A facile templated synthesis of functional nanocarbon materials with well‐defined spherical mesopores is developed using all‐organic porogenic precursors comprised of hairy nanoparticles with nitrogen‐rich polyacrylonitrile shells grafted from sacrificial cross‐linked poly(methyl methacrylate) cores (xPMMA‐g‐PAN). Such shape‐persistent all‐organic nanostructured precursors, prepared using atom transfer radical polymerization (ATRP), assure robust formation of template nanostructures with continuous PAN precursor matrix over wide range of compositions, and allow for removal of the sacrificial template through simple thermal decomposition. Carbon materials prepared using this method combine nitrogen enrichment with hierarchical nanostructure comprised of microporous carbon matrix interspersed with mesopores originating from sacrificial xPMMA cores, and thus perform well as CO2 adsorbents and as supercapacitor electrodes. 相似文献
Mesoporous carbons were synthesized from polyacrylonitrile (PAN) using ordered and disordered mesoporous silica templates and were characterized using transmission electron microscopy (TEM), powder X-ray diffraction, nitrogen adsorption, and thermogravimetry. The pores of the silica templates were infiltrated with carbon precursor (PAN) via polymerization of acrylonitrile from initiation sites chemically bonded to the silica surface. This polymerization method is expected to allow for a uniform filling of the template with PAN and to minimize the introduction of nontemplated PAN, thus mitigating the formation of nontemplated carbon. PAN was stabilized by heating to 573 K under air and carbonized under N2 at 1073 K. The resulting carbons exhibited high total pore volumes (1.5-1.8 cm3 g(-1)), with a primary contribution of the mesopore volume and with relatively low microporosity. The carbons synthesized using mesoporous templates with a 2-dimensional hexagonal structure (SBA-15 silica) and a face-centered cubic structure (FDU-1 silica) exhibited narrow pore size distributions (PSDs), whereas the carbon synthesized using disordered silica gel template had broader PSD. TEM showed that the SBA-15-templated carbon was composed of arrays of long, straight, or curved nanorods aligned in 2-D hexagonal arrays. The carbon replica of FDU-1 silica appeared to be composed of ordered arrays of spheres. XRD provided evidence of some degree of ordering of graphene sheets in the carbon frameworks. Elemental analysis showed that the carbons contain an appreciable amount of nitrogen. The use of our novel infiltration method and PAN as a carbon precursor allowed us to obtain ordered mesoporous carbons (OMCs) with (i) very high mesopore volume, (ii) low microporosity, (iii) low secondary mesoporosity, (iv) large pore diameter (8-12 nm), and (v) semi-graphitic framework, which represent a desirable combination of features that has not been realized before for OMCs. 相似文献
Silica particles with different morphology have been functionalized with carbon shells by different synthetic procedures. In the key step, the bare silica particles are functionalized by a specific cationic surface polymerization with furfuryl alcohol (FA). The polyfurfuryl alcohol (PFA)/silica hybrid particles have been also post-functionalized with maleic anhydride (MSA) by a Diels Alder reaction. Simultaneously occuring cationic polymerization of FA and sol-gel process with TEOS has been used for producing interpenetrating carbon-silica hybrid materials. The thermal transformation of the PFA component on silica into the carbon phase has been carried out under argon atmosphere in a temperature range from 700°C to 900°C. The influence of the former morphology of the silica on the homogenity of the resulting carbon layer is shown by zetapotential measurements and electron microscopic investigations. 相似文献
Summary: Organic‐inorganic hybrid materials consisting of nanosized silica particles with surface grafted PS or PS‐b‐PMMA were synthesized using ATRP. These hybrid materials were used in the fabrication of highly‐ordered isoporous membranes. Optical characterization revealed that the membranes consisted of hexagonally ordered pores of uniform size. The combination of an open pore structure and high surface area makes isoporous membranes into materials of high interest in fields as biotechnology and photonics.
