Luminescence Thermometry Based on the Upconversion Luminescence from the Stark Sublevels of BaY2F8:Yb3+, Tm3+ Phosphor

Visible and near-infrared (NIR) upconversion luminescence (UCL) emissions originating from the BaY2F8: Yb3+, Tm3+ systems were investigated under a laser excitation at 980 nm. The BaY2F8:20 mol% Yb3+, x mol% Tm3+ and BaY2F8: y mol% Yb3+, 0.5 mol% Tm3+ phosphors showed prominent UCL at 800 and 810 nm. The optimized doping concentrations of Yb3+ and Tm3+ in the BaY2F8 host matrix were evaluated, their spectroscopic properties were determined, and studies on their temperature-dependent behaviour were carried out. The temperature-sensing properties were studied by generating the fluorescence intensity ratio (FIR) of the UCL peaks originating from the thermally-coupled energy levels of the Tm3+ ions. The Stark sublevels of 1G4 level of Tm3+ ions were utilized to estimate the temperature-sensing abilities of the phosphor.

Biosynthesis of Al2 O3 and europium-doped Al2 O3 nanoparticle using Cymbopogon citratus (lemongrass) extract and its antibacterial property

Cymbopogon citratus-mediated pure aluminium oxide (Al2 O3 ) and europium (Eu)-doped Al2 O3 with different amounts of metal ion were prepared using a green synthesis method. Synthesised nanoparticles were characterised by ultraviolet (UV)-visible spectroscopy, photoluminescence (PL), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Synthesis of nanoparticles is confirmed by using UV-visible spectroscopy showing maximum absorption at 411 and 345 nm for Al2 O3 and Eu-doped Al2 O3 , respectively. The antibacterial activity of prepared nanoparticles was evaluated against Pseudomonas aeruginosa, Streptococcus aureus, Escherichia coli and Klebsiella pneumoniae using a well-diffusion technique. The effect of pure Al2 O3 and Eu-doped nanoparticles shows excellent results against P. aeruginosa, S. aureus, E. coli and K. pneumoniae.

Tailored efficient energy transfer Tb3+, Eu3+ activated/co-activated LiAl(PO3)4 phosphor by substitution of alkali metals: the effect of charge compensation

Phosphites are the new emerging candidates in the field of luminescence in the modern era. In the present investigation, Tb3+/Eu3+ activated/co-activated LiAl(PO3)4 phosphor was prepared by a wet chemical method, and the effect of R+ (Na+, K+) ions on photoluminescence (PL) properties of these phosphors are investigated. Phase identification and crystal structure of the prepared phosphor were determined using XRD and Rietveld refinement, respectively. Morphological study and elemental analysis of the proposed phosphor with elemental analysis of the sample were performed using SEM and EDS. The PL properties of the proposed phosphor showed three simultaneous emission peaks in the visible range, giving color-tunable emission. The charge compensation of Na+ and K+ ions make a significant impact on the PL intensity of Tb3+, Eu3+ co-activated LiAl(PO3)4 phosphors. The PL intensity of Tb3+, Eu3+ co-activated LiAl(PO3)4 phosphors was significantly enhanced by factors 1.2 and 1.4 when Na+ and K+ charge compensators, respectively, were introduced. To manifest the charge compensation effect of alkali metals the optimum intense sample in the co-doped sample was used. These results indicate the potential candidacy of the studied phosphor for further improvement in PL properties for application in solid-state lighting.

Evaluation of the dosimetric influence of interfractional 6D setup error in hypofractionated prostate cancer treated with IMRT and VMAT using daily kV-CBCT

INTRODUCTION

Prostate cancer is one of the most common malignant tumors in men and is usually treated with advanced intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Significant uncorrected interfractional 6-Dimensional setup errors could impact the delivered dose. The aim of this study was to assess the dosimetric impact of 6D interfractional setup errors in hypofractionated prostate cancer using daily kilovoltage cone-beam computed tomography (kV-CBCT).

METHODS

This retrospective study comprised twenty prostate cancer patients treated with hypofractionated IMRT (8) and VMAT (12) with daily kV-CBCT image guidance. Interfraction 6D setup errors along lateral, longitudinal, vertical, pitch, roll, and yaw axes were evaluated for 400 CBCTs. For targets and organs at risk (OARs), the dosimetric impact of rotational error (R_Error), translational error (T_Error), and translational plus rotational error (T+R_Error) were evaluated on kV-CBCT images.

RESULTS

The single fraction maximum T_Error ranged from 12-20 mm, and the R_Error ranged from 2.8⁰-3.0⁰. The maximum mean absolute dose variation ΔD in D_98% (dose to 98% volume) of CTV-55 and PTV-55 was -0.66±0.82 and -5.94±3.8 Gy, respectively, in the T+R_Error. The maximum ΔD (%) for D_98% and D_0.035cc in CTV-55 was -4.29% and 2.49%, respectively, while in PTV-55 it was -24.9% and 2.36%. The mean dose reduction for D_98% in CTV-55 and D_98% and D_95% in PTV-55 was statistically significant (p<0.05) for T_Error and T+R_Error. The mean dose variation for D_mean and D_50% in the rectum was statistically significant (p<0.05) for T_Error and T+R_Error.

CONCLUSION

The uncorrected interfractional 6D setup error results in significant target underdosing and OAR overdosing in prostate cancer. This emphasizes the need to correct interfractional 6D setup errors daily in IMRT and VMAT.

Combustion assisted Ca8.25 Na1.5 Al6 O18 :Sm3+ phosphors for solid state lighting and WLEDs applications

Aluminate based phosphors are most investigated luminescent phosphors over the decades due to its outstanding optical properties. In the proposed work, a series of Sm³⁺ doped Ca_8.25 Na_1.5 Al₆ O₁₈ (CNAO) phosphor sample wasprepared by employing a simple combustion technique with the help of two fuels i.e., urea-glycine. The purity of phase and structural analysis of the CNAO phosphors were confirmed by XRD analysis. Vibrational features of this phosphors confirmed via FT-IR analysis. Photoluminescence study of this phosphor shows doublet emission at 568 and 576 in yellow region attributable to ⁴ G_5/2 →⁶ H_5/2 transition of Sm³⁺ ions while doublet peak noticed in red part ranges in-between 600-620 nm are attributable to ⁴ G_5/2 →⁶ H_7/2 transition of Sm³⁺ ions. Moreover, CIE colour co-ordinates are also located in yellowish red region which confirms the potential of this phosphor as a yellowish red component for WLEDs and display devices applications.

Wet chemical synthesis of BiPO4 : Eu3+ phosphor for W-LED application

The synthesis of BiPO₄ : Eu³⁺ phosphors has been achieved via a wet chemical process. X-ray diffraction patterns show that the phase of as-prepared samples matches very well with the standard BiPO₄ structure. At 395 nm, the highest excitation intensity was observed. Following 395 nm excitation, two characteristic emission peaks at 592 nm and 616 nm were shown. At 0.5 mole percent of Eu³⁺ ions, concentration quenching occurred. The particle size is within the micrometer range, according to the SEM magnification. The chromaticity coordinates for wavelengths 592 nm and 616 nm are (X=0.586, Y=0.412) and (X=0.682, Y=0.317), respectively. The findings imply that prepared phosphor may be used to create white LEDs.

