Yichun Liu

Government of the People's Republic of China, Peping, Beijing, China

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Publications (186)454.51 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We successfully synthesized mesoporous ZnxCd1-xS/reduced graphene oxide (ZxCSG) hybrid materials as photocatalysts using a facile one-pot hydrothermal reaction, in which graphene oxide (GO) was easily reduced (RGO), and simultaneously ZnxCd1-xS (ZxCS) nanoparticles (NPs) with a mesoporous structure were uniformly dispersed on the RGO sheets. By well tuning the band gap from 3.42 to 2.21 eV by changing the molar ratio of Zn/Cd (or Zn content), ZxCSG with an optimal zinc content has been found to have a significant absorption in the visible light (VL) region. In addition, under VL irradiation (λ > 420 nm), ZxCSG also showed zinc content-dependent photocatalytic efficiencies for the degradation of methylene blue (MB). Our findings are that, among ZxCSG, Z0.4CSG displayed not only a superior photodegradation efficiency of MB (98%), but also good removal efficiency of total organic carbon (TOC) (67%). Furthermore, Z0.4CSG had a high photocatalytic stability, and could be used repeatedly. The enhanced photocatalytic activity for Z0.4CSG could be attributed to a synergistic effect between mesoporous ZxCS NPs and RGO, including the optimal band gap and the moderate conduction band position for ZxCS (compared to CdS), efficient separation and transfer ability of photogenerated electron/hole pairs in the presence of RGO sheets, and relatively high surface area for both mesoporous ZxCS NPs and RGO.
    Dalton transactions (Cambridge, England : 2003). 07/2014;
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    ABSTRACT: In this paper, p-MoO3 nanostructures/n-TiO2 nanofiber heterojunctions (p-MoO3/n-TiO2-NF-HJs) were obtained by a two-step fabrication route. First, MoO2 nanostructures were hydrothermally grown on electrospun TiO2 nanofibers. Secondly, by thermal treatment of the obtained MoO2 nanostructures/TiO2 nanofibers, p-MoO3/n-TiO2-NF-HJs were obtained due to the phase transition of MoO2 to MoO3. With increasing the concentration of molybdenum precursor in hydrothermal process, the morphologies of MoO2 changed from nanoparticles to nanosheets, and then fully covered shells with increasing their loading on TiO2 nanofibers. After calcination, the obtained p-MoO3/n-TiO2-NF-HJs possessed similar morphology to that without thermal treatment. X-ray photoelectron spectra showed that both Ti 2p and OTi-O 1s peaks of p-MoO3/n-TiO2-NF-HJs shifted to higher binding energies than that of TiO2 nanofibers, suggesting electrons transfer from TiO2 to MoO3 in the formation of p-n nano-heterojunctions. The p-n nano-heterojunctions decreased photoluminescence intensity, suppressed photogenerated electrons and holes recombinations, and enhanced charge separation and photocatalytic efficiencies. The apparent first-order rate constant for the degradation of RB by p-MoO3/n-TiO2-NF-HJs with nanosheets surface morphology was two times that of TiO2 nanofibers. For the core/shell structure of p-MoO3/n-TiO2-NF-HJs, the internal electric field of p-n junction forced the photo-generated electrons transferring to TiO2 cores, then decreased the surface photocatalytic reactions and led to the lowest photocatalytic activity among the p-MoO3/n-TiO2-NF-HJs.
    ACS Applied Materials & Interfaces 05/2014; · 5.01 Impact Factor
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    ABSTRACT: TiO2/MgO/Au composite thin films with different MgO spacer layer thicknesses (0-41 nm) were fabricated on c-sapphire substrates by sputtering and pulsed laser deposition. Through optimizing the thickness of MgO spacer layer, which can effectively prevent nonradiative Förster resonant energy transfer and charge transfer between Au and TiO2, defect-related yellow-green light emission of TiO2 thin film was greatly enhanced - 12 times. The enhancement mechanism is attributed to the efficient increase of luminescence efficiency of deep levels in TiO2 induced by resonant coupling between localized surface plasmons in Au nanoparticles and electron-hole pairs in defect-related levels of TiO2.
