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AbstractWith an insight into the efficacy of various impurity-doping upon the luminescence properties, experiments were initiated to manipulate the structural amenities of pyrochlore-derived cesium based complex (Cs2K/NaAl3F12) fluorides. Difficulty in producing expected results in lab-synthesized fluorides is not new to the researchers. Though fluorides with more than one cation appears complicated, triumph in synthesis of Cs2KAl3F12 and Cs2NaAl3F12 complexes have been achieved via simple precipitation method. Photo-luminescence (PL) results showed that all attempted rare-earth ions got successfully incorporated into the crystal lattices during synthesis process itself. Consequences of dopant concentration on PL intensity for all impurity-ions have been summarized along with their calculated CIE parameters such as Correlated Color Temperature (CCT) and Color purity, particularly for the activators exhibiting emissions in the visible range. However, Ce, Tb and Dy showed as usual characteristic emissions, two phosphors Cs2KAl3F12:Eu3+ (1%) and Cs2NaAl3F12:Eu3+ (1%) acquire exceptional color purity. CCT for most of the phosphors proposed in the present study reflects promising applications in the household LED lighting. Radius percentage discrepancy (Dr) values were found helpful in understanding the underlying prospects of ionic replacement of cationic sites within the lattice structures by the various substituting impurity-ions. Additional studies related to phase purity, morphology and elemental analysis of the compounds were also included, by means of different x-ray diffraction (XRD), Scanning Electron Microscopic (SEM) and Energy-dispersive X-ray spectroscopy (EDAX) techniques. [ABSTRACT FROM AUTHOR]

Ba3Ca2(PO4)3F, having been proven beneficial for ancient geological surveys, was also found to be an efficient fluorescence emitter when doped with various rare-earth and transition ions. Advancing the respective properties further, dysprosium (Dy3+) was added as an activator into the Ba3Ca2(PO4)3F host lattice. The Dy ion in its trivalent form possesses emission in two regions, blue at 481 nm and green at 575 nm, opening a new window towards its plausible use in white-light-emitting diode (LED) lighting appliances. Subsequent analyses including x-ray diffraction, Rietveld refinement, photoluminescence, and lifetime observed in milliseconds (ms) revealed a similar nature of the decay curves as given in the literature. Further, a CIE coordinate calculation predicted near-ideal white light emission. [ABSTRACT FROM AUTHOR]

Calcium molybdate (CaMoO 4) and Dy3+ doped CaMoO 4 (Dy3+ = 0.5, 1, 1.5, 2 and 2.5 at.%) nanoparticles were successfully obtained by mechanochemical approach. The influence of Dy3+ ion concentration on the structure, morphology, and photoluminescent properties were investigated. The CaMoO 4 and Dy3+ doped CaMoO 4 phases with tetragonal structure were completely prepared after 30 min milling time with applied milling speed of 850 rpm. TEM analysis shows that the synthesized samples consist of mainly spherical particles with narrow particle size distribution. According to both XRD and TEM analysis, the average particles size is below 40 nm. The UV–vis absorption spectra show one peak at 240–245 nm. The calculated optical band gap of pure CaMoO 4 is 3.96 eV and it decreases to 3.65 eV with increasing the concentration of Dy3+ ion up to 2.5 at %. The excitation spectra of the Dy3+-doped CaMoO 4 samples contain absorption peaks corresponding to the MoO 4 group and to the Dy3+ ion. The green and blue light emissions were observed for pure CaMoO 4 and Dy3+ doped CaMoO 4 samples under different wavelengths excitation (250 and 350 nm) typical for absorption of the host matrix. Emission spectra of all doped powders consist of the characteristic peaks of Dy3+ in the blue (∼480 nm) and yellow (∼575 nm) regions which are assigned to the 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 transitions, respectively. The weak peak at 660 nm also is observed due to 4F 9/2 → 6H 11/2 transition of Dy3+ ion. The highest photoluminescence emission intensity was detected when the sample is doped with 1.5 at.% Dy3+ concentration. It was found that the color coordinates (x and y) of 1.5 at.% and 2 at.% Dy3+-doped CaMoO 4 fall close to the white light region in the CIE diagram. The results indicate that the mechanochemically obtained Dy3+ doped CaMoO 4 nanoparticles can find application in different optical instruments. [ABSTRACT FROM AUTHOR]

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet–visible (UV–Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of Eu3+-doped Er2SiO5 phosphor are reported. The samples are prepared using the modified conventional solid-state synthesis technique with variable concentrations of doping ions and their structural studies are carried out by X–ray diffraction (XRD). The information on the morphology of the samples prepared with optimized doping ion concentrations is obtained by scanning electron microscopy (SEM). A photoluminescence (PL) analysis of the phosphor samples is also done for the fixed doping ion concentrations. The identified PL emission bands are attributed to the intra 4f transitions of a Eu3+ ion, such as 5D0→7F1 at 590 nm, 5D0→7F0 at 602 and 5D0→7F2 at 613 nm. The corresponding transitions of the doping ions and the concentration quenching effect are studied in detail. The 1931 Commission Internationale de l'éclairage (CIE) (x, y) chromaticity coordinates show the spectral distribution calculated from the PL emission spectrum. A thermoluminescence (TL) glow curve analysis is performed for variable doping ion concentrations, and the corresponding trap parameters are calculated using the Computerized Glow Curve Deconvolution (CGCD) technique. Our study shows that as-prepared phosphor may be useful for display devices. [ABSTRACT FROM AUTHOR]

The present investigation describes the synthesis of luminescent terbium‐doped strontium aluminate nanoparticles emitting bright green light, which were synthesized through a solid‐state reaction method assisted by microwave radiation. Various samples containing different concentrations of Tb were synthesized, and an analysis of their structural and morphological features was conducted using powder x‐ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The band gaps of the samples were determined utilizing the Kubelka–Munk method. The quenching mechanism observed was identified to be due to dipole–dipole interaction using the Dexter theory. The optimized sample with a terbium concentration of 4 at.% has a luminescence lifetime of 1.05 ms with 20.62% quantum efficiency. The results of this study indicate that the terbium‐doped strontium aluminate fluorescent nanoparticles exhibit promising potential for a wide range of applications, including bioimaging, sensing and solid‐state lighting. [ABSTRACT FROM AUTHOR]

