Luminescent and mechanical properties of the epoxy composites doped with europium complex
Introduction
Luminescent rare earth complexes with organic ligands have many potential applications in light emitting diodes, fluorescent sensors, or laser materials due to their intense emission peaks in visible and near-infrared region under a UV excitation [1], [2], [3], [4], [5], [6], [7]. But their applications are limited by the poor machinabilities and thermal stabilities. In attempting to resolve these problems, some research groups have incorporated the complexes into various sol–gel and polymer matrixes [8]. Up to now, a series of rare earth complex-containing polymer composites were synthesized and their luminescence properties were studied [9], [10], [11], [12], [13]. Much of these composites show favorable luminescent and mechanical properties implying a promising future in real-life applications. However, the metal ion incorporated in the matrix may be disturbed by environmental molecules more or less which induces the quenching of luminescence [1], [14]. Many efforts have been devoted to solute this problem among which designing an organic polydentate ligand which can shield the rare earth ion from interfering of surrounding molecules may be the most effective one [15], [16], [17], [18]. We have designed and synthesized a series of tripodal ligands which could form stable cup-like structures when coordinated to the central metal ions [19], [20], [21]. In this report, we utilize a Eu complex of such ligand to develop a high performance luminescent nanocomposite with epoxy for special material applications.
Section snippets
Instruments
The C, H, and N were determined with an Elementar Vario E1 Elemental analyzer. 1H NMR data were recorded with a Varian INOVA 500NB spectrometer. IR spectra were recorded using a Nicolet AVATAR-360 spectrometer. The steady-state fluorescence and fluorescence lifetimes were determined with an Edinburgh Instrument FLS920 fluorescence spectrophotometer using a laser light resource. The samples were sputtered with about 10 nm of Au prior to SEM imaging. Tensile tests were performed in all seven sets
SEM analysis
The SEM images show that direct reaction of H3L·HCl and Eu(ClO4)3 in acetone results in amorphous solid particles which are badly aggregated to form a big mass with a coarse surface (Fig. 1a). Fig. 1b gives out the structures of the complex products prepared by redeposition method with cetyltrimethylammonium bromide as surfactant. In this image, the particles exhibit the presence of uniform nanoballs with diameters rang from 30 nm to 100 nm. Some nanoballs grow together with each other due to
Conclusion
Ball-like nanoparticles of Eu complex were successfully prepared. Property tests show that europium complex maintains its molecule structure and luminescent strength in matrix which may attribute to the stable cup-like structure of the ligand which can protect the Eu ion from outer molecules. The epoxy composites possess good mechanical properties compared to the pure complex which may make it applicable in a wide range of new technologies.
Acknowledgement
This project is fully supported by the Hong Kong Polytechnic University Grant (B-Q856/ PolyU5271/04E).
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