Junpeng Wang

University of Jinan (Jinan, China), Chi-nan-shih, Shandong Sheng, China

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Publications (23)87.2 Total impact

  • Ruixia Shi · Ping Yang · Xueling Song · Junpeng Wang · Quande Che · Aiyu Zhang
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    ABSTRACT: ZnO flowers consisting of single crystal nanosheets with exposed {1-100} facets were fabricated from trisodium citrate via hydrothermal at 180 °C. The single crystal nanosheet has the thickness of about 70 nm and a well-crystalline structure with dominant surfaces as {1-100} planes. The site-specific nucleation-growth process contributes to the formation of hierarchical flower-like ZnO structures. The ZnO flowers exhibited white emission. The visible emission gradually decreased with time and the UV emission suggests that the recombined rate of photogenerated electrons and holes of samples varied with the synthesis parameters. The ZnO flowers displayed an enhanced photocatalytic performance compared with ZnO microspheres. The maximized exposure of the reactive {1-100} facets also favors the enhanced photocatalytic performance. Additionally, the special loose structural feature with an open microstructure has more important influences on the photocatalytic activity than specific surface area.
    No preview · Article · Jan 2016 · Applied Surface Science
  • Junpeng Wang · Ping Yang · Zeyan Wang · Baibiao Huang · Ying Dai
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    ABSTRACT: (GaN)1-x(ZnO)x solid solution with hexagonal plate-like morphology was synthesized by the nitridation of Zn/Ga/CO3 layer double hydroxides (LDHs) precursors, which were obtained by a co-precipitation method. Structure and composition evolution that depends on temperature during the nitridation between 500 and 900 °C were studied to reveal the transformation procedure from LDHs to (GaN)1-x(ZnO)x solid solution. The LDHs transformed to wurtzite structure (GaN)1-x(ZnO)x solid solution after a short time nitridation and maintained the hexagonal morphology until the temperature raised to 900 °C. EDX analysis revealed that the Ga/N ratio is more close to 1 when the temperature increased, and the Zn/Ga ratio decreased due to the volatilization of zinc. The diffuse reflection spectra for the samples obtained at different nitridation temperatures indicated that the light absorption properties of samples were closely related to the Ga/N and Ga/Zn ratios.
    No preview · Article · Dec 2015 · Journal of Alloys and Compounds
  • Qian Ma · Hanxiao Yue · Yuanna Zhu · Junpeng Wang · Quande Che · Ruixia Shi · Ping Yang
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    ABSTRACT: A series of red to near-infrared (NIR) emitting quantum dots (QDs) with spherical morphologies and tunable photoluminescence (PL) properties have been synthesized by a facile organic route using octadecene (ODE) as solvent and oleic acid (OA) as single capping agent. CdSe cores with the average size of 4.5 nm display the typical optical behaviors with the PL emission peak around 610 nm. The coating CdZnS shells are introduced on the surface of CdSe cores for improving the photostability and PL efficiency of the initial QDs. As the thickness of CdZnS shells increasing, the gradual red-shift of emission wavelength varying from 617 to 634 nm of the resulting QDs can be observed, along with the remarkable increase of PL quantum yield (QY). The composition-dependent CdTe x Se1-x (CdTeSe) cores with the emission in NIR region are easily carried out by adjusting the molar ratio of Se/Te. The abnormal variation of optical bowling effect is mainly ascribed to the composition effect of alloyed QDs. Compared with CdTe0.1Se0.9/CdZnS core/shell QDs, the introducing of CdZnS shells on CdTe0.05Se0.95 cores can exhibit better passivation effect on surface status, consequently leading to the red-shifted emission peaks in the range of 739–752 nm with the maximum PL QY reaching up to 45.09%. The unique PL properties of CdTeSe-based QDs in the red to NIR range make these core/shell QDs attractive for future biological sensing and labeling applications.
