Crystal structure, electronic structure, and photoluminescence properties of La3BW(1-x)Mo(x)O9:Eu³âº red phosphor.

A series of La3BW(1-x)Mo(x)O9:Eu(3+) (x = 0-0.4) polycrystalline powders were prepared by using solid-state reactions. The phase structure, UV-vis absorption spectra, and photoluminescence properties were studied as a function of the Mo/W ratio. When Mo(6+) ions are incorporated into the lattice, the characteristic sharp lines in the excitation spectra of Eu(3+) monitored at 617 nm are prominently enhanced, which join the ligand-to-metal charge transfer (LMCT) band of La3BW(1-x)Mo(x)O9:Eu(3+) into a broad band ranging from 250 to 450 nm centered at 375 nm. The intensity of the broad excitation band reaches a maximum when the content of Mo(6+) ions increases to x = 0.3. On the other hand, the LMCT band around 306 nm decreases and shifts toward the longer wavelength. These features are advantageous to near-UV or blue light GaN-based LED applications. Orbital population analysis by density functional theory calculation (DFT) reveals that the near-UV excitation of La3BW(1-x)Mo(x)O9:Eu(3+) red phosphor is due to the electronic transition from the O 2p orbital to the W 5d and Mo 4d orbitals, respectively. With the introduction of Mo(6+) into the lattice, the band gap of La3BW(1-x)Mo(x)O9 becomes narrower than that of the pure phase La3BWO9.

Mesoporous bioactive glass as a drug delivery system: fabrication, bactericidal properties and biocompatibility.

Implant-associated infection remains a difficult medical problem in orthopaedic surgery. Here, we report on the fabrication of gentamicin-loaded mesoporous bioactive glass (Gent-MBG) for use as a controlled antibiotic delivery system to achieve the sustained release of antibiotics in the local sites of bone defects. The high surface area and mesoporous structure of MBG enable higher drug loading efficiency (79-83 %) than non-mesoporous biological glass (NBG) (18-19 %). Gent-MBG exhibits sustained drug release for more than 6 days, and this controlled release of gentamicin significantly inhibits bacterial adhesion and prevents biofilm formation by S. aureus (ATCC25923) and S. epidermidis (ATCC35984). Biocompatibility tests with human bone marrow stromal cells (hBMSCs) indicate that MBG has better biocompatibility than NBG. Therefore, Gent-MBG can be used as a controlled drug delivery system to prevent and/or treat orthopedic peri-implant infections.

Investigation of the toxic effect of a QDs heterojunction on the interactions between small molecules and plasma proteins by fluorescence and resonance light-scattering spectra.

The effect of a ZnO#ZnS QDs heterojunction (O#SQDs) on the binding affinities of flavonoid glycosides for bovine serum albumin (BSA) was investigated. The fluorescence intensities of BSA decreased remarkably with increasing concentration of O#SQDs. The magnitudes of the binding constants of flavonoid glycosides for BSA in the presence of O#SQDs were in the range of 10(5)-10(7) L mol(-1), and the number of binding sites per BSA (n) was determined as 1.24 ± 0.17. O#SQDs increased the affinities of flavonoid glycosides for BSA by about 2.96% to 114.68% depending on their structures. O#SQDs in blood will enhance the transportation of flavonoid glycosidegs in blood and improve their pharmacology effects. From this point, O#SQDs are a perfect candidate for flavonoid glycosides delivery applications.

Selective and controlled synthesis of multiform morphologies Y2O3:Eu3+ and luminescence properties.

Uniform Y2O3 nanorods, nanosheets, nanotubes and nanoshperes were controllably synthesized via an urea-based homogeneous precipitation and hydrothermal synthesis through choosing appropriate yttrium sources, the water/ethanol ratio of mixed solvents and precipitators. The nanopheres and nanotubes were obtained through homogeneous precipitation method using soluble yttrium nitrate as the yttrium source. The nanosheets and nanorods were obtained via a facile hydrothermal synthetic method using yttrium chloride and yttrium acetate as the yttrium source. During these experiments Urea and NaOH were used as precipitators and added in correct order. We also studied the spectroscopic properties of Y2O3:Eu3+ phosphor. The Eu3+ ion mainly shows its characteristic red (611 nm, 5D0 --> 7F2) emissions in all kinds of morphologies Y2O3:Eu3+ phosphor, but emission intensity are different. It can be explain from the viewpoint of their different absorption properties closely related to their micro-morphologies.

