Inokuti-Hirayama Research Articles

Solution combustion derived color-tunable Eu3+ doped Ca8ZnBi(VO4)7 nano sample for luminous devices and latent fingerprinting applications

Eu3+ doped Ca8ZnBi(VO4)7 host lattice have been produced through an environmentally friendly, economical, and energy-efficient solution combustion synthesis. The trigonal phase with the R 3c space group of the constructed series was verified by x-ray diffraction and Rietveld refinement technique. The elemental and morphological study was done by using energy dispersive X-ray analysis (EDAX) and scanning electron microscope (SEM), transmission electron microscope (TEM) respectively. In the excitation spectra, the intense band at 334 nm indicates the transfer of energy occur between VO43- → Eu3+. The color-tunable features of the generated nanosample are indicated by the emission (617 nm, 5D0→7F2) color of the nanophosphor, which lies in the yellow, orange, and red regions for varying doping amounts. The band gap was determined using Tauc’s hypothesis for both host lattice (3.18 eV) and Eu3+ doped nanomaterials (3.13 eV) which lie in the range of semiconductors. The use of Dexter’s theory and the Inokuti-Hirayama (I-H) model verified the existence of dipole–dipole (d-d) type interlinkages as a genuine phenomenon for concentration quenching. Additionally, Auzel’s system was used to study radiative lifetime (0.6510 ms), quantum efficiency (59.51 %), and non-radiative rates (621.8 s−1). The CIE coordinates (0.5164, 0.4703), lower value of correlated colour temperature (CCT) (2459 K) and color-tunable phenomena made it a possible choice for warm white light emitting luminous devices. The optimized nanophosphor has been investigated for latent fingerprinting and has been successful in identifying all of the fingerprint’s levels-1, 2 and 3.

Structural elucidation by Raman spectroscopy and analysis of luminescence quenching by the Inokuti-Hirayama model in the Pr3+ doped multi-component silicate photonic films

Thin films of multi-component silica glasses doped with Ca2+ and Pr3+ modifiers were fabricated by the spin coating technique. Surface micrographic images extracted by the Field Emission Scanning Electron Microscope revealed a homogeneous texture of the films. Detailed structural analysis by Fourier Transform Raman spectroscopy confirmed the existence of Si-O-Si and polyphosphate groups in the glass matrix. The Burstein-Moss shift was evidenced with doping, by an increase in the band gap of the glass films, evaluated by Tauc’s plots. The films exhibit red and near infra-red emissions (NIR), corresponding to the transitions: 3P0→3F2 and 3P0→3F4 respectively. The decay analysis by the Inokuti-Hirayama (I-H) model validated the contributions of multi-polar interactions particularly that of dipole-quadrupole mechanisms, leading to significant quenching in the highly doped film. The energy transfer efficiency between the sensitizer and activator ions, determined by the formulations of the model was 51.8 %. The decreasing lifetime of the metastable state observed in the glass films could be considered to be prospective for NIR waveguide lasers and red laser sources for optical display screens.

Preparation and luminescence properties of Ce3+/Sm3+ codoped A-Lu2SiO5@SiO2 core-shell nanospheres

X-ray induced photodynamic therapy (X-PDT) has been applied as an effective strategy against cancer. A novel nanoscintillator A-Lu2SiO5:Ce3+,Sm3+@SiO2 core-shell nanosphere was fabricated and its practicability in X-PDT has been demonstrated in this work. The emission and excitation spectra of the co-doped samples were measured, and the energy transfer (ET) from Ce3+ to Sm3+ was investigated using the Inokuti-Hirayama (I-H) model, revealing that the dominant mechanism of ET in the sample Lu2SiO5:Ce3+,Sm3+@SiO2 nanospheres would be electric dipole-dipole interaction. In particular, the corresponding spectra demonstrated ET between Ce3+ and Sm3+ under X-ray excitation, while light yield has been estimated for a representative co-doped sample. It was concluded that the as-prepared A- Lu2SiO5:Ce3+,Sm3+@SiO2 core-shell nanospheres have potential applications for the simultaneous excitation of blue and red activated photosensitizers in X-PDT as material for nanoscintillators.

