Microwave-Assisted Modified Polyimide Synthesis: A Facile Route to the Enhancement of Visible-Light-Induced Photocatalytic Performance for Dye Degradation

Visible-light-active π-conjugated polymer photocatalysts can effectively harness solar energy, thereby offering pragmatic solutions to eclectic environmental issues. In the present study, a series of ingenious visible-light-responsive, stable, and recyclable modified polyimide (SWO₃/PI) photocatalysts was synthesized via a facile microwave-assisted rapid thermal polymerization strategy. The precursors employed were pyromellitic dianhydride, melamine, thiourea, and tungsten trioxide co-catalyst. The template-free inclusion of sulfur and tungsten oxide species into the PI conformation increased visible-light absorption and enhanced the separation efficiency of the photogenerated electron–hole pairs. The visible-light-induced reactive red 120 (RR 120) photodegradation efficiency exhibited by the SWO₃/PI photocatalyst was over 98% and was approximately 2.3 times higher than that exhibited by pristine PI. Herein h⁺ and OH^• were the principal active species involved in dye degradation. Interestingly, the sizable valence band edge downshift from 2.02 to 3.36 eV induced a remarkable enhancement in the photooxidation ability of the photoinduced holes, despite the fact that the relatively inappropriate position conduction band edge position (1.77 eV) did not favor the participation of photoinduced electrons in the reduction process. The liquid chromatography–mass spectrometry results revealed that photocatalytic degradation of RR 120 had been effectively accomplished

Kinetics and mechanism of interaction of Pt(II) complex with bio-active ligands and <i>in vitro</i> Pt(II)-sulfur adduct formation in aqueous medium: bio-activity and computational study

<p>Kinetics of interaction between [Pt(pic)(H₂O)₂](ClO₄)₂, <b>2</b> (where pic = 2-aminomethylpyridine) with the selected ligands DL-methionine (DL-meth) and DL-penicillamine (DL-pen) have been studied spectrophotometrically in aqueous medium separately as a function of [<b>2</b>] as well as [ligand], pH and temperature at constant ionic strength. The association equilibrium constants (<i>K</i>_E) for the outer sphere complex formation have been evaluated together with the rate constants for the two subsequent steps. Activation parameters (enthalpy of activation ΔH^≠ and entropy of activation ΔS^≠) were calculated from the Eyring equation. An associative mechanism of substitution is proposed for both reactions on the basis of the kinetic observations, evaluated activation parameters, and spectroscopic data. Structural optimizations, HOMO-LUMO energy calculation, and Natural Bond Orbital (NBO) analysis of <b>2</b>–<b>4</b> were carried out with Density Functional Theory. Bonding mode of thiol and thio-ether is confirmed by spectroscopic analyses and NBO calculation. Cytotoxic properties of <b>2</b>–<b>4</b> were explored on A549 carcinoma cell lines; DNA-binding properties of the complexes were also investigated by gel electrophoresis.</p