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Carbon dots with a size of 5 nm were synthesized through hydrothermal synthesis by recycling discarded coffee powder. In the Raman signal, the typical D (1364 cm−1) and G (1563 cm−1) bands of Sp 2 carbon were detected, and when excited at 324 nm, a blue, wide-range emission spectrum signal was detected. The synthesized carbon dots were mixed with a solution containing 10 ppm of Pb, Cr, and Cd to be used in the field of detecting metal ions in a solution state. Carbon dots that reacted with metal ions lost their unique blue luminescent color and showed that they could be used as metal ion detection sensors. In addition, spherical particle CaWO 4 :Eu3+ phosphor powder was synthesized and prepared by coprecipitation at room temperature. The synthesized phosphor had a tetragonal structure, and a strong signal from the (112) plane, the main peak, was detected in the XRD pattern, showing excellent crystallinity. When excited at 267 nm, a strong red emission signal of 613 nm was detected, and when the synthesized carbon dots were impregnated and made into a composite, an emission spectrum was observed in a wide range from blue to red, showing white color. This composite was mixed with PDMS to make a flexible sheet and applied to a UV-LED chip, suggesting that it could be used as a white light-emitting device. [ABSTRACT FROM AUTHOR]

• Y 2 Sn 2 O 7 :Eu3+ phosphors were synthesized by a sol-gel method. • The phosphors exhibit excellent reddish orange emission with dominant peak at 589 nm upon excitation at 273 nm. • CIE coordinates of the phosphors was measured as (0.6086, 0.3906). • Y 2 Sn 2 O 7 :Eu3+ phosphors have potential to be used as color convert for latent fingerprint detections and anti-counterfeit security ink. In forensic science, fingerprint detection and anti-counterfeiting technologies are crucial. Inorganic phosphors are potentially suitable materials for high-quality visualization and security. We synthesized novel Y 2 Sn 2 O 7 :Eu3+ (YSO:Eu3+) phosphors by a sol–gel method. They have a cubic structure and emit reddish orange emission from the Eu3+ ions electronic transition of 5D 0 →7F 1. The optimal doping concentration of Eu3+ is 7 mol% and dipole-dipole interaction causes the quenching mechanism. The chromaticity coordinates of YSO:7Eu3+ phosphor are (0.6086, 0.3906). We used the optimized YSO:7Eu3+ phosphors for forensic applications, such as latent fingerprints and security ink. The latent fingerprints stained with YSO:7Eu3+ phosphors showed clear images and reliable level 1–3 characteristics. The security ink was visible on different surfaces. Our results indicate that the YSO:7Eu3+ phosphor can be used for visualizing latent fingerprints and anti-counterfeiting applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Latent fingerprints provide crucial affirmations of identity in forensic science. However, they are microscopic. In this study, novel fluorescence materials, Ba 2 LaSbO 6 :Mn4+ (BLSO:Mn4+) phosphors, were developed by a sol–gel method for the fluorescence imaging of latent fingerprints. The structural properties of the phosphors were investigated by powder X-ray diffraction (XRD) and its Rietveld refinement analyses, and transmission electron microscopy and scanning electron microscopy techniques. The photoluminescence properties of the BLSO:Mn4+ phosphors were evaluated comprehensively by recording the emission, excitation, and decay curves. The BLSO:Mn4+ phosphors provide a high-intensity red emission at 677 nm under 350 nm excitation caused by the 2E g →4A 2g transition of Mn4+. The optimum concentration of Mn4+ in the BLSO host was determined to be ~0.2 mol%. The calculated Commission International de L'Eclairage (CIE) chromaticity coordinates (0.716, 0.283) of the emission from the BLSO:Mn4+ phosphor are located in the pure red region of the CIE 1931 diagram. The red-emitting BLSO:0.2Mn4+ phosphor was used as a fluorescence imaging powder for visualizing latent fingerprints on various substrates with high resolution, high contrast, and high efficiency, as well as good selectivity. [ABSTRACT FROM AUTHOR]

