Decay Time Profiles Research Articles

Photophysical, photodynamical, redox properties and BSA interactions of novel isomeric tetracationic peripheral palladium(II)-bipyridyl porphyrins.

New isomeric tetra-cationic porphyrins containing peripheral [Pd(bpy)Cl]+ units attached to pyridyl substituents were synthesized and fully characterized. The porphyrins present an intense Soret band located in the blue spectral region and an additional four weaker red-shifted Q bands in the visible spectral region (about 500-700 nm). The obtained Strickler-Berg parameters indicate fully spin and symmetry allowed transitions for all the observed absorption bands. Both porphyrins present two fluorescence emission bands, an intense one located around 650 nm and an additional weak red-shifted emission at ∼710 nm. Fluorescence decay time profiles were obtained showing bi-exponential decay. The interaction of the porphyrins with bovine serum albumin (BSA) was studied in detail by a fluorescence quenching method and molecular docking analysis. In addition, the photodynamical activity of the porphyrins in the photooxidation of BSA was determined and compared with the light-induced formation of reactive oxygen species (ROS) by electron paramagnetic resonance (EPR) allied with the spin trapping method. The results show that the Pd(ii)-bypyridyl tetra-cationic porphyrins are promising candidates for the photooxidation of biological substrates used in photodynamic therapy (PDT).

Cold bluish white and blue emissions in Cu+-doped zinc phosphate glasses

Reducing agent-free zinc phosphate glasses doped with cooper ions (Cu+) were synthesized by melt-quenching technique. The physical properties of these glasses such as density, molar volume and refractive index were studied. The X-ray diffraction (XRD) patterns for all prepared glasses, confirm their amorphous structure. Raman spectroscopy suggest that the phosphate network is composed by tetrahedral PO4 units, since the vibrations of P–O–P, PO2 and PO, observed in the spectra, belong to the PO4 units. All glasses display absorptions bands in the ultraviolet and near infrared regions, associated with the absorption edge and contribution of the Cu+:1Ag → 1T2g + 3T2g (280 nm) and Cu2+: 2Eg → 2Tg (890 nm) transitions, respectively. The optical band gap values determined from the absorption spectra assuming indirect optical band gap, are reduced from 4.83 to 2.95 eV for Cu+ content in the range of 0–0.3 mol%. For Cu+ concentration higher than 0.3 mol%, band gap values increase up to 3.17 eV. Such last behaviour was attributed to the reduction of the amount of Cu+ species and/or Moss-Burstein effect. The emission spectra of the Cu+-doped zinc phosphate glasses upon 272 and 290 nm excitation, displayed overall bluish white light and blue emission, depending the excitation wavelength and Cu+ contents. A maximum photoluminescence quantum yield value of 12.5% with an inherent uncertainty up to 3.75%, was reached under 290 nm excitation. The emission decay time profiles were well fitted to a bi-exponential function from which the average lifetimes values resulted to be in the interval of 26.8–16.7 μs, which are shortened for Cu+ contents higher than 0.3 mol%. The structural and photoluminescence characteristic makes of the reducing agent-free Cu+-doped zinc phosphate glasses potentially attractive for blue phosphors and WLEDs applications.

Alpha and gamma spectroscopy of composite scintillators based on the LuAG:Pr crystals and single crystalline films of LuAG:Ce and (Lu,Gd,Tb)AG:Ce garnets