Luminescence Studies on Dy3+ Doped Calcium Aluminum Borosilicate (CABS) Glasses for White Light Emission and Applications in w-LEDs.

Dy3+ doped calcium aluminum borosilicate (CABS) glasses have been synthesized via quick melt quench technique. CABS: xDy3+ glasses (x = 0.1, 0.5, 1, 1.5 and 2mol%) were subjected to various morphological and photoluminescence studies. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were conducted to study the structural and bonding nature of the undoped glass. The excitation spectra of Dy3+ doped CABS glasses under 574nm emission show many sharp peaks amongst which the transition from 6H15/2 → 6P7/2 (351nm) had the highest intensity. Under 351nm excitation, glasses exhibit sharp peaks in the blue, yellow and red regions corresponding to the transitions 4F9/2 → 6H15/2, 6H13/2, 6H11/2 and 6H9/2 respectively. The dipole-dipole nature of the interaction between the Dy3+ ions is confirmed via Dexter theory and Inokuti-Hirayama (I-H) model. CIE coordinates estimated from the emission profiles of these glasses under 351nm excitation fall in the white region. Considering that these glasses exhibit sharp visible emission under UV excitation, have stable yellow to blue (Y/B) ratios and fast decays with intense energy transfers, we propose to utilise these glasses for white light generation and other white light LED (w-LED) and solid-state lighting (SSL) applications.

Nonlinear optical and luminescence studies on Zinc Alumino-Boro-Silicate glasses co-doped with Dy3+ and Sm3+ ions for optical limiting and W-LEDs applications

In the present work, Dy3+ and Sm3+ co-doped Zinc Alumino-Boro-Silicate (ZABS) glasses doped with an optimized Dy3+ concentration (0.5 mol%) and varying Sm3+ concentrations are prepared using a conventional melt-quenching method. Optical absorption spectra showed the signature of Dy3+ and Sm3+ peaks through possible transitions in the range of 300–1800 nm. The optical bandgap of the glasses is obtained in the range of 4.2 to 3.9 eV. The emission curves aswellas decay lifetimes of Dy3+ and Sm3+ ions under 350 nm and 402 nm excitation were investigated using photoluminescence studies. Through the Inokuti-Hirayama (I-H) energy fitting model, the nature of energy transfer between Dy3+ and Sm3+ is found to be a ‘dipole–dipole’ type. Neutral to near warm white light emissions from the co-doped glasses were evaluated through colour chromaticity and correlated colour temperature calculations. The nonlinear optical measurements showed the reverse saturable absorption behaviour of the glasses whose nonlinear absorption coefficients (β) decreased with higher concentrations of Sm3+. Among the prepared glasses, ZABSDS1 (Sm3+ 0.1 mol%) glass showed the highest nonlinear coefficient (3.56 × 10−12 W cm−2) and lowest optical limiting (37.5 × 1011 W cm−2) threshold. From the overall studies, the suitability of the prepared glasses for White LEDs and optical limiting laser device applications were realized.

Structural, optical, and luminescence properties of Dy3+ -activated potassium calcium silicate phosphor for white light-emitting diodes.

A dysprosium (Dy3+ )-activated potassium calcium silicate (K4 CaSi3 O9 ) phosphor was prepared using a solid-state synthesis route. The phosphor had a cubic structure with the space group Pa as confirmed using X-ray diffraction (XRD) measurements. Details of surface morphology and elemental composition of the as-synthesized undoped KCS phosphor was obtained using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The chemical structure as well as the vibrational modes present in the as-prepared KCS phosphor was analyzed using Fourier transform infrared (FT-IR)spectroscopy. Diffuse reflectance spectra (DRS) were used to determine the optical bandgap of the phosphors and were found to be in the optical range 3.52-3.71 eV. Photoluminescence (PL) spectra showed intense yellow emission corresponding to the 4 F9/2 →6 H13/2 transition under 350 nm excitation. Commission International de l'Eclairage colour chromaticity coordinates were evaluated using the PL spectral data lie within the white region. Dexter theory and the Inokuti-Hirayama (I-H) model were applied to study the nature of the energy transfer mechanism in the as-prepared phosphors. The relatively high activation energy of the phosphors was evaluated using temperature-dependent PL (TDPL) data and confirmed the high thermal stability of the titled phosphor. The abovementioned results indicated that the as-prepared KCS:Dy3+ phosphor was a promising candidate for n-UV-based white light-emitting diodes.