    No preview · Article · Sep 2015 · Journal of Nanoscience and Nanotechnology
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    ABSTRACT: One-dimensional ZnO nanostructures with various morphologies including nanotubes, nanobelts, solid fibers, nanochains, and porous nanotubes were created through adjusting the parameters in single-spinneret electrospinning and calcination processes. The evolution of morphology depended strongly on the viscosity of precursor solutions and calcination process. Namely, the nanotube was fabricated via a two-step calcination process while the nanochain and solid fiber were created using a one-step calcination process. The nanotubes consisted of small ZnO nanoparticles. Furthermore, the nanobelt was fabricated when much more zinc precursor was added to increase the viscosity of the precursor solution. A possible mechanism based on Kirkendall effect and the decomposition of polyvinyl pyrrolidone was proposed to explain the formation of ZnO nanotubes and other one-dimensional structures. The photocatalytic activity of these ZnO samples for the degradation of Rhodamine B under ultraviolet light was investigated, and nanobelts showed the best degradation efficiency. Besides, the deposition of Au nanoparticle on ZnO nanobelts can further enhance the photocatalytic performance due to the formation of ohmic contact.
    No preview · Article · Sep 2015
  • Junpeng Wang · Ping Yang · Baibiao Huang
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    ABSTRACT: Synthesis of Ti3+ self-doped TiO2 with high stability is very necessary to understand the role of Ti3+ defects in photocatalytic process. In this study, we report a simple strategy for preparing stable Ti3+ self-doped TiO2 nanowires with Ti2O3 as precursors. Raman and XPS spectrum confirmed the existence of Ti3+ and oxygen vacancies. Compared with the pure TiO2, the photocatalytic activity of the Ti3+ self-doped TiO2 enhanced under UV light irradiation, however, neither pure TiO2 nor the self-dope TiO2 samples exhibit photocatalytic activity while irradiated under visible light, though the self-doped TiO2 have an enhanced absorption in visible region. On the basis of the experimental results, the possible mechanism of Ti3+ in photocatalytic process is proposed. (C) 2015 Published by Elsevier B.V.
    No preview · Article · Aug 2015 · Applied Surface Science
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    ABSTRACT: One-dimensional (1D) titanium dioxide (TiO2) nanowires and nanobelts have been fabricated via a hydrothermal synthesis and subsequent calcination process in different atmospheres. Ti2O3 used as a raw material to directly provide Ti3+ in the resulting TiO2 nanomaterials. The Ti3+ concentration in TiO2 could be adjusted by annealing TiO2 precursors in different atmospheres. The photocatalysis activity of samples calcinated in air or nitrogen with different Ti3+ concentrations was investigated. By means of analyzing photocatalytic degradation curves, 1D TiO2 nanowires calcinated in nitrogen revealed enhanced photocatalysis activity compared with that one calcinated in air while the TiO2 nanobelts exhibited an opposite result. The enhanced photocatalytic activity is ascribed to the enhanced light absorption from the narrowing band gap. The proper concentrations of Ti3+ and oxygen vacancies result in the efficient separation of photo-generated charge carriers in these nanomaterials
    No preview · Article · Jul 2015 · RSC Advances
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    Changchao Jia · Ping Yang · Hsueh-Shih Chen · Junpeng Wang
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    ABSTRACT: Monodispersed mesoporous anatase titania (TiO2) hollow microspheres with controllable morphology and size are prepared via thioglycolic acid (TGA) chemically induced self-assembly for the first time. The formation process of TiO2 hollow spheres consists of three steps: hydrolysis of titanium butoxide (TBT) forming Ti-oxo clusters followed by connecting with TGA via hydrogen bonding, assembly of the Ti-oxo clusters to solid spheres, and transformation of the TiO2 solid spheres into hollow spheres through the synergistic effect of thermodynamics (Ostwald ripening process) and kinetics (gas release) factors. TGA molecules firstly supply an acidic condition slowing down the hydrolysis rate of TBT, then control the formation of solid spheres, and finally create hollow structures. The prepared TiO2 hollow sphere with mesoporous structure has a large specific surface area (292.20 m2/g). Photocatalytic degradation of methyl orange (MO) by the TiO2 hollow spheres after reflux treatment improves significantly, owing to removal of TGA molecules from the TiO2 hollow spheres. Moreover, photocatalytic water splitting of high crystalline TiO2 hollow spheres decorated with Pt nanoparticles exhibits an impressive performance of producing H2 (0.477 mmol/h).