Photoluminescence and Thermoluminescence in Dy3+ , Ce3+ and Tb3+ activated MgB4 O7 phosphor for dosimetry application

Samples of microcrystalline rare earth doped magnesium borate materials were synthesized via. modified solid state diffusion and were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) techniques. Photoluminescence (PL) results of MgB₄ O₇ :Dy sample depicts blue emission resulted from (⁴ F_9/2 -⁶ H_15/2 ) transition peaked at 484 nm, which is much stronger than yellow emission arising due to the (⁴ F_9/2 -⁶ H_13/2 ) at 576 nm. From emission spectra of MgB₄ O₇ :Tb, it looks that, at higher concentration of Tb³⁺ ion, the green emission becomes strong and strong which directly relates the energy transfer from ⁵ D₃ excited state to ⁵ D₄ excited state by a cross-relaxation while blue emission gets suppressed in MgB₄ O₇ phosphors. The TL of the samples was taken immediately after the irradiation and compared the TL curve with CaSO₄ :Dy. MgB₄ O₇ :Dy showed very good TL sensitivity for the desirable dosimetric curve at about 218°C and the best glow curve structure. In comparison to dosimetric peak of MgB₄ O₇ :Ce and MgB₄ O₇ :Tb, MgB₄ O₇ :Dy phosphor is equally sensitive to CaSO₄ : Dy. MgB₄ O₇ :Dy and MgB₄ O₇ :Tb have shown linearity for 1-5 kGy dose. The activation energies and frequency factors are also calculated for samples MgB₄ O₇ :RE (RE=Dy, Tb, Ce) using peak shape method.

Review on long afterglow nanophosphors, their mechanism and its application in round-the-clock working photocatalysis

Semiconductor assisted photocatalysis is one of the most efficient methods for the degradation of complex organic dyes. A major limiting factor of semiconductor assisted photocatalysis is the requirement of a continuous source of light to perform a redox reaction. One of the upcoming solutions is photon energy-storing long afterglow/persistent phosphors. They are an unusual kind of rechargeable, photon energy capturing/trapping phosphors that can trap charge carriers (electrons/holes) in their meta-stable energy levels, thereby resulting in persistent luminescence. Persistence luminescence from such materials can range from minutes to hours. The coupling of long afterglow phosphors (LAP) with the conventional semiconductor is a promising way to support the photocatalytic process even in dark. In addition, dissimilar band structures of LAPs and semiconductor results in formation of heterojunction which further suppresses the recombination of charge. Such an encouraging idea of LAP for round-the-clock working photocatalytic system is in its premature stage; which is required to be investigated fully. Thus, we present a state-of-art review on the potential materials for assisting round-the-clock photocatalysis, trapping-detrapping mechanism in LAP materials, fabrication strategies and their associated characterization tools. Review also covers LAP materials and their photocatalytic mechanism briefly.

Persistent phosphors for luminous paints: A review

The paper briefly reports the fundamental scientific principles and landmarks in the field of luminescence and further enlightens the importance of persistent phosphor that is now widely used in luminous paints. Its main focus is on phosphorescence that makes use of lanthanides that have gained paramount importance in various cross-sections of luminescent applications.. Both inorganic and organic afterglow materials, synthesis and characterization along with skilled researchers' essential updates on emerging trends and efforts are elucidated at length. It exclusively reviews the red/green/blue organic/inorganic/hybrid phosphorescent materials and the latest advances in the development of novel long afterglow materials that can accelerate the green technology in the world of luminescence.

Study on luminescence properties of Ce3+ and Eu3+ ions in nanocrystalline hexagonal Zn4 Al22 O37 novel system

The present communication is strongly focused on an investigation of synthesis, structural and luminescence properties of cerium (Ce³⁺ ) and europium (Eu³⁺ ) activated Zn₄ Al₂₂ O₃₇ phosphors. We have prepared Ce³⁺ and Eu³⁺ doped Zn₄ Al₂₂ O₃₇ novel phosphors by using solution combustion synthesis route. The structural properties have been studied by using powder x-ray diffraction (XRD) and high resolution transverse electron microscope (HR-TEM). The optical properties are studied by using ultraviolet visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR) and luminescence properties are studied using photoluminescence technique (PL). The crystal structure of the prepared Zn₄ Al₂₂ O₃₇ host and Ce³⁺ and Eu³⁺ activated Zn₄ Al₂₂ O₃₇ phosphors have been investigated and these have found a hexagonal structure. The measured PL emission spectrum of Ce³⁺ doped Zn₄ Al₂₂ O₃₇ phosphor shows an intense and broad emission band centered at 421 nm under the 298 nm excitation wavelength. Whereas, the Eu³⁺ doped Zn₄ Al₂₂ O₃₇ phosphor exhibits two strong and intense emission bands around 594 nm (orange) and 614 nm (red), monitored under 395 nm excitation. The CIE color coordinates of the Ce³⁺ doped Zn₄ Al₂₂ O₃₇ have been investigated as x=0.1567, y=0.0637 (blue) at 421 nm and Eu³⁺ doped Zn₄ Al₂₂ O₃₇ as x= 0.6018, y= 0.3976 (orange) at 594 nm and x= 0.6779, y= 0.3219 (red) at 614 nm emissions. The luminescence behavior of the synthesized phosphors suggested that these phosphors may be applicable in lighting applications.

Novel red color emitting Ca0.995 Mg2 (SO4 )3 :0.5Eu2+ phosphor under UV, blue and green excitation for plant growth LEDs

In the recent few years, Eu²⁺ and Mn⁴⁺ activated phosphors are widely used as potential color converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we are synthesized novel red color emitting Ca_(2-x) Mg₂ (SO₄ )₃ : xmol% Eu²⁺ (x = 0-1.0 mol%) phosphors via solid-state reaction method in reducing atmosphere. The PL excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm and 554 nm. Under these excitations, emission spectra exhibits broad band in the red color region around 634 nm. The PL emission intensity were measured for different concentration of Eu²⁺ . The maximum Eu²⁺ doping concentration in Ca₂ Mg₂ (SO₄ )₃ host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole-dipole interaction is responsible for concentration quenching. The luminous red color emission of the sample was confirmed by CIE color coordinate. The results of PL excitation and emission spectrum of prepared phosphors are well-matched with excitation and emission wavelengths of phytochrome P_R . Therefore, as per the entire investigation and obtained results it was concluded that the synthesized Ca_0.995 Mg₂ (SO₄ )₃ :0.5mol%Eu²⁺ phosphor has huge potential for plant cultivation application.

Tailoring of thermoluminescent properties and assessment of trapping parameters of natural fluorite samples from Dogargaon fluorite mines, India

Mineral fluorite or fluorspar (CaF₂ ) can host significant quantities of trivalent REE³⁺ (rare earth element) by substitution with divalent Ca²⁺ . The fluorites associated with carbonatites are often REE-rich compared to those derived from sedimentary, hydrothermal, or Mississippi Valley-type (MVT) fluorites. The naturally occurring fluorites have several industrial applications one of which is for luminescence. Whether or not REE enriched, the fluorite makes an ideal host for REEs, which are very important phosphors. The naturally occurring fluorites are available in sufficient quantities to cater to the industrial demand. Investigations have been carried out on the fluorites from active fluorite mines at Dongargaon in central India. Thermoluminescence behavior of a natural fluorite sample was investigated using a Nucleonix TL 1009I thermoluminescence reader. Multiple traps formed in the broad thermoluminescent (TL) glow curve were found by TL anal deconvolution software. Trapping parameters for all multiple traps formed on deconvoluting broad TL glow curve were found by different methods like Initial rise method, Chen's Peak shape method and Ilich method.

