Xueliang Qiao

Huazhong University of Science and Technology, Wu-han-shih, Hubei, China

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Publications (50)51.2 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: In this study, silver–graphene nanocomposites (SGNs) were successfully prepared by spontaneous reduction of silver ions and graphene oxide. Silver nanoparticles (about 30 nm) with narrow size distribution were distributed randomly on the surface of graphene. Different amounts of SGNs were introduced into silver flakes filled electrical conductive adhesives (ECAs) to study the effect of SGNs on the properties of the ECAs. The results showed that the volume resistivity of the ECAs decreased first and then increased with the increase of weight ratios of SGNs to silver flakes. While the weight ratio of SGNs to silver flakes was 20:80 (%), the resistivity reached the lowest value of 2.37 × 10−4 Ω cm. The lap shear strength decreased with the increase of the content ration of SGNs. And when the weight ratio of SGNs to silver flakes was 20:80 (%), the lap shear strength of ECA was about 10 MPa. According to the thermogravimetric analysis, the addition of SGNs can cause a slight decrease in the thermal stability of the ECA. In summary, SGNs are the promising candidates for the conductivity improvement of silver flakes filled electrical conductive adhesives.
    Journal of Materials Science Materials in Electronics 03/2014; 25(3). · 1.49 Impact Factor
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    ABSTRACT: Compared with other inorganic antibacterial agents, magnesium oxide (MgO) nanopowders exhibit a unique antibacterial mechanism and various advantages in applications, having attracted extensive attention. In this study, MgO nanopowders doped with different ions (Li+, Zn2+ and Ti4+) were synthesized by a sol-gel method, respectively. The structures and morphologies of the as-obtained precursors and nanopowders were characterized and confirmed by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. The influence of three metal ions doping on the antibacterial properties of MgO nanopowders was also investigated by their bactericidal activity against Escherichia coli (E. coli, ATCC 25922) using the broth microdilution method and the agar method. The results show that Li-doped MgO exhibits better antibacterial activity, Zn-doped and Ti-doped MgO display poorer antibacterial activity than pure MgO. It can be concluded that the influence of different ions doping on the antibacterial properties of MgO mainly lies on oxygen vacancies and basicity of nanopowders.
    Applied Surface Science 11/2013; · 2.11 Impact Factor
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    ABSTRACT: Silver nanoparticles (Ag NPs) were prepared via a wet-chemical method in the presence of poly(vinyl pyrrolidone) (PVP) without other reducing agents at room temperature. The influence of the addition of water on the preparation of Ag NPs was investigated. It was found that water addition has a significant influence on the reduction reaction, resulting in changes of shape, size and optical properties of the particles. When large amounts of water were added, the reduction rate was very slow. However, when small amounts of water were used, the opposite effects on the reaction process were observed, initial inhibition effect and final promotion effect. Two main possible mechanisms were proposed to explain the opposite effects of two reaction stages with small amounts of water addition: (1) the initial inhibition effect was induced by free oxygen in water, which would react preferentially with the reducing species in the system; (2) the promotion effect thereafter may be due to the differences of chain extension of PVP molecules and electron transfer rate in ethanol and water.
    Journal of Nanoscience and Nanotechnology 06/2013; 13(6):4084-9. · 1.15 Impact Factor
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    ABSTRACT: The highly pure nano-silver sols were prepared by an electrolysis method using two highly pure silver flakes as electrodes and deionized water as electrolytic solution, and PVP served as stabilizer. The effects of PVP content, electrolytic time and current density on the colloidal silver nanoparticles were researched. The results indicate that as-synthesized particles were spherical about 1∼3 nm in size, and monodispersed and its concentration reached to 130 μg/g under the condition of 5.0 wt% PVP with current density about 1∼2 mA/cm2 for 150 min. Moreover, the nano-silver sol had such an excellent stability that it had not any change though it was placed in dark at room temperature for 6 months.
    Rare Metal Materials and Engineering. 02/2013; 42(2):249–253.
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    ABSTRACT: Magnesium oxide (MgO) nanopowders were synthesised by a sol-gel method with different amounts of ammonium hydroxide (NH3·H2O) and characterised by a combination of thermo gravimetric analysis, X-ray diffraction and transmission electron microscopy. It was found that the structure and morphology of MgO nanopowders can be regulated by the addition of NH3·H2O. When an appropriate amount of NH3·H2O was added into the reaction system, plate-like nanoMgO was obtained. The antibacterial activity of MgO nanoplates was also investigated by the minimum inhibition concentration (MIC) test and bactericidal efficacy against Escherichia coli (E. coli, ATCC 25922). The tested results revealed that the MgO nanoplates have great antibacterial effect with an MIC value of 600 mg/l and the bactericidal rate was about 99.8% at a concentration of 500 mg/l. Furthermore, the effect of NH3·H2O on the structure and morphology of MgO nanopowders and on the growth mechanism are briefly discussed. The hydroxide ion of NH3·H2O, in favour of Mg(OH)2 generation in the precursors, is essential for the formation of MgO nanoplates.
