2-Mercaptothiazoline modified mesoporous silica for mercury removal from aqueous media

Mesoporous silicas (SBA-15 and MCM-41) have been functionalized by two different methods. Using the heterogeneous route the silylating agent, 3-chloropropyltriethoxysilane, was initially immobilized onto the mesoporous silica surface to give the chlorinated mesoporous silica Cl-SBA-15 or Cl-MCM-41. In a second step a multifunctionalized N, S donor compound (2-mercaptothiazoline, MTZ) was incorporated to obtain the functionalized silicas denoted as MTZ-SBA-15-Het or MTZ-MCM-41-Het. Using the homogeneous route, the functionalization was achieved via the one step reaction of the mesoporous silica with an organic ligand containing the chelating functions, to give the modified mesoporous silicas denoted as MTZ-SBA-15-Hom or MTZ-MCM-41-Hom. The functionalized mesoporous silicas were employed as adsorbents for the regeneration of aqueous solutions contaminated with Hg (II) at room temperature. SBA-15 and MCM-41 functionalized with MTZ by the homogeneous method present good mercury adsorption values (1.10 and 0.7mmolHg (II)/g of silica, respectively). This fact suggests a better applicability of such mesoporous silica supports to extract Hg (II) from aqueous solutions. In addition, it was observed the existence of a correlation between mercury adsorption with pore size and volume since, SBA-15 with lower areas and higher pore sizes functionalized with sterically demanding ligands, show better adsorption capacities than functionalized MCM-41.     

Photoelectric properties of nano-ZnO fabricated in mesoporous silica film

Via electrochemical deposition, nanosized zinc oxide (nano-ZnO) is prepared within a template of mesoporous silica (MPS) film fabricated on a conductive substrate. Enhanced dark current from the nano-ZnO in MPS film is obtained because nano-ZnO is located in the nanosized pores of MPS. Most of the nano-ZnO surface is prevented from contacting ambient oxygen, and the combination of oxygen with free electrons of this n-type semiconductor is avoided; thus the free electrons increase the conductivity. Photodetection to ultraviolet (UV) light is examined at the exciting wavelength of 365 nm. The photocurrent with fast growing and decay times is observed due to the photo-generated holes being trapped at the interface between ZnO and pore walls of MPS film, while producing the photocurrent by photo-generated electrons. Photoluminescence (PL) spectrum of nano-ZnO in MPS film at room temperature shows increased amount of oxygen vacancies in these nano-ZnO, which might contribute to the conductivity.     

Superior anti-corrosion and self-healing bi-functional polymer composite coatings with polydopamine modified mesoporous silica/graphene oxide

In this article,graphene oxide (GO) and benzotriazole-loaded mesoporous silica nanoparticles (BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine (PDA),preparing a self-healing bi-functional GO (fGO) used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP) coatings.Scanning electronic microscopy (SEM) images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has pH-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42 × 107 Ω cm2) after 30 days immersion in 3.5 wt.％ NaCl solution revealed 2 orders of magnitude higher that of blank WEP (1.17 × 105 Ω cm2).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.     

Preparation of high nickel-containing MCM-41-type mesoporous silica via a modified direct synthesis method

A method with modifying tetraethyl orthosilicate (TEOS) with nickel species has been developed for the synthesis of mesoporous silica with high nickel content (11.8 wt.% of Ni or even higher). With the method, MCM-41-type materials were obtained with high BET surface area reaching 868 m²/g and pore volume up to 0.73 cm³/g. The materials were characterized by means of X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, N₂ adsorption, Fourier transform infrared and X-ray photoelectron spectroscopy. Nickel species were incorporated into the silica frameworks. The mesostructures still remain after activation using H₂ at 773 K.     

