Synthesis, characterization, and electrochemical properties of ordered mesoporous carbons containing nickel oxide nanoparticles using sucrose and nickel acetate in a silica template

New ordered mesoporous carbons containing nickel oxide nanoparticles have been successfully synthesized by carbonization of sucrose in the presence of nickel acetate inside SBA-15 mesoporous silica template. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, and transmission electron microscopy (TEM). The NiO nanoparticles were embedded inside the mesoporous carbon framework due to the simultaneous pyrolysis of nickel acetate during carbonization. The electrochemical testing of the as-made nanocomposites showed a large specific capacitance of 230 F g⁻¹ using 2 M KOH as the electrolyte at room temperature. This is attributed to the nanometer-sized NiO formed inside mesoporous carbons and the high surface area of the mesopores in which the NiO nanoparticles are formed. Furthermore, the synthetic process is proposed as a simple and general method for the preparation of new functionalized mesoporous carbon materials, for various applications in catalysis, sensor or advanced electrode material.     

Synthesis and characterization of nanocast silica NCS-1 with CMK-3 as a template

Nanocast silica (NCS-1) was synthesized by a casting process by employing the mesoporous carbon CMK-3 (the replica of SBA-15) as a template, tetraethoxysilane (TEOS) as the silica source, and hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS-1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA-15 used for the synthesis of CMK-3 over two replication steps on the nanometer scale. This demonstrates the well-connected porosity in CMK-3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS-1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS-1 can be tuned to a certain range by varying these parameters.     

Mesoporous silica SBA-15, a new adsorbent for bioactive polyphenols from red wine

The aim of this paper is to evaluate the ability of the mesoporous silica SBA-15 to adsorb polyphenols from red wine. The mesoporous molecular sieve silica SBA-15 was hydrothermally synthesized in acidic media and characterized by SAXRD, BET, EDX and SEM. The adsorption behavior of mesoporous silica SBA-15 was investigated at 5 °C for 24 h using an adsorbent dose of 8 g SBA-15 L⁻¹ red wine. The total polyphenols content expressed as mg of gallic acid equivalents (GAE L⁻¹) was estimated from the standard curve of gallic acid (absorbance at 280 nm). HPLC chromatograms of methanolic extract from mesoporous SBA-15 at 256, 280, 324, and 365 nm exhibits the strong retention of quercetin and cis-resveratrol and a reasonable retention of trans-resveratrol, catechin, epicatechin, rutin, and phenolic acids (meta- and para-hydroxybenzoic, vanillic, caffeic, syringic, salicylic and para-coumaric acids).     

Highly ordered Ti-SBA-15: Efficient H2 adsorbent and photocatalyst for eco-toxic dye degradation

Highly ordered 2D-hexagonal mesoporous titanium silicate Ti-SBA-15 materials (space group p6mm) have been synthesized hydrothermally in acidic medium employing amphiphilic tri-block copolymer, Pluronic F127 as structure directing agent. Samples are characterized by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, FT IR spectroscopy, UV-visible diffuse reflectance measurements, N₂ adsorption/desorption and TG-DTA analysis. XRD and TEM results suggested the presence of highly ordered mesophase with hexagonal pore arrangements. BET surface area for Ti-SBA-15 (924 m² g⁻¹) is considerably higher than the pure silica SBA-15 (611 m² g⁻¹) prepared following the same synthetic route. UV-visible and FT-IR studies suggested the incorporation of mostly tetrahedral titanium (IV) species, along with some six-coordinated sites in the silicate network. This material shows very good H₂ adsorption capacity at higher pressure and excellent catalytic activity in the photocatalytic degradation of ecologically abundant dye methylene blue.     

Reversible replication between ordered mesoporous silica and mesoporous carbon

Highly ordered mesoporous silica can be regenerated from a mesoporous carbon CMK-3 that is a negative replica of mesoporous silica SBA-15, indicating reversible replication between carbon and inorganic materials.     