Crystalline CaWO 4 was synthesized by a co-precipitation method at room temperature. XRD peak at a position like that in the reference pattern, and the signal was detected from the (112) plane. Raman signals suggested the presence of symmetrical vibrations of the WO 4 bond. The absorption was observed in the UV region, and the bandgap calculated from the Tauc plot was 4.47 eV. When the sample was excited at 230 nm, blue emission with a peak at 430 nm was observed. Crystalline CaWO 4 was doped with Dy3+ ions to synthesize a white light-emitting phosphor. The addition of Dy3+ ions altered the crystal structure and shifted the Raman signals slightly. The sample was excited at 230 nm, both 430 nm and 575 nm emissions were observed, and the intensity of the 575 nm emission increased with increasing Dy3+ concentration. The CaWO 4 : 0.1 Dy3+ sample showed the highest luminescence intensity, and excessive doping decreased the luminescence intensity owing to concentration quenching. The photoluminescence decay lifetime initially increased with increasing Dy3+ concentration but decreased at concentrations greater than 0.1 mol% because of concentration quenching. The synthesized white light emitting CaWO 4 :Dy3+ powder was mixed with PDMS to form a flexible composite. The composite could be easily bent with a finger and emitted white light when applied on a UV-LED chip. [Display omitted] • Crystalline microsphere CaWO 4 :Dy3+ particle was synthesized at room temperature by co-precipitation. • Investigation of structure and luminescence properties according to Dy3+ concentration. • Fabricated as a flexible composite showed white light emission when applied to UV-LED. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The yellow-emitting Y 2 BaAl 4 SiO 12 :Ce3+ phosphors were synthesized by a sol-gel method. • Y 2 BaAl 4 SiO 12 :Ce3+ phosphors can be efficiently excited under the blue light. • Y 2 BaAl 4 SiO 12 :Ce3+ phosphors exhibit excellent yellow emission under blue light. • Y 2 BaAl 4 SiO 12 :Ce3+ phosphors are promising yellow phosphor for the fabrication of WLED. Abstract Yellow-emitting Y 2 BaAl 4 SiO 12 :Ce3+ (YBAS:Ce3+) phosphors were synthesized by a sol-gel method followed by annealing at high temperature. The phase purity of the YBAS:Ce3+ phosphors was confirmed by X-ray diffraction analysis. The emission characteristics of YBAS:Ce3+ phosphors were investigated by measuring their photoluminescence excitation and emission spectra. These phosphors can be efficiently excited with blue light that induced an intense yellow emission peak centered at 530 nm. White light-emitting diodes (WLEDs) were fabricated using the synthesized YBAS:6Ce3+ phosphors. The CIE chromaticity coordinates of YBAS:6Ce3+ and the fabricated WLEDs were located at the yellow (0.391, 0.563) and cool white-light (0.265, 0.326) regions, respectively. [ABSTRACT FROM AUTHOR]

Fingerprints provide significant unique identification of individuals. Fingerprint technology requires luminescent materials with high contrast, high selectivity, low background interface and high efficiency. Herein, a red-emitting La 2 Ti 2 O 7 :Eu 3+ phosphors are synthesized by a solvothermal reaction method for latent fingerprint application. The structural properties are investigated by the X-ray diffraction analysis, Rietveld refinement and Raman spectroscopy. The optical properties are studied by the measurement of diffused reflectance, excitation and emission spectra. The PLE spectra of La 2 Ti 2 O 7 :Eu 3+ phosphor exhibits both host absorption and charge transfer bands along with f-f transitions of Eu 3+ ions. The PL spectra exhibit an intense red emission due to the 5 D 0 → 7 F 2 transition with the CIE chromaticity coordinates (0.614, 0.383). The latent fingerprints on the surface of various substrates are developed and exhibit excellent visualization with clear papillary ridges under the UV illumination of 254 nm. These results suggest that the La 2 Ti 2 O 7 :Eu 3+ phosphors are promising luminescence materials for latent fingerprint technologies. [ABSTRACT FROM AUTHOR]

Bi 4 Si 3 O 12 :Eu 3+ phosphors are synthesized by a solvothermal reaction method. The structural properties are investigated using the X-ray diffraction patterns, which confirmed the cubic phase with a space group I-43d. The optical properties are studied by the measurement of diffused reflectance, excitation and emission spectra. The photoluminescence (PL) excitation spectra of Bi 4 Si 3 O 12 :Eu 3+ phosphor exhibits a broad band between 220 and 350 nm with two peaks occurring around 271 and 297 nm corresponding to the host absorption and charge transfer bands, respectively, and several sharp peaks due to the f–f transitions of Eu 3+ ions in the wavelength over 350 nm. The PL spectra exhibit blue emission due to the 1 S 0  →  3 P 1 transition of Bi 3+ and red emission due to the 5 D 0  →  7 F 2 transition of Eu 3+ . With increase of Eu 3+ concentration, blue emission decreased and red emission increased. At the concentration of 3 mol% Eu 3+ , Bi 4 Si 3 O 12 :Eu 3+ phosphors show white emission with the CIE chromaticity coordinates (x = 0.345, y = 0.327). These results suggest that the Bi 4 Si 3 O 12 :Eu 3+ phosphors are promising luminescence materials for UV based white light emitting diodes. [ABSTRACT FROM AUTHOR]

