Main Emission Bands Research Articles

Effect of the reducing atmospheres on the photoluminescent and phosphorescent properties of Sr4Al14O25:Eu2+, Dy3+, Cr3+ phosphors

This work reports the effects of two reducing atmospheres (N2 + H2 and carbon) on the luminescent, morphological, and structural properties of Sr4Al14O25:Eu2+ (1 mol%), Dy3+ (2 mol%), Cr3+ (1–4 mol%) [SALO:Eu, Dy, Cr] phosphors. They were synthesized by a combustion method followed by an annealing treatment in a reducing atmosphere. According to scanning electron microscopy (SEM) images, the samples annealed in both types of reducing atmospheres present microparticles with irregular shape. An increase of Cr concentration from 1 to 4 mol% produced microparticles with higher porosity. X-ray diffraction patterns demonstrated that the orthorhombic phase was maintained in all the samples synthesized with different Cr concentrations or reducing atmospheres. Two main emission bands centered at 490 and 693 nm were observed in the SALO:Eu, Dy, Cr phosphors under excitation at 375 nm. In general, the annealing under carbon atmosphere produced the strongest luminescent emission and the longest phosphorescence times in SALO:Eu, Dy, Cr phosphors. When the Cr concentration is increased from 1 to 4 mol%, the phosphorescence times for the NIR and VIS bands were drastically reduced from ≈1830 to 40–60 s. The phosphorescence intensity was favored by the presence of defects such as oxygen vacancies (Vo) and Dy3+–Vo traps, which were formed after the introduction of Dy3+ and Cr3+ ions in the SALO host. The presence of these defects was confirmed by absorbance measurements. The annealing in carbon atmosphere is simpler than that in H2 + N2 atmosphere and leads to enhanced luminescent properties of SALO:Eu, Dy, Cr phosphors.

Engineering Ratiometric Persistent Luminous Sensor Arrays for Biothiols Identification.

Thiols play vital roles in mediating physiological processes. However, it is difficult to discriminate one thiol from another because of the similarities among structures and reactivities of thiols. In light of the ultralow background and impressive discrimination power, a persistent luminescence-based sensing array has attracted increasing attention but still remains a huge challenge. Herein, we have thoroughly studied the chemistry involving dual-emission persistent luminescence nanoparticles (D-PLNPs) with metal ions (MIs) and for the first time proposed an MIs-triggered ratiometric persistent luminescence (R-PersL) sensor array for the discrimination of six thiols. To extract data-rich outputs from a single sensor element, three representative D-PLNPs with a core-shell structure and subsequent carboxyl functionalizations (CSD-PLNPs) were rationally fabricated. Interestingly, MIs revealed the different regulating efficiencies for the two main emission bands of CSD-PLNPs, resulting from MI-triggered R-PersL signal transductions. Inspired by the crucial roles of thiols in vivo, a proof-of-concept sensor array through the ensemble of CSD-PLNPs-COOH and certain MIs was developed and demonstrated aR-PersL "fingerprint" pattern identification for six thiols. Remarkably, because of the autofluorescence-free background and high-throughput signal output, this sensing array system enabled a highly sensitive and differentiable detection of thiols at various concentrations in human blood serums, paving a new way to develop multiparameters sensing for complex analytes.

Synthesis and photoluminescence properties of nanoporous anodic aluminum oxide (NAAO): Sm3+ nanocomposite layer: Effect of anodizing parameters (time and voltage), Sm3+ concentrations, and annealing temperatures

