The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Thurston Herricks - One of the best experts on this subject based on the ideXlab platform.

  • single crystal nanowires of platinum can be synthesized by controlling the reaction rate of a polyol process
    Journal of the American Chemical Society, 2004
    Co-Authors: Jingyi Chen, Thurston Herricks, Matthias Geissler
    Abstract:

    Platinum nanowires of ∼100 nm in length and ∼5 nm in diameter have been synthesized by reducing H2PtCl6 with ethylene glycol in the presence of poly(vinyl Pyrrolidone) (PVP) and a trace amount of Fe3+ or Fe2+. The wires were generated at the final stage of the synthesis, which involved the formation of several intermediate species. The Fe3+ or Fe2+ ions had dual functions in the synthesis:  they induced aggregation of Pt nanoparticles into larger structures that served as the nucleation sites, and they greatly reduced the reaction rate and supersaturation level to induce anisotropic growth. The reaction mechanism was studied by X-ray photoelectron spectroscopy (XPS) and UV−vis spectral analysis. The Pt nanowires could be readily separated from the surfaces of the agglomerates by sonication and obtained as pure samples by centrifugation.

  • uniform silver nanowires synthesis by reducing agno3 with ethylene glycol in the presence of seeds and poly vinyl Pyrrolidone
    Chemistry of Materials, 2002
    Co-Authors: Brian T Mayers, Thurston Herricks
    Abstract:

    A solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 30−40 nm, and lengths up to ∼50 μm. The first step of this process involved the formation of Pt (or Ag) nanoparticles by reducing PtCl2 (or AgNO3) with ethylene glycol (EG) heated to ∼160 °C. These Pt (or Ag) nanoparticles could serve as seeds for the heterogeneous nucleation and growth of silver (formed by reducing AgNO3 with EG) because of their close match in crystal structure and lattice constants. In the presence of poly(vinyl Pyrrolidone) (PVP), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios as high as ∼1000. UV−visible spectroscopy, SEM, TEM, XRD, and electron diffraction were used to characterize these silver nanowires, indicating the formation of a highly pure phase, as well as a uniform diameter and bicrystalline structure. Both morphology and aspect ratios of these silver nanostructures could be varie...

  • uniform silver nanowires synthesis by reducing agno3 with ethylene glycol in the presence of seeds and poly vinyl Pyrrolidone
    Chemistry of Materials, 2002
    Co-Authors: Yugang Sun, Thurston Herricks, Brian T Mayers, Yadong Yin, Younan Xia
    Abstract:

    A solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 30−40 nm, and lengths up to ∼50 μm. The first step of this process involved the formation of Pt (or Ag) nanoparticles by reducing PtCl2 (or AgNO3) with ethylene glycol (EG) heated to ∼160 °C. These Pt (or Ag) nanoparticles could serve as seeds for the heterogeneous nucleation and growth of silver (formed by reducing AgNO3 with EG) because of their close match in crystal structure and lattice constants. In the presence of poly(vinyl Pyrrolidone) (PVP), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios as high as ∼1000. UV−visible spectroscopy, SEM, TEM, XRD, and electron diffraction were used to characterize these silver nanowires, indicating the formation of a highly pure phase, as well as a uniform diameter and bicrystalline structure. Both morphology and aspect ratios of these silver nanostructures could be varie...

Changsheng Zhao - One of the best experts on this subject based on the ideXlab platform.