The fingerprints are commonly latent for detection at crime scenes and thus the effective way for analysis and detection of latent fingerprints is important. Currently, the traditional powder dusting method has low resolution, sensitivity, contrast and high background noise. To solve these problems, we synthesized the Ce 3+ doped strontium phosphate phosphors (Sr 10 (PO 4 ) 6 O:xCe 3+ , x = 0.01–0.1 mol) with cyan color by a facile solid state reaction route. The X-ray diffraction patterns of Sr 10 (PO 4 ) 6 O:xCe 3+ phosphors confirmed the hexagonal phase. The emission peak centered at 472 nm is attributed to 5 D 3/2  →  7 F J transitions (J = 7/2 and 5/2) of Ce 3+ ions with the CIE coordinates value of (x = 0.171, y = 0.256). Using Sr 10 (PO 4 ) 6 O:Ce 3+ phosphors, the latent fingerprints with various ridge shapes (arch, whorl and loop) and on substrates (glass, aluminum foil, stainless steel, compact disk and credit card) exhibited excellent visualization and sensitivity with clear ridges under 254 nm UV illumination. The results indicate that Sr 10 (PO 4 ) 6 O:Ce 3+ phosphors can be effectively used in fingerprint identification and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Novel yellow-emitting Ca 5 (Zn 1- x Mg x ) 4 (VO 4 ) 6 self-activated phosphors were synthesized via a sol-gel method. The X-ray diffraction showed their typical cubic garnet structure. The photoluminescence excitation spectra of Ca 5 (Zn 1- x Mg x ) 4 (VO 4 ) 6 phosphors exhibited a broadband ranging from 250 to 430 nm, which was originated from the [VO 4 ] 3− group charge transfer transition. For the emission spectra, Ca 5 Zn 4 (VO 4 ) 6 and Ca 5 Mg 4 (VO 4 ) phosphors exhibited the characteristic broadband emissions between 420 and 750 nm with highest intensities at 538 and 533 nm, respectively. The calculated CIE coordinates were (0.331, 0.476) and (0.318, 0.463) for Ca 5 Zn 4 (VO 4 ) 6 and Ca 5 Mg 4 (VO 4 ) 6 yellow phosphors, respectively. The results hint that these luminescent powders may be good candidates for their potential use in the fabrication of rare-earth elements free WLEDs. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2 ) spheres were synthesized by a solvothermal reaction methodand sintered at different temperatures. The mixed anatase and rutile phase was observed at 800 °C and these were transformed to pure tetragonal rutile phase at above 900 °C. The size of TiO 2 spheres was increased by increasing the sintering temperature. The diffused reflectance spectra exhibited a higher reflectance for rutile than that of anatase phase. White light-emitting diodes (WLEDs) were fabricated by combining the mixture of TiO 2 spheres and commercial YAG:Ce 3+ phosphors with blue LED chip. The fabricated WLEDs with the combination of rutile TiO 2 spheres, commercial YAG:Ce 3+ phosphor, and blue LED chip to improve the light-extraction efficiency of about 43.6% than that of the fabricated WLEDs with combinations of commercial YAG:Ce 3+ and blue LED chip. [ABSTRACT FROM AUTHOR]

Novel deep red-emitting Ca 14 Al 10 Zn 6 O 35 :Mn 4+ (CAZ:Mn 4+ ) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction patterns of CAZ:Mn 4+ phosphors confirmed their cubic structure after annealing at 1200 °C. The photoluminescence emission (PL) and excitation (PLE) spectra were measured to examine the emission richness of CAZ:Mn 4+ phosphors. The PLE spectra of CAZ:Mn 4+ phosphor exhibited a broad band, between UV and blue regions, due to the charge transfer (CT) transition of Mn 4+ -O 2- and 4 A 2g → 4 T 2g , 4 A 2g → 4 T 2g , 4 A 2g → 4 T 2g of Mn 4+ ions. The results showed that the deep red emission peak of the CAZ:Mn 4+ phosphor was located at 714 nm due to the 2 E g → 4 A 2g transition of Mn 4+ ion, which was effectively excited by 450 nm. The optimum concentration of Mn 4+ ion in Ca 14 Al 10 Zn 6 O 35 host lattice was found to be at 3 mol%. Using CAZ:3Mn 4+ phosphors, white light-emitting diode (WLED) was fabricated. The CIE chromaticity coordinates of CAZ:3Mn 4+ and fabricated WLED located at (0.709, 0.291) and (0.338, 0.396), respectively, resulting in the generation of warm white light for indoor illumination. [ABSTRACT FROM AUTHOR]

Fingerprints have been used in forensic investigation for the identification of individuals. Herein, we report a novel red-emitting Eu 3+ ions activated rhombohedral Y 4 Zr 3 O 12 nanophosphors for latent fingerprint technology. The synthesized nanophosphors exhibited the rhombohedron-like morphology. The photoluminescence (PL) excitation spectra of Y 4 Zr 3 O 12 :Eu 3+ exhibited the both charge transfer and the f-f transition bands of Eu 3+ ions. The PL emission spectra displayed an intense red emission ( 5 D 0 → 7 F 2 ) with the color coordinates of (0.640, 0.359). The optimum concentration of Eu 3+ ion in Y 4 Zr 3 O 12 host lattice has been found to be at 10 mol%. Using Y 4 Zr 3 O 12 :Eu 3+ nanophosphors, the latent fingerprints on different surfaces has been developed and exhibited excellent visualization with clear papillary ridges under 254 nm UV-lamp. These results suggest that the Y 4 Zr 3 O 12 :Eu 3+ nanophosphors are promising red-emitting material for the visualization of latent fingerprints. [ABSTRACT FROM AUTHOR]