In the present work, nanoporous anodic aluminum oxide (NAAO) layers were synthesized by mild and mild-hard anodization methods in a solution of oxalic acid and photoluminescence properties of these oxide layers were compared. Then, the nanoporous anodic aluminum oxide: Sm3+ (NAAO: Sm3+) nanocomposite layer is produced by boiling the NAAO layers in a solution of samarium nitrate and annealing at different temperatures under argon atmosphere. Moreover, effect of anodizing parameters (time and voltage), Sm3+ concentrations, and annealing temperatures on photoluminescence properties of the NAAO: Sm3+ nanocomposite layers were investigated and results indicate composition of SmAlO3. Finally, morphology, phase structure, energy levels, and emission wavelengths of the oxide layers were investigated by field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), and photoluminescence (PL) spectroscopy. Results indicate that the PL intensity of the NAAO layers produced by mild-hard anodization is more than the mild anodization. Moreover, the layers produced at 120 V for 2 h have the most PL intensity. At 1200 °C temperature, 0.7 M concentration of samarium ions the most PL intensity is created. Moreover, with the excitation of the NAAO: Sm3+ nanocomposite layer created at 400 nm wavelength, three main emission bands from the 4f-4f intra-configuration transitions from Sm3+ ions are clearly observed. These transitions include 4G5/2 → 6H5/2, 4G5 2 → 6H7/2, and 4G5/2 → 6H9/2.

Synthesis and multicolor emission properties of polystyrene with difluoroboron avobenzone complexes at side chains

Random copolymers (poly(ABSt-co-St)) consisting of avobenzone-BF2 complex monomer (ABSt) and styrene (St) were synthesized and used for emission color tuning including white-like emission in the solid state using St units as a spacer. The emission color of ABSt in the resulting copolymers changed from green to blue via bluish-white by changing the content of St. The fluorescence quantum yields of the polymers in the solid state were relatively high (Φf = 0.30–0.51) independent of the composition contents. The polymers have two main emission bands around 440 and 540 nm, which were derived from the emission of single-molecule and amorphous aggregation, respectively. The fluorescence color changed according to a change in the ratio of the fluorescence intensity at 440 and 540 nm (F440/F540). The absorption and fluorescence properties of the polymers in tetrahydrofuran were independent of the composition ratio of ABSt and St, which indicates no intermolecular interaction between avobenzone-BF2 (AB) fluorophores in the intra-polymer chain. The emission color of all polymers in the solution was blue and the fluorescence spectra were the same as that of ABSt in the solution. Thus, emission color changes observed in the solid state were mainly derived from the intermolecular interaction between AB fluorophores in inter-polymer chains because the polymers intertwined each other in the solid state. When the polymers in the solid state were annealed, F440/F540 increased and all of the fluorescence spectra became similar to that of monomer emission according to the arrangement change of the polymer chain. It is concluded that emission color changes of the polymers are mainly derived from intermolecular interaction between AB fluorophores in the inter-polymer chains. We have demonstrated that poly(ABSt-co-St) forms excellent homogeneous fluorescence polymer films. In contrast, the mixture of methoxy AB (ABOMe) and poly(St) undergoes crystallization even in the low content of ABOMe in poly(St).

Photoluminescence emission from nanostructured porous preparations of CdS-ZnTiO3 assembled nanoparticles.

This study reports the structural and optical properties of CdS/ZnTiO3 nanocomposites prepared using a chemical bath and different titanate concentrations. Commercial ZnTiO3 nanoparticles were introduced into a chemical bath that had been used to produce CdS semiconductor nanoparticles (NPs). Here, the growing CdS crystallites precipitated onto the suspended zinc titanate NPs. X-ray diffraction patterns revealed that samples of CdS/ZnTiO3 nanopowders were made of cubic ZnTiO3 and hexagonal CdS wurtzite. The morphology of the particles was studied using transmission electron microscopy and scanning electron microscopy images. These images demonstrated the different characteristics of the CdS/ZnTiO3 nanocomposites and their dependence on titanate concentration when placed into the CdS-growing solution. Photoluminescence spectra showed three main emission bands for the electron transitions in the CdS/ZnTiO3 composite. This composite produced three photoluminescence bands, the intensities of which depended on composite shape, which in turn depended on the relative concentrations of CdS and ZnTiO3 .