Alpha and gamma spectroscopy (pulse height spectra and scintillation decay time profiles) were used to study scintillating properties of composite scintillators systems consisting of single crystalline films (SCF) and single crystal (SC) substrate plates. α-particles of 241Am of energy 5.4857 MeV and γ-quanta of 137Cs of energy 661.66 keV are used as excitation sources of SCFs or SC substrates, respectively. As SC substrates mainly LuAG:Pr single crystal plates are used and these plates are characterized by light yield (LY) between 10-21 × 103 ph/MeV, Energy Resolution (ER) ~5% at 661.66 keV and good proportionality. LuAG:Ce, Lu2-xGdTbxAG:Ce and Lu3-xTbxAG:Ce SCFs at x = 0.15–2.285 were prepared by LPE method onto LuAG:Pr substrates and investigated. LY of LuAG:Ce SCF under α-particles excitation is about of 60% than that of LuAG:Pr SC substrate. The LY of Lu3-x TbxAG:Ce SCFs depend nonlinearly on Tb3+ concentration in the 0.15–2.285 range and changed from 60-62% to 106–109%, respectively, in comparison with LY of LuAG:Pr SC substrate. Detailed scintillation decay time profiles have shown that there are differences between the decay curves of composite scintillators under α-particles and γ-quanta excitations. Such differences are characterized using the tα/tγ ratio between the time of scintillation decay to 1/e, 0.1, 0,05 and 0.02 levels under α-particles excitation (tα) and γ-quanta excitation (tγ). From all studied types of composite scintillators, based on the LuAG:Pr substrates, the highest value of tα/tγ ratio can be reached for Lu3-xTbxAG:Ce SCF/LuAG:Pr SC substrate composite scintillators at Tb content x = 2.15–2.275, where this ratio is equal to 4.2–6.2 at scintillation decay level of 0.1.

Calcium-zinc phosphate glasses activated with Tb3+/Eu3+ for laser and white LED applications

A spectroscopic analysis of Tb3+, Eu3+ and Tb3+/Eu3+ doped calcium-zinc phosphate glasses is carried out through their absorbance and photoluminescence spectra, and decay time profiles. Laser parameter values (stimulated emission cross section, effective bandwidth, gain bandwidth and optical gain) were obtained for the europium 5D0 → 7F2 red and terbium 5D4 → 7F5 green emissions upon 392 and 350 nm excitations, respectively, to judge the suitability of the glass phosphor for fiber lasers. The Tb3+/Eu3+ activated phosphor tonality can be shifted from reddish-orange of 1744 K upon 376 nm excitation to warm white of 3560 K and neutral white of 4414 K upon 370 and 368 nm excitations, respectively. From decay time profiles of the terbium 5D4 and 5D3 levels in the co-doped glass is inferred that Eu3+ can be sensitized by Tb3+ through a non-radiative energy transfer. An electric dipole-dipole or quadrupole-dipole interaction into Tb3+ - Eu3+ clusters could be the dominant mechanism in the Tb3+ to Eu3+ energy transfer. Tb3+ and/or Eu3+ activated calcium-zinc phosphate glasses, pumped by UV LED chips, could be appropriate phosphors for the development of materials emitting neutral/warm white light, reddish-orange light or green/red laser light.

Spectroscopic evaluation a new and novel Nd3+/Yb3+ co-doped CdO-V2O5 glass system for 1 μm laser application

Structural and spectral evaluations of Nd3+ and Nd3+/Yb3+ doped CdO-V2O5 glasses based on X-Ray diffraction, Raman spectroscopy, absorption, excitation and emission spectra and decay time profiles, are performed. X-Ray diffraction patterns and Raman spectroscopy revealed that all samples are amorphous (glassy phase) up to 4 mol% of Yb3+, without segregation of any crystalline phase. The optical band gap values determined from the absorption spectra, assuming direct optical band gap, were in the range of 2.13–2.07 eV, depending on the Yb3+ concentration. The emission spectra of the Nd3+ and Nd3+/Yb3+ doped glasses upon Nd3+ excitation at 585 nm, displayed the NIR Nd3+ feature emissions centered at 880, 1060 and 1342 nm, and Yb3+ emission at 977 nm, being the latter one achieved at expenses of energy transfer from Nd3+. According to the shortening of the Nd3+ emission decay profiles such process is not radiative with efficiency in the range of 0.181–0.521, depending on the Yb3+ content. The 880 nm Nd3+ decay fitting using the Inokuti-Hirayama model considering, energy migration among donors, suggested that an electric dipole-dipole interaction might mediate the energy transfer process, within Nd3+-Yb3+ clusters.

