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Yb3+/Er3+codoped La10W22O81 (LWO) nanophosphor rods have been successfully synthesized by a facile hydrothermal assisted solid state reaction method, and their upconversion photoluminescence properties were systematically studied. X-ray diffraction patterns revealed that the nanophosphors have an orthorhombic structure with space group Pbcn (60). A microflowers-like morphology with irregular hexagonal nanorods was observed using field emission scanning electron microscopy for the Yb3+(2 mol%)/Er3+(2 mol%):LWO nanophosphor. The shape and size of the nanophosphor and the elements along with their ionic states in the material were confirmed by TEM and XPS studies, respectively. A green upconversion emission was observed in the Er3+: LWO nanophosphors under 980 nm laser excitation. A significant improvement in upconversion emission has been observed in the Er3+: LWO nanophosphors by increasing the Er3+ ion concentration. A decrease in the upconversion emission occurred due to concentration quenching when the doping concentration of Er3+ ions was greater than 2 mol%. An optimized Er3+(2 mol%): LWO nanophosphor exhibited a strong near infrared emission at 1.53 μm by 980 nm excitation. The green upconversion emission of Er3+(2 mol%): LWO was remarkably enhanced by co-doping with Yb3+ ions under 980 nm excitation because of energy transfer from Yb3+ to Er3+. The naked eye observed this upconversion emission when co-doping with 2 mol% Yb3+. In order to obtain the high upconversion green emission, the optimized sensitizer concentration of Yb3+ ions was found to be 2 mol%. The upconversion emission trends were studied as a function of stimulating laser power for an optimized sample. Moreover, the NIR emission intensity has also been enhanced by co-doping with Yb3+ ions due to energy transfer from Yb3+ to Er3+. The energy transfer dynamics were systematically elucidated by energy level scheme. Colorimetric coordinates were determined for Er3+ and Yb3+/Er3+: LWO nanophosphors. The energy transfer mechanism was well explained and substantiated by several fluorescence dynamics of upconversion emission spectra and CIE coordinates. The results demonstrated that the co-doped Yb3+(2 mol%)/Er3+(2 mol%): LWO nanophosphor material is found to be a suitable candidate for the novel upconversion photonic devices.

The photoluminescence properties of lithium borate glasses doped with Tb3+ and Eu3+ ions individually and together were explored. The combination of bright green and orange-red emissions from the optimized glasses can generate white light under ultraviolet excitation. The red emission of Eu3+ ions was remarkably improved by external doping with Tb3+ ions by means of energy transmission from Tb3+ to Eu3+. The correlated color temperature and chromaticity coordinates were significantly changed from warm reddish to cool white region in Eu3+ and (Tb3++Eu3+):lithium borate glassy matrices, respectively, which were found to be a good candidates for white light emitting device applications.

Individually and doubly doped Ce3+/Eu3+:CaLa2ZnO5 (CLZO) phosphors were synthesized by a conventional sol-gel method as highly efficient luminescence-based phosphor materials. X-ray diffraction and field-emission scanning electron microscope were used to analyze the structural and morphological properties. The elements and their ionic states were determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy studies, respectively. The assignment of the functional groups was analyzed using Fourier-transform infrared spectral studies. Bright red emission was obtained from Eu3+-doped CLZO phosphors due to its hypersensitive transition of 5D0→7F2 at 626 nm with a royal blue excitation source. By increasing the Eu3+ content, the emission features were rapidly enhanced. Moreover, the red emission related to Eu3+ was further increased by the addition Ce3+ ions as a co-dopant along with Eu3+ in the CLZO matrix due to energy transfer. The energy migration from Ce3+ to Eu3+ is systematically illustrated by several fluorescent approaches, such as photoluminescence analysis, spectral overlap, CIE coordinates, lifetime dynamics, luminescence quantum yields, and color purity. Surprisingly, the CIE coordinates were very close to the NTSC coordinate values. Based on the results, these phosphors could be suitable materials for luminescence-based optoelectronic devices.