Формирование гетероперехода II типа в полупроводниковой структуре InAsSb/InAsSbP

The results of studying the electroluminescent and current-voltage characteristics of the n-InAs/n-InAsSb/p-InAsSbP heterostructure grown by gas-phase epitaxy from organometallic compounds are presented. Intense electroluminescence was detected in the spectral range 0.23–0.29 eV at the temperature T = 77 K. The position of the maximum of the main emission band (h ~ 0.24 eV) showed a noticeable “blue” shift with increasing applied forward bias. Based on the performed studies, it was concluded that there is a staggered type II heterojunction at the InAs0.84Sb0.16/InAs0.32Sb0.28P0.40 heterointerface, which is confirmed by the results of the calculation of the energy band diagram.

Electronic structure, energy transfer mechanism and thermal quenching behavior of K3YB6O12:Dy3+, Eu3+ phosphor

Rare-earth ions activated K3YB6O12:Dy3+, Eu3+ phosphors were successfully prepared by a high temperature solid state reaction. The electronic structure of K3YB6O12 was estimated by density functional theory. Under the excitation of ultraviolet light, K3YB6O12:Dy3+ presented two main emission bands with peaks at 487 nm and 576 nm, belonging to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions respectively. The variable emitting color was observed after co-doping with Eu3+ associated with the energy transfer between Dy3+ and Eu3+, which was confirmed by analyzing the photoluminescence spectra and the luminescence decay curves. Using the Dexter's theory and the Reisfeld's approximation, the energy transfer process from Dy3+ to Eu3+ can be explained by quadrupole-quadrupole interaction. Furthermore, the temperature dependent emission spectra of K3YB6O12:Dy3+, Eu3+ confirmed that the luminous intensity of 576 nm at 493 K was 78% of the initial value, suggesting the good emission thermal stability. It was worth noting that as the temperature increases, the emission intensity of Eu3+ hardly changed, which was different with that of Dy3+. Different thermal quenching phenomena of Dy3+ and Eu3+ were depicted in the coordinate graphics.

Synthesis and luminescence characterization of Pr3+, Gd3+ co‐doped SrF2 transparent ceramics

AbstractPr3+, Gd3+ co‐doped SrF2 transparent ceramic, as the potential material for visible luminescent applications, was prepared by hot‐pressing of precursor nanopowders. The microstructure, phase compositions, and in‐line transmittance, as well as the photoluminescence properties were investigated systematically. Highly optical quality Pr,Gd:SrF2 transparent ceramic with nearly pore‐free microstructure was obtained at 800°C for 1.5 hours. The average in‐line transmittance of the x at.% Pr, 6 at.% Gd:SrF2 (x = 0.2, 0.5, 1.0, 2.0) transparent ceramics reached to 87.3 % in the infrared region. The photoluminescence spectra presented intense visible light emissions under the excitation of 444 nm, the main intrinsic emission bands located at 483 and 605 nm, which were attributed to the transitions of Pr3+: 3P0 → 3H4 and 1D2 → 3H4, respectively. With the co‐doping of Gd3+ ions, the emission intensity of the Pr:SrF2 transparent ceramic was greatly enhanced. All the emission bands of x at.% Pr, 6 at.% Gd:SrF2 transparent ceramics exhibited the highest luminescence intensity with the 1.0 at.% Pr3+ doping concentrations, whereas the lifetimes decreased dramatically with the Pr3+ doping contents increasing from 0.2 to 2.0 at.% due to its intense concentration quenching effect. The 1 at.% Pr, 6 at.% Gd:SrF2 transparent ceramic is a promising material for visible luminescent device applications.

Spectroscopic Characteristics of Polymer Films Activated by a Supramolecular Nanodiamond Complex of Europium with Bathophenanthroline

New high efficiency luminescence films that convert UV radiation in a wavelength range of 220–410 nm into the europium ion luminescence are first obtained using a supramolecular diamond-containing complex of europium(III) with bathophenanthroline. The films allow the degree of radiation monochromaticity to be tuned at the main band of Eu3+ ions, centered at 615 nm. The excitation spectrum profile, as well as the half-width of the main emission band at 615 nm (a 5D0–7F2 transition) and the quantum yield values (in a range of ~0.3–0.8), is found to depend on the type of matrix material. The optical materials presented in the present work are promising candidates for the design of various light-emitting devices, such as screens, indicators, solar concentrators, organic LEDs, and laser media.

