Nijuan Sun

Peking University, Peping, Beijing, China

Are you Nijuan Sun?

Claim your profile

Publications (13)38.58 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate that Mo6S9−xIx nanowires (MoSI NWs) enable the detection of proteins with cytochrome c as a model protein using UV–vis spectrometry. The association of cytochrome c with the nanowires was verified by scanning electroctron microscopy, X-ray photoelectron, light scattering and micro-FTIR spectroscopies. Our results show that MoSI NWs is a promising nanostructure material for the development of ultrasensitive sensors for detecting proteins. The new MoSI NW derived amplification bioassay is expected to provide a straightforward and effective strategy for protein analysis and biosensor construction.
    Progress in Natural Science: Materials International. 01/2013; 23(3):326–330.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrochemistry of double-wall carbon nanotubes (DWCNTs) encapsulating C60 (C60@DWCNT) have been studied by preparing a C60@DWCNT modified electrode, and three pairs of reversible electro-reduction waves corresponding to electron transfer reactions of C60 inside DWCNTs have been obtained in a mixed solvent of toluene and acetonitrile (4:1, v:v) containing tetrabutylammonium cation as supporting electrolyte, which indicates that DWCNTs act as molecular wires to allow electrical communication between the underlying electrode and the redox-active guest C60. The influencing factors on the electrochemistry of C60@DWCNT modified electrodes have been investigated. The results suggest that the voltammetric behavior of C60@DWCNT is dependent on the nature of the supporting electrolyte and the solvent system. In addition, spectral characterization of the C60@DWCNT modified electrodes before and after electrochemical scanning reveals interaction between C60 and DWCNT and verifies the reduction of C60 encapsulated in DWCNTs. C60 molecules inside DWCNTs retains their redox activity, and can also act as an electron-transfer mediator to electrocatalyze the reduction of halohydrocarbon.
    Carbon. 10/2012; 50(12):4401–4408.
  • Source
    Electrochemistry Communications 01/2012; · 4.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Electrochemical properties of a novel nanohybrid material, ferrocene-filled double-walled carbon nanotubes (Fc@DWNTs), have been successfully investigated for the first time by preparing different kinds of Fc@DWNTs modified glassy carbon electrodes. One pair of surface-confined redox waves corresponding to the couple of Fc/Fc+ is obtained, indicating Fc encapsulated in DWNTs retains electrochemical activity. Significantly differing from those of ferrocene-filled single-walled carbon nanotubes (Fc@SWNTs), Fc@DWNTs shows a specific electrochemical behavior, typically exhibiting thin-layer electrochemical characteristics at low scan rates, whereas diffusion-confined characteristics at high scan rates. The results indicate that the novel nanohybrid material possessing excellent electrochemical properties may have possible applications in constructing specific chemical and biological sensors.
    Journal of Nanoscience and Nanotechnology 05/2011; 11(5):4034-8. · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate the use of a novel electrochemical sensing platform based on aptamer conjugated Mo(6)S(9-x)I(x) nanowires (MoSI NWs) for the highly sensitive detection of the blood clotting enzyme thrombin. MoSI NWs nanowires were self-assembled on a gold electrode to which thrombin binding aptamers were covalently attached. The modification and immobilization steps of the electrodes were characterised by cyclic voltammetry along with high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The platform is based on the creation of a self-assembled MoSI MW layer via the sulfur-gold affinity followed by the creation of MoSI-thiolated aptamer conjugates via the sulfur-sulfur affinity. Using this system, sensitive quantitative detection of thrombin is realized by monitoring differences of differential pulse voltammetric responses of electrostatically trapped [Ru(NH(3))(6)](3+) cations to the aptamer before and after thrombin binding. The sensitivity limit for the detection of thrombin is 10 pM. This value is 10-fold better than all currently reported one step label free electrochemical strategies. Given the direct label free nature of the approach and the simplicity of the electronic detection, the aptamer conjugated MoSI NWs biosensor appears well suited for implementation in portable point of care microdevices directed at the rapid and sensitive detection of proteins and pathogens.