Efficient tunable photoluminescence of Dy3+/Eu3+ co-doped OFSZBS glasses for warm white LEDs

A series of oxyfluoride strontium zinc borosilicate (OFSZBS) glasses co-doped with Dy3+/Eu3+ ions was prepared via melt quench method. The structural properties were examined using XRD and scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX) on DE2.0 and undoped OFSZBS glasses, respectively. UV–Vis absorption spectroscopy was used to evaluate the direct & indirect energy band gaps. At different excitations (348, 362, 385 and 393 nm), the photoluminescence (PL) spectra were observed with tuned light. Warm white light was generated through the Dy3+ (4F9/2→6H15/2, 6H13/2) and Eu3+ (5D0→7F2) transitions. Dexter Reisfield approximation applied to PL data revealed a dipole-dipole (d-d) mechanism accountable for the energy transfer (non-radiative) between sensitizer (Dy3+) and activator (Eu3+) ions. The energy transfer efficiency in the co-doped glass samples was found between 8% to 50%, depending on the doping. The Inokuti-Hirayama (I-H) fitting of PL decay profiles also confirm the energy transfer mechanism. The CIE chromaticity color coordinates observed for OFSZBSDE2.0 glass also confirm the color tunability. The above findings reveal the applications of as-prepared Dy3+/Eu3+ co-doped OFSZBS glasses excited using n-UV light for warm white LEDs and tuned devices.

Investigation on luminescence properties and XANES of dysprosium ion doped borophosphate glasses

In this research, melt quenching was used to prepare Dy3+ ion doped alkaline borophosphate glasses. According to the XANES measurement, Dy ions in glass show +3 oxidation state, identical to the standard Dy2O3 powder. Glasses were measured for density (ρ), molar volume (Vm), and refractive index (n). The absorption peaks, which are assigned to transitions from the ground state 6H15/2 to higher energy levels of Dy3+ ion in glass matrix. Four prominent emission bands were observed in luminescence spectra, which correspond to the 4F9/2→6HJ (J = 15/2, 13/2, 11/2, 9/2) transitions. The Judd-Ofelt (J-O) intensity parameters follow the trend as Ω2>Ω6>Ω4 of the PBLAGdDy1.0. For the stimulated emission cross-section and branching ratio (>0.5), 4F9/2 → 6H13/2 transition was found to be higher than other transitions. Because the decay curves of glasses with different concentrations of Dy3+ ion were found to be non-exponential, these glasses were calculated using the Inokuti-Hirayama (I-H) model. The obtained photoluminescence and decay times spectra primarily showed energy transfer effects from Gd3+ to Dy3+ ions and the calculated values of energy transfer efficiency (η) found that the values increased, which confirms energy transfer from Gd3+ to Dy3+ ions. From this study, the current glasses could be useful in the applications of solid-state lasers, LEDs, and scintillation materials.

Color tuneability behaviour and energy transfer analysis on Dy3+-Eu3+ co-doped glasses for NUV-WLEDs application

A series of Dy3+ and Eu3+ co-doped zinc aluminoborosilicate (ZABS) glasses were synthesized by a high-temperature melt-quenching method. Visible and NIR transitions of Dy3+-Eu3+ ions are observed through absorption spectra. A reverse trend in the optical band gap values and Urbach energy are seen with addition of Eu3+ ions. Photoluminescence studies recorded under different excitation wavelengths showed a variation in the emission intensities and prevailed the color tuneability behaviour of dopants. The energy transfer between Dy3+ and Eu3+ ions are studied through emission profiles, energy level diagram, and decay curves. The type of multipolar interaction between Dy3+ and Eu3+ are understood via Inokuti-Hirayama (IH) model and Dexter energy model. The CIE chromaticity coordinates, and correlated color temperature (CCT) values suggest that the prepared glasses can be used for light emitting diode application when excited at near-ultraviolet region.