Highly ordered Zn-doped mesoporous silica: An efficient catalyst for transesterification reaction

Designing highly ordered material with nanoscale periodicity is of great significance in the field of solid state chemistry. Herein, we report the synthesis of highly ordered 2D-hexagonal mesoporous zinc-doped silica using a mixture of anionic and cationic surfactants under hydrothermal conditions. Powder XRD, N₂ sorption, TEM analysis revealed highly ordered 2D-hexagonal arrangements of the pores with very good surface area (762 m² g⁻¹) in this Zn-rich mesoporous material. Chemical analysis shows very high loading of zinc (ca. 12.0 wt%) in the material together with retention of hexagonal pore structure. Interestingly, high temperature calcination resulted into zinc silicate phase, unlike any ZnO phase, which otherwise is expected under heat treatments. High surface area together with Zn loading in this mesoporous material has been found useful for the catalytic activity of the materials in the acid-catalyzed transesterification reactions of various esters under mild liquid phase conditions.     

Amperometric sensing of norepinephrine at picomolar concentrations using screen printed,high surface area mesoporous carbon

Norepinephrine (NE) is detected amperometrically using the enzyme Phenylethanolamine N-methyl transferase and cofactor S-(5′-Adenosyl)-l-methionine chloride dihydrochloride with disposable screen printed mesoporous carbon electrodes. The role of internal surface area and pore size of the mesoporous carbon is systematically examined using soft-templated, mesoporous silica–carbon powders with highly microporous walls obtained from etching of the silica to produce powders with surface areas ranging from 671–2339 m² g⁻¹. As the surface area increases, the sensitivity of the biosensor at very low NE concentrations (0–500 pg mL⁻¹) in phosphate buffered saline (PBS) increases just as the current signal increases with respect to the NE concentration of 81–1581 μA mL ng⁻¹ cm⁻² for the mesoporous carbons. The best performing electrode provides similar sensitivity in whole rabbit blood in comparison to PBS despite no membrane layer to filter the non-desired reactants; the small (<5 nm) pore size and large internal surface area acts to minimize non-specific events that decrease sensitivity.     

Effect of the conditions of the matrix carbonization of sucrose on the structure and adsorption properties of mesoporous carbon materials

A study was carried out on the effect of the conditions of the matrix carbonization of sucrose in MCM-48 and SBA-15 silica mesoporous molecular sieves on the structure and adsorption properties of the resultant CMK-1 and CMK-3 mesoporous carbon molecular sieves. CMK-3 was found to be a structurally similar replica of SBA-15. An exact replica is not formed in the case of MCM-48. This failure is attributed to considerable deformation of the matrix during the carbonization process due to the bicontinuous pore system and thinner framework walls. This is probably related to transformation of the carbon material into a low symmetry product upon detemplating of the C/MCM-48 composite (dissolution of the silica). Mesoporous carbon materials were obtained with good adsorption structure features. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 365–370, November–December, 2008.     

Direct multielement trace analyses of silicon carbide powders by spark ablation simultaneous inductively coupled plasma optical emission spectrometry

A procedure for the direct analysis of silicon carbide powders (SiC) by simultaneous detection inductively coupled plasma optical emission spectrometry using a Spectro-CIROS™ spectrometer (CCD-ICP-OES) and a novel spark ablation system Spectro-SASSy (SA) as sample introduction technique is described. The sample preparation procedure for SA of non-conducting material is based on mixing the sample powders with a conducting matrix, in this case copper and briquetting pellets. Pressing time, pressure and mixing ratio are shown to be important parameters of the pelleting technique with respect to their mechanical stability for the reliability of the analysis results. A mixing ratio of 0.2 g +0.6 g for SiC and Cu, a pressure of 10 t cm^− 2 and a pressing time of 8 min have been found optimum. It has also been shown that the spark parameters selected are crucial for uniform volatilization. Electron probe micrographs of the burning spots and the analytical signal magnitude showed that a rather hard spark at 100 Hz was optimum. The determination of trace elements in silicon carbide powders is demonstrated using a calibration based on the addition of standard solutions. For Al, Ti, V, Mn and Fe detection limits in the lower µg g^− 1 range can be achieved. Internal standardization with Y in combination with the addition of standard solutions allows relative standard deviations in the range of 4 to 24% for concentration levels of the order of 3 to 350 µg g^− 1.     

