Optical and photoluminescence characteristics of amorphous nanocomposites containing organic compounds with Eu+3 and polymers

Abstract

Thin films (1-10 µm thickness) of nanocomposites (NC) based on polymers and organic coordinated compounds (OCC) Eu(TTA)3H2O, Eu(TTA)3Phen, Eu(DBM)3Phen, Eu(TTA)2(Ph3PO)2NO3 (where TTA is thenoyltrifluoroacetonate (C8H5F3O2S), Ph3PO – triphenylphosphine oxyde (C6H5PO) and polymer – polyvinylpyrrolidone ((C6H9NO)n) (PVP) and copolymer styrene-butylmethacrilate (SBMA)) were obtained by chemical methods. NC were characterized by measurements of optical transmission, and photoluminescence (PL) at different concentrations of OCC in NC. It was established that the excitation spectrum of the photoluminescence covers the range of wavelength from 200 to 410 nm. All types of NC show similar characteristics of the photo luminescence and absorption. PL bands centred at 580, 590, 612 - 615, 651, and 700 nm, have been detected that that correspond to the radiative transitions between the energy levels of the Europium ions and it can be attributed especially to internal 4f-4f transitions 5 D0 → 7 Fi (i = 0,1,2,3 and 4), respectively. This has been explained from the viewpoint of the surrounding environment of Eu3+ ion and removal of internal interdiction for transitions in electronic shields of Eu3+ ion as a result of ligands interactions. The dominant maximum of PL is in the range to 612-615 nm with halfwidth less than 10 nm and its intensity is about 20 times higher than intensity of maxima of other bands. The optimal concentrations of OCC in NC for maximum of PL efficiency were in the range 6 - 12%. It was found that there is an effective transfer of energy from polymer matrix to ligands of the OCC complex on their energetic levels HOMO and LUMO, and subsequent energy transfer to the Eu3+ ion. HOMO and LUMO of the OCC complex are found to be situated between levels S and T of the polymer, and they are higher than the energy of 5 D0 → 7 Fi transitions in Eu3+ ion.