Shape-selective formation of monodisperse copper nanospheres and nanocubes via disproportionation reaction route and their optical properties

Synthesis of stable and monodisperse Cu nanocrystals of controlled morphology has been a long-standing challenge. In this Article, we report a facile disproportionation reaction approach for the synthesis of such nanocrystals in organic solvents. Either spherical or cubic shapes can be produced, depending on conditions. The typical Cu nanospheres are single crystals with a size of 23.4 ± 1.5 nm, and can self-assemble into three-dimensional (3D) nanocrystal superlattices with a large scale. By manipulating the chemical additives, monodisperse Cu nanocubes with tailorable sizes have also been obtained. The probable formation mechanism of these Cu nanocrystals is discussed. The narrow size distribution results in strong surface plasmon resonance (SPR) peaks even though the resonance is located in the interband transition region. Double SPR peaks are observed in the extinction spectra for the Cu nanocubes with relative large sizes. Theoretical simulation of the extinction spectra indicates that the SPR band located at longer wavelengths is caused by assembly of Cu nanocubes into more complex structures. The synthesis procedure that we report here is expected to foster systematic investigations on the physical properties and self-assembly of Cu nanocrystals with shape and size singularity for their potential applications in photonic and nanoelectronic devices. © 2014 American Chemical Society

Synthesis of ZnO-ZnCo2O4 hybrid hollow microspheres with excellent lithium storage properties

通讯作者地址: Peng, DLZnO-ZnCo2O4 hybrid hollow microspheres are successfully produced via an annealing process of the pre-fabricated zinc-cobalt citrate hollow microspheres in air. ZnO and ZnCo2O4 have homogeneous distribution within the whole hollow microspheres. The gained hybrid hollow microspheres deliver outstanding lithium storage properties when utilized as the anode material in lithium ion batteries. A high reversible capacity of 1199 mA h g (1) can be retained after 200 cycles. The exceptional electrochemical properties of the hybrid hollow microspheres are ascribed to the synergetic effect between ZnO and ZnCo2O4 nanoparticles, the catalytic effect of Co nanocrystals, the favorable hollow structures together with the nanometer-sized building blocks of hybrid microspheres

Synthesis of ZnO-ZnCo2O4 hybrid hollow microspheres with excellent lithium storage properties

通讯作者地址: Peng, DLZnO-ZnCo2O4 hybrid hollow microspheres are successfully produced via an annealing process of the pre-fabricated zinc-cobalt citrate hollow microspheres in air. ZnO and ZnCo2O4 have homogeneous distribution within the whole hollow microspheres. The gained hybrid hollow microspheres deliver outstanding lithium storage properties when utilized as the anode material in lithium ion batteries. A high reversible capacity of 1199 mA h g (1) can be retained after 200 cycles. The exceptional electrochemical properties of the hybrid hollow microspheres are ascribed to the synergetic effect between ZnO and ZnCo2O4 nanoparticles, the catalytic effect of Co nanocrystals, the favorable hollow structures together with the nanometer-sized building blocks of hybrid microspheres

Disproportionation route to monodispersed copper nanoparticles for the catalytic synthesis of propargylamines

National Basic Research Program of China [2012CB933103]; National Outstanding Youth Science Foundation of China [50825101]; National Natural Science Foundation of China [51171157, 50971108]; Fundamental Research Funds for the Central Universities of China [201112G015]By taking advantage of the coordination between a monovalent Cu+ precursor and trioctylphosphine, monodisperse Cu nanoparticles were synthesized via a disproportionation reaction. A Cu@SiO2 nanocatalyst was formed by supporting Cu nanoparticles onto a silica aerogel, which showed a high surface area (779.53 m(2) g(-1)) and excellent catalytic activity for the synthesis of propargylamines

Shape-related optical and catalytic properties of wurtzite-type CoO nanoplates and nanorods

National Basic Research Program of China [2012CB933103]; National Outstanding Youth Science Foundation of China [50825101]; National Natural Science Foundation of China [51171157, 51171158]In this paper, we report the anisotropic optical and catalytic properties of wurtzite-type hexagonal CoO (h-CoO) nanocrystals, an unusual nanosized indirect semiconductor material. h-CoO nanoplates and nanorods with a divided morphology have been synthesized via facile solution methods. The employment of flash-heating and surfactant tri-n-octylphosphine favors the formation of plate-like morphology, whereas the utilization of cobalt stearate as a precursor is critical for the synthesis of nanorods. Structural analyses indicate that the basal plane of the nanoplates is (001) face and the growth direction of the nanorods is along the c axis. Moreover, the UV-vis absorption spectra, the corresponding energy gap and the catalytic properties are found to vary with the crystal shape and the dimensions of the as-prepared h-CoO nanocrystals. Furthermore, remarkable catalytic activities for H-2 generation from the hydrolysis of alkaline NaBH4 solutions have been observed for the as-prepared h-CoO nanocrystals. The calculated Arrhenius activation energies show a decreasing trend with increasing extension degree along the direction, which is in agreement with the variation of the charge-transfer energy gap. Finally the maximum hydrogen generation rate of the h-CoO nanoplates exceeds most of the reported values of transition metal or noble metal containing catalysts performing in the same reaction system, which makes them a low-cost alternative to commonly used noble metal catalysts in H-2 generation from the hydrolysis of borohydrides, and might find potential applications in the field of green energy