    Biosensors & bioelectronics 02/2010; 26(5):1853-9. · 5.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: C121 and C121/didodecyldimethylammonium bromide (DDAB) film modified electrodes have been constructed and their electrochemistry has been studied. In the acetonitrile solution containing 0.1M tetrabutylammonium perchlorate, the C121 films show three couples of relatively stable redox peaks corresponding to three two-electron transfer processes involving reduction of two fullerene units in the dimers. In an aqueous solution containing 0.1M tetrabutylammonium bromide, the C121 films display an irreversible reduction peak, whereas the C121/DDAB films display two couples of quasi-reversible redox peaks with the splitting first peak, and the C121/DDAB films have good reversibility and stability in the aqueous solution due to existence of DDAB. All of these experimental results indicate that voltammetric behaviors of the C121 films are different from those of C60 films due to different structures though C121 is carbon-bridged C60 dimer, and the common characteristics are that their electrochemical behaviors are dependent on the nature of solvent and cation of supporting electrolyte. Furthermore, electrocatalysis of H2O2 at the C121/DDAB films was explored in the aqueous solution, which indicates that C121 is a good electron-transfer mediator.
    Journal of Electroanalytical Chemistry - J ELECTROANAL CHEM. 01/2009; 629(1):152-157.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate a novel and highly sensitive electrochemical detection of estrone based on an immunosensor platform, composed of bioassembled nanocircuits of Mo 6S 9- x I x nanowires (MoSI NWs) covalently connected to anti-estrone antibodies. The one-step, label-free, and quantitative detection of estrone is realized by employing the [Ru(NH 3) 6] (3+/2+) redox ions to sense anti-estrone antibody and estrone interactions. The MoSI NWs/anti-estrone antibody nanocircuit architectures provide an amplification and conductive pathway for the specific electrochemical sensing of estrone hapten. A detection limit of 1.4 pg x mL (-1) was achieved in contrast to previous electrochemical techniques in which the sensitivity was limited to the nanomolar range.
    Analytical Chemistry 06/2008; 80(10):3593-7. · 5.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Well-defined gold nanobelts as well as unique gold nanocombs made of nanobelts were readily synthesized by the reduction of HAuCl4 with ascorbic acid in aqueous mixed solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the anionic surfactant sodium dodecylsulfonate (SDSn). Single-crystalline gold nanobelts grown along the <110> and <211> directions were prepared in mixed CTAB-SDSn solutions at 4 and 27 degrees C, respectively. Furthermore, single-crystalline gold nanocombs consisting of a <110>-oriented stem nanobelt and numerous <211>-oriented nanobelts grown perpendicularly on one side of the stem were fabricated by a two-step process with temperature changing from 4 to 27 degrees C. It was proposed that the mixed cationic-anionic surfactants exerted a subtle control on the growth of gold nanocrystals in solution due to the cooperative effect of mixed surfactants. This synthetic strategy may open a new route for the mild fabrication and hierarchical assembly of metal nanobelts in solution. The obtained gold nanobelts showed good electrocatalytic activity toward the oxidation of methanol in alkaline solution; in particular, the electrode modified with the nanobelts obtained at 27 degrees C exhibited an electrocatalytic activity considerably higher than normal polycrystalline gold electrode. Moreover, the gold nanobelts were used as the surface-enhanced Raman scattering (SERS) substrate for detecting the enhanced Raman spectra of p-aminothiophenol (PATP) molecules, and the gold nanobelts obtained at 4 degrees C exhibited an unusual larger enhancement of the b2 modes relative to the a1 modes for the adsorbed PATP molecules.
    Langmuir 02/2008; 24(3):991-8. · 4.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hierarchical, three-fold symmetrical, single-crystalline gold dendrites were synthesized by the reaction between a zinc plate and a solution of HAuCl 4 in the ionic liquid [BMIM][PF 6 ]. The unique dendritic gold nanostructures show a three-order hierarchy (i.e., a three-fold symmetrical <111>-oriented trunk, three groups of trident-like <111>-oriented branches grown on the trunk, and many <111>-oriented nanorod leaves grown on the branches symmetrically), indicating an interesting fractal growth. According to the investigation on the growth process of the gold dendrites, it was proposed that gold nuclei nanocrystals first formed on the zinc substrate through a direct surface reaction and that the subsequent crystal growth preferentially took place on the preformed gold crystals through a primary cell reaction, leading to the formation of the final hyperbranched dendrites under nonequilibrium conditions. In contrast, AuZn alloy dendrites consisting of aggregated primary nanoparticles were produced when the ionic liquid solution was replaced by an aqueous solution. It was proposed that the significantly lowered ion diffusivity and reaction rate in the ionic liquid medium could largely contribute to the formation of the pure single-crystalline gold dendrites. Moreover, electrocatalytic measurements performed in alkaline solution suggested that the obtained dendritic gold nanostructures exhibited good electrocatalytic activity toward the oxidation of methanol, which might be related to the special three-order hierarchical architectures.