This manuscript presents research on the optoelectronic and energy transfer properties of conjugated polymer poly (N,N′-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (poly-TPD) and laser dye Fluorol 7GA (F7GA) hybrid thin films prepared via solution blending technique. Various weight ratios of F7GA were added to a fixed concentration of poly-TPD to form homogeneous hybrids. The hybrid thin films were characterized using absorption and photoluminescence spectroscopy. The results showed enhanced absorption, widened optical bandgaps, slight blue-shifted emission, and decreased refractive index in the hybrid films compared to pristine poly-TPD. The significant spectral overlap between the emission spectrum of poly-TPD and the absorption spectrum of F7GA, allowing for efficient Förster resonance energy transfer. Parameters including efficiency, distance, lifetime, and probability of energy transfer were calculated to quantitatively analyze energy transfer. Modulation of F7GA content led to tunable emission colors across the visible spectrum. Overall, the successful energy transfer demonstrated in this study paves the way for exciting future directions in the field of poly-TPD/F7GA hybrid materials for advanced optoelectronic applications. [ABSTRACT FROM AUTHOR]

A series of Er3+ ions doped Sr9Y2W4O24 (SYW) phosphors have been synthesised using solid‐state reaction technique. For optical thermometry and solid state lighting applications, the crystal structure, morphological, and luminescence features of the SYW : Er3+ phosphors were explored. X‐ray diffraction (XRD) reveal that synthesized phosphors having single phase with a tetragonal crystal structure and I41/a space group. Scanning electron microscopy (SEM) was used to examine the morphological behaviour and presence of composition elements. The optical bandgap of the phosphor was evaluated using UV‐Vis diffuse reflection spectra (DRS). The photoluminescence (PL) emission spectra were captured under 380 nm excitation, and the peak with the maximum intensity was identified at 563 nm ascribed to transition 4S3/2→4I15/2, that emits green color in visible region. The temperature dependent PL (TD‐PL) spectra show that SYW phosphor is substantially more thermally stable, having thermal activation energy of about 0.247 eV. Additionally, the fluorescence intensity ratio (FIR) was used to study the optical sensing characteristics of the thermal quenching transitions (2H11/2, 4S3/2) with maximum relative sensitivity (SR) and an absolute sensitivity (SA) being 1.33 % K−1and 0.307 % K−1, respectively. All of the aforementioned findings demonstrate that SYW : Er3+ ions doped phosphors have potential for optical thermometry and other photonic devices. [ABSTRACT FROM AUTHOR]

Y2Sr3B4O12 phosphors doped with europium ions were synthesized by a modified conventional solid-state reaction method. Characterizations of the prepared samples, viz., X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and Commission Internationale de I'Eclairage were studied. The XRD analysis confirmed the formation of mixed phase due to polyborate and has a hexagonal crystalline yttrium orthoborate phosphor. SEM images showed the irregular morphology of the sample. The grain size distribution was broad and the average size was found to range from 2 μm to 100 nm. PL measurements showed excitation and emission characteristics of the prepared phosphor with different concentrations of the doping ion. From the emission spectra, it was clearly observed that the emission intensity of the magnetic dipole was higher than that of electric dipole transition owing to the Eu3+ ions occupying a higher symmetry site in the Y2Sr3B4O12 host. The intensity of PL increased with increasing concentration of the doping ion up to 2.0 mol.%; after that, the PL intensity decreased owing to the concentration-quenching phenomenon. The results indicated that Y2Sr3B4O12:Eu3+ phosphors can be selected as a potential candidate for solar cell/photovoltaic application. [ABSTRACT FROM AUTHOR]

Structural, optical and photoluminescent properties of La2−xPrx(MoO4)3 phosphors with different doping concentrations of Pr3+, synthesized by conventional solid-state and solution combustion routes were studied. X-ray diffraction studies of compounds synthesized through conventional solid-state ceramic route confirm that all samples crystallized in monoclinic La2(MoO4)3 structure with c2/c space group, while combustion synthesized compounds show the existence of two different crystal environments. Analysis of UV–visible diffuse reflectance spectra (DRS) shows characteristics of absorption bands in blue and red regions for Pr3+ substituted La2(MoO4)3 samples, synthesized by both methods. The calculated band gap from the DR spectrum showed an inverse dependence with Pr3+ doping concentration for solid-state synthesized La2−xPrx(MoO4)3 samples, while for combustion synthesized La2−xPrx(MoO4)3 compounds the variation of band gap with concentration is not monotonous. The photoluminescence emission spectrum of blue excited La2−xPrx(MoO4)3 phosphors synthesized by both routes showed similar multicoloured emission bands. Maximum emission intensity was observed for Pr3+ concentration of x = 0.05 in both synthesis methods. The exchange interaction between nearest activator ions leads to concentration quenching of luminescence for solid-state synthesized La2−xPrx(MoO4)3 compounds and dipole–dipole interaction for combustion synthesized La2−xPrx(MoO4)3 compounds. The average emission colour of the blue excited La2−xPrx(MoO4)3 phosphors lies in the yellow–orange region. The CCT values lie in the warm light region and the luminescence lifetime of 8 µs for red emission peak showed promising applications requiring fast switching response. [ABSTRACT FROM AUTHOR]

