Yan Shi

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (24)108.69 Total impact

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    ABSTRACT: In this paper, we constructed a fluorescence resonance energy transfer (FRET) system between amino-functionalized carbon dots (C-dots) and gold nanoparticles (AuNPs). In this system, C-dots were treated as energy donors, while AuNPs were treated as energy acceptors. We optimized some important factors including incubation time, AuNPs concentration and media pH, which would affect the efficiency of the FRET system. Under the optimized experimental conditions, melamine could be detected based on fluorescence intensity of C-dots. We could get a linear relationship between 50 nM and 500 nM and the detection limit was 36 nM. The proposed method was applied to the determination of melamine in milk samples with satisfactory results. Compared with previous reports, the proposed method manifested great advantages including high sensitivity, short analysis time, low cost and ease of operation.
    No preview · Article · Oct 2014 · Sensors and Actuators B Chemical
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    ABSTRACT: In this paper the fabrication of CuO nanowires (CuO NWs) by a facile two-step method is reported. Cu(OH)2 nanowires (Cu(OH)2 NWs) on a copper surface were prepared at room temperature by a simple solution-based procedure, and subsequent calcinations of Cu(OH)2 NWs led to the formation of CuO NWs. The morphologies and structures of Cu(OH)2 NWs and CuO NWs were characterized by scanning electron microscopy and X-ray diffraction. Electrochemical measurements showed that the CuO NWs modified Cu electrode exhibited good electrocatalytic behavior for the detection of glucose with a wide linear range from 2 μM to 3.56 mM (R2 = 0.9984), a low detection limit down to 0.05 μM, and a high sensitivity of 1886.3 μA mM−1 cm−2. The sensor also displayed a high selectivity, an acceptable reproducibility, an excellent long-term stability and good repeatability. Moreover, the as-prepared sensor has great potential in practical applications.
    No preview · Article · Jul 2014 · RSC Advances
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    ABSTRACT: In this study, a facile method to sensitively detect melamine and highly improve the peroxidase-like activity of bare gold nanoparticles (Au NPs) at the same time is proposed for the first time. It is interesting to find that the addition of melamine could improve the peroxidase-like activity of Au NPs. By coupling with 3,3',5,5'-tetramethlybenzidine (TMB)-H2O2 chormogenic reaction, a novel method for colorimetic detection of melamine is developed. The detection limit of this method is as low as 0.2nM with the help of UV-vis spectroscopy and 0.5µM by naked-eye observation, both which are far below the US food and Drug Administration estimated melamine safety limit of 20µM. In addition, the present method is successfully applied for the detection of melamine in raw milk and milk powder. More importantly, the proposed method could also improve the peroxidase-like activity of Au NPs, which may not only provide a new approach to develop effective nanomaterials-based mimetic enzyme, but also irradiative to develop new applications for Au NPs in varieties of cost-effective and simple sensors in medicine, biotechnology and environmental chemistry.
    No preview · Article · Apr 2014 · Biosensors & Bioelectronics
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    ABSTRACT: NiCo2O4 nanoflake composites were synthesized by using DNA molecules as templates via in-situ assembly and subsequent thermal treatment. The obtained NiCo2O4 composites were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray powder diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Cyclic voltammetry and chronopotentiometry tests were used to investigate the electrochemical properties of the as-prepared composites. Superior performances with a good specific capacitance (1468 F/g), an extraordinary rate capability (64.9% capacity retention at 16 A/g) and an excellent cycling stability (85.5% retention after 5000 cycles) were achieved. The DNA templates were introduced as the binder of NiCo2O4 and as the conductive matrix to facilitate the electron transmission between electroactive materials and outside current collectors, which resulted in the excellent electrochemical performances of the synthesized NiCo2O4 composites. It is believed that our NiCo2O4 nanocomposites could be used as effective electrode materials for supercapacitors.
    No preview · Article · Mar 2014 · Electrochimica Acta
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    ABSTRACT: In this report, it was found that the Napierian logarithm of the electrical resistance is proportional to the reciprocal thickness for the platinum nanofilms. A new method was proposed to determine the thickness of platinum nanofilm simply by measuring its electrical resistance, which is fast and cost effective.
    No preview · Article · Jan 2014 · Analytical methods
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    ABSTRACT: In this study, a facile method to sensitively detect melamine and highly improve the peroxidase-like activity of bare gold nanoparticles (Au NPs) at the same time is proposed for the first time. It is interesting to find that the addition of melamine could improve the peroxidase-like activity of Au NPs. By coupling with 3,3′,5,5′-tetramethlybenzidine (TMB)–H2O2 chormogenic reaction, a novel method for colorimetic detection of melamine is developed. The detection limit of this method is as low as 0.2 nM with the help of UV–vis spectroscopy and 0.5 µM by naked-eye observation, both which are far below the US food and Drug Administration estimated melamine safety limit of 20 µM. In addition, the present method is successfully applied for the detection of melamine in raw milk and milk powder. More importantly, the proposed method could also improve the peroxidase-like activity of Au NPs, which may not only provide a new approach to develop effective nanomaterials-based mimetic enzyme, but also irradiative to develop new applications for Au NPs in varieties of cost-effective and simple sensors in medicine, biotechnology and environmental chemistry.