    Preview · Article · Feb 2015 · CrystEngComm
  • Yunshi Liu · Junpeng Wang · Quande Che · Ping Yang · Yunlong Yue
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    ABSTRACT: Hydrophilic and hydrophobic quantum dots (QDs) including oleic acid (OA)-capped CdSe, thiodipropioyic acid (TDPA)-capped CdSe, and thioglycollic acid (TGA)-capped CdTe were incorporated into poly(vinyl pyrrolidone) (PVP) fibers via an electrospinning method using a PVP ethanol solution with PVP weight ratio of 8% which was obtained by optimizing preparation conditions. The amounts of the QDs were adjusted to investigate the effect of QD surface state on the morphologies of fibers. The QDs retained their photoluminescence (PL) peak wavelengths in PVP solutions and fibers. The PVP fiber with aqueous CdTe QDs was fabricated by dispersing QDs in water while the hydrophobic ones were firstly dispersed in hexane. With increasing the amount of CdSe QDs, the PL intensity of the fibers was gradually enhanced. In addition, CdSe nanorods were characterized by evident unevenness and local enrichment in the fibers because of rod morphology and properties of TDPA ligand. The fiber surface was rather smooth and it almost had no wrinkles.
    No preview · Article · Feb 2015 · Nanoscience and Nanotechnology Letters
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    ABSTRACT: The polyvinylpyrrolidone (PVP) hybrid luminescent micro-/nanofibers doped with the novel hybrid SiO2-coated CdTe nanocrystals (HS-CdTe NCs) have been fabricated for the first time via the electrospinning technique. The morphologies and photoluminescence (PL) emissions of HS-CdTe/PVP micro-/nanofibers prepared by doping the HS-CdTe NCs with the different PL peak wavelength (571, 616, and 643 nm) in PVP fibers were investigated by optical and PL microscope. The results revealed that all the HS-CdTe/PVP hybrid fibers showed an ultralong length for several hundreds of micrometers and a relatively uniform diameter of 1000 similar to 1200 nm. The hybrid fibers displayed a wavelength-tunable PL emission, determining by the PL of doped HS-CdTe NCs. Moreover, similar to the original PL properties of HS-CdTe NCs before the electrospinning, the HS-CdTe/PVP fibers also showed a series of superior PL properties, such as narrow and symmetry PL spectrum, high, and uniform brightness. For comparison purpose, we also prepared three CdTe/PVP hybrid fibers by doping the 553 nm, 600 nm, and 633 nm PL-emitting CdTe NCs respectively in PVP electrospinning fibers. The characterization results showed that, the obtained three CdTe/PVP hybrid fibers had a basically satisfactory micro-/nanofiber morphology with a long length and relatively uniform diameter, but all the fibers exhibited very weak PL emissions. The enormous contrast in PL properties between HS-CdTe/PVP and CdTe/PVP fibers should mainly be ascribed to the different connection modes of ligands with the NCs and the passivation effect of inert hybrid silica shell on HS-CdTe. It is hopeful that the high luminescent HS-CdTe/PVP micro-/nanofibers with the tunable PL peak wavelength would be a good candidate in the optical sensor, light-emitting devices (LEDs), nanometerscale waveguides, and the other related photonic materials.
    No preview · Article · Jan 2015 · Materials Chemistry and Physics
  • Ruixia Shi · Ping Yang · Qian Ma · Junpeng Wang · Quande Che
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    ABSTRACT: The monoclinic CuO nanosheet arrays, disk-like and sheaf-like CuO have been synthesized on Cu substrate by a facile solution route in absence of surfactant at room temperature (20 °C). The thickness of sheets and morphology of CuO can be tuned by the concentration and kind of alkali. A plausible growth mechanism was proposed to account for the formation of the nanosheet arrays. Due to the different rate of nucleation and crystal growth the morphology of CuO changed with the concentration of OH– when the same alkali metal hydroxide was used during reaction. The ionic radius of alkali metal hydroxide utilized to generate [Cu(OH)4]2– ions significantly influenced the morphology of CuO. The different cation radius has different charge density, which causes the different formation rate of the copper oxide precipitates.