A family of ordered mesoporous carbons derived from mesophase pitch using ordered mesoporous silicas as templates

A variety of ordered mesoporous carbons (OMCs) were synthesized using ordered mesoporous silicas (OMSs) as hard templates and the mesophase pitch (MP) as a carbon precursor. The synthesis included the mixing of OMS with MP, the infiltration of OMS with MP at 450–550?°C and the carbonization of MP in OMS/MP composite followed by the dissolution of the OMS template. OMCs with structures of two-dimensional hexagonal arrays of nanorods and three-dimensional arrays of nanospheres were obtained through the replication of silica templates, including large-pore SBA-15, KIT-6, large-pore FDU-12 and SBA-16. In particular, 2-D hexagonal array of carbon nanorods (CMK-3 carbon) with (100) interplanar spacing of ～13 nm as well as an array of carbon nanospheres arranged in the face-centered cubic structure with the unit-cell parameter of 33 nm were successfully prepared. The specific surface areas of the resulting carbons were up to 400 m²/g, and the total pore volumes were up to 0.43 cm³/g, with the highest values achieved when the MP infiltration temperature was 500?°C. The OMCs exhibited narrow mesopore size distributions. As inferred from XRD, the frameworks of OMCs featured semi-graphitic structures even though moderate carbonization temperature (850?°C) was employed.     

有序介孔碳的简易模板法制备与电化学电容性能研究

0引言电化学电容器(Electrochemical Capacitors),又称为超级电容器(supercapacitors)是介于传统电容器和二次电池之间的一种新型储能装置,它具有循环寿命长、比容量高、能快速充放电等优点[1,2]。近年来随着电子、电气设备的日趋小型化以及电动汽车工业的不断发展,作为后备电源和记忆候补装置的超级电容器日益引起了人们的广泛关注。碳材料由于具有成本低、比表面积大、导电性优良、制备电极工艺简单等特点,一直是超级电容器电极材料的首选。其中,活性炭是最早采用的多孔电极材料,其比表面积可高达2500￣3000m·2g-1[3]。然而,活性炭材料…     

Chitosan modified ordered mesoporous silica as micro-column packing materials for on-line flow injection-inductively coupled plasma optical emission spectrometry determination of trace heavy metals in environmental water samples

A novel adsorbent of chitosan chemically modified ordered mesoporous silica was synthesized and employed as a solid phase extraction (SPE) material for flow injection (FI) micro-column preconcentration on-line coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) determination of trace heavy metals V, Cu, Pb, Cd and Hg in environmental water samples. The factors affecting separation and preconcentration of target heavy metals such as pH, sample flow rate and volume, eluent concentration and volume, interfering ions were investigated. Under the optimized experimental conditions, an enrichment factor of 20 and sampling frequency of 10 h⁻¹ were obtained. The detection limits of the method for V, Cu, Pb, Cd and Hg were 0.33, 0.30, 0.96, 0.05 and 0.93 ng mL⁻¹, and the relative standard deviations (RSDs) were 2.8%, 6.7%, 1.8%, 4.0% and 5.3% (n = 7, C = 10 ng mL⁻¹), respectively. The adsorption capacities of chitosan modified ordered mesoporous silica for V, Cu, Pb, Cd, and Hg were found to be 16.3, 21.7, 22.9, 12.2 and 13.5 mg g⁻¹, respectively. In order to validate the developed method, a certified reference material of GSBZ50009-88 environmental water sample was analyzed and the determined values were in good agreement with the certified values. The proposed method has also been applied to the determination of trace heavy metals in natural water samples with satisfactory results.     