Photoluminescence properties of novel blue-light excited orange-red phosphors Sr3Al2Si3O12:Eu2+

Developing red phosphors for LEDs is highly demanded yet challenging. Herein, a novel Eu2+-activated orange-red phosphors Sr3-xAl2Si3O12:xEu2+ (SASO:xEu2+) (0 ≤ x ≤ 0.08, ∆x = 0.01) were successfully prepared by high-temperature solid-phase reaction. The phosphors all belong to the cubic crystal system, and the space group is Fm-3 m(225). Phosphors SASO:xEu2+ can be efficiently excited by wavelengths in the range of 420–500 nm and produces strong orange-red light emission at 618 nm. In phosphors SASO:xEu2+, the optimal doping concentration of Eu2+ is 0.06, and the Inokuti–Hirayama (I-H) model shows that the energy transfer between Eu2+ ions is mainly due to the dipole-dipole (d-d) interaction. The phosphors SASO:xEu2+ have excellent thermal stability, the fluorescence intensity of phosphor SASO:0.06Eu2+ at 418 K still maintains 69.57 % of the fluorescence intensity at room temperature. Phosphor SASO:0.06Eu2+ has a high luminescence quality with a color purity of 86.5 %, which exhibits bright orange-red emission under 450 nm illumination.

Color-tunable emissions realized by Tb3+ to Eu3+ energy transfer in ZnGdB5O10 under near-UV excitation.

Photoluminescent (PL) energy transfer (ET) between two typical rare earth activators Tb3+ and Eu3+ is utilized to achieve color-tunable emission and the color range is apparently dependent on the ET efficiency. In the target host ZnGdB5O10 (ZGBO), the relatively low symmetric coordination environment of the rare earth cation not only suppresses the parity-forbidden law of the 4f-4f transitions of Tb3+ in the near-UV region, but also enhances the internal quantum efficiency (IQE), where the optimal IQE is 65.61% for ZGBO:0.8Tb3+. Moreover, its ET to Eu3+ is highly efficient, i.e. 94.71% in ZGBO:0.8Tb3+,0.10Eu3+, which eventually leads to a wide range of color-tunable emissions from green (0.2915, 0.5915) to red (0.6207, 0.3731). The systematic PL spectral study on Tb3+/Eu3+ singly doped and co-doped phosphors suggests that the ET mechanism takes place through the electric dipole-dipole interaction according to the Inokuti-Hirayama (I-H) model. Additionally, the in situ high temperature PL spectra indicate the very high thermal stability of ZnGd0.19Tb0.8Eu0.01B5O10, indicating that it can be a potential candidate for near-UV light emitting diode-pumped phosphors.

Tb3+-Tb3+ cross-relaxation study under novel experimental technique: Simultaneous laser excitation at UV–Vis

Tb3+ doped GeO2-Na2O glasses have been fabricated by conventional melt quenching technique using 0.3, 1, 3, and 5 %mol of terbium ions. The optical properties were studied by means of steady-state photoluminescence (excitation and emission spectra), and emission decay time. Under excitation of 355 nm and as the concentration of dopant increases, the glasses show an enhancement of the emission intensity from 5D4 level accompanied by a decrease on the emission intensity from 5D3 level. This phenomenon can be attributed to an energy transfer process that occurs through cross-relaxation mechanisms between Tb3+ ions. The aim of this study is to report an experimental technique to study the cross-relaxation of 5D3 level decay curves of Tb3+ ions under simultaneous temporal and spatial pulsed excitation using UV and visible light (355 nm + 488 nm), allowing to limit the occurrence of cross-relaxation mechanisms and increase luminescent efficiency. Upon simultaneous UV + Vis excitation, the emission from 5D3 level in enhanced, as the energy of the 488 nm pulse is increased. Additionally, the energy transfer efficiency between Tb3+ ions was analyzed with the Inokuti-Hirayama (IH) model, as function of the excitation pulse energy at 488 nm, keeping fixed the energy of the 355 nm pulse, determining a dipole–dipole interaction as the dominant interaction mechanism.