Effect of alkali-metal ions on the local structure and luminescence for double tungstate compounds AEu(WO4)2 (A = Li, Na, K).

The effect of alkali-metal ions on the local structure and luminescence properties for alkali-metal europium double tungstate compounds AEu(WO(4))(2) (A = Li, Na, K) has been investigated by a dual-space structural technique, atomic pair distribution function (PDF) analysis, and the Rietveld method of powder X-ray diffraction. The compounds AEu(WO(4))(2) (A = Li, Na) crystallize in the isostructure with the tetragonal space group I41/a (No. 88) and show the same luminescence properties in spite of the different doped alkali metals. However, KEu(WO(4))(2) crystallizes in monoclinic symmetry with the space group C2/c (No. 15). Compared with the two other counterparts, KEu(WO(4))(2) exhibits a more effective charge-transfer excitation, a larger Stokes shift, and a broader 612 nm emission band. This phenomenon is ascribed to the lower crystal symmetry in KEu(WO(4))(2), which influences bond distances and the coordination number of Eu(3+). Two complementary methods, the Rietveld method and PDF analysis, reveal that both LiEu(WO(4))(2) and NaEu(WO(4))(2) afford the same local surroundings of Eu(3+). The local structure determined by the Rietveld and PDF methods well account for the observed luminescent properties.

Correlations between shape and near infrared reflective properties of nano/micro-yttria.

Yttria nanorods, nanoflakes and microshperes have been prepared via solvothermal and homogeneous precipitation methods followed by further calcining treatment, without any catalysts, templates, or substrates, in which yttrium nitrate was used as the yttrium source, sodium hydroxide and urea as the precipitators. The results show that the reflectivity of nano-yttria has significant correlations with its nanostructures. In contrast, Y2O3 microshperes possess about 90% reflectivity in the NIR region, which can be applied in energy saving and military camouflage etc.

Morphologies and luminescence properties of SrZnO2 microstructure.

The SrZnO2 of beardlike and sheetlike nanobundles, rod and treelike nanostructures have been synthesized by a citrate-gel combusting synthesis approach. As-prepared SrZnO2 shows orthorhombic structure with Pnma space group and unit cell with the lattice parameters: a = 5.830 A, b = 3.340 A and c = 11.348 A. By increasing the sintering temperature, the beardlike nanobundle gradually dissolved to form microrods and treelike microstructure. Citrate acid exerts a major influence in directing the formation of these unique SrZnO2 microstructures. These materials were analyzed for their use to luminescence materials. The as-made samples exhibit an efficient absorption and excitation band in the UV spectral region (centered at 380 nm). In the same time, the samples of with different morphologies showed a broad yellow emission peak centered at approximately 545 nm which should been associated with the composition and morphologies of sample or from the oxygen vacancies of semiconductor SrZnO2. The material may be used as novel conversion phosphors or host material of phosphor for white-light LEDs.

Preparation and tunable luminescent characteristics of SiO2 coated ZnO:LiAc nanoparticles.

ZnO:LiAc nanopaticles were successfully synthesized though a colloidal-sol technique in nonaqueous solution under ultrasonic irradiation. The luminescent characteristics from blue to red can be tunable by varying [Li]/[Zn] ratios. The possible reason of tunable luminescent characteristics can be attributed to the increase of density of oxygen vacancies caused by Li+ adsorbed in the surface of magic-sized ZnO nanocrystals based on XRD, zeta potential and XPS results. What's more, it is found that SiO2 shell coated on ZnO:LiAc nanoparticles can improve the surface property of ZnO nanoparticles and enhance the PL emission intensity and optical stability. Due to its excellent luminescent characteristic and optical stability, as-prepared SiO2 coated ZnO:LiAc nanoparticles may be a promising candidate for some applications in high-efficiency low-voltage phosphor, solar cells and biological luminescent labels.

ZnO-ZnS QDs interfacial heterostructure for drug and food delivery application: enhancement of the binding affinities of flavonoid aglycones to bovine serum albumin.

