Our findings revealed that the composition of the constituents, reaction conditions, and synthetic processes all influence the characteristics and therefore the applications of the resulting biopolymer composites.

By using the chemical bath deposition approach, binary bismuth sulphides (Bi₂S₃) and chromium-doped ternary bismuth sulphides (Bi_2−xCr_xS₃) thin films were effectively produced, and their potential for photovoltaic applications was examined. Structural elucidation revealed that Bi₂S₃ deposited by this simple and cost-effective method retained its orthorhombic crystal lattice by doping up to 3 at.%. The morphological analysis confirmed the crack-free deposition, hence making them suitable for solar cell applications. Optical analysis showed that deposited thin films have a bandgap in the range of 1.30 to 1.17 eV, values of refractive index (n) from 2.9 to 1.3, and an extinction coefficient (k) from 1.03 to 0.3. From the Hall measurements, it followed that the dominant carriers in all doped and undoped samples are electrons, and the carrier density in doped samples is almost two orders of magnitude larger than in Bi₂S₃. Hence, this suggests that doping is an effective tool to improve the optoelectronic behavior of Bi₂S₃ thin films by engineering the compositional, structural, and morphological properties.

Thin films of binary nickel sulphide (NiS) and zinc-doped ternary nickel sulphides (Ni_1−xZn_xS, where x = 0–1) were effectively produced by the chemical bath deposition method, and their potential use in photovoltaics were investigated. Dopant inclusion did not change the crystal structure of NiS, according to the structural analysis of the synthesized samples. They are appropriate for solar cell applications since the morphological study verified the crack-free deposition. Optical research revealed that the deposited thin films had refractive index (n) ranges between 1.25 and 3.0, extinction coefficient (k) ranges between 0.01 and 0.13, and bandgap values between 2.25 and 2.54 eV. Overall findings indicated that doping is a useful method for modifying the composition, and therefore, the structural and morphological characteristics of NiS thin films, to enhance their optoelectronic behavior.

For photovoltaic applications, undoped and Ni²⁺ doped Bi₂S₃ thin films were chemically deposited onto glass substrates at room temperature. Elemental diffraction analysis confirmed the successful Ni²⁺ incorporation in the range of 1.0 to 2.0 at. %, while X-ray Diffraction analysis revealed that orthorhombic crystal lattice of Bi₂S₃ was conserved while transferring from binary to ternary phase. Scanning electron microscopy images reported homogeneous and crack-free morphology of the obtained films. Optoelectronic analysis revealed that the bandgap value was shifted from 1.7 to 1.1 eV. Ni²⁺ incorporation also improved the carrier concentration, leading to higher electrical conductivity. Resultant optoelectronic behavior of ternary Bi_2−x Ni_xS₃ thin films suggests that doping is proved to be an effectual tool to optimize the photovoltaic response of Bi₂S₃ for solar cell applications.

Electrochemical advanced oxidation practices (EAOPs), remarkably, electro-peroxone (EP), photoelectro-peroxone (PEP), and complementary hybrid EP approaches, are emerging technologies on accountability of complete disintegration and elimination of wide spectrum of model pollutants predominantly biodegradable, recalcitrant, and persistent organic pollutants by engendering powerful oxidants in wastewater. A concise mechanism of EP and PEP approaches along with their contribution to free radical formation are scrutinized. Furthermore, this chapter provides a brief review of EP, PEP, and complementary hybrid EP-based EAOPs that have pragmatically treated laboratory-scale low- and high-concentrated distillery biodigester effluent, refractory pharmaceutical, textile, herbicides, micropollutant, organic pollutant, acidic solution, landfill leachates, municipal secondary effluents, hospital, and industries-based wastewater. Afterward, discussion has further extended to quantitatively evaluate energy expenditures in terms of either specific or electrical energy consumptions for EP and PEP practices through their corresponding equations.