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Since the commercialization of white light-emitting diodes (WLEDs) in 1996, they are rapidly replacing conventional lighting sources and have become an essential commodity for day-to-day human life. At present, most of the WLEDs existing in the market are rare-earth based, which are very limited, expensive and often not available due to monopolistic supply conditions. Hence, there is a serious demand for novel rare-earth free phosphors to achieve cost-effective and energy-efficient WLEDs with excellent luminous efficacy for general illumination. Herein we report on highly efficient rare-earth free Cs(1−x)RbxVO3 phosphors as a single emitting compound for near UV-based WLEDs manufactured by the citrate sol–gel method for the first time. Rietveld refinement is performed for the X-ray diffraction patterns of the CsVO3 host and CsVO3:0.25Rb phosphors to reveal their orthorhombic pyroxene structure. The difference in the ionic radii of Rb+ and Cs+ ions led to a more distorted VO43− tetrahedron with a broken Td symmetry, which allows spin forbidden transitions for CsVO3:0.25Rb phosphors, resulting in enhanced internal and external quantum efficiencies of 94.7% and 84.5% along with superior luminescence properties compared to the CsVO3 host. When varying the input current from 20 to 200 mA, the fabricated WLED exhibited a good color rendering index of 69.7–81.5 and an extremely high luminous efficacy of 94.8–58.7 lm W−1, which are among the highest values for the same host lattice. These rare-earth free CsVO3:0.25Rb phosphors with a single emitting center may emerge as a new class of advanced inorganic phosphors for near UV-based WLEDs in the lighting industries. [ABSTRACT FROM AUTHOR]

Evolution of a simple, efficient and reproducible strategy for the rational design of hierarchically structured metal chalcogenide-based supercapacitors has attracted considerable research interest in recent years. Herein, a facile wet-chemistry approach is employed to design three-dimensional forest-like porous nickel sulfide nanotrees on nickel foam (NiS NTs/Ni foam) for use as a cathode material in hybrid supercapacitors. The growth time plays a crucial role in controlling the surface morphology, and the optimal growth conditions (3 h at 85 °C) led to the growth of forest-like NiS NTs/Ni foam with reliable adherence. The forest-like NiS NTs/Ni foam shows maximum areal and specific capacities of 752.71 μA h cm−2 and 342.1 mA h g−1 at a current density of 4 mA cm−2, with an excellent cycling stability of 89.4%. This result is primarily due to the availability of more surface-active sites in the well-defined hierarchical architecture, which allow the rapid diffusion of electrolyte ions and minimize the electron transport limitation. Utilizing the hierarchical NiS NTs/Ni foam as a cathode and activated carbon-based anode, we further fabricated a hybrid supercapacitor, which demonstrates a wide potential window of 1.6 V with high areal energy and power densities of 0.472 mW h cm−2 and 21.5 mW cm−2, respectively. The fabricated hybrid supercapacitor is successfully utilized to drive various electronic gadgets for real-life applications. The electrochemical performance of a hierarchically structured NiS-based binder-free electrode with our facile approach paves a new pathway for the development of novel metal chalcogenides for high-performance hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

We report a facile and large-scale synthesis of size-tunable and nontoxic mesoporous silica-coated Gd2O3:Eu3+ (Gd@mSi) core–shell nanostructures using a TPAOH assisted modified UHP technique. The role of TPAOH in controlling the particle size was evaluated. The potentiality of these Gd@mSi core–shell nanoparticles before and after folic acid conjugation was established by in vitro fluorescence microscopy of the U2OS cell lines for cancer imaging and therapy. [ABSTRACT FROM AUTHOR]

