Study on green synthesis and properties of luminescent material bis(8-hydroxyquinoline) calcium (CaQ2)

This work proposes a novel, effective and green synthesis method for bis(8-hydroxyquinoline) calcium (CaQ2) that can be directly used for organic electroluminescent materials. Cycle experiment shows that the utilization of raw materials was well improved. The influence of different synthesis conditions on the crystallinity and purity of the samples was studied through X-ray diffraction spectroscopy (XRD), which indicates that the product has excellent crystallinity and high purity. EDS pattern reveals that the sample contains elements of Ca, C, N and O. The structure was investigated by Fourier transform infrared absorption spectroscopy (FITR). Infrared absorption spectrum illustrates the Ca-O peak at 487 cm−1 and the existence of the quinoline ring. The crystal morphologys obtained by different synthetic conditions were detected by SEM. Since only CaQ2-A had synthesized without adding any organic solvent which had blocks with smooth surface. Luminescence properties of CaQ2 compound were examined by fluorescence spectra at ambient temperature. The emission spectras of CaQ2 under different synthesis conditions were obtained under the excitation of 288 nm excitation wavelength. Maximum emission wavelengths are 470 nm, 466 nm and 466 nm, respectively. The decay lifetime of CaQ2 is 21.83 ns which was obtained at 288 nm excitation. The TG-DTA analysis shows that CaQ2 has a high thermal stability.