Transition Of Eu Research Articles

UV-vis induced emission-color switching in Eu-doped BaNa2MgP2O8

This paper demonstrates emission-color change of BaNa2MgP2O8: Eu through photoredox reactions of dopant europium ions. Europium doped BaNa2MgP2O8 was prepared by high-temperature solid state reaction in air. Under UV excitation, Eu-doped BaNa2MgP2O8 exhibited weak mixed-color emission involving orange and blue components. They were derived from 4 f6-4 f6 intraconfigurational electron transition in Eu3+ and 4 f65d1-4 f7 interconfigurational electron transition in Eu2+, respectively. Since Eu3+ ⇄ Eu2+ photoredox reactions were both facilitated by UV–vis photostimulation, Eu3+/Eu2+ ratio approached to an equilibrium value depending on the stimulation wavelength. The resultant emission color was continuously varied by stimulation light. Optical absorption character and ESR spectroscopy revealed that the photoredox reactions in Eu were caused by electron transfer between Eu and PO43- within BaNa2MgP2O8.

Luminescence and microstructural characteristics of Eu2O3-doped SrAl2O4 single crystals

Single crystals of SrAl2O4 prepared with 0.2–2.0 mol% Eu2O3 were synthesized using the optical floating zone method using ceramic rods that had been prepared under reducing conditions to favor conversion of Eu3+ to Eu2+. Samples were then characterized by a combination of X-ray diffraction (XRD), X-ray photoelectron (XPS), positron annihilation, electron paramagnetic resonance (EPR), photoluminescence excitation (PLE) and photoluminescence (PL) spectroscopic techniques, and their excited state lifetimes were measured. XRD showed that the crystal samples were all in the monoclinic phase. EPR and PL techniques indicated that they contained Eu2+, although XPS indicated that the Eu3+ reduction was only ∼50%. Positron annihilation spectroscopy demonstrated that all of the samples contained a considerable number of defects that act as positron traps, and were influenced by the amount of Eu2O3 used in the crystal synthesis. These defects did not show an EPR signal, which suggests that they may correspond structural vacancies, possibly due to the presence of cation vacancies as a result of incorporation of some Eu3+ in the divalent cation sites. However, EPR did reveal a small amount of anionic paramagnetic defects, and showed a progressive broadening of the Eu2+ resonance for crystals synthesized with Eu2O3 concentrations >0.5 mol%. The intensity of the PLE spectra increased with Eu2O3 concentration, and the relative proportions of the peaks at 3.62 eV (360 nm) and 3.13 eV (417 nm) changed with Eu2O3 concentration. The PL spectra showed a broad green emission peak at 2.52 eV (518 nm), which is attributed to 4f65d-4f7 charge transfer transitions in Eu2+. Both its intensity and fluorescence decay time increased with Eu2O3 concentration, reached a maximum with the sample prepared with 1.5 mol% Eu2O3, then decreased with higher Eu2O3 concentrations.

Activation of zirconia nanophosphors with Eu3+ to demonstrate multifunctional optical applications

Pristine ZrO2 and Eu3+ activated ZrO2 nanophosphors were synthesized by urea assisted solution combustion method. The synthesized nanophosphors were characterized by Powder X-ray diffraction (PXRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and photoluminescent (PL) spectroscopy for their structural, morphological, surface, vibrational and luminescent studies. The crystal structure and phase transformation were studied by PXRD which was supported well by XPS and FTIR results. FESEM studies reveal the porous morphology due to the combustion synthesis. XPS results reveal that activator Eu was predominantly present in the +3 oxidation state in the nanpohosphor. PL emission spectra of Eu3+ activated zirconia show characteristic reddish emission corresponding to 5D0→7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+ ion. Photometric parameters were calculated to check the possible application of the nanophosphors for solid-state lighting. The high color purity ∼94% of the synthesized phosphors indicates their application in phosphor-converted white light-emitting diodes (pc-wLEDs). The fluorescence intensity ratio (FIR) of non-thermally coupled levels 5D0→7F2 and 5D0→7F3 were used to calculate the temperature. At 623 K, a maximum relative and absolute sensitivity of 0.11% K−1, and 0.76% K−1 was observed. The possible anti-counterfeiting application of ZrO2:Eu3+ has been tested using a standard screen-printing procedure. The high contrast fingerprints of the synthesized phosphor taken under near-ultraviolet (n-UV) light indicate that the synthesized phosphor can be used for latent fingerprinting applications. All these results indicate that Eu3+ activated zirconia has the potential to be used as multifunctional material.