Current study is aimed at evaluating Eu-doped barium-bismuth phosphate glasses as potential visible laser medium operating in red spectral region. Samples with composition x Eu 2 O 3 –20BaO–20Bi 2 O 3 -1.5Al 2 O 3 -(58.5- x)P 2 O 5 (x = 0, 0.5, 1.0, 1.5) were prepared using melt-quenching technique. Physical parameters, such as, density, molar volume, oxygen packing density, rare-earth ion concentration, inter-nuclear distance and field strength were evaluated. Thermal stability of prepared glass samples was observed using Thermogravimetric Analysis (TG). The influence of rare-earth oxide content on glass transition temperature T g , crystallization temperature T c and onset of crystallization temperature T x was studied through Differential Thermal Analysis (DTA). Optical band gap and related optical properties were evaluated from absorption spectrum recorded in the range 225–1000 nm. Judd-Ofelt parameters, branching ratio, radiative lifetime, emission cross-section and other radiative properties were evaluated from photoluminescence emission spectrum in the range 500–750 nm. High value of emission cross-section observed for transition 5D 0 →7F 4 in 0.5-EuBiPBa sample signifies its potential use in the development of visible lasers. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate the photoluminescence properties of Dy3+-activated YNbO4, LuNbO4, and mixed YxLu1−xNbO4:Dy3+ (x = 0.25, 0.5, 0.75) phosphors. For this purpose, five samples with a fixed Dy3+ concentration (2 mol%) were prepared by the solid-state reaction method. X-ray diffraction measurements showed that all phosphors crystallize in a monoclinic fergusonite-beta-(Y) structure with a C2/c space group. Scanning electron microscopy clearly shows that samples are composed of dense, well-developed micron-sized, cube-shaped grains with rounded edges. The photoluminescent emission spectra feature Dy3+ peaks at standard positions corresponding to transitions from the 4F9/2 excited emitting level to the 6HJ (J = 15/2; 13/2; 11/2 and 9/2) lower levels with two dominant emission bands placed in the blue (~ 479 nm, B) and yellow (~ 576 nm, Y) spectral region. It is observed that with Lu increase in the host lattice Y/B ratio decreases toward the desired ratio of unity to obtain white light. To evaluate the suitability of these phosphors for use in solid-state lighting, their photoluminescence emission was analyzed in detail by calculating CIE coordinates, correlated color temperature (CCT) and Delta u,v (DUV). It is shown that CIE chromaticity coordinates of all Dy3+-activated YxLu1−xNbO4 samples (x = 0, 0.25, 0.5, 0.75, and 1) fall into the white portion of the diagram and that with the increase of Lu in the host lattice color becomes whiter. CCT values for all samples are in the cooler 4000–4500 K range with positive DUVs indicating that color points are placed above the black body curve. The average lifetime of 4F9/2 level is calculated to be ~ 0.2 ms for all Dy3+-activated YxLu1−xNbO4 samples, indicating that there is no influence of the Y-to-Lu ratio in the host niobate material on the luminescence kinetics. [ABSTRACT FROM AUTHOR]

We discuss new features of Sm3+-doped LaCePO4 phosphor as a potential candidate for display applications. Mainly, the traditional modified solid-state synthesis technique was used to prepare the samples. The X-ray diffraction technique was used for the structural studies. LaCePO4:Sm3+ phosphor production was verified by Fourier transform infrared studies. It was customary to use scanning electron microscopy to learn more about the morphology of the prepared samples. Additionally, photoluminescence (PL) analysis of the phosphor samples was presented for different doping ion concentrations with various excitations. In the presence of Sm3+, LaCePO4 emits powerful blue and orange emissions. In-depth research was carried out on the transitions between the concentration quenching effect and the doping ion. The distribution of the spectral region estimated from PL emission spectra was shown in the 1931 Commission International de l'Éclairage (x, y) chromaticity coordinates and was located (0.20, 0.22) in the blue region. According to our research, as-prepared phosphor may find useful application in display devices, especially because of its blue and orange content. [ABSTRACT FROM AUTHOR]

The study examines the optical and electrical characteristics of n-ZnO:Al (AZO) thin films that were deposited on p-Si using the sol-gel dip-coating process, with thicknesses ranging from three to six cycles. The I-V characteristics of the diode device exhibited a high and low current under forward and reverse bias, respectively. The ideality factors were found to decrease from 2.78 to 2.13 with an increase in the number of layers from 3C to 6C. However, it was revealed that the barrier height increased from 0.72 to 0.79 eV. Similarly, the rectification ratio increased from 3196 at ±4 V to 5253 at ±4 V with an increase in the thickness of the emitter layer. Some diode parameters were calculated according to the thermionic and Chueng models and found to be in a range comparable to the literature. The optical study based on photoluminescence under UV excitation showed typical emission spectra of n-AZO/-Si heterostructure characterized by a high emission band around 389 nm, which is due to the recombination of excitons (e-=h+). The various intrinsic defects present in ZnO-doped Al thin films are attributed to the broad emission band in the visible range. The chromaticity study with color properties indicated that the correlated color temperature value of the sample 3C (1380 K) falls in the warm white light region. However, the correlated color temperature value of sample 6C (4454 K) is located in the cool white light source region, which is more suitable as an LED lighting source. It was found that by increasing the emitter layer thickness, the correlated color temperature value of the 6C sample is getting closer to 6504 K - the Commission Internationale de l'Eclairage (CIE) standard for daylight (D65). However, unlike the Duv value of the 6C sample (0.011), the one of the 3C sample (0.0032) is located within the acceptable shift range (±0:006). Based on this study, these heterostructures might be an appealing option for manufacturing W-LEDs with n-UV/blue LED chips as the excitation source for use in displays and lighting. [ABSTRACT FROM AUTHOR]

Different concentrations of Sm2O3‐doped lead borosilicate glass were synthesized using a melt–quenching method and their characteristics were analyzed using X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy absorption, emission, and decay curves. From the XRD patterns, the noncrystalline nature of titled glass was confirmed. The structural groups that existed in the host glass were observed from FTIR spectra. The Judd–Ofelt (JO) intensity parameters and oscillator strengths were derived from the absorption spectra and compared with various reported systems. The excitation luminescence levels of the Sm3+ ion radiative properties were further computed using the JO intensity parameters. Effective bandwidth, emission cross‐sections (σe), and several lasing properties were assessed from emission spectra and compared with other reported glass systems. The decay curves of the 4G5/2 level of Sm3+ ion were also been measured and examined. Additionally, the colour coordinates of the Commission International de I'Éclairage chromaticity were assessed. The titled glass were suitable for visible reddish orange luminescence devices based on all obtained parameters. [ABSTRACT FROM AUTHOR]