Zero-dimensional nanostructures are green nanomaterials that have recently attracted increasing attention. However, very little information is available on whether or not these heterostructures affect drug transport in blood. In current work, flavonoid aglycones were studied for their affinities for bovine serum albumin (BSA) in the presence and absence of zinc oxide-zinc sulfide quantum dots (ZnO-ZnS QDs) in vitro. The fluorescence intensity of BSA decreased remarkably with increasing concentration of ZnO-ZnS QDs, resulting in an obvious red-shift of the maximum emission of BSA from 340 to 348 nm. The magnitudes of binding constants in the presence of QDs ranged from 10(4) to 10(6) L/mol, and the number of binding sites per BSA molecule (n) was determined as 1.12 ± 0.17. Although ZnO-ZnS QDs significantly increased the affinities for BSA of myricetin, luteolin, gallocatechin gallate, tectorigenin, and formononetin, they barely affected the binding affinities of flavone, (-)-epicatechin gallate, and quercetin. FROM THE CLINICAL EDITOR: Serum albumins are major transport proteins in blood that reversibly bind fatty acids, amino acids, drugs, and inorganic ions, which interactions have important effects on the distribution, free concentration, and metabolism of drugs in blood. In this research nine flavonoid aglycones were studied for their affinities for bovine serum albumin (BSA). Interestingly it was found that presence of ZnO-ZnS QDs significantly increased the affinities of BSA for several of these aglycones.

Transparent poly(methyl methacrylate)/ZnO nanocomposites based on KH570 surface modified ZnO quantum dots.

Transparent luminescent ZnO embedded PMMA polymer has been synthesized by means of grafting poly(methyl methacrylate) (PMMA) onto the surface of ZnO QDs after g-methacryloxypropyl trimethoxy silane (KH570) modification. The resulting ZnO/PMMA nanocomposites with KH570-modified nanoparticles have better dispersibility and preserve the superior luminescence of ZnO nanoparticles in the nanocomposites. The obtained PMMA/ZnO nanocomposite films show high transparency, high UV-shielding efficiency and improved thermal stability. The obtained nanocomposite was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray powder diffraction (XRD), thermogravimetry (TG), ultraviolet-visible (UV-vis) absorption spectroscopy.

Efficient polycrystalline silicon solar cells with double metal oxide layers.

Crystalline silicon solar cells can achieve high power conversion efficiency and can be successfully commercialized; however, the exploration of optimization strategies is still necessary. Here, we demonstrated improved performance of a polycrystalline silicon solar cell by depositing Sb2Ox/CdO double layers onto a Si wafer via a low-cost route. The metal oxide layers, forming effective heterojunctions, suppressed carrier recombination and reduced surface reflection. Additionally, the heterojunctions of Sb2Ox/CdO/Si enhanced the transmission of electrons and holes and simultaneously, a wider response range in the solar spectrum was realized. The power conversion efficiency improved from 12.6 to 16.7% in a polycrystalline silicon solar cell, with relative increase of 33%. It is expected that the metal oxide-enhanced devices will have tremendous potential in commercial applications.

Greatly Enhanced Photovoltaic Performance of Crystalline Silicon Solar Cells via Metal Oxide.

Band-gap alignment engineering has now been extensively studied due to its high potential for application. Here we demonstrate a simple route to synthesize two metal oxide layers and align them together according to their bandgaps on the surface of crystalline silicon (c-Si) solar cells. The metal oxide layers not only extend absorption spectrum to generate extra carriers but also more efficiently separate electron⁻hole pairs. As a consequence, the photovoltaic performance of SnO2/CdO/Si double-layer solar cell (DLSC) is highly improved compared to the controlled Si solar cell, CdO/Si and SnO2/Si single-layer solar cells (SLSCs). Via alignment engineering, the SnO2/CdO/Si DLSC produces a short circuit photocurrent (Jsc) of 38.20 mA/cm², an open circuit photovoltage (Voc) of 0.575 V and a fill factor (FF) of 68.7%, a conversion efficiency (η) of 15.09% under AM1.5 illumination.

Tunable morphologies, multicolor properties and applications of RE3+ doped NaY(MoO4)2 nanocrystals via a facile ligand-assisted reprecipitation process.