Red-emitting GdSr 2 AlO 5 :Eu 3+ phosphors were synthesized by a modified citrate sol-gel route. The tetragonal phase of the GdSr 2 AlO 5 :Eu 3+ phosphors were confirmed by measuring the XRD patterns. The photoluminescence excitation (PLE) and emission (PL) properties of these phosphors were carried out to analyze their emission performance. The PLE spectra of the GdSr 2 AlO 5 :Eu 3+ phosphors exhibited the high intense charge transfer band and typical f–f transitions of Eu 3+ ions. The PL spectra of GdSr 2 AlO 5 :Eu 3+ phosphors unveiled the red emission with the band centered at 625 nm, which is originated from the 5 D 0 → 7 F 2 transition. The Eu 3+ ion concentration in the GdSr 2 AlO 5 host lattice was optimized with respect to the 5 D 0 → 7 F 2 transition intensities, and was found to be at 4 mol%. The decay curves data of the GdSr 2 AlO 5 :Eu 3+ phosphors were well fitted with a single exponential function. [ABSTRACT FROM AUTHOR]

A series of Eu 2+ ions doped BaZrSi 3 O 9 phosphors were synthesized by a solvothermal reaction method. The X-ray diffraction patterns of BaZrSi 3 O 9 :Eu 2+ phosphors confirmed their hexagonal structure after the samples were sintered above 1300 °C. The photoluminescence properties of BaZrSi 3 O 9 :Eu 2+ phosphors were explored by measuring the excitation and emission spectra, and decay curves. The excitation spectra of BaZrSi 3 O 9 :Eu 2+ phosphors consist of broad bands in the ultraviolet (UV) region due to 4 f 8 →4 f 7 5 d 1 transition of Eu 2+ ions. The sintering temperature and Eu 2+ ion concentration of BaZrSi 3 O 9 :Eu 2+ phosphors were optimized based on the dominant cyan emission intensity under the near-UV excitation. The optimum doping concentration of Eu 2+ ions was 3 mol% and the critical distance was calculated to be 23.245 Å. These luminescent powders are expected to be a potential candidate for solid-state lighting based white light-emitting diodes and optical display systems. [ABSTRACT FROM AUTHOR]

The novel red-emitting Eu 3+ ions activated CaGd 2 (MoO 4 ) 4 phosphors were prepared by a citrate sol–gel method. The X-ray diffraction patterns confirmed their tetragonal structure when the samples were annealed above 600 °C. The photoluminescence excitation spectra of CaGd 2 (MoO 4 ) 4 :Eu 3+ phosphors exhibited the charge transfer band (CTB) and intense f–f transitions of Eu 3+ ion. The optimized annealing temperature and Eu 3+ ion concentration were analyzed for CaGd 2 (MoO 4 ) 4 :Eu 3+ phosphors based on the dominant red ( 5 D 0 → 7 F 2 ) emission intensity under NUV (394 nm) excitation. All decay curves were well fitted by the single exponential function. These luminescent powders are expected to find potential applications such as WLEDs and optical display systems. [ABSTRACT FROM AUTHOR]

Abstract: A series of Ce3+ ions doped GdSr2AlO5 (GSA) phosphors were synthesized by a citric acid based sol–gel method. The X-ray diffraction patterns confirmed their tetragonal structure after the samples were annealed at 1300°C, and the scanning electron microscope image showed the closely packed particles. The excitation spectra revealed that the GSA phosphor effectively excited with blue light of 442nm due to the 4f1→5d1 transition and exhibited yellow emission corresponding to the 5d1→4f1 transition of Ce3+ ions. The optimum doping concentration of Ce3+ ions was 5mol% and the critical distance was calculated to be ~17Å. White LEDs were fabricated by combining blue LED (465nm) chip with Ce3+:GSA phosphor. The CIE chromaticity coordinates (0.34, 0.31) provide their emission potentiality in the white light region. [Copyright &y& Elsevier]

Highlights: [•] Ca8Gd2(PO4)6O2:Eu2+, Eu3+ ultrafine nanorods are prepared by a hydrothermal method. [•] Ammonia and EDTA play a key role in the formation of nanorods. [•] The effect of EDTA on the nanorod morphology is investigated. [•] Eu ions from Ca2+ and Gd3+ sites emit the bluish-green and red colors, respectively. [•] Nanorods exhibit hydrophilic nature, which is a basic requirement for bio applications. [Copyright &y& Elsevier]

Abstract: The color rendering index (CRI) and structural stability of cerium doped yttrium aluminum garnet (YAG:Ce) based phosphors have been enhanced by replacing Y3+ ions by larger radius ions (Tb3+, Gd3+, Eu3+, and Sm3+) at the dodecahedral site and replacing Al3+ ions by larger ones (Ga3+, Y3+, Tb3+, Gd3+, and Sm3+) at the octahedral site. These aluminum garnet crystalline powders were prepared by solvothermal reaction method at 300 °C for 48 h. The lattice constant values of synthetic aluminum garnet crystalline powders are larger than that of YAG and the emission wavelength of Ce3+ ion of these samples is longer than that of YAG:Ce. FESEM and TEM studies revealed that the Ln3Ga2Al3O12 and Ln3Al2Al3O12 crystalline powders have 3-dimensional star-like morphology with submicron size and good crystallinity, while, Ln3(LnAl)Al3O12 garnet crystalline powders were cubic crystalline phases and shaped as cubes with the round edge having an approximate diameter of about 200–400 nm. All the prepared powders were grown along (100) direction and crystallized into single crystal. Also, the effects of treatment time and reaction temperature on the structure of aluminum garnet crystalline powders have been investigated. [Copyright &y& Elsevier]