Effect of Gd2O3 concentration on photo and X-rays excited luminescence characteristics of Dy3+-Activated Li2O3–SrO–B2O3 glass

Gd3+ and Dy3+-doped borate glasses are considered attractive candidates for white light emission. In this work, the samples, developed by the melt-quenching route, contain a mixture of Gd3+ and Dy3+ with known molar compositions. The determined physical parameters indicate structural changes. Information regarding the Judd-Ofelt (JO) intensity parameters and spectral radiative features, calculated from absorption spectra and emission properties, respectively, are obtained. Excitation and photoluminescence characteristics of the developed samples are found. The energy transfer (ET) efficiency from Gd3+ → Dy3+ is determined by considering their emission intensities and lifetime. The quantum efficiency (QE) of glasses is evaluated. Inokuti –Hirayama (IH) model shows that the Dy3+ → luminescence center ET is dominated by dipole-dipole coulomb interaction. Due to the excitation of more secondary electrons, the X-ray luminescence shows an intense emission pattern. Furthermore, we find the integral scintillation efficiency to be 8.4% of the commercial BGO scintillator crystal for the 10 mol% Gd2O3-doped glass. Commission International deI’Eclairage (CIE) color coordinates and color correlated temperature (CCT) show the suitability of tested samples for white-light applications.

Tunable Luminescence and Energy Transfer of Sr3B2O6:Ce3+, Sm3+ Phosphors with Potential Anti-Counterfeiting Applications.

Sm3+ and Ce3+ singly doped and Sm3+ and Ce3+ co-doped Sr3B2O6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm3+-doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm3+ ions. Upon 340 nm excitation, the Ce3+-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6H5/2 → 6P3/2 excitation line of Sm3+ and implies the possible energy transfer from Ce3+ to Sm3+. The spectral and decay measurements of the Ce3+ and Sm3+ co-doped samples are conducted and the Inokuti–Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce3+. Owing to the evident sensitization of the Sm3+ by the Ce3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.

Structural and luminescence characteristics of thermally stable Dy3+ doped oxyfluoride strontium zinc borosilicate glasses for photonic device applications

Structural, thermal, and photoluminescence (PL) characteristics of a series of Dy3+ doped Oxyfluoride Strontium Zinc Borosilicate (OFSZBS) glasses have been investigated. The XRD of 1.0 mol% Dy3+ ions doped OFSZBS glass and FT-IR investigations conducted on an un-doped as well as all the Dy3+ ions doped OFSZBS glasses confirm the non-crystalline nature and distinct functional groups present in it respectively. The Differential Scanning Calorimetry (DSC) thermogram recorded for an un-doped OFSZBS glass reveals thermal stability (ΔT) and transition temperature (Tg). The optical band gaps were computed using the Tau'c method. Under 348 nm pumping wavelengths, the Photoluminescence (PL) spectra of the as-synthesized OFSZBSDy glass samples exhibit blue (450 nm), yellow (575 nm), and red (650 nm) color transitions. The PL intensity increases with Dy3+ ions concentration up to 1 mol% and after that intensity decreases due to the concentration quenching effect. The PL decay profiles reported at higher concentrations were best fitted to the Inokuti-Hirayama (I-H) model for s = 6, indicating the energy transfer process as dipole–dipole in nature. The result obtained from the I-H model is in consonance with that of Dexter's theory. At 448 K, the PL intensity is up to 85% of room temperature, indicating that the as-synthesized glasses have exceptional thermal stability. Relatively higher values of quantum efficiency (η), emission cross-sectional area (σse), and probability of radiative transition (AR) observed for 1 mol% Dy3+ ions doped OFSZBS glasses declare their suitability in photonic devices under n-UV/blue pumping wavelength.