Luminescent properties and energy transfer of Tm3+/Dy3+ co-doped oxyfluoride borate glasses for white LEDs

Tm3+/Dy3+ co-doped oxyfluoride borate glasses with composition of 25CaF2–25ZnO–6P2O5–44B2O3 (mol%) for white light-emitting diodes were synthesized by a conventional melting-quenching method. The glass structure, spectroscopic properties and decay time profiles were characterized by XRD and FT-IR, optical and fluorescence spectrum measurements. Under 354 nm excitation, the color tones change from light blue (0.3004, 0.2646) to warm white (0.3626, 0.3642) by increasing concentration of Tm3+. The shortening of the Dy3+ emission decay time in presence of Tm3+ suggests that Dy3+/Tm3+ non-radiative energy transfer occurs. By using the Inokuti–Hirayama model, it is inferred that an electric quadrupole–quadrupole interaction might be the dominant mechanism involved in the energy transfer. The results suggest that the as-prepared Tm3+/Dy3+ co-doped oxyfluoride borate glasses may be promising candidate in white LEDs and other display devices.

Scintillation performance of the TlSr2I5 (Eu2+) single crystal

TlSr2I5: Eu2+ is a newly discovered scintillator that show promising scintillation properties for X- and γ-ray spectroscopy applications. Two zone vertical Bridgman technique is used for the growth of this scintillator. Luminescence properties of the grown crystals are measured under X-ray excitation at room temperature. Pure and Eu2+ doped crystals contained broad emission bands between 445 and 670 nm peaking at 528 nm and 430–600 nm peaking at 463 nm, respectively. Energy resolution, light yield and decay time profiles are studied under 662 keV γ-ray excitation using 137Cs radioactive source. Energy resolution of 4.2% (FWHM) is obtained for 3 mol% Eu2+ doped crystal. For the same sample, light yield of 70,000 ph/MeV is also obtained. Three and two decay constants are observed for the pure and Eu2+ doped samples, respectively at room temperature. Effective Z-number and density are found to be 61 and 5.30 g/cm3, respectively.

Luminescence and low temperature trap centers in mixed rare earth borate crystal

The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10–300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence (TL) glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10–300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were calculated using various standard methods such as peak shape (PS), variable heating rate (VHR), initial rise (IR) and computerized glow curve deconvolution (CGCD).

Lithium-aluminum-zinc phosphate glasses activated with Tb3+ and Tb3+/Eu3+ for green laser medium, reddish-orange and white phosphor applications

A spectroscopic analysis of Tb3+ and Tb3+/Eu3+ doped lithium-aluminum-zinc phosphate glasses is performed through their absorbance and photoluminescence spectra, and decay time profiles. Laser parameter values (stimulated emission cross section, effective bandwidth, gain bandwidth and optical gain) were obtained for the terbium 5D4 → 7F5 green emission from the Tb3+ singly-doped glass (LAZT) excited at 350 nm to judge the suitability of the glass phosphor for fiber lasers. A quantum yield of (47.68 ± 0.49)% was measured for the 5D4 level luminescence. Upon 350 nm excitation the LAZT glass phosphor emits green light with a color purity of 65.6% and chromaticity coordinates (0.285, 0.585) very close to those (0.29, 0.60) of European Broadcasting Union illuminant green. The Tb3+/Eu3+codoped glass emission color can be tuned from reddish-orange of 1865 K upon 318 nm excitation to warm white of 3599 K and neutral white of 4049 K upon 359 and 340 nm excitations, respectively. Upon Tb3+ excitation at 340 nm Eu3+ is sensitized by Tb3+ through a non-radiative energy transfer with an efficiency of 0.23–0.26. An electric dipole-dipole interaction might be the dominant mechanism in the Tb3+ to Eu3+ energy transfer taking place into Tb3+ - Eu3+ clusters.

