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ABSTRACT: Graphitized carbon quantum dots (CQDs) were synthesized by a simple hydrothermal process with cetyltrimethylammonium bromide (CTAB) as the starting material and nitric acid as surface oxidant. The photoluminescent quantum yield (QY) of CQDs could be greatly enhanced through surface esterification with glycol. Based on the structure characterization, we proposed that the CQDs consisted of the stack of graphene sheets sized several nanometers and their excitation-dependent photoluminescence (PL) should be attributed to the n→π* transition of CO bond of surface carboxylic groups. And the PL of CQDs was obviously enhanced by the esterification of carboxylic groups, possibly due to the increase of the molecular coplanarity or the rigidity.
Journal of Colloid and Interface Science 01/2011; 356(2):416-21. · 3.07 Impact Factor
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ABSTRACT: Porous titania with bicrystalline (anatase and rutile) framework was successfully synthesized by a facile hydrothermal process using inexpensive and nontoxic organic molecules, EDTA (ethylenediamine-tetra-acetic acid) or its sodium salts as a template, which could be removed from porous titania by the extraction with sodium hydroxide aqueous solution and then easily recovered by acidification. XRD investigation suggested that the ratio of anatase to rutile could be readily tuned by employing different sodium salts of EDTA. All of as-prepared porous titania showed higher activities than the commercial photocatalyst P25 for the degradation of methyl orange (MO), because of the high surface area, bicrystalline phase composition and bimodal porous structures.
Journal of Nanoscience and Nanotechnology 01/2008; 7(12):4339-45. · 1.56 Impact Factor
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ABSTRACT: The effects of cations on the absorption spectra of silver sols have been investigated by the UV-vis spectrometry and TEM. Experiments showed that injection of certain amounts of transition metal cations into silver sols resulted not only in the aggregation of silver nanoparticles but also in the appearance of a new band centered near 510 nm in the absorption spectra of silver sols. However, the new band was not observed in the presence of alkaline earth metal cations or the Mv2+ cations. The peak position of the new band depends on the nature as well as the concentration of metal cations used. Comparing the peak positions of the new bands, it was found that the new band induced by the injection of Cr3+ was red-shifted with respect to those induced by Cu2+, Zn2+, or the Cd2+ cations. It is reasonable that this band near 510 nm should be attributed to the coeffects of the adsorption of metal cations onto the surfaces of silver nanoparticles and the aggregation of silver nanoparticles.
Journal of Colloid and Interface Science 02/2003; 257(2):188-94. · 3.07 Impact Factor
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ABSTRACT: The composite particles of Ag–TiO2 both in a nanocrystal form was prepared by photoreduction of AgNO3 in the rutile colloidal solution. The surface plasmon absorption (SPA) band of the silver clusters supported on the TiO2 nanocrystal was red shift, and a strong surface enhanced Raman scattering (SERS) effect for the composite particles of Ag–nanocrystalline TiO2 was observed. The SERS effect is relating to the red shift phenomenon of SPA band, which could be explained by induced-resonance effect.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.
