Feng Zan

Shanghai University, Shanghai, Shanghai Shi, China

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Publications (6)21.65 Total impact

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    ABSTRACT: In this paper, we systematically investigated the conjugation of quantum dots (QDs) with certain biomolecules using capillary electrophoresis (CE) and fluorescence correlation spectroscopy (FCS) methods. Commercial QDs and aqueous-synthesized QDs in our lab were used as labeling probes, certain bio-macromolecules, such as proteins, antibodies, and enzymes, were used as mode samples, and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysulfo-succinimide (Sulfo-NHS) were used as linking reagents. We studied the effects of certain factors such as the isoelectric points (pIs) of bio-macromolecules and buffer pH on the bioconjugation of QDs, and found that the pIs of bio-macromolecules played an important role in the conjugation reaction. By the optimization of the buffer pH some proteins with different pIs were efficiently conjugated with QDs using EDC and Sulfo-NHS as linking agents. Furthermore, we on-line investigated the kinetic process of QDs-bioconjugation by FCS and found that the conjugation reaction of QDs with protein was rapid and the reaction process almost completed within 10 min. We also observed that QDs conjugated with proteins were stable for at least 5 days in phosphate buffer. Our work described here will be very helpful for the improvement of the QDs conjugation efficiency in bioapplications.
    Electrophoresis 07/2012; 33(13):1987-95. · 3.26 Impact Factor
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    ABSTRACT: In this study, we report for the first time a one-pot approach for the synthesis of new CdSeTeS quaternary-alloyed quantum dots (QDs) in aqueous phase by microwave irradiation. CdCl(2) was used as a Cd precursor during synthesis, NaHTe and NaHSe were used as Te and Se precursors and mercaptopropionic acid (MPA) was used as a stabilizer and source of sulfur. A series of quaternary-alloyed QDs of different sizes were prepared. CdSeTeS QDs exhibited a wide emission range from 549 to 709 nm and high quantum yield (QY) up to 57.7 %. Most importantly, the quaternary-alloyed QDs possessed significantly long fluorescence lifetimes > 100 ns as well as excellent photostability. Results of high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX) and powder X-ray diffraction (XRD) spectroscopy showed that the nanocrystals possessed a quaternary alloy structure with good crystallinity. Fluorescence correlation spectroscopy (FCS) showed that QDs possessed good water solubility and monodispersity in aqueous solution. Furthermore, CdSeTeS QDs were modified with alpha-thio-omega-carboxy poly(ethylene glycol) (HS-PEG-COOH) and the modified QDs were linked to anti-epidermal growth factor receptor (EGFR) antibodies. QDs with the EGFR antibodies as labeling probes were successfully applied to targeted imaging for EGFR on the surface of SiHa cervical cancer cells. We believe that CdSeTeS QDs can become useful probes for in vivo targeted imaging and clinical diagnosis. Copyright © 2012 John Wiley & Sons, Ltd.
    Luminescence 06/2012; · 1.27 Impact Factor
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    ABSTRACT: Gold nanoparticles (GNPs) are attractive alternative optical probes and good biocompatible materials due to their special physical and chemical properties. However, GNPs have a tendency to aggregate particularly in the presence of high salts and certain biological molecules such as nucleic acids and proteins. How to improve the stability of GNPs and their bioconjugates in aqueous solution is a critical issue in bioapplications. In this study, we first synthesized 17 nm GNPs in aqueous solution and then modified them with six thiol compounds, including glutathione, mercaptopropionic acid (MPA), cysteine, cystamine, dihydrolipoic acid, and thiol-ending polyethylene glycol (PEG-SH), via a Au-S bond. We systematically investigated the effects of the thiol ligands, buffer pH, and salt concentrations of the solutions on the colloidal stability of GNPs using UV-vis absorption spectroscopy. We found that GNPs modified with PEG-SH were the most stable in aqueous solution compared to other thiol compounds. On the basis of the above results, we developed a simple and efficient approach for modification of GNPs using a mixture of PEG-SH and MPA as ligands. These biligand-modified GNPs were facilely conjugated to antibody using 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide and N-hydroxysulfosuccinimide as linkage reagents. We conjugated GNPs to epidermal growth factor receptor antibodies and successfully used the antibody-GNP conjugates as targeting probes for imaging of cancer cells using the illumination of a dark field. Compared to current methods for modification and conjugation of GNPs, our method described here is simple, has a low cost, and has potential applications in bioassays and cancer diagnostics and studies.