    Micro & Nano Letters 01/2013; 8(9):479-482. · 0.85 Impact Factor
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    ABSTRACT: Large-scale ZnO arrays with a series of morphologies, including nest-like, tower-like, and flower-like samples, have been successfully synthesized by a simple hydrothermal method. The morphologies of the obtained ZnO arrays can be conveniently tailored by changing seeding conditions. The samples were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Their PL spectra depend on their morphologies and defects density. The morphology-dependent photocatalytic performances were studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The nest-like ZnO arrays exhibited higher photocatalytic activity than tower-like and flower-like ZnO arrays.
    Applied Surface Science 12/2012; · 2.11 Impact Factor
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    ABSTRACT: Ag/ZnO heterostructure nanocrystals were successfully synthesized by a novel method using glucose as a reducing agent. The Ag/ZnO heterostructure nanocrystals were composed of ZnO nanorods and metallic Ag nanoparticles (10–30 nm). The formation mechanism of Ag/ZnO heterostructure nanocrystals was clearly discussed. The photocatalytic performance of Ag/ZnO heterostructure nanocrystals was evaluated by analyzing the degradation of methylene blue (MB) under UV illumination. The Ag/ZnO heterostructure nanocrystals showed an enhanced photocatalytic performance, and the optimized Ag content was investigated. Besides, no obvious loss of photocatalytic activity was observed after five cycles, indicating the excellent photostability of Ag/ZnO heterostructure nanocrystals. This synthesis method has great potential for the industrial production of Ag/ZnO heterostructure nanocrystals as photocatalysts.
    Materials Research Bulletin. 11/2012; 47(11):3357–3361.
  • Journal of Materials Science 10/2012; 47(20):7262-7268. · 2.16 Impact Factor
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    ABSTRACT: Silver nanocrystals with controlled particle size were prepared by reduction of silver nitrate with sodium borohydride in the presence of trisodium citrate and then silver nanorods were synthesized by using the nanocrystals as seeds. The aging has obvious influence on the small nanocrystals but little influence on the large nanocrystals, implying different structural defects on the crystal surfaces of the two kinds of nanocrystals. The use of silver nanocrystals prepared by addition of NaBH4 all at once and prepared at 0 °C helps produce the most silver nanorods with maximum aspect ratio. Only the smaller and slightly aged nanocrystals can be used as seeds for the formation of silver nanorods with high aspect ratio. The effects of concerned parameters of silver seeds can be applied to the synthesis of other anisotropic nanomaterials by a seed-mediated growth approach.
    Applied Surface Science 05/2012; 258(15):5909–5913. · 2.11 Impact Factor
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    ABSTRACT: Here we report a facile, surfactant-free and template-free synthesis process of highly uniform dendritic silver nanostructures with high catalytic activity for the reduction of p-nitrophenol. By controlling the concentration of AgNO(3) aqueous solution and the reaction time, various shapes of silver nanodendrites (SNDs) could be obtained easily. The effects of different parameters such as concentrations of the reagents and reaction time on the morphology and structure of as-prepared tree-like nanostructures have also been investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Also, the X-ray photoelectron spectroscopy (XPS) has been used to identify the oxidation state of SNDs. In addition, the catalytic activity of the as-prepared SNDs samples at 200 mM AgNO(3) aqueous solution was evaluated by a redox reaction of p-nitrophenol in the presence of an excess amount of NaBH(4). It was found that the highly symmetrical SNDs with roughly 60-120 nm in stem and branch diameter and 3-12 μm in length obtained after 120 s reaction time do have higher catalytic activity than other SNDs prepared at different reaction time, several times stronger catalytic activity in the sodium borohydride reduction of p-nitrophenol to p-aminophenol, compared to some other silver nanoparticles reported in literature. The crystallinity provided by X-ray diffraction (XRD) analysis indicates that the improvement of the crystallinity is also very crucial for SNDs' catalytic activities. The SNDs are very promising catalytic candidates for the reduction of p-nitrophenol because of easily simple preparation route and high catalytic activity.