Nanostructured inorganic materials are potential building blocks for advanced materials and devices with desired functions. Latent fingerprint technology requires cost-effective and high-quality luminescent nanomaterials to identify an individual with sufficient information. We report the synthesis and growth mechanism of novel nanostructured CaGd2ZnO3(CO3)2·H2O and CaGd2ZnO5 materials through a urea- and EDTA-mediated hydrothermal process. The conversion from the carbonate to the oxide form is explained using physicochemical measurements. Furthermore, when doped with Eu3+ ions, CaGd2ZnO5 nanostructures exhibit superior luminescent properties to replace conventional red phosphors for latent fingerprint technology. In contrast to previously reported individual fluorescent nanoparticles, CaGd2ZnO5:5Eu3+ nanostructures provide three levels of identification with high-quality imaging on various hydrophilic and hydrophobic substrates. These properties demonstrate that CaGd2ZnO5:Eu3+ nanorod bundles are a promising luminescent material for solid-state lighting and latent fingerprint technologies. [ABSTRACT FROM AUTHOR]

Single, double and triple trivalent rare-earth (RE3+ = Dy3+, Tm3+, Tm3+/Dy3+ and Tm3+/Dy3+/Eu3+) ions activated Sr2Gd8(SiO4)6O2 (SGSO) phosphors were synthesized by a sol–gel process. X-ray diffraction profiles confirmed their oxyapatite structure after annealing at 1450 °C for 12 h. Morphological studies were performed by taking scanning and transmission electron microscopy images, which displayed rod-like shapes. SGSO phosphors exhibited good photoluminescence (PL) properties in the respective regions when doped with Dy3+ and Tm3+ ions. Dy3+ co-activated SGSO:Tm3+ phosphors revealed tunable emissions from cool white light to warm white light towards the yellow region based on the co-activator concentration. However, Eu3+ ions co-doped SGSO:Tm3+/Dy3+ phosphors tuned the emissions towards the red region. The energy transfers from Tm3+ to Dy3+ ions and Tm3+/Dy3+ to Eu3+ ions were established based on the energy level diagram. The cathodoluminescence properties of these phosphors showed excellent emission behavior when the single, double or triple trivalent RE ions were doped into the SGSO host lattice. Unlike the case of the PL, the energy transfer process was observed to take place. The calculated Commission Internationale de l'Eclairage chromaticity coordinates of Tm3+ and Dy3+ individual ion doped SGSO phosphors confirmed the blue and white emissions, while the co-doped samples exhibited tunable emissions. [ABSTRACT FROM AUTHOR]

A series of Eu3+ ions activated Ba4La6(SiO4)6O (BLSO:Eu3+) phosphors were synthesized by a modified citrate sol–gel process. The structural properties of these phosphors were explored by means of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The XRD patterns confirmed their oxyapatite structure with the space group of P63/m after annealing at 1400 °C. The scanning electron microscope image exhibited the irregular morphology of BLSO:Eu3+ particles and the elemental mapping confirmed that the Eu3+ ions were distributed homogeneously on the La3+ ion sites. Photoluminescence (PL) excitation spectra of BLSO:Eu3+ exhibited the charge transfer band (CTB) and intense f–f transitions of Eu3+ ions in the violet and blue wavelength regions. The CTB intensity decreased and the f–f transition of Eu3+ ions increased with increasing the Eu3+ ion concentration due to the presence of defects in the 4f and 6h sites of the BLSO host lattice. This feature facilitates the strong absorption in the near-ultraviolet (NUV) region, which is useful for high color rendering index NUV based white light-emitting diodes for display and lighting applications. The PL spectra displayed intense red emission (5D0→7F2) along with considerable orange emission (5D0→7F1) with good asymmetry ratios and chromaticity coordinates, and exhibited better emission performance than that of commercial Y2O3:Eu3+ phosphors. The three-dimensional PL spectra revealed their strong emission characteristics under UV, NUV and visible excitation wavelengths. The cathodoluminescence properties were also similar to the PL results, confirming that the BLSO:Eu3+ phosphors emit stable red emission under different excitation sources as compared to the commercial Y2O3:Eu3+ phosphors. [ABSTRACT FROM AUTHOR]

