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[en] Highlights: • Zn_0_._8_5Co_0_._0_5Mg_0_._1_0O films with different morphologies have been first prepared. • With increasing Na_3Cit, the films present morphology, orientation and bandgap changes. • Strong and wide visible emission centering at about 460 nm was found on PL spectra. • All samples show room temperature ferromagnetism. - Abstract: Zn_0_._8_5Co_0_._0_5Mg_0_._1_0O (ZCMO) films with different morphologies have been prepared by a low temperature hydrothermal method via changing sodium citrate (Na_3Cit) concentration in the source solutions, which have been investigated on their structural, optical and magnetic properties. With continuously increasing Na_3Cit concentration in the source solutions, these films derived from the solutions changed their morphologies from aligned nanorods to the rose flower-like crystals vertical to the substrate and preferential orientation from [0 0 0 1] to [101"¯0] direction which were characterized by scan electron microscope (SEM) and X-ray diffraction (XRD) respectively. It was also found that the bandgaps of the ZCMO films obtained from transmittance spectra enlarge with the increase of the Na_3Cit concentration in the source solutions. A strong and wide visible emission band centering at about 460 nm and the ferromagnetism were observed for all ZCMO films at room temperature, the intensities of which change with the variation of Na_3Cit concentration in the source solutions. The change of bandgaps and the origins of the visible emission and the ferromagnetism were also discussed
[en] High density arrays of Zn1-xCoxO (x = 0.05, 0.10, 0.15, denoted by ZnCoO) nanorods were vertically grown on glass coated ZnO films via hydrothermal reaction at 70 0. The structures and morphology of the arrays were studied by x-ray diffraction, photoluminescence (PL) spectroscopy and field emission scanning electron microscopy, which show that the nanorods of 150 nm diameter and 4.5 nm length grow along the [0 0 0 1] direction. X-ray photoemission spectroscopy demonstrated that Co was successfully doped into the nanorods. Ammonia concentration and ZnO buffer were found to play a very important role in the nucleation and growth of the ZnCoO nanorods. PL spectra were composed of broad ultraviolet (UV) emission and visible light. Using Gaussian simulation, the UV band was separated into two peaks, both of which were characteristic of redshift with the increase in Co concentration. The effect of the Co dopant on the broad ultraviolet emission peak and the formation mechanism of ZnCoO arrays were also discussed
[en] Highlights: • Visible-light-driven ZnO/ZnFe2O4/Ag spheres were successfully synthesized. • ZnO/ZnFe2O4/Ag spheres have unique mesoporous hollow structures. • ZnO/ZnFe2O4/Ag spheres exhibit excellent photodegradation of 2,4-dichlorophenol. • ZnO/ZnFe2O4/Ag spheres are reusable with the aid of a magnet. - Abstract: Silver-loaded ZnO/ZnFe2O4 (ZnO/ZnFe2O4/Ag) mesoporous hollow spheres were synthesized via a layer-by-layer technique followed chemical reduction method. The structures and morphologies of the as-prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N2 adsorption/desorption porosimetry. The photodegradation activities of ZnO/ZnFe2O4/Ag mesoporous hollow spheres toward 2,4-dichlorophenol were investigated under UV and visible light irradiation. The experimental results indicated that our mesoporous hollow spheres exhibited much higher photodegradation activities than P25 for the loading of silver particles, the bands matching and the unique structures. There exists an optimal loading dosage of silver particles. Too high or too low loading will reduce the photodegradation activities of ZnO/ZnFe2O4/Ag mesoporous hollow spheres. The possible mechanism behind was proposed. Noteworthily, the ZnO/ZnFe2O4/Ag mesoporous hollow spheres are reusable with the aid of a magnet, which is cost effective.
[en] Al-doped ZnO (AZO) and (Al, Na) co-doped ZnO (ANZO) thin films were prepared via sol-gel technique with an annealing process at temperatures between 450 and 550 deg. C for 60 min in air ambient, and their structural and optical properties have been investigated. The deposited films exhibited hexagonal zinc oxide structure except annealing at 450 deg. C. For the 500 deg. C-annealed samples, the surface morphology was analyzed via scanning electron microscopy, Photoluminescence (PL) of different Na content ANZO thin films showed that there were very obvious violet and blue emission bands between 400 and 500 nm, and intensity of which were enhanced with Na content increasing. Transparency of the films was improved along with increasing Na content. The result of UV indicated the absorb bands appeared obviously red shift with Na doping into ZnO, the optical gaps of all films far beyond 3.37 eV of pure ZnO, and gradually decreased with Na content increasing, this is very virtual for improving photoelectricity performance of transparent conduct oxide (TCO) film. The possible origins responsible for structure and optical properties also had been discussed.
[en] Searching alternatives to enhance the attainable conversion efficiency of organic photovoltaics is one of the most crucial issues toward renewable energy source. Here, the model ternary organic solar cells systems were designed to improve the performance of P3HT/PC61BM organic solar cells which promise a potential to large area and flexible fabrication, based on a group of cyclopent[hi]aceanthrylenes (CPAs) derivatives as the third cascade component in active layer of the device. In all of these solar cells, although all ternary structures containing a group of cyclopent[hi]aceanthrylene derivatives demonstrate the improvement of open-circuit voltage (VOC) compared to binary device of P3HT/PC61BM, the conversion efficiencies of these devices can not all be improved. This indicates the different influence on observable device metrics attributed by the different substituents around cyclopent[hi]aceanthrylene core. By extension, these results suggest that the ternary system used a simple one single active layer processing step can provide a potentially effective way to optimize the performance in BHJ solar cells.