Color tunable photoluminescence in KZABS: Tm3+ glasses under different sources of excitation for photonic applications

Potassium Zinc Alumino Borosilicate (KZABS) glasses doped with Tm3+ ions have been prepared by using a melt quenching process and further investigated through various spectroscopic tools such as optical absorption, photoluminescence (PL) excitation, PL emission, and PL decay measurements. The non-crystalline nature of the as-prepared glasses was confirmed by XRD measurements. PL spectral properties show blue and red colors under different excitation wavelengths. The absorption spectrum recorded in the UV-Vis-NIR range reveals the high bandgap energy. The Inokuti-Hirayama (I-H) model well fitted to non-exponential decay curves confirms the energy transfer between Tm3+-Tm3+ ions as dipole-dipole in nature. Under 359 and 466 nm excitation wavelength the titled glasses are showing CIE coordinates falling in deep blue and deep red color, respectively. A good color tunability can be seen from the blue to the red region under different excitation wavelengths. All the studies finally reveal the superiority of Tm3+ doped KZABS glasses for their usage in blue/red-emitting photonic devices needed to fabricate photonic devices such as w-LEDs.

Structural and optical conduct of cool white-light emanating BaGd2ZnO5:Dy3+ nanocrystals for white LEDs

An orthorhombic symmetry type BaGd2ZnO5:Dy3+ nanocrystals with luminance of cool white-color light have been fabricated via urea assisted combustion methodology. Morphological analysis revealed the agglomerated particles with non-uniform shape having crystal-size of 30–40 nm. Optimized amount of dopant (Dy3+) was examined to be x = 3 mol%, after the occurrence of quenching phenomenon. The logical pathways for quenching mechanism has been determined as non-radiative (NR) relaxations of energy via exchange-type interrelations as validated by Inokuti-Hirayama (I-H) and Dexter’s theory. Fabricated nano-powders represents two band located at 492 nm (bluish) and at 581 nm (yellowish). Band gap, decay life time and quantum efficiency of optimal powder were found as 4.71 eV, 0.7049 ms and 93.9% respectively. White-light emanation is reflected in terms of CIE color-parameters like color-coordinates of white regions (0.2869, 0.3876), color purity of 30 × 10−2 and CCT values as 7206.2 K, which have been in congruence with standard coordinates of commercial LEDs and NTSE and thus, authenticate their optimistic applicability for advanced illuminating devices.

Energy transfer dynamics in thermally stable Sm3+/ Eu3+ co-doped AEAlBS glasses for near UV triggered photonic device applications

Transparent, Sm3+/Eu3+ co-doped alkaline earth alumino borosilicate (AEAlBS) glasses have been synthesized by employing melt quenching process and explored their down-shifting luminescent properties to understand their utility in visible red photonic devices applications. The amorphous (non-crystalline) nature of the as-prepared glasses was analyzed with help of an X-ray powder diffraction (XRD) pattern, containing a broad peak. Photoluminescence (PL) properties demonstrate that the glasses can be proficiently excited by near-UV with a dominant peak centered at 402 nm. The PL emission spectra exhibit four emission peaks with an intense peak placed at 599 nm under 402 nm excitation. The optimum emission intensity was obtained for 0.5 mol% Sm3+ ions doped in AEAlBS glasses. In the present work, Sm3+ ion is acting as an effective sensitizer for Eu3+ activator in AEAlBS glasses, and part of energy gets transferred from sensitizer (Sm3+) to activator (Eu3+) ions. The PL intensity of Eu3+ ions is increasing at the expense of a decrease in the intensity of Eu3+ ion peaks in the co-doping AEAlBS glasses at λex = 402 nm. The efficient ET from sensitizer to activator ions proved to be dipole-dipole in nature via employing Dexter's formula with Reisfeld's approximation. The experimental lifetime values calculated from the PL decay profiles are decreasing with the surge in Eu3+ ion concentration in the as-prepared glasses. Inokuti Hirayama (I-H) model applied to the PL decay profiles confirms the ET process responsible for a decrease in experimental lifetimes as dipole-dipole in nature. The outcome of the I-H model is in consonance with the result given by Dexter theory. The CIE coordinates for single Sm3+ doped glasses are falling in the orange region and gradually surge into the red region by co-doping with Eu3+ ions in AEAlBS glasses. The temperature-dependent emission analysis reveals that the PL intensity at 150 °C and 200 °C perseveres up to 94.34 and 91.30% of the PL intensity at ambient temperature, respectively. All the obtained results contemplate the superiority of the multifunctional Sm3+/Eu3+ co-doped AEAlBS glasses for near UV triggered photonic device applications.