  • hemocompatibility and ultrafiltration performance of surface functionalized polyethersulfone membrane by blending comb like amphiphilic block copolymer
    Journal of Membrane Science, 2014
    Co-Authors: Haiming Song, Fen Ran, Huili Fan, Xiaoqin Niu, Long Kang, Changsheng Zhao
    Abstract:

    While polyethersulfone (PES) represents outstanding oxidative, thermal and hydrolytic stability as well as good mechanical and film-forming properties, the hemocompatibility of PES membrane must be dramatically enhanced to reduce injections of anticoagulants during hemodialysis. In this study, a comblike amphiphilic block copolymer poly (vinyl Pyrrolidone)-block-poly (acrylate-graft-poly (methyl methacrylate))-block-poly-(vinyl Pyrrolidone) (PVP-b-P(AE-g-PMMA)-b-PVP) was synthesized via reversible addition-fragmentation chain transfer polymerization and used to modify PES membrane via a liquid–liquid phase separation technique. The surface structure of the modified membrane were characterized by using X-ray photoelectron spectroscopic analysis, fourier transform infrared and water contact angle measurement. The modified PES membrane showed low hemolysis ratio, improved hydrophilicity, suppressed platelet adhesion and prolonged activated partial thromboplastin time. And the modified membranes showed high PBS solution (or water) flux and good protein anti-fouling properties. The dramatic performance enhancement is attributed to its unique surface architecture, which may be formed by migration and self-assembly of PVP-b-P(AE-g-PMMA)-b-PVP during phase separation. In the surface layer of the modified membrane, PVP chain formed functional brush while PMMA chain embedded in the membrane substrate. The highly branched chains of P(AE-g-PMMA) block endowed the modified membrane with good stability, which has potential to be used in blood purification.

  • biocompatibility of modified polyethersulfone membranes by blending an amphiphilic triblock co polymer of poly vinyl Pyrrolidone b poly methyl methacrylate b poly vinyl Pyrrolidone
    Acta Biomaterialia, 2011
    Co-Authors: Weifeng Zhao, Jie Li, Baihai Su, Changsheng Zhao
    Abstract:

    Abstract An amphiphilic triblock co-polymer of poly(vinyl Pyrrolidone)–b-poly(methyl methacrylate)–b-poly(vinyl Pyrrolidone) (PVP-b-PMMA-b-PVP) was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The block co-polymer can be directly blended with polyethersulfone (PES) using dimethylacetamide (DMAC) as the solvent to prepare flat sheet and hollow fiber membranes using a liquid–liquid phase separation technique. The PVP block formed a brush on the surface of the blended membrane, while the PMMA block mingled with the PES macromolecules, which endowed the membrane with permanent hydrophilicity. After adding the as-prepared block co-polymer the modified membranes showed lower protein (bovine serum albumin) adsorption, suppressed platelet adhesion, and a prolonged blood coagulation time, and thereby the blood compatibility was improved. Furthermore, the modified PES membranes showed good cytocompatibility, ultrafiltration and protein anti-fouling properties. These results suggest that surface modification of PES membranes by blending with the amphiphilic triblock co-polymer PVP-b-PMMA-b-PVP allows practical application of these membranes with good biocompatibility in the field of blood purification, such as hemodialysis and bioartificial liver support.

  • biocompatibility of modified polyethersulfone membranes by blending an amphiphilic triblock co polymer of poly vinyl Pyrrolidone b poly methyl methacrylate b poly vinyl Pyrrolidone
    Acta Biomaterialia, 2011
    Co-Authors: Weifeng Zhao, Fen Ran, Shengqiang Nie, Shudong Sun, Changsheng Zhao
    Abstract:

    An amphiphilic triblock co-polymer of poly(vinyl Pyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinyl Pyrrolidone) (PVP-b-PMMA-b-PVP) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The block co-polymer can be directly blended with polyethersulfone (PES) using dimethylacetamide (DMAC) as the solvent to prepare flat sheet and hollow fiber membranes using a liquid-liquid phase separation technique. The PVP block formed a brush on the surface of the blended membrane, while the PMMA block mingled with the PES macromolecules, which endowed the membrane with permanent hydrophilicity. After adding the as-prepared block co-polymer the modified membranes showed lower protein (bovine serum albumin) adsorption, suppressed platelet adhesion, and a prolonged blood coagulation time, and thereby the blood compatibility was improved. Furthermore, the modified PES membranes showed good cytocompatibility, ultrafiltration and protein anti-fouling properties. These results suggest that surface modification of PES membranes by blending with the amphiphilic triblock co-polymer PVP-b-PMMA-b-PVP allows practical application of these membranes with good biocompatibility in the field of blood purification, such as hemodialysis and bioartificial liver support.

