Starch-Assisted Synthesis of Bi₂S₃Nanoparticles for Enhanced Dielectric and Antibacterial Applications

Starch [(C₆H₁₀O₅)_n]-stabilized bismuth sulfide (Bi₂S₃) nanoparticles (NPs) were synthesized in a single-pot reaction using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and sodium sulfide (Na₂S) as precursors. Bi₂S₃NPs were stable over time and a wide band gap of 2.86 eV was observed. The capping of starch on the Bi₂S₃NPs prevents them from agglomeration and provides regular uniform shapes. The synthesized Bi₂S₃NPs were quasispherical, and the measured average particle size was ∼11 nm. The NPs are crystalline with an orthorhombic structure as determined by powder X-ray diffraction and transmission electron microscopy. The existence and interaction of starch on the NP's surface were analyzed using