    Journal of Nanoscience and Nanotechnology 05/2014; 14(5):3748-52. · 1.15 Impact Factor
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    ABSTRACT: In this work, we report a novel approach to fabricate hierarchical TiO2 microspheres (HTMS) assembled by ultrathin nanoribbons where an anatase/TiO2(B) heterojunction and high energy facet coexist. The as-adopted approach involves (1) nonaqueous solvothermal treatment of a mixture of tetrabutyl titanate and acetic acid and (2) topotactical transformation into HTMS via thermal annealing. By this approach, the TiO2(B) phase usually synthesized from an alkaline treatment route could be initially formed. Subsequently, phase transition from TiO2(B) to anatase TiO2 occurs upon thermal treatment. It is demonstrated that such phase transition is accompanied by crystallographic orientation along the c-axis of anatase and TiO2(B) crystals, resulting in not only a coherent interface between two phases but also oriented attachment of anatase mesocrystals along the [001] direction, and finally high-energy (001) facet exposure. Interestingly, this work provides an alternative fluorine-free route for the synthesis of TiO2 crystals with high-energy (001) facet exposure. The structural analysis reveals that lattice-match induced topotactic transformation from TiO2(B) to anatase is the sole reason for the (001) facet exposure of anatase TiO2. The photocatalytic test for acetaldehyde decomposition shows that HTMS with anatase/TiO2(B) heterojunction and high-energy (001) facet exhibits superior photocatalytic efficiency compared with the relevant commercial product P25, which can be ascribed to the synergistic effect of large surface area, anatase/TiO2(B) heterojunction as well as high-energy facet exposure.
    Nanoscale 04/2014; · 6.23 Impact Factor
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    ABSTRACT: Wide bandgap (3.37 eV) and high exciton-binding energy of ZnO (60 meV) make it a promising candidate for ultraviolet light-emitting diodes (LEDs) and low-threshold lasing diodes (LDs). However, the difficulty in producing stable and reproducible high-quality p-type ZnO has hindered the development of ZnO p–n homojunction LEDs. An alternative strategy for achieving ZnO electroluminescence is to fabricate heterojunction devices by employing other available p-type materials (such as p-GaN) or building new device structures. In this article, we will briefly review the recent progress in ZnO LEDs/LDs based on p–n heterostructures and metal–insulator-semiconductor heterostructures. Some methods to improve device efficiency are also introduced in detail, including the introduction of Ag localized surface plasmons and single-crystalline nanowires into ZnO LEDs/LDs.
    Chinese Science Bulletin 04/2014; 59(12). · 1.32 Impact Factor
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    ABSTRACT: A series of single-phased (Sr3-x,Ca1-y-z,Ba)(PO4)3Cl (SCBPO_Cl):xEu(2+), yTb(3+), zMn(2+) phosphors were synthesized by high-temperature solid-state reaction, and luminescent properties of these phosphors were investigated by means of photoluminescence and microcathode luminescence (μ-CL). Under UV excitation, white-light emission was obtained from triactivated SCBPO_Cl phosphors via combining three emission bands centered at 450, 543, and 570 nm contributed by Eu(2+), Tb(3+), and Mn(2+), respectively. White-light emission with the three emission bands is further demonstrated in the fluorescence microscope images, CL spectrum, and μ-CL mappings, which strongly confirm that the luminescence distribution of as-prepared SCBPO_Cl:xEu(2+), yTb(3+), zMn(2+) phosphors is very homogeneous. Both spectral overlapping and lifetime decay analyses suggest that dual energy transfers, that is, Eu(2+)→Tb(3+) and Eu(2+)→Mn(2+), play key roles in obtaining the white emission. The International Commission on Illumination value of white emission as well as luminescence quantum yield (51.2-81.4%) can be tuned by precisely controlling the content of Eu(2+), Tb(3+), and Mn(2+). These results suggest that this single-phased SCBPO_Cl:xEu(2+), yTb(3+), zMn(2+) phosphor may have a potential application as a near-UV convertible white-light emission phosphor for phosphor-converted white light-emitting diode.
