One-pot synthesis of ordered mesoporous carbon–silica nanocomposites templated by mixed amphiphilic block copolymers

Mixed amphiphilic block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) and polydimethylsiloxane-poly(ethylene oxide) (PDMS–PEO) have been successfully used as co-templates to prepare ordered mesoporous polymer–silica and carbon–silica nanocomposites by using phenolic resol polymer as a carbon precursor via the strategy of evaporation-induced self-assembly (EISA). The ordered mesoporous materials of 2-D hexagonal (p6m) mesostructures have been achieved, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen-sorption measurements. Experiments show that using PDMS–PEO as co-template can enlarge the pore sizes and reduce the framework shrinkage of the materials without evident effect on the specific surface areas. Ordered mesoporous carbons can then be obtained with large pore sizes of 6.7 nm, pore volumes of 0.52 cm³/g, and high surface areas of 578 m²/g. The mixed micelles formed between the hydrophobic PDMS groups and the PPO chains of the F127 molecules should be responsible for the variation of the pore sizes of the resulting mesoporous materials. Through the study of characteristics of mesoporous carbon and mesoporous silica derived from mother carbon–silica nanocomposites, we think mesoporous carbon–silica nanocomposites with the silica-coating mesostructure can be formed after the pyrolysis of the PDMS–PEO diblock copolymer during surfactant removal process. Such method can be thought as the combination of surfactant removal and silica incorporation into one-step. This simple one-pot route provides a pathway for large-scale convenient synthesis of ordered mesostructured nanocomposite materials.     

Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

Sonochemical synthesis of ordered SnO₂/CMK-3 nanocomposites and their lithium storage properties

In this study, we successfully prepare SnO(2) nanoparticles inside the pore channels of CMK-3 ordered mesoporous carbon via sonochemical method. The content of SnO(2) is 17 wt % calculated according to the energy-dispersive X-ray spectroscopy (EDS) result. CMK-3 with 17 wt % loading of SnO(2) nanoparticles has a large specific surface area and pore volume. Electrochemical performance demonstrates that the ordered SnO(2)/CMK-3 nanocomposites electrode possesses higher reversible capacity and cycling stability than that of original CMK-3 electrode. Moreover, the ordered SnO(2)/CMK-3 nanocomposites electrode also exhibits high capacity at higher charge/discharge rate. The improved electrochemical performance is attributed to the nanometer-sized SnO(2) formed inside CMK-3 and the large surface area of the mesopores (3.4 nm) in which the SnO(2) nanoparticles are formed.     

Synthesis,characterization and magnetic performance of Co-incorporated ordered mesoporous carbons

Co-incorporated ordered mesoporous carbon (Co-OMC) with magnetic frameworks has been synthesized via a one-pot self-assembly strategy. The effects of cobalt loading on carbon matrix, adsorption properties and magnetic properties of the resultant mesostructured cobalt/carbon composites were investigated by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and magnetometer measurements. The results show that the mesoporous composites with a high cobalt content (such as 18.0 wt%) possess an ordered and uniform mesoporous structure (5.3 nm), high surface areas (up to 687 m²/g) and high pore volumes (up to 0.54 cm³/g). Cobalt nanoparticles of size 4–9 nm are confined inside the mesopores or walls of the mesoporous carbon. These materials exhibit typical ferromagnetic characteristics. The saturation magnetization strength can be easily adjusted by changing the content of cobalt. The carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMC also.     

Facile fabrication of magnetic nanocomposites of ordered mesoporous carbon decorated with nNickel nanoparticles

A magnetic nanocomposite of ordered mesoporous carbon (CMK-3) decorated with nickel nanoparticles was synthesized successfully by a simple chemistry method. Nickel nanoparticles were prepared and uniformly supported on ordered mesoporous carbon CMK-3 by reduction route with CMK-3 as a reducing agent at 673 K. The Ni/CMK-3 composite materials were characterized by powder X-ray diffraction, nitrogen sorption, and transmission electron microscopy. As-prepared nickel nanoparticles supported on CMK-3 were crystalline with a face-center-cubic phase and a size distribution ranging from 10 to 60 nm. The BET special surface area and pore volume of Ni/CMK-3 were as high as 797 m2 g(-1) and 0.72 cm3 g(-1), respectively. The formation mechanism of the nickel nanoparticles outside the surface of CMK-3 was preliminarily discussed. The hysteresis loops of the CMK-3 decorated with nickel nanoparticles were measured by vibrating sample magnetometer (VSM), and the results showed that the composite was ferromagnetism with the saturated magnetization of 15 emu/g, and the coercivity value of 214 Oe. Furthermore, the application of Ni/CMK-3 as magnetically separable adsorbent for vitamin B2 was primarily examined in this study.     

