Huan-Ping Zhou

Peking University, Peping, Beijing, China

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Publications (9)69.28 Total impact

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    Hao-Shuai Wu · Ling-Dong Sun · Huan-Ping Zhou · Chun-Huan Yan
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    ABSTRACT: This article reports a facile and controllable two-step method to construct TiO(2)-Pt@SiO(2) nanocomposites. TiO(2) nanoparticles (NPs), with small size and high surface energy, were synthesized by a solvothermal reaction process. The TiO(2)-Pt@SiO(2) nanocomposites were fabricated by a reverse micro-emulsion method. SiO(2) shell coated NPs were adopted for further photocatalytic reaction. Because of their small size and high surface energy, TiO(2)@SiO(2) and TiO(2)-Pt@SiO(2) nanocomposites show higher photocatalytic activity than commercial Degussa P25. Compared with TiO(2)@SiO(2), TiO(2)-Pt@SiO(2)nanocomposites have improved photocatalytic activity due to the Pt induced spatial separation of electrons and holes. The silica shells not only maintain the structure of the nanocomposites but also prevent their aggregation during the photocatalytic reactions, which is highly important for the good durability of the photocatalyst. This strategy is simple, albeit efficient, and can be extended to the synthesis of other composites of noble metals. It has opened a new window for the construction of hetero-nanocomposites with high activity and durability, which would serve as excellent models in catalytic systems of both theoretical and practical interest.
    Preview · Article · Apr 2012 · Nanoscale
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    ABSTRACT: Pt/CeO(2) hetero-nanocomposites were prepared from Pt/CeO(2)@SiO(2) obtained by a microemulsion-mediated method. Facilitated by the earlier calcination under the protection of a silica shell, the as-formed Pt/CeO(2) hetero-nanocomposites exhibit a good thermal stability, which can preserve their pristine properties after subsequent calcination at even 450 degrees C. The thermally stable Pt/CeO(2) hetero-nanocomposites possess the characteristics of small particle size, low aggregation, and maximized Pt/CeO(2) interfaces and thus exhibit high catalytic activity in CO oxidation.
    No preview · Article · Mar 2010 · Journal of the American Chemical Society
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    ABSTRACT: Inorganic-organic composite films for rewritable optical storage are fabricated base on the reversible luminescence modulation of ordered upconversion nanopatterns via a photochromic diarylethene. The near-IR excitation for reading the upconversion emission does not affect the recorded data bits. Moreover, the spatially well-defined 2D nanopatterns promise future applications in ultrahigh-density storage.
    No preview · Article · Feb 2010 · Advanced Materials
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    ABSTRACT: Colour modification of the upconversion emission has been successfully achieved in a novel upconversion photonic crystal.
    No preview · Article · Nov 2009 · Chemical Communications
  • Huan-Ping Zhou · Rui Si · Wei-Guo Song · Chun-Hua Yan
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    ABSTRACT: Uniform Ce1−xZrxO2 (x=0.2–0.8) nanocrystals with ultra-small size were synthesized through a thermolysis process, facilitated by the initial formation of precursor (hydrated (Ce,Zr)-hydroxides) at low temperature. TEM, XRD, EDAX, and Raman spectra were employed to study the formation of the solid solutions with various Ce/Zr ratios. Ultraviolet–visible (UV–vis) spectra showed that the ratios of Ce3+ to Ce4+ in both surface and bulk for the as-prepared Ce1−xZrxO2 nanocrystals increased with the zirconium content x. The well-distributed Zr and Ce in the hydrated (Ce,Zr)-hydroxides before their thermolysis became the crucial factor for the structural homogeneity of the products. In addition, this strategy was extended to the synthesis of Ce1−xGdxO1−x/2, Ce1−xSmxO1−x/2, and Ce1−xSnxO2 solid solutions. Catalytic measurements indicated that the ceria-based catalysts were active for CO oxidation at temperatures beyond 250 °C and the sequence of catalytic activity was Ce0.5Zr0.5O2>Ce0.8Zr0.2O2>Ce0.2Zr0.8O2>Ce0.5Sm0.5O1.75.AbstractUniform ultra-small nanostructured Ce1−xZrxO2, Ce1−xGdxO1−x/2, Ce1−xSmxO1−x/2, and Ce1−xSnxO2 solid solutions with homogeneous textures were synthesized through a thermolysis process, facilitated by the initial formation of precursors (hydrated (Ce,M)-hydroxides).
    No preview · Article · Sep 2009 · Journal of Solid State Chemistry
  • Huan-Ping Zhou · Chao Zhang · Chun-Hua Yan