Nanocrystalline Ca2Gd8Si6O26 ( CGS): Sm3+ phosphors were synthesized by solvothermal reaction method. The structural and morphological properties of the samples were evaluated by X-ray diffraction and scanning electron microscopy. The photoluminescence excitation and emission spectra along with decay properties were investigated as a function of Sm3+ concentration. Under 405 nm excitation wavelength, the photoluminescence spectra showed three emission peaks at 565 nm (4G5/2 → 6H5/2) and at 650 nm (4G5/2 → 6H9/2), and with an intense orange emission at 600 nm (4G5/2 → 6H7/2). Based on the orange emission performance, the Sm3+ concentration was optimized to be at 2 mol%. The low voltage cathodoluminescence ( CL) properties were also performed for 2 mol% Sm3+-doped CGS phosphors as a function of accelerating voltage (1-5 kV). From the CL spectra, the reddish-orange emission was observed. The calculated Commission International De I-Eclairage chromaticity coordinates are in close proximity to the chromaticity coordinates of Nichia corporation developed amber light emitting diodes. [ABSTRACT FROM AUTHOR]

Abstract: Blue and green light emissive nanocrystalline Ca2Gd8Si6O26 (CGS):Tm3+ and CGS:Er3+ phosphors with high color purity were prepared by solvothermal reaction method. The structural and morphological properties of these phosphors were evaluated by the powder X-ray diffraction (XRD) and scanning electron microscopy, respectively. From the XRD results, Tm3+:CGS and Er3+:CGS phosphors had the characteristic peaks of oxyapatite in the hexagonal lattice structure. The visible luminescence properties of phosphors were obtained by ultraviolet (UV) or near-UV light and low voltage electron beam (0.5–5kV) excitation. The photoluminescence and cathodoluminescence properties were investigated by changing the variation of Tm3+ or Er3+ concentrations and the acceleration voltage, respectively. The CGS:Tm3+ phosphors exhibited the blue emission due to 1D2→3F4 transition, while the CGS:Er3+ phosphors showed the green emission due to 4S3/2→4I15/2 transition. The color purity and chromaticity coordinates of the fabricated phosphors are comparable to or better than those of standard phosphors for lighting or imaging devices. [Copyright &y& Elsevier]

Abstract: Bi3+ and Tb3+ ions co-doped GdAlO3 (GAP) nanophosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GAP phosphor confirms their orthorhombic phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of GAP:Tb3+, Bi3+ phosphors consist of a broad band in the shorter wavelength region due to the 4f8 →4f75d1 transition of Tb3+ ions overlapped with the 6s2 →6s16p1 (1S0 → 3P1) transition of Bi3+ ions and some sharp peaks in the longer wavelength region due to f→f transitions of Tb3+ ions. The present phosphors exhibit green color due to strong 5D4 → 7F5 transition of Tb3+ ions. The emission intensity was enhanced by co-doping with Bi3+ ions under 292nm excitation, which indicate that the efficient energy transfer occurred from Bi3+ to Tb3+ ions. [Copyright &y& Elsevier]

Abstract: A series of Eu3+ ions co-doped (Gd0.9Y0.1)3Al5O12:Bi3+, Tb3+ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi3+, Tb3+, Eu3+ phosphors consists of broad bands in the shorter wavelength region due to 4f8 → 4f75d1 transition of Tb3+ ions overlapped with 6s2 → 6s16p1 (1S0 → 3P1) transition of Bi3+ ions and the charge transfer band of Eu3+–O2−. The present phosphors exhibit green and red colors due to 5D4 → 7F5 transition of Tb3+ ions and 5D0 → 7F1 transition of Eu3+ ions, respectively. The emission was shifted from green to red color by co-doping with Eu3+ ions, which indicate that the energy transfer probability from Tb3+ to Eu3+ ions are dependent strongly on the concentration of Eu3+ ions. [Copyright &y& Elsevier]

Abstract: Y (10mol%) substituted GAG:Ce (GdYAG:Ce) phosphors have been synthesized by solvothermal reaction method and which were sintered at various temperatures. The XRD patterns confirm that the GdYAG:Ce phosphors have garnet structures with a single cubic phase. GdYAG:Ce phosphors were stable with pure garnet phase at higher temperatures and lower concentration of Y3+ ions. The SEM images of these phosphors show spherical morphology. The luminescent properties of these phosphors have been investigated by the measurement of their emission and excitation spectra. The excitation spectra of GdYAG:Ce phosphors consist of a broad band with a maximum at 485nm and also the emission spectra of these phosphors emit the reddish yellow colors with a peak intensity at 546nm from the measured spectra. [Copyright &y& Elsevier]

