Integrated Luminescence Intensity Research Articles

Luminescence Properties of Yb-2,4-Dimethoxyhematoporphyrin IX, a Promising Compound for Diagnosis of Malignant Tumors

The measured quantum yield of Yb-2,4-dimethoxyhematoporphyrin (Yb-DMHP) in DMSO was 0.8%. It was found that molecular oxygen did not quench luminescence of the metal ion in Yb-DMHP, which was a diagnostic advantage while using this complex in practice. The kinetic characteristics of IR luminescence of the Yb porphyrin complex in DMSO/H2O mixtures were measured. The average lifetime of Yb 3+ ( 2 F5/2) in DMSO was 9.7 ȝ s, which was an order of magnitude greater than that of the auto-fl uorescence of biological tissues. Water molecules quenched effectively IR luminescence of Yb-DMHP. The integrated luminescence intensity of Yb 3+ ( 2 F5/2) depended non-linearly on the fraction of H2O in the DMSO/H2O mixtures. This was indicative of a complex quenching mechanism of Yb luminescence by surrounding molecules.

Crystal Structure and Optical Properties of Lu3Al5O12:Ce3+ Obtained by a Colloidal Chemical Synthesis Method

We have used a colloidal chemical method to synthesize ultradisperse powders of lutetium aluminum garnet activated by Ce3+ ions. We used optical spectroscopy, x-ray and neutron diffraction to study their spectral luminescence and structural properties as a function of the activator concentration and the heat treatment conditions for the precursor. We have observed a change in a number of structural parameters of these powders, due to the particular details of their synthesis, which leads to distortion of the crystallographic environment of the Ce3+ ions and a change in the intensity of their luminescence. We show that among the studied powders, the highest integrated luminescence intensity is observed for an activator concentration of 1.0 at.%, and its maximum is achieved with heat treatment in the range 1200–1300°C.

Optical properties of Ce-doped SiO2 films: From isolated Ce3+ ions to formation of cerium silicate

The optical properties of Ce-doped SiO2 thin films were investigated by photoluminescence spectroscopy. Strong blue luminescence is obtained at room temperature from as-deposited films. The dependence of the luminescence on both Ce content and annealing temperature is then systematically studied. The luminescence is found to shift to higher wavelength as the annealing temperature increases. Moreover, the integrated luminescence intensity first increases for annealing temperatures between 500°C and 900°C as a result of the activation of Ce3+ ions and eventually decreases for higher temperatures which is interpreted by the formation of cerium clusters. At 1100°C, the formation of a cerium silicate phase is observed by infrared absorption spectroscopy. X-ray diffraction measurements confirm the formation of an orthorhombic Ce6Si4(SiO4)2O13 compound.

Pulsed evaporator of an electrodynamic disperse suspension of particles

We consider the technique for obtaining electrodynamic disperse suspension of metal (Al, W, Cu) and dielectric (semiconductor) particles (SiO2, Al2O3, CuO, Cu2O) and its evaporation with the help of a diffusive electric discharge. The time dependences of current and integrated luminescence intensity in a pulsed electric discharge in a tube containing a film of a substance (Cu) of the electrodynamic disperse suspension are measured.

Rare earths in lead-free oxyfluoride germanate glasses

Spectroscopic properties of rare earths in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Eu3+, Pr3+ and Er3+ ions were examined as a function of BaF2 concentration and several spectroscopic parameters for rare earths were determined. The ratio of integrated luminescence intensity of the 5D0→7F2 transition to that of the 5D0→7F1 transition of Eu3+ decrease significantly with increasing BaF2 content. The absorption (Er3+) and emission (Pr3+) ‘hypersensitive transitions’ of rare earths are shifted in direction to shorter wavelengths with increasing BaF2 content in glass composition. Emission spectra and their decays corresponding to the main 4I13/2→4I15/2 laser transition of Er3+ were also analyzed. Quite long-lived NIR luminescence of Er3+ is observed for lead-free glass samples with low BaF2 concentration.

Вплив параметрів друкарської форми на люмінесцентні характеристики нанофотонних друкованих покриттів

There is investigated the influence of the parameters of a printing plate (for screen and pad printing on features of printed application of coatings with nanophotonic components and on parameters of the photoluminescence of obtained printed coverings in order to produce nanophotonic elements for security printing and/or smart packaging. To determine the dependence of luminescence intensity on the thickness of solid coating there was carried out the formation of nanophotonic solid surfaces by means of screen printing with different layer thickness on the polypropylene film. The obtained analytical dependencies were used to confirm the explanation of the processes that occur during the fabrication of nanophotonic coverings by pad printing with photopolymer and metal printing plates. As a result of experimental studies, it was determined that the different character of the dependency of integrated luminescence intensity of nanophotonic elements from the percentage of a pad is explained by the use of different types of pad printing plates, where the size of raster points remains constant in one case, and changes in the other case, while the depth of the printing elements accordingly changes or remains constant. There was shown that consideration of the influence of investigated factors on changes of photoluminescent properties of nanophotonic printed surfaces that should be allows to obtain nanophotonic areas with predetermined photoluminescent properties.