Preparation of ZrO2-doped Nd3+: Y2O3 transparent ceramic and the corresponding characteristic of luminescence

Highly transparent ZrO2-doped Nd3+: Y2O3 ceramics were prepared by a simple shaping approach followed by a low-cost sintering and simple sintering approach: Slip casting and vacuum pressureless sintering (1840 × 8 h), with the Nd3+ doping concentration of 0.5 at%, 1.0 at%, 1.5 at%, and 2.0 at% respectively. The in-line transmission (IT) of Nd3+ doped sample at 0.5 at% is the highest at 1074 nm, which is 80.7%, equivalent to 99.6% of the theoretical IT. The 1.0 at% Nd3+-doped sample has strong absorption peaks at 746, 806, 821 and 893 nm. The strongest absorption peak is 821 nm, and the two absorption peaks at 806 and 821 nm correspond to the transition of 4I9/2-[4F5/2+2H (2)9/2]. Under the excitation of 808 nm LD, there are three main emission bands, located at 870–950 nm, 1047–1137 nm and 1310–1460 nm, corresponding to the energy level transitions of 4F3/2-4I9/2, 4F3/2-4I11/2 and 4F3/2-4I13/2, respectively. The main emission peak at 1074 nm corresponds to the 4F3/2-4I11/2 energy level transition. The fluorescence lifetime can be tuned with Nd3+ doping concentration.

Effect of Yb3+ concentration on the green-yellow upconversion emission of SrGe4O9:Er3+ phosphors

Abstract This work presents the structural, morphological and luminescent, properties of SrGe4O9 (SGO):Er3+,Yb3+ phosphors. These phosphors were synthesized by simple combustion synthesis and subsequently annealed at 1100 °C. The XRD patterns revealed that all the SGO samples doped with Yb3+ concentrations from 2 to 10 at.% presented a trigonal pure phase (the Er3+ concentration was fixed to 1 at.%). The morphology of the SGO samples was analyzed by scanning electron microscopy and found that they are formed by microparticles with irregular shapes and average sizes in the range of 0.2 μm–3 μm. The luminescence measurements of the SGO:Er3+,Yb3+ samples showed the presence of two main emission bands at 551 nm (green) and at 662 nm (red) under excitation at 980 nm, which are associated to Er3+ transitions. For Yb concentration of 2 and 3 at.% the green band dominated, but the red band became more intense for Yb concentrations above 5 at.%. As result, the CIE coordinate changed from the green to the yellow region. The increase for the Yb content from 2 to 10 at.% also enhanced of the NIR emission of Er3+ ≈5 times and the maximum upconversion emission was observed for 8% of Yb concentration. Further, the surface of the SGO samples was analyzed by the FTIR technique in order to find OH groups which are common luminescent quenching centers, but these groups were not detected on the samples. Since the SGO samples presented tunable emission, absence of OH groups on their surface and stable crystalline structure for high Yb dopant concentrations, they could be good candidates as phosphors for solid state lighting or displays applications.

Crystal structure and luminescence studies of microcrystalline GGG:Bi3+ and GGG:Bi3+,Eu3+ as a UV-to-VIS converting phosphor for white LEDs

The paper contains detailed crystal structure and photoluminescence studies of the Bi3+ and Bi3+-Eu3+ co-doped Gd3Ga5O12 (GGG) garnet. The studied materials have been synthesized in the form of microcrystalline powders by the common solid-state reaction method. Precise crystal structure parameters were derived from the X-ray powder diffraction data. Photoluminescence studies were done by the steady-state and time-resolved techniques in the 4.2–400 K temperature range. The studied materials show no UV luminescence caused by electronic transitions of a Bi3+ ion. The observed luminescence in visible is interpreted by excitons localized around Bi3+ ions. In particular, two emission bands located at 2.55 eV (486 nm) and 2.05 eV (605 nm) at 4.2 K were revealed. The main emission band at 2.55 eV is attributed to the triplet relaxed state of excitons localized around single (regular) Bi3+ ions, whereas the weaker band at 2.05 eV is related to some associates of a single Bi3+ ion with a crystal lattice defect. The performed studies for Bi3+-Eu3+ co-doped samples indicate that the energy transfer from Bi3+ to Eu3+ is radiative and is caused by reabsorption of the Bi-related exciton emission by Eu3+ ions. The studied materials were also characterized as a single-phase converting phosphor for near-UV excited white LEDs. The possibility of the emission color tuning from blue to orange-red at UV excitation by the way of changing of Bi3+ and Eu3+ concentrations was shown.