Photoluminescence and scintillation properties of Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) crystals

Apatite crystals with chemical compositions of 0.5% Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) were synthesized by the Floating Zone method, and then we evaluated their photoluminescence (PL) and scintillation properties. All the Ce-doped samples exhibited PL and scintillation with an intense broad emission in 400–550 nm in which the origin was attributed to the 5d-4f transition of Ce3+, and the emission peak became broader with increasing the concentration of Lu3+. Both PL and scintillation decay time profiles were best-approximated by a sum of two exponential decay functions, and the origin of slower component was attributed to the 5d-4f transition of Ce3+. In the X-ray induced afterglow measurements, the Ce-doped Sr2(Gd0.4Lu0.6)8(SiO4)6O2 sample exhibited the lowest afterglow level. Furthermore, the Ce-doped Sr2(Gd0.5Lu0.5)8(SiO4)6O2 and Sr2(Gd0.4Lu0.6)8(SiO4)6O2 samples showed a clear full energy deposited peak under 5.5 MeV 241Am α-ray irradiation, and the estimated absolute scintillation light yields were around 290 and 1300 ph/5.5 MeV-α, respectively.

Spectroscopy evaluation of crystalline and amorphous Cd2V2O7 as blue phosphors

Cd2V2O7 compounds in crystalline and amorphous phases were fabricated by the melt-quenching process. Characterizations such as X-ray diffraction, Raman spectroscopy and photoluminescence were performed. X-ray diffraction patterns of the crystalline sample showed peaks associated with a pure Cd2V2O7 monoclinic structure, in agreement with the Raman vibrational spectrum. In the case of the amorphous sample, X-ray diffraction patterns only exhibited a broad band, typical of a glassy structure, whereas its Raman spectrum displayed two broad vibrational modes centered at 350 and 850cm−1, attributed to stretching vibrations of VO3 groups. In spite of the structural differences, both samples presented similar photoluminescence features, consisting of a wide band in the 375–525nm range with two peaks at 411 and 432nm, associated respectively with the 3T2 → 1A1 and 3T1 → 1A1 electronic transitions in the VO4 tetrahedron, under 340nm excitation. Thus, blue light emission with CIE1931 chromaticity coordinates x~ 0.200 and y~ 0.145, and color purity of 62–63%, is achieved from the crystalline and amorphous Cd2V2O7 compounds. The emission decay time profiles were well fitted to a bi-exponential function from which the calculated average lifetime values resulted to be 112 ± 13 and 99 ± 4ns for the crystalline and amorphous Cd2V2O7 samples, respectively. Theoretical calculations based on the density of electronic states revealed that the photoluminescence arises through charge transference processes from 3d orbitals of four-fold coordinated vanadiums to 2p orbitals of three-fold coordinated oxygens in the VO4 tetrahedron, being the basic unit of Cd2V2O7 in crystalline and amorphous phases.

Yellow to orange-reddish glass phosphors: Sm3+, Tb3+ and Sm3+/Tb3+ in zinc tellurite-germanate glasses

An optical spectroscopy analysis of TeO-GeO2-ZnO glass co-activating Sm3+/Tb3+ ions was carried out through Raman, photoluminescence spectra and decay time profiles as a function of Sm3+ concentration. According to the estimated CIE1931 chromaticity coordinates, the color of the emission can be adjusted from the yellow light region (0.4883, 0.4774), towards the reddish light region (0.5194,0.4144) by increasing the Sm3+ content from 1, 3, 5% mol, co-doped with 1% mol Tb3+ under co-excitation of Sm3+ and Tb3+ at 378 nm. The color temperatures are in the range of 1379–2804 K. Such photoluminescence is generated by the 4G 5/2 → 4H 5/2, 4H 7/2, 4H9/2 emissions of Sm3+ in addition to the 5D4→7F6,5,4,3 emissions of Tb3+; the single doped Sm3+ glass displayed an intense orange light. Meanwhile, co-doped Sm3+/Tb3+ glasses excited at 378 nm showed a significant reduction in Tb3+ emission, with a simultaneous increment in the reddish-orange emission of Sm3+, due to a non-radiative resonant energy transfer from Tb3+ to Sm3+. Decay time profile analysis of the Tb3+ emission as function of Sm3+ ion content suggests that an electric dipole–dipole interaction into Tb3+–Sm3+ clusters might dominate in the energy transfer process, with an efficiency and probability of 0.22, 0.27, 0.38 and 122.8, 327.6, 522.7 s−1, respectively.