Rare earth (RE3+)-doped NaY(MoO4)2 nanocrystals are efficient materials for realizing multicolor emission, which plays an important role in displays, W-LEDs, solar cells and biolabeling. Up to now, research on the multicolor tuning properties of RE3+-doped NaY(MoO4)2 nanoparticles has mostly focused on traditional preparation routes such as the hydrothermal method and sol-gel process. However, the products obtained using these methods are usually large in size (on the micron/submicron scale) and agglomeration problems are inevitable. With the development of nano optoelectronic devices and bioluminescence labeling, there is an urgent need to find an efficient method to prepare nanoscale, monodispersed and NaY(MoO4)2:RE3+ nanocrystals (NCs) with good crystallinity and stronger emission properties. In this work, we demonstrate a simple, fast, reproducible and one-step synthesis of NaY(MoO4)2:Eu3+ NCs with sizes varying from 1-20 nm via a ligand-assisted reprecipitation strategy. The reaction mechanism and emission intensities of NaY(MoO4)2:Eu3+ NCs with various morphologies have been discussed in detail. Furthermore, Tb3+ and Eu3+ ion co-doped NaY(MoO4)2 NCs were also prepared, and various emission colors were obtained and tuned from red, orange-red, yellow and yellow-green to green. Energy transfer between the Tb3+ and Eu3+ ions in the NaY(MoO4)2 host matrix has also been demonstrated. Finally, a highly efficient and stable NaY(MoO4)2:0.05Tb,0.04Eu NC-based W-LED device was built, which indicates the promising future application for this material in the field of lighting. The tunable multicolour emission, ease of preparation and nanosize reveal that NaY(MoO4)2:RE3+ NCs have a potential application in full color displays and W-LEDs.

A hierarchical CoFeS2/reduced graphene oxide composite for highly efficient counter electrodes in dye-sensitized solar cells.

Transition metal sulfides are a kind of potential candidates for efficient and stable CE materials in DSSCs due to their good electrocatalytic ability and stability towards I3- reduction. However, the low conductivity of sulfides is harmful for the electron collection and transfer process, and the absorption/desorption and diffusion process of I-/I3- should be optimized to achieve high electrocatalytic activity over Pt. Herein, a hierarchical CoFeS2/reduced graphene oxide (CoFeS2/rGO) composite was rationally designed and prepared via the in situ conversion of CoFe layer double hydroxide anchored on rGO. Due to the synergistic effects of Co and Fe, unique 3D hierarchical structures formed by nanosheets, and the conductivity of rGO, the CoFeS2/rGO CEs exhibited good electrocatalytic activity and stability towards the reduction of I3- to I-, and the DSSCs could also achieve a high efficiency of 8.82%, higher than those of the devices based on Pt (8.40%) and pure CoFeS2 (8.30%) CEs. Moreover, the devices also showed the characteristics of fast activity onset, good stability, and high multiple start/stop capability. The results indicated that the developed CoFeS2/rGO composite could be a promising alternative for Pt in DSSCs.

[Synthesis and photoluminescence properties of Tb(3+) -acetylacetone ternary complexes doped with La3+ or Y3+].

Four series of solid complexes including RE(x) Tb(1-x) (acac)3 phen and RE(x) Tb(1-x) (acac)3 bipy (RE = La, Y; x = 0, 0.10, 0.20, 0.30, 0.50, 0.70, 0.90, 1.00) were synthesized. These complexes were characterized by IR spectra and XRD. Photoluminescence (PL) properties of these complexes were studied. The relation between their fluorescence intensities and the content of doped ions was also discussed. The experimental results show that the PL intensity of Tb3+ was sensitized by La3+ or Y3+ , and La3+ is better than Y3+ in enhancing the fluorescence of Tb3+. When x = 0.1-0.3, the fluorescence intensities of most doped complexes are stronger than their corresponding pure Tb3+ complex.

Enhancement of white-light-emission from single-phase Sr5(PO4)3F:Eu(2+),Mn(2+) phosphors for near-UV white LEDs.

A series of single-phase broadband white-light-emitting Sr5(PO4)3F:Eu(2+),Mn(2+) phosphors were prepared by a solid state reaction. The luminescence property, and the crystal and electronic structures of the fluorophosphates were studied by photoluminescence analysis, XRD Rietveld refinement and density functional theory calculation (DFT), respectively. Under near ultraviolet excitation in the 250 to 430 nm wavelength range, the phosphors exhibit two emission bands centered at 440 and 556 nm, caused by the Eu(2+) and Mn(2+) ions. By altering the relative ratios of Eu(2+) and Mn(2+) in the compounds, the emission color could be modulated from blue to white. The efficient energy transfer from the Eu(2+) to Mn(2+) ions could be ascribed to the well crystallized host lattice and the facile substitution of Eu(2+) and Mn(2+) for Sr(2+) sites due to similar ionic radii. A series of fluxes were investigated to improve the photoluminescence intensity. When KCl was used as flux in the synthesis, the photoluminescence intensity of Sr5(PO4)3F:Eu(2+),Mn(2+) was enhanced by 85% compared with no fluxes added. These results demonstrate that the single-phase Sr5(PO4)3F:Eu(2+),Mn(2+) with enhanced luminescence efficiency could be promising as a near UV-convertible direct white-light-emitting phosphor for WLED applications.

