Synthesis and optical characterization of the organic luminophore nanocomposite PEPC/Eu(o-MBA)3Phen
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BORDIAN, Olga, VERLAN, Victor, CULEAC, Ion, YOVU, M., ZUBAREVA, Vera. Synthesis and optical characterization of the organic luminophore nanocomposite PEPC/Eu(o-MBA)3Phen. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 222.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

Synthesis and optical characterization of the organic luminophore nanocomposite PEPC/Eu(o-MBA)3Phen


Pag. 222-222

Bordian Olga1, Verlan Victor1, Culeac Ion1, Yovu M.1, Zubareva Vera2
 
1 Institute of Applied Physics, Academy of Sciences of Moldova,
2 Institute of Chemistry of the Academy of Sciences of Moldova
 
Disponibil în IBN: 11 martie 2019


Rezumat

In last decades, research of rare-earth organic materials has been a very attractive subject to their peculiar properties and wide potential applications as luminescent labels in biological systems and active centers for luminescent materials and devices. In the work was studied nanocomposite PEPC/Eu(o-MBA)3Phen, where PEPC – poly-N-epoxypropilcarbazol and o-MBA o– methylbenzoic acid, Phen – phenanthroline. EuCl3·6H2O, o-MBA, and Phen were purchased. All reagents had analytical grade and were used without further purification. Synthesis of rare-earth complex Eu(o- MBA)3Phen: a warmed ethanol solution (96%) containing 0.4 g (3 mmol) of o-methylbenzoic acid and 0.2 g (1 mmol) of 1,10 – phenanthroline was adjusted to pH 6.0 – 7.0 with 1M NaOH solution. Further, europium chloride (1 mmol) dissolved in 5 ml of water was added dropwise to the organic mixture and stirred. Light pink precipitate was formed immediately. The precipitate was filtered, washed with small portions of ethanol, dried thoroughly in air. The synthesis yield was 0.56 g (37.6%). For C36H29O6N2, it was calculated, %: Eu - 20.61, C - 58.63, H - 3.97, N - 3.80 . Found, %: Eu - 20.88, C - 59.23, H - 4.17, N - 3,75. The thin films of nanocomposite PEPC/Eu(o-MBA)3Phen were obtained on quartz substrates from colloidal solution mixed by spin-coating method and subsequently dried. The solutions of PEPC and Eu(o-MBA)3Phen were obtained separately by dispersion in solvents by mixing toluene and DMFA in an ultrasonic bath for 30 min. at a temperature of 60 ° C. Nanocomposite coatings were studied separately by microscopy, optical transmission and photoluminescence spectra. The absorption threshold at different concentrations of Eu(o- MBA)3Phen in PEPC was approximately the same (3.34 – 3.4 eV). Photoluminescence spectra were measured using monochromator based on MDR-23-24 connected to the PC, photoluminescence excitation was performed with nitrogen laser (λ = 337 nm) radiation intensity range 0.1–103 W/cm2. PL spectra characterized the efficiency of energy transfer from the LUMO energy levels of chelates and ligands of the compound to the energetic levels of Eu3+ ion. HOMO and LUMO levels of the complex PEPC/Eu(o-MBA)3Phen are found to be situated between levels S and T of ligands, and this case is similar to doping of semiconductor. The photoluminescence properties can be attributed to the internal transition of Eu3+ ion 5D0 →7Fi (i = 0,1,2,3 and 4), which are centered at 537, 578, 614 (611, 613, 618), 650 and 702 nm. The half width of PL band at 614 nm is less than 10 nm, which indicates that the compound Eu(o-MBA)3Phen exhibits high emission and color purity. Each maximum of PL band is splinted in 3 components. A possible method of raising the fluorescence efficiency of Eu(o-MBA)3Phen is the energy transfer from S and T ligands levels to internal levels of Eu3+ ion. There is a rather weak and broad band at 578.5 and 614 nm associated to the 5D0 →7F 0,2 forbidden electric dipole transitions. Based on selection rules, the band at 594 nm is attributed to the 5D0 →7F1 parity-allowed magnetic dipole transition, which is independent of the surroundings symmetry. The 5D0 →7F1,2 transitions are allowed electrical-dipole transitions. The most intensive band around 614 nm belongs to the 5D0 →7F2 transition that is hyper-sensitive to the symmetry of the crystal field surrounding the Eu3+ ion, and will be relatively strong if the surroundings symmetry is low. In this respect, it is known that the ratio of the emission intensities R = I(5D0 →7F2)/I(5D0 →7F1) is an asymmetry parameter for the Eu3+ sites and a measure of the extent of Eu3+ interaction with surrounding ligands, indicating on the environment of the Eu3 ion.