Coordination compounds of europium(III), terbium(III), dysprosium(III), samarium(III), and gadolinium(III) with 2-acetylbenzoic acid

LnAcbenz3 · 3H2O complexes of Eu3+, Tb3+, Dy3+, Sm3+, and Gd3+ with 2-acetylbenzoic acid (HAcbenz) have been synthesized. The complexes have been studied by thermogravimetry and infrared and luminescence spectroscopy. According to IR spectroscopy data, the complexation of Acbenz− with lanthanide ions occurs due to the bidentate coordination of carboxyl groups. According to thermal analysis, the complexes are dehydrated at a temperature above 140°C, and their thermodestruction begins at a temperature above 250°C. From the luminescence spectra measured at 77 and 300 K, it has been established that the integral luminescence intensity of EuAcbenz3 · 3H2O and TbAcbenz3 ° 3H2O is, respectively, 10 and 19 times higher than for tris-benzoates of the same metals. TbAcbenz3 ° 3H2O, the most intensively luminescing complex, is recommended for use as a promising luminescent material.

Spectroscopic studies of Eu3+:PbO–Bi2O3–WO3–B2O3 glasses

The effect of Bi2O3 and PbO on the physical and luminescence properties of Eu3+:PbO–Bi2O3–WO3–B2O3 glasses is presented. The increase in the concentration of Bi2O3 causes UV shift in the optical absorption spectra and increase in the intensities in the photoluminescence spectra (excitation and emission) of these glasses. The spectroscopic ratio factors of the integrated luminescence intensities 5 D 0 → 7 F J / 5 D 0 → 7 F 1 (j = 0, 1, 2, 3) are reported. The experimental branching ratios of the 5 D 0 → 7 F J (j = 0, 1, 2, 3) are presented. The 5 D 0 → 7 F 2 exhibits high β R (>60 %) values for all glasses reflecting their potential lasing application in the development of red laser and optical devices. The σ e for 5 D 0 → 7 F 2 and 5 D 0 → 7 F 4 transitions are reported. The observed 5 D 0 → 7 F 0 in the emission spectra confirms low symmetry around Eu3+ ion for all glass compositions.

The optical band gap and surface free energy of polyethylene modified by electron beam irradiations

In this study, investigations have been carried out on electron beam irradiated ultra high molecular weight polyethylene (UHMWPE). Polyethylene samples were irradiated with 1.5MeV electron beam at doses ranging from 50 to 500kGy. Modifications in optical properties and photoluminescence behavior of the polymer were evaluated by UV–vis and photoluminescence techniques. Changes of surface layer composition of UHMWPE produced by electron irradiations were studied by Rutherford back scattering spectrometry (RBS). The change in wettability and surface free energy induced by irradiations was also investigated. The optical absorption studies reveal that both optical band gap and Urbach’s energy decreases with increasing electron dose. A correlation between energy gap and the number of carbon atoms in clusters is discussed. Photoluminescence spectra were reveal remarkable decrease in the integrated luminescence intensity with increasing irradiation dose. Contact angle measurements showed that wettability and surface free energy increases with increasing the irradiation dose.

Does photodissociation of molecular oxygen from myoglobin and hemoglobin yield singlet oxygen?

Time-resolved luminescence measurements in the near-infrared region indicate that photodissociation of molecular oxygen from myoglobin and hemoglobin does not produce detectable quantities of singlet oxygen. A simple and highly sensitive method of luminescence quantification is developed and used to determine the upper limit for the quantum yield of singlet oxygen production. The proposed method was preliminarily evaluated using model data sets and confirmed with experimental data for aqueous solutions of 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin. A general procedure for error estimation is suggested. The method is shown to provide a determination of the integral luminescence intensity in a wide range of values even for kinetics with extremely low signal-to-noise ratio. The present experimental data do not deny the possibility of singlet oxygen generation during the photodissociation of molecular oxygen from myoglobin and hemoglobin. However, the photodissociation is not efficient to yield singlet oxygen escaped from the proteins into the surrounding medium. The upper limits for the quantum yields of singlet oxygen production in the surrounding medium after the photodissociation for oxyhemoglobin and oxymyoglobin do not exceed 3.4×10−3 and 2.3×10−3, respectively. On the average, no more than one molecule of singlet oxygen from every hundred photodissociated oxygen molecules can succeed in escaping from the protein matrix.