Younan Xia - One of the best experts on this subject based on the ideXlab platform.

  • engraving the surface of electrospun microfibers with nanoscale grooves promotes the outgrowth of neurites and the migration of schwann cells
    Angewandte Chemie, 2020
    Co-Authors: Jiajia Xue, Younan Xia
    Abstract:

    We report a simple method based upon coaxial electrospinning for the fabrication of aligned microfibers engraved with nanoscale grooves to promote neurite outgrowth and cell migration. The success of this method relies on the immiscibility between poly(ϵ-caprolactone) (PCL) and poly(vinyl Pyrrolidone) (PVP) in 2,2,2-trifluoroethanol (TFE) for the generation of PVP/TFE pockets on the surface of a PCL jet. The pockets are stretched and elongated along with the jet, eventually resulting in the formation of nanoscale grooves upon the removal of PVP. The presence of nanoscale grooves greatly enhances the outgrowth of neurites from both PC12 cells and chick embryonic dorsal root ganglia (DRG) bodies, as well as the migration of Schwann cells. The enhancements can be maximized by optimizing the dimensions of the grooves for potential use in applications involving neurite extension and wound closure.

  • functionalization of electrospun ceramic nanofibre membranes with noble metal nanostructures for catalytic applications
    Journal of Materials Chemistry, 2009
    Co-Authors: Eric Formo, Eric Lee, Mustafa Selman Yavuz, Lucas A Lane, Younan Xia
    Abstract:

    This article reports a simple method for functionalizing the surface of TiO2 (both anatase and rutile) and ZrO2nanofibre membranes with Pt, Pd, and Rh nanoparticles. The TiO2membranes were prepared in the form of nonwoven mats by electrospinning with a solution containing both poly(vinyl Pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air to generate anatase (at 510 °C) or rutile (at 800 °C). The ZrO2membranes were fabricated with a solution of poly(vinyl Pyrrolidone) and zirconium acetylacetonate, followed by calcination in air at 550 °C to yield the tetragonal phase. The fibre mats were then immersed in a polyol reduction bath to coat the surface of the nanofibres with Pt, Pd, or Rh nanoparticles of 2–5 nm in size. In addition, the ceramic fibres decorated with Pt nanoparticles could serve as a substrate to grow Pt nanowires ∼7 nm in diameter with lengths up to 125 nm. We subsequently demonstrated the use of Pd-coated anatase fibre membranes as a catalytic system for cross-coupling reactions in a continuous flow reactor. Contrary to the conventional setup for an organic synthesis, a continuous flow system has advantages such as short reaction time and no need for separation. The membrane-based catalytic system can also be fully regenerated for reuse.

  • polyol synthesis of cu2o nanoparticles use of chloride to promote the formation of a cubic morphology
    Journal of Materials Chemistry, 2008
    Co-Authors: Mun Ho Kim, Byungkwon Lim, Eric Lee, Younan Xia
    Abstract:

    We have employed the polyol method to synthesize copper(I) oxide (Cu2O) nanostructures with well-defined shapes and in large quantities. Transmission electron microscopy and X-ray powder diffraction studies show that polycrystalline colloidal spheres could be prepared in high yields by simply reducing copper nitrate with ethylene glycol heated to 140 °C in the presence of poly(vinyl Pyrrolidone). When a small amount of sodium chloride was introduced, single-crystal nanocubes were obtained. In this case, chloride seems to play a pivotal role in controlling the formation of seeds and the growth rates of various crystallographic planes to shape the Cu2O nanostructures into nanocubes. Based on the structural analysis of samples obtained at different growth times, we also proposed a plausible mechanism to account for the formation of these two distinctive morphologies under different conditions.