    Journal of hazardous materials 03/2012; 217-218:36-42. · 4.14 Impact Factor
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    ABSTRACT: A modified chemical-precipitation method is proposed to synthesize MgO nanopowders with high crystallinity at a low temperature of 400 degrees C using acetic acid as a modifier. The as-obtained intermediates and final products were investigated by Fourier-transformed infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and transmission electron microscopy, respectively. The influence of acetic acid in the MgO preparation process was also investigated by a comparison of the samples without acetic acid, and the mechanism of acetic acid modification is also proposed. The carboxyl group of acetic acid could coordinate with Mg atom in a monodentate mode to form a new organic ligand intermediate Mg(OH)(OCOCH3), which facilitates the thermal decomposition of the intermediate at low temperature and enhances the crystallization of MgO.
    Journal of Nanoscience and Nanotechnology 03/2012; 12(3):1919-23. · 1.15 Impact Factor
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    ABSTRACT: This paper describes a simple solvothermal route to synthesize silver nanoplates by reduction of silver nitrate (AgNO3) with N,N-dimethylformamide. In this approach, ferric chloride (FeCl3) servers as the controlling agent, enabling the control over the concentration of free Ag+ ions in the solution. As the concentration of FeCl3 added to the reaction was increased, the morphologies of silver nanostructures evolved from triangular silver nanoplates to hexagonal silver nanoplates. The structures of these nanoplates were characterized by X-ray diffraction, electron microscopy and electron diffraction. A possible mechanism is proposed to interpret the shape-controlled synthesis of silver nanostructures. Finally, our results suggest that this method provides a convenient way to prepare silver nanostructures with different morphologies.
    Journal of Materials Science Materials in Electronics 01/2012; · 1.49 Impact Factor
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    ABSTRACT: Silver nanostructures have been synthesized through a simple solvothermal method by reducing silver nitrate (AgNO3) with ethylene glycol (EG) and using poly(vinylpyrrolidone) (PVP) as an adsorption agent. Different concentrations of ferric chloride (FeCl3) are added into the solution. It is found that AgCl colloids formed in the initial stage greatly influence the final morphologies of the products. When a low-concentration FeCl3 solution is used, there is a mixture of silver nanoparticles and nanowires. However, when a high-concentration FeCl3 solution (100 μM) is used, large amounts of AgCl colloids appear, resulting in decreasing free Ag+ during initial formation of silver seeds and slowly releasing of Ag+ to the solution in the subsequent reaction. This leads to the formation of silver nanowires. Furthermore, an increase in the concentration of FeCl3 from 100 to 300 μM results in the synthesis of silver nanowires with larger sizes. In addition, Fe(III) is reduced to Fe(II) form which in turn reacts with and removes adsorbed atomic oxygen from the surface of silver seeds. In this case, uniform silver nanowires can be obtained.
    Journal of Materials Science Materials in Electronics 01/2011; 22(1):6-13. · 1.49 Impact Factor
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    ABSTRACT: Nano-silver loaded montmorillonite (Ag-MMT) was prepared by ion-exchange and then a UV-photoreduction two-step approach was applied. The silver content in Ag-MMT determined by Volhard method was about 6.4 wt%. The morphology and structure of as-synthesized Ag-MMT were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the Ag nanoparticles were spherical and their diameters were about 15–20 nm. Moreover, the structure of MMT did not change. The minimum inhibition concentration (MIC) of Ag-MMT was 100×−6 and the sterilizing efficiency (SE) of Ag-MMT was approximately 100% against Escherichia coli ATCC 11229 (E. coli). In addition, the slow release property of silver in Ag-MMT was also demonstrated.
    Journal of Materials Science & Technology - J MATER SCI TECHNOL. 01/2011; 27(8):685-690.
  • Dapeng Chen, Xueliang Qiao, Jianguo Chen
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    ABSTRACT: Silver nanostructures have been synthesized by a simple solvothermal method in the presence of poly(vinylpyrrolidone) (PVP). Typically, different exotic agents (NaOH, KBr, NaCl) are added into the reaction system. The anions (OH−, Cl−, Br−) from these agents can combine Ag+ to form silver salt colloids (AgOH, AgBr and AgCl), decreasing the concentration of free Ag+ in the initial formation of silver seeds. However, different release rates of Ag+ from these colloids to the solution in the subsequent reaction may play different roles in the growth of silver seeds. The as-prepared silver nanostructures were characterized by UV–vis absorption spectrum, X-ray diffraction (XRD) and field emission scanning electron microscope (FSEM). It is found that silver nanostructures with various shapes can be obtained by the addition of different exotic agents. Finally, our work provides a simple route to synthesize silver nanostructures with controllable morphologies.