A facile approach to fabrication of well-dispersed NiO-ZnO composite hollow microspheres

A novel, facile and template-free approach was developed for the fabrication of amorphous zinc-nickel citrate hollow microspheres and crystalline well-dispersed NiO-ZnO composite hollow microspheres. In this approach, amorphous zinc-nickel citrate hollow microspheres were prepared through a simple chemical reaction and with room temperature ageing at nickel nitrate solution. The zinc-nickel citrate hollow microspheres have an average size of about 1.4 μm. The average thickness of the shell is about 300 nm. The content of Ni in the zinc-nickel citrate can be simply adjusted by changing the ageing time. The well-dispersed NiO-ZnO composite hollow microspheres can be prepared via the perfect morphology inheritance of the zinc-nickel citrate hollow microspheres, by calcination at 500 °C for 2 h. The optical absorption of the samples can extend into the visible region after the loading of NiO. The NiO-ZnO composite hollow microspheres with the high content of NiO exhibit the highest photocatalytic activity for the degradation of different organic dyes including Rhodamine-B, methylene blue and methyl orange under UV irradiation, which might be ascribed to their highest separation efficiency of photogenerated electron-hole pairs. In addition, these NiO-ZnO composite photocatalysts can be used repeatedly without a significant decrease of the photocatalytic activity under UV irradiation. ? 2013 The Royal Society of Chemistry

Engineering oxygen vacancies in hierarchically Li-rich layered oxide porous microspheres for high-rate lithium ion battery cathode

Abstract(#br)Lithium-rich layered oxides always suffer from low initial Coulombic efficiency, poor rate capability and rapid voltage fading. Herein, engineering oxygen vacancies in hierarchically Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 porous microspheres (L@S) is carried out to suppress the formation of irreversible Li 2 O during the initial discharge process and improve the Li + diffusion kinetics and structural stability of the cathode mateiral. As a result, the prepared L@S cathode delivers high initial Coulombic efficiency of 92.3% and large specific capacity of 292.6 mA h g −1 at 0.1 C. More importantly, a large reversible capacity of 222 mA h g −1 with a capacity retention of 95.7% can be obtained after 100 cycles at 10 C. Even cycled at ultrahigh rate of 20 C, the L@S cathode can..

Surface Ni-rich engineering towards highly stable Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode materials

Abstract(#br)Li-rich layered oxide cathode materials (LLOs) are regarded as promising next-generation cathode candidate in high-energy-density lithium ion batteries due to their high specific capacity over 250 mA h g −1 . However, LLOs always suffer from a series of severe issues, such as rapid voltage fading, fast capacity decay and bad cycling stability. In this work, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 -Li 1.2 Mn 0.44 Ni 0.32 Co 0.04 O 2 (LLO-111@111/811) hybrid layered-layered cathode is constructed via facilely increasing surface Ni content. Profiting from this special design, the prepared LLO-111@111/811 cathode exhibits a remarkable specific capacity of 249 mA h g −1 with a high capacity retention of 89.3% and a high discharge voltage of 3.57 V with a voltage retention of 83.0% after cycling 350 times at 0.5 C. As a result, the specific energy of LLO-111@111/811 cathode is 887 Wh Kg −1 at 0.5 C and it keeps as high as 658 Wh Kg −1 after 350 cycles. LLO-111@111/811 also exhibits an initial high capacity of 169 mA h g −1 at a high rate of 5 C and maintains a good capacity retention of 90.0% after 200 cycles. This strategy can successfully improve structural stability, suppress capacity decay and restrain voltage fading of LLOs, which is beneficial for their practical application

Aqueous Solution Preparation, Structure, and Magnetic Properties of Nano-Granular ZnxFe3−xO4 Ferrite Films

This paper reports a simple and novel process for preparing nano-granular ZnxFe3−xO4 ferrite films (0 ≤ x ≤ 0.99) on Ag-coated glass substrates in DMAB-Fe(NO3)3-Zn(NO3)2 solutions. The deposition process may be applied in preparing other cations-doped spinel ferrite films. The Zn content x in the ZnxFe3−xO4 films depends linearly on the Zn2+ ion concentration ranging from 0.0 to 1.0 mM in the aqueous solutions. With x increasing from 0 to 0.99, the lattice constant increases from 0.8399 to 0.8464 nm; and the microstructure of the films changes from the non-uniform nano-granules to the fine and uniform nano-granules of 50–60 nm in size. The saturation magnetization of the films first increases from 75 emu/g to the maximum 108 emu/g with x increasing from 0 to 0.33 and then decreases monotonously to 5 emu/g with x increasing from 0.33 to 0.99. Meanwhile, the coercive force decreases monotonously from 116 to 13 Oe