• Dy3+/Eu3+ dual doped tungstate-tellurite (TWKZBiDyEu) glasses synthesized. • Emitting colour tuned from white to orange-red with activator ion concentration. • Energy transfer from Dy3+ to Eu3+ ions confirmed via theoretical models. • TWKZBiDyEu glasses show good thermal stability with high activation energy. • In view of the above, glasses can be useful for w-LEDs and other photonic devices. In this study, dual ions (Dy3+/Eu3+) doped tungstate-tellurite (TWKZBi: Dy3+/Eu3+) glass matrices have been formed with the help of the melt quenching approach. The structural, thermal, morphological, and photoluminescent (PL) characteristics, as well as the energy transfer (ET) processes were thoroughly investigated. The structural features of the titled glasses have been explored via X-ray diffraction (XRD) analysis. The morphology and elemental studies of the titled glass matrices were verified with the help of field emission scanning electron microscopy (FE-SEM) along with energy dispersive spectroscopy (EDS). The PL results designate that the TWKZBi doped with Dy3+ ions glass samples exhibit a strong emission peak at 575 nm when excited via n-UV light, whereas Eu3+ doped TWKZBi glass sample demonstrates a conspicuous red emission band at 614 nm when stimulated with the n-UV light. In addition, TWKZBi glasses doped with both Dy3+ and Eu3+ ions demonstrate the emission peaks in the blue (B), yellow (Y) and red (R) zones of the electromagnetic spectrum. The combination of these peaks generates white and orange-red light through properly controlling the activator ion concentrations and selected excitations. Based on Dexter's and Reisfeld's approximation, dipole-dipole (d-d) interaction is responsible for the transfer of energy from donor (Dy3+) to accepter (Eu3+) ions. The decay profiles demonstrate the bi-exponential behaviour with a decline in the average lifetime (τ a v g) values as varying activator (Eu3+) ion concentrations in the titled TWKZBi: Dy3+/Eu3+ glasses. All the results above validate that the titled TWKZBi: Dy3+/Eu3+ glass samples could be fascinating for white LEDs and other optoelectronic applications. [ABSTRACT FROM AUTHOR]

(a). The emission of the 40 NTU sample in a water environment at different temperatures under 980 nm excitation. (b). Photomicrographs of the luminescence of 1 %Ho3+, 5 %Tm3+, 1 %Yb3+:Bi 2 WO 6 phosphor excited at 980 nm in a natural light/dark environment and luminescent color change of 323–573 K phosphors. (c). Experimental operation diagram of ambient and thermochromic discoloration and the luminescence photos of 1 %Ho3+, 5 %Tm3+, and 1 %Yb3+ doped Bi₂WO₆ fluorescent powder excited by 980 nm laser demonstrate the color changes of its luminescence in liquid environment and after drying process. [Display omitted] • Ho3+/Tm3+ energy level pairs with larger intervals were constructed to achieve higher fluorescence temperature sensitivity. • The luminescence and temperature sensing properties of Ho3+/Tm3+/Yb3+:Bi 2 WO 6 powders in a water environment were studied. • The synthesized sample displays different luminescent colors in air and water, which has potential applications in anti-counterfeiting. A series of x%Ho3+, 5 %Tm3+, y%Yb3+:Bi 2 WO 6 (x = 0, 0.5, 1, 3, 5; y = 0.5, 1, 3) luminescent materials was prepared using a high-temperature solid-phase method. The microstructure, up-conversion luminescence, and temperature sensing properties of the synthesized powders were analyzed. X-ray diffraction patterns revealed that doping with Ho3+, Tm3+, and Yb3+ ions at certain concentrations did not affect the orthorhombic crystal structure of the Bi 2 WO 6 host. Scanning electron microscopy revealed that the morphology of the sample consisted of lumpy particles with a particle size range of 1–5 µm and agglomeration. SEM mapping and energy-dispersive X-ray spectroscopy analyses revealed that each element was relatively uniformly distributed on the particle surface. Under 980 nm excitation (380 mW), the strongest luminescence of the sample was obtained when both Ho3+ and Yb3+ doping concentrations were 1 %. Compared with the luminescence of the 5 %Tm3+ and 1 %Yb3+:Bi 2 WO 6 sample, with increasing Ho3+ concentrations, the luminescence intensity of Tm3+ was first enhanced and subsequently weakened, whereas the luminescence of Ho3+ was significantly weakened, which indicates the positive energy transfer from Ho3+ → Tm3+. At 980 nm (80–380 mW), for the 1 %Ho3+, 5 %Tm3+, and 1 %Yb3+:Bi 2 WO 6 sample, the 538 nm, 545 nm, 660 nm, and 804 nm emission peaks originated from the two-photon absorption. FIR 660 nm/804 nm , FIR 545 nm/804 nm , and FIR 538 nm/804 nm were used to characterize the temperature and corresponded to temperature sensitivities S r of 0.0046 K−1, 0.022 K−1 and 0.024 K−1 at 573 K, respectively. At 498 K, the minimum temperature resolution δT values were 0.03384 K, 0.03203 K and 0.04373 K. When the temperature increased from 298 K to 573 K, the powder sample luminescence gradually shifted from the yellow-green region to the red region. The results of environmental discoloration and thermochromic performance tests indicate that this sample has potential application in optical anti-counterfeiting. FIR 804 nm /660 nm and FIR 804 nm /538 nm were obtained for the 40 NTU turbidity suspension under identical excitation conditions. At 298 K, for the 40 NTU turbidity sample, the maximum S r values were 0.0197 K−1 and 0.0405 K−1; at 340 K, the minimum temperature resolutions δT values were 0.54037 K and 0.66237 K. When the temperature decreased from 340 K to 298 K, the luminescence of the 40 NTU suspension samples gradually shifted from the yellow region to the green region. [ABSTRACT FROM AUTHOR]