    Journal of Materials Science Materials in Electronics 01/2011; · 1.49 Impact Factor
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    ABSTRACT: Silver nanostructures have been synthesized via a simple solvothermal method by adding sodium sulfide (Na2S) into the solution. The morphologies of products are controlled by the concentration of Ag2S formed in the initial stage. A low-concentration Ag2S (12.5 ~ 50 μM) acts as the catalysis, leading to the formation of silver nanocubes with controllable sizes. However, a high-concentration Ag2S (100 μM) mainly acts as the controlling agent. It facilitates the synthesis of silver nanowires. Reaction conditions, the reaction temperature and the molar ratio of the repeating unit of PVP to AgNO3 (R), have also been investigated. A possible mechanism is proposed to interpret the synthesis of silver nanocubes and nanowires. Finally, our results indicate that this strategy provides a simple route to prepare silver nanocubes with adjustable sizes.
    Journal of Materials Science Materials in Electronics 01/2011; · 1.49 Impact Factor
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    ABSTRACT: Silver nanowires have been successfully synthesized via a simple solvothermal method by adding sodium sulfide (Na(2)S) into the solution. The Ag(2)S colloids produced in the initial stage help reduce the concentration of free Ag(+) ions in the initial formation of silver seeds and subsequently release Ag(+) ions to the solution. Otherwise, there is no oxidative etching owing to the absence of oxygen. In these cases, silver nanowires are grown preferentially. Furthermore, silver nanowires with adjustable diameters can be obtained by adjusting the concentration of Na(2)S. Electron microscopy, X-ray diffraction, and absorption spectra have been used to investigate the products, and a mechanism is proposed to interpret the controlled synthesis of silver nanowires. Finally, our results indicate that this approach provides a versatile route to prepare silver nanowires with controllable diameters.
    Journal of Colloid and Interface Science 04/2010; 344(2):286-91. · 3.17 Impact Factor
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    ABSTRACT: Silver nanostructures have been synthesized via a microwave-assisted polyol method by adding sodium sulfide (Na(2)S) into the solution. An interesting morphology evolution can be observed by adjusting the concentration of Na(2)S and the heating power. It is found that the ideal concentration of Na(2)S is 31.25-500 microM for the fast reduction of Ag(+) at 300 W under optimal conditions for producing monodispersed silver nanocubes. When the heating power is increased to 400 W, 62.5-250 microM is the ideal concentration of Na(2)S for the synthesis of silver nanocubes. On increasing the concentration of Na(2)S (>500 microM), a mixture of silver nanowires, nanocubes, bipyramids, and irregular/quasispherical particles is synthesized at 300 and 400 W. In particular, an increase in the concentration of Na(2)S to 750 microM at 400 W leads to the production of a quantity of silver nanowires. In addition, silver nanocubes with controllable sizes can be obtained by changing the concentration of Na(2)S and the heating power. Compared to traditional wet-chemical methods, this method has the advantage of a marked decrease in reaction time to 3.5 min. Finally, our work provides a simple strategy for fabricating silver nanostructures with controllable morphologies and sizes.
    Nanotechnology 01/2010; 21(2):025607. · 3.84 Impact Factor
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    ABSTRACT: Ti-doped magnesium oxide powders were prepared by a chemical coprecipitation technique using magnesium nitrate hexahydrate and titanium tetrabutoxide as starting materials and ammonia hydroxide as precipitator. The influence of titanium doping on the structure and morphology of MgO powders was investigated by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and transmission electron microscopy. The results show that titanium ion (Ti4+) was successfully incorporated into the MgO crystal lattice, and consequently, caused the changing of MgO crystal lattice parameter. However, titanium doping resulted in varied particle sizes, and enhanced slightly the particle aggregation. It is attributed to the difference between the solubility product (Ksp) of the two precursors, Mg(OH)2 and TiO(OH)2, which is one of important factors in the chemical coprecipitation process.
    Materials Characterization 08/2009; 60(8):858-862. · 1.88 Impact Factor
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    ABSTRACT: Silver nanoparticles are considered to apply a silver paste for electrode because of their high conductivity. However, the dispersion of silver nanoparticles in electronically conductive adhesives (ECAs) restricts them used as conductive fillers. A simple method had enabled the synthesis of silver nanoparticles by reducing silver nitrate with ethanol in the presence of poly(N-vinylpyrrolidone) (PVP). Reaction conditions, such as silver nitrate concentration, PVP concentration, reaction time, and reaction temperature, had been studied. Fine dispersion and narrow size distribution of silver nanoparticles were obtained. They were added to ECAs by re-dispersing them in ethanol while it was used as the diluent to adjust the volatility of ECAs, preventing them from the aggregation and increasing the chance to fill the gaps between silver flakes. This proposed process offers the possibility to effectively use these synthesized silver nanoparticles for improving the conductivity of ECAs.
    Journal of Materials Science 01/2009; 44(4):1076-1081. · 2.16 Impact Factor