Optical and radioluminescence properties of Ce-doped Sr2RE8(SiO4)6O2 (RE = Y, Gd, Lu)

Ce-doped Sr2Y8(SiO4)6O2, Sr2Gd8(SiO4)6O2 and Sr2Lu8(SiO4)6O2 (SrYS, SrGS and SrLuS, respectively) apatite crystals were grown by the Floating Zone method, and their optical and radioluminescence (RL) properties were characterized. In the photoluminescence (PL) and RL spectra, we observed an emission band between 400 and 500nm for all the samples, which were due to the 5d-4f transition of Ce3+. The RL decay time profiles were approximated by a sum of two exponential decay functions, and the origin of faster decay component was due to the 5d-4f transition of Ce3+. Among all the samples, SrGS sample showed the lowest afterglow level. In the pulse height spectrum, all the samples showed a full energy absorption peak under 241Am 5.5MeV α-ray irradiation. The absolute scintillation light yields of SrYS, SrGS and SrLuS were around 31, 76 and 940ph/5.5MeV-α, respectively.

Photoluminescence, scintillation and thermally-stimulated luminescence properties of Tb-doped 12CaO·7Al2O3 single crystals grown by FZ method

Tb-doped 12CaO·7Al2O3(Tb:C12A7) crystals were synthesized by the floating zone (FZ) method and the photoluminescence (PL), scintillation and thermally-stimulated luminescence (TSL) properties were investigated. The photoluminescence (PL) emission spectra and PL decay time profiles were investigated by using Quantaurus-tau (Hamamatsu). The scintillation spectra and decay time profiles were measured by using our laboratory-constructed set-up under X-ray irradiation. Finally, TSL glow curve was measured by using Nanogray TL-2000 with the heating rate of 1 °C/s. In PL and scintillation, emission peaks were observed at 493, 543, 587 and 620 nm due to the 4f-4f transitions of Tb3+. Decay time constants of the emission by PL and scintillation appeared to be different, and the measured values were approximately 2.4 and 1.9 ms, respectively. After X-ray irradiations, the 0.5% (all Tb contents in this paper are in mole fraction) and 1.0% Tb-doped samples showed a single intense and broad glow peak around 100 °C while 1.2%−1.5% Tb-doped samples showed notable additional peak around 250 °C.

Protolytic behavior of axially coordinated hydroxy groups of Tin(IV) porphyrins as promising molecular catalysts for water oxidation

