中纳米结构的形貌。     

Synthesis of mixed-phase uniformly infiltrated SBA-3-like in SBA-15 bimodal mesoporous silica from rice husk ash

The mixed-phase bimodal mesoporous silicas (BMS) were simply synthesized via sol-gel technique using rice husk ash-derived sodium silicate as a silica source, and Pluronic P123 and cetyltrimethyl ammonium bromide (CTAB) as the pore structure-directing agents. The gel solution composition in the synthesis process was based on SiO₂:Pluronic P123:CTAB:HCl:H₂O molar ratio of 1:0.088:0.088:4:200. The effect of mixing sequences of starting materials on BMS structures was investigated. The phase separation among SBA-15, SBA-3-like porous silica and xerogel was found when the gel solutions of SBA-15 and SBA-3-like were prepared separately in the primary stage, whereas the mixed-phase uniformly infiltrated SBA-3-like in SBA-15 bimodal porous silica was successfully synthesized when CTAB was added into the SBA-15 gel solution and the secondary micelle structure was formed inside the primary SBA-15 framework.     

Amine and thiol functionalization of SBA-15 nanoparticles for highly efficient adsorption of sulforaphane

This study presents a novel material for highly efficient adsorption of sulforaphane based on SBA-15. The SBA-15 nanoparticles were synthesized using natural silica by hydrothermal method and functionalized with thiol and amine groups by the post-synthesis grafting procedure. All adsorbents were characterized by various techniques including BET, LAXRD, FT-IR, FE-SEM, and CHNS. The batch adsorption experiments revealed that the adsorption efficiency of SBA-15 for sulforaphane can be mainly influenced by the introduction of functional groups and the best adsorption performance was observed for amine-functionalized SBA-15 (SBA-15-NH₂) compared to pure SBA-15 and thiol-functionalized SBA-15 (SBA-15-SH) with the highest adsorption efficiency of about 97%. Preliminary adsorption studies of sulforaphane onto SBA-15-NH₂ were performed in aqueous solutions with different pH values and various organic solvents. Also, the effects of adsorbent dosage, contact time, and initial sulforaphane concentration on sulforaphane adsorption using SBA-15-NH₂ were studied. Langmuir and Redlich-Peterson isotherm models were the best-fitting models for the experimental data, followed by Temkin, Freundlich, and Dubinin-Radushkevich models. The adsorption process could be well described by the pseudo-first-order kinetic model based on kinetic parameters, correlation coefficient, and error functions. Meanwhile, the intra-particle diffusion model showed a multi-linear plot with three steps demonstrating slow diffusion into mesopores as a rate-limiting step.     

Synthesis and characterization of a novel neighboring dicarboxyl-modified SBA-15 via the Diels-Alder reaction

A novel neighboring dicarboxyl-modified SBA-15 (SBA-15-(COOH)₂) has been synthesized by the Diels-Alder reaction of cyclopentadienyl-modified SBA-15 (SBA-15-Cp), which was synthesized by co-condensation of (2-(cyclopenta-1,3-dienyl) ethyl) triethoxysilane and tetraethoxyorthosilicate in the presence of P123 as structure directing agent, with maleic anhydride and hydrolysis in dilute sulfuric acid. This novel material was characterized by N₂ sorption, X-ray diffraction and transmission electron microscopy. The results showed that the ordered mesoporous structure of SBA-15-Cp has been preserved after the Diels-Alder reaction and hydrolysis. Fourier transformed infrared spectroscopy investigation indicated that neighboring dicarboxyl groups were successfully incorporated in SBA-15. The acidity capacity and the dissociation constant for SBA-15-(COOH)₂ were ca. 0.54 mmol/g and 4.84 respectively.     

Pd-porphyrin functionalized ionic liquid-modified mesoporous SBA-15: An efficient and recyclable catalyst for solvent-free Heck reaction

The Pd-porphyrin functionalized ionic liquid could be covalently anchored in the channels of mesoporous SBA-15 through ion-pair electrostatic interaction between imidazolium-cationic and Pd-porphyrin-anionic moieties. Such modified SBA-15 materials were prepared successfully via a post-synthesis (surface sol-gel polymerization) or a one-pot sol-gel procedure, which were characterized by powder X-ray diffraction, UV-visible spectroscopy, Fourier transform infrared spectroscopy, N₂ sorption, elemental analysis, and transmission electron microscopy. The modified SBA-15 materials are efficient and recyclable catalysts for cross-coupling of aryl iodides or activated aryl bromides with ethyl acrylate without activity loss and Pd leaching even after 9 runs.     