    Inorganic Chemistry 03/2014; · 4.59 Impact Factor
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    ABSTRACT: We report a SnO2 nanobelt field effect transistor sensor, with the SnO2:Sb nanobelts serving as the source and drain electrodes. An anomalous feature of the device is that the threshold voltage shows the negative shift upon exposure to NO2. The comparative results from the other two types of devices, including SnO2 nanobelt with metal film electrodes and SnO2:Sb nanobelt with metal film electrodes, reveal that the interface between the SnO2:Sb nanobelt electrodes and the SnO2 nanobelt is responsible for the improved carrier injection efficiency and the negative shift in the threshold voltage. Such a response mechanism results in the detection limit for NO2 down to 10 ppb, with a sensitivity as high as 7.16 × 105 % at room temperature.
    01/2014; 104(7).
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    ABSTRACT: Phase selective synthesis is particularly valuable in revealing performance of photocatalyst existing as several polymorphic phases. In this work, we develop a general soft chemical route that used a TiO2 (B) nanosheet as a precursor to synthesize TiO2 nanostructures of desired phase. Benefiting from the structural similarity and ultrathin thickness feature, TiO2 (B) nanosheet precursor can readily transform to pure phase of anatase, rutile and brookite as well as mixed phase of brookite/anatase. A possible dissolution-recrystallization mechanism is proposed for the phase transition of TiO2 (B) nanosheets to other phases. Photocatalytic activity tests demonstrated that the brookite/anatase mixture had the highest activity in degrading acetaldehyde under UV light irradiation, due to the synergistic effect of high crystallinity, large surface area and mixed phase structure.
    01/2014;
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    ABSTRACT: TiO2 nanoporous films loaded with Ag nanoparticles exhibited distinctive photochromism and photoanisotropy under the visible linearly polarized irradiation. Based on such properties, a pure polarization holographic grating was recorded in the photochromic film using two orthogonal circularly polarized green beams (532 nm) and reconstructed with a red beam (632.8 nm). The diffraction efficiency of the holographic grating and the brightness of the reconstruction image were strongly dependent on the polarization state of the probe beam. The hologram can be erased simply by the irradiation of single green beam. This recording–erasing process can be repeated with little loss, which may be benefited from the reciprocating mobility of Ag+ ions, reversible deformation and re-growth of Ag nanoparticles under the alternate irradiation of linearly and circularly polarized light. The novel nanocomposite system with photoanisotropy makes a new range of applications in the field of high-density optical memory media.
    Optics Communications 01/2014; 318:1–6. · 1.44 Impact Factor
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    ABSTRACT: The construction of multiple heterojunctions holds promise for enhancing the performance of semiconducting photocatalysts. It can improve charge separation and extend light absorption range via component optimization. Herein, we report the structural design and optimization of a (WO3–Pt)/TiO2 multi-heterojunction photocatalyst based on WO3 nanorods and Pt and TiO2 nanoparticles. The multi-heterojunction-based photocatalyst displayed high activity for the degradation of Rhodamine B dye (RB), phenol, and gaseous acetaldehyde under visible light excitation. Moreover, its activity was higher than single-heterojunction-based photocatalysts, P25 and P25/Pt. The higher performance of the multi-heterojunction-based photocatalyst was attributed to the synergistic effect of efficient conduction band electrons transfer at the WO3/Pt interface and valence band holes transfer at the WO3/TiO2 interface. The photocatalytic performance of the multi-heterojunction-based photocatalyst was also dependent on the location of the loaded Pt nanoparticles. Pt surface loading on WO3, as opposed to loading on the TiO2 surface, was more beneficial in maximizing the photocatalytic activity.
