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A series of the TeO2–GeO2–ZnO glass system was single and double doped with different Tb3+/Eu3+ ratios. Their luminescent and colorimetric properties were analyzed for possible use as phosphor materials in lighting devices. The characterization by X-ray diffraction and Raman spectroscopy verified the glassy nature of the fabricated samples. The luminescent properties of the doped glasses were analyzed by means of steady-state fluorescence and time-resolved spectroscopy. The Tb3+ excitation bands observed in the codoped samples while monitoring the 700 nm emission of Eu3+, as well as the shortening of Tb3+ lifetime in presence of europium indicated a Tb3+ → Eu3+ energy transfer, which main interaction type is electric dipole–dipole, according to Inokuti–Hirayama model. The Eu3+ → Tb3+ energy transfer also occurs in the samples but with lower efficiency. The CIE1931 chromaticity coordinates, upon different excitation wavelengths, show a multicolor tunning from green to orange-red due to the lanthanide concentration ratio and the Tb3+ → Eu3+ energy transfer process. [ABSTRACT FROM AUTHOR]

Hydrothermally grown SnO2 and SnO2:Eu nanoparticles of 4-11 nm size range were analyzed by photoluminescence (PL) and therrmoluminescence (TL) spectroscopy to study the effect of Eu-doping on their emission behaviors. It has been observed that most of the incorporated Eu3+ ions remain at the interstitial sites of SnO2 lattice. High Eu-contents in the nanoparticles generate lattice deformation, formation of Eu3+/Eu0 clusters at interstitial sites, or segregation to their surfaces. Formation of Eu clusters at interstitial sites enhances electronic defect density in the crystal lattice, reorganizes carrier trapping centers, and modifies their activation energies. Room temperature PL emission and beta-irradiated TL dose response of SnO2 nanoparticles enhance significantly when doped with 0.5 and 1.0 mol. % nominal of Eu3+, respectively, opening up their possibilities of applications in bio-imaging and radiation therapy. Possible mechanisms of enhanced PL and TL responses of the samples have been discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • SnSrO 3 nanoparticles prepared by the sonochemical method and solid-state reactions. • Study of rare-earth doping effects on the structure and photoluminescent properties. • XRD results confirmed the orthorhombic phase of SrSnO 3. • Near-white light emission from Sm3+, Tb3+ co-doped SnSrO 3 perovskites. Sm3+, Tb3+ co-doped SrSnO 3 perovskites were successfully prepared by the sonochemical method and solid-state reactions. X-ray diffraction showed well-defined peak characteristics of the SrSnO 3 orthorhombic phase, while SEM analysis revealed the formation of rod-like structures composed of particles with a mean size of 100 nm. Under the excitation of 325 nm, the photoluminescence spectra exhibited a broad emission band (380–500 nm) related to intrinsic defects and peaks attributed to characteristic electronic transitions of Tb3+ (5D 4 →7F 6 , 489 nm, 5D 4 →7F 5 , 542 nm) and Sm3+ (4G 5/2 →6H 5/2 , 570 nm, 4G 5/2 →6H 7/2 , 605 nm) ions. Through co-doping with these rare earths, the emission from perovskite can be tuned. The obtained chromaticity coordinates are (0.33, 0.31) and (0.34, 0.32) for 4Sm2Tb and 4Sm4Tb perovskites, respectively. It indicates the promising application potential of Sm3+, Tb3+ co-doped SrSnO 3 as single-phase perovskite for UV excited white light-diodes. [ABSTRACT FROM AUTHOR]

