Graphene oxide–cellulose acetate (GO–CA) nanocomposite membranes have been successfully prepared via phase inversion method. The GO sheets were firstly well dispersed in formamide, and then the solution was mixed with acetone containing CA so as to confirm the GO sheets well dispersed in the final GO–CA nanocomposite membranes. All the GO–CA nanocomposite membranes are composed of dense skin layer and sponge-like sublayer. With the increase in GO contents (from 0 to 0.01 wt%), the skin layer gradually became thinner and the pore size in the sublayer increased; meanwhile, the contact angle of GO–CA membranes decreased from 70.59° to 53.42° due to better hydrophilicity. All the membranes, except for the nanocomposite membrane containing 0.01 wt% GO, have featured pores at about 0.9 nm. The permeation rate of the membrane containing 0.005 wt% GO was 2.3 times higher than that of the CA membrane (0 wt% GO) with a little decrease (~15%) in salt retention. Compared with CA membrane, the enhanced performance of GO–CA membranes may be attributed to their enhanced structure and hydrophilicity.

Monophasic Ce3+ and Pr3+ co-doped yttrium aluminum garnet (YAG:Ce3+,Pr3+) nanoparticles with good dispersity and uniform grain sizes in the range of 50–80 nm were prepared by a two-step route, which consisted of a modified co-precipitation preparation of mixed metal hydroxide hydrate intermediates at low temperature of about 40 °C and a subsequent calcination conversion of the synthesized intermediates to crystalline nanoparticle products at about 1000 °C. The influences of both the lanthanide ion (Ce3+ and Pr3+) doping concentration and different doping (Ce3+/Pr3+) ratio on the photoluminescence intensity were systematically investigated. The synthesized (Ce0.6Pr0.4)0.04Y2.96Al5O12 nanoparticles were near spherical nanoclusters with good dispersity and uniform sizes in the range of 50–80 nm for about 85% of the particles. The strongest photoluminescence intensity was observed for the (Ce0.6Pr0.4)0.04Y2.96Al5O12 nanoparticle products.(a) SEM image of (Ce0.6Pr0.4)0.04Y2.96Al5O12 nanoparticles, (b) PL emission intensity of (CexPr1-x)yY0.04Al5O12 with different Ce/Pr ratioDownload high-res image (136KB)Download full-size image

Anisotropic-shaped CuCr2Se4 nanocrystals have been synthesized by thermal decomposition and reaction of novel mixed metal–oleate complexes with selenium in a high-boiling point organic solvent, trioctylamine (TOA). The synthesized CuCr2Se4 nanocrystals exhibit close to triangular and hexagonal morphology, with an average size of 20 nm. X-ray diffraction patterns and XPS spectral analysis confirm the formation of the pure spinel phase without any impurities. A possible reaction mechanism is suggested and formation pathways for the triangular and hexagonal shaped CuCr2Se4 nanocrystals are proposed. Magnetic studies indicate that the anisotropic-shaped CuCr2Se4 nanocrystals are superparamagnetic near room temperature but exhibit ferromagnetic behavior at lower temperatures, with magnetization values of 31 and 43 emu g−1 at 300 and 5 K, respectively.

In this work, hierarchical lead sulfide (PbS) nano-architectures were obtained via a simple one-pot hydrothermal method using a single-source precursor of Pb(II)–thiourea complex, without involving any insulating organic surfactants. Structurally, the eight-armed hierarchical PbS nanostructures were controlled to exhibit one-fold, two-fold, or three-fold hierarchy of anisotropic growth along 〈111〉 directions, under different reaction conditions. The product morphology and structural evolution in the hydrothermal process exhibit four stages: Stage 1, the nucleation of PbS nanoparticles from the complex precursor; Stage 2, the formation of cubic PbS growth bases; Stage 3, the formation of PbS nano-architectures from consumption of the previously formed PbS growth bases; and Stage 4, the deconstruction of the hierarchical PbS nanoarchitectures. Nanostructures with high energy crystal faces are attractive for designing high efficiency solar cell devices. Within the PbS octa-armed dendrites, all sub-units grow along the 〈111〉 directions with {100} facets exposed. The photoexcited electrons can be driven in the {100} facets with mixed Pb/S atoms through σ bonding consisting of the overlapping s(Pb 6s)–p(S 3p) orbitals, which significantly shortens the carrier transfer distance and reduces the carrier recombination. Drop-cast thin films prepared with octa-armed PbS dendrites, showing desired [100] structural orientation, exhibit greatly enhanced photocurrent compared to that of spray-printed thin films without any structural orientation. It is expected that these findings will be useful in understanding the formation and application of PbS and other fcc nanocrystals with different morphologies.