    Chemical Engineering Journal. 01/2014; 237:29–37.
  • Electrochimica Acta. 01/2014; 130:290–295.
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    ABSTRACT: Bi2WO6–carbon nanofibers (Bi2WO6–CNFs) heteroarchitectures were fabricated by two steps consisting of the preparation of CNFs by electrospinning and growth of Bi2WO6 on the CNFs through ethylene glycol solvothermal processing. The results showed that the loading amounts of Bi2WO6 on the surface of CNFs could be controlled by adjusting the precursor concentration for the fabrication of Bi2WO6–CNFs heteroarchitectures during the solvothermal process. The photocatalytic tests revealed that the obtained Bi2WO6–CNFs heteroarchitectures showed higher photocatalytic property under visible light to degrade Rhodamine B than pure Bi2WO6 synthesized by solvothermal process in the absence of CNFs owing to improved separation efficiency of photogenerated electrons and holes. Moreover, the Bi2WO6–CNFs heteroarchitectures could be separated easily by sedimentation due to their one-dimensional nanostructural property. Meanwhile, the photocatalytic activity of Bi2WO6–CNFs heteroarchitectures was stable during the recycling due to the strong interactions between Bi2WO6 nanosheets and CNFs. Trapping experiment suggested that [TEX equation: {\text{O}}_{ 2}^{ \cdot - }] , instead of OH·, was the main active species during the photocatalytic process of the Bi2WO–CNFs heteroarchitectures.
    Journal of Sol-Gel Science and Technology 01/2014; 70(1). · 1.66 Impact Factor
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    ABSTRACT: A multiple drop-casting method of growing the ultralong dibenzo-tetrathiafulvalene (DB-TTF) micro/nanowire arrays has been developed which has the success ratio as high as 94%. This method enables the arrays with a length over a few hundreds of micrometers to locate between droplets with the definite orientation. The width of the micro/nanowires is controlled via tuning the concentration of DB-TTF solution in dichloromethane. The large-scale arrays can be grown onto Si, SiO2, glass, and the flexible polyethylene terephthalate (PET) substrates. These results show the promising potential of this facile solution-based process for the growth of the high-quality organic micro/nanowires, the fabrication of high-performance and flexible devices, and the fabrication of controlled assemblies of nanoscale circuits for fundamental studies and future applications.
    Nanoscale 12/2013; · 6.23 Impact Factor
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    ABSTRACT: In this work, a series of n-ZnO/p-GaN and n-MgZnO/p-GaN heterojunctions are designed and fabricated. The carrier transport and recombination mechanism is discussed based on electroluminescence (EL) and photoluminescence (PL) spectra, current–voltage (I–V) characteristics as well as energy band diagram. For ZnO device, the near-ultraviolet (UV) emission at ∼400 nm is attributed to the spatially-indirect, interfacial transition from ZnO conduction band minimum to GaN acceptor level. While for MgZnO diodes, their UV EL is independent on Mg composition, is thought to origin from the donor–acceptor pair (DAP) recombination in GaN layer. Our experiment results suggest that pure ZnO or MgZnO emission can hardly be achieved in n-(Mg)ZnO/p-GaN heterojunctions, rational device design towards (Mg)ZnO exciton emission is more important in the further work. EL spectra of different n-MgxZn1−xO/p-GaN diodes and the schematic carrier transport and recombination process.