Effect of annealing on UV‐visible absorption and photoluminescence behavior of liquid phase deposited TiO2 nanorods

AbstractIn this work, anatase and rutile TiO2 nanorods were fabricated using one‐step liquid phase deposition process, followed by heat treatment in the range 300‐800°C. The direct and indirect band gap of the TiO2 nanorods was estimated form optical absorption data which illustrated a red shift at higher temperatures owing to the different nature of excitons in anatase and rutile phases. The photoluminescence (PL) spectra revealed the presence of two main emission bands consisting of four peaks. It was found that two high‐energy peaks located at 2.95‐3.30 eV could be generated from exciton transitions from the conduction band to the valence band of TiO2 nanorods, while two low‐energy peaks located at 2.43‐2.64 eV may arise from surface state transitions. The PL intensity firstly increased with temperature and at 500°C reached a maximum value, then decreased through increasing temperature up to 800°C. These variations in the intensity of PL emission could be explained in terms of changes in phase structure, crystallinity, and amount of the oxygen vacancies, which are all dependent to the annealing temperature based on X‐ray diffractometer and X‐ray photoelectron spectrometer studies. These results indicated that annealing temperature allows to manipulate the properties of TiO2 nanorods for opto‐electronic applications.

The creation spectra of intrinsic emission of a [formula omitted] crystal irradiated by ultraviolet photons

The spectra of creation and excitation of the main emission bands of 3.7–3.8 eV and 3.0–3.1 eV at 15 K and 300 K were measured by vacuum-ultraviolet spectroscopy. The minimum creation energy of the primary luminescence 3.7–3.8 eV, is about 5 eV. Based on the measurement of the excitation spectrum of the emission band 3.7–3.8 eV, three sub-bands inside the valence band were detected. Emission of 3.7–3.8 eV is created by recombination of electrons in the conduction band with localized holes relaxed from three sub-bands above top of the valence band.

Site-Bi3+ and Eu3+ dual emissions in color-tunable Ca2Y8(SiO4)6O2:Bi3+, Eu3+ phosphors prepared via sol-gel synthesis for potentially ratiometric temperature sensing

A series of Ca2Y8(SiO4)6O2 (CYSO):Bi3+, Eu3+ phosphors were prepared via a Pechini-type sol-gel reaction method. The refinement results for CYSO:Bi3+, Eu3+ phosphors implied that they had a pure phase. The blue-green emission ascribed to Bi3+ 3P1→1S0 transition was generated upon UV excitation in Bi3+ singly-doped CYSO samples. Spectral analysis indicated that two main emission bands around 414 and 494 nm correspond to two kinds of Bi3+ occupying the crystal lattices of 4f and 6 h available for Y3+ in CYSO, denoted as Bi3+(2) and Bi3+(1), respectively. A broad spectral overlap between Bi3+ emission and Eu3+ excitation spectra implied the existence of energy transfer from Bi3+ to Eu3+ ions in CYSO:Bi3+,Eu3+, which resulted in the tunable emission color from blue-green to red. The energy transfer mechanism from Bi3+ to Eu3+ ions was determined to be a dipole-quadrupole interaction. Moreover, the quite different luminescence thermal quenching behaviors between Bi3+(2) and Eu3+ showed good temperature sensing properties with a temperature range of 298–523 K by analyzing the temperature sensitivity of the fluorescent intensity ratio [Bi3+(2)/Eu3+(612)]. The maximum absolute and relative sensitivities reached as high as 0.07174 K-1 (523 K) and 0.958% K−1 (423 K), which can be compared to the highest values of 0.015 K-1 and 1.1%K−1 in reported optical thermometric materials before, respectively, based on the thermally coupled level (TCLs) of Er3+. Meanwhile, the luminescence thermal quenching mechanism in this system was investigated in detail. Results inspire that a feasible method based on site-Bi3+ and Eu3+ emissions is potential as one of candidate strategies for developing novel ratiometric optical thermometry materials.