Er3+-doped and co-doped (Er3+/Yb3+):polyethylene oxide (PEO)/polyvinylpyrrolidone (PVP) blended polymer composites were synthesized by the traditional solution-casting method. The amorphous nature of the prepared Er3+- and Yb3+-doped polymer composites was confirmed by X-ray diffraction analysis. The interaction between dopant rare earth ions and the blended polymer was systematically elucidated by Fourier transform infrared spectroscopy and Raman spectroscopy analysis. A prominent near-infrared (NIR) emission was observed at 1.53 μm (4I13/2→4I15/2) from the fluorescence spectra of the Er3+:PEO/PVP polymer composites under 980 nm excitation at room temperature. The NIR emission intensity was appreciably increased by increasing the Er3+ ion concentration. The optimized concentration of the Er3+ ions was found to be 0.2 wt%. The emission performance was drastically reduced after the optimized concentration due to the concentration quenching effect. Upon co-doping with Yb3+ to Er3+:PEO/PVP polymer composites, the NIR emission intensity at 1.53 μm (4I13/2→4I15/2) was remarkably improved through energy transfer from Yb3+ to Er3+. The Er3+ NIR fluorescence intensity was increased significantly by increasing the co-doping concentration of Yb3+ in the PEO/PVP polymer composite system. The optimized sensitizing concentration of Yb3+ ions was found to be 0.05 wt% in the PEO/PVP polymer-blended composite system. The energy-transfer phenomenon was elucidated through an energy-level diagram. These co-doped (0.2Er3++0.05Yb3+):PEO/PVP polymer-blended composite materials could be considered as promising candidates for several NIR photonic device applications. This approach of NIR-emitting polymer composites will be useful for various NIR optoelectronic applications.

A series of Ce3+/Eu3+ co-doped biocompatible lithium zinc borate glasses were synthesized via melt quenching. X-ray diffraction, Raman and scanning electron microscopy studies were carried out for synthesized glasses. The photoluminescence spectrum of Ce3+ glass exhibited a broad blue band at 447 nm (5d→4f) with λexc = 350 nm. The optimized content of Eu3+ (1.0 mol%) doped glass exhibited an intense red emission at 612 nm (5D0→7F2) under λexc = 393 nm. The energy transfer is supported by spectral overlap, fluorescence, decay dynamics, and Commission Internationale de l'Elcairage color coordinates. Inokuti–Hirayama model revealed energy transfer from Ce3+ to Eu3+ is dominated by dipole-dipole interaction. The chromaticity coordinates of Eu3+ have been shifted from red to white region by inclusion of Ce3+ ions due to efficient energy transfer from Ce3+ to Eu3+. In vitro Prestoblue assay result confirms non-cytotoxicity with appreciable biocompatibility. Based on these spectral features, Ce3+/Eu3+ co-doped biocompatible lithium zinc borate glasses can be suggested as a promising candidate for white light applications.

We synthesized a batch of co-doped (Ce3++Sm3+): LBZ glass specimens by melt quenching process and their structural and radiation properties were studied by employing XRD, FE-SEM, optical absorption, photoluminescence and lifetime measurements. UV–Vis–NIR absorption studies of the co-doped (Ce3++Sm3+): LBZ glassy matrix displays pertinent bands of both Ce3+ and Sm3+ ions. Individually doped Sm3+: LBZ glass exhibit bright orange emission at 603 nm (4G5/2 → 6H7/2) under the excitation of 403 nm. Nevertheless, the luminescence intensities pertaining to Sm3+ were extraordinarily increased by co-doping with Ce3+ ions to Sm3+: LBZ glassy matrices because of energy transfer from Ce3+ to Sm3+. The fluorescence spectra of co-doped (Ce3++Sm3+): LBZ exhibits characteristic emission bands of Ce3+ (441 nm, blue) and Sm3+ (603 nm, reddish orange) under the excitation of 362 nm. Decay curves of Ce3+ and Sm3+ ions in co-doped glass has been fitted to double exponential nature. The decreasing lifetime of donor ion and rising lifetime of acceptor ion in double doped glass could support the energy transfer from Ce3+ to Sm3+ ions in the host matrix. The CIE coordinates and CCT values were calculated for all the obtained co-doped glassy samples from their luminescence spectra. By adding Ce3+ ions to individually doped Sm3+: LBZ glass matrix, the emitting color changes from reddish orange to white light which resembles the energy transfer from Ce3+ to Sm3+ ions. These studies, perhaps implied that attained co-doped (Ce3++Sm3+): LBZ glassy samples are potential materials for white lighting appliances.