    Physica Status Solidi (A) Applications and Materials 12/2013; 210(12). · 1.46 Impact Factor
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    ABSTRACT: One-dimensional BiOCl/PAN composite nanofibers which are composed of bismuth oxychloride (BiOCl) nanosheets on electrospun polyacrylonitrile (PAN) nanofibers were fabricated by combining electrospinning technique and solvothermal method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-vis diffuse reflectance, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy, thermal gravimetric and differential thermal analysis, were used to characterize the as-fabricated BiOCl/PAN composite nanofibers. The results revealed that BiOCl nanosheets were successfully immobilized on electrospun PAN nanofibers. The contents of the BiOCl nanosheets were controlled by adjusting the precursor concentrations for the fabrication of BiOCl/PAN composite nanofibers during the solvothermal synthesis processes. It was found that some interactions might exist between BiOCl and PAN molecules of BiOCl/PAN composite nanofibers. The obtained BiOCl/PAN composite nanofibers exhibited high photocatalytic activity for degradation of rhodamine B under ultraviolet light irradiation. The trapping experiments confirmed that the main active species for photocatalysis was hydroxyl radicals, which was produced by both the oxidative pathway and reductive pathway. Notably, the BiOCl/PAN composite nanofibers photocatalysts not only had good reusable property because of their one-dimensional structure and flexibility but also retained high photocatalytic stabilities after several cycles due to the interaction between BiOCl and PAN molecules.
    Applied Surface Science 11/2013; · 2.11 Impact Factor
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    ABSTRACT: A multiphase strategy is proposed and successfully applied to make the insulating green phosphor CaCeAl3O7:Tb(3+) conductive in the form of 12CaO·7Al2O3-CaCeAl3O7:Ce(3+),Tb(3+). The phosphor shows bright green-light emission with a short lifetime (2.51 ms) under low-voltage electron beam excitation (3 kV). The green photo- and cathodoluminescence from (5)D4-(7)FJ (J = 6, 5, 4, 3) transitions of Tb(3+) are significantly enhanced in comparison with pure C12A7:Tb(3+). It was confirmed that this enhancement is the consequence of the joint effects of energy transfer from Ce(3+) to Tb(3+) and broadening of the absorption spectrum of Ce(3+) due to the existence of multiple phases. In particular, under 800 V electron beam excitation, cathodoluminescence is improved by the modified electrical conductivity of the phosphor. When compared to the commercial Zn2SiO4:Mn(2+) with a long luminescence lifetime of 11.9 ms, this conductive green phosphor has greater advantage for fast displays.
    Dalton Transactions 09/2013; · 3.81 Impact Factor
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    ABSTRACT: Novel nanostructured Ag/TiO2 hybrid nanofibers (NFs) have been successfully prepared via a simple electrospinning process combined with silver mirror reaction. The Ag/TiO2 NFs demonstrated a unique morphology with evenly distributed Ag nanoparticles uniformly deposited onto the surface of each individual TiO2 NFs. The loading capacity and size of Ag NPs can be easily controlled by varying the silver mirror reaction time. Compared with pristine TiO2 NFs, such heterogeneous Ag/TiO2 nanocomposites exhibited preferable photocatalytic activity during photocatalytic degradation of rhodamine-B under the simulated sunlight irradiation and this enhanced photocatalytic performance was driven by combination and interaction between TiO2 and Ag NPs.
    Applied Surface Science 09/2013; · 2.11 Impact Factor
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    ABSTRACT: In2S3 nanosheets were assembled on electrospun TiO2 nanofibers template by a hydrothermal technique. For the obtained one-dimensional In2S3/TiO2 hierarchical heterostructures (1D In2S3/TiO2 H-HSs), the density and size of the secondary In2S3 nanosheets could be controlled by adjusting the reactant concentrations for the preparation of In2S3 in the hydrothermal process. The 1D In2S3/TiO2 H-HSs exhibited higher visible-light photocatalytic activity for the degradation of Methyl orange (MO) and the reduction of Cr(VI), as compared with the pure TiO2 nanofibers and pure In2S3 nanosheets. The enhanced visible light photocatalytic activity might be attributed to the extended absorption in the visible light region from the narrow band-gap In2S3, the effective photogenerated electron-hole separation by the photosynergistic effects of the In2S3/TiO2 H-HSs and quick electron-transfer in the 1D TiO2 nanofibers. Meanwhile, the 1D In2S3/TiO2 H-HSs could be recycled easily by sedimentation due to their nanofibrous nonwoven web structure. Moreover, the mechanisms of photodegradation of MO and photoreduction of Cr(VI) were proposed through systematical investigations. This work provided new insights into utilizing 1D In2S3/TiO2 H-HSs as high efficiency visible-light-driven photocatalysts for environmental remediation and energy conversion.