Fluorescent Eu3+/Tb3+ Metal-Organic Frameworks for Ratiometric Temperature Sensing Regulated by Ligand Energy.

This work presents three series of Eu/Tb metal-organic frameworks (MOFs) containing benzophenone-4,4'-dicarboxylic acid (H2BPNDC), 4,4'-dicarboxydiphenyl ether (H2OBA), and terephthalic acid (H2BDC) as the ligands. Eu/Tb MOFs have the same structural features in that their 3D frameworks are simplified as 2,3,10-connected {42.6}2{46.618.819.102}{4}2 topological networks. The solid-state fluorescence spectra of three Eu/Tb MOF series are attributed to the combined emissions of 5D0 → 7FJ (J = 1-4) transitions in Eu3+ and 5D4 → 7FJ (J = 6-5) transitions in Tb3+. The nEu:nTb of Eu/Tb MOFs is optimized as 1:69 based on the relationships between ITb(545)/IEu(614) and nEu:nTb; that is, Eu0.0143Tb0.9857-L (L = BPNDC2-, OBA2-, and BDC2-) were selected to carry out the following temperature (T)-sensing tests. The fluorescence mechanism of Eu0.0143Tb0.9857-L can be explained by a ligand-to-metal charge transfer combined with an intermetallic Tb3+ → Eu3+ energy transfer. The T-dependent fluorescence indicates linear relationships with sensitivities of 1.85% K-1 for Eu0.0143Tb0.9857-BPNDC, 6.49% K-1 for Eu0.0143Tb0.9857-OBA, and 0.28% K-1 for Eu0.0143Tb0.9857-BDC. The influence of T on the lowest excited triplet energy levels (T1 values) of the ligands reveals that the ligand energy regulation impacts their fluorescence properties, including the sensitivity, fluorescence quenching rate, quantum yield, and fluorescence lifetime. This shows that Eu0.0143Tb0.9857-BPNDC is sufficiently sensitive to T, making it applicable in noncontact T measurements.

Photoluminescence of Europium in ZnO and ZnMgO thin films grown by Molecular Beam Epitaxy

In this work, luminescence properties of Europium doped ZnO and ZnMgO thin films grown on a-oriented (11–20) sapphire substrates by oxygen plasma assisted Molecular Beam Epitaxy method are studied. The concentrations and distributions of Eu atoms in the respective hosts were analysed using Secondary Ion Mass Spectrometry, which confirmed successful doping around the level of ∼1%. Optical properties of the samples were investigated by room temperature photoluminescence (PL) and Photoluminescence excitation (PLE) measurements. The PL data suggest the co-existence of 2+ and 3+ ionic states of Eu in the as-grown samples. It has been observed that alloying Mg with ZnO increases the intensity of the 5D0→7FJ intra-4f-shell emission of Eu3+ ions by an order of magnitude even in as-grown samples. The samples were also annealed at 800 °C in oxygen flux and re-measured to see changes in the PL. After annealing, all the emission lines due to the 5D0→7FJ intra-4f-shell transitions of Eu3+ were strongly enhanced, whereas the bands attributed to Eu2+ were found to diminish or disappear completely. The results of PLE measurements point to efficient host to dopant energy transfer in the studied films.