Magnetic spinel CdCr2S4 nanocrystals have been synthesized using a high-temperature solvothermal method. The synthesis process involves the reaction of excess 1-dodecanethiol (1-DDT) with CdCl2 and CrCl3·6H2O in 1-octadecene (ODE) solution carried out in a sealed titanium alloy autoclave. Nearly monodisperse spherical CdCr2S4 nanocrystals with an average size of 8.0 ± 1.5 nm are obtained. X-ray diffraction patterns confirm formation of the pure spinel phase without any impurities. Magnetic measurements indicate a Curie temperature (Tc) of ∼76 K for the synthesized CdCr2S4 nanocrystals, which are ferromagnetic at lower temperatures with a saturation magnetization value of 19 emu g−1 at 5 K. The magnetic entropy change ΔSm, evaluated from isothermal magnetic measurements, exhibits a maximum around 82 K, with a value of −ΔSm = 0.86 J kg−1 K−1 at Hmax = 5 T. ΔSm spans a broad temperature range, with a full width at half maximum of ∼88 K in the magnetic field range of 0–5 T, which is attractive for magnetic refrigeration applications in the liquid nitrogen temperature range.

•Sandwich-structured Si nanoparticles-Graphene nanocomposites were fabricated.•The method combines magnesiothermic reduction, freeze-drying, and thermal reduction.•The nanocomposite shows a 746 mAh g−1 reversible capacity after 160 cycles.•The nanocomposite’s specific capacity is superior to that of graphite and pure Si.•This novel method provides a low-cost alternative to prepare Si-based anodes.A novel method was developed to synthesize ordered sandwich-structured magnesiothermo-reduced Si nanoparticles (MR-Si NPs)-thermally reduced graphene oxide (TRGO) nanocomposites that combines magnesiothermic reduction, freeze-drying, and thermal reduction. The MR-Si NPs were dispersed into ordered graphene oxide (GO) layers with the aid of sonication. This MR-Si@TRGO composite structure was retained by freeze-drying and followed by thermal reduction. The key features of the nanocomposites, including nanoparticle crystal phase, size, and dispersity on the TRGO matrix, could be controlled by tuning reaction conditions such as reduction temperature and duration. The influence of the weight ratio of active materials: conductive agent: binder, the types of binder, and the content of electrolytes on the electrochemical performance as an anode in lithium-ion batteries was systematically investigated. The electrode fabricated using the MR-Si@TRGO nanocomposites under optimized conditions (80:10:10 for the weight ratio of MR-Si@TRGO: acetylene black: CMC; the electrolyte containing 5 v% vinylene carbonate) exhibited a reversible capacity of 746 mAh g−1 after 160 cycles at 1000 mA g−1, which is substantially higher than 701 mAh g−1 after 120 cycles for the MR-Si@TRGO in the absence of vinylene carbonate, 330 mAh g−1 for commercial graphite reported, and 10 mAh g−1 for pure MR-Si NPs tested at 200 mA g−1 with a weight ratio of 50:30:20 optimized for active materials: acetylene black: PVDF.