Photoluminescence studies and synthesis of BaSO3 Cl2 :Ce3+ blue-emitting lamp phosphor

The photoluminescence excitation and emission spectra of BaSO₃ Cl₂ :Ce³⁺ phosphor were investigated. Excitation wavelength was 323 nm. The phosphor was prepared using a combustion synthesis method. The emission spectrum exhibited a well defined asymmetric band with a maximum at 445 nm for higher emission concentrations. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence and Commission Internationale de l'éclairage colour coordinates; emission intensity was related to relative Ce³⁺ concentration. These developments enabled the rapid and energy-efficient production of fine particles in the powder form with little expenditure. No additional emission band was observed in the emission spectra, demonstrating that the Ce³⁺ ion occupied one category of site in the prepared host phosphor.

Investigations on optical properties of Eu0.5 Sm0.5 (TTA)3 tppo hybrid organic complexes molecularly doped in PMMA and PS matrices

An attempt has been made to synthesize orange-red light-emitting rare earth-doped polymer matrices Eu_0.5 Sm_0.5 (TTA)₃ tppo (Eu = europium, Sm = samarium, TTA = thenoyltrifluoroacetone, tppo = triphenylphosphine oxide) hybrid organic complex by solution technique. Blended thin films were made by molecularly doping the complex in polymethylmethacrylate (PMMA) and polystyrene (PS) polymers at different weight percentages (5%, 10%). These films were solvated in basic and acidic media to explore the effect of solvent on its luminescence properties. UV-visible absorption spectra of these solvated films portray two peaks corresponding to π→π* and n→π* optical transitions in the range 240-275 nm and 370-390 nm in basic medium. Energy band gap of these thin films in basic medium was found between 3.16 eV to 3.20 eV and 3.12 eV to 3.22 eV in acidic medium. Photoluminescence spectra of all films in dichloromethane showed an intense peak at 614 nm, whereas in formic acid, the same were found at 475 nm, which fell in the orange-red and blue region of the visible spectrum, respectively. CIE coordinates of these solvated films in various solvents and at different weight percentages revealed tunable orange-red to blue light emission with change in polarity of the solvent. Therefore the synthesized complexes blended in the polymers can be shaped into flexible films for fabrication of organic light-emitting diodes (OLEDs) with consistent results, proving their prospect as colour tunable light emissive materials for OLED devices, lasers, displays, and solid-state lighting.

Thermoluminescence study in fossils of dinosaur bones and eggshells

In this study, thermoluminescence (TL) characterization of fossils of sauropod dinosaur bone, dinosaur eggshells, and associated sediments were recorded for the first time. The fossil bone was collected from the Bagwanya intertrappean sediments in the Dhar district of Madhya Pradesh, India. TL was recorded using ⁶⁰ Co gamma ray exposure at different doses. Fossils of dinosaur bone, dinosaur eggshells, and associated sediments were irradiated using ⁶⁰ Co gamma rays at different doses from 0.15 kGy to 19 kGy. The linear dose-response curve of the irradiated sample was obtained for a dose ranging from 0.15 kGy to 9.5 kGy. These geological samples were characterized further using X-ray diffraction for confirmation with phase, scanning electron microscopy, Fourier transform infrared spectroscopy, and wavelength dispersive-X-ray fluorescence for determination of the elemental composition in parts per million to percentage levels.

Thermoluminescence dosimetry properties and kinetic analysis of K3 Ca2 (SO4 )3 F:Dy3+ phosphor

A trivalent Dy³⁺ -activated K₃ Ca₂ (SO₄ )₃ F fluoride-based phosphor was synthesized using a solid-state reaction method and characterized for its thermoluminescence (TL) application. The crystal structure and surface morphology of the as-synthesized material was analyzed using X-ray diffraction and scanning electron microscopy. A series of the K₃ Ca₂ (SO₄ )₃ F:Dy³⁺ phosphor was irradiated using γ-rays from a ⁶⁰ Co source and TL glow curves were recorded using a Nucleonix 1009I TL reader. The glow curve of the prepared phosphor showed a prominent single peak at 278°C. TL characteristics were maximum intensity at 1 mol% of Dy³⁺ ion with a single TL glow peak. The TL glow curve revealed linearity with increase in exposure dose range from 0.1 kGy to 3.0 kGy. Theoretical analysis of the TL glow curve of the γ-ray-irradiated sample was carried out using a computerized glow curve deconvolution method and trapping parameters such as activation energy and frequency factor were calculated using the initial rise method and Ilich's method. The synthesized Dy³⁺ -doped K₃ Ca₂ (SO₄ )₃ phosphor revealed excellent TL properties and was found to be a potential candidate for dosimetric applications.

Thermoluminescence study of CaNa2 (SO4 )2 phosphor doped with Eu3+ and synthesized by combustion method

In the present study, the thermoluminescence (TL) properties of an Eu³⁺ -doped CaNa₂ (SO₄ )₂ phosphor were studied. The Eu³⁺ -doped CaNa₂ (SO₄ )₂ phosphor was synthesized using the combustion method. The samples were well crystallized in the monoclinic phase. The TL glow curve of the Eu³⁺ -doped CaNa₂ (SO₄ )₂ phosphor showed a single prominent peak at around 210°C with showed linearity on increasing exposure. The response curve of the synthesized phosphor showed linearity in the range 500-7000 Gy. Trapping parameters of synthesized phosphors such as activation energy, frequency factor, and order of kinetics were calculated in the study. These trapping parameters were determined by different methods such as Chen's peak method, the initial rise method, and Ilich's method. Each characteristic of these outcomes demonstrated that the synthesized Eu³⁺ -doped CaNa₂ (SO₄ )₂ phosphor had outstanding TL properties and might be valuable for TL dosimetry application.

Synthesis and luminescence characterization of Eu3+ -doped Ca7 Mg2 (PO4 )6 phosphor for eco-friendly white light-emitting diodes and thermoluminescence dosimetric applications

A Eu³⁺ -activated Ca₇ Mg₂ (PO₄ )₆ phosphor was prepared at high temperature (800°C) using a solid-state reaction method. The crystal structure, phase formation of the prepared phosphor was characterized using X-ray diffraction patterns and Fourier transformed infrared analysis. The luminescence properties of the synthesized phosphor were characterized using photoluminescence and thermoluminescence techniques. The prepared phosphor showed two emission peaks at 594 nm with an orange colour due to the ⁵ D₀ →⁷ F₁ transition and at 612 nm a red colour due to the ⁵ D₀ →⁷ F₂ transition under 396 nm near-UV excitation. The prepared phosphors were irradiated with different doses of γ-rays from a ⁶⁰ Co gamma irradiation source. Thermoluminescence glow curves for this sample phosphor were obtained using a Nucleonix 1009I TL reader. Synthesized phosphor samples were exposed to a 3.6 kGy dose of γ-rays. The thermoluminescence glow curve of the Ca₇ Mg₂ (PO₄ )₆ :0.05 mol%Eu³⁺ phosphor showed maximum intensity at all concentrations of Eu³⁺ ions. The Ca₇ Mg₂ (PO₄ )₆ :0.05 mol%Eu³⁺ phosphor was irradiated with different doses of ⁶⁰ Co γ-irradiation and a linear response was observed between 0.6 kGy and 3.6 kGy. Trapping parameters such as activation energy, frequency factor and order of kinetics were calculated. The CIE chromaticity diagram showed the colour coordinates of the synthesized phosphor in the orange and red regions of the visible spectrum; this spectral feature revealed high colour purity and excellent chromaticity coordinate characteristics. Photoluminescence and thermoluminescence properties revealed that the prepared phosphor could be a potential red-emitting phosphor for eco-friendly white light generation and an excellent thermoluminescent dosimeter material for thermoluminescence dosimetric applications.