Oriented attachment assisted self-assembled three-dimensional (3D) flower-like La(OH)3:Eu3+ nanorod bundles were successfully synthesized by a facile wet-chemical method. Hexamethylenetetramine played an important role in the formation of the hexagonal phase of La(OH)3:Eu3+ with respect to the reaction time and its concentration. No other surfactants or capping agents were used. The calcination temperature did not show any influence on the morphological texture, and the La2O3:Eu3+ phase was obtained by a subsequent annealing process. The phase formation and morphological properties were confirmed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photoluminescence properties were studied for both the synthesized La(OH)3:Eu3+ and La2O3:Eu3+ samples, and also compared with that of the solid-state reaction based La2O3:Eu3+ phosphor. The 3D flower-like La2O3:Eu3+ nanorod bundles showed an intense red emission due to the hypersensitive 5D0→7F2 transition with good asymmetric ratio and chromaticity coordinates. Likewise, a systematic study of the cathodoluminescence (CL) properties was carried out in detail. Furthermore, to estimate the CL potentiality, the La2O3:Eu3+ phosphor was compared with a commercially available Y2O3:Eu3+ red phosphor. [ABSTRACT FROM AUTHOR]

GdPO 4 :Eu 3+ nanorods (~20 nm) were synthesized by a facile hydrothermal technique based on the water/2-PrOH interface. The size of nanorods was controlled by varying the reaction temperature and solvent interface. After calcination at 700 °C, the hexagonal phase of as-prepared GdPO 4 ·H 2 O:Eu 3+ nanorods was transformed into the monoclinic phase, which was confirmed by XRD patterns and TEM images. During the calcination process, along with the phase transformation, the size of nanorods was also shortened by the removal of H 2 O molecules from the lattice. Photoluminescence (PL) excitation spectra revealed the efficient energy transfer between Gd 3+ and Eu 3+ ions and the orange-red emission was typically observed from PL spectra because the Eu 3+ ions exist with inversion symmetry in the lattice. Also, these GdPO 4 :Eu 3+ nanorods were highly dispersible in water. [ABSTRACT FROM AUTHOR]

Although much progress has been made in treating cancers, cancer death rates in and around the United States are still high. Current treatments are either ineffective against some cancers or detrimental to patients, which decreases their quality of life. The use of nanotechnology in cancer therapy can potentially increase patient survival, reduce side effects, and reduce mortality rates because nanoparticles (NPs) have the potential to target only tumors and bypass healthy cells. NPs possess many features, including size, shape, charge, and composition, which allow them to carry chemotherapeutics to cancer cells. NPs can also be used in radiotherapy as radiosensitizers and in imaging as contrast agents. Many studies have performed in vitro and/or in vivo experiments on these particles in human and animal cell lines. This review discusses recent studies on different NPs and their potential use in cancer therapy. [ABSTRACT FROM AUTHOR]

Red color-emitting CaGd2ZnO5:Eu3+ (CGZO:Eu3+) nanophosphors were synthesized by a facile sol–gel process. The structural and luminescent properties of these phosphors were investigated as a function of annealing temperature and Eu3+ ion concentration. The orthorhombic phase was confirmed at different annealing temperatures, showing an irregular morphology within the nanoscale range. Photoluminescence (PL) excitation spectra of CGZO:Eu3+ showed host absorption band (HAB), charge transfer band (CTB), and intense f–f transitions of Eu3+ in the violet and blue wavelength regions. The CTB intensity increased and the HAB intensity decreased with increasing annealing temperature or Eu3+ ion concentration. The CGZO:Eu3+ exhibited a strong absorption in the blue region as compared to the CTB and had a superior property compared to available commercial phosphors. This feature facilitates the fabrication of high color rendering index white light-emitting diodes for display systems. In PL spectra, an intense red emission was observed due to the hypersensitive 5D0→7F2 transition with good asymmetry ratio and chromaticity coordinates. Optimized annealing temperature and concentration of Eu3+ ions were observed for CGZO host lattice based on the 466 nm excitation wavelength. The cathodoluminescent properties were also similar to the PL results. [ABSTRACT FROM AUTHOR]