Novel bright red emission was obtained from co-doped Gd3+/Eu3+: CaLa2ZnO5 (CLZO) phosphor spheres. We have successfully synthesized co-doped Gd3+/Eu3+: CLZO phosphor spheres by citrate sol-gel method. Structural and morphological analysis was carried out by XRD and FE-SEM. EDS and XPS studies were employed to analyze the presence of elements and their ionic states respectively. The complex formation studies were carried out by the FTIR spectral study. The photoluminescence spectral profiles confirm the dazzling red emission has been observed at 626 nm (5D0 → 7F2) from the Eu3+: CLZO phosphors under the excitation of 467 nm. Upon increasing the Eu3+ concentration, the photoluminescence performance has also increased remarkably. The optimized concentration of the Eu3+ was noticed at 12 mol%. Upon co-doping with Gd3+ ions to Eu3+: CLZO phosphors, the red emission pertaining to Eu3+ was appreciably enhanced through energy transfer from Gd3+ to Eu3+ ions. The energy transfer mechanism was substantiated by several fluorescent methods such as lifetime decay dynamics and quantum efficiencies. Commission International de I’Echairage (CIE) 1931 chromaticity coordinates (x–y) calculated for singly doped and co-doped CLZO samples. The CIE coordinates were found to be (0.6644, 0.3355) and (0.6688, 0.3311) respectively, which were good consistent with the standard values of NTSC surprisingly. Correlated color temperature (CCT) value was evaluated for optimised co-doped sample and it was found to be between 2000–5000 K which could be more preferable red component for warm white light applications. The lifetime and quantum efficiency of the optimized co-doped sample have been evaluated as 1.102 ms and 69% respectively. The ravishing red emission of the Gd3+/Eu3+: CLZO phosphor spheres which suggests that these phosphor materials could be promising candidates for red luminescent optical devices.

We have successfully synthesized co-doped Bi3+/Eu3+: CLZO nanophosphor spheres by citrate sol-gel method. Tetragonal structure has been confirmed from the XRD analysis. Morphological studies were carried out from FE-SEM analysis for the optimized sample. EDAX and XPS measurements were employed to confirm the presence of elements and their ionic states. The homogeneous shape, size and crystalline planes of the phosphor crystalline nanosphere have been clearly demonstrated by HR-TEM analysis. Photoluminescence (PL) spectral profiles reveal that the strong red emission has been noticed at 626 nm (5D0→7F2) from the Eu3+: CLZO phosphors under the visible excitation of 467 nm. The PL performance has been remarkably enhanced by increasing the Eu3+ ion concentration. By co-doping with Bi3+ ions to Eu3+: CLZO phosphors, the red emission pertaining to Eu3+ was appreciably enhanced through energy transfer from Bi3+ to Eu3+ ions. The energy transfer mechanism from Bi3+ to Eu3+ ions has been demonstrated by partial energy level scheme diagram. Commission International de I'Echairage (CIE) 1931 chromaticity coordinates (x-y) calculated for singly Eu3+(12 mol %): CLZO and co-doped Eu3+(12 mol %)+Bi3+(1 mol %): CLZO nanophosphor spheres and they were found to be (0.6644, 0.3355) and (0.6688, 0.3311) respectively. The Correlated Color Temperature (CCT) value was evaluated as 3059 K for co-doped sample. Moreover, lifetime and quantum efficiency for Eu3+ emission were significantly enhanced upon co-doping with Bi3+ ions to the Eu3+ doped CLZO nanophosphor spheres. The energy transfer phenomenon from Bi3+ to Eu3+ ions was clearly elucidated by several fluorescence dynamics such as overlapped spectral studies, photoluminescence spectral features, CIE color coordinates and quantum efficiency. These dazzling red luminescent nanophosphor spheres material could be suggested as a promising candidate for solid state illumination and optical display devices.