Carbon Quantum Dots/Polyaniline Nanocomposite (S-CQD/PANI) for High Capacitive Asymmetric Supercapacitor Device

A sucrose derived carbon quantum dots/polyaniline (S-CQD/PANI) nanocomposite was synthesized as electrode materials by electrodeposition method to achieve excellent electrocapacitive performance for supercapacitor application. The morphology reveals that CQD were distributed uniformly over the surface of PANI. The highest specific capacitance obtained to be 1512.4 Fg^-1 at current density 1 Ag^-1 for S-CQD/PANI-25 composite in three electrode system with 1 M H₂SO₄ aqueous electrolyte within the potential range of -0.2 to 0.8 V. In addition asymmetric supercapacitor device was fabricated reveals highest specific capacitance of 295 Fg^-1 at 1 Ag^-1 with excellent stability over 1000 cycle at 3 Ag^-1. Remarkably, the device delivers energy density of 40.86 Whkg^-1 at power density 2000 Wkg^-1.

Luminescence characterization of KBaPO4 :RE (RE = Sm3+ ,Eu3+ ,Dy3+ ) phosphors

KBaPO₄ luminescent powdered phosphors doped with rare earth elements (RE = Sm³⁺ ,Eu³⁺ ,Dy³⁺ ) were successfully synthesized using a wet chemical method to identify the most suitable phosphor for solid-state lighting based on the measurement of their emission spectra at excitation wavelengths. The X-ray diffraction pattern of the as-prepared KBaPO₄ was well matched with its standard JCPDS file no. 330996, indicating the formation of the desired compound. Scanning electron microscopy images revealed irregular morphology, the material crystallized particles aggregated and were non-uniform with particle sizes ranging from 1 to 100 μm. Photoluminescence excitation and emission spectra clearly indicated that the phosphor containing the Sm³⁺ -activated KBaPO₄ phosphors could be efficiently excited at 403 nm and exhibited an emission mainly including two wavelength peaks at 559 nm and 597 nm. The phosphor containing the Eu³⁺ -activated KBaPO₄ phosphors could be efficiently excited at 396 nm and exhibited a bright red emission mainly including two wavelength peaks at 594 nm and 617 nm. The phosphor containing the Dy³⁺ -activated KBaPO₄ phosphors could be efficiently excited at 349 nm and exhibited wavelength peaks at 474 nm and 570 nm.

Correction and removal of expression of concern: A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca2Al2SiO7:Dy3+ phosphors fabricated using a combustion-assisted method

Correction and removal of expression of concern for ‘A study on the luminescence properties of gamma-ray-irradiated white light emitting Ca₂Al₂SiO₇:Dy³⁺ phosphors fabricated using a combustion-assisted method’ by Geetanjali Tiwari et al., RSC Adv., 2016, 6, 49317–49327.

Synthesis and photoluminescence properties of Eu3+ -activated Ba2 Mg(PO4 )2 phosphor

In this paper, we have reported the photoluminescence (PL) properties of the Ba₂ Mg(PO₄ )₂ :Eu³⁺ phosphor synthesized using a wet chemical method. The preliminary scanning electron microscopy (SEM) investigation of the sample revealed irregular surface morphology with particle sizes in the 10-50 μm range. The strongest PL excitation peak was observed at 396 nm. The emission spectra indicated that this phosphor can be effectively excited by the 396 nm wavelength. Upon 396 nm excitation, the emission spectrum showed characteristics peaks located at 592 nm and 615 nm. These intense orange-red emission peaks were obtained due to f→f transitions of Eu³⁺ ions. The emission peak at 592 nm is referred to as the magnetic dipole ⁵ D₀ →⁷ F₁ transition and the emission peak at 615 nm corresponded to the electric dipole ⁵ D₀ →⁷ F₂ transition of Eu³⁺ . The Commission Internationale de l'Eclairage (CIE) coordinates of the Ba₂ Mg(PO₄ )₂ :Eu³⁺ phosphor were found to be (0.586, 0.412) for wavelength 592 nm and (0.680, 0.319) for wavelength 615 nm situated at the edge of the CIE diagram, indicating high colour purity of phosphors. Due to the high emission intensity and a good excitation profile, Eu³⁺ -doped Ba₂ Mg(PO₄ )₂ phosphor may be a promising orange-red phosphor candidate for solid-state lighting applications.

Luminescence study of LiMgBO3 :Dy for γ-ray and carbon ion beam exposure

LiMgBO₃ :Dy³⁺ , a low Z_eff material was prepared using the solution combustion method and its luminescence properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), photoluminescence (PL), Fourier transform infrared spectroscopy, and electron paramagnetic resonance (EPR) techniques. Reitvield refinement was also performed for the structural studies. The PL emission spectra for LiMgBO₃ :Dy³⁺ consisted of two peaks at 478 due to the ⁴ F_9/2 →⁶ H_15/2 magnetic dipole transition and at 572 nm due to the hypersensitive ⁴ F_9/2 →⁶ H_13/2 electric dipole transition of Dy³⁺ , respectively. A TL study was carried out for both the γ-ray-irradiated sample and the C⁵⁺ irradiated samples and was found to show high sensitivity for both. Moreover the γ-ray-irradiated LiMgBO₃ :Dy³⁺ sample showed linearity in the dose range 10 Gy to 1 kGy and C⁵⁺ -irradiated samples show linearity in the fluence range 2 × 10¹⁰ to 1 × 10¹¹ ions/cm² . In the present study, the initial rise method, various heating rate method, the whole glow curve method, glow curve convolution deconvolution function, and Chen's peak shape method were used to calculate kinetic parameters to understand the TL glow curve mechanism in detail. Finally, an EPR study was performed to examine the radicals responsible for the TL process.

Study of luminescence properties of dysprosium-doped CaAl12 O19 phosphor for white light-emitting diodes

Dy³⁺ -doped CaAl₁₂ O₁₉ phosphors were synthesized utilizing a combustion method. Crystal structure and morphological examinations were performed respectively using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to identify the phase and morphology of the synthesized samples. Fourier transform infrared spectroscopy (FTIR) estimations were carried out using the KBr method. Photoluminescence properties (excitation and emission) were recorded at room temperature. CaAl₁₂ O₁₉ :Dy³⁺ phosphor showed two emission peaks respectively under a 350-nm excitation wavelength, centered at 477 nm and 573 nm. Dipole-dipole interaction via nonradiative energy shifting has been considered as the major cause of concentration quenching when Dy³⁺ concentration was more than 3 mol%. The CIE chromaticity coordinates positioned at (0.3185, 0.3580) for the CaAl₁₂ O₁₉ :0.03Dy³⁺ phosphor had a correlated color temperature (CCT) of 6057 K, which is situated in the cool white area. Existing results point out that the CaAl₁₂ O₁₉ :0.03Dy³⁺ phosphor could be a favorable candidate for use in white light-emitting diodes (WLEDs).