We prepare glasses with a chemical composition of 10NaO2-10SrO2-10Gd2O3-69P2O5-1Dy2O3 (NSrODy) and 10NaF-10SrO2-10GdF3-69P2O5-1Dy2O3 (NSrFDy) melt-quenching method and study the effect of Gd2O3 and GdF3 compounds on their physical and luminescence properties. We observed higher emission spectra intensity of NSrFDy glass than that of NSrODy glass. The difference in the intensity is attributed to the difference in OH concentrations in each samples and the efficient energy transfer from Gd3+ ions to Dy3+ ions in the case of NSrFDy glass. We also find that the 6H15/2 → 6F11/2 + 6H9/2 transition has a high oscillator strength and the relation among the J-O parameters, Ωλ (λ = 2, 4, 6), is Ω2 > Ω4 > Ω6 for both glasses. The NSrFDy glass demonstrates a high value of stimulated emission cross-section and, hence, considered good for laser gain medium. We find that CIE coordinates are (0.37, 0.42) and (0.37, 0.41), while CCT values are 4378 K and 4426 K for NSrODy and NSrFDy glasses, respectively. [ABSTRACT FROM AUTHOR]

1 mol% Re2O3–99 mol% Ca3(PO4)2 (Re = Sm, Dy and Er) powder samples were prepared by solid-state sintering method. The structural, thermal, vibrational and optical properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Raman and photoluminescence techniques. XRD studies confirm the formation of β-Ca3(PO4)2 with the rhombohedral crystal structure. FESEM images reveal the formation of flake-like agglomerated particles of size in the range of 100–700 nm. DSC analysis shows that β-TCP → α-TCP structural phase transition occurs at 1286 ºC, followed by α-TCP → α'-TCP transformation at 1469 ºC. Raman spectra of the samples show antisymmetric and symmetric stretching and bending vibration bands of P-O linkages. Photoluminescence studies found intense reddish-orange emission in Sm-doped samples, white light emission in Dy-doped samples and yellow emission in Er-doped samples. The luminescence intensity of Sm and Dy-doped β-TCP samples is found to be significantly higher than that of Er-doped samples. [ABSTRACT FROM AUTHOR]

A new red‐emitting Eu3+ (1−17 mol%)‐doped Na3Mg4LiSi12O30 (NMLS) phosphor was prepared using a conventional solid‐state reaction method at low temperature. The prepared samples belong to a hexagonal structure with a good match to JCPDS card no. 73–0934. The photoluminescence (PL) emission spectrum showed an intense peak at 612 nm when excited at 393 nm. The variation of electric dipole transition (5D0–7F2) emission intensity with increasing Eu3+ ion concentration was investigated. The concentration quenching at 11 mol% is due to the dipole–dipole interaction mechanism in the NMLS host. The optimized NMLS:Eu3+phosphor shows 2.18 times higher luminescence intensity than the (Y,Gd)BO3 (YGB) commercial phosphor. The NMLS:Eu3+showed an intense red emission, having Commission Internationale de l'éclairage (CIE) coordinates (0.6280, 0.3691) and colour purity of 99.2%. The resulting phosphor exhibits good thermal stability of 80% at 423 K. The magnified images of fingerprint showed various minute features such as bridges, sweat pores, ridge end, bifurcation, island and core with better visualization under 393 nm excitation. Furthermore, the optimized NMLS:Eu3+ was used for pc‐LED, latent fingerprints, and anticounterfeit applications as a promising red phosphor. [ABSTRACT FROM AUTHOR]

Improving photophysical properties of poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]-end capped with dimethylphenyl, MDMO-PPV-DMP, was achieved via incorporation anatase titania nanoparticles (TiO2 NPs). Various contents of TiO2 NPs (up to 50 wt%) were dispersed into fixed concentration of the MDMO-PPV-DMP (5 mg/mL) via solution blending method followed by spin coating onto cleaned glass substrates to form their thin films. The formation of MDMO-PPV-DMP/TiO2 nanocomposites was evidenced from the results of X-ray diffractograms and Fourier transform infrared spectra, while the homogeneity of the films was detected by field emission-scanning electron microscopy (FE-SEM). Increasing the contents of TiO2 NPs resulted in a slight decrease (up to ~ 0.07 eV) in both direct and indirect energy band gaps of the MDMO-PPV-DMP in the nanocomposite thin films. A higher degree of disorder in the electronic structure of the MDMO-PPV-DMP/TiO2 nanocomposite and increasing the localized states density within the forbidden gap can be achieved by increasing the energy tail values and decreasing the steepness parameter with rising the TiO2 NPs content. The enhancement in emission intensity and broadening of emission spectra with increasing the TiO2 NPs content can be explained by the charge trapping effect and particle size distribution, respectively. Moreover, the incorporation of TiO2 NPs into the MDMO-PPV-DMP led to tuning its emitted light color which is of distinct interest in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Tb3+‐doped Na4Ca4Si6O18 (NCMS:Tb3+) phosphors were synthesized using a solid‐state reaction route with increasing dopant concentration. The phase identification studies for NCMS:Tb3+ phosphors were carried out using an X‐ray diffraction (XRD) technique. The XRD patterns for the as‐synthesized phosphors showed satisfactory agreement with the standard pattern (JCPDS card no. 75‐1687) for the pure phase of the Na4Ca4Si6O18 compound. The morphology and size of particles were illustrated from scanning electron microscope (SEM) micrographs. The photoluminescence excitation (PLE) spectrum of Tb3+‐doped Na4Ca4Si6O18 phosphor depicts the strong excitation peak obtained in the UV spectral region. The trivalent terbium‐activated NCMS phosphors excited in the UV region (232 nm wavelength) exhibited intense emission in the blue (350–470) and green (470–650) spectral regions. When increasing the concentration of Tb3+ ions in the host matrix, the emission colour shifted from the blue to the green region due to cross‐relaxation energy transfer (CRET) mechanisms and showed the tunable behaviour of the Tb3+‐activated as‐synthesized NCMS phosphor. These results demonstrated that the Tb3+‐activated sodium calcium metasilicate phosphor has immense potential to contribute as a green‐ and blue–green‐emitting component in lighting and display device applications. [ABSTRACT FROM AUTHOR]