Down- and up-conversion photoluminescence of ZrO2:Ho3+ and ZrO2:Ho3+/Yb3+ coatings formed by plasma electrolytic oxidation

This paper discusses ZrO2:Ho3+ and ZrO2:Ho3+/Yb3+ coating formation by the plasma electrolytic oxidation (PEO) of zirconium in alkaline electrolyte containing Ho2O3 and Ho2O3/Yb2O3 particles, respectively. The morphology, chemical and phase composition, as well as down- and up-conversion photoluminescence (PL) of the coatings, were investigated. Down-conversion PL emission spectra of ZrO2:Ho3+ excited by 280 nm radiation are composed of broad PL band associated with ZrO2 host and bands corresponding to f–f transitions of Ho3+. The main PL emission bands of Ho3+ at around 540 nm and 550 nm are assigned to 5F4→5I8 and 5S2→5I8 transitions, respectively. The down-conversion PL intensity of ZrO2:Ho3+ excited by 450 nm radiation (transition 5I8→5G6) strongly depends on the concentration of Ho3+ incorporated into ZrO2 coatings. That is, it depends on the duration of the PEO process and concentration of Ho2O3 particles in electrolyte. PL intensity increases with rising Ho3+ concentration in ZrO2 coatings, reaching a maximum Ho:Zr ratio of about 18⋅10−3 and shows concentration quenching for higher values. Excitation of ZrO2:Ho3+/Yb3+ coatings by 980 nm laser diode results in the appearance of a strong green (5F4,5S2→5I8), weaker red (5F5→5I8), and NIR (5F4,5S2→5I7) up-conversion emissions. An increase of the PL intensity with increasing Yb3+ concentration indicates an efficient transfer of energy from excited Yb3+ ions to Ho3+ ions.

Photosensitiser functionalised luminescent upconverting nanoparticles for efficient photodynamic therapy of breast cancer cells.

Photodynamic therapy (PDT) is a well-established treatment of cancer in which cell toxic reactive oxygen species, including singlet oxygen (1O2), are produced by a photosensitiser drug following irradiation of a specific wavelength. Visible light is commonly used as the excitation source in PDT, although these wavelengths do have limited tissue penetration. In this research, upconverting nanoparticles (UCNPs) functionalised with the photosensitiser Rose Bengal (RB) have been designed and synthesised for PDT of breast cancer cells. The use of UCNPs shifts the required excitation wavelength for the production of 1O2 to near infrared light (NIR) thus allowing deeper tissue penetration. The system was designed to maximise the production of 1O2via efficient Förster resonance energy transfer (FRET) from the UCNPs to the photosensitiser. Highly luminescent NaYF4:Yb,Er,Gd@NaYF4 core-shell UCNPs were synthesised that exhibited two main anti-Stokes emission bands at 541 and 652 nm following 980 nm irradiation. RB was chosen as the photosensitiser since its absorption band overlaps with the green emission of the UCNPs. To achieve efficient energy transfer from the nanoparticles to the photosensitiser, the functionalised UCNPs included a short l-lysine linker to attach the RB to the nanocore yielding RB-lysine functionalised UCNPs. The efficient FRET from the UCNPs to the RB was confirmed by luminescence lifetime measurements. The light emitted by the UCNPs at 541 nm, following excitation at 980 nm, generates the 1O2via the RB. Multi-photon and confocal laser scanning microscopies confirmed the internalisation of the RB-lysine-UCNPs by SK-BR-3 breast cancer cells. Cell viability studies revealed that the RB-lysine-UCNPs induced low dark toxicity in cells prior to PDT treatment. Importantly, following irradiation at 980 nm, high levels of cell death were observed in cells loaded with the RB-lysine-UCNPs. Cell death following PDT treatment was also confirmed using propidium iodide and confocal microscopy. The high drug loading capacity (160 RB/nanoparticle) of the UCNPs, the efficient FRET from the UCNPs to the photosensitiser, the high level of accumulation inside the cells and their PDT cell kill suggest that the RB-lysine-UCNPs are promising for NIR PDT and hence suitable for the treatment of deep-lying cancer tumours.