Versatility of thermoluminescence materials and radiation dosimetry - A review

Thermoluminescence (TL) materials exhibit a wide range of applications in different areas such as personal dosimetry, environmental dosimetry, medical research etc. Doping of different rare earth impurities in different hosts is responsible for changing the properties of materials useful for various applications in different fields. These materials can be irradiated by different types of beams such as γ-rays, X-rays, electrons, neutrons etc. Various radiation regimes, as well as their dose-response range, play an important role in thermoluminescence dosimetry. Several TL materials, such as glass, microcrystalline, nanostructured inorganic materials and recently developed materials, are reviewed and described in this article.

Alteration of the electronic structure and the optical properties of graphitic carbon nitride by metal ion doping

The photoluminescence quenching of graphitic carbon nitride (GCN) was systematically investigated with the doping of transition metal ions. The photoluminescence spectra of metal doped and pristine GCN were monitored and the trend of quenching efficiency was found to be Cu²⁺ > Co²⁺ > Mn²⁺. Interestingly, with the increasing doping concentration of different metal ions simultaneous red shift and luminescence quenching was determined in the photoluminescence spectra as well as increased absorption tail in longer wavelength hence enhancement in the bandgap. The change in the optical properties could be mainly due to structural reconstruction and doping induced electronic redistribution is discussed.

Synthesis and characterization of a green-light-emitting (pbi-Br)2 Ir (acac) metal complex for OLEDs

We designed and synthesized a 2-(4-bromophenyl)-1-phenyl-1H-benzimidazole (pbi-Br) ligand, which was then employed to create an innovative phosphorescent cyclometallated iridium(III) (pbi-Br)₂ Ir(acac) metal complex with acetyl acetone as an ancillary ligand using the Suzuki coupling reaction. The complex was then characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra and thermogravimetric analysis (TGA)/differential thermal analysis (DTA) for structural and thermal analysis, respectively. XRD confirmed its amorphous nature and the FTIR spectrum revealed the molecular structure confirmation of the metal complex. The TGA/DTA curve disclosed its thermal stability up to 310°C. Ultraviolet (UV)-vis absorption and photoluminescence (PL) spectra were measured to explore the photo-physical properties of the (pbi-Br)₂ Ir(acac) complex in basic and acidic media respectively. With the variation in solvent from acidic to basic media, optical absorption peaks blue shifted with variation in optical densities. These results facilitated the calculation of various photo-physical parameters. When excited at 379 nm in the solid state, the synthesized complex gave out a green light emission, peaking at λ_emi  = 552 nm. Staggering differences in optical density were observed in the PL spectra of the solvated complex. A Stokes' shift of 7140.45 cm^-1 and 7364.94 cm^-1 was observed when the complex was solvated in acetic acid and chloroform, respectively. Hence the synthesized iridium metal complex can be considered as promising green emissive material for optoelectronic applications.

Recent advances and developments on integrating nanotechnology with chemiluminescence assays

Chemiluminescence (CL) techniques are extensively utilized for detection of analytes due to their high sensitivity, rapidity and selectivity. With the advent of nanotechnology and incorporation of the nanoparticles in the CL system has revolutionized the assays due to their unique optical and mechanical properties. Several CL-based reactions have been developed where these nanoparticle based CL sensors have evolved as excellent prospects for sensing in various analytical applications. This review article addresses the nanoparticles based CL detection system that are recently developed, the mechanisms has been summarized and the role of luminophors have been discussed. This article critically analyzes the optimal conditions for the CL detection along with quantitative assessment of the analytes. We have included the use of semiconductor nanoparticles, metal nanoparticles, graphene based nanostructures, mesoporous nanospheres, layered double hydroxides, clays for CL detection. The scope and application of these nanoscale material based CL system in various branches of science and technology including chemistry, biomedical applications, pharmaceutics, food, environmental and toxicological applications has been critically summarized.

Synthesis and characterization of high quantum yield and oscillator strength 6-chloro-2-(4-cynophenyl)-4-phenyl quinoline (cl-CN-DPQ) organic phosphor for solid-state lighting

A novel blue luminescent 6-chloro-2-(4-cynophenyl) substituted diphenyl quinoline (Cl-CN DPQ) organic phosphor has been synthesized by the acid-catalyzed Friedlander reaction and then characterized to confirm structural, optical and thermal properties. Structural properties of Cl-CN-DPQ were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) spectroscopy. FTIR spectra confirmed the presence of different functional groups and bond stretching. ¹ H-NMR and ¹³ C-NMR confirmed the formation of an organic Cl-CN-DPQ compound. X-ray diffraction study provided its crystalline nature. The surface morphology of Cl-CN-DPQ was analyzed by SEM, while EDAX spectroscopy revealed the elemental analysis. Differential thermal analysis (TGA/DTA) disclosed its thermal stability up to 250°C. The optical properties of Cl-CN-DPQ were investigated by UV-vis absorption and photoluminescence (PL) measurements. Cl-CN-DPQ exhibits intense blue emission at 434 nm in a solid-state crystalline powder with CIE co-ordinates (0.157, 0.027), when excited at 373 nm. Cl-CN-DPQ shows remarkable Stokes shift in the range 14800-5100 cm^-1 , which is the characteristic feature of intense light emission. A narrow full width at half-maximum (FWHM) value of PL spectra in the range 42-48 nm was observed. Oscillator strength, energy band gap, quantum yield, and fluorescence energy yield were also examined using UV-vis absorption and photoluminescence spectra. These results prove its applications towards developing organic luminescence devices and displays, organic phosphor-based solar cells and displays, organic lasers, chemical sensors and many more.

Influence of Li+ charge compensator ion on the energy transfer from Pr3+ to Gd3+ ions in Ca9Mg(PO4)6F2:Gd3+, Pr3+, Li+ phosphor

Phototherapy is a renowned treatment for curing skin diseases since ancient times. Phototherapeutic treatment for psoriasis and many other diseases require narrow band ultra violet-B (NB-UVB) light with peak intensity at 313nm to be exposed to the affected part of body. In this paper, we report combustion synthesis of NB-UVB -313nm emitting Ca₉Mg(PO₄)₆F₂ phosphors doped with Gd³⁺, Pr³⁺ and Li⁺ ions. The phase formation was confirmed by obtaining X-ray diffraction (XRD) pattern and morphology was studied with the Scanning electron microscopy (SEM) images. Photoluminescence (PL) emission spectra show intense narrow band emission at 313nm under 274nm excitation wavelengths. Emission intensity was enhanced when Ca₉Mg(PO₄)₆F₂ compound is co-doped with Pr³⁺ ions. Excitation spectra of Ca₉Mg(PO₄)₆F₂:Gd³⁺, Pr³⁺ doped samples shows broad excitation in ultra violet C (UVC) region. Diffuse reflectance spectra (DRS), obtained by UV-visible spectrophotometer, measures the absorption properties of the material. By applying Kubelka Munk function on the diffuse reflectance spectra, band gap of the material is determined. PL decay curves were examined which indicates efficient energy transfer between Pr³⁺ and Gd³⁺ ions. Charge compensation effect was also studied by co-doping Li⁺ ion in host. Emission intensity was found to increase with the addition of charge compensator. The prepared phosphor has potential to convert UVC light into NB-UVB. The luminescence intensity of Gd³⁺ shows remarkable increase when it is sensitized with Pr³⁺, and an addition of charge compensator in the form of Li⁺, show even better results. This phosphor surely has the potential to be used as phototherapy lamp phosphor.