The above figure represents graphical abstract of the combined spectra consisting of tunable emissions excited at various wavelengths of 1 mol % of singly and co-doped Dy3+/Eu3+- BaPbAlFB glasses The above figure represents graphical abstract of the combined spectra consisting of tunable emissions excited at various wavelengths of 1 mol % of co-doped Dy3+/Eu3+- BaPbAlFB glasses. [Display omitted] • The singly doped Dy3+, and Eu3+co-doped Dy3+/Eu3+ − BaPbAlFB glasses are prepared by using the melt quenching technique. • At various excitation wavelengths, luminescence properties of Dy3+/Eu3+ co-doped BaPbAlFB glasses are investigated. • The blue & yellow emissions of Dy3+ ions with red emission of Eu3+ ions in Dy3+ /Eu3+ co-doped BaPbAlFB glasses gives white light emission. • The CIE coordinates were different in different regions depends upon the concentration of Eu3+ ion and different excitation wavelength. Barium lead alumino fluoroborate (BaPbAlFB) glasses singly and co-doped with Dy3+ and Eu3+ ions were prepared by melt quench method and studied their photoluminescence (PL) properties along with energy migration. Singly doped Dy3+/Eu3+ ions in BaPbAlFB glasses under 365 and 393 nm excitation wavelengths emit the PL bands through Dy: (4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2) and Eu: (5D 0 →7F 2) transitions located at (Dy: 483 and 575 nm) and (Eu: 613 nm) respectively. Further, tunability of PL emissions is achieved by exciting the Dy3+/Eu3+ co-doped BaPbAlFB glasses at various wavelengths. The obtained CIE (0.34, 0.33) and CCT value (5080.4 K) of Dy3+/Eu3+ co-doped BaPbAlFB glass produced white light emission under 365 nm excitation wavelength. The corresponding CCT values of Dy3+/Eu3+ co-doped BaPbAlFB glasses varied from 1580 to 5080 K and their corresponding color emission changes from intense red to white light regime quite suitable for fabrication of epoxy-free w-LED devices. [ABSTRACT FROM AUTHOR]

• The visible light transmittance of the prepared glass sample is good (the transmittance is about 91%), and the maximum energy transfer efficiency is 46.9%. • Based on Judd-Ofelt theory, it is proved that Sm3+ and Dy3+ have strong inversion asymmetry and high covalency in boro-silicate glass, which is conducive to the realization of strong fluorescence emission. • By changing the Sm3+ ion concentration from 0.1 to 1.0 mol%, the CIE coordinates tuned to (0.4259,0.4345) under 348 nm excitation wavelength. As a result, genial warm white light can be realized. • Energy transfer mechanism involved in Dy3+→Sm3+ has been explained in terms of luminescence decay curve analysis. • The prepared glass has a long fluorescence lifetime, and the lifetime of SiBNM-DSm0.25 sample is up to 0.579 ms. By the melt quenching method, a series of colorless, transparent, multi-component borosilicate luminous glass samples were successfully prepared. The glasses undergo analysis using X-ray diffraction (XRD), transmittance spectroscopy, UV–visible absorption spectroscopy, photoluminescence (PL) spectroscopy, PL decay, Commission Internationale de L'Eclairage (CIE) color coordinates, and correlated color temperature (CCT). The results of laboratory optical studies were confirmed by the Judd-Ofelt (J-O) intensity parameter (Ω 2 , Ω 4 , Ω 6). Upon excitation at 348 nm, the Dy3+-Sm3+ co-doped glass exhibits a substantial drop in the intensity of the emission peak of Dy3+. Simultaneously, the emission peak intensity of Sm3+ increases due to the energy transfer (ET) from Dy3+. Energy is transferred from Dy3+ to Sm3+ through a dipole–dipole interaction. Their energy level diagram, emission spectrum, donor lifetime, and ET characteristic parameters all contribute to an explanation of this. Under 348 nm excitation, the CCT value is in the range of 3422–4233 K. The CIE coordinates changed to (0.4259, 0.4345) when the number of Sm3+ ions went from 0.1 mol% to 1.0 mol%, achieving high-quality warm white light ideal for warm white LED applications. The findings that were received validate the usefulness of the produced glasses for applications in photonic devices, such as warm white LEDs, solar cells, and display devices. [ABSTRACT FROM AUTHOR]

• Explored the potential of fluorinated terbium (III) complexes as materials for advanced OLEDs applications. • Examined the influence of different ancillary ligands on photoluminescent properties of Tb(III) complexes. • Substantial paramagnetic shifts observed for the protons of both hfpd (downfield shifts) and ancillary ligands (upfield shifts) are indicative of dipolar interactions with the paramagnetic center. • The synthesized complexes demonstrate promising attributes for applications in green-emitting displays, either by direct application or through incorporation into host matrices. Octa-coordinated, green light emitting Tb(III) complexes have been synthesized using hfpd = anion of 1,1,1,5,5,5-hexafluoro-pentane-2,4‑dione and different ancillary ligands. Spectroscopic analyses, employing elemental, HRMS, XRD, SEM, XPS, FTIR, NMR and PL, were used to investigate the chemical composition, electronic structure and photophysical properties. The coordination sphere of Tb(III) consists of six oxygen atoms provided by hfpd ligands and two atoms from the ancillary ligand. Optical energy gap corresponding to these complexes falls within the semiconductor range. Energy transfer mechanism for the synthesized complexes is also studied. The prepared complexes exhibit ligand sensitized metal centered emission, ∼ 70% branching ratio relative to hyperintense peak and high thermal stability, exceeding 250 °C. These characteristics, coupled with their cool light emission, evident from CCT values above 4000 K, makes them excellent candidate for displays and lighting technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we present new aspects of Sm3+‐doped pure Li2CaSiO4 as a suitable candidate for white light emitting diode (WLED) applications. The samples were mainly prepared using a conventional modified solid‐state synthesis technique. The structural studies were done using X‐ray diffraction and Rietveld refinement. Instruments such as a scanning electron microscope (SEM) were used to obtain information about the morphology of the as‐prepared samples. Photoluminescence (PL) analysis of phosphor samples for variable concentrations of doping ions with variable excitations were presented. When doped with Sm3+ in host Li2CaSiO4 it emitted intense blue, green and red emissions and a more intense red emission peak (605 nm) under 408 nm excitation (near‐UV–blue). Our study shows that the as‐prepared phosphor may be useful for optical devices and mainly for WLEDs. The corresponding transitions of doping ions and concentration quenching effect were studied in detail. The 1931 Commission Internationale de l'Eclairage (x, y) chromaticity coordinates showed the distribution of spectral regions calculated from PL emission spectra and this was found (0.63, 0.36) in the red region, so the phosphor may be useful for near‐UV–blue excited WLED applications. [ABSTRACT FROM AUTHOR]