Trivalent lanthanide (Eu3+, Tb3+ and Dy3+) ions activated tunable color emitting BaGd2O4 (BG) phosphors were synthesized by a facile Pechini-type sol–gel process. The X-ray diffraction pattern confirmed the orthorhombic phase after annealing at 1300 °C for 5 h. Morphological studies were performed based on the analysis of transmission electron microscopy images, which showed needle type nanorods. The BG phosphor exhibited good photoluminescence (PL) properties in the respective regions when doped with Eu3+, Tb3+ and Dy3+ ions. The Eu3+ co-activated BG:Tb3+ phosphor yielded tunable emissions including tri-band established white light emission based on the co-activator concentration and excitation wavelength. The energy transfer from Tb3+ to Eu3+ ions was controlled by selecting a suitable excitation wavelength and the decay measurements were carried out for analyzing the energy transfer efficiency. The cathodoluminescence properties of these phosphors were almost similar to PL properties when doped with individual Eu3+, Tb3+, and Dy3+ ions, but were different when co-doped with Eu3+/Tb3+ or Eu3+/Dy3+ ions. In the case of Eu3+/Tb3+ doped samples, the energy transfer process occurred unlike the PL channel. The calculated Commission International de l'Eclairage chromaticity coordinates of individual ion doped BG phosphors confirmed red, green, and white emissions and for co-doped samples they showed tunable emission. [ABSTRACT FROM AUTHOR]

RE3+ (Er3+/Tm3+/Yb3+) ions tri-doped SrY2O4 nanocrystalline phosphors were synthesized by a citrate sol–gel method. After annealing at 1300 °C, the structure was identified to be pure orthorhombic and the particles were found to be nearly spherical in shape. The up-conversion emission spectra of the SrY2O4:1Er3+ phosphor revealed a bright green emission (4S3/2→4I15/2) around 551 nm. To enhance the red emission of the Er3+ ions, Yb3+ ions were co-doped with Er3+ ions, leading to a greenish yellow emission under 980 nm excitation. In the case of the 1Er3+/1Tm3+/3Yb3+ ions tri-doped phosphor, white-light emission was observed corresponding to the 1G4→3H6 (Tm3+), 4S3/2→4I15/2 (Er3+) and 4F9/2→4I15/2 (Er3+) transitions at 487, 551 and 664 nm, respectively. It was interestingly noticed that, when the exciting pump power was changed from 100 to 900 mW, the blue emission band of the Tm3+ ions was enhanced by the suppression of the red and green emission bands of the Er3+ ions so that the chromaticity coordinates were also moved to the cyan emission region. This feature suggests that the Er3+ ion may also act as a sensitizer for the Tm3+ and Yb3+ ions and a possible energy transfer mechanism was also discussed. [ABSTRACT FROM AUTHOR]

Tm3+/Er3+/Eu3+/Er3+, Tm3+/Er3+/Eu3+ single, double and triple activator ion/ions doped nanocrystalline BaGd2O4 (BG) phosphors were prepared by a Pechini type sol-gel process. After annealing at 1300 °C, X-ray diffraction patterns confirmed their orthorhombic structure. Field-emission transmission electron microscope images of the BG sample indicated a nanoneedle-type morphology. Photoluminescence (PL) and cathodoluminescence (CL) measurements were utilized to establish the emission properties of rare-earth ions doped nanocrystalline BG host lattice. Under near-ultraviolet (NUV) excitations, BG:Tm3+ and BG:Er3+ exhibited their characteristic emissions in the blue and green regions, respectively, while BG:Tm3+/Er3+ and BG:Tm3+/Er3+/Eu3+ showed cyan and white light emissions, respectively, when doped with appropriate amounts of activator ions. In the PL, the cross-relaxation process is dominant rather than the energy transfer process. Due to the different mechanism from PL, the CL spectra showed different emission features of BG: Tm3+/Er3+/Eu3+ phosphor. The CL spectra of BG:Tm3+ and BG:Er3+ established the high purity blue and green emissions, respectively. From the PL and CL investigations, the white-light emission was realized from the single-phase BG:Tm3+/Er3+/Eu3+ phosphor under NUV and low voltage electron beam excitations. [ABSTRACT FROM AUTHOR]