Photoluminescence Properties of Red-Emitting Mn2+-Activated CaAlSiN3 Phosphor for White-LEDs

Mn2+-doped CaAlSiN3 phosphors have been prepared by a solid-state reaction method at high temperature and the solubility of Mn2+ in the host lattice as well as their photoluminescence properties were investigated. In CaAlSiN3, not only Ca2+ sites, but also Al3+ sites can be substituted by Mn2+ ions. CaAlSiN3 : Mn2+ absorbs blue light in the spectral range of 440–460 nm, and exhibits a broad band emission in the wavelength range of 475–750 nm, which can be ascribed to the 4T1 (4G) → 6A1 (6S) transition of Mn2+ located at two different sites in CaAlSiN3. The emission bands at lower energy (15,950 cm−1 or 627 nm) and higher energy (18,250 cm−1 or 548 nm) are assigned to the Mn2+ locating at the Al site (MnAl) and Ca site (MnCa), respectively with energy transfer from MnCa to MnAl. In addition, the integral luminescence intensity only decreases to about 94% at 150°C of the value at 50°C, which is of great interest for the applications of white-LEDs.

Photoluminescence in dense arrays of silicon nanocrystals: the role of the concentration and average size

The computer-assisted Monte Carlo simulation of the photoluminescence kinetics in planar insulator structures with embedded silicon nanocrystals is carried out. In the simulation, the number of nanocrystals in the array was >106. It is shown that, in rather dense arrays, a significant role is played by the processes of energy exchange between neighboring nanocrystals, resulting in the elimination of smaller nanocrystals from the luminescence process and in a noticeable decrease in the integrated luminescence intensity. Nonexponential decay of the luminescence intensity is established. Such character of the decay is attributed to different relaxation processes prevailing at different stages of system’s evolution.

Wavelength dependence of nonlinear optical properties of colloidal CdS quantum dots

Wide wavelength range (550-1600 nm) measurements of nonlinear optical properties of ca. 5 nm CdS quantum dots (QDs) colloidal solution were performed using the Z-scan technique with femtosecond laser pulses at 1 kHz. Parameters characterizing nonlinear absorption and nonlinear refraction were determined. Nonlinear absorption has the character of a two-, three- and four-photon process depending on the wavelength range, with the values of the relevant coefficients peaking at 750 nm, 1200 nm and 1500 nm, respectively. The order of the nonlinear processes was confirmed by measurements of the integral luminescence intensity vs. input excitation intensity. Maxima of the multi-photon absorption bands correspond to the second absorption band of the QDs. The maximum value of the two-photon absorption cross-section σ2 was estimated to be 7.2 × 10(-47) cm(4) s per QD at 750 nm.

Condensation of excitons in Cu2O at ultracold temperatures: experiment and theory

We present experiments on the luminescence of excitons confined in a potential trap at milli-Kelvin bath temperatures under continuous-wave (cw) excitation. They reveal several distinct features like a kink in the dependence of the total integrated luminescence intensity on excitation laser power and a bimodal distribution of the spatially resolved luminescence. Furthermore, we discuss the present state of the theoretical description of Bose–Einstein condensation of excitons with respect to signatures of a condensate in the luminescence. The comparison of the experimental data with theoretical results with respect to the spatially resolved as well as the integrated luminescence intensity shows the necessity of taking into account a Bose–Einstein condensed excitonic phase in order to understand the behaviour of the trapped excitons.

Plasmon-assisted photoluminescence enhancement of SiC nanocrystals by proximal silver nanoparticles

Plasmon-enhanced photoluminescence has wide application potential in many areas, whereas the underlying mechanism is still in debate. We report the photoluminescence enhancement in SiC nanocrystal–Ag nanoparticle coupled system spaced by the poly(styrene sulfonic acid) sodium salt/poly(allylamine hydrochloride) polyelectrolyte bilayers. The integrated luminescence intensity can be improved by up to 17 times. Our analysis indicates that the strong coupling between the SiC nanocrystals and the surface plasmon oscillation of the silver nanoparticles is the major cause of the luminescence enhancement. These findings will help to understand the photoluminescence enhancement mechanism as well as widen the applications of the SiC nanocrystals in photonics and life sciences.

Luminescence enhancement due to energy transfer in ZnO nanoparticles and Eu3 + ions co-doped silica

SiO2 thin films co-doped with ZnO nanoparticles and Eu3+ ions were prepared by sol–gel method. The formation of nano-sized ZnO particles was confirmed by X-ray diffraction patterns and transmission electron microscopy. The characteristic emission bands from Eu3+ ions can be observed at room temperature and the luminescence intensity is increased obviously by introducing ZnO nanoparticles into Eu3+-doped silica films. The integrated luminescence intensity is influenced by the concentration and size of ZnO particles, suggesting effective energy transfer from nano-sized ZnO to Eu3+ ions. It is argued that the efficient luminescence enhancement occurs under the suitable Zn2+ amount and annealing temperature.