[en] The surfactant-assisted hydrothermal route was used to prepare fractal dendrite cerium carbonate hydroxide (CeOHCO3) microstructures. After annealing at 600 deg. C for 4 h, the products were transformed to CeO2. The crystal structures of the two compounds were determined by X-ray diffraction (XRD). The morphologies and microstructures were characterized by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Room temperature photoluminescence (PL) showed that a strong ultraviolet emission at 336 nm was observed for CeOHCO3, and that centered at 415 nm for CeO2 microstructures. Both of these emission peaks are different from those reported for CeOHCO3 and CeO2 with other shapes. In addition, the possible growth mechanism of dendrite CeOHCO3 microstructures and the role of surfactant polyvinyl pyrrolidone (PVP) were also investigated in this paper.
[en] The configuration of electrode materials is of great significance to the performance of supercapacitors (SCs) because of its direct effects on specific surface area and electron transfer path. Given this, herein, a series of Co3O4 hierarchical configurations composed of porous acicular nanorods are designedly synthesized on Ni foam with in-site self-organization method depending on the addition of NH4F. In the absence of NH4F, Co3O4 nanorods self-assemble into porous urchin-like structure (PULS), while the introduction of NH4F can induce the vertical growth of Co3O4 acicular nanorods, forming porous acicular nanorod arrays (PANRAs). By simply tuning the concentration of NH4F, the Co3O4 PANRAs with different specific surface area can be obtained. As expected, Co3O4 PANRAs electrode for SCs (using 1 mmol of NH4F) exhibits high specific capacitance (1486 F g−1 at 1 A g−1) and excellent cycling stability (98.8% retention after 5000 continuous charge–discharge cycles), which are better than those of Co3O4 PULS electrode (658.2 F g−1 at 1 A g−1, 90.4%). Corresponding solid-state symmetric SC achieves a high energy density of 48.63 Wh kg−1 at power density of 600 W kg−1. Such superior performance is attributed to fast charge transfer kinetics, facile electron transport and ions diffusion rate resulting from porous array structure, indicating the importance of configuration design of electrode materials for high performance SCs. (paper)
[en] Highlights: • RGO/BaFe12O19/Fe3O4 nanocomposite are prepared via a two-step solvothermal method. • The maximum reflection loss can reach −46.04 dB, and the effective absorption bandwidth under −10 dB is 5.68 GHz. • Interfacial polarization as one of the mechanism for the enhanced absorption properties was detailedly analyzed. - Abstract: In this paper, we designed and prepared a composite of BaFe12O19 (BFO) flakes, two-dimensional graphene and Fe3O4 nanoparticles using a two-step solvothermal method. The combination of BFO flakes and two-dimensional graphene could effectively enhance the heterointerface and is believed to be favorable to enhance the interface polarization. The introduction of inverse spinel Fe3O4 as the third phase could increase the saturated magnetization. The phase structure, morphology, magnetic properties and electromagnetic wave absorption performance of the as-prepared samples were characterized. Due to the enhanced interfacial polarization between the BaFe12O19 flakes and graphene, the composite of RGO/BaFe12O19/Fe3O4 exhibits excellent microwave absorption properties. The maximum reflection loss can reach -46.04 dB at 15.6 GHz with a thickness of 1.8 mm, and the effective absorption bandwidth reaches 5.68 GHz (from 11.60 GHz to 17.28 GHz). It is believed that the RGO/BaFe12O19/Fe3O4 composites can find potential application in the field of microwave absorption due to their excellent absorption properties.
[en] Graphical abstract: Different loadings of SnO2 nanoparticles embedded in mesoporous silica (sample S1, S2 and S3) show higher response to H2 at lower operating temperature than pure SnO2 nanoparticles. - Highlights: • Two-solvent method is firstly used to synthesize SnO2 nanoparticles embedded in mesoporous silica (SBA-15). • The SnO2/SBA-15 nanocomposites show higher response to H2 at lower operating temperature than pure SnO2 nanoparticles. • The SnO2/SBA-15 nanocomposites have higher photodegradation ability toward methylene blue than pure SnO2 nanoparticles. - Abstract: Different loadings of SnO2 nanoparticles embedded in mesoporous silica (SBA-15) were prepared via a two-solvent method with the ordered hexagonal mesoporous structure of SBA-15 kept. X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy and N2 adsorption porosimetry were employed to characterize the nanocomposites. Compared with pure SnO2 nanoparticles, the SnO2/SBA-15 nanocomposites show higher response to H2 at lower operating temperature. The photocatalytic activity of as-prepared SnO2/SBA-15 for degradation of methylene blue was investigated under UV light irradiation and the results show that the SnO2/SBA-15 nanocomposites have higher photodegradation ability toward methylene blue than pure SnO2 nanoparticles
[en] The work reports the fabrication of Cu doped Zn–In–S (CZIS) alloy quantum dots (QDs) using dodecanethiol and oleic acid as stabilizing ligands. With the increase of doped Cu element, the photoluminescence (PL) peak is monotonically red shifted. After coating ZnS shell, the PL quantum yield of CZIS QDs can reach 78%. Using reverse micelle microemulsion method, CZIS/ZnS QDs@SiO2 multi-core nanospheres were synthesized to improve the colloidal stability and avoid the aggregation of QDs. The obtained multi-core nanospheres were dispersed in curing adhesive, and applied as a color conversion layer in down converted light-emitting diodes. After encapsulation in curing adhesive, the newly designed LEDs show artifically regulated color coordinates with varying the weight ratio of green QDs and red QDs, and the concentrations of these two types of QDs. Moreover, natural white and warm white LEDs with correlated color temperature of 5287, 6732, 2731, and 3309 K can be achieved, which indicates that CZIS/ZnS QDs@SiO2 nanostructures are promising color conversion layer material for solid-state lighting application. (paper)