Abstract: Dy3+:GAP (gadolinium aluminum perovskite) powder nanophosphors have been newly synthesized by means of solvothermal process. Spherically shaped particles in the nanometer ranges prepared by this method were evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The synthesis, structural and luminescent properties along with chromaticity coordinates of the nanophosphor samples with the compositions xDy3+:Gd(1− x )AlO3 (x =0.005–0.05) are featured in this paper. Furthermore, the yellow to blue intensity ratio of Dy3+:GAP nanophosphors varies from 1.19 to 1.03. Such luminescent powders are expected to find potential applications such as optical display systems. [Copyright &y& Elsevier]

Owing to the great thermal stability, phosphor-in-glass (PiG) is a promising color converter for the laser diode (LD) excitation based high-power white light-emitting LDs. Here, we reported the rapidly developed PiG plates using a facile microwave irradiation technique where the YAG:Ce3+ phosphor embedded with soda-lime silica glass. The effects of phosphor content and microwave irradiation energy were studied for investigating the optimal performance of PiG plate. To evaluate the practical applicability, the luminescence and thermal properties of the PiG plate was compared with the commercial YAG:Ce3+ single-crystal. The PiG plate and YAG:Ce3+ single-crystal individually combined with blue LD exhibited the white light with the CIE color coordinates of (0.3016, 0.3098) and (0.3254, 0.3555), respectively. The maximum surface temperature of the PiG plate was found to be about 96.1 °C, which is much lower than the YAG:Ce3+ single-crystal of 124 °C. The change in the CIE color coordinate of the PiG with aging time is smaller than that of YAG:Ce3+ single-crystal. This PiG plate might provide an important implication to overcome current limitation of LD driven solid state laser lighting. • First report on the microwave irradiation method of phosphor-in-glass (PiG). • The PiG color converter exhibits excellent thermal stability. • The change in CIE color coordinate of the PiG color converter shows smaller than that of YAG:Ce3+ single-crystal. • The PiG is a candidate of color converter in high-power laser diode. [ABSTRACT FROM AUTHOR]

Latent fingerprint detection is one of the promising technique in forensic science. Here, an oxide based red-emitting phosphors, CaGdAlO 4 :Eu3+ (CGA:Eu3+), have been successfully synthesized by a solvothermal reaction method. The structural phase was characterized with the XRD Rietveld refinement and TEM analyses. The luminescence properties and dynamics of Eu3+ in CGA were studied in detail by room temperature emission, excitation and decay curve measurements. Intense red emission peaking at 620 nm due to 5D 0 →7F 2 transitions of Eu3+ under the excitation at 283 nm was obtained and the optimal Eu3+ ion concentration was found to be about 7 mol%. The CIE chromaticity coordinate evaluated from the PL spectra and exhibited (0.6410, 0.3581) coordinates within the pure red region of the CIE 1931 diagram with a close proximity to the commercial red phosphor (Y 2 O 2 S:Eu3+). Furthermore, with the use of the CGA:7Eu3+ phosphors, the developed latent fingerprint fluorescent images were well visualized and identified their level 1, 2 and 3 details with high contrast, selectivity and sensitivity. These results indicate that CGA:7Eu3+ has great potential for practical applications in the latent fingerprint detection. • CaGdAlO 4 :Eu3+ phosphors were synthesized by a solvothermal reaction method. • The phosphors exhibit excellent red emission with dominant peak at 620 nm upon excitation at 283 nm. • CIE coordinates of the phosphors was measured as (0.6410, 0.3581). • CaGdAlO 4 :Eu3+ has potential to be used as color convert for latent fingerprint detections. [ABSTRACT FROM AUTHOR]

Boron nitride (BN) was synthesized by pyrolysis of a molecular precursor prepared by chemical mixing of boric acid (H 3 BO 3) and melamine (C 3 H 6 N 6) with a small amount of europium nitrate (Eu3+) as luminescent materials. After pyrolysis, the Eu3+ ions were substitutionally incorporated into a B 3 N 3 hexagonal layer of turbostratic BN (t-BN) at a low doping level estimated to be less than 12 × 1018 atoms/cm3. This phenomenon is due to a randomly stacked turbostratic structure rather than a perfectly stacked hexagonal boron nitride (h-BN) structure along the c-axis. The photoluminescence (PL) spectrum of pure BN was detected at 456 nm (blue), and Eu3+-doped BN was detected at 590, 614, 648, and 696 nm (red) by excitation of UV light (λ = 314 nm). The PL intensity improved as the level of Eu3+ addition was increased. However, excessive doping caused the disappearance of the luminescent properties due to the concentration quenching phenomenon. When the synthesized nanoparticle BN phosphor was mixed with a polymer to form a flexible composite, it was shown that it could be applied as a filter to UV-LED. [Display omitted] • Crystalline BN:Eu3+ was synthesized at pyrolysis. • Structure and luminescence investigated properties according to Eu3+ concentration. • Fabricated as a flexible composite showed red light emission when applied to UV-LED. [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]