Dy3+ -, Sm3+ -, Ce3+ - and Tb3+ -activated optical properties of microcrystalline BaMgP2 O7 phosphors

Photoluminescence (PL) and thermoluminescence (TL) properties of rare earth (RE) ion (RE = Dy³⁺ , Sm³⁺ , Ce³⁺ , Tb³⁺ ) activated microcrystalline BaMgP₂ O₇ phosphors are presented in this work. Non-doped and doped samples of BaMgP₂ O₇ were prepared using a solid state diffusion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), PL and TL. The XRD measurement confirmed the phase purity of the BaMgP₂ O₇ host matrix. The average particle size was found through SEM measurement to be around 2 μm. All activators using the PL technique displayed characteristic excitation and emission spectra that corresponded to their typical f → f and f → d transitions respectively. Thermoluminescence measurements showed that BaMgP₂ O₇ :RE (RE = Dy³⁺ , Sm³⁺ , Tb³⁺ , Ce³⁺ ) and co-doped BaMgP₂ O₇ :Ce³⁺ ,Tb³⁺ phosphors have also TL behaviour.

Phosphor for phototherapy: Review on psoriasis

We review developments in the field of phototherapy in terms of the treatment wavelength, dosimetry and phosphor used for different dermatoses. We attempt to categorize skin lesions and diseases by morphology, focusing on conditions that can be treated using phototherapy and photochemotherapy. Recent research and review articles are studied, the treatments explained and information on phototherapy that is applicable to psoriasis and other diseases is tabulated. The clinical features, epidemiology, epitalogy and various types of psoriasis, together with the therapies available to treat them are reported. Needs-based research has been carried out on narrow and broad band UVB wavelength-emitting phosphors and psoralen combined with UVA (PUVA) depending upon the disease undergoing treatment. Somewhat detailed descriptions of the different types of therapies used in the treatment of psoriasis are given. Phototherapy is shown to be a good therapeutic option for various types of skin diseases. The use of natural therapy has diminished as more people move towards artificial phototherapy like narrow band UVB, broad band UVB, PUVA and targeted phototherapy. The main advantages of these treatments are that they are safe and reduce erythema following treatment. Regarding safety issue the targated phototherapy pay more attention towards researcher.

Assessment of electron-vibrational interaction (EVI) parameters of YAG:Ce3+, TAG:Ce3+ and LuAG:Ce3+ garnet phosphors by spectrum fitting method

The electron-vibrational interaction (EVI) in 4f↔5d optical transitions of Ce³⁺ ions in YAG, TAG and LuAG garnet phosphors have been analysed in this work. The main EVI parameters that have been estimated and reported here are Huang-Rhys factor, effective phonon energy, Stokes shift, red shift and Zero-phonon line position. The EVI parameters were estimated from the room temperature photoluminescence results that were recently reported. The spectrum fitting method was employed to determine the EVI parameters. An emission band was modelled with the aid of the calculated EVI parameters. The agreement between the modelled emission bands with the experimentally obtained ones validated the estimated values of EVI parameters.

Visible upconversion in Er3+/Yb3+ co-doped LaAlO3 phosphors

The Er³⁺ doped and Er³⁺/Yb³⁺ co-doped LaAlO₃ phosphors have been synthesized by the combustion method and characterized their structural, morphological, elemental, vibrational and optical properties. The optical absorption and upconversion properties of the synthesized phosphors have been studied. Upon co-doping Yb³⁺ ions into Er³⁺:LaAlO₃, the blue, green and red upconversion emissions of Er³⁺ ions have been enhanced about ~20, ~54 and ~22 times, under 978nm laser excitation. The observed upconversion emissions could be due to excited state absorption in Er³⁺:LaAlO_3, whereas energy transfer is dominant mechanism in Er³⁺/Yb³⁺:LaAlO₃ phosphors. The tuning in the color emitted from the synthesized phosphors towards the green region has been found due to incorporation of the Yb³⁺ ions. With increase in the pump power, the color emitted from the co-doped phosphor is not tuned significantly, showing its applicability in making the green display devices.

Photoluminescence and thermoluminescence of K2 Mg(SO4 )2 :Eu and evaluation of its kinetic parameters

The K₂ Mg(SO₄ )₂ :Eu phosphor, synthesized by a solid-state diffusion method, was studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. The X-ray diffraction (XRD) pattern of the material was matched with the standard JCPDF No. 36-1499. For PL characteristics, K₂ Mg(SO₄ )₂ :Eu²⁺ showed an emission peak at 474 nm when excited at 340 nm, while it showed Eu³⁺ emission at 580 nm, and 594 nm splitting at 613 nm and 618 nm for an excitation of 396 nm wavelength due to radiative transitions from ⁵ D₀ to ⁷ F_j (j = 0, 1, 2, 3). The Commission International de I' Eclairage (CIE) chromaticity coordinates were also calculated for the K₂ Mg(SO₄ )₂ :Eu phosphor, and were close to the NTSC standard values. For the TL study, the prepared sample was irradiated using a ⁶⁰ Co source of γ-irradiation at the dose rate of 0.322 kGy/h for 2 min. The formation of traps in K₂ Mg (SO₄ )₂ :Eu and the effects of γ-radiation dose on the glow curve are discussed. Well defined broad glow peaks were obtained at 186°C. With increasing γ-ray dose, the sample showed linearity in intensity. The presence of a single glow peak indicated that there was only one set of traps being activated within the particular temperature range. The presented phosphors were also studied for their fading, reusability and trapping parameters. There was just 2% fading during a period of 30 days, indicating no serious fading problem. Kinetic parameters were calculated using the initial rise method and Chen's half-width method. Activation energy and frequency factor were found to be 0.77 eV and 1.41 × 10⁶  sec^-1 .

Luminescence characterization of Dy and Eu doped Na6 Mg(SO4 )4 phosphors

A series of single-phase phosphors based on Na₆ Mg(SO₄ )₄ (Z_eff  = 11.70) doped with Dy and Eu was prepared by the wet chemical method. The photoluminescence (PL) and thermoluminescence (TL) properties of Dy³⁺ - and Eu³⁺ -activated Na₆ Mg(SO₄ )₄ phosphors were investigated. The characteristic emissions of Dy³⁺ and Eu³⁺ were observed in the Na₆ Mg(SO₄ )₄ host. The TL glow curve of the Na₆ Mg(SO₄ )₄ :Dy phosphor consisted of a prominent peak at 234°C and a very small hump at 158°C. The TL sensitivity of the Na₆ Mg(SO₄ )₄ :Dy phosphor was found to be four times less than the commercialized CaSO₄ :Dy phosphor. The TL dose-response of the Na₆ Mg(SO₄ )₄ :Dy phosphor was studied from a dose range of 5-10 kGy and the linear dose-response was observed up to 1 kGy which is good for a microcrystalline phosphor. Trapping parameters for both the samples were calculated using the Initial Rise and Chen's peak shape methods.