Mesoporous particles are emerging as multifunctional biomaterials for imaging and drug delivery in several disease models, including cancer. We developed PEGylated α-Gd2(MoO4)3 marigold flower-like mesoporous particles for the purpose of drug delivery and, more specifically, evaluated their ability to deliver curcumin. The obtained mesoporous particles significantly conjugated the curcumin particles on their surfaces by inducing the formation of curcumin nanoparticles. In vitro studies of the PEGylated mesoporous particles filled with curcumin demonstrated that these particles could considerably facilitate the continuous and sustained release of curcumin into the cytoplasm and nucleus. As a result, the intracellular release of curcumin can inhibit proliferation in two human pancreatic cancer cell lines: MIA PaCa-2 and PANC-1. Additionally, the particles showed the increased inhibition of pIKKα, pIKKα/β and NF- κB-DNA binding activity as compared to pure curcumin. The curcumin conjugated mesoporous particles are concentrated in the cytoplasm and nucleus of the treated cancer cell lines. Consequently, these mesoporous particles are an effective method for drug delivery that can cross the biological barriers of the body targeting the cellular nucleoplasm. [ABSTRACT FROM AUTHOR]

Trivalent rare-earth (RE3+ = Eu3+, Tb3+, Dy3+, and Sm3+) ions activated Gd2O(CO3)2·H2O chrysanthemum-like flowers are prepared by a modified urea-based homogeneous precipitation via a template free hydrothermal synthesis route. Subsequently, Gd2O3 monodispersed spheres were obtained after calcining at 750 °C. The growth mechanism of the Gd2O(CO3)2·H2O:RE3+ chrysanthemum-like morphology (homogeneous precipitation) and their transformation to monodispersed spheres (heterogeneous nucleation) are established by taking scanning electron microscope and transmission electron microscope images of the intermediate products. The thermogravimetric analysis, Fourier transform infrared analyses confirmed the decomposition of CO2 and OH groups, and the corresponding XRD patterns exhibited the Gd2O(CO3)2·H2O and cubic Gd2O3 phases. The photoluminescence measurements are used to explore the emission behavior of different RE3+ ions activated Gd2O3 spheres. The Gd2O3:Eu3+ shows gorgeous red emission with high purity red color as compared to the commercial Y2O3:Eu3+ phosphors. Gd2O3:Tb3+, Gd2O3:Dy3+ and Gd2O3:Sm3+ exhibit green, yellow and rich orange emissions, respectively. The Tb3+/Eu3+ co-doped sample shows warm white light by controlling the energy transfer. At minimal parameters, the cathodoluminescence intensity of Gd2O3:Eu3+ is beyond the experimental limit for 5 kV of accelerating voltage. The CIE chromaticity coordinates were also calculated from the PL and CL spectra of RE3+ ions to establish their color richness. [ABSTRACT FROM AUTHOR]

Pyrochlore-structured yttrium titanate phosphors activated by trivalent europium ions (Y2Ti2O7(YT):Eu3+), with spherical morphology, were synthesized at different pH values by a solvothermal process. From the structural and morphological measurements, the annealing temperature had no effect on the spherical morphology of the YT:Eu3+ sample. The photoluminescence excitation and emission spectra were taken by activating the Eu3+ ions in the YT host lattice as functions of Eu3+ ion concentration and annealing temperature. The optimal doping concentration was found to be 4 mol%, exhibiting an excellent orange-red emission due to the highest intensity of the 5D0 → 7F1 transition. When the YT:Eu3+ phosphor was mixed with YAG:Ce3+ phosphor, a brilliant white light emission was achieved. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Eu3+ ions activated Gd2O3 flower-like phosphor powders were prepared by a facile synthesis route. The growth mechanism was examined using the scanning electron microscope images as a function of reaction time. The X-ray diffraction pattern confirmed the cubic structure. The excitation spectra showed the efficient energy transfer from the Gd3+ to Eu3+ ions and the emission spectra exhibited the strongest emission band at wavelengths of ∼611nm. The Eu3+ concentration was optimized to be 5mol%. The emission intensity and color purity of Gd2O3:5mol% Eu3+ were high as compared to the commercial Y2O3:Eu3+ phosphor. [Copyright &y& Elsevier]