    No preview · Article · Oct 2014 · Nanoscience and Nanotechnology Letters
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    Xiaobin Dong · Ping Yang · Junpeng Wang · Baibiao Huang
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    ABSTRACT: ZnO rhombic sheets consisting of small particles with a size range of 150–250 nm have been prepared successfully using zinc glycerolate as a template through calcining at 600 °C. The crystallinity of the small particle plays an important role toward highly efficient photocatalysis. The sheet consisting of regular ZnO particles with fewer surface defects revealed enhanced photocatalysis compared with that constructed from small ZnO nanoparticles. Monodisperse Ag2O nanoparticles were deposited on the rhombic sheet. Highly efficient photocatalysis was observed after Ag2O nanoparticle decoration under ultraviolet and visible-light irradiation for degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results of photocatalysis investigations demonstrated that the ZnO rhombic sheets with Ag2O/ZnO molar ratio of 1:6 had great activity for decomposing MO and 2,4-DCP. Ag2O/ZnO rhombic sheets are favorable for the separation of the photocatalyst, which is important for applications.
    Full-text · Article · Sep 2014 · ChemPlusChem
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    ABSTRACT: A Ti3+:TiO2/TiF3 hybrid was synthesized via a one-step facile solvothermal method. Due to the presence of TiF3, TiO2 contained a high concentration of Ti3+ species and Ti3+ was stabilized. The Ti3+:TiO2/TiF3 hybrid exhibited excellent visible-light photocatalytic reactivity. The electron structure of TiF3 was studied, and a photocatalytic mechanism was also proposed.
    No preview · Article · Aug 2014 · CrystEngComm
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    ABSTRACT: To investigate the shell deposited kinetics, CdSe quantum dots (QDs) and nanorods (NRs) with a maximum length of 17 nm were fabricated via organic synthesis routes. CdSe with a hexagonal crystal structure (wurtzite) favors epitaxial growth on the {002} surfaces when well-controlled conditions were used. The morphologies and sizes of CdSe samples depended strongly on chemicals and temperature. In the case of 320 °C, CdSe NRs with adjusted length of 7–17 nm were obtained from trioctylphosphine oxide (TOPO) and tetradecylphosphonic acid (TDPA). In contrast, short CdSe NRs (less than 10 nm) were created from octadecylphosphonic acid (ODPA) and trioctylamine (TOA). Spherical CdSe QDs were further fabricated using stearic acid (SA) and TOPO at 300 °C. CdSe cores were coated with Cd0.5Zn0.5S and CdTe shells. Anisotropic growth occurred during shell deposition because CdS shells grown preferentially on the {001} facet of the CdSe core. In the case of CdSe core prepared from TOPO and TDPA, CdSe/Cd0.5Zn0.5S core/shell samples prepared from long CdSe NRs (more than 10 nm) revealed a peanut morphology while the core/shell samples created from short ones (less than 10 nm) exhibited a spherical morphology. All of the CdSe/Cd0.5Zn0.5S core/shell samples revealed a similar length to that of the CdSe cores. This phenomenon was also observed for the core/shell samples fabricated using CdSe NRs prepared by ODPA and TOA. This is ascribed to the well-developed crystal structure of CdSe NRs fabricated using an organic synthesis at high temperature. In contrast, this anisotropic growth did not occur when spherical CdSe QDs prepared from SA and TOPO and the shell (Cd0.5Zn0.5S) coating carried out using SA and TOA. To indicate the shell depositing process, CdSe NRs fabricated using TDPA and TOPO were coated with a CdTe shell. CdTe monomers were deposited on the middle and tip parts of the CdSe NRs to form a tetrapod-like morphology at 220 °C. This is ascribed to the large difference of structure of CdSe (hexagonal) and CdTe (zinc blende).
