Thermal quenching of photoluminescence of Eu3+ ions in an Eu(fod)3 complex

Abstract

Introduction.Currently transparent polymer materials are being increasingly widely used in optoelectronics. They are used as the basis for designing new types of integrated optics devices such as optical amplifiers, frequency selectors, three-dimensional memory devices, etc. Furthermore, study of the physical and chemical properties of polymers is of significant interest since those properties can change considerably when specific molecular compounds are added.Adding organometallic compounds to the internal free volume of samples using supercritical media, in particular supercritical carbon dioxide (supercritical CO 2 ), in order to modify their optical properties is a very advanced doping method [1,2]. A still unresolved question is how the matrix of the studied materials affects the spectral properties of the organometallics added to them.Such a property of Eu(fod) 3 molecules as the temperature dependence of the photoluminescence intensity in the range 20 o C-100 o C allows us to use doped polymers as highly sensitive temperature sensors which can be utilized, for example, in medicine. Moderate (up to 70 o C-80 o C) local heating of biological tissues by laser radiation is currently being used to correct the shape of the nasal septum, to regenerate intervertebral discs, and to treat tumors by hyperthermia. The required therapeutic effect is usually achieved when changes in the physical and chemical properties (especially mechanical, optical, and thermal properties) occur within the heated tissue interior as determined by the experimental conditions. Controlling the experimental conditions significantly reduces the likelihood of complications after laser procedures, and so monitoring such conditions has become important in both a scientific and practical sense. Designing such a sensor based on the effect of the temperature dependence of photoluminescence provides a noninvasive, rapid, highly sensitive, and optimal method for observing the conditions during laser heating of biological tissues.The aim of this work was to search for optical materials which can be used in designing a temperature sensor, and to study the effect of temperature on the photoluminescent properties of Eu(fod) 3 . In this project, we were guided by the following considerations. First of all, we need to choose a molecular compound that is photostable in the temperature range 20 o C-100 o C and has a sufficiently intense photoluminescence band in the visible region. Secondly, such a compound should be efficiently introduced into the matrices used with the help of supercritical CO 2 . At this time we have studied the process of quenching of the photoluminescence of Eu 3+ ions in several polymer materials such as polymethylmethacrylate (PMMA), polydimethylsiloxane (PDMS), and polypropylene (PP) doped with Eu(fod) 3 . For comparison, we also used the original polycrystalline Eu(fod) 3 powder in the experiments. The doping

Spectra of copper and europium β-diketonates in alcoholic solutions and transparent dielectrics

“…As we see from Fig. 2a, in the initial Eu(fod) 3 there are two types of centers: Eu(fod) 3 (center I) and, as we hypothesize, its hydrolyzed form (center II (OH) ), which was formed during synthesis of the polycrystalline powder due to the presence of traces of water [9]:…”

“…This work is a continuation of the investigations we started on the spectroscopy of organometallic molecules, introduced by impregnation of some polymers and nanoporous glasses using conventional solutions and solutions of supercritical CO 2 [1][2][3][4]9]. Study of these questions is timely and aimed toward development of new photosensitive and thermosensitive materials, for example for designing a medical luminescent thermosensor to be used in laser operations on biological tissues [9].…”

“…Study of these questions is timely and aimed toward development of new photosensitive and thermosensitive materials, for example for designing a medical luminescent thermosensor to be used in laser operations on biological tissues [9].…”

“…The optical absorption and photoluminescence spectra were obtained on an automatic spectral system described in [4,9]. The EPR spectra of the Cu 2+ ions in the samples were measured on an RE ′ -1306 spectrometer in the 3 cm wavelength range (X band) at a temperature of 77 K. The spectra of the alcoholic solutions of the Cu(hfac) 2 molecules were measured after they were frozen down to liquid nitrogen temperature.…”

Effect of the external medium on the spectral characteristics of polypropylene films doped with Eu(fod)3 molecules

“…Using europium organometallic compounds makes it possible to excite red photoluminescence of the Eu 3+ rather easily through the ligand component of the molecule [7,10], where the intensity of such photoluminescence varies considerably within the temperature range 20 o C-100 o C [4]. This factor is important in choosing a thermosensitive material for a temperature sensor using the effect of the fall-off in the intensity of the photoluminescence excited from a simple light-emitting diode source in the near UV range [4]. However, the application of such materials for a wide variety of practical problems, including the case mentioned above, may run up against some difficulties if we do not take into account the effect of the external medium, leading to a change in the spectral characteristics of polymers doped with organometallic compounds.…”