    No preview · Article · Jan 2014 · Biosensors & Bioelectronics
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    ABSTRACT: Here, we report a new and facile method to prepare silver nanoparticles (Ag NPs) film for surface-enhanced Raman scattering (SERS)-based sensing. The porous Ni foam was used as a template to generate high quality of Ag NPs by seed-mediated growth of metallic nanoparticles. The preparation process is very economic and environment-friendly, can achieve the recovery of the raw materials. We found that the type of silver-plating solution and the growth time are two key factors to determine the magnitude of SERS signal enhancement. Using rhodamine 6G (R6G) and 4-animothiophenol (4-ATP) as probe molecules, the created Ag NP films exhibited relatively high enhancement ability, good stability, and well reproducibility. The synthesized SERS-active substrate was further used to detect melamine molecules, an illegal additive in infant milk powder, and the limitation of detection can reach 1 μM.
    Preview · Article · Oct 2013 · Applied Surface Science
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    ABSTRACT: In this work, we proposed a facile, environmentally friendly and cost-effective assay for melamine with BSA-stabilized gold nanoclusters (AuNCs) as a fluorescence reader. Melamine, which has a multi-nitrogen heterocyclic ring, is prone to coordinate with Hg(2+). This property causes the anti-quenching ability of Hg(2+) to AuNCs through decreasing the metallophilic interaction between Hg(2+) and Au(+). By this method, detection limit down to 0.15µM is obtained, which is approximately 130 times lower than that of the US food and Drug Administration estimated melamine safety limit of 20µM. Furthermore, several real samples spiked with melamine, including raw milk and milk powder, are analyzed using the sensing system with excellent recoveries. This gold-nanocluster-based fluorescent method could find applications in highly sensitive detection of melamine in real samples.
    No preview · Article · Sep 2013 · Biosensors & Bioelectronics
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    ABSTRACT: A sensitive hydrogen peroxide (H2O2) sensor was fabricated based on a Prussian blue @ gold nanocomposite (PB@Au). Au nanoparticles (Au NPs) were first electrodeposited on a glassy carbon electrode (GCE) to increase the conductivity and to catalyze the chemical deposition of PB. Electrochemical measurements showed that the PB@Au modified electrode exhibited good electrocatalytic behavior for the detection of H2O2 with a wide linear range from 2 μM to 8.56 mM (R2 = 0.9980), a low detection limit down to 0.1 μM (S/N = 3), and a high sensitivity of 39.72 μA mM−1. The sensor also displayed a good anti-interference ability, an acceptable reproducibility, an excellent long-term stability and good repeatability. The desirable recoveries achieved in disinfected fetal bovine serum verified that the developed sensor could have a potential use in the detection of H2O2 in real samples. Moreover, the operating simplicity and low expense of the fabrication made the as-prepared electrode attractive.
    No preview · Article · Sep 2013 · RSC Advances
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    ABSTRACT: This study demonstrates a cocaine sensing method employing graphene oxide (GO), gold nanoparticles and a structure switching aptamer, which can fold into a three-way junction in the presence of cocaine. On the observation of gold nanoparticles (Au NPs) induced graphene oxide fluorescence quenching, a structure switching aptamer of cocaine was introduced as the linker between the two parts. Firstly, two fragments of a cocaine aptamer were immobilized covalently onto GO and Au NPs, respectively. Then when the three-way junction formed, the Au NPs were drawn near to the GO surface and induced a fluorescence intensity decrease. The limit of detection was 0.1 μM for cocaine in purified water, and well defined results were also obtained in biological fluids and the specificity experiment, which expands the feasibility of the as-prepared sensor for practical applications.
    No preview · Article · Aug 2013 · The Analyst
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    ABSTRACT: Electrochemical reduction and electrodeposition are two effective methods for the preparation of new nanomaterials for electrochemical sensing. In this work, the reduced graphene oxide-nickel nanoparticles composite (RGO-NiNPs) was synthesized using both methods mentioned above. The fabrication process was simple and easily performed. Then, the RGO-NiNPs composite was characterized by SEM, EDS, and XRD. Furthermore, for the strong catalytic ability of the high-valent oxyhydroxide species (NiOOH) formed in alkaline media, the composite was used as the matrix for nonenzymatic detection of glucose. Comparing with NiNPs modified glassy carbon electrode (NiNPs/GCE), the RGO-NiNPs/GCE showed better sensitivity and stability. A low detection limit of 0.1 µM with a wide linear range from 2 µM to 2.1 mM (R=0.996) was obtained.