    No preview · Article · Aug 2014 · Journal of Nanoparticle Research
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    ABSTRACT: A sol-gel SiO2 film prepared from 3-aminopropyltrimethoxysilane (APS) has been developed as an excellent medium to encapsulate both hydrophobic and hydrophilic quantum dots (QDs). The film was fabricated by spin and dip coating on flat substrates as well as by a spraying approach on various substrates with a 3dimensional (3D) surface. Pre-heat-treatment of the substrate plays an important role for creating homogeneous films on a 3D surface. In the case of aqueous CdTe and ZnSe0.9Te0.1 QDs, APS did not decrease the photoluminescence (PL) efficiency of the QDs. For hydrophobic QDs, a phase transfer from oil to water phase was first performed through the ligand exchange process between APS and the capping agent. By mixing QDs with different emitting colors, silica gel with white-light emission was obtained. Based on hydrophobic and hydrophilic QDs, white-light-emitting diodes with adjustable chromaticity coordinates were fabricated using a UV-emitting InGaN chip as excitation source. Because of the facile preparation procedure, high stability, and high PL efficiency, the magic film shows great potential for use in white-lighting-emission applications.
    No preview · Article · May 2014 · RSC Advances
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    ABSTRACT: Stable Ti(3+) self-doped TiO(2) with tunable phase composition and highly efficient visible-light photoactivity (ca. 32.7 times stronger than an undoped sample for ˙OH formation) was synthesized via a facile metallic zinc-assisted method. The surface Ti(3+) species can be stabilized by Zn doping, and the photocatalytic selectivity can be regulated by the phase composition.
    Full-text · Article · Dec 2012 · Chemical Communications
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    ABSTRACT: Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO(2) as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation.
    Full-text · Article · Jul 2012 · ACS Applied Materials & Interfaces
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    ABSTRACT: A new class of AgCl microstructures, concave cubes, with preferential overgrowth along <110> and <111> directions, has been prepared in a monodisperse fashion by a wet chemical oxidization method. With high-index facets exposed, the concave cubic AgCl exhibits higher photocatalytic activity in O(2) evolution than cubic ones.
    Full-text · Article · Mar 2012 · Chemical Communications
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    ABSTRACT: We report a facile and simple way to synthesize graphene@TiO 2 nanocomposites with controlled crystal facets by a one-pot hydrothermal process. By controlling the concentrations of the starting materials and reaction times, graphene@TiO 2 nanocomposites with various exposed crystal facets can be obtained. The surface states and the growth process of graphene@TiO 2 nanocomposites have been studied. Owing to the exposed high-reactive crystal facets and high dispersities of TiO 2 nanocrystals on graphene surfaces, the as-prepared sample exhibited enhanced photocatalytic activities over graphene@P25 nanocomposites.
    Full-text · Article · Mar 2012 · CrystEngComm
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    ABSTRACT: A novel Ag/AgBr/BiOBr hybrid was prepared by a rational in situ ion exchange reaction between BiOBr hierarchical microspheres and AgNO(3) in ethylene glycol followed by light reduction, which displayed superior visible light driven photocatalytic activities in sterilization of pathogenic organism and degradation of organic dye compared to N-doped P25.
    Full-text · Article · Jul 2011 · Chemical Communications
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    ABSTRACT: (GaN)1−x(ZnO)x solid solutions are potential photocatalysts for water splitting and environmental decontamination under visible light. Solid solutions prepared by the traditional method are not effective because of their low Zn content (x < 0.5). Here, we show that Zn-rich solid solutions (0.5 < x < 0.8) are readily prepared by the nitridation of layered double hydroxides (LDHs) containing Zn2+ and Ga3+ ions, and that the Zn content is easily adjusted by changing the Zn/Ga ratio of the LDH precursors. The band gap of (GaN)1−x(ZnO)x decreases gradually from 2.60 eV at x = 0.46 to 2.37 eV at x = 0.81. The Zn-rich solid solutions absorb strongly above 500 nm, and these solutions loaded with 1 wt% Pt are found to be efficient for photoreducing Cr6+ ions under visible light.
    No preview · Article · Mar 2011 · Journal of Materials Chemistry