Photoluminescence investigation of Eu2+-doped BaSO4

Eu doped BaSO4 was prepared by the recrystallization method and characterization of the material was done by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques. From the XRD pattern of Eu doped BaSO4 com- pound, it was found that the prominent phase formed was BaSO4 and traces of other phases were very weak and the result of FTIR spectrum of BaSO4:Eu shows that the sulfur-oxygen stretch was found at around 1100 cm−1. The room-temperature PL spectra of the Eu doped BaSO4 sample showed one peak centered at 374 nm, which is the characteristic emission of Eu2+ ion. This emission band at 374 nm corresponds to the 4f6 5d 4f7 (8S7/2) transitions of Eu2+ ions. The excitation spectrum taken at the wave- length 374 nm extends over a wide range of wavelengths from 220–350 nm with a strong peak at around 260 nm. Furthermore, the present sample shows good crystal quality and high photoluminescence sensitivity. Hence our results suggest possible potential applications of Eu doped BaSO4 phosphor in optoelectronic devices.

Robust magnetic-field effect on spin-reorientation in Eu3+-modified TmFeO3 single crystal

Strongly correlated electron systems are an excellent platform for functional materials. Here, we present a strong magnetic effect in the Eu3+-doped TmFeO3 single crystal, where half of the Tm3+ sites are replaced by Eu3+ dopants in the orthorhombic lattice of TmFeO3 (Tm0.5Eu0.5FeO3). We demonstrated by combining the dc-magnetic susceptibility χ(T) as well as magnetization isotherm M(H), that the temperature dependent magnetization results under tiny change in magnetic field (H) shows the evidence for the formation of such remarkable effects due to Tm3+ substituted with Eu3+ ion in TmFeO3. Interestingly, Eu3+ doping protects the antiferromagnetic (AFM) spin-reorientation transition along crystallographic c-axis as observed by a sharp transition at TSR = 90 K, similar as parent TmFeO3. Further, an external applied field (H) of 500 Oe is enough to fully suppress the spin-reorientation transition in Eu3+ doped TmFeO3. We emphasize that the transition from almost free-state of Tm3+ spin to AFM state changes by 90 K at such low magnetic field. Experimentally observe significant changes in terms of shift in the magnetic transition (SRT) under an applied very low magnetic field due to Eu3+ doping in TmFeO3 lattice is truly robust effect.

Characterization, Luminescence and Optical Resonant Modes of Eu-Li Co-Doped ZnO Nano- and Microstructures

ZnO nano- and microstructures co-doped with Eu and Li with different nominal concentrations of Li were grown using a solid vapor method. Different morphologies were obtained depending on the initial Li content in the precursors, varying from hexagonal rods which grow on the pellet when no Li is added to ribbons to sword-like structures growing onto the alumina boat as the Li amount increases. The changes in the energy of the crystallographic planes leading to variations in the growth directions were responsible for these morphological differences, as Electron Backscattered Diffraction analysis shows. The crystalline quality of the structures was investigated by X-ray diffraction and Raman spectroscopy, showing that all the structures grow in the ZnO wurtzite phase. The luminescence properties were also studied by means of both Cathodoluminescence (CL) and Photoluminescence (PL). Although the typical ZnO luminescence bands centered at 3.2 and 2.4 eV could be observed in all cases, variations in their relative intensity and small shifts in the peak position were found in the different samples. Furthermore, emissions related to intrashell transitions of Eu3+ ion were clearly visible. The good characteristics of the luminescent emissions and the high refraction index open the door to the fabrication of optical resonant cavities that allow the integration in optoelectronic devices. To study the optical cavity behavior of the grown structures, µ-PL investigations were performed. We demonstrated that the structures not only act as waveguides but also that Fabry–Perot optical resonant modes are established inside. Quality factors around 1000 in the UV region were obtained, which indicates the possibility of using these structures in photonics applications.

Designing Optical Thermometers Using Down/Upconversion Ca14Al10Zn6O35: Ti4+, Eu3+/Yb3+, Er3+ Thermosensitive Phosphors.

