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Graphitic carbon nitride (g-C 3 N 4 ) based ternary composite photocatalyst (g-C 3 N 4 /SiO 2 -Au NFs) was prepared using Au nanoparticles (NPs) decorated SiO 2 nanofibers (SiO 2 -Au NFs) as a support by employing a heat treatment with a mixture of urea powder and SiO 2 -Au NFs. The resulting Au NPs with the mean diameter of about 13 nm were evenly dispersed on the g-C 3 N 4 /SiO 2 -Au NFs. In addition, the thin g-C 3 N 4 nano-layers were found to be uniformly grown on the g-C 3 N 4 /SiO 2 -Au NFs as determined by electron microscopy and elemental mapping image analyses. Comparative studies revealed that the g-C 3 N 4 /SiO 2 -Au NFs showed better photocatalytic activity for the degradation of Rhodamine B (RhB) under visible light than g-C 3 N 4 /SiO 2 NFs, which was prepared by the same process. The photocurrent enhancement of the g-C 3 N 4 /SiO 2 -Au NFs also indicated an enhanced separation of photo-induced electron-hole pairs. In addition, both the g-C 3 N 4 /SiO 2 -Au and g-C 3 N 4 /SiO 2 NFs could be easily precipitated and separated, which resulted from their ultra-long one-dimensional nanostructure. Also, the g-C 3 N 4 /SiO 2 -Au NFs exhibited high stability could be reused with little loss of photocatalytic activity after three recycles. [ABSTRACT FROM AUTHOR]

Abstract: Graphene oxide (GO) sheets are mixed with the aptamer-functionalized CdSe/ZnS quantum dots (QDs). Consequently, the aptamer-conjugated QDs bind to the GO sheets to form a GO/aptamer-QD ensemble, which enables the energy transfer from the QDs to the GO sheets, quenching the fluorescence of QDs. The GO/aptamer–QD ensemble assay acts as a “turn-on” fluorescent sensor for Pb2+ detection. When Pb2+ ions are present in the assay, the interaction of Pb2+ with the aptamer induces a conformational change in the aptamer, leading to the formation of a G-quadruplex/Pb2+ complex. As a result, the QDs that are linked to the G-quadruplex/Pb2+ complex are detached from the GO sheet, which “turns on” the fluorescence of the QDs. This sensor exhibits a limit of detection of 90pM and excellent selectivity toward Pb2+ over a wide range of metal ions. The experiments have provided direct evidence that the fluorescence of QDs is quenched by GO via the nano-metal surface energy transfer (NSET) mechanism rather than the conventional Förster resonance energy transfer (FRET) process. [Copyright &y& Elsevier]

Abstract: Label-free fluorescent detection of Hg2+ has been realized via quenching of fluorescence of graphene oxide (GO). The water-soluble GO sheets, which are functionalized with single-stranded DNA aptamer, exhibit strong fluorescence emission at 600nm under the excitation of 488nm in the absence of Hg2+ ions. When Hg2+ ions appear in the aqueous solution, Hg2+ ions are sandwiched between the hairpin-shaped double-stranded DNA due to the formation of the thymine–Hg2+–thymine complex, which holds the Hg2+ ions in proximity to the surface of GO sheets. As a result, the fluorescence emission of GO is quenched. The present GO-based sensor shows a limit of detection as low as 0.92nM and excellent selectivity toward Hg2+ over a wide range of metal ions. The present work indicates that GO is a promising fluorescent probe for detection of metal ions and biomolecules. [Copyright &y& Elsevier]

Nanoporous graphene sheets were generated through a simple thermal annealing procedure using composites of ferrocene nanoparticles and graphene oxide sheets as precursors in a large scale. The morphology, composition, and formation mechanism of the as-obtained nanoporous graphene sheets were studied complementarily with scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, and other spectroscopy techniques. We found that the density of nanopores on the graphene sheet was determined by the surface distribution of oxygen-containing groups on the original graphene oxide sheets. The coin cells using nanoporous graphene sheets as anode materials showed higher specific lithium ion storage capacity, better discharge/charge rate capability and higher cycling stability when compared to the coin cells with graphene or chemically reduced graphene sheets as anodes. [ABSTRACT FROM AUTHOR]