Chun Cao

Anhui Normal University, Wu-hu-shih, Anhui Sheng, China

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Publications (6)15.71 Total impact

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    ABSTRACT: A method for determination of vitamin B1 has been developed that is based on the enhancement effect of vitamin B1 on the luminescence of water-soluble CdTe nanorods modified with thioglycolic acid and cysteine. The effect of variables including the size of the nanorods on the enhancement of luminescence have been investigated. A preliminary mechanistic study showed that the passivating action of vitamin B1 on the surface of the CdTe nanorods is likely to be responsible for the enhancement. Interferences by shortwave fluorescence are effectively eliminated because measurements are performed in the near-infrared. Due to the near-infrared measurement character, the fluorescence interference of vitamin B2 can be effectively eliminated. Under the optimum conditions, the extent of luminescence enhancement is proportional to the concentration of vitamin B1 in the range from 0.1 to 3.0 μmol L−1 and the detection limit is 0.03 μmol L−1. The relative standard deviation for 2.0 μmol L−1 vitamin B1 is 1.3% (n = 6). The method is highly sensitive and selective, avoids the sample treatment needed in other procedures, and can be applied to the determination of vitamin B1 in real samples with satisfactory results.
    No preview · Article · Apr 2010 · Microchimica Acta
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    ABSTRACT: A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5x10(-8) and 8.0x10(-6)mol L(-1) with a detection limit of 6.0x10(-9)mol L(-1). The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.
    No preview · Article · Mar 2010 · Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy
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    ABSTRACT: CdS quantum dots (QD) were capped with SiO2 via a microemulsion method for reducing the toxicity and imparting the biocompatibility of the CdS QD. The resulting CdS/SiO2 core/shell nanoparticles (NP) showed an improved water-solubility and stability even in pH 4.0 acidic medium. Their fluorescence could be effectively enhanced in the presence of bovine serum albumin (BSA), due to the passivation effect of BSA on the surface of the NP. Furthermore, the concentration dependence of the fluorescence intensity obeys the Langmuir-type binding isotherm. Thus a novel fluorescence enhancement method for the determination of BSA has been developed using the less-toxic CdS/SiO2 core/shell NP as probes. Under optimal conditions, the linear range of calibration curve is 0.6–30 µg·mL−1, and the detection limit is 0.18 µg·mL−1. Compared with the water-soluble CdS NP without SiO2 shell, the CdS/SiO2 core/shell NP exhibited slightly lower fluorescence response to BSA as well as other coexisting substances, such as heavy and transition metals, due to the inhibition of SiO2 shell. The proposed method was applied to the quantification of BSA in synthetic and serum samples with satisfactory results.
    No preview · Article · Sep 2009 · Chinese Journal of Chemistry
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    ABSTRACT: Glutathione-capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous medium. Their interactions with proteins, especially three heme-containing proteins, were investigated over a broad pH range. At 6.0 < pH < 8.0, the fluorescence of the GSH-CdTe QDs can be effectively quenched by cytochrome c (Cyt. c) and hemoglobin, respectively. At pH > 8.0, only cytochrome c quenched the fluorescence of the GSH-CdTe QDs, and no significant fluorescence changes were observed for hemoglobin or other proteins. Based on the distinct fluorescence response, a novel method has been developed for the selective determination of cytochrome c using GSH-CdTe QDs as the fluorescence probe at pH 9.0. Under optimum conditions, the linear range of the calibration curve is from 3.2 × 10−8 to 2.4 × 10−6 mol L−1 and the detection limit is 3.0 × 10−9 mol L−1. The method has been applied to the determination of cytochrome c in three synthetic and real samples, and satisfactory results were obtained with QDs through selecting the proper pH value.
    No preview · Article · Jun 2009 · Microchimica Acta
  • Yun-Sheng Xia · Chun Cao · Chang-Qing Zhu
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    ABSTRACT: Four sizes of water-soluble thiol-capped CdTe quantum dots (QDs) have been synthesized and used to investigate the photoluminescence (PL) responses to Ag+ ions. For small particles, the CdTe QDs exhibit PL enhancement in the presence of lower concentration of Ag+ but show obvious quenching with the further increase of Ag+; for larger particles, however, PL of CdTe QDs is quenched all the time with the Ag+ addition, no PL enhancement is observed. Mechanism study shows that small QDs with more traps on the particle surface are effectively passivated by initial adsorbed Ag+, which accounts for the PL enhancement observed; after the initial traps are saturated, the excess Ag+ facilitates nonradiative recombination, resulting in PL quenching. For larger particles, the nonradiative recombination dominates the whole process even for the lower concentration of Ag+, due to the fewer traps on the QD surface. Compared with larger particles, the small CdTe QDs are more suitable for sensing Ag+ because of the more sensitive and selective PL response. To our best knowledge, this is the first systematical study on the interaction of Ag+ with different-sized CdTe QDs.
    No preview · Article · Jan 2008 · Journal of Luminescence
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    ABSTRACT: Three different size CdTe quantum dots (QDs) capped by 3-mercaptopropionic acid (MPA) have been prepared in aqueous solutions, and their interactions with Cu2+ and Hg2+ have been investigated. The opposite size-dependent fluorescence quenching of CdTe QDs by Hg2+ and Cu2+ was observed: Hg2+ quenched smaller particles more efficiently than larger ones while larger particles were more markedly quenched by Cu2+. Based on the different size responses, Hg2+ and Cu2+ were respectively detected with high sensitivity and selectivity, for the first time, using the QDs with different sizes but the same components and capping ligands.
    No preview · Article · Dec 2007 · Chinese Journal of Chemistry