Monophasic Ce3+-doped yttrium aluminum garnet (Ce:YAG) nanoparticles with high crystallinity and tunable grain size ranging from ∼19–30 nm were prepared by a modified co-precipitation process with a follow-up calcination treatment. For the synthesis, aluminum, yttrium, and cerium nitrates were used as starting materials, ammonium sulfate as dispersant, and a combination of ammonium bicarbonate and ammonia as precipitating agent. Influence of precipitation temperature, the pH value of precipitant solutions, aging period, calcination conditions, and Ce-doping level were investigated for controlling the purity, particle size, and photoluminescence performance of the Ce:YAG nanoparticles. High-purity YAG nanoparticles were prepared at pH=10.50–11.00 and calcination temperatures of 850–1100 °C with a calcination time of 3 h. With increasing Ce3+ concentration, the peak in the emission spectra of the obtained nanopowders shifted from 529 nm for the 0.67 wt.%-Ce:YAG to 544 nm for the 3.4 wt.%-Ce:YAG, while the strongest photoluminescence intensity was observed for the 1.3 wt.%-Ce:YAG nanoparticles.XRD patterns of 0.67% (1), 1.3% (2), 2.0% (3), 2.7% (4), and 3.4% (5) Ce-doped YAG products synthesized by calcination at 1000 °C for 3 h (The inset shows magnified (420) peak positions, clearly indicating the successive shifting to low angles with increasing Ce-doping concentration) and Emission spectra of the YAG with different Ce3+ doping concentrations of 0.67% (1), 1.3% (2), 2.0% (3), 2.7% (4), and 3.4% (5) (All spectra were recorded at room temperature)

We describe a novel strategy for fabrication of a unique minky-dot-fabric-shaped composite of well-organized porous TiO2 microspheres and reduced-graphene-oxide (rGO) sheets used as an anode material in lithium-ion batteries. In this composite, the porous TiO2 microspheres act as hosts for fast and efficient lithium storage while the rGO sheets serve as highly conductive substrates. Such unique structural features assure a large contact area between the electrolyte and the electrode, favorable for the diffusion of electrons and Li+ ions. Moreover, they can accommodate volume changes of the electroactive TiO2 materials readily so as to improve the overall electrical conductivity between the electrodes during electrochemical processes. In electrochemical tests, the TiO2–rGO composites used as anodes in lithium-ion batteries exhibited superior performance with a reversible capacity of 100 mA h g−1 at 10 C for up to 100 cycles, as compared to 58 mA h g−1 at 10 C for up to 100 cycles from pure TiO2, suggesting great potential of this unique composite to function as high-rate lithium-ion battery materials.

We describe a novel strategy for fabrication of a unique minky-dot-fabric-shaped composite of well-organized porous TiO2 microspheres and reduced-graphene-oxide (rGO) sheets used as an anode material in lithium-ion batteries. In this composite, the porous TiO2 microspheres act as hosts for fast and efficient lithium storage while the rGO sheets serve as highly conductive substrates. Such unique structural features assure a large contact area between the electrolyte and the electrode, favorable for the diffusion of electrons and Li+ ions. Moreover, they can accommodate volume changes of the electroactive TiO2 materials readily so as to improve the overall electrical conductivity between the electrodes during electrochemical processes. In electrochemical tests, the TiO2–rGO composites used as anodes in lithium-ion batteries exhibited superior performance with a reversible capacity of 100 mA h g−1 at 10 C for up to 100 cycles, as compared to 58 mA h g−1 at 10 C for up to 100 cycles from pure TiO2, suggesting great potential of this unique composite to function as high-rate lithium-ion battery materials.

Magnetic spinel CdCr2S4 nanocrystals have been synthesized using a high-temperature solvothermal method. The synthesis process involves the reaction of excess 1-dodecanethiol (1-DDT) with CdCl2 and CrCl3·6H2O in 1-octadecene (ODE) solution carried out in a sealed titanium alloy autoclave. Nearly monodisperse spherical CdCr2S4 nanocrystals with an average size of 8.0 ± 1.5 nm are obtained. X-ray diffraction patterns confirm formation of the pure spinel phase without any impurities. Magnetic measurements indicate a Curie temperature (Tc) of ∼76 K for the synthesized CdCr2S4 nanocrystals, which are ferromagnetic at lower temperatures with a saturation magnetization value of 19 emu g−1 at 5 K. The magnetic entropy change ΔSm, evaluated from isothermal magnetic measurements, exhibits a maximum around 82 K, with a value of −ΔSm = 0.86 J kg−1 K−1 at Hmax = 5 T. ΔSm spans a broad temperature range, with a full width at half maximum of ∼88 K in the magnetic field range of 0–5 T, which is attractive for magnetic refrigeration applications in the liquid nitrogen temperature range.