Various concentrations of Er3+ (0.3, 0.5, 1.0 and 1.5 mol %) doped lithium fluoro zinc borate glasses were synthesized by a traditional melt quenching method. XRD, FTIR and FESEM have been employed to analyze the structural, compositional and morphological analysis respectively. Judd–Ofelt theory has been employed to analyze the intensity parameters (Ωλ, λ = 2, 4 and 6) which can be used to estimate the radiative properties of fluorescent levels of Er3+. We have been observed a strong NIR emission peak at 1.53 μm (4I13/2 → 4I15/2) under the excitation of 980 nm from Er3+: LBZ glasses. Nevertheless, the NIR emission is remarkably enhanced by increasing the Er3+ ions concentration until the optimized concentration of 0.5 mol%. The lifetime of the excited level of 4I13/2 in the NIR emission transition is evaluated and it is found to be1.22 ms from the decay analysis of 0.5 mol% Er3+: LBZ glass. Apart from the NIR emission, a bright up-conversion green emission is observed at 544 nm (4S3/2 → 4I15/2) along with an intense red emission at 659 nm (4F9/2 → 4I15/2) and a weak blue emission (2H9/2 → 4I15/2) under the excitation of 980 nm. Up-conversion emission features were significantly enhanced with increasing the Er3+ concentration up to 1.0 mol%. The combination of the obtained up-conversion emission colors of green, red and blue could generate white light emission. The cool white-light emission from the optimized glass sample has been confirmed from the Commission International de I'Echairage (CIE) 1931 chromaticity diagram analysis and their correlated color temperature (CCT) values. Based on the NIR and up-conversion emission features, Er3+: LBZ glasses could be suggested as promising candidates for optical amplifiers, optical telecommunication windows and white light photonic applications.

Lithium zinc borate glasses (LBZ) composed of Li2CO3-LiF-H3BO3-ZnO activated with distinct concentrations (0.1–1.0 mol%) of Tb3+ ions were synthesized and explored their structural and optical characteristics. The functional groups and non-crystalline behavior of glasses were validated from the RAMAN and X-ray diffraction analysis, respectively. The optical bandgap was found to be 3.203 eV for (0.5 mol%) Tb3+ contained glass. The excitation spectrum of the same glass discloses a sharp peak at 376 nm (7F6→5D3). Under 376 nm excitation, luminescence spectra of Tb3+ ions incorporated glasses displayed the prominent emission transitions noticed at 5D4 → 7F6–3 with a strong green luminescence centered at 543 nm (5D4 → 7F5). The optimized concentration of Tb3+ for efficient green color emitting display devices was found to be 0.5 mol%. Lifetime decay analysis was carried out which is well fitted in single exponential function and it was found to be 1.032 ms. CIE color coordinates were estimated for all the procured glasses from their emission spectra and they are reside in the strong green color zone. The obtained green color coordinate values of the optimized glass were closer to the SMPTE and EBU coordinates (0.290, 0.600) for the green illumination appreciably. CCT values of the optimized Tb3+ incorporated glass were lie in the cool green region with high color purity of 82%. From these strong green emission features of the studied glasses, 0.5 mol% Tb3+: LBZ glassy matrix could be suggested as a potential candidate for the application of green laser and display device applications.

Lithium fluoro zinc borate (LBZ) glasses doped with Nd 3 + ions at distinct concentrations (0.3, 0.5, 1 & 1.5 mol%) were prepared using melt quenching technique. Structural, thermal and compositional studies of these glasses were carried out by XRD, TG-DTA and FTIR analysis respectively. The properties of dielectric studies such as dielectric constant and dielectric loss have been studied systematically as a function of frequency. The ionic conductivity of Nd 3 + : LBZ doped glasses have been found to be more than the conductivity of the host LBZ glass and the optimized concentration of 0.5 mol% Nd 3 + : LBZ glass exhibits high ionic conductivity. Photoluminescence proerties of obtained glasses were systematically analyzed. J-O intensity Ω λ (λ = 2, 4, 6) parameters have been evaluated from the absorption spectrum of 0.5 mol% Nd 3 + : LBZ glass and they were used to estimate the parameters such as radiative lifetime (τ R ), transition probability (A), branching ratios (β R ) and spectroscopic quality factor (χ) for the major emission transitions. Predominant NIR emission at 1062 nm ( 4 F 3/2 → 4 I 11/2 ) is observed under the excitation of 741 nm ( 4 I 9/2 → 4 F 7/2 ) along with other two moderately less intense emission peaks at 897 nm ( 4 F 3/2 → 4 I 9/2 ) and 1332 nm ( 4 F 3/2 → 4 I 13/2 ). Experimental lifetime for the level 4 F 3/2 has been compared with radiative lifetime obtained through J-O parameters. The decay lifetimes dynamics and non-radiative transition rate have been systematically evaluated. These Nd 3 + doped glasses could be suggested as promising candidates for 1.06 μm laser applications and solid state battery applications.

