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In this work, the luminescence properties of YVO4:Dy3+ are modified by co-doping of alkali metals (M = Li, Na, and K), and the materials were prepared by hydrothermal technique followed by its calcination at 500 °C. By analyzing Powder X-ray Diffraction (P-XRD), SEM and TEM, Fourier transform infrared (FTIR), optical absorption and photoluminescence techniques, as well as UV-DRS spectroscopy of the as-prepared products, it was determined that co-doping of alkali metals affects the properties of crystal phase and photoluminescence. The P-XRD pattern reveals the formation of the tetragonal crystalline phase. On the other hand, morphological studies show that samples have regular bipyramidal structures. Functional group analysis shows the band near 500 cm−1 attributed to Y–O absorption. An intense band around 781 cm−1 corresponds to symmetrical stretching due to the V–O vibration of the VO43− group. Furthermore, in PL emission spectra, the most intense emission peak was observed at 573 nm, due to the 4F9/2 → 6H13/2 transition of Dy3+ on excitation at 320 nm. Among the above-described alkali metal ions (such as Li+, Na+, and K+), K+ effectively enhances the intensity of the prominent emission peak located at 573 nm. The optimum concentration of K+ ion co-doping for improvement in the photoluminescence properties of yttrium vanadate doped with Dy3+ phosphor was found to be 10 at.%. Tauc relation and Kubelka–Munk relation were used to calculate the band gaps of samples. The calculated band gaps of YVO4:5 at.%Dy3+:5 at.% M+ (M+ = Li+, Na+, and K+) and YVO4:5 at.%Dy3+:x at.% K+ (x = 0, 1, 3, 5, 7, 10 and 15) samples were found to be 3.42, 3.69,3.73 eV, 3.62, 3.61, 3.63, 3.62, 3.61, 3.60 and 3.62 eV, respectively. For YVO4:Dy3+, the (x,y) values of calculated CIE chromaticity color coordinates are (0.40, 0.47), which is in the yellow range and suitable for display device applications. [ABSTRACT FROM AUTHOR]

TiO2/Ag/TiO2 multilayer films have been deposited by Ion-beam sputtering technique with different Ag thickness. X-ray reflectivity technique with 3-layer fitting model has been used to calculate thickness, density, and roughness of the multilayer films. Gaussian fitting of XRD and Raman data is used to detect the crystalline growth of films while FTIR data confirm the presence of metal layer in the films. A phonon confinement effect originating from decrease in crystallite size is also observed with blue shift in some of the Raman active modes. Effect of Ag layer thickness on optical and electrical properties of multilayer films has been presented including a comparative study of our data with previously reported work on TiO2/Ag/TiO2 transparent conducting oxides. Transmittance of multilayer films in visible region (550 nm) has increased from 65 to 81% with increase in Ag thickness. The band gaps calculated from Tauc plot of these films follow Burstein–Moss effect. Sheet resistance has decreased from 15.41 to 5.92 Ω/□ while carrier concentration and mobility show an increasing trend from 5.94 × 1021 to 1.35 × 1022 and 6.83 to 13.72 cm2/Vs, respectively, with the increase in Ag mid-layer thickness. Haacke's Figure of Merit (FOM) is recorded to be 7.9 × 10−3 Ω−1. [ABSTRACT FROM AUTHOR]

Fluorescent ZnS:Mn quantum dots coated with hypro-mellose (HPMC) were synthesized by using simple and facile chemical precipitation technique in which HPMC acts as a novel organic surfactant to passivate the surface, to tune the optical properties and also to functionalize the surface of quantum dot for a futuristic controlled drug release applications. Morphological and optical characterizations were done to see the effect of HPMC coating on ZnS:Mn quantum dots. Structural and morphological studies was done by using XRD and TEM respectively. XRD studies confirms the pure zinc blende phase for all the samples. TEM studies shows that HPMC is efficiently doing the surface passivation in doped quantum dots. Optical studies were done by using UV-visible, FTIR and time resolved photoluminescence. UV-visible studies shows that quantum confinement effect is more prominent and also tunable in case of HPMC coated manganese doped ZnS quantum dots. FTIR studies confirms the functionalization of HPMC on the surface of doped ZnS quantum dots. Laser induced time resolved photoluminescence studies were also done to see the effect of HPMC on the photoluminescence intensity of doped quantum dots. Time resolved studies clearly shows the much desired luminescence stability of the HPMC coated quantum dots. It is observed that both the structural and optical characteristics have strong dependence on capping concentration. As HPMC is a very important viscoelastic polymer and organic surfactant used in various types of drug formulations, these studies opens a new way in the area of efficient drug delivery, controlled drug release and targeting. [ABSTRACT FROM AUTHOR]