A series of four Tin(IV)porphyrins with different substituents on meso-phenyl groups, trans-dihydroxy-5,10,15,20-tetra(p-tolyl)porphyrinatetin(IV) (Sn(IV)TTP(OH)2), trans-dihydroxy-tetra(2,4,6-trimethyl)phenylporphyrinatetin(IV) (Sn(IV)TMP(OH)2), trans-dihydroxy-5,10,15,20-tetra(p-carboxyphenyl)porphyrinatetin(IV) (Sn(IV)TCPP), and trans-dihydroxy-5,10,15,20-tetra(N-methyl-4′-pyridiniumyl)porphyrinatetin(IV) (Sn(IV)TMPyP(OH)2) have been prepared and characterized focusing on their protolytic behavior of the axial ligands, hydroxy groups, both in the ground and excites states as well as their electrochemical oxidation behavior. The two axially ligating hydroxy groups on each Tin(IV)-porphyrins exhibit protonations and deprotpnations in five steps. The pKa value of each protolytic equilibrium in the ground states was spectrophotometrically determined, while fluorescence decay time profiles indicate that the protolytic processes are sufficiently slower than the intrinsic fluorescence decay rates to lead to non-protolysis in the excited states. The oxidation peak potentials were determined by cyclic voltammetric analysis. Pourbaix diagram of each protolytic species of Sn(IV)TMPyP in water indicated that the one-electron oxidation of fully deprotonated Sn(IV)TMPyP(O−)2 is not a proton-coupled process, while the doubly hydroxy coordinated species Sn(IV)TMPyP(OH)2 has a proton-coupled one. Tin(IV)-porphyrins exhibit efficient catalytic currents on the first oxidation wave in their cyclic voltammetry and the saturated catalytic currents were high enough in a wide range of pH to be promising as water oxidation catalysts. This is the first detailed study on Tin(IV)-porphyrins to examine water oxidation ability of the one-electron oxidized form against twenty kinds of species (five protolytic species for each of the four Tin(IV)-porphyrins).

Scintillation and optical properties of Ce3+-doped CaGdAl3O7 single crystals

The single crystals of 0, 0.6, 1, 1.6 and 2mol% Ce doped CaGdAl3O7 (Ce:CGAM) were grown by the Floating Zone method, and investigated on photoluminescence (PL) and scintillation properties. In the PL spectra, a broad emission appeared over 380–500nm under 280 and 360nm excitations with the quantum yield of 33.8–38.8%. Under a vacuum ultraviolet excitation (90nm) using a synchrotron source, non-doped CGAM single crystal showed broad emissions over 250–650nm. The PL decay time profiles followed a monotonic exponential decay with a decay time constant of around 33ns. The scintillation spectra were similar to those of PL. All of the samples exhibited a clear photoabsorption peak and Compton edge in the pulse height spectra measured under 137Cs γ-ray irradiation, and the absolute scintillation light yield (LY) was highest for the 2% Ce-doped sample with the value of 3300±300ph/MeV. The scintillation decay profiles were approximated by a third order exponential decay function, and the extracted decay time of Ce3+ emission component was around 36–44ns. Among all the samples, 2%Ce:CGAM single crystal sample showed the best afterglow level as a scintillator under X-ray irradiation.

X-ray induced luminescence properties of (Y,Eu)AlO3 single crystals

We investigated photoluminescence, scintillation and dosimeter properties of (Y1-x Eux)AlO3 (x = 0.001, 0.5 and 1) single crystals (hereafter denoted as Eu:YAP for x = 0.001, EYAP for x = 0.5 and EAP for x = 1). The samples were prepared by the Floating Zone method. In photoluminescence (PL), we observed a broad emission around 300–400 nm due to host under excitation of 280 nm, and emissions due to the 4f state transitions of Eu3+ appeared around 590 nm and 615 nm. Scintillation spectra also show emission peaks around 590 and 615 nm due to the 4f state transitions of Eu3+ in all the samples. In addition, emissions around 300–400 nm due to YAP host and around 550–700 nm due to 5d-4f transitions of Eu2+ appeared in Eu:YAP. The PL and scintillation decay time profiles consisted of several exponential decay components. The fast (ns) component group was possibly due to host emission, and especially Eu:YAP demonstrated a very fast PL decay time of 16 ns. The intermediate (μs) component group was due to the 5d-4f transitions of Eu2+. The slow (ms) component group was ascribed to the 4f state transitions of Eu3+ ion. The Eu:YAP sample showed intense thermally-stimulated luminescence (TSL) with peaks at 46, 155, 255 and 443 °C. The intensity was much higher than those of EAP and EYAP. In particular, the peak at 254 °C, which showed the highest intensity, was due to doping with Eu. The TSL dose response function showed a good linearity (R2 > 0.99) over a wide dose range from 0.1 mGy to 100 mGy for Eu:YAP, which showed the highest sensitivity among the present samples.