A series of co-doped (Yb 3+ /Er 3+ ): Li 2 O-LiF-B 2 O 3 -ZnO glasses were prepared by standard melt quenching technique. Structural and morphological studies were carried out by XRD and FESEM. Phonon energy dynamics have been clearly elucidated by Laser Raman analysis. The pertinent absorption bands were observed in optical absorption spectra of singly doped and co-doped Yb 3+ /Er 3+ : LBZ glasses. We have been observed a strong up-conversion red emission pertaining to Er 3+ ions at 1.0 mol% under the excitation of 980 nm. However, the up-conversion and down conversion (1.53 µm) emission intensities were remarkably enhanced with the addition of Yb 3+ ions to Er 3+ : LBZ glasses due to energy transfer from Yb 3+ to Er 3+ . Up-conversion emission spectra of co-doped (Yb 3+ /Er 3+ ): LBZ glasses exhibits three strong emissions at 480 nm, 541 nm and 610 nm which are assigned with corresponding electronic transitions of 2 H 9/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 respectively. Consequently, the green to red ratio values (G/R) also supports the strong up-conversion emission. The Commission International de E′clairage coordinates and correlated color temperatures (CCT) were calculated from their up-conversion emission spectra of co-doped (Yb 3+ /Er 3+ ): LBZ glasses. The obtained chromaticity coordinates for optimized glass (0.332, 0.337) with CCT value at 5520 K are very close to the standard white colorimetric point in cool white region. These results could be suggested that the obtained co-doped (Yb 3+ /Er 3+ ): LBZ glasses are promising candidates for w-LEDs applications.

A prominent sensitization effect of In 3+ ions is observed in In 3+ +Eu 3+ : PVA polymer composites under UV excitation. Consequently, it enhances the red emission performance of Eu 3+ ions in PVA system. We have successfully synthesized Eu 3+ : PVA, In 3+ : PVA and In 3+ +Eu 3+ : PVA polymer films by traditional solution casting method. The structural and ion-polymer interaction studies have been analyzed from XRD and FTIR spectral profiles. Eu 3+ doped PVA polymer composites are exhibited a red emission at 619 nm ( 5 D 0 → 7 F 2 ) under 396 nm ( 7 F 0 → 5 L 6 ) of excitation. Upon co-doping with In 3+ ions in different concentrations to the Eu 3+ : PVA polymer film, it exhibits predominant red emission than singly doped Eu 3+ : PVA under 396 nm of excitation due to energy migration from In 3+ to Eu 3+ . Successful emission photons of In 3+ ions are collectively absorbed by the Eu 3+ ions which lead the improvement of red emission. Optimized sensitization concentration of the In 3+ ions has been found to be 0.01 wt%. Possible energy migration phenomenon is elucidated by several fluorescent dynamics. The energy transfer process is substantiated by lifetime decay analysis and overlapped spectral studies. The Commission International de I-Eclairage chromaticity coordinates were calculated. The quantum efficiencies of the Eu 3+ ions and In 3+ ions in singly doped and co-doped polymer systems have been evaluated. From these results, these co-doped In 3+ +Eu 3+ : PVA composite polymer films might be proposed as encouraging candidates for bright red fluorescent materials for several photonic applications.