Direct determination of impurities in high purity silicon carbide by inductively coupled plasma optical emission spectrometry using slurry nebulization technique

A novel method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni and Ti in high purity silicon carbide (SiC) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) was described. The various sizes of SiC slurry were dispersed by adding dispersant polyethylene imine (PEI). The stability of slurry was characterized by zeta potential measurement, SEM observation and signal stability testing. The optimal concentration of PEI was found to be 0.5 wt% for the SiC slurry. Analytical results of sub-μm size SiC by the slurry introduction were in good accordance with those by the alkaline fusion method which verified that determination could be calibrated by aqueous standards. For μm size SiC, results of most elements have a negative deviation and should be calibrated by the Certified Reference Material slurry. Owing to a rather low contamination in the sample preparation and stability of the slurry, the limits of detection (LODs), which are in the range of 40-2000 ng g⁻¹, superior to those of the conventional nebulization technique by ICP-OES or ICP-MS.     

Influence of Hierarchical Porosity in Carbon Material on Electrocatalytic Property of Supported Pt Nanoparticles

The influence of hierarchical porosity on electrocatalytic property was investigated with Pt nanoparticles supported on three types of carbon materials, namely, commercial Vulcan XC-72, ordered mesoporous carbon CMK-5, and hierarchical carbon aerogel (HCA). The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in H₂SO₄ and CH₃OH solution. Pt/HCA presented superior performance with higher peak current (7.5 mA·cm⁻²) and electrochemical active area (128.0 m²·g⁻¹). This could be attributed to the carbon aerogel with continuous but nonperiodical mesopore structure, which facilitated dispersion of Pt nanoparticles and mass transport around reactants and products.     

Surface functionalization of ordered mesoporous carbons--a comparative study

Hexagonally structured mesoporous carbons C15 and CMK-5 and cubically structured carbon C48 were synthesized using ordered silica SBA-15 and MCM-48 as templates and carbon precursors of different structures. The surfaces of these ordered carbons were chemically functionalized by employing an approach, in which the selected diazonium compounds were in situ generated and reacted with the carbon frameworks of the mesoporous carbons. The aromatic organic molecules containing chlorine, ester, and alkyl groups were covalently attached to the surface of these ordered mesoporous carbons. The presence of functional groups on the modified carbons was confirmed with Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption. The BET-specific surface area and the pore width of ordered carbons were significantly reduced, whereas the primary structure of these ordered carbons and their unit cells were intact. Basically, the density of grafted functional groups is related to the specific surface area of the sample, particularly the surface area of mesopores. The surface functionalization reaction takes place only on the external surface of carbon C15, while it occurs on both of the internal and external surface of CMK-5 carbon with the nanopipe structure. The presence of the micropores in CMK-5 carbon should be responsible for its lower grafting density because the small micropores are inaccessible in the reaction. It was also proposed that the preferred adsorption/reaction in C48 may be related to the observed unsymmetrical degradation of the XRD patterns for the functionalized C48 samples. The chemical modification process considerably reduced the primary mesopores in these ordered carbons by approximately 1-1.5 nm, affording carbons with micropores in the cases of C15 and C48, and mixed micropores and small mesopores in the case of CMK-5. A grafting density of approximately 0.9-1.5 micromol/m(2) was achieved under current research.     