Synthesis and characterization of surface-modified and organic-functionalized MCM-41 type ordered mesoporous materials

A new and efficient method for the preparation of MCM-41 type ordered mesoporous phases using phosphate as promoter under reflux conditions is reported. The various mesoporous materials studied were: silica (Si-MCM-41), alumino-silicate (Al-MCM-41), and titanium-silicate (Ti-MCM-41). Our concept of promoter-assisted synthesis of zeolites and related microporous materials was found to be applicable in the synthesis of ordered mesoporous materials as well. The addition of small catalytic quantity of phosphate ions (PO ₄ ³⁻ ), used as promoters, significantly reduced the synthesis time (by a factor of 3–4) of all these mesoporous materials. The synthesis of new MCM-41 type organic-inorganic composite materials with unique properties is also reported.     

Synthesis, characterization, and catalytic application of highly ordered mesoporous alumina-carbon nanocomposites

Highly ordered mesoporous carbon-alumina nanocomposites (OMCA) have been synthesized for the first time by a multi-component co-assembly method followed by pyrolysis at high temperatures. In this synthesis, resol phenol-formaldehyde resin (PF resin) and alumina sol were respectively used as the carbon and alumina precursors and triblock copolymer Pluronic F127 as the template. N2-adsorption measurements, X-ray diffraction, and transmission electron microscopy revealed that, with an increase of the alumina content in the nanocomposite from 11 to 48 wt.%, the pore size increased from 2.9 to 5.0 nm while the ordered mesoporous structure was retained. Further increasing the alumina content to 53 wt.% resulted in wormhole-like structures, although the pore size distribution was still narrow. The nanocomposite walls are composed of continuous carbon and amorphous alumina, which allows the ordered mesostructure to be well preserved even after the removal of alumina by HF etching or the removal of carbon by calcination in air. The OMCA nanocomposites exhibited good thermostability below 1000 °C; at higher temperatures the ordered mesostructure partially collapsed, associated with a phase transformation from amorphous alumina into γ-Al₂O₃. OMCA-supported Pt catalysts exhibited excellent performance in the one-pot transformation of cellulose into hexitols thanks to the unique surface properties of the nanocomposite.     

Facile fabrication of copper-supported ordered mesoporous carbon for antibacterial behavior

Copper-supported ordered mesoporous carbon (Cu/CMK-3) was prepared by impregnating ordered mesoporous carbon (CMK-3) with CuCl₂ aqueous solution. CMK-3 was served as a carrier for the continuous immobilization of Cu. The supported copper was observed to be the bivalence state, indicating that the Cu²⁺ ion was not reduced into cuprous species or metallic copper in the CMK-3. The BET surface area and pore volume of Cu/CMK-3 were 728 m²/g and 0.95 cm³/g, respectively. The antibacterial activities of Cu/CMK-3 were tested by means of minimal inhibitory concentration (MIC) and viable cell counting method. The results show that Cu/CMK-3 presents a good antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which indicates its potential applications as antibacterial material for microbiocides.     

Conditions and features of matrix and bulk carbonization of the organic precursors

Comparative research of matrix and bulk carbonization of some organic precursors (sucrose, acetonitrile) in silica mesoporous materials SBA-15 and KIT-6 was conducted. X-ray diffraction, nitrogen adsorption analysis, Raman spectroscopy were used for determination of the structural-sorption characteristics of the obtained materials. It was shown that the carbon mesoporous materials CMK-8 obtained in the mesopores of KIT-6 had higher adsorption characteristics because of features of three-dimensional cubic structure, larger pore volume and framework’s wall thickness. It was established that partially graphitized spatially well-organized carbon materials were formed as a result of pyrolysis of acetonitrile in the silica matrices SBA-15 and KIT-6. It was conditioned by the absence of considerable spatial limitations for growth of graphite structures on the initial stage of the synthesis when the pores of the matrix were not filled up with the organic precursor. Product of bulk carbonization of sucrose is compact carbon microporous framework with low sorption characteristics (micropore volume is 0.09 cm³/g).     

Preparation of hydrophilic mesoporous carbon and its application in dye adsorption

A hydrophilic mesoporous carbon (H-MS) has been prepared by a rapid redox reaction between mesoporous carbon (CMK-3) and an acidic potassium permanganate (KMnO₄) solution at room temperature. The obtained material has a hydrophilic surface by the modification of oxygen-containing groups, and meanwhile retains the ordered mesoporous structure. No obvious difference of pore size between H-MS and CMK-3, and the slight decrease of surface area and pore volume is due to the modification of oxygen-containing groups on the carbon surface. An improved property for adsorbing dyes in aqueous solution was observed in H-MC, and the adsorption amount at equilibrium is ~ 3 times higher than that of CMK-3.     