  • rapid synthesis of silver nanowires through a cucl or cucl2 mediated polyol process
    Journal of Materials Chemistry, 2008
    Co-Authors: Kylee E Korte, Sara E Skrabalak, Younan Xia
    Abstract:

    The presence of various ions has been shown to have a strong impact on the shape and size of silver nanostructures produced via the polyol reduction of AgNO3. Here we report a simple and rapid (reaction time ∼1 h) route to Ag nanowires, in which ethylene glycol serves as the solvent and a precursor to the reducing agent. The reaction could be performed in disposable glass vials, with all the reagents being delivered using pipettes. In addition to the use of poly(vinyl Pyrrolidone) as a stabilizer, copper (I) or copper (II) chloride had to be added to the reaction to reduce the amount of free Ag+ during the formation of initial seeds and scavenge adsorbed oxygen from the surface of the seeds once formed. In doing so, Ag nanowires were grown preferentially.

  • uniform silver nanowires synthesis by reducing agno3 with ethylene glycol in the presence of seeds and poly vinyl Pyrrolidone
    Chemistry of Materials, 2002
    Co-Authors: Yugang Sun, Thurston Herricks, Brian T Mayers, Yadong Yin, Younan Xia
    Abstract:

    A solution-phase approach has been demonstrated for the large-scale synthesis of silver nanowires with diameters in the range of 30−40 nm, and lengths up to ∼50 μm. The first step of this process involved the formation of Pt (or Ag) nanoparticles by reducing PtCl2 (or AgNO3) with ethylene glycol (EG) heated to ∼160 °C. These Pt (or Ag) nanoparticles could serve as seeds for the heterogeneous nucleation and growth of silver (formed by reducing AgNO3 with EG) because of their close match in crystal structure and lattice constants. In the presence of poly(vinyl Pyrrolidone) (PVP), the growth of silver could be directed into a highly anisotropic mode to form uniform nanowires with aspect ratios as high as ∼1000. UV−visible spectroscopy, SEM, TEM, XRD, and electron diffraction were used to characterize these silver nanowires, indicating the formation of a highly pure phase, as well as a uniform diameter and bicrystalline structure. Both morphology and aspect ratios of these silver nanostructures could be varie...

Junyan Gong - One of the best experts on this subject based on the ideXlab platform.

  • high quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly vinyl Pyrrolidone assisted hydrothermal process
    Langmuir, 2006
    Co-Authors: Haisheng Qian, Shuhong Yu, Junyan Gong
    Abstract:

    Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4−9 nm, and microbelts with a width of 250−800 nm and tens of micrometers in length, can be realized by a poly (vinyl Pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4−9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue...

  • high quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly vinyl Pyrrolidone assisted hydrothermal process
    Langmuir, 2006
    Co-Authors: Haisheng Qian, Junyan Gong, Linbao Luo, Linfeng Fei
    Abstract:

    Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4-9 nm, and microbelts with a width of 250-800 nm and tens of micrometers in length, can be realized by a poly (vinyl Pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4-9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue color and nanobelts in gray color by this approach can be well dispersed in water or ethanol, making it possible for further engineering of their surfaces to prepare other hybrid core-shell nanostructures.

Haisheng Qian - One of the best experts on this subject based on the ideXlab platform.

  • high quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly vinyl Pyrrolidone assisted hydrothermal process
    Langmuir, 2006
    Co-Authors: Haisheng Qian, Shuhong Yu, Junyan Gong
    Abstract:

    Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4−9 nm, and microbelts with a width of 250−800 nm and tens of micrometers in length, can be realized by a poly (vinyl Pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4−9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue...

  • high quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly vinyl Pyrrolidone assisted hydrothermal process
    Langmuir, 2006
    Co-Authors: Haisheng Qian, Junyan Gong, Linbao Luo, Linfeng Fei
    Abstract:

    Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4-9 nm, and microbelts with a width of 250-800 nm and tens of micrometers in length, can be realized by a poly (vinyl Pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4-9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue color and nanobelts in gray color by this approach can be well dispersed in water or ethanol, making it possible for further engineering of their surfaces to prepare other hybrid core-shell nanostructures.