A bright novel sensitized red emission has been obtained from functionalized multiwalled carbon nanotubes (f-MWCNTs) embedded Bi 3+ +Eu 3+ : PVA polymer nanocomposites under UV excitation. We have successfully synthesized Eu 3+ : PVA, Bi 3+ +Eu 3+ : PVA and Bi 3+ +Eu 3+ + functionalized MWCNTs: PVA polymer films by traditional solution casting method. The structural and ion-polymer interaction studies have been analysed from XRD and FTIR spectral profiles. Eu 3+ doped at different concentrations in PVA polymer films has displayed a red emission at 619 nm ( 5 D 0 → 7 F 2 ) under 396 nm ( 7 F 0 → 5 L 6 ) of excitation. Upon co-doping with Bi 3+ ions in different concentrations to the Eu 3+ : PVA polymer film, it exhibits enriched red emission than single Eu 3+ : PVA under the same excitation due to energy migration from Bi 3+ to Eu 3+ . Successful emission photons of Bi 3+ ions are collectively absorbed by the Eu 3+ ions which lead the improvement of red emission. In the same fashion, enriched red emission is observed from f-MWCNTs impregnated co-doped Bi 3+ +Eu 3+ : PVA polymer composites. The red emission of Eu 3+ is significantly enhanced in two ways through an efficient energy migration process from Bi 3+ to Eu 3+ and f-MWCNTs to Eu 3+ . Possible energy transfer mechanism is clearly demonstrated by several fluorescent methods. From these results, these f-MWCNTs embedded Bi 3+ +Eu 3+ : PVA polymer films might be recommended as promising candidates for red luminescent materials for photonic devices.

Red emission was obtained from rare earth doped polymer nanocomposites, namely, composites of polyvinyl-alcohol (PVA) co-doped with Gd 3+ and Eu 3+ and embedded with TiO 2 nanoparticles (TiO 2 NP), under ultraviolet (UV) excitation. We successfully synthesized Eu 3+ : PVA, Gd 3+ : PVA, (Gd 3+ + Eu 3+ ): PVA, and (Gd 3+ + Eu 3+ + TiO 2 NP): PVA films by solution casting method. From X-ray diffraction patterns and Fourier-transform infrared spectral profiles, the structural details of the films and the ion–polymer interaction mechanism responsible for their formation were systematically analyzed. The thermal stability and decomposition dynamics of the prepared samples were evaluated by thermogravimetry and differential thermal analysis. Pertinent optical absorption bands related to Eu 3+ and Gd 3+ ions in the polymer composites were observed and assigned to the corresponding electronic transitions. The PVA film containing different concentrations of the Eu 3+ dopant displayed red emission at 618 nm ( 5 D 0 → 7 F 2 ) under UV excitation at 396 nm ( 7 F 0 → 5 L 6 ). Upon co-doping with Gd 3+ to form the (Gd 3+ + Eu 3+ ): PVA film, it exhibited red emission that was stronger than that from the singly doped Eu 3+ : PVA film under 270 nm excitation because of the energy transfer from Gd 3+ to Eu 3+ ions. After the TiO 2 nanoparticles were evenly dispersed in the co-doped (Gd 3+ + Eu 3+ ): PVA films, the photoluminescence properties were remarkably enhanced and prominent red emission was observed under 274 nm excitation. The red emission of Eu 3+ was significantly enhanced through an efficient energy-transfer process from the Gd 3+ ions to Eu 3+ ions and from the TiO 2 nanoparticles to Eu 3+ ions. A possible energy-transfer mechanism was clearly demonstrated by several fluorescent methods and lifetime decay dynamics. Based on the above results, these polymer composite films are promising candidates for red luminescent photonic devices.

Lithium borate glasses activated with specific concentrations of Ce3+ ions have been processed by melt quenching technique. X-ray diffraction and SEM with EDAX carried out structural and surface morphology with elemental confirmation respectively. The nebulous nature of glassy matrices have been affirmatively confirmed by XRD and it was corroborated with SEM analysis. A distinguished absorption band is noticed in the ultraviolet region and the photoluminescence spectra displays a broad and intense blue emission band in the region from 395 nm to 570 nm which is centered at 447 nm (5d→4f) by exciting with 350 nm in Ce3+: LBZ glassy matrices. The dazzling blue emission intensity was significantly ameliorated by improving the addition of Ce3+ ion concentration in the glass matrix. The blue emission intensity has been found to be decreased at higher concentrations due to concentration quenching and the optimal concentration of Ce3+ ions is estimated to be 0.5 mol%. The fluorescence decay time has been evaluated as 0.86 ms from the decay profile of 0.5 mol% Ce3+: LBZ glass. Chromaticity coordinates were determined from the luminescence spectra, which are found to be falls in the bright blue region. The obtained blue emission CIE coordinates are close to standard EBU and NTSC coordinates for blue illumination. In view of these spectral features, 0.5 mol% Ce3+: LBZ glass could be recommended as promising candidate for the applications of blue emissive photonic devices.