• Convenient room-temperature gas sensing using ZnO nanorods thin films. • Detection of low concentration of methanol vapors using ZnO nanorods films. • Photoluminescence measurements of ZnO as an alternative method for gas detection. • Adsorption of various vapors and their role on the optical properties of ZnO. Zinc oxide (ZnO) nanorod films with thickness of 700 nm were prepared via a chemical bath deposition method using a ZnO seed layer deposited on a silicon substrate by a conventional dip-coating technique. The morphology and structural properties of the obtained ZnO nanorods were characterized by field emission scanning electron microscopy and Raman spectroscopy. Photoluminescence spectroscopy exhibited an intense emission located at 380 nm related to near band edge (NBE) recombination and a yellow emission band at 575 nm attributed to intrinsic defects of ZnO. Changes in intensity of the NBE and yellow emissions were determined through room-temperature photoluminescence measurements of ZnO nanorods films when exposed to vapors of ethanol, methanol and tequila-methanol mixtures respectively. ZnO nanorods based sensors showed rapid response times and moderate recovery times together with good selectivity for methanol and ethanol vapors. For tequila-methanol mixtures samples, the change in photoluminescence intensity of both said emissions of ZnO nanorods presented an opposite behavior in comparison against methanol and ethanol samples. Intensity changes of the NBE emission showed a linear trend depending on the increase in methanol concentration, while the yellow emission intensity presented an exponential trend for concentrations below 50 % of methanol in tequila. [ABSTRACT FROM AUTHOR]

The results presented here refer to the tunability of global emission characteristics of Eu3+, Dy3+ and Eu3+/Dy3+ ions, varying the composition glasses; TeO 2 -GeO 2 -X (X = ZnO, MgCl 2). Also, the influence of exchanging the modifier compound on the global luminescent response of the glasses was analyzed by Raman spectroscopy, excitation and emission spectra, and emission decay profiles. Changes in the Te-O-Te network structure, when MgCl 2 substitutes ZnO, were identified from Raman spectrum deconvolution analysis. The energy transfer between Eu3+ and Dy3+ ions, and tunable emission characteristics, were studied under UV excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The energy transfer process between Eu3+ and Dy3+ ions was studied based on the emission spectra with different excitation wavelengths and time decay curves of the 5D 0 →7F 2 level of Eu3+ at 612 nm. In TGZED and TGMED glasses and upon 351 nm, the time shortening of Dy3+ emission decay in presence of Eu3+ was attributed to an Dy3+→Eu3+ non-radiative energy transfer process. The energy transfer probabilities P D→E and energy transfer efficiency η D→E were calculated for TGZ and TGM glasses. According to the Inokuti-Hirayama model it might be dominated through an electric dipole-dipole interaction, with efficiency of 5.0% and 1.9% and the obtained γ 6 energy transfer parameter values γ 6 = 0.082 ± 0.005 and 0.026 ± 0.005 respectively, for TGZED and TGMED glasses. The non-radiative Eu3+→Dy3+ energy transfer was observed too for both glasses TGZED and TGMED, so that transfer of energy is more favored in the oxide vitreous matrix than in the oxide-halide one. The dominated are an electric dipole-dipole interaction with γ 6 energy transfer parameter values are 0.072 ± 0.005 (TGZED) and 0.036 ± 0.005 (TGMED), with efficiency 6.9 and 4.1% respectively. In TGM glasses is very low efficiency of non-radiative Dy3+→Eu3+ and Eu3+ →Dy3+ energy transfer that TGZ matrix. Neutral white emissions of 4135, 4567 K were observed in the Dy3+ and 3914 and 242 K, Eu3+/Dy3+ doped TGZ glasses excited at 351 and 388 nm, respectively. Similarly, global emissions of Dy3+ single doped were 4028 and 4123 K, but in Eu3+/Dy3+ double doped TGM glasses are neutral white light of 3929 and 3979 K, respectively. Upon 394 nm excitation, the Eu3+ doped TGZ and TGM glasses displayed reddish-orange global emissions of 1979 and 1964 K, respectively. For excitations at 382 and 394 nm the Eu3+/Dy3+ doped TGZ and TGM glasses emit warm white light of 3414 and 3160 K (382 nm excitation) and reddish-orange of 2123 and 2030 K (394 nm excitation), respectively, depending mostly on the Eu3+ and Dy3+ relative excitation intensity. [ABSTRACT FROM AUTHOR]