Down/upconversion Ca14Al10Zn6O35 inorganic phosphors codoped with Ti4+/Eu3+ or Yb3+/Er3+ were prepared. The crystal structure and downconversion luminescence properties of Ca14Al10Zn6O35:Ti4+, Eu3+ phosphors were studied in detail. Ti4+ and Eu3+ occupied Al3+ and Ca2+ sites in the host lattice, respectively. Under the excitation of 273 nm, the emission peak in the 300-570 nm band originated from the 2T2 → O2- transition of Ti4+. The f-f transition of Eu3+ ions generated multiple peaks in the 570-800 nm range. The emission intensity of Ti4+ and Eu3+ ions can be used as a fluorescence intensity ratio (FIR) signal. Based on the FIR technology, the maximum relative sensitivity (Sr) and the minimum temperature uncertainty (δT) reached 1.41% K-1 and 0.07 K, respectively. Meanwhile, the temperature-sensing behaviors were explored by the temperature-dependent upconversion spectra of Er3+- and Yb3+-codoped Ca14Al10Zn6O35 phosphors. Based on the fluorescence intensity ratio of thermal coupling levels (Er3+:2H11/2/4S3/2), the maximum Sr and minimum δT of upconversion phosphors reached 1.28% K-1 and 0.08 K in the temperature range of 293-473 K, respectively. Ca14Al10Zn6O35:Ti4+/Eu3+ (Yb3+/Er3+) phosphors realize temperature sensors with higher relative sensitivity, and it is a good candidate material for optical temperature measurement.

Energy transfer mechanism in Eu3+ doped tin oxide nanophosphors for red solid state lighting

A europium doped tin oxide (SnO2:Eu3+) nanophosphor is prepared by using of solution-combustion process with a variation in the doping amount of Eu3+. The results recorded by X-ray diffraction are established that SnO2: Eu3+ has a polycrystalline tetragonal structure without phase alteration for each concentration of Eu3+. The undoped SnO2 nanoparticles showed only defects related emission while emission due to the f→f transitions of Eu3+ ion is observed upon doping. The optimized photoluminescent intensity was observed for 3 mol% Eu3+. The life-time measurement of Eu3+ -doped SnO2 associated with major emission band located at 612 nm was monitored as 0.3 ms for the 3 mol% of Eu concentration. The present results reveal that Eu3+ -doped SnO2 nanoparticles may be used as a source of red light phosphor and this may be utilized for solid white light emitting application.

Using liquid phase precursor method to create a high-efficiency Ca<sub>2</sub>SiO<sub>4</sub>:Eu<sup>2+</sup> green-emitting phosphor

A standard solid-state reaction (SSR), a new fluid phase preparatory method utilizing LPP-SiO2(sol), and a water-based soluble silicone compound were employed to manufacture green Eu2+-based Ca2SiO4 phosphors liquid phase precursor (LPP-WSS). The generated phosphors feature large excitation spectra in the range of 225–450 nm and a strong green emission reaches the peak value at 502 nm owing to a 4f65d1→4f7(8S7/2) transition of Eu2+. These samples burned at 1100 1C produce the highest luminous intensity. The luminous properties of phosphors, which are manufactured by the liquid phase precursor LPP-WSS technique, were investigated at the range of 0.1-5.0 mol percent of Eu2+, with the maximum emission density observed at the value of 3.0 mol percent of Eu2+. The phosphors produced by the LPP-WSS technique exhibited a more uniform phase dispersion and higher luminous strength than those produced using the other procedures, according to a detailed report based on numerous characterizations. As a result, Ca2SiO4:Eu2+ has an indisputable possibility in white light-emitting diodes WLEDs and fluorescent lighting.

Dazzling Red-Emitting Europium(III) Ion-Doped Ca2LaHf2Al3O12 Garnet-Type Phosphor Materials with Potential Application in Solid-State White Lighting.