The present paper brings out the results concerning the preparation and optical properties of Sm 3+ and Dy 3+ each ion separately in different concentrations (0.3, 0.5, 1.0 and 1.5 mol.%) and also together doped (x mol.% Dy 3+ + 1.5 mol.% Sm 3+ ): Li 2 O-LiF-B 2 O 3 -ZnO (where x = 0.5, 1.0 and 1.5 mol.%) glasses by a melt quenching method. Structural and thermal properties have been extensively studied for those glasses by XRD and TG/DTA. The compositional analysis has been carried out from FTIR spectral profile. Optical absorption spectral studies were also carried out. Sm 3+ : LBZ glasses have displayed an intense orange emission at 603 nm ( 4 G 5/2 → 6 H 7/2 ) with an excitation wavelength at 403 nm and Dy 3+ : LBZ glasses have shown two emissions located at 485 nm ( 4 F 9/2 → 6 H 15/2 ; blue ) and 574 nm ( 4 F 9/2 → 6 H 13/2 ; yellow ) with an excitation wavelength at 385 nm. Remarkably, it has been identified that the significant increase in the reddish orange emission of Sm 3+ ions and diminished yellow emission pertaining to Dy 3+ ions in the co-doped LBZ glass system under the excitation of 385 nm which relates to Dy 3+ ions. This could be due energy transfer from Dy 3+ to Sm 3+ . The non-radiative energy transfer from Dy 3+ to Sm 3+ is explained in terms of their emission spectra, donor lifetime, energy level diagram and energy transfer characteristic factors. These significantly enhanced orange emission exhibited glasses could be suggested as potential optical glasses for orange luminescence photonic devices.

An intense red emission from Eu3+: La10W22O81 (LWO) microphosphor rods has been obtained under UV excitation source for latent fingerprint (LFP) imaging. Microphosphor rods of LWO doped with various concentrations of Eu3+ ions were synthesized using a hydrothermal assisted solid-state method. XRD revealed that the microphosphors had an orthorhombic structure with the space group of Pbcn (60). FE-SEM showed that the surface morphology of the optimized Eu3+ (14 mol %): LWO microphosphors were hexagonal rods with pencil-like tips at both ends. TEM evaluation with elemental mapping and XPS analysis confirmed the occurrence of the vital elements in the microrods. FTIR spectral analysis was performed for the analysis of the spectral bands. An intense red emission was obtained from the Eu3+ doped LWO microphosphors under the excitation of 394 nm (7F0→5L6) which could be attributed to the hypersensitive transition of 5D0→7F2 pertaining to the Eu3+ ions. Enhancement of the emission was noticed from the microphosphors when the Eu3+ content was increased. Optimal red emission was obtained with the Eu3+ (14 mol %): LWO microphosphor. The photoluminescence intensity was found to be reduced after optimized concentration due to concentration quenching. The quadrupole–quadrupole interaction is found to be responsible for concentration quenching. The luminescent properties were systematically demonstrated using an energy level scheme diagram. The luminescence lifetime was evaluated for all the concentrations of Eu3+ doped LWO samples. The lifetime decay dynamics has also been clearly elucidated. CIE color coordinates were also evaluated from the luminescence spectra of the microphosphors and they are found to be located in strong red region. A significant luminescence quantum yield was determined for the Eu3+ (14 mol %): LWO microphosphor. The optimized microphosphor was used in detecting LFPs, employing the powder dusting method commonly used in forensic science. We detected the LFP ridge patterns with high sensitivity, reliability, and selectivity by using the optimized microphosphor. Its non-cytotoxic nature was also evaluated using WI-38 cell lines. Results demonstrated that the Eu3+ (14 mol %): LWO microphosphor could be a promising candidate for luminescent applications and LFP applications in forensic investigation preferably.