Спектроскопические свойства полимерных пленок, активированных супрамолекулярным наноалмазным комплексом европия с батофенантролином

For the first time, using the supramolecular diamond-containing europium (III) complex with bathophenanthroline, new luminescent films were obtained, converting UV radiation in the wavelength range of 220–410 nm with high efficiency to luminescence of europium ions, with the ability to control the degree of monochromaticity of radiation in the main emission band of Eu3+ ions with maximum of 615 nm. It was found that the shape of the excitation spectra, the half-width of the main emission band of 615 nm (transition 5D0–7F2), the values of quantum yields (within ~ 0.3–0.8) depend on the type of matrix material. The proposed optical materials can be used in the development of various light-emitting devices: screens, indicators, solar concentrators, organic light-emitting diodes, laser media.

Photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation

In the present work, down- and up-conversion photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation of zirconium in electrolyte containing Er2O3 and Yb2O3 particles were investigated. Down-conversion PL analysis shows that emission spectra of ZrO2:Er3+/Yb3+ coatings excited with 280 nm radiation are composed of broad PL band related to ZrO2 host and bands assigned to f-f transitions of Er3+. The main PL emission bands of Er3+ at around 548 nm and 560 nm are related to 4S3/2→4I15/2 transition. PL excitation spectra monitored at 548 nm feature broad band in the region from 250 nm to 350 nm which is associated with the electron transfer transition from 2p orbital of O2− to 4f orbital of Er3+ and transitions of ZrO2. On the other hand, bands in PL excitation spectra ranging from 350 nm to 535 nm are related to 4f transitions of the Er3+ from the ground state 4I15/2 to higher energy levels. Down-conversion PL intensity decreases with increasing concentration of Yb3+ in coating due to energy transfer from Er3+ to Yb3+. ZrO2:Er3+/Yb3+ coatings show intense green (4S3/2→4I15/2) and red (4F9/2→4I15/2) up-conversion PL emission under the excitation with a 980 nm diode laser. With increasing Yb3+ concentration red up-conversion PL intensity increases more rapidly with respect to green emission, because red up-conversion PL intensity strongly depends on Yb3+ concentration, i.e. 4F9/2 state of Er3+ is directly excited by energy transfer from excited Yb3+.

Reprint of “In-situ luminescence studies of silica glass during low energy H+, He+ and O+ irradiation”

Silica glass can be used as optical windows of nuclear facilities, optical fibers, and different electronic components in high radiation level environments. The study of structural changes and other effects created by ion irradiation in silica glass is important both for the performance study in above applications and the mechanical study of ion implantation modifications of silica for manufacture advanced materials. A low-energy ion beam induced luminescence (IBIL) set-up was developed at the 200 kV Ion Implanter of Beijing Normal University to measure the dynamic process involved in the damage creation of different materials. In-situ luminescence measurements were performed on silica glasses under the irradiation of 40 keV, 100 keV, 180 keV H+, He+ and 100 keV, 180 keV O+ at room temperature. The evolution of two main emission bands under 100 keV H+, He+, and O+ irradiation was discussed. The IBIL kinetics studied in this work was different to that observed for MeV-ions. The saturated luminescence induced by H+, He+ presented almost linear relationship with electronic energy deposition of incident ions. The roles of electronic and nuclear stopping power at different ion energies were discussed to explore the origin of luminescence. Ex-situ optical absorption spectra were measured to monitor optical properties and point defects concentration evolution with H+ and O+ fluence.