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    ABSTRACT: The Langmuir-Blodgett (LB) technique provides a facile and robust method for the formation of large-area films of various nanoparticles (NPs), including 24.9 nm NaYF(4):Yb,Er nanospheres, 12.0 nm LiYF(4) nanopolyhedra, 14.1 x 1.8 nm triagonal-shaped LaF(3), 12.6 nm square CaF(2), 9.5 x 2.0 nm hexagonal EuF(3), and so forth. The assembly patterns of the deposited films were studied in accordance with the pi-A isotherms. Combined with the TEM observations, several representative stages of assembly process can be distinguished. The scrutiny of the self-assembly process by means of their pi-A isotherms elucidates that the concentration, size, and symmetry of nanoparticles play crucial roles in this process. The concept of "effective concentration", which is defined as the amount of nanoblocks in the "gas phase" rather than the actual number of nanoparticles at the air-water interface, was first proposed as a control parameter to elucidate the possible assembly kinetics. The similarly shaped 12.0 nm LiYF(4) and the 24.9 nm NaYF(4):Yb,Er were selected as the size-dependent examples. The smaller nanoparticles show a strong tendency of congregation to lower the surface energy. Three representative samples, namely, 24.9 nm NaYF(4):Yb,Er nanospheres (O(h)), 14.1 x 1.8 nm oblate triagonal LaF(3) nanosheets (D(3h)), and 41.3 nm x 24.6 nm NaYF(4) rods (D(6h)), were selected as the shape-dependent samples, which showed that the assembly patterns were contributed by the stability arising from the geometry of the nanoparticles, the tendency of aggregation of nanoparticles, and the probable rotation energy during the compression. More importantly, guided by the above assembly kinetics, for the 9.5 x 2.0 nm hexagonal EuF(3), we can effectively acquire the desirable assembly pattern.
    No preview · Article · Aug 2009 · Langmuir
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    ABSTRACT: Dimension-tunable ceria nanostructures including 0D uniform nanocrystals, 2D polycrystalline assembly, and 3D mesoporous framework were selectively synthesized from the same cerium precursor of Ce(OC8H17)4 with the designed solution methods. The thermolysis of Ce(OC8H17)4 in tri-n-octylphosphine oxide and dioctyl ether at 250 °C yielded uniform ceria nanopolyhedra and elongated nanocrystals (around 2.2 nm in size). Through the polyol alcoholysis in ethylene glycol at 195 °C, polycrystalline assembled nanostructures (PANs) composed of small ceria crystallites (around 3−4 nm) were achieved, showing adjustable cross-linkages in the 2D dendritic structure. The raise of Ce(OC8H17)4 concentration and reaction time would increase the cross-linkages of the PANs. By a conventional sol−gel route, mesoporous ceria gels in an ordered 2D hexagonal mesostructure were synthesized at 40 °C through controlling the hydrolysis rate, and the condensation and aggregation of the metal precursor, as well as the critical micelle concentration (cmc) of the block-copolymer surfactants as used (e.g., EO20-PO70-EO20, P123). Catalytic measurements indicated that three CeO2 catalysts prepared from the above different nanostructures were active for CO oxidation at temperatures beyond 250 °C and showed T50 (50% conversion of CO) at 310 °C for the PAN catalysts, 340 °C for the nanopolyhedra catalyst, and 390 °C for the mesoporous catalyst.
    No preview · Article · Nov 2008 · The Journal of Physical Chemistry C
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    ABSTRACT: Uniform CeO(2) nanoflowers were synthesized by rapid thermolysis of (NH(4))(2)Ce(NO(3))(6) in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO(2) nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10-40 nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO(2) nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO(3) (-)) via hydrolysis of (NH(4))(2)Ce(NO(3))(6) at temperatures in the range 140-220 degrees C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220 degrees C in a strong redox reaction. After calcination at 400 degrees C for 4 h the 33.8 nm CeO(2) nanoflowers have a specific surface area as large as 156 m(2) g(-1) with high porosity, and they are highly active for conversion of CO to CO(2) in the low temperature range of 200-400 degrees C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuO(x)) nanoflowers.
    No preview · Article · Apr 2008 · Chemistry
  • Rui Si · Ya-Wen Zhang · Huan-Ping Zhou · Ling-Dong Sun · Chun-Hua Yan
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    ABSTRACT: Single-crystalline and monodisperse cubic rare-earth (RE = La to Lu, Y) oxide nanocrystals (ultrathin nanoplates and nanodisks) have been synthesized via a nonhydrolytic approach in oleic acid (OA)/oleylamine (OM)/1-octadecene (ODE) using various rare-earth complexes, including acetylacetonate, benzoylacetonate, and acetate, as the precursors. The transformation from the complex precursors to RE2O3 was proposed to occur in two stages:  first, the formation of rare-earth oleates by ligand exchange in solution, and second, the subsequent decomposition of the oleates into RE2O3 catalyzed by the base of OM. The selective adsorption of coordinating OA ligands onto specific crystal planes of cubic RE2O3 nanocrystals made them adopt a plate shape with the confined growth of {100} facets and/or a disk shape with the confined growth of {111} facets. Along with delicately tuning the polarity of the dispersant, the RE2O3 nanocrystals could be aligned to form “side-to-side” or “face-to-face” self-assembly nanoarrays on carbon-coated copper grids. With the developed synthetic method, we also obtained high-quality luminescent Y2O3:Eu ultrathin nanodisks, which displayed strong surface-dependent, highly pure red emissions that were due to selective incorporation of Eu3+ ions in the surface of the nanodisks.
    No preview · Article · Dec 2006 · Chemistry of Materials