Antimony-lead-oxyfluoroborate (SbPbOFB) glasses doped with various concentrations of Eu3+ ions were prepared by employing melt quenching and their luminescence activity was characterized using different spectroscopic methods such as optical absorption, photoluminescence (PL) excitation, PL emission, and PL decay. The Raman spectrum was recorded for an un-doped SbPbOFB glass to identify various functional groups present. The optical absorption spectra recorded for Eu3+ ion-doped SbPbOFB glasses showed five bands corresponding to 7F0→5L6, 7F0→5D2, 7F1→5D1, 7F0→7F6 and 7F1→7F6 transitions. The PL spectra measured under 394-nm excitation wavelength show five peaks corresponding to 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions at 578, 592, 613, 652 and 701 nm, respectively. Among them, that pertaining to the 5D0→7F2 transition appeared at 613 nm in the visible red region showing relatively high intensity. The Judd-Ofelt (J-O) parameters evaluated from the absorption spectral data are correlated with the prominent emission spectral features such as 5D0→7F1 (592 nm), 5D0→7F2 (613 nm) and 5D0→7F4 (701 nm) to estimate radiative properties such as transition probabilities (AR), branching ratios (βR) and emission cross sections (σ se). Quantum efficiency (η%) of the prepared glasses was estimated by correlating the radiative lifetimes with the experimental lifetimes measured from the PL decay spectral features. The PL emission spectral features are used to estimate the CIE color coordinates (x, y) of the studied glasses. The measured βR, σ se, η%, and the CIE coordinates estimated for the studied glasses revealed their suitability for visible red light-emitting device applications. [ABSTRACT FROM AUTHOR]

A novel tetradentate Schiff base ligand, 3-((2-(-(1-(2-hydroxyphenyl)ethylidene)amino)ethyl)imino)-2-pentone and its Ni(II) complex have been synthesized by green chemical, ultrasonication method. The ligand and metal complex were characterized analytically and spectroscopically by elemental analysis, HRMS, IR, 1H NMR, 13C NMR, UV–vis absorption spectroscopy, molar conductance, and magnetic susceptibility measurements. Powder XRD analysis was done to show the crystalline nature of the samples. The surface morphology and size of both ligand and complex were monitored by SEM and TEM microscopic techniques. Based on the various physicochemical measurements and spectral analysis, Ni(II) complex is assigned to an octahedral geometry. The optical bandgap energy, fluorescence spectrum lifetime analyses and chromaticity studies were accomplished to encounter the possibilities of optical applications. The fluorescence nature of both ligand and complex was found to be in the visible range. Optical bandgap energy values fall in the range of semiconductor materials. The chromaticity studies give the CIE 1931 coordinates and colour correlation temperature values of the samples. The ligand and the Ni(II) complex were screened for biological activities such as antimicrobial, antioxidant, and larvicidal activities. The results implied that the Ni(II) complex shows better antimicrobial, antioxidant and larvicidal activities than the free ligand.

Ce3+/Dy3+ (CDBB) and Ce3+/Sm3+ (CSBB) co-doped barium borate glasses were prepared by melt quenching technique. These glasses are made of B2O3 as a glass former and contain the luminescence activators of Ce3+, Dy3+ and Sm3+ rare earth ions. FT–IR spectra figured out the presence of various stretching and bending vibrations of borate groups in the prepared glasses energy dispersive X-ray spectroscopy (EDX) combined with SEM, enabled the study of near-surface elements and their quantities at various locations, resulting in a sample map. Optical absorption, optical band gap energy (Eg), Urbach energy (ΔE) and the linear refractive index (n) were calculated from the wavelength range observed from 1200 to 200 nm using UV-Vis spectrometer. The emitting wavelengths including 435 (blue), 560 (green), 600 (reddish orange) and 645 nm (red) were observed simultaneously in the luminescent spectra of CSBB at the prominent excitation wavelength of 400 nm, and the mixture of these four emissions yields the white light emission. Further, the energy transfer process occured due to sensitizer-activator ion pairs via a non-radiative mechanism. Notably, co-doping Ce3+and Sm3+ ions increased red emission by efficiently transferring energy from Ce3+ to Sm3+ in the CSBB glass. The CIE chromatograph coordinate (x = 0.339, y = 0.331) of the emission from the CSBB glass is close to the standard white-light illumination (0.320, 0.348). The measured excitation purity (Pe) and colour purity (Pc) of these glasses revealed the quality of their light emission. Furthermore, the synthesized CDBB glasses have reasonable non-linear optical (NLO) properties with stronger SHG intensity of 11.0 mV. [ABSTRACT FROM AUTHOR]

Eu3+/Nd3+ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF 2 +10K 2 O +20SiO 2 +(49-x) B 2 O 3 +1Nd 2 O 3 +xEu 2 O 3) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu3+ ions in the Nd3+ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of 7F 0 → 5L 6 band (394 nm) with the increasing concentration of Eu3+ ion in the Nd3+ excitation spectra (λ emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd3+ ion with the typical excitation wavelengths (Nd3+ = 584 nm and Eu3+ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE3+ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu3+ and Nd3+ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu3+/Nd3+ co-doped glasses with other Nd3+ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu3+ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications. Image 1 [ABSTRACT FROM AUTHOR]

The present investigation describes the synthesis of luminescent terbium-doped strontium aluminate nanoparticles emitting bright green light, which were synthesized through a solid-state reaction method assisted by microwave radiation. Various samples containing different concentrations of Tb were synthesized, and an analysis of their structural and morphological features was conducted using powder x-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The band gaps of the samples were determined utilizing the Kubelka-Munk method. The quenching mechanism observed was identified to be due to dipole-dipole interaction using the Dexter theory. The optimized sample with a terbium concentration of 4 at.% has a luminescence lifetime of 1.05 ms with 20.62% quantum efficiency. The results of this study indicate that the terbium-doped strontium aluminate fluorescent nanoparticles exhibit promising potential for a wide range of applications, including bioimaging, sensing and solid-state lighting., (© 2024 John Wiley & Sons Ltd.)