Bright red-emitting phosphors with high color purity and high photoluminescence quantum yield (PLQY) are highly demanded for the fabrication of high-performance warm-white light-emitting diodes (LEDs). Herein, we demonstrated a novel efficient Eu3+-activated Ca2LaHf2Al3O12 garnet phosphor with excellent luminescence properties for near-ultraviolet (near-UV) excited warm-white LEDs. The Ca2LaHf2Al3O12:Eu3+ phosphors exhibited an intense excitation spectrum in the near-UV region with a maximum around 394 nm, and they produced dazzling red luminescence peaking at 592, 614, 659, and 711 nm due to the 5D0 → 7FJ (J = 1-4) transitions of Eu3+ ions when the excitation wavelength was set at 394 nm. Luminescent properties have been studied as a function of Eu3+ doping concentration, and the highest emission intensity was achieved at 50 mol % Eu3+, while the dipole-dipole interaction brought the concentration quenching effect. The Ca2LaHf2Al3O12:50%Eu3+ sample exhibited CIE chromaticity coordinates of (0.6419, 0.3575) with a color purity of 92.7%, and its PLQY was measured to be 64%. The thermal stability and activation energy of Ca2LaHf2Al3O12:50%Eu3+ phosphors were also discussed and analyzed. Finally, we made a near-UV chip-based white LED device in which the Ca2LaHf2Al3O12:50%Eu3+ phosphor was utilized as a red ingredient. A bright warm-white light emission was realized from this LED device under 80 mA driving current, accompanied by a high color rendering index (CRI) of 88.3, a low correlation color temperature of 3853 K, and good CIE chromaticity coordinates of (0.3909, 0.3934). These results revealed that these red-emitting Ca2LaHf2Al3O12:Eu3+ phosphors have promising application prospect in near-UV-excited warm-white LEDs with high a CRI.

(INVITED)Laser-driven white light with tunable low-colour temperature based on novel ZrO2-doped (Gd,Lu)2O3:Eu red-emitting transparent ceramics

Novel red-emitting ZrO2-doped (Gd,Lu)2O3:Eu transparent fluorescent ceramics were fabricated via a vacuum sintering method. The f–f transitions of Eu3+ in the ZrO2-doped (Gd,Lu)2O3:Eu transparent fluorescent ceramics have much higher intensity than the charge-transfer band (CTB) excitation, hence can be efficiently excited with near-UV light and blue light for white LED applications. The YAG:Ce phosphor was used to prepare a coating on the surface of the transparent ceramics to prepare (Gd,Lu)2O3:Eu/YAG:Ce ceramic laminates as colour converters. XRD, SEM, UV–vis–NIR spectroscopy and PLE/PL were used to characterize the properties of the resultant phosphors, transparent ceramics and colour converters. The results showed that for the (Gd,Lu)2O3:Eu transparent ceramic, an appropriate reduction of the sintering temperature and time would reduce its optical transmittance while enhancing the red emission. Under the excitation of 465 nm laser light, the (Gd,Lu)2O3:Eu/YAG:Ce ceramic converter could generate ideal white light at various low colour temperatures, effectively making up for the deficiency of the low colour rendering index and high colour temperature caused by the lack of red light components in the solid-state lighting. The ceramic converters may have potential applications in laser lighting.

A high sensitivity dual-mode optical thermometry based on charge compensation in ZnTiO3:M (M = Eu3+, Mn4+) hexagonal prisms

Optical thermometer based on dual-mode fluorescence intensity ratiometric thermometry has been attracted more attention due to its higher sensitivity. In order to obtain optical thermal probe with high sensitivity, ZnTiO3 hexagonal prisms with hexagonal perovskite structure were fabricated by using self-assembly method, and Al3+ ions were introduced into the crystal lattices of ZnTiO3 doped with Eu3+/Mn4+ to improve the optical properties. The emission intensity assigned to Eu3+ was enhanced about twice with the charge compensation of Al3+ between Eu3+ and Ti3+. While the luminescence ratio between the thermal coupled level of Eu3+ revealed poor temperature dependence property. The emission assigned to 2Eg→4A2g (713 nm) transition of Mn4+ revealed an huge thermal quenching. Using the luminescence ratio between 5D0→7F2 (5D0→7F1) transition of Eu3+ to 2Eg→4A2g of Mn4+, the higher relative sensitivity of 2.7 %K-1was obtained. The charge compensation of Al3+ improved the coordination and reduced the relative sensitivity, Sr =1.85 %K−1. The results suggested the potential application in optical temperature probes for ZnTiO3: Mn4+,Eu3+ phosphor.