纳米多孔二氧化硅薄膜的制备与表征

以正硅酸乙酯为原料,采用酸/碱两步溶胶 凝胶法、结合匀胶和超临界干燥等工艺在硅片上成功制备了纳米多孔二氧化硅薄膜。适合匀胶的二氧化硅溶胶的粘度范围为 9~15mPa·s;多孔二氧化硅薄膜表面均匀平整,其厚度为400~1000nm;折射率为1.09~1.24;介电常数为1.5~2.5。该多孔二氧化硅薄膜具有三维网络结构,二氧化硅微粒直径为10~20nm。     

Prussian Blue electrodeposition within an oriented mesoporous silica film: preliminary observations

Prussian Blue (PB) has been electrochemically grown through thin mesoporous silica films of novel generation, exhibiting regular arrays of hexagonally packed mesopores channels (3 nm in diameter) oriented perpendicular to the underlying electrode surface. Due to confinement effects, special care has to be taken to ensure effective permeability of PB precursors through the hard silica template, which was best achieved by pulsed electrodeposition from a high ionic strength medium (2 M KCl). Energy dispersive X-ray spectroscopy associated to electron microscopy was used to evidence the presence of PB in the vertically-aligned mesopores, which was also assessed by their electrocatalytic behavior towards H₂O₂ reduction.     

氟烷基官能化介孔氧化硅纳米颗粒及涂层的制备

以正硅酸乙酯和氟代烷基硅氧烷为硅源,十六烷基三甲基氯化铵为表面活性剂,三乙醇胺为催化剂在弱碱性条件下制备了氟烷基官能化的纳米介孔氧化硅颗粒。并采用动态光散射、FT-IR、SEM、TEM、氮气吸附-脱附以及UV-Vis光谱对产物进行了表征。结果表明:反应在45min后能得到粒径不再变化的30nm左右尺寸均一、高分散、高孔率的氟烷基官能化介孔氧化硅纳米颗粒。纳米颗粒涂层对光学玻璃具有良好的增透性能,是一种性能优良的光学涂层材料。     

Preparation of mesoporous silica nanoflakes and nanospheres with perpendicular pore channels

Silica nanoflakes and nanospheres with perpendicular pore channels are attractive due to their potential applications. Herein, the nanoflakes were prepared using the self-assemblies of a chiral low-molecular-weight amphiphile, L-18Ala4PyBr, as the templates; and nanospheres were prepared using this amphiphile and cyclohexane as a co-structure-directing agent. By gradually increasing the bridging alkylene chain length of L-18Ala4PyBr, amphiphiles L-18Ala6PyBr and L-18Ala11PyBr were synthesized. Nanoflakes with perpendicular pore channels and nanoworms with horizontal pore channels were prepared using L-18Ala6PyBr and L-18Ala11PyBr, respectively. The hydrophobic association of the bridging alkylene chains should play an important role in controlling the morphologies and pore architectures of the mesoporous silicas.     

水性含磷功能性聚合物的制备及应用

水性含磷功能性聚合物是一种环境友好材料,且具有阻燃、耐热、防腐、生物相容性好以及改善粘接性能等多种特性.本文介绍了水性含磷功能性聚合物的结构和制备方法,综述了其在粘合剂、涂料以及生物医用材料等方面的应用报道,并展望了其发展前景.     

Fabrication of mesoporous silica KIT-6/polymer composite and its low thermal expansion property

Here we fabricate mesoporous silica KIT-6/epoxy polymer composite as low thermal expansion material. From the specific gravity of the composites, almost all the mesopores (around 90%) are successfully filled with the epoxy polymers. The thermal mobility of the confined polymer molecules inside the mesopores is restricted by the rigid silica frameworks. Therefore, the volume expansion degree of the composites is much lower than that of epoxy polymer. Through the comparative experimental using FSM-16-type mesoporous silica with a 2 dimensional (2D) hexagonal mesostructure, it is proved that KIT-6 system with a 3D bicontinuous gyroid mesostructure more effectively contributes low thermal expansion property.     