Resonant and non-resonant energy transfer from Ce3+ → X (X = Tb3+ , Eu3+ or Dy3+ ) in NaMgSO4 F material

An inorganic NaMgSO₄ F fluoride material was prepared by the wet chemical method and studied for its photoluminescence (PL) and resonant-non-resonant energy transfer (RET and NORET) capabilities between Ce³⁺  → Tb³⁺ , Ce³⁺  → Eu³⁺ and Ce³⁺  → Dy³⁺ rare earth ions. The Tb³⁺ emission for Ce³⁺  → Tb³⁺ transfers under ultraviolet (UV) wavelengths peaked at 491, 547, and 586 nm, for excitation at 308 nm due to ⁵ D₄  → ⁷ F_J (J = 4, 5, 6) transitions. Eu emission spectra were observed at 440 nm (Eu²⁺ ), 593 nm and 616 nm (Eu³⁺ ) recorded for different concentrations of materials, whereas Dy³⁺ emission from Ce³⁺  → Dy³⁺ transfer under UV wavelengths peaked at 485 nm and 577 nm due to ⁴ F_9/2  → ⁶ H_15/2 and ⁶ H_13/2 transitions. The purpose of the present study is to understand the RET and NORET effects of Tb³⁺ , Eu³⁺ and Dy³⁺ co-doping in a NaMgSO₄ F:Ce³⁺ luminescent material, which could be used as a green-emitting material for lamp phosphors.

Luminescence analysis of SrGa2 Si2 O8 : RE3+ (RE = Dy, Tm) phosphors

This article reports on the luminescence properties of rare earth (Dy³⁺ and Tm³⁺ )ions doped SrGa₂ Si₂ O₈ phosphor were studied. SrGa₂ Si₂ O₈ phosphors weresynthesizedby employing solid state reaction method.From the measured X-ray diffraction (XRD) pattern of the samplemonoclinic phase structure has been observed. Thermoluminescenceand Mechanoluminescence properties of the γ-ray irradiated samples have been studied. Photoluminescence spectra of Dy³⁺ activated SrGa₂ Si₂ O₈ phosphor has been measured with an excitation wavelength at 348 nm,and it shows two emission bands at 483 and 574 nm due to ⁴ F_9/2  → ⁶ H_15/2 and ⁴ F_9/2  → ⁶ H_13/2 transitions respectively. Whereas the photoluminescence spectra of Tm³⁺ activated SrGa₂ Si₂ O₈ phosphor has been measured with an excitation wavelength at 359 nm and it exhibits two emission bands at 454 and 472 nm due to ¹ D₂  → ³ F₄ and¹ G₄  → ³ H₆ transitions respectively. In thermoluminescence study, γ-irradiatedthermoluminescence glow curve of SrGa₂ Si₂ O₈ :Dy³⁺ phosphor shows two well defined peaks at 293 °C (peak1)and 170 °C (peak2) whereas thermoluminescence glow curve of SrGa₂ Si₂ O₈ :Tm³⁺ phosphor shows peaks at 292 °C (peak1) and 184 °C (peak2) indicating that two sets of traps are being activated within the particular temperature range and the trapping parameters associated with the prominent glow peaks of SrGa₂ Si₂ O₈ :Dy³⁺ and SrGa₂ Si₂ O₈ :Tm³⁺ are calculated using Chen's peak shape and initial rise method.From the Mechanoluminescence study, only one glow peak has been observed. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis and characterization of novel Na15 (SO4 )5 F4 Cl:Ce3+ halosulfate phosphors

A series of Na₁₅ (SO₄ )₅ F₄ Cl phosphors doped with Ce³⁺ ions was prepared using the wet chemical method. X-Ray diffraction studies were used to determine their phase formation and purity. Fourier transform infrared spectroscopy effectively identified the chemical bonds present in the molecule. The photoluminescence properties of the as-prepared phosphors were investigated and the Ce³⁺ ions in these hosts were found to give broadband emission in the UV range. For the thermoluminescence study, phosphors were irradiated with a 5 Gy dose of γ-rays from a ⁶⁰ Co source. Chen's half-width method was employed to calculate the trapping parameters from the thermoluminescence glow curve. Copyright © 2016 John Wiley & Sons, Ltd.

Novel optical properties of Ca12 Al10.6 Si3.4 O32 Cl5.4 :Ce3+ ,Li+ phosphor for solid-state lighting

This article reports a novel blue emission in a series of Ca₁₂ Al_10.6 Si_3.4 O₃₂ Cl_5.4 :Ce³⁺ phosphor under excitation in the near-UV wavelength range. This phosphor was prepared using the combustion method. Here, the Ce³⁺ emission band is observed over a broad range of 380-550 nm, under 365 nm excitation, and is due to 5d-4f transition. The effect of a Li⁺ charge compensator on the emission properties of the phosphor was also investigated for the first time. X-Ray diffraction confirmed the phase purity of the synthesized phosphor. The surface morphology and elemental composition of the phosphor were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.

Luminescence in Ba2 Sr2 Al2 O7 :RE (RE = Tb(3) (+) ,Eu(3) (+) and Dy(3) (+) ) novel aluminate phosphors

The luminescence of novel rare earth (Tb(3) (+) , Eu(3) (+) and Dy(3) (+) )-activated Ba2 Sr2 Al2 O7 phosphors for solid-state lighting is presented. The aluminate phosphors were synthesized using a one-step combustion method. X-Ray diffraction, scanning electron microscopy and photoluminescence characterizations were performed to understand the mechanism of excitation and the corresponding emission in the as-prepared phosphor, as characterized the phase purity and microstructure. Improvements in the luminescence properties of the phosphors with rare earth concentration were observed. The phosphor hue could be tuned from blue, green and red by proper selection of rare earth ions in typical concentrations. Effective absorption in the near-ultraviolet region was observed, which makes the phosphor a potential candidate for ultraviolet light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd.

Photoluminescence and electron paramagnetic resonance properties of a potential phototherapic agent: MMgF4 :Gd3+ (M = Ba, Sr) sub-microphosphors

Novel narrow band UVB-emitting phosphors, BaMgF₄ :Gd³⁺ and SrMgF₄ :Gd³⁺ phosphors, were synthesized using a co-precipitation synthesis method. X-Ray diffraction analysis was carried out to confirm compound formation, phase purity and crystallinity of the phosphor. At 274 nm excitation, phosphors show a sharp narrow band emission at 313 nm that can be assigned to ⁶ P_7/2  → ⁸ S_7/2 transition of the Gd³⁺ ion. With increasing dopant concentration, intensity enhances and then decreases after a certain concentration, which is an indication of concentration quenching taking place in the phosphor. Scanning electron microscopy images of the phosphor show agglomerated particles in the sub-micron range. Particles range in size from 600 to 800 nm. Electron paramagnetic resonance studies of the phosphors were carried out to detect radicals present in the prepared phosphor. With narrow band UVB emission, phosphor seems to be a good candidate for UV phototherapy application. Copyright © 2016 John Wiley & Sons, Ltd.