Tunable luminescent chromaticity of CaZnOS: Bi3+, Eu3+ with white emitting based on energy transfer

A series of Bi3+ or Eu3+ ion single doped and Bi3+ and Eu3+ co-doped CaZnOS phosphors were synthesized via high temperature solid state method. Under ultraviolet (UV) excitation, CaZnOS: Bi3+ has an intense emission band ranged from 400 to 600 nm owing to the 3P1,0 → 1S0 transition of Bi3+. And CaZnOS: Eu3+ shows superior red emissions due to the characteristic 5D0 → 7FJ (J = 1, 2, 3, 4) transitions of Eu3+. Tunable emission chromaticity from cyan, white, yellow to red is obtained by regulating the proportion of Eu3+ in CaZnOS Bi3+, Eu3+. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed to be a quadrupole-quadrupole interaction based on the overlap of emission band of Bi3+ and excitation band of Eu3+ combined with the luminescent lifetime measurement. In addition, CaZnOS: 2.5 mol% Bi3+, 3 mol% Eu3+ phosphor with optimized concentrations has standard white light chromaticity coordinates (0.315, 0.323) and activation energy about 0.372 eV, which reflects its potential application in ultraviolet-chip excited white light emitting diodes (W-LEDs).

Surface engineered La2Zr2O7:Eu3+ nanophosphors: Luminescent based platform for latent fingerprints visualization and anti-counterfeiting applications

The advancements in the forensic technologies is still a constructive and requires continuous development and evaluation strategies are to be implement. In this regard, the present work deals with fabrication of novel surface modified red-emitting Eu3+ ions doped La2Zr2O7 nanophosphors and used for latent fingerprint visualization and data security applications. The powdered x-ray diffraction studies of the prepared samples confirm the disordered cubic phase. The photoluminescence emission spectra consist of intense emission peaks located at ∼ 576, 593, 613, 656 and 711 nm, ascribed to the 5D0 → 7FJ (J = 0 - 4) transitions of Eu3+ ions, respectively. The surface modified nanophosphors by oleic acid showed 2-fold enhancement in the emission intensity as compared to bare nanophosphors, which is due to effective intramolecular energy transfers from coordinated ligands to the activated Eu3+ ions, called the antenna effect. The photometric properties of the surface grafted nanophosphors exhibit pure red color with high purity. The visualized latent fingerprints using surface modified nanophosphor could reveal level 1 − 3 ridge characteristics, which is most reliable evidence for personal identification. High resolution images of developed latent fingerprints further validated the effective chemical binding between the hydrophobic nanophosphor and chemical constituents present in the fingerprints, which enables most authenticated sweat pores. The oleic acid grafted nanophosphors can be formulated into writable inks so that secret writings can be accomplished using a simple brush technique and decoded under ultraviolet light illumination. The followed surface modification strategy drastically improves the properties of the nanophosphor, which is real time choice for latent fingerprint development and anti-counterfeiting technologies.

Eu2+ activated novel eulytite Na3Bi5(PO4)6: Eu3+ phosphors: Enhanced luminescence and thermal stability for photonics application

For the first time, novel eulytite-like Eu2+/Eu3+: Na3Bi5(PO4)6 phosphor was synthesized via high temperature solid-state reaction method in reduction environment, and the structure, luminescence performances and thermal stability were investigated and discussed using various techniques. X-ray refinement diffraction and Raman spectra revealed the around 200 nm well-crystallized eulytite-type (I43d space group) phosphors were synthesized, and a diagram of crystal structure of Na3Bi5(PO4)6 was proposed. X-ray photoelectron spectroscopy analysis confirmed the co-existence of Eu2+ and Eu3+ ions which exhibited characteristic 4f65d→8S7/2 transition of Eu2+ and 7F0→5D0,1,2,3,4 transitions of Eu3+ ions. On the other hand, due to the activation of Eu2+, samples displayed good tunability on excited and emission behaviors under different excited laser. The JO parameters, emission cross-section, branching ratio and asymmetric ratio indicated that the Eu doping increased the covalency and asymmetry of host. Thermal quenching was studied and the reasons were discussed. Through the comparison of phosphors prepared in different conditions, the thermal stability& repeatability, radiative lifetime, color purity and activation energy were remarkably superior due to the Eu doping and in particularly Eu2+ activation. Finally, the energy level and CIE chromaticity diagrams were plotted to explain the mechanism of Eu2+ activation and energy transfer between Eu2+ and Eu3+ ions. The 0.5%Eu doped Na3Bi5(PO4)6 exhibited promising tunable red-emission performance with quantum efficiency of 92%, activation energy of 0.24 eV, red color purity of 93.74% and very low non-radiative transfer ratio 44.20 s−1 with smaller CCT (<2200 K).