    No preview · Article · Apr 2013 · Electroanalysis
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    ABSTRACT: Water safety is one of the most pervasive problems afflicting people throughout the world. Microcystin, a hepatotoxin produced by cyanobacteria, poses a growing and serious threat of water safety. According to World Health Organization (WHO), the limit of content of microcystin-LR (MC-LR) in drinking water is as low as 1 μg/L; it is thus necessary to explore a sensitive method for the trace detection of microcystins (MCs). Based on the observation of gold nanoparticles (Au NPs) induced graphene oxide (GO) fluorescence quenching, a reliable biosensor was developed here for microcystins detection. MCs could be attached on Au NPs through the interaction with single strand-DNA (ss-DNA) modified on Au NPs, which formed Au-DNA-MCs complexes. These MCs in the complexes could be immunologically recognized by the antibodies adsorbed on GO sheets, as a result, Au NPs were close enough to quench the photoluminescence of GO by the fluorescence resonance energy transfer (FRET). The fluorescence intensity decreased with the increase of MCs as more Au NPs linked onto GO surface. The limit of detection was 0.5 and 0.3 μg/L for microcystin-LR and microcystin-RR (MC-RR), respectively, which satisfies the strictest standard of WHO. Well defined results were also obtained in natural lake water and the specificity experiment. The antibody used here could recognize Adda group, the conservative part of MCs, which allowed the biosensor to detect both single toxin and the total content of MCs existing in the water sample.
    No preview · Article · Jun 2012 · Biosensors & Bioelectronics
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    ABSTRACT: A biofunctional hybrid composite was constructed by assembling hydroxyapatite (HA) onto carboxylic group-functionalized carbon nanofibers (FCNFs). The FCNFs was obtained from acid treatment of carbon nanofibers (CNFs) which were synthesized by the combination of electrospinning and thermal treatment processes. The obtained carbon nanofibers–hydroxyapatite composite (FCNFs–HA) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and FTIR spectroscopy. Cytochrome c (Cyt c) was successfully immobilized in this three-dimensional FCNFs–HA composite and the electron transfer rate constant (ks) was evaluated to be 3.66s−1 according to Laviron's equation. And the surface coverage (Γ*) was estimated to be 8.1×10−10molcm−2. Cyt c immobilized in FCNFs–HA composite exhibited a good electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2). The catalytic current is linear to the H2O2 concentration in the range of 2.0μM to 8.7mM (r=0.9996; n=28), and the detection limit was 0.3μM based on the criterion of a signal-to-noise ratio of 3.
    No preview · Article · Dec 2011 · Sensors and Actuators B Chemical
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    ABSTRACT: This review highlights recent advanced researches on the assembly of various metallic nanostructures by oligonucleotide and plasmidDNA. The obtained DNA–nanoconjugates show many unique and attractive properties, while this review focuses on their properties related to SERS detection. The applications of DNA-based assemblies in SERS detections were fully commented upon, for the detection ofDNA, proteins, small molecules, and metallic ions. Finally, a concluding section is given, which covers the challenges and scope for DNA assembled nanostructures as well as for the DNAassemblies-related SERS detections.
    No preview · Article · Oct 2011 · Journal of Materials Chemistry
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    ABSTRACT: Ni(OH)2 nanoplates were successfully synthesized and in situ assembled on reduced graphene oxide (RGO) nanosheets by a simple one-pot method. This RGO-Ni(OH)2 nanocomposite was characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). TEM images showed that the composite was round and that leaf-shaped nanoplates with a diameter of about 150 nm assembled on the RGOnanosheets. EDX, XRD, Raman and XPS characterization proved that the constituent parts of the composite were Ni(OH)2 and RGO. Moreover, the amount of Ni(OH)2 assembled on the RGO could be adjusted simply by changing the volume of NiCl2 added to the reactant mixture. For the strong catalytic ability of the high-valent oxydroxide species (NiOOH) formed in alkaline media, the RGO-Ni(OH)2 nanocomposite was used as the matrix for the non-enzymatic detection of glucose. A low detection limit of 0.6 μM with a wide linear range from 2 μM to 3.1 mM (R = 0.9987) could be obtained. The operating simplicity and low expense of fabrication make this Ni(OH)2-based electrode attractive in sensor construction.