Gd 0.99-x VO 4 :Tm 3+ 0.01 /Yb 3+ x phosphors with different Yb 3+ concentration (0.01–0.07 mol) and sintering temperatures (450–600 °C) were synthesized by the planetary ball milling method. The structural properties were analyzed using the X-ray diffraction patterns, which conform the poly phase with Na 3 Gd(VO 4 ) 2 and GdVO 4 . Upconversion luminescence was investigated under the 975 nm laser diode. The upconversion spectra of Gd 0.99-x VO 4 :Tm 3+ 0.01 /Yb 3+ x show two emission peak in 1 G 4 → 3 H 6 (477 nm, blue) and 3 H 4 → 3 H 6 (802 nm, NIR) of the Tm 3+ transitions, together with the 2 F 5/2 → 2 F 7/2 transition of Yb 3+ . Gd 0.92 VO 4 :Tm 3+ 0.01 /Yb 3+ 0.07 phosphor sintered at 600 °C is expected to find potential applications such as blue LED by the near infra-red (NIR) excitation. [ABSTRACT FROM AUTHOR]

Abstract: Different concentrations of trivalent praseodymium (Pr3+) ions activated GdAlO3 nanophosphors were synthesized by solvothermal reaction method. Thermogravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD) measurements were used to investigate the phase transformations that occur during the preparation of these phosphors. The morphology of the powder after heat treatment was observed by scanning electron microscopy (SEM). The luminescent studies on these compounds have been carried out from the measurements of their photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The PL spectra show blue-green emission corresponding to the f–f transitions of Pr3+ (3P0 → 3H4) and red emission corresponding to the f–f transition of Pr3+ (3P0 → 3H6) by monitoring the excitation with f–f transition of Pr3+ (3H4 → 3P2) at 449 nm. Emission mechanism in these systems has also been elucidated by an energy level scheme. [Copyright &y& Elsevier]

Abstract: Eu3+ doped Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM) nanophosphors were prepared by solvothermal reaction method. The structural properties were studied by using their XRD measurements and the luminescent properties of these phosphors were investigated by the measurement of their excitation and emission spectra along with their decay curves. The relationship between the structures and the photoluminescence properties of the phosphors has been studied. The emission spectrum of Eu3+ doped YAG phosphor is dominated by orange emission due to 5D0 → 7F1 transition with inversion symmetry. However, the emission spectrum of Eu3+ doped YAP phosphor is dominated by red emission due to 5D0 → 7F2 transition without inversion symmetry. The PL spectrum of Eu3+ doped YAM phosphor consists of similar emission intensities for both 5D0 → 7F1 (590nm) and 5D0 → 7F2 (607nm) transitions. [Copyright &y& Elsevier]

Abstract: Different concentrations of dysprosium (Dy3+) doped gadolinium aluminates (GdAlO3) have been newly synthesized by the wet chemical route method. Very fine particles in the nanometer range could be prepared by this method, as evidenced by X-ray diffraction and SEM measurements. The XRD profile confirms their orthorhombic nature, which is well correlated with the reported results. Luminescence studies on these compounds have been carried out on the emission and excitation, along with lifetime measurements. Such luminescent powders are expected to find potential applications as new optical materials. The emission procedure in the system has also been elucidated by an energy level scheme. [Copyright &y& Elsevier]

Abstract: We reported the novel red-emitting phosphors of trivalent europium (Eu3+) ions activated CaGd4O7 (CG) prepared by a sol–gel method. After the samples were annealed at 1500°C, the X-ray diffraction patterns confirmed their monoclinic structure and the transmission electron microscopy image showed the nanocrystallinity of the CG: Eu3+ phosphor. The photoluminescence excitation spectra exhibited the efficient energy transfer from the Gd3+ to Eu3+ by overlapping the f–f transition of Gd3+ excitation band with charge transfer band of Eu3+ ions. The photoluminescence (PL) spectra showed the emission band in the entire visible region at lower Eu3+ concentration and the red emission at higher Eu3+ concentration. All the decay curves were well fitted by single exponential functions. The temperature dependent luminescence measurements were performed for identifying the thermal stability of CG: Eu3+ phosphors at elevated temperatures. The cathodoluminescent (CL) spectra also presented a similar behavior to that observed in PL spectra. Form the PL, CL, and decay analysis the optimum concentration of Eu3+ ions in the CG host lattice was found to be 5mol%. The CIE chromaticity coordinates varied from yellow to red in visible spectral region by increasing the Eu3+ concentration. [Copyright &y& Elsevier]

