Colloid imprinted carbons

Fang, B., Kim, J.H., Yu, J.S. Colloid-imprinted carbon with superb nanostructure as an efBcient cathode electrocatalyst support in proton exchange membrane fuel cell. Electrochem. Commun. 10(4), 659-662 (2008)... 

FIGURE 2.30 Schematic illustration of the synthesis of colloid-imprinted carbons. (From Li, Z. and Jaroniec, M. Chem Mater 15 1327-1333, 2003. With permission.)... 

B. Fang, M.-S. Kim, S.-H. Flwang and J.-S. Yu, Colloid-imprinted carbon with tailored nanostructure as an unique anode electrocatalyst support for formic acid oxidation. Carbon 46,2008, 876-883. 

Li Z., Jaroniec M., Lee Y. J. and Radovic L. R., Hi surface area graphitized carbon with uniform mesopores synthesised by colloidal imprinting method. Chem. Commun. (2002) pp. 1346-1347. 

Jaroniec s group reported the synthesis of mesoporons carbons by using Lichrosper Si 100 silica spherical particles as tanplates and a synthetic meso-phase pitch or acrylonitrile as the carbon precursors [229]. Such carbons possess mesoporosity with negligible microporosity. Recently, a colloidal imprinting (Cl) method for prodncing mesoporous carbons was also described by Jaroniec and coworkers, as schematically illustrated in Fignre 2.30 [66-68]. The key to this... 

Preparing carbons with hierarchical pore structure is done by impregnation of preformed macropo-rous structures, such as silica colloids, with the carbon precursor gels, followed by precursor carbonization and macropore template dissolution. Although in hard-templated carbons, two particle sizes of the hard template are simultaneously required for the colloidal imprinting method the soft-templating method makes this procedure much simpler and broadens the selection of templates for the larger mesopores and macropores. 

To use this method for the preparation of imprinted colloids, Whitcombe et al. applied it during the shell preparation. They synthesized a copolymer network shell consisting of poly(EGDMA-co-cholesteryl (4-vinyl)phenyl carbonate) using a variety of different seed particles to build the polymer core [26]. The seed particles used were 30-45 nm in diameter and the imprinted p(EGDMA-co-CVPC) shell resulted to a thickness of about 15 nm (Fig. 3). The specific BET surface area of the core-shell particles was typically 80 m2 g... 

As can be seen from Figure 2 the adsorption branch of this isotherm exhibits two distinct steps that reflect the capillary condensation inside smaller or larger mesopores at relative pressures about 0.79 and 0.9, respectively. The condensation in the relative pressure range of 0.9S-0.99S reflects condensation in secondary mesopores or small macropores, which resulted from the imprinting of agglomerates of colloidal particles. To our knowledge, this kind of isotherm has not been reported for porous carbon materials. The pore size distribution for this mesoporous carbon shown in Figure 3 exhibits two distinct peaks located about 11 nm and 24 nm, which correspond to the particle size of Bindzil 30/360 and Ludox AS-40 colloidal silicas, respectively. 

With time and improved synthetic protocols, larger templates (fuUerenes, dendrimers, nanoparticles, colloids, micelles, lipid bilayers, self-assembled block copolymers, oligonucleotides, DNA and proteins) have been imprinted [14] and the choice of matrices has expanded to liquid crystal polysiloxanes, carbon networks, zeolites, layered aluminophosphates and colloidal crystals, though organic polymer networks remain the dominant imprint casting medium [14]. 

Our previous papers [15,16] and the current work show that die imprinting of mesophase pitch particles with colloidal silica is an efficient technique to prepare mesoporous carbons with uniform spherical pores as well as carbons with bimodal pore size distributions. These carbons exhibit negligible amount of micropores, which can be further eliminated during graphitization process. If micropores are need, they can be created by controlled oxidation analogous to that used in the preparation of activated carbon fibers. The possibility of tailoring the size of uniform spherical mesopores is of great importance for catalysis, adsorption and other advanced applications such as die manufacture of hi -quaiity electrochemical double-layer capacitors, fuel cells and lidiium batteries. 

Zhang, Z. Hu, Y. Zhang, H. Yao, S. (2010a). Novel layer-by-layer assembly molecularly imprinted sol-gel sensor for selective recognition of clindamycin based on Au electrode decorated by multi-wall carbon nanotube. Journal of Colloid and Interface Science, 344,158-164. 

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