Innovative Green Chemistry Approach to Synthesis of Sn2+-Metal Complex and Design of Polymer Composites with Small Optical Band Gaps

In this work, the green method was used to synthesize Sn2+-metal complex by polyphenols (PPHs) of black tea (BT). The formation of Sn2+-PPHs metal complex was confirmed through UV-Vis and FTIR methods. The FTIR method shows that BT contains NH and OH functional groups, conjugated double bonds, and PPHs which are important to create the Sn2+-metal complexes. The synthesized Sn2+-PPHs metal complex was used successfully to decrease the optical energy band gap of PVA polymer. XRD method showed that the amorphous phase increased with increasing the metal complexes. The FTIR and XRD analysis show the complex formation between Sn2+-PPHs metal complex and PVA polymer. The enhancement in the optical properties of PVA was evidenced via UV-visible spectroscopy method. When Sn2+-PPHs metal complex was loaded to PVA, the refractive index and dielectric constant were improved. In addition, the absorption edge was also decreased to lower photon. The optical energy band gap decreases from 6.4 to 1.8 eV for PVAloaded with 30% (v/v) Sn2+-PPHs metal complex. The variations of dielectric constant versus wavelength of photon are examined to measure localized charge density (N/m*) and high frequency dielectric constant. By increasing Sn2+-PPHs metal complex, the N/m* are improved from 3.65 x 10(55) to 13.38 x 10(55) m(-3) Kg(-1). The oscillator dispersion energy (E-d) and average oscillator energy (E-o) are measured. The electronic transition natures in composite films are determined based on the Tauc's method, whereas close examinations of the dielectric loss parameter are also held to measure the energy band gap.

Automated summary

In this study, a green method was used to synthesize Sn2+-metal complex by polyphenols from black tea. The synthesized Sn2+-PPHs metal complex successfully decreased the optical energy band gap of PVA polymer. The optical properties of PVA were enhanced when loaded with the Sn2+-PPHs metal complex.