Search

An easy and reproducible process which demonstrates a triconstituent co-assembly approach to prepare well-ordered mesoporous polymer-silica and carbon-silica nanocomposites by using resols as a polymer precursor, silicate oligomers as an inorganic precursor, and triblock copolymer F127 as a template is presented. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites.

A new class of macrocyclic metal-N4 complexes [MN4]n (M = Co and Fe) were designed and synthesized based on a triangular ligand. Their unique triangular trinuclear structure provides a high density of active sites and facilitates the reduction of dioxygen via a four-electron pathway. Among them, a [CoN4]3/C catalyst (20 wt %) exhibits high catalytic activity and long-time stability for the oxygen reduction reaction (ORR) in alkaline conditions, superior to the commercial Pt/C catalyst. Such structurally well-defined [MN4]n complexes provide a platform for a new generation of nonprecious metal catalysts (NPMCs) for fuel cell applications. [ABSTRACT FROM AUTHOR]

Highly ordered mesoporous carbon−titania nanocomposites with nanocrystal-glass frameworks have been synthesized via the organic−inorganic−amphiphilic coassembly followed by the in situ crystallization technology. A soluble resol polymer was used as a carbon precursor, prehydrolyzed TiCl 4as an inorganic precursor, and triblock copolymer F127 as a template. The carbon−titania nanocomposites with controllable texture properties and composition can be obtained in a wide range from 20 to 80 wt% TiO 2by adjusting the initial mass ratios. The C−TiO 2nanocomposites with “bricked-mortar”frameworks exhibit highly ordered 2D hexagonal mesostructure and high thermal stability up to 700 °C. The nanocomposites have high surface area (465 m 2g −1) and large pore size (∼4.1 nm). Additionally, the nanocomposites show good performance in degradation of Rhodamine B due to the photocatalytic activity of the titania nanocrystals and the strong adsorptive capacity of the glasslike carbon. [ABSTRACT FROM AUTHOR]

Multicolor photoluminescent graphene quantum dots (GQDs) with a uniform size of ∼60 nm diameter and 2-3 nm thickness were prepared by using unsubstituted hexa-peri-hexabenzocoronene as the carbon source. This result offers a new strategy to fabricate monodispersed GQDs with well-defined morphology. [ABSTRACT FROM AUTHOR]

A high-temperature reductive sulfuration method is demonstrated to synthesize highly ordered mesoporous metal sulfide crystallites by using mesoporous silica as hard templates. H2S gas is utilized as a sulfuration agent to in situ convert phosphotungstic acid H3PW12O40·6H2O to hexagonal WS2 crystallites in the silica nanochannels at 600 °C. Upon etching silica, mesoporous, layered WS2 nanocrystal arrays are produced with a yield as high as 96 wt %. XRD, nitrogen sorption, SEM, and TEM results reveal that the WS2 products replicated from the mesoporous silica SBA-15 hard template possess highly ordered hexagonal mesostructure (space group, p6mm) and rodlike morphology, analogous to the mother template. The S-W-S trilayers of the WS2 nanocrystals are partially oriented, parallel to the mesochannels of the SBA-15 template. This orientation is related with the reduction of the high-energy layer edges in layered metal dichalcogenides and the confinement in anisotropic nanochannels. The mesostructure can be 3-D cubic bicontinuous if KIT-6 (Ia3d) is used as a hard template. Mesoporous WS2 replicas have large surface areas (105-120 m²/g), pore volumes (~0.20 cm³/g), and narrow pore size distributions (~4.8 nm). By one-step nanocasting with the H3PMo12O40·6H2O (PMA) precursor into the mesochannels of SBA-15 or KIT-6 hard template, highly ordered mesoporous MoS2 layered crystallites with the 2-D hexagonal (p6mm) and 3-D bicontinuous cubic (Ia3d) structures can also be prepared via this high-temperature reductive sulfuration route. When the loading amount of PMA precursor is low, multiwalled MoS2 nanotubes with 5-7 nm in diameter can be obtained. The high-temperature reductive sulfuration method is a general strategy and can be extended to synthesize mesoporous CdS crystals and other metal sulfides. [ABSTRACT FROM AUTHOR]