Green coordination chemistry as a novel approach to fabricate polymer:Cd (II)-complex composites: Structural and optical properties

In the present work black tea leaves extract solution as a novel green coordination method was used to synthesis cadmium metal ions-complexes (Cd2+-polyphenol complex) with enhanced absorption in UV-vis region. The Cd2+-polyphenol complexes were mixed with poly (vinyl alcohol) (PVA) to fabricate composite films with tunable optical properties. The construction of direct band gap (DBG) polymer composites with developed amorphous phase is vital for applications in optoelectronic devices. The Cd2+-polyphenol complexes and composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-Vis spectroscopy. The outcomes indicate that the interaction between Cd+2 ions and polyphenols can create Cd2+-polyphenol complex. It is displayed by the XRD findings that the synthesized Cd2+-polyphenol complexes are amorphous structure. The analysis of XRD deconvolution shows a development of amorphous nature of PVA with Cd2+-polyphenol complex insertion. The FTIR results exhibit the occurrence of complexation between PVA and Cd2+-polyphenol complex. From UV-Vis spectroscopy study, the optical parameters (absorption edge, refractive index (n), dielectric constant (epsilon r), dielectric loss (epsilon i), and band gap energy (Eg)) of pure PVA and composite films were measured. Examination of the epsilon i optical parameter is carried out in order to measure the Eg, while kinds of electronic transition in the films are determined based on the Tauc's method.