Infrared spectroscopic study of water in mesoporous silica under supercritical conditions

The structure of water under high temperature–pressure conditions in mesospace was investigated by measuring the infrared spectra of water in mesoporous silica. Absorption peaks attributed to OH-stretching vibration of water in mesoporous silica were detected at lower wavenumbers as compared with bulk water, and the absorption peak positions were dependent on pore diameter. For small pore diameters (3–20 nm), absorption peak positions of water were detected at lower wavenumbers (ca. 3,300 cm⁻¹) at 400 °C, while for larger pore diameters (30–50 nm) the peaks were detected at higher wavenumbers (ca. 3,500 cm⁻¹). We attribute these features to the effects of mesoporous silica surface structure on the structural and vibrational modes of water. Furthermore, absorption peak positions changed significantly at different pore sizes (20 and 30 nm), indicating that the structure of water in small pores approaches a more ice-like structure. Based on our experimental results, the structured water layer in mesoporous silica is estimated to be at least 10 nm thick, which is thicker than that previously documented in molecular dynamic simulation studies where the thickness of structured water was found to be two or three layers from the surface.     

Synthesis and characterization of bimodal rod-like mesoporous carbons from raffinose by SBA-15 templates

Mesoporous carbons with bimodal rod-like pore structures and tunable pore sizes from 3.66 to 5.42 nm were for the first time obtained by employing SBA-15 as templates and raffinose as carbon precursors. Small angle X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ sorption analysis, and Raman spectroscopy were used to determine the textural properties of the resulting materials. Bimodal frameworks with mesopores (4–5 nm) as well as macropores (125–130 nm) were achieved. The mesoporous carbons lost its ordered structure from the templates due to mesostructural shrinkage and collapse of mesopores, which resulted in partial duplicate of the template and pore-widening effect (meso to macropores). With the increasing of carbonization temperature from 500, 700 to 900 °C, the textural parameters such as specific surface areas, pore volumes, and mean pore diameters all increased significantly. In the temperature range studied, higher carbonization temperature would generate much more abundant porosity. The ratio of I _D to I _G (I _D/I _G) indicated a rather low crystallinity with the varying of aging temperature and the carbonization temperatures. The advantage of the procedure was that no acid or other chemical catalysts were involved during the infiltration and carbon formation process.     

Morphological control on SBA-15 mesoporous silicas via a slow self-assembling rate

Pluronic 123-templated mesoporous SBA-15 silica rods with a length of ca. 3.0–4.0 μm were easily synthesized in a dilute silicate solution with a pH value of 2.0 at room temperature. Through a good control on the synthetic condition and the chemical components, a high homogeneity (>95%) of the hexagonal SBA-15 silica rods can be achieved. In addition, the effect of the synthetic conditions including acid source, weight ratio of the P123/sodium silicate, temperature, water content, pH value, and applying shearing flow were explored in detail to tailor the morphologies of the SBA-15 mesoporous silicas. In this paper, we also focused on the counterion effect on the synthesis of the SBA-15 mesoporous silicas. It was found that the SO₄ ²⁻ counterion from H₂SO₄ has higher affinity to induce the formation of P123 rod-like micelles than that of Cl⁻, NO₃ ⁻. Meanwhile, we postulated that the self-assembly pathway of the silica species and the neutral tri-block copolymer micelles in a dilute solution with a pH value of 2.0 would occur through an S⁰···I⁰ rather than the S⁰X^−…I⁺ one as previously discussed. We further employed the SAB-15 mesoporous silica rods as the templates to synthesize high-quality CMK-3 mesoporous carbon rods by using commercially available phenol–formaldehyde (PF) resin as the carbon source.     

Synthesis and electrocatalytic activity of platinum nanoparticle/carbon nanotube composites

Pt/CNT nanocomposite materials with an average platinum particle size of 3–5 nm and platinum content of 13–28 wt % have been prepared by reducing chloroplatinic acid, H₂PtCl₆, in the presence of conical carbon nanotubes. The effect of synthesis conditions on the average platinum particle size, total platinum content, and surface composition of the nanocomposites has been studied using X-ray photoelectron spectroscopy, IR spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. Their performance has been assessed by cyclic and steady-state voltammetric techniques. The structure and composition effects on the electrocatalytic properties of the nanocomposites are discussed.     