    No preview · Article · Oct 2011 · Journal of Materials Chemistry
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    ABSTRACT: A sensitive hydrogen peroxide (H2O2) sensor was fabricated based on graphene–Pt (GN–Pt) nanocomposite. The GN–Pt was synthesized by photochemical reduction of K2PtCl4 on GNs, and characterized by atomic force microscope (AFM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical investigations indicated that the GN–Pt exhibited a high peak current and low overpotential towards the reduction of H2O2. The GN–Pt modified glass carbon electrode displayed a wide linear range (2–710μM), low limit of detection (0.5μM) and good selectivity for detection of H2O2 with a much higher sensitivity than that of Pt nanoparticles or graphene modified electrode.
    No preview · Article · Oct 2011 · Electrochemistry Communications
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    ABSTRACT: A novel electrochemical sensor based on the silver decorated carbon nanotube is reported here for the accurate and rapid determination of hydrogen peroxide. The hybrid nanostructure was synthesized separately and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The high focus on the silver-based hydrogen peroxide sensor spurred us to investigate the determination of the electrocatalytic activity towards hydrogen peroxide. The as-prepared electrochemical senor exhibited well-defined response to the reduction of hydrogen peroxide. The detection limit of hydrogen peroxide was found to be 1.6μM, which was lower than the certain enzyme-based biosensor.
    No preview · Article · Jun 2011 · Journal of electroanalytical chemistry
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    ABSTRACT: Au nanocages (AuNCs) were synthesized by a simple one-pot method without the use of any solid templates or Au seeds. The structure of the as-prepared AuNCs was characterized by SEM, TEM, EDS and XRD. For their good electrochemical properties and large surface-to-volume ratio, the AuNCs were utilized to modify glassy carbon electrode (GCE) directly for nonenzymatic detection of H2O2. Electrochemical experiments showed that the AuNCs displayed high electrocatalytic activity towards the reduction of H2O2 and obtained a wide linear range from 0.5 μM to 5.8885 mM (R = 0.9993) with a detection limit down to 0.1 μM (S/N = 3). The sensitivity of the H2O2 sensor was as high as 273.83 μA mM−1 cm−2. The sensor also exhibits good anti-interference ability to electroactive molecules, including uric acid, ascorbic acid, glucose, ethanol, and glycine. Moreover, the operating simplicity and low expense of fabrication made this electrode more attractive.Highlights► Au nanocages (AuNCs) were synthesized by a simple one-pot method. ► The structure of the as-prepared AuNCs was characterized by SEM, TEM, EDS and XRD. ► The AuNCs displayed high electrocatalytic activity towards the reduction of H2O2. ► The sensor has a wide linear range with a detection limit down to 0.1 μM (S/N = 3). ► The sensitivity of the H2O2 sensor was as high as 273.83 μA mM−1 cm−2.
    No preview · Article · Jun 2011 · Journal of electroanalytical chemistry
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    ABSTRACT: A superhydrophobic substrate that combines the superhydrophobic condensation effect and high enhancement ability of silver nanoparticle coated zinc oxide nanorods array (Ag@ZnO) is explored for surface enhanced Raman scattering (SERS). The effects of water contact angle and droplet volume on the final SERS signal intensity are also investigated for the first time. Our results indicate the superhydrophobic substrate could exhibit 3-fold signal enhancement more than the ordinary hydrophilic Ag@ZnO substrate due to the superhydrophobic condensation effect. This signal amplification effect is affected by the water contact angle and water droplet volume on the substrate, i.e., (1) the higher the contact angle is, the higher the SERS signal is; (2) the SERS intensity fluctuates as the droplet volume increases, and proper volume, not the largest one, should be chosen to achieve a stronger signal. Most importantly, this superhydrophobic substrate with high signal reproducibility is successfully applied to detect small molecules such as adenine and melamine, with the detection limits of 1 order of magnitude less than those on the hydrophilic Ag@ZnO substrate. It is expected this superhydrophobic SERS substrate can be widely used in the trace analysis in the future.
    No preview · Article · Apr 2011 · The Journal of Physical Chemistry C
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    ABSTRACT: Microcystin-LR (MC-LR) is one of the hepatotoxins produced by cyanobacteria in the eutrophicated fresh water. In this work, the minor groove binding mode of MC-LR to plasmid DNA was explored by using UV and fluorescence spectra, and the binding characteristics of MC-LR for plasmid DNA were calculated via the fluorescence quenching of ethidium bromide (EB) and mole ratio method. Furthermore, atomic force microscopy (AFM) was used to observe DNA morphology change in the presence of MC-LR. With the increasing concentration of MC-LR, circle DNA strands twined gradually to rod condensates. The possible reason for the condensation might be the masking of the electrostatic repulsion between DNA double strands by MC-LR. The present study might provide useful information for the pathopoiesis mechanism of MC-LR. More, because the condensation of DNA could affect the progresses of gene expression and protein transcription, it may implicate another trend to explore the nosogenesis of MC-LR.
    No preview · Article · Feb 2011 · Biomacromolecules