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured.

A series of Dy3+ doped aluminoborosilicate glasses with general formula 20SiO 2 -(40-x) B 2 O 3 –10Al 2 O 3 –20NaF 2 –10ZnO-xDy 2 O 3 (x = 0, 0.1, 0.5, 1.0. 1.5, 2.0 and 2.5 mol %) were prepared by melt-quenching method. The FTIR analysis confirms the presence of stretching and bending vibrations of BO 4 , BO 3 and SiO 4 units in the prepared glasses. DTA results show that Tg is decreasing with addition of Dy3+ ions in the glass system. Theoretically calculated mechanical properties such as elastic modulus, bulk modulus, shear modulus and Poisson's ratio suggest the increase in mechanical stability of glasses with dysprosium addition. Also experimental analysis carried out using Vicker's microhardness suggests glass stability with applied loads. Absorption spectrum shows twelve bands that exist due to transition from 6H 15/2 level to different excited levels. Nephelauxetic ratio and bonding parameter calculated shows decreasing ionicity of glasses with increase in Dy3+ ions. Judd-Oflet parameter calculated for all the glasses follow the trend Ω 6 > Ω 4 > Ω 4. Luminescence study shows three emission peaks having transitions from 4F 9/2 → 6H 15/2 (blue), 4F 9/2 → 6H 13/2 (yellow) and 4F 9/2 → 6H 11/2 (red). Radiative parameters calculated suggest higher stimulated emission cross-section for present glasses having 4F 9/2 → 6H 13/2 transition. The decay measurement for all the glass samples were recorded with an excitation at 350 nm and monitoring emission at 575 nm corresponding to the 4F 9/2 → 6H 13/2 transition and decay curves were fitted to bi-exponential fit. The CIE colour chromaticity coordinates were determined using CIE chromaticity diagram and the values were found to be in close proximity with the standard white light (0.33. 0.33) for all the glasses. Further colour correlated temperature values were found to lie in the near bright white region with CCT around ~4000 K. • Various concentrations of Dy3+-doped SiO 2 –B 2 O 3 –Al 2 O 3 –NaF–ZnO glasses were synthesized. • Mechanical properties of these glasses were studied along with experimental analysis. • Optical bandgap and Urbach energy of these glasses were calculated. • Energy transfer mechanism and radiative parameters were studied. • All Dy3+- doped glasses CIE (x, y), and CCT values represent the bright white light region. [ABSTRACT FROM AUTHOR]

Calcium borophosphate (CBP) phosphors doped with Dy3+ were synthesized by solid-state reaction method. These phosphors were characterized by photoluminescence spectra and decay curves in the visible region. These phosphors were excited at 350 nm, and emission spectra were studied. Decay curves were obtained for the transition, 4F9/2 → 6H13/2 of Dy3+, and lifetimes were measured for different concentrations of Dy3+ ions. CIE chromaticity coordinates were obtained for these Dy3+-doped CBP phosphors. Correlated color temperature was also calculated using the standard formula. [ABSTRACT FROM AUTHOR]

A series of Dy3+ doped zinc-aluminoborosilicate glasses with chemical composition 30SiO 2 -(30-x) B 2 O 3 –10Al 2 O 3 –15NaF–15ZnF 2 -xDy 2 O 3 (x = 0, 0.5, 0.7, 1.0 and 1.5 mol %) were prepared by conventional melt-quenching method. Structural and optical properties of the glasses were analyzed through XRD, FTIR, UV–Visible–NIR and luminescence studies. Gamma radiation shielding parameters were obtained using PSD software. Nephelauxetic ratio (β) and bonding parameters (δ) calculated using absorption spectrum shows the decreasing ionic nature of the Dy ions. Judd-Oflet parameters (Ω 2 , Ω 4 and Ω 6) obtained shows the covalency and asymmetric nature of dysprosium ions. The luminescence properties shows that Dy3+ doped glasses have two strong intense emission at blue (482 nm) and yellow (575 nm) region. Branching ratio and stimulated emission cross section calculated suggests the glasses suitability to act as lasing material. CIE colour coordinates and its colour correlated temperature (CCT) for the glasses were estimated and found that these prepared glasses lie in the warm white light region. Image 1 • Various concentrations of Dy3+-doped SiO 2 –B 2 O 3 –Al 2 O 3 –NaF–ZnF 2 glasses were synthesized. • Judd-Oflet intensity parameters were evaluated from absorption spectra, for all glasses. • All Dy3+- doped glasses CIE (x, y), and CCT values represent the warm white light region. • Photon-Shielding and Dosimetry (PSD) software was used to calculate (μ/ρ) at different energies. • With the addition of Dy 2 O 3 , the shielding efficiency of the prepared glasses is improved. [ABSTRACT FROM AUTHOR]

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. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Here, we report the synthesis of Sr2−xEuxSiO4 (Sr2SiO4:Eu3+) [x = 0.01, 0.015, 0.02, 0.025, 0.03] silicate phosphors via high-temperature solid-state reaction method. The prepared phosphors were X-ray diffraction (XRD) characterized, and the analysis of XRD data conveyed that all the samples are crystalline, single-phased and have crystallized to orthorhombic structure (Pmnb). The structure, space group (Pmnb) and other structure concerned parameters were further verified using Rietveld refinement for x = 0.01 phosphor. The XRD pattern for all the synthesized phosphors was identical in appearance, and there is no evidence of the new peak with increased doping of Eu3+ ion. This behavior may be attributed to the uniform distribution of rare earth Eu3+ ion at Sr2+ site due to comparative ionic size of the host and guest ion. The formation of Sr2SiO4:Eu3+ phosphors is verified further by FTIR spectroscopic technique. To investigate optical band gap of prepared phosphors, UV–Vis diffuse reflectance spectroscopic studies have been carried out. Photoluminescence property of Sr2SiO4:Eu3+ phosphors was studied. The emission spectrum displayed characteristic emission peaks corresponding to Eu3+ around 587, 612 and 702 nm. The Commission International de I'Eclairage color coordinates were found lying in orange-red region. [ABSTRACT FROM AUTHOR]