纳米多孔二氧化硅薄膜的制备及其光学性质研究

以正硅酸乙酯(TEOS)为先驱体，采用溶胶-凝胶法，结合旋转涂胶和超临界干燥等工艺，在硅片上制备了纳米多孔SiO2薄膜。XRD和AFM表明该SiO2薄膜为无定形态，具有多孔网络结构，表面均匀平整，其SiO2基本粒子和孔隙的直径为30～40nm。利用椭偏光谱仪测量了SiO2薄膜在波长245～1650nm的椭偏光谱，采用Si／cauchy／rough结构模型对该光谱进行了拟合，获得了SiO2薄膜的厚度和光学常数。SiO2薄膜的厚度为500～1100nm；折射率为1．13～1．21；孔隙率为56％～70％；介电常数为1．9～2．3。     

A hybrid system: MnO-incorporated mesoporous silica nanoparticles for theranostic applications

The need for an alternative \({ T}_{1}\) contrast enhancer for magnetic resonance imaging (MRI) has been escalating owing to the toxicity profiles observed with the use of commercial contrast agents. Manganese oxide nanoparticles provide an optimal solution for the problem, as it is an endogenous co-factor for many enzymes in the biological system. In the present work, we have synthesized mesoporous silica nanoparticles encapsulated with manganese oxide nanoparticles as a positive contrast enhancer for MRI applications. Spherical magnetic MnO nanoparticles with divalent oxidation state were also synthesized and utilized as control to compare the efficiency of the nano-hybrid system. MRI showed higher contrast enhancement with the use of nano-hybrid and the relaxivity value for \({ T}_{1}\)-weighted imaging was calculated to be \(2.6~\hbox {mg ml}^{-1}~\hbox {s}^{-1}\). Also, the developed system was validated for its usefulness as a therapeutic system through adsorption studies. Therefore, the nano-hybrid has the potential to be a competent MRI contrast enhancer that could be used for theranostic applications.     

Ratiometric fluorescence detection of mercury ions in water by conjugated polymer nanoparticles

We present dye-doped polymer nanoparticles that are able to detect mercury in aqueous solution at parts per billion levels via fluorescence resonance energy transfer (FRET). The nanoparticles are prepared by reprecipitation of highly fluorescent conjugated polymers in water and are stable in aqueous suspension. They are doped with rhodamine spirolactam dyes that are nonfluorescent until they encounter mercury ions, which promote an irreversible reaction that converts the dyes to fluorescent rhodamines. The rhodamine dyes act as FRET acceptors for the fluorescent nanoparticles, and the ratio of nanoparticle-to-rhodamine fluorescence intensities functions as a ratiometric fluorescence chemodosimeter for mercury. The light harvesting capability of the conjugated polymer nanoparticles enhances the fluorescence intensity of the rhodamine dyes by a factor of 10, enabling sensitive detection of mercury ions in water at levels as low as 0.7 parts per billion.     

Cr(VI) adsorption on functionalized amorphous and mesoporous silica from aqueous and non-aqueous media

A mesoporous silica (SBA-15) and amorphous silica (SG) have been chemically modified with 2-mercaptopyridine using the homogeneous route. This synthetic route involved the reaction of 2-mercaptopyridine with 3-chloropropyltriethoxysilane prior to immobilization on the support. The resulting material has been characterized by powder X-ray diffraction, nitrogen gas sorption, FT-IR and MAS NMR spectroscopy, thermogravimetry and elemental analysis. The solid was employed as a Cr(VI) adsorbent from aqueous and non-aqueous solutions at room temperature. The effect of several variables (stirring time, pH, metal concentration and solvent polarity) has been studied using the batch technique. The results indicate that under the optimum conditions, the maximum adsorption value for Cr(VI) was 1.83 ± 0.03 mmol/g for MP-SBA-15, whereas the adsorption capacity of the MP-SG was 0.86 ± 0.02 mmol/g. On the basis of these results, it can be concluded that it is possible to modify chemically SBA-15 and SG with 2-mercaptopyridine and to use the resulting modified silicas as effective adsorbents for Cr(VI).     

The removal of reactive dyes from aqueous solutions using chemically modified mesoporous silica in the presence of anionic surfactant-the temperature dependence and a thermodynamic multivariate analysis

The three-parameter Sips adsorption model was successfully employed to modeled equilibrium adsorption data of a yellow and a red dye onto a mesoporous aminopropyl-silica, in the presence of the surfactant sodium dodecylbenzenesulfonate (DBS) from 25 to 55 degrees C. The results were evaluated in relation to the previously reported surface tension measurements. The presence of curvatures of the van()t Hoff plots suggested the presence of non-zero heat capacities terms (Delta(ads)C(p)). For the yellow dye, it is observed that the values of Delta(ads)H are almost all positive and they decrease in endothermicity, in the absence and in the presence of DBS, from 25 to 55 degrees C. For the red dye, there is an increase in endothermicity in relation to the temperature increase. The negative Delta(ads)G values indicate spontaneous adsorption processes. Almost all adsorption entropy values (Delta(ads)S) were positive. This suggests that entropy is a driving force of adsorption. The adsorption thermodynamic parameters were also evaluated using a new 2(3) full factorial design analysis. The multivariate polynomial modelings indicated that the thermodynamic parameters are also affected by important interactive effects of the experimental factors and not by the temperature changes alone.     