Eu3+:PEO + PVP, Sm3+:PEO + PVP and co-doped Sm3+ + Eu3+:PEO + PVP polymer films have successfully been synthesized by solution casting method. For these polymer films, their XRD, FTIR and RAMAN spectral profiles were studied systematically. Both absorption and photoluminescence spectra have been assessed by evaluating their optical properties. The Sm3+:PEO + PVP and Eu3+:PEO + PVP polymer film has displayed a reddish-orange and red emissions at 596 nm and 619 nm respectively under an UV lamp. A reddish-orange emission was found for Sm3+:PEO + PVP polymer film at 596 nm (4G5/2 → 6H7/2) and its lifetime has also been evaluated suitably. Red emission at 619 nm (4G5/2 → 6H7/2) of Eu3+ has been identified for Eu3+:PEO + PVP polymer film and its lifetime are also evaluated. The photoluminescence efficiency of Eu3+ ion has been enhanced due to the addition of Sm3+ by means of an energy transfer process. The energy transfer mechanism, from Sm3+ to Eu3+ has been clearly established. At 0.1 wt% concentration of Sm3+ ions (sensitizer), the photoluminescence efficiency of the Eu3+ ion (activator) has been significantly enhanced in co-doped sample through energy transfer from Sm3+ to Eu3+ in the polymer matrix. The energy transfer process has been analyzed using lifetime decay dynamics. From the obtained results, these polymer materials could be proposed as potential Red luminescent optical materials.

A series of distinct concentrations of Eu3+ doped lithium borate glassy matrices were prepared by melt quenching technique and their structural and luminescence characteristics have been studied. A wide hump exhibited in X-ray diffraction spectrum and smooth surface from SEM analysis affirms the nebulous behavior of the obtained glassy matrices. A strong excitation band noticed at 393 nm (7F0→5L6) correlated with the excitation wavelength of near-UV LED chip. By exciting with 393 nm, photoluminescence spectra reveals a strong red emission at 612 nm (5D0→7F2). Luminescence intensity has been embellished remarkably with rising Eu3+ concentration up to 1.0 mol % which can be identified as optimized concentration. At higher concentrations of Eu3+, emission intensity has been decreased due to concentration quenching. The excited level 5D0 lifetime is computed and it is evaluated to be 2.57 ms from the decay profile of 1.0 mol % Eu3+: LBZ glassy matrix. CIE color coordinates have been calculated from the luminescence spectra, which indicates strong red emission. Based on the luminescence spectral features, 1.0 mol % Eu3+: LBZ glassy matrices could be suggested as favorable candidates for the application of reddish orange emission photonic devices.

Gadolinium oxide nanobars were obtained by thermal decomposition of gadolinium oxalate, which was synthesized by the chemical precipitation method along with glycerol. The functional group analysis and formation of gadolinium oxide from gadolinium oxalate were characterized by the Fourier transform infrared spectroscopy and thermo gravimetric analyzer. The crystal structure, average crystallite size, and lattice parameter were analyzed by X-ray diffraction technique. Moreover, Raman shifts, elemental composition and morphology of the gadolinium oxide was widely investigated by the laser Raman microscope, X-ray photoelectron spectroscopy, FE-SEM-EDAX and HR-TEM, respectively. Furthermore, the optical properties like band gap, absorbance measurement of the gadolinium oxide were extensively examined. In addition, the paramagnetic property of gadolinium oxide nanobars was explored by the vibrating sample magnetometer.

Bioclimatic concepts in vernacular architecture was developed and used through the centuries by many civilizations across the world. This study is carried out on the vernacular architecture of coastal regions. The vernacular architecture in the coastal belts of Nagapatinam is known for its use of natural and passive methods so as to create a comfortable indoor environment. However, so far, it has not been proved by a detailed quantitative evaluation method. The authors have conducted the qualitative and quantitative analysis to investigate the indoor environmental condition of a vernacular residential building in coastal region of Nagapatinam. The quantitative analysis has been done by continuously monitoring the indoor and outdoor thermal and environmental conditions using a custom made instrument called “Mini metrological Station known as Architectural Evaluation System”. The results of this study research shows that the solar passive techniques used in these vernacular residential buildings in coastal region provides comfortable thermal indoor environment irrespective of the outdoor climatic conditions.