Combustion Synthesized Europium Doped LaAI₁₁O₁₈ Phosphors--An Electron Paramagnetic Resonance and Optical Study

By adopting a facile solution combustion synthesis, crystallized europium doped blue phosphors were successfully prepared. These phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared absorption (FT-IR), energy dispersive analysis of X-ray, Electron Paramagnetic Resonance (EPR) and Photoluminescence (PL) experimental methods. The photoluminescence spectrum indicates Eu²⁺ and Eu³⁺ ions in these phosphors. The band at around 442 nm is attributed to the spin-allowed 4f⁶5d¹ (2D) --> 4f⁷(⁸S₇/2) transition of Eu²⁺ ions. The sharp bands at 591 (⁵D₀ --> ⁷F₁) and 616 (⁵D₀ --> ⁷F₂) nm are attributed to the spin-forbidden transitions of Eu³⁺ ions. The EPR spectra of as-prepared and post-treated LaAl₁₁O₁₈:Eu phosphors exhibit signals characteristic of La²⁺ and Eu²⁺ ions. The number of spins, Gibbs energy, magnetic susceptibility, Curie constant and effective magnetic moment values were calculated and compared at 296 and 110 K.

Synthesis and characterization of erbium-doped YAlO3 phosphor

In the yttrium aluminium system, the YAlO3 phosphor is a prominent host because of the yttrium aluminium ratio (1:1). Phosphor was synthesized by the solid-state reaction method at variable concentrations of erbium (0.1-2.5 mol%). This method is suitable for large-scale production and is a less time-consuming method when compared with the soft synthesis method. The prepared sample was characterized by X-ray diffraction technique and the crystallite size was calculated by Scherer's formula. Vibrational and bending analysis of prepared phosphor for optimized concentration of erbium ion is described based on the Fourier transform infrared spectroscopic technique. The photoluminescence (PL) emission spectra of prepared phosphor for variable concentrations of erbium ion were recorded and the excitation spectrum was found to be at 291 nm with three shoulder peaks at 305, 270 and 242 nm. For 291 nm excitation, the emission spectrum was found at 546 nm and 552 nm. PL intensity increased with increasing concentrations of erbium and after 2 mol% emission intensity decreased due to concentration quenching. Spectrophotometric determination of YAlO3:Er(3+) is described by CIE co-ordinates and shows an intense emission in the green region such that the prepared phosphor can act as a single host for green light emission. Thermoluminescence glow curve analysis of the YAlO3:Er(3+) phosphor was recorded for different ultraviolet (UV) light exposures and gamma exposure. Different gamma doses 0.5-2 kGy show a linear response. Kinetic parameters were calculated by the peak shape method.

Luminescence of Eu and Ce in K3Ca2(SO4)3F fluoride material

A new halophosphor K3Ca2(SO4)3F activated by Eu or Ce and K3Ca2(SO4)3F:Ce,Eu co-doped halosulfate phosphor has been synthesized by the co-precipitation method and characterized for its photoluminescence (PL). The PL emission spectra of the K3Ca2(SO4)3F:Ce phosphor show emission at 334 nm when excited at 278 nm due to 5d → 4f transition of Ce(3+) ions. In the K3Ca2(SO4)3F:Eu lattice, Eu(2+) (440 nm) as well as Eu(3+) (596 nm and 615 nm) emissions have been observed showing (5) D0 →(7) F1 and (5) D0 →(7) F2 transition of the Eu(3+) ion, which is in the blue and red region of the visible spectrum respectively. The trivalent europium ion is very useful for studying the nature of metal coordination in various systems owing to its non-degenerate emitting (5) D0 state. K3Ca2(SO4)3F:Ce,Eu is suitable for Ce(3+) → Eu(2+) → Eu(3+) energy transfer in which Ce(3+) and Eu(2+) play the role of sensitizers and Eu(2+) and Eu(3+) act as the activators. The observations presented in this paper are relevant for lamp phosphors.

Synthesis and characterization of Ba3Si6O12N2:Eu(2+) phosphor

Eu(2+)-doped Ba3Si6O12N2 phosphors were prepared successfully via a modified solid-state diffusion method. The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence measurements. These phosphors were effectively excited at 355 nm and an intense emission peaking in the range 480 nm to 525 nm in the blue region was observed. The optimized dopant concentration was determined to be 1 mol% of Eu(2+) ion. The colour coordinates for phosphor were found to be (0.196, 0.326) in the blue region. This phosphor may find application for near-ultraviolet (NUV) excited lamp phosphors. The thermoluminescence study shows the complex glow curve. Trapping parameters (activation energy and frequency factor) were calculated for individual deconvoluted peaks by Chen's peak shape method, the initial rise method and the whole glow peak method.

Energy transfer between Ce³⁺ → Gd³⁺ or Tb³⁺ in KNaSO₄ microphosphor

KNaSO4 microphosphor doped with Ce,Gd and Ce,Tb and prepared by a wet chemical method was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) characterization. KNaSO4 has a 5-µm particle size detected by SEM. KNaSO4:Ce(3+),Tb(3+) showed blue and green emission (at 494 nm, 557 nm, 590 nm) of Tb(3+) due to (5)D(4)  → (7)F(J) (J = 4, 5, 6) transitions. KNaSO4:Ce(3+),Gd(3+) showed luminescence in the ultraviolet (UV) light region at 314 nm for an excitation at 271 nm wavelength. It was observed that efficient energy transfer took place from Ce(3+)  → Gd(3+) and Ce(3+)  → Tb(3+) sublattices indicating that Ce(3+) could effectively sensitize Gd(3+) or Tb(3+) (green emission). Ce(3+) emission weakened and Gd(3+) or Tb(3+) enhanced the emission significantly in KNaSO4. This paper discusses the development and understanding of photoluminescence and the effect of Tb(3+) and Gd(3+) on KNaSO4:Ce(3+).

Mechanoluminescence, thermoluminescence, photoluminescence studies on Ca3Y2Si3O12:RE(3+) (RE(3+) = Dy(3+) and Eu(3+)) phosphors

Dy(3+) and Eu(3+) activated Ca3Y2Si3O12 phosphors were synthesized by the solid-state synthesis method. The phosphors were characterized by X-ray diffraction (XRD), mechanoluminescence (ML), thermoluminescence (TL) and photoluminescence (PL) to determine structure and luminescence. For ML glow curves, only one peak was observed, as only one type of luminescence centre was formed during irradiation. The Ca3Y2Si3O12:Dy(3+) TL glow curve showed a single peak at 151.55 °C and the Ca3Y2Si3O12:Eu(3+) TL glow curve peaked at 323 °C with a small peak at 192 °C, indicating that two types of traps were activated. The trapping parameters for both the samples were calculated using Chen's peak shape method. Dy(3+)-activated Ca3Y2Si3O12 showed emission at 482 and 574 nm when excited by a 351 nm excitation wavelength, whereas the Eu(3+)-activated Ca3 Y2Si3O12 phosphor PL emission spectra showed emission peaks at 613 nm, 591 nm, 580 nm when excited at 395 nm wavelength. When excited at 466 nm, prominent emission peaks were observed at their respective positions with very slight shifts.