    Journal of hazardous materials 06/2013; 260C:892-900. · 4.14 Impact Factor
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    ABSTRACT: Two series of K1-xNaxSrPO4:0.005Eu2+ and K0.4Na0.6Sr0.995-yPO4:0.005Eu2+, yTb3+ phosphors are synthesized via high-temperature solid-state reaction. Their emission color can be tuned from deep blue to blue-green through modulating the crystal field strength and energy transfer. Partial substitution of K+ by Na+ results in contraction and distortion of unit cell of K1-xNaxSr0.995PO4:0.005Eu2+ host, tuning the emission from 426 to 498 nm. The red-shifted emission is attributed to an increased crystal field splitting for Eu2+ in a lowered symmetry crystal field. The tunable emission is further demonstrated in cathodoluminescence spectra, indicating that the luminescence distribution of K1-xNaxSr0.995PO4:0.005Eu2+ phosphor is very homogenous. On the other hand, utilizing the principle of energy transfer, the emission color can be further tuned by co-doping Tb3+. The chromaticity coordinates for the co-doped phosphor, K0.4Na0.6Sr0.995-yPO4:0.005Eu2+,yTb3+, can be adjusted from (0.202, 0.406) for y = 0 to (0.232, 0.420) for y = 0.09. Energy transfer processes from sensitizer Eu2+ to activator Tb3+ are studied and demonstrated as a resonance-type dipole-dipole interaction mechanism, and the critical distance of the energy transfer calculated to be 12.46 Å using concentration quenching method.
    J. Mater. Chem. C. 05/2013;
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    ABSTRACT: A three-dimensional (3D) free-standing network composed of cross-linked carbon@Au core-shell nanofibers was fabricated by combining the electrospinning technique and an in situ reduction approach. The results showed that a uniform Au layer of approximately 5 nm thickness was formed around the electrospun carbon nanofiber. What's more, it's interesting to note that the Au layer was composed of small Au nanoparticles. And, the as-prepared CNFs@Au network exhibited excellent catalytic activity for the reduction of 4-nitrophenol (4-NP) based on the electron-rich catalytic platform arising from the synergistic effect between carbon and Au. Notably, the free-standing 3D nanofibrous cross-linked network structure could improve the catalyst's performance in separation and reuse.
    Physical Chemistry Chemical Physics 05/2013; · 3.83 Impact Factor

Publication Stats

747 Citations
454.51 Total Impact Points

Institutions

  • 2014
    • Government of the People's Republic of China
      Peping, Beijing, China
  • 2000–2014
    • Northeast Normal University
      • • Center for Advanced Optoelectronic Functional Materials Research
      • • Department of Chemistry
      Hsin-ching, Jilin Sheng, China
  • 2012
    • Beihua University
      Yung-chi, Jilin Sheng, China
  • 2011
    • Changchun University of Technology
      Huinan, Jilin Sheng, China
  • 2002–2009
    • Changchun Institute of Optics, Fine Mechanics and Physics
      Hsin-ching, Jilin Sheng, China
  • 2007
    • Jilin University
      • College of Electronic Science and Engineering
      Jilin, Jilin Sheng, China
  • 2006
    • Fisk University
      • Department of Physics
      Nashville, TN, United States
  • 2005
    • Nanjing University
      • Department of Physics
      Nanjing, Jiangsu Sheng, China