Novel sponge-like molecularly imprinted mesoporous silica material for selective isolation of bisphenol A and its analogues from sediment extracts

Bisphenol A (BPA) imprinted sponge mesoporous silica was synthesized using a combination of semi-covalent molecular imprinting and simple self-assembly process. The molecularly imprinted sponge mesoporous silica (MISMS) material obtained was characterized by FT-IR, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption measurements. The results show that the MISMS possessed a large specific surface area (850.55 m² g⁻¹) and a highly interconnected 3-D porous network. As a result, the MISMS demonstrated a superior specific adsorption capacity of 169.22 μmol g⁻¹ and fast adsorption kinetics (reaching equilibrium within 3 min) for BPA. Good class selectivity for BPA and its analogues (bisphenol F, bisphenol B, bisphenol E and bisphenol AF) was also demonstrated by the sorption experiment. The MISMS as solid-phase extraction (SPE) material was then evaluated for isolation and clean-up of these bisphenols (BPs) from sediment samples. An accurate and sensitive analytical method based on the MISMS–SPE coupled with HPLC–DAD has been successfully established for simultaneous determination of five BPs in river sediments with detection limits of 0.43–0.71 ng g⁻¹ dry weight (dw). The recoveries of BPs for lyophilizated sediment samples at two spiking levels (50 and 500 ng g⁻¹ dw for each BP) were in the range of 75.5–105.5% with RSD values below 7.5%.     

Structural and sorption properties of carbon replicas obtained by matrix carbonization of organic precursors in SBA-15 and KIT-6

We have carried out a comparative study of matrix carbonization of some organic precursors (sucrose, polydivinylbenzene, polyphenol-formaldehyde, polyacrylonitrile, acetonitrile) in SBA-15 and KIT-6 silica mesoporous molecular sieves. We have shown that carbon mesoporous molecular sieves of the CMK-8 type, obtained in KIT-6 mesopores, have better adsorption characteristics due to the features of the three-dimensional cubic structure, the larger pore volume and thickness of the walls of the framework. The maximum micropore volume is observed in CMK-3 and CMK-8, obtained by carbonization of polyphenol-formaldehyde and polydivinylbenzene, while the greatest specific surface area is observed on carbonization of sucrose, where the maximum hydrogen adsorption capacity is achieved at a level of ∼1.4 wt.% (77 K, 1 atm). We show that the mesopore surface coverage by hydrogen in carbon mesoporous molecular sieves increases as the degree of graphitization increases.     

An ordered mesoporous aluminosilicate with completely crystalline zeolite wall structure

An ordered mesoporous aluminosilicate with completely crystalline zeolite pore wall structure, denoted as OMZ-1, was successfully synthesized by recrystallization of SBA-15 using in situ formed CMK-5 as the hard template. The role of carbon material not only serves as a hard template to preserve ordered mesoporous structure but also kinetically controls the crystallization process to form large crystals.     

简易模板法制备有序介孔碳

通过一种简易的模板法制备了有序介孔碳,即硅/P123三嵌段共聚物复合物经硫酸处理后,再加入蔗糖碳源经碳化和除硅处理合成出有序介孔碳。该方法与传统硬模板相比,其合成工序简单,成本更低;与其他简化合成方法相比,避免了由碳源不足而造成的介孔碳有序性低的缺点。通过小角XRD、N2吸脱附和HRTEM对样品及其中间过程进行了表征。结果表明,自晶化过程后,样品在合成的各个时期均保持着有序的介孔结构,当蔗糖添加量为1.5g时合成出的介孔碳材料有序性最高,比表面积和孔容也最高,分别为1261m2·g-1,1.03cm3·g-1。     

Ordered mesoporous carbon as an efficient and reversible adsorbent for the adsorption of fullerenes

An ordered mesoporous carbon, CMK-3, was synthesized using a mesoporous siliceous material, SBA-15, as the template. CMK-3 was characterized and used for the adsorption of fullerenes C60 and C70. It was found that the adsorption capacity of CMK-3 is 4 times higher than that of activated carbon. The adsorption equilibrium isotherms of C60 and C70 on CMK-3 were studied for both single and binary systems. The reversibility of fullerene adsorption on CMK-3 was also explored. The results showed that CMK-3 is an effective and reversible adsorbent for the separation of fullerenes by adsorption.