Image from optical microscope of hybrid nanoparticle membrane of SiO2‐g‐PS with hexagonally‐ordered pores. 相似文献
Based on a molecularly imprinted organic‐silica hybrid‐based stir bar, a pre‐treatment methodology was developed for enrichment of nicosulfuron in aqueous samples. The molecularly imprinted organic‐silica hybrid‐based coating on the outer surface of a glass stir bar was prepared by in‐situ polymerization using nicosulfuron as a template molecule, α‐methacrylic acid as a functional monomer, methacryloxypropytrimethoxysilane as a cross‐linker in the mixture of acetonitrile and trichloromethane (V/V, 7.5:1). To achieve the selective extraction of the target analyte from aqueous samples, several main parameters, including extraction time, pH value and contents of inorganic salt in the sample matrix were investigated. Evidence was also presented by the scanning electronic microscopic images of the imprinted and non‐imprinted stir bars. Then, the extraction efficiency of the stir bar was tested with separate experiments and competitive sorption experiments. These results showed that using six sulfonylureas as substrates the molecularly imprinted organic‐silica hybrid‐based stir bar gave high selectivity for the template, nicosulfuron compared to the non‐imprinted organic‐silica hybrid‐based stir bar. This sorption extraction was coupled to liquid chromatography ultraviolet detection allowing the determination of nicosulfuron from tap water. The method showed good recoveries and precision, 96.0% (RSD 2.7%, n=3) for tap water spiked with 0.125 nmol (25.00 mL sample), suggesting that the stir bar can be successfully applied to the pre‐concentration of nicosulfuron in real aqueous samples. 相似文献
We present a simple and fast method for the synthesis of polyacrylates-silica hybrid materials with significantly low volume shrinkages through the sol-gel reactions of tetraethyl orthosilicate and 2-hydroxyethyl methacrylate along with the free-radical polymerization of the acrylate monomer. The volume shrinkage from the processible sol to the final product was about 6–20% for the hybrid materials having the silica contents up to about 50 wt-%. As a result of the low shrinkage, crack-free, transparent and monolithic hybrid materials of relatively large sizes can be prepared within a short period of 6 to 12 hours. The formation of covalent bonding between the organic and the silica components in the hybrid materials was demonstrated. Thermal stability of the polyacrylate component in the hybrid materials were found to be higher than that of the bulk polymer. Other vinyl polymers such as poly(methyl methacrylate) and polyacrylonitrile have also been incorporated into the inorganic silica sol-gel matrix by using this method. 相似文献
A pyridinium‐based immobilized ionic liquid type multifunctional hybrid silica monolith was prepared by the in situ polymerization of 3‐chloropropyl‐silica matrix and 4,4′‐dipyridyl for hydrophilic interaction CEC. The obtained hybrid monolith possessed of high stable skeletal microstructures with obviously hydrophilic retention mechanism under ACN content >50% in the mobile phase. Strong and stable anodic EOF could be observed under a broad pH range from pH 3.0 to 9.0. Due to the immobilized dipyridyl groups bonded to the silica matrix surface, the resulting hydrophilic hybrid monolith possessed multiple separation interactions including hydrogen bond, π–π, and anion exchange. Excellent separations of various polar analytes including electroneutral phenols, charged acid nucleotides, and basic analytes were successfully achieved. The highest column efficiencies up to 120 000, 164 000, and 106 000 plates/m were obtained for nucleotides, nucleic acid bases, and nucleosides and nicotines, respectively. These results demonstrated that the dipyridyl‐immobilized ionic liquid functionalized hybrid monolith possessed highly mechanical stability and good chromatographic performance for hydrophilic interaction electrochromatography. 相似文献
Tin anode materials have attracted much attention owing to their high theoretical capacity, although rapid capacity fade is commonly observed mainly because of structural degradation resulting from volume expansion. Herein, we report a versatile strategy based on a basil seed inspired design for constructing a monodisperse core–shell Sn@C hybrid confined in a carbon matrix (Sn basil seeds). Analogous to the structure of basil seeds soaked in water, Sn basil seeds are used to tackle the volume expansion problem in lithium‐ion batteries. Monodisperse Sn cores are encapsulated by a thick carbon layer, which thus lowers the electrolyte contact area. The obtained Sn basil seeds are closely packed to construct a framework that supplies fast electron transport and provides a reinforced mechanical backbone. As a consequence, an ensemble of this hybrid network shows significantly enhanced lithium‐storage performance with a high capacity of 870 mAh g?1 at a current density of 0.4 A g?1 over 600 cycles. After the intense cycling, the Sn cores transform into ultrafine nanocrystals with sizes of 3–6 nm. The structural and morphological evolution of the Sn cores can reasonably explain the gradual increase in the capacity and the long‐term cycling ability of our Sn basil seeds. 相似文献