Inclusion of cefalexin in SBA-15 mesoporus material and release property

SBA-15 (Santa Barbara Amorphous-15) is a high ordered mesoporous material. It has the advantages of a non-toxic property, good hydrothermal stability and thermal stability, etc. Inside inner surface a lot of silanols exist. Pore diameter size is uniform and pore size distribution is narrow. This structural feature makes SBA-15 have a higher loading drug amount and be able to effectively extend the drug release cycle. In this paper, polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol was used as template and tetraethyl orthosilicate was used as silica source to prepare SBA-15 by hydrothermal synthesis method. Cefalexin was included in SBA-15 and the included cefalexin drug content was 158.72 mg/g. The composite materials were characterized by using chemical analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared (IR) spectroscopy, and low temperature nitrogen adsorption–desorption. The results showed that cefalexin had been successfully included in host SBA-15 pore channels. Rational analyses of the release processes of cefalexin drug from the pores of SBA-15 to the simulated body fluid, simulated gastric juice and simulated intestinal fluid were made and sustained-release effects of the drug in complex system were studied. The results showed that in simulated body fluid within 1–5 h cefalexin was fast released and the cumulative release reached 50.00% at 5 h. In 15–20 h, the sustained release speed of cefalexin drug in the composite material decreased and the sustained-release cumulative amount reached 99.87% at 20 h. The release of cefalexin was basically complete. In simulated gastric fluid, composite material sustained-release ended at 4 h, the cumulative sustained release ratio reaching 26.10%. In simulated gastric fluid, the sustained-release was complete at 7 h, the cumulative sustained release ratio reaching 32.46%. The composite material of SBA-15 and cefalexin could improve efficiency of the sustained-release of drug and has a very great potential applicable value.     

Catalytic activity of ratio-dependent SBA-15 supported cerium/Pt catalysts for highly selective oxidation reaction of benzyl alcohol to benzaldehyde

The Pt/Ce bimetal doped Mesoporous SBA-15 with various metal ratios was prepared by a wet chemical route. Several characterization methods were applied to determine the structural and chemical properties of the catalyst such as XRD, FT-IR, SEM, BET, and TEM Analysis. The prepared SBA-15 catalyst has a hexagonal mesoporous structure after the addition of cerium doesn’t affect the structure of the SBA-15 catalyst it is also confirmed by TEM analysis. The catalytic performances of the Pt/Ce-SBA-15 catalysts were examined in the BzOH conversion under acetonitrile as a solvent and tert-butyl hydroperoxide (TBHP) as an oxidant. The Pt/CeO₂(15%)-SBA-15 (PCS-15) is the best catalyst composition of the prepared catalyst with a maximum conversion of 98.5% and selectivity of 100%. The reaction parameters like the molar ratio of TBHP: BzOH, catalyst amount, temperature, and reaction time were explored in detail. The recycling studies show that the synthesized Pt/CeO₂(15%)-SBA-15 (PCS-15) catalyst is more stable up to 7 consecutive runs. The Pt/CeO₂(15%)-SBA-15 composite has tremendous application potential in organic synthesis, fuel cells, and electrochemical biosensors due to its outstanding reactivity, excellent selectivity, and remarkable stability as well as recyclability.     

Synthesis, characterization, and enhanced luminescence of CaWO4:Eu3+/SBA-15 composites

Considering the combination of lanthanide-doped CaWO₄ nanophosphor and mesoporous matrix may contribute to superior luminescent properties, CaWO₄:Eu³⁺/SBA-15 composites were successfully synthesized in a mild condition. The physicochemical properties of the resultant composites were carefully characterized by X-ray diffraction, high-resolution transmission electron microscopy, inductive coupled plasma optical emission spectroscopy (ICP), N₂ adsorption–desorption, Fourier transform infrared spectroscopy, and luminescence spectra. It’s found that the incorporation of CaWO₄:Eu³⁺ showed no obvious impact on the ordered mesostructure of the host matrix SBA-15, which, however, led to a decrease of BET surface area from 836 to 187 m² g⁻¹ for pure SBA-15 and CES (0.5), respectively. ICP results indicated that the real loaded amount of CaWO₄:Eu³⁺ in SBA-15 host was lower than the initial molar ratios (x) of CaWO₄:Eu³⁺ to SBA-15 for all samples. The maximum loaded level of CaWO₄:Eu³⁺ in SBA-15 is about 27.3 %. Moreover, the real Eu³⁺ dopant concentration increased with the initial molar ratios (x), which showed a maximum of about 6.51 % at x = 0.25. The resultant CaWO₄:Eu³⁺/SBA-15 composites exhibited enhanced-luminescent properties than that of pure CaWO₄:Eu³⁺ nanoparticles, which can be mainly attributed to the variation of Eu³⁺ dopant concentration and the host-protect effect through interaction between guest molecules and host matrix. The available large surface area, pore volume, and superior luminescent properties would facilitate future applications for the composites.