    Langmuir 03/2012; 28(9):4464-71. · 4.38 Impact Factor
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    ABSTRACT: In this study, we first synthesized a series of highly fluorescent InP/ZnS core/shell QDs under varied reaction conditions and then systematically investigated the blinking behaviors of QDs by single molecule imaging technique. In the measurement of blinking processes, the PL intensity trajectories of single QDs with different emission peak were recorded by a total internal reflection fluorescence (TIRF) imaging system. We observed that particle size, molar ratio of myristic acid/indium (MA:In), and the overcoating of ZnS shell had significant influence on the blinking behaviors of InP/ZnS QDs. Statistical analysis documented that both the on and off events (mon and moff) followed the power-law distributions P(ton/off) = Bt–mon/off, and the values for mon and moff were in the ranges of 1.3–1.7 and 1.4–1.9, respectively. As the wavelength of emission peak increased from 565 to 646 nm, the on-time fraction changed from 30% to 70%. The QDs prepared under higher MA/In ratio possessed a longer on-time fraction. The optimal overcoating time of the ZnS shell was about 3 h for blinking suppression in this case. Furthermore, we found that UV irradiation of QDs certainly suppressed the off-time fraction by reducing surface traps. We were able to control the blinking behavior of QDs by varying the synthesis parameters, and prepared InP/ZnS QDs with the on-time fraction up to 80% for future biological and photoelectric applications.
    The Journal of Physical Chemistry C 02/2012; 116(6):3944–3950. · 4.84 Impact Factor
  • Feng Zan, Jicun Ren
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    ABSTRACT: In this paper, we describe a simple and efficient approach for synthesis of highly luminescent InP/ZnS core/shell quantum dots (QDs) in gas-liquid phase reaction using zinc phosphide (Zn3P2) as a new phosphorus source and indium(III) myristate as indium precursor. The effects of experimental conditions, such as the ratios of reactants, reaction temperature and overcoating time of ZnS shell, were systematically investigated. We observed that the molar ratio of In:myristic acid (MA) and the overcoating time of ZnS had significant influences on the optical properties of the InP/ZnS core/shell QDs. Under the optimal conditions, we prepared highly photoluminescent InP/ZnS QDs with emission range of 540–660 nm and the quantum yields were about 30–60%. The characterization of high-resolution transmission electron microscopy and X-ray diffraction (XRD) showed that the InP/ZnS QDs had good monodispersity and a nice crystal structure. Furthermore, we observed that the luminescence efficiency of InP/ZnS QDs was significantly improved after UV irradiation in the presence of dithiothreitol. Compared with the commonly used expensive and extremely flammable tris(trimethylsilyl)phosphine (P(TMS)3) as phosphorus precursor, Zn3P2 is a low-cost and stable phosphorus source. Our method is an easy and fast way for large-scale synthesis of highly luminescent InP/ZnS QDs for wide applications in the future.
    Journal of Materials Chemistry 01/2012; 22(5):1794-1799. · 6.63 Impact Factor
  • Feng Zan, Jicun Ren
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    ABSTRACT: In this paper, we described a simple approach for aqueous synthesis of highly luminescent ZnSe(S) alloyed quantum dots (QDs) in the presence of 3-mercaptopropionic acid as stabilizers using zinc chloride and NaHSe as precursors. The synthesis conditions were systematically investigated. We observed that the pH value of the Zn precursor solution had significant influence on the optical properties and the structure of the as-prepared ZnSe(S) QDs. The optimal pH value and molar ratio of Zn(2+) to HSe(-) were 12.0 and 25 : 1 respectively. Under the optimal conditions, we prepared highly photoluminescent ZnSe(S) QDs at up to 31% quantum yield (compared with Rhodamine 6G). The characterization of HRTEM and XRD showed that the ZnSe(S) QDs had good monodispersity and nice crystal structure. The fluorescence life time spectra demonstrated that ZnSe(S) QDs had a long lifetime in contrast to fluorescent dyes. Compared with the currently used organometallic approach, our method was 'green', the reaction condition was mild and the as-prepared ZnSe(S) QDs were water-soluble. More importantly, our method was low cost, and was very suitable for large-scale synthesis of highly luminescent ZnSe(S) QDs for the future applications.
    Luminescence 09/2009; 25(5):378-83. · 1.27 Impact Factor