Improve the physical and chemical properties of biocompatible polymer material by MeV He ion beam

There is a high interest in improving the hydrophilicity of polymer surfaces due to their wide use for technological purposes. In this study Ultra High Molecular Weight Polyethylene (UHMWPE) as a biocompatible material was bombarded with 1MeV He ions to the fluences ranging from 1×1013 to 5×1014cm−2. The pristine and ion beam modified samples were investigated by photoluminescence (PL), ultraviolet–visible (UV–vis) spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The changes of wettability and surface free energy were determined by the contact angle measurements. The obtained results showed that the ion bombardment induced decrease in integrated luminescence intensity and decrease in the transmittance with increase of ion fluence as well. This is might be attributed to degradation of polymer surface and/or creation of new electronic levels in the forbidden gap. The FTIR spectral studies indicate that the ion beam induces chemical modifications within the bombarded UHMWPE. Formation of carbonyl groups (C=O) on the polymer surface was studied. Direct relationship of the wettability and surface free energy of the bombarded polymer with the ion fluences was observed.

Luminescence enhancement by the reduction–oxidation synthesis in monoclinic RE2O3 (RE=Eu, Gd) phosphors containing Eu3+ activator

A novel synthesis was developed for enhanced luminescence in sesquioxide phosphors containing Eu3+ activator. It consisted of two annealing steps: reduction under vacuum with gaseous H2 at 10Torr and 1300°C and re-oxidation at 300–1500°C in air. The integrated luminescence intensity of the monoclinic Eu2O3 phosphor was enhanced ca. 21 times by this method compared with conventional processing. The photoluminescence (PL) intensity was maximized at re-oxidation temperatures of 500–1100°C. The PL characteristics of monoclinic Eu2O3 and Gd2O3:0.06Eu samples were compared with a commercial cubic Y2O3:Eu phosphor. The evolution of physical characteristics during the two-step annealing was studied by Raman spectroscopy, XPS, XRD, PL decay analysis, and SEM. PL decay lifetime increased proportionally to the PL intensity over the range 0.5–100μs. Additional vibrational modes appeared at 490, 497, and 512cm−1 after the two-step annealing. The increase in PL intensity was ascribed to the formation of excess oxygen vacancies and their redistribution during annealing. Resonance crossovers between the charge transfer state and the emitting 5DJ states are discussed in relation to reported luminescence saturation mechanisms for oxysulfides Ln2O2S:Eu3+ (Ln=Y, La).

X-ray luminescence spectra of graded-gap AlxGa1−xAs structures irradiated by alpha particle

The influence of 241 Am alpha particle irradiation on X-ray luminescence spectra of the graded-gap Al x Ga 1− x As structures of different thicknesses is investigated. It is observed that the integral X-ray luminescence intensity of nonirradiated thin (15 μm) structure is 1.4 times less than that in the thick (32 μm) structure, and this difference increases to 3 times after 3×10 10 cm −2 dose of irradiation by alpha particle. The X-ray luminescence intensity of the energy hν <1.5 eV of thin nonirradiated structure is about 7 times less than that in thick one. The internal graded-gap electric field F gg is responsible of that large difference, because it shifts the X-ray generated carriers to the narrow-gap surface with great nonradiative surface recombination rate. The alpha particle irradiation increases nonradiative recombination rate and causes a decrease of the X-ray luminescence intensity of all spectra lines in the thin (15 μm) detector. The most significant drop in X-ray luminescence efficiency is observed from the region at narrow-gap surface after the initial stage (10 9 cm −2 dose) of alpha particle irradiation. In the 32 μm thick detector, the luminescence intensity of the energy hν =1.8 eV does not change up to 2×10 10 cm −2 of alpha particle irradiation dose. That means the high irradiation hardness of the thick graded-gap X-ray detector with optical response.

Radiative properties of α-ZnAl 2S 4:V spinel type single crystals

The absorption and luminescent properties of α-ZnAI 2S 4:V spinel type crystals in the temperature range 10–300 K are investigated. The spectra are assigned to the electronic transitions of trivalent vanadium ions located in octahedral sites. It is shown that at low temperatures the three main components of the revealed IR luminescence spectra are caused by the 1A 1g( 1G)→ 1E g( 1D), 1T 2g( 1D), 3T 2g( 3F)→ 3T 1g( 3F), and 1E g( 1D)→ 3T 1g( 3F) transitions. The observed dependencies of the emission components intensities on temperature are explained assuming that there is a phonon assisted tunnelling between 3T 2g( 3 F) and 1E g( 1D) states. On temperature rise, the 3T 2g( 3F)→ 3T 1g( 3F) vibronic transitions suppress other emission channels, which leads to the enhancement of the integral luminescence intensity and to the broadening of the spectrum centred at λ=1.4 μm.