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

Abstract

We have studied the effect of external factors (humidity, pressure, temperature) on the stability of the organometallic compound Eu(fod) 3 (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadione) impregnated into polypropylene (PP) using supercritical CO 2 . We have established that under the influence of external conditions, there is a decrease in the integrated intensity of the absorption band for the Eu(fod) 3 molecule and the photoluminescence (PL) of Eu 3+ ions as a function of the properties of the medium, and in the presence of water molecules the shape of the bands for these spectra changes. We propose a physical model explaining the behavior of the absorption and photoluminescence spectra when the polypropylene films are stored under different conditions. Introduction. Transparent polymer materials doped with organometallic compounds can be widely used in information science (in designing new memory media based on them), in optoelectronics (to obtain new laser media, radiation converters, filters etc.) [1][2][3], and also in biomedical technologies (for example, in developing sensitive temperature sensors [4]). In the latter case, promising materials include some transparent polymers of the polypropylene (PP) and polyethylene (PE) type, doped with Eu(fod) 3 molecules using impregnation in a supercritical CO 2 solution [5,6]. 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. In particular, the rather high porosity of the polymers (the void size in the matrix is as large as 1 nm) not only makes it possible to efficiently dope them using an advanced method via a supercritical CO 2 solution, but also facilitates penetration of atmospheric impurities into the structure of the polymer. Furthermore, the advantage obtained by exciting photoluminescence of Eu 3+ ions via the absorption bands of the ligand of the organometallic compound requires additional studies of photodecomposition mechanisms for organometallic compounds [11] and prediction of the possibilities for improving the photostability of these materials.In this work, we have studied the effect of the medium or atmosphere (humidity, pressure, and temperature of the air) on the characteristics of the absorption and photoluminescence spectra of Eu(fod) 3 molecule...

Люминесцентные свойства разнолигандных beta-дикетонатов неодима, полученных в среде сверхкритического диоксида углерода в полимерных матрицах различной природы

“…Так, в табл. 1 приведены данные по положениям полос в спектре люминесценции экстракта, полученного выдерживанием в хлороформе плёнки ОУМ-5, импрегнированной Nd(Acac) 3 накладывающихся друг на друга узких полос, положения максимумов которых совпадает с максимумами полос люминесценции совместного раствора Nd(Acac) 3 и фенантролина в хлороформе (табл. 1).…”

“…Наличие интенсивной люминесценции у комплексов редкоземельных элементов (РЗЭ), в частности у β-дикетонатов, позволяет использовать их при получении люминесцентных полимерных материалов различного назначения: оптоволоконных волноводов, OLED, оптических сенсоров, конвертеров солнечной энергии [1][2][3][4][5]. Органические комплексы РЗЭ обладают большим сродством к полимерам, чем неорганические люминофоры, а также эффективно преобразуют поглощаемую энергию света в узкополосное люминесцентное излучение через механизм сенсибилизации лиганда [6].…”