Tunable solar-heat shielding property of transparent films based on mesoporous Sb-doped SnO2 microspheres.

In this paper, mesoporous antimony doped tin oxide (ATO) microspheres are synthesized via a solvothermal method from a methanol system with the surfactant followed by a thermal treatment process. Morphology studies reveal that the spherical products obtained by polyvinylpyrrolidone (PVP) templating result in a higher uniformity in size. Such obtained ATO microspheres with a secondary particle size ranging between 200 and 800 nm consist of packed tiny nanocrystals and have high specific surface area (∼98 m(2) g(-1)). The effect of Sb doping on the structural and electrical properties of SnO2 microspheres is studied. Because of the substitution of Sn(4+) with Sb(5+) accompanied by forming a shallow donor level close to the conduction band of SnO2, a lower resistivity of powder pellet can be achieved, which corresponds to the spectrally selective property of films. The application of ATO microspheres provides an example of transparent coatings; depending on Sb concentration in SnO2 and solid content of coatings, transparent films with tunable solar-heat shielding property are obtained.

[IR and Raman spectra of ternary solid complexes of rare earth with alpha-naphthoic acid and 1,10-phenanthroline].

Five ternary solid complexes of rare earth with alpha-naphthoic acid (HNaP) and 1,10-phenanthroline (Phen) were prepared. These complexes all have the composition of RE(Nap)3.phen (RE3+ = Y, La, Eu, Tb, Dy). IR and Raman spectra were investigated. Assignment of complex bands were made by searching group vibration frequencies. Vibrational spectra indicate that carboxylate ions in the alpha-naphthoate take the bidentate coordination modes and the nitrogen atoms in 1,10-phenanthroline are coordinated and format five number chelate ring.

Drug delivery property, bactericidal property and cytocompatibility of magnetic mesoporous bioactive glass.

A multifunctional magnetic mesoporous bioactive glass (MMBG) has been widely used for a drug delivery system, but its biological properties have been rarely reported. Herein, the effects of mesopores and Fe3O4 nanoparticles on drug loading-release property, bactericidal property and biocompatibility have been investigated by using mesoporous bioactive glass (MBG) and non-mesoporous bioactive glass (NBG) as control samples. Both MMBG and MBG have better drug loading efficiency than NBG because they possess ordered mesoporous channels, big specific surface areas and high pore volumes. As compared with MBG, the Fe3O4 nanoparticles in MMBG not only provide magnetic property, but also improve sustained drug release property. For gentamicin-loaded MMBG (Gent-MMBG), the sustained release of gentamicin and the Fe3O4 nanoparticles minimize bacterial adhesion significantly and prevent biofilm formation against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Moreover, the magnetic Fe3O4 nanoparticles in MMBG can promote crucial cell functions such as cell adhesion, spreading and proliferation. The excellent biocompatibility and drug delivery property of MMBG suggest that Gent-MMBG has great potentials for treatment of implant-associated infections.

Synthesis of the bismuth oxyhalide solid solutions with tunable band gap and photocatalytic activities.

Three series of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions were systematically synthesized through a low-temperature precipitation. These solid solutions were characterized by XRD, FESEM, TEM, EDS, UV-vis spectra, nitrogen sorption/desorption, and PL. The tunable band gaps of the as-prepared solid solutions were realized via only changing the molar ratio of two halide ions. Meanwhile, the influence of citric acid in the formations of controllable morphological structures was discussed to study the growth mechanism of solid solutions. The photocatalytic activities of the bismuth oxyhalide solid solutions have also been investigated by the degradation of Rhodamine-B (RhB) under visible light irradiation. The optimized solid solutions possess higher photocatalytic activity than pure ones [BiOM (M = Cl, Br, I)] due to the broadened range of visible light response and the reduced recombination rate of electron-holes pairs. The results show that the synthesis of BiOM(x)R(1-x) (M, R = Cl, Br, I) solid solutions have profound significance for the design of the novel photocatalyst materials.