Optical, scintillation and thermally stimulated luminescence properties of Ce-doped yttrium–aluminum–indium garnet

We have investigated the photoluminescence (PL), scintillation and thermally stimulated luminescence (TSL) properties of 1 mol % Ce-doped Y3(AlXIn1−X)5O12 (X = 0–1; Ce:YAING). These samples showed strong and broad PL emission by Ce3+ ion appeared in the spectral range from 480 to 620 nm. The PL decay profiles can be represented by a first-order exponential function with the decay time ranging 39–62 ns. Furthermore, the scintillation spectra showed similar features with those observed in PL. The scintillation decay time profiles were approximated by second or third order exponential decay functions, and we observed 26–61 ns component due to Ce3+ emission. The X-ray induced afterglow levels of Ce:YAING were worse than that of Ce:Y3Al5O12. The pulse height spectra of Ce:Y3(Al0.26In0.74)5O12 showed a clear photoabsorption peak, and that of the scintillation light yield was around 6,700 photons/MeV. In TSL glow curves, Ce:YAING show the glow peak at around 110 °C.

Reddish-orange and neutral/warm white light emitting phosphors: Eu3+, Dy3+ and Dy3+/Eu3+ in potassium-zinc phosphate glasses

A multicolor luminescence investigation of potassium-zinc phosphate glasses activated with Eu3+, Dy3+ and Dy3+/Eu3+ is performed by analyzing their Raman and photoluminescence spectra, and decay times. Reddish-orange light emission, with a correlated color temperature (CCT) of 2117K and a high color purity of 96.8%, is observed in the Eu3+ singly-doped glass excited at 393nm. Upon Dy3+ excitation at 348nm the Dy3+ singly-doped glass emits neutral white light of 4396K, and codoping with Eu3+ the glass phosphor also emits neutral white light of 4017K. In the codoped glass the neutral white light emission is generated mainly by the transitions 5D0→7F2 of Eu3+ and 4F9/2→6H13/2, 6H15/2 of Dy3+, Eu3+ being sensitized by Dy3+ through non-radiative energy transfer with an efficiency of 0.11. From an analysis of Dy3+ emission decay time profiles it is inferred that an electric quadrupole-quadrupole interaction into Dy3+ – Eu3+ clusters might be the dominant mechanism in the Dy3+ to Eu3+ energy transfer. Upon Dy3+ and Eu3+ co-excitations at 362 and 381nm, the Dy3+/Eu3+ codoped glass can exhibit warm white and reddish-orange overall emissions, with CCT values of 3040 and 1735K, respectively.

Scintillation properties of rare-earth doped NaPO3-Al(PO3)3 glasses

We systematically investigated photoluminescence (PL), scintillation and dosimeter properties of rare-earth (RE) doped NaPO3-Al(PO3)3 (NAP) glasses. The NAP glasses doped with a series of RE ions (La-Yb, except Pm) with a consistent concentration (0.3 wt%) were prepared by the conventional melt-quenching method. The PL and scintillation decay time profiles showed fast (ns) and slow (μs or ms) components: the fast components from 15 to 100 ns were due to the host or 5d-4f transition emission, and the slow components from 15 μs to 5 ms were due to the 4f-4f transitions of RE. The thermally stimulated luminescence (TSL) was evaluated as a dosimeter property, and glow peaks appeared around 400 °C in all the samples. The TSL dose response function was examined in the dose range from 10 mGy to 10 Gy. Among the samples tested, Nd and Tb doped glasses showed higher signal by at least one order of magnitude than those of non-doped and other RE-doped samples. Over the dose range tested, the TSL signals are linearly related with the incident X-ray dose, showing a potential for practical applications.