    Chemistry of Materials - CHEM MATER. 01/2008; 20(12).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hierarchical, two-dimensional (2D), disc-like networks consisting of crossed single-crystalline Bi2S3 nanorods have been synthesized via a novel 2D-template-engaged topotactic transformation process, which involves the formation of intermediate BiOCl single-crystalline discs and their subsequent chemical transformation into disc-like Bi2S3 nanofabrics. The transformation process from (001)-oriented BiOCl discs to disc-like Bi2S3 nanorod networks has been followed by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED) and X-ray diffraction (XRD), which revealed that the close matching between the lattice constants of the c-axis for orthorhombic Bi2S3 and the a- or b-axis for tetragonal BiOCl could be responsible for the preferential growth of [001]-oriented Bi2S3 nanorods on the top faces of (001)-oriented BiOCl discs along the two perpendicular [100] and [010] directions of BiOCl. The diameter of the Bi2S3 nanorods involved in the networks can be adjusted by changing the bismuth ion concentration in the reaction solution; moreover, an increase of the HCl concentration would prevent the formation of precursor BiOCl discs, leading to the formation of Bi2S3 nanostructures with varied morphologies. Charge–discharge curves and cyclic voltammograms of the obtained Bi2S3 nanostructures were measured to investigate their electrochemical hydrogen storage behaviors. It was found that the disc-like Bi2S3 nanorod networks could electrochemically charge and discharge with a capacity of 162 mA h g−1 at room temperature, indicating their potential applications in hydrogen storage, high-energy batteries, and catalytic fields.
    Advanced Functional Materials 01/2008; 18(8):1194-1201. · 9.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report a method to prepare composites based on carbon nanotubes (CNTs) and CeO2 nanoparticles (NPs). The CeO2 NPs were attached to CNTs by hydrothermal treatment of Ce(OH)4/CNT mixture in NaOH solution at 180°C. It was found that larger CeO2 NPs were formed in the presence of CNTs. Grain size of CeO2 NPs in the composites can be reduced when NaNO3 was added in the hydrothermal process. Electrochemical characterizations have shown that the composites possess a specific capacity between those of CNTs and CNTs mechanically mixed with CeO2. These CeO2/CNT composites could serve as promising anode materials for Li-ion batteries.
    Journal of Solid State Chemistry 01/2008; 181(10):2620-2625. · 2.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Electrochemical properties of a new nanomaterial ferrocene (Fc) peapod, Fc-filled single-walled carbon nanotubes (Fc@SWNTs), have been investigated in an aqueous solution in detail by preparing different kinds of Fc@SWNTs-modified glassy carbon electrodes (Fc@SWNTs/GCE and Fc@SWNTs-gel/GCE). One pair of surface-confined redox waves corresponding to the couple of Fc/Fc+ is obtained, which indicates that Fc encapsulated inside SWNTs retains electrochemical activity. The Fc@SWNTs-gel/GCE shows better electrochemical reversibility due to the existence of room temperature ionic liquid (RTIL). Furthermore, it shows excellent mediation of H2O2 based on Fc/Fc+ used as electron-transfer mediators for oxidation of H2O2 to O2 and reduction to H2O, suggesting specific properties of Fc@SWNTs due to a combination of Fc and SWNTs. The interaction between Fc and SWNTs is also characterized by UV-vis-NIR spectrometry and Raman spectrometry. A Fc@SWNTs-based sensor for H2O2 with a determination limit of 5 microM is fabricated, and it shows good stability and reproducibility. This work not only demonstrates that the Fc peapod is a new kind of functional nanomaterial but also appears promising in constructing novel chemical and biosensors and fuel cells.
    Analytical Chemistry 10/2006; 78(17):6050-7. · 5.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Redox processes of C60@SWNT and C70@SWNT modified electrodes corresponding to electron transfer reactions of C60 and C70 inside single-wall carbon nanotubes have been firstly observed. Three pairs of reversible electro-reduction waves have been obtained in acetonitrile containing tetrabutylammonium cation as supporting electrolyte. The influencing factors on electrochemistry of fullerene peapod modified electrodes have been investigated. The results suggest that voltammetric behavior of C60@SWNT or C70@SWNT is dependent on the nature of the supporting electrolyte and the solvent system.
    Electrochemistry Communications - ELECTROCHEM COMMUN. 01/2005; 7(11):1148-1152.