Abstract: Eu3+ activated oxyapatite Ca2Gd8Si6O26 (CGS) nanophosphors were synthesized using a solvothermal reaction method. The structural and luminescent properties of these nanophosphors were investigated as a function of sintering temperature and Eu3+ ion concentration. The SEM images of the prepared phosphors reveal spherically shaped particles in the nanometer range and the XRD patterns confirm their hexagonal structure. The photoluminescence excitation (PLE) spectra of Eu3+:CGS showed the charge transfer band (CTB) and intense f–f transitions of Eu3+ and Gd3+. The intensity of the f–f transitions of Gd3+ increases with increasing the sintering temperature and decreases with increasing the Eu3+ concentration. It was observed that the CTB of Eu3+ shifted to a shorter wavelength region with an increase the crystallite size due to the variation of coordination environments. The photoluminescence (PL) spectra of Eu3+:CGS exhibit two emission lines corresponding to the 5D0 → 7F0 transition which results from occupation of Eu3+ ions in two different low symmetry local sites in CGS host lattice. The optimized sintering temperature and concentration of Eu3+ were observed for Eu3+:CGS nanophosphors based on the dominant red (5D0 → 7F2) emission intensity under NUV (395nm) excitation. The decay curves of 5D0 level show that the lifetime decreases with increasing the crystallite size. These luminescent powders are expected to find potential applications such as WLEDs and optical display systems. [Copyright &y& Elsevier]

There are ongoing efforts to develop novel phosphors with the properties required to make an object look as natural as it does under sunlight. It has been proven that particle morphology influences the luminescent properties of a phosphor. The rare-earth pyrosilicates, such as La 2 Si 2 O 7 (LSO) are currently regarded as novel promising scintillators and protective pigments because of their good chemical and thermal stabilities. However, to date, there have been no reports available on the definite morphology of the LSO matrix and the precise luminescent properties of the trivalent europium (Eu3+)-doped LSO phosphor. Herein, we report the development of Eu3+-activated dumbbell-shaped LSO nanocrystalline phosphors using a two-step solvothermal and hydrothermal approach. After regrowth, the amorphous natured LSO:Eu3+ precursor was transformed into well-defined LSO:Eu3+ dumbbell-shaped nanocrystalline phosphors (LSO-R:Eu3+) with a pure monoclinic phase. The phase purity was verified by Rietveld refinement analysis. The formation mechanism of the dumbbell-shaped particles was evaluated using surface morphological studies, and the involvement of the crystal splitting mechanism was established. The luminescence spectra revealed robust red emission at 614 nm under ultraviolet (UV) and near-UV excitations. The dipole-dipole interactions between the neighboring Eu3+ ions induced the concentration quenching in LSO host matrix. Chromaticity coordinates (0.645, 0.342) emerged in the reddish-orange region and were comparable to the standard-definition and high-definition digital television coordinates (0.640, 0.330). Therefore, these results indicate that the synthesized LSO-R:Eu3+ dumbbell-shaped nanocrystalline phosphor is a promising auxiliary red component for assembling desired white light-emitting diodes for indoor illuminations. [ABSTRACT FROM AUTHOR]

• A Facile and efficient strategy has been used to synthesize the far-red phosphor. • Energy transfer has been verified by measuring 3D photoluminescence spectra. • The sensitizer has assisted in doubling the quantum efficiency. • The phosphor synthesized herein exhibited outstanding thermal and photostability. • The fabricated LED with NUV chip exhibited high-purity far-red emission. [Display omitted] Since the inception of white light-emitting diodes (white LEDs), phosphor-coated LEDs have been in focus owing to the tremendous advantageous that they offer in assorted applications ranging from biomedical to automotive applications, including plant growth. While, plant growth LEDs have been bustling the commercial market, there is ample scope to commercialize the promising far-red (FR) emitting LEDs for potential growth of plants in indoor farming. Herein, a facile and efficient strategy was used to develop Mn4+ (Nb site)- and Sm3+ (La site)- ions-doped Ca 2 LaNbO 6 (CLNO:Mn4+/Sm3+) phosphors with outstanding photoluminescence (PL) properties. The PL properties of CLNO:Mn4+ and CLNO:Sm3+ phosphors showed FR emissions at 650 and 697 nm, respectively. When Mn4+/Sm3+ ions were co-doped in a CLNO host lattice, Rietveld refinement revealed alterations in bond lengths of the CLNO crystal structure, which enhanced the phosphor's thermal stability and photostability and caused the creation of effective pathways for efficient energy transfer from Sm3+ to Mn4+ ions. Furthermore, the reverse strategy, where the sensitizer (Sm3+) concentration was changed instead of activator (Mn4+) concentration, was used to achieve brilliant FR emission from the CLNO:Mn4+/Sm3+ phosphors and the dominant emission was perceived for the CLNO:0.2Mn4+/1.5Sm3+ phosphor. The internal quantum efficiency of the CLNO:0.2Mn4+/1.5Sm3+ phosphor was increased from 28% (CLNO:0.2Mn4+) to 56%. An LED fabricated by coating a CLNO:Mn4+/Sm3+ phosphor layer on a near-ultraviolet LED chip exhibited excellent FR emission with high color purity and with chromaticity coordinates of (0.733, 0.267). The results obtained for the CLNO:0.2Mn4+/1.5Sm3+ phosphor along with the characteristics of fabricated LED showed the high potential of the phosphor for use in promoting indoor plant growth. [ABSTRACT FROM AUTHOR]