Novel hybrid decontamination processes based on visible-light-responsive photocatalysts (VLPHS) have recently become a focus of environmental research. In this study, the sonophotocatalytic degradation of the antibiotic tetracycline (TC) using a binary rGO/CdWO 4 composite under simulated visible-light irradiation was demonstrated for the first time. Structural characterization confirmed that flower-like CdWO 4 particles with a wolframite phase structure were successfully immobilized on the surface of the graphene oxide (GO). Subsequently, reduced GO/CdWO 4 (rGO/CdWO 4) VLPHS were prepared via the facile photocatalytic reduction of GO/CdWO 4. A Box-Behnken design based on response surface methodology (RSM) was employed to determine the maximum efficiency of sonophotocatalytic degradation by optimizing the process parameters (pH, initial TC concentration, treatment time, and catalyst dosage). The high determination coefficients (R 2 = 0.9818 and adjusted- R 2 = 0.9636) indicated that the experimental values fitted the proposed RSM model well. Compared with CdWO 4, rGO/CdWO 4 VLPHS exhibited significant photoelectrochemical (PEC) performance, superior sonophotocatalytic activity, and mineralization efficiency. The enhanced catalytic activity was mainly due to the larger optical adsorption range, greater photo-induced charge carrier transfer, and higher surface area. In addition, rGO/CdWO 4 exhibited a catalytic activity that was 1.5 and 3 times higher than that of commercial nano–ZnO and –TiO 2 , respectively. The kinetic analysis indicated that the degradation rate of TC follows the Langmuir–Hinshelwood kinetic model. The possible photocatalytic mechanism behind the degradation of TC by rGO/CdWO 4 was also tentatively proposed. This study provides a simple and scalable pathway to produce highly efficient rGO-based VLPHS for photocatalytic and PEC applications. Unlabelled Image • Facile wet chemistry is reported for the synthesis of rGO/CdWO 4 photocatalysts. • Tetracycline (TC) completely degraded by sonophotocatalysis. • rGO/CdWO 4 exhibits superior sonophotocatalytic activity over nano-ZnO and nano-TiO 2. • Maintaining the high sonophotocatalytic activity after four cycles of reusability tests • Sonophotocatalytic mechanism for degradation of TC over rGO/CdWO 4 was proposed. [ABSTRACT FROM AUTHOR]

White light-emitting diode (WLED) products currently available on the market are based on the blue LED combined with yellow phosphor approach. However, these WLEDs are still insufficient for general illumination and flat panel display (FPD) applications because of their low color-rendering index (CRI < 75) and high correlated color temperature (CCT = 6000 K). Although near-ultraviolet (UV) LED chips provide more efficient excitation than blue chips, YAG:Ce3+ phosphors have very weak excitation in the near-UV spectral region. Hence, there is an increasing demand for novel yellow phosphor materials with excitation in the near-UV region. In this work, we report novel self-activated yellow Ca5Zn3.92In0.08(V0.99Ta0.01O4)6 (CZIVT) phosphors that efficiently convert near-UV excitation light into yellow luminescence. The crystal structure and lattice parameters of these CZIVT phosphors are elucidated through Rietveld refinement. Through doping with In3+ and Ta5+ ions, the emission intensity is enhanced in the red region, and the Stokes shift is controlled to obtain good color rendition. When a near-UV LED chip is coated with a combination of CZIVT and commercial blue Ba0.9Eu0.1MgAl10O17 phosphors, a pleasant WLED with a high CRI of 82.51 and a low CCT of 5231 K, which are essential for indoor illumination and FPDs, is achieved. [ABSTRACT FROM AUTHOR]