Crystal structure and optical analysis of new reddish-orange Sm3+ doped BaGd2ZnO5 nano-crystalline materials for multifunctional applications

In the present report, a new series of Sm3+ doped BaGd2ZnO5 nanomaterials emanating reddish orange light have been manufactured via an ecological, ideal and less energy consuming combustion methodology. Crystallographic investigation reports the orthorhombic symmetry type with Pbnm (62) space group. Morphological analysis examines the non-uniform agglomerated particles of 35-45 nm. Photoluminescent (PL) studies reveals about the orange red emanation from the fabricated nanomaterials by recording the PL emission spectrum, which shows a fine peak at 610 nm and also discloses that the exchange type interrelations as the main mechanism for non-radiative relaxation of energy, as validated by Inokuti-Hirayama (I-H) and Dexter's theory. Band gap, decay life time, quantum efficiency and non radiative rates of optimal powder were found as 4.84 eV, 0.607 ms, 87.84 % and 0.20 ms1, respectively. At the last, excellent luminescent performance is reflected in terms of CIE color parameters like color –coordinates (0.579, 0.420), color purity (78.88 %) and 1768 K color correlated temperature (CCT). These magnificent results certified the relevancy of the targeted nanocrystals as an auspicious agent in the manufacturing of advanced illuminating appliances like WLEDs, lasers, photonic devices, solar cell, sensors and various opto-electronic appliances.

Augmenting the photoluminescence efficiency via enhanced energy-relocation of new white-emanating BaYAlZn3O7:Dy3+ nano-crystalline phosphors for WLEDs

Ongoing progress of solid-state illumination technology necessitates the compelling need for energy-efficient nanophosphors with superfine luminance. The present paper reports the synthesis and characterization of nano-crystalline phosphors by incursion of Dy3+ ions into BaYAlZn3O7 matrix. Rietveld-refinement of XRPD profiles revealed the hexagonal structure of as synthesized nano-crystalline phosphors. Non-uniform agglomerated particles with size ranging between 44 and 65 nm have been observed from morphological investigation. The observed white light in the studied nanophosphors is due to emissions lying in blue and yellow domains radiated from 4F9/2 to 6H15/2, 13/2 states of Dy3+ respectively. Inokuti-Hirayama (I-H) and Dexter’s models have been employed to understand the phenomenon of Photoluminescence. It has been observed that d-d (dipole-dipole) inter-linkages chiefly command the luminance-quenching for nanophosphor with Dy3+ content (x) equal to 0.05. Various radiative-possessions reflecting better luminance-potentiality of presently studied nanophosphor like decay-time, intrinsic life-time, quantum-efficiency and relaxation-rate have also been evaluated. White light parameters viz. CP and CCT values of BaY0.95Dy0.05AlZn3O7phosphors are 19.84 × 10−2 and 8088.31 K, respectively along with CIE-1931 coordinates (x = 0.2588, y = 0.3306), imply the studied nanophosphor to be a new superfine cool-white-emanating material for nUV-activated WLEDs (white-light-emanating diodes), portable-electronics, signage, aircraft-cabins, digital communication, sensors, horticulture, solar-cells and advanced lasers. The reported outcomes will certainly open an avenue for researchers to design more BaYAlZn3O7-like materials.