Synthesis and characterization of ordered and cubic mesoporous silica crystals under a moderately acidic condition

Ordered and cubic mesoporous silica materials were synthesized by using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer as template under a moderately acidic condition of 0.5 mol/l HCl solution. These mesoporous materials were characterized by Fourier transform (FT) IR spectroscopy, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements. The three-dimensional cage-like microporosity of the prepared mesoporous silica having ordered hexagonal mesoporous structure was evidenced by the well-defined XRD patterns combined with TEM photographs. SEM observation shows a highly regular cubic crystal structure for the prepared mesoporous silica. The size of these crystallites was maintained within the range between 4 and 6 μm, which is fairly important for the application to the stationary phase for separation. The nitrogen adsorption–desorption analysis reveals that the prepared mesoporous silica possesses a small pore diameter of 3.68 nm, a total surface area of 363.648 m²/g, a total pore volume of 0.379 cm³/g, and a pore-wall thickness of 6.63 nm. These features may lead to higher thermal and hydrothermal stability, excellent microporosity, and good connectivity. The mesoporous silica prepared in this study exhibits potential applications to catalysis, sensoring, and separation.     

Synthesis of 3-dimensional mesoporous silica using a di-block copolymer template

Exploring polymeric surfactants as templates for synthesizing ordered mesoporous silicas has become increasingly important for both academic interests and industrial applications. In this work, we employed C₁₆EO₄₀, a di-block copolymer polyethylene-poly(ethylene oxide), as template in an attempt to synthesize a modified 3-dimensional wormhole mesoporous silicas (WMS-39). In addition, various synthesizing conditions were investigated, including pre-hydrolysis time of TEOS, reaction temperatures and the ratios of TEOS to template. The products were characterized using powder XRD, TEM, ²⁹Si MAS NMR and nitrogen adsorption measurements. The characteristics of as-synthesized mesoporous silica were compared with SBA-15, a highly ordered mesoporous silica, prepared using non-ionic tri-block copolymers of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) as templates. The WMS-39 materials have a BET surface area of 600–970 m²/g and narrowly distributed pore diameter around 3.9 nm. The morphology of WMS-39 was found to be wormhole framework as indicated in TEM diagrams. Thermal transformation of the as-synthesized mesoporous materials were carefully analyzed with TGA/DTA. Findings obtained from this work enable us to propose a modified assembly mechanism of mesoporous silicas.     

Preparation of conductive transparent adhesive films from carbon nanomaterials and polar acrylate

Electrically conductive optically clear adhesives (ECOCAs) were prepared using a nanostructured carbon material (CMK-3(150)) as a conductive filler. The mesoporous carbon material, CMK-3(150), was synthesized using an ordered mesoporous silica template to produce inverse replica ordered mesoporous carbon material with an approximately 10 nm pore diameter. An adhesive solution of acrylic monomers containing polar acrylate, CMK-3(150), and thermal initiator was reacted at 80 degrees C to prepare the ECOCA composite which had appropriate viscosity for further processing. The adhesive composite was adhered to various surfaces including ITO films upon thermal processing at 60 degrees C to afford a highly transparent and adhesive film. Tensile strength of the ECOCA films was increased with the contents of conductive filler up to 4 wt%. The percolation concentration of the CMK-3(150) in the composite was approximately 7 wt%, which is much less than those of typical conductive fillers. The optimum content of CMK-3(150) to assure optical clarity, tensile strength, and high conductivity was 2-3 wt%.     

Synthesis of mesoporous structured hydroxyapatite particles using yeast cells as the template

In this study, hydroxyapatite (HAp) particles with mesoporous structure have been synthesized from calcium hydroxide and di-ammonium hydrogen phosphate using yeast cells as the template. The characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR), N₂ adsorption–desorption isotherms (NADI), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used for determination of the particles structure (particle size, structural evolution and morphology). The results show that HAp particles with mesoporous structure could be produced. The size of HAp particles was approximately hundreds of nanometer. The pore width of HAp particles was in the range of 2.0–40 nm and the maximum centered around 4.5 nm.     

Structure and photoluminescence of SiC/ZnO nanocomposites prepared by radio frequency alternate sputtering

SiC/ZnO nanocomposites were prepared by radio frequency alternate sputtering followed by annealing in N₂ ambient. Well-crystallized ZnO matrix was obtained after annealed at 750 °C according to X-ray diffractometer patterns. Transmission electron microscopy analyses indicated that the SiC thin layer aggregated to form SiC nanoclusters with the average size of 7.2 nm when the annealing temperature was 600 °C. When the annealing temperatures increased above 900 °C, some of the SiC nanoclusters changed into SiC nanocrystals and surfacial atoms of the SiC nanoparticles were surrounded by a layer of SiO _x (x ≤ 2) according to the Fourier transform infrared spectrums. The SiC/ZnO nanocomposites annealed at 750 °C exhibit strong photoluminescence bands ranging from 250 to 600 nm. UV light originates from the near band edge emission of ZnO and the blue emission peaked at around 465 nm (2.7 eV) may be due to the formation of emission centers caused by the defects in Si–O network, while the green-emission peak at around 550 nm (2.3 eV) may be attributed to the deep level recombination luminescence caused by the vacancies of oxygen and zinc.     

Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.