Preparation and characterization of vinyl-functionalized mesoporous SBA-15 silica by a direct synthesis method

Vinyl groups were used to functionalize the pore channels of mesoporous SBA-15 materials by the co-condensation of tetraethyl orthosilicate (TEOS) and triethoxyvinylsilane (TEVS) 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 FT-IR, XRD, TEM, solid state NMR and N₂ adsorption, in order to study the effect of vinyl concentration on their mesoscopic order and pore structure. The results show that vinyl groups are attached covalently to the pore wall of SBA-15 after modification. The mesoscopic architecture almost remains intact upon functionalization, with only a minor decrease of the intensity of (110) diffractions for the 20 mol% TEVS-functionalized samples, which still preserve a desirable pore structure, with a surface area of 883.7 m²/g, a pore volume of 0.98 cm³/g and a mean pore size of 4.4 nm.     

Infrared spectroscopic analysis of siloxane network modification of mesoporous silica film by silylation and cesium doping

Effects of pore surface silylation and cesium doping on the siloxane bonding structure of mesoporous silica (MPS) film were analyzed using infrared spectroscopy. MPS film was derived by sol-gel method and self-assembling technology of non-ionic surfactant template. Cesium (Cs) catalyst was doped to the precursor solution with the amounts of 0, 5, and 15 wt-ppm. Vapor phase silylation was performed by transporting tetramethylcyclotetrasiloxane (TMCTS) or hexamethyldisilazane (HMDS). From dispersion analysis of the infrared spectrum, transverse optical (TO) function and longitudinal optical (LO) function of silica skeleton, which concern the ionic vibration of siloxane bonding at ~ 1000-1300 cm⁻¹, were determined. In terms of LO-TO splitting width of the disorder-induced oxygen vibration (AS₂) mode, siloxane network connectivity was discussed. Oscillator strength of ionic vibration was also calculated quantitatively. It was found that TMCTS treated MPS had highly cross linked siloxane network with increased oscillator strength compared to those of HMDS treated MPS. Cs doping promoted siloxane network connectivity, while the oscillator strength was negligibly changed. The connectivity and oscillator strength were almost equal to those of 1000 °C annealed gel silica. Mechanical enhancement associated with the TMCTS treatment and Cs doping was presumably due to increased degree of the siloxane network.     

Novel mesoporous composites based on natural rubber and hexagonal mesoporous silica: Synthesis and characterization

The present study is the first report on the synthesis and characterization of mesoporous composites based on natural rubber (NR) and hexagonal mesoporous silica (HMS). A series of NR/HMS composites were prepared in tetrahydrofuran via an in situ sol–gel process using tetraethylorthosilicate as the silica precursor. The physicochemical properties of the composites were characterized by various techniques. The effects of the gel composition on the structural and textural properties of the NR/HMS composites were investigated. The Fourier-transform infrared spectroscopy (FTIR) and ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR) results revealed that the surface silanol groups of NR/HMS composites were covered with NR molecules. The powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) data indicated an expansion of the hexagonal unit cell and channel wall thickness due to the incorporation of NR molecules into the mesoporous structure. NR/HMS composites also possessed nanosized particles (∼79.4 nm) as confirmed by scanning electron microscopy (SEM) and particle size distribution analysis. From N₂ adsorption–desorption measurement, the NR/HMS composites possessed a high BET surface area, large pore volume and narrow pore size distribution. Further, they were enhanced hydrophobicity confirmed by H₂O adsorption–desorption measurement. In addition, the mechanistic pathway of the NR/HMS composite formation was proposed.