Porous Silicon Nanoparticles with Rare Earth as Potential Contrast Agents for MRI and Luminescent Probes for Bioimaging

Nanoparticles of porous silicon with incorporated europium and gadolinium ions were prepared by using mechanical grinding of electrochemically grown mesoporous silicon films followed with impregnation with rare earth ions from aqueous solutions. The photoluminescence spectroscopy of europium doped porous silicon nanoparticles allowed us to reveal narrow lines associated with the 5D0→7F4 transitions in Eu3+ ions. Measurements of the proton relaxation in aqueous suspensions of nanoparticles with embedded Gd3+ ions showed an effect of the shortening of both the longitudinal and transverse relaxation times. Potential applications of rare earth doped porous silicon nanoparticles as contrast agents in MRI and fluorescent labels in bioimaging are discussed.

Фотолюминесценция сульфида цинка, легированного ионами Mn-=SUP=-2+-=/SUP=- и Eu-=SUP=-3+-=/SUP=- в среде додекана

Photoluminescence (PL) of zinc sulfide powder synthesized and doped with Mn2+ and Eu3+ ions by the method of emerging reagents in a dodecane medium was investigated. In the absorption and excitation spectra of the PL samples ZnS and ZnS:Mn2+(Eu3+), bands corresponding to the transitions of electrons from the valence band to the conduction band and to the levels of structural defects of ZnS, as well as bands of transition of 4f – electrons of Eu3+ ions from the ground 7F0 to excited electronic states were recorded. A wide band associated with recombination processes at the energy levels of defects on the surface of ZnS particles is observed in the PL spectra. Narrow bands of PL are attributed to 5D0→7Fj and 4T1→6A1 electronic transitions in Eu3+ and Mn2+ ions. They are associated with the intra-zone glow centers formed by these ions in the ZnS structure. Energy transfer from ZnS defect levels to excited energy levels of Eu3+ ions was registered. Assumptions are made about the mutual influence of ZnS and alloying ions, as well as about the influence of synthesis conditions on the spectral properties of substances.

Photoluminescence of zinc sulfide doped with Mn-=SUP=-2+-=/SUP=- and Eu-=SUP=-3+-=/SUP=- ions in dodecane medium

Photoluminescence (PL) of zinc sulfide powder synthesized and doped with Mn2+ and Eu3+ ions by the method of emerging reagents in a dodecane medium was investigated. In the absorption and excitation spectra of the PL samples ZnS and ZnS : Mn2+(Eu3+), bands corresponding to the transitions of electrons from the valence band to the conduction band and to the levels of structural defects of ZnS, as well as bands of transition of 4f-electrons of Eu3+ ions from the ground 7F0 to excited electronic states were recorded. A wide band associated with recombination processes at the energy levels of defects on the surface of ZnS particles is observed in the PL spectra. Narrow bands of PL are attributed to 5D0-&amp;gt;7Fj and 4T1-&amp;gt;6A1 electronic transitions in Eu3+ and Mn2+ ions. They are associated with the intra-zone glow centers formed by these ions in the ZnS structure. Energy transfer from ZnS defect levels to excited energy levels of Eu3+ ions was registered. Assumptions are made about the mutual influence of ZnS and alloying ions, as well as about the influence of synthesis conditions on the spectral properties of substances. Keywords: non-aqueous synthesis, dodecane, zinc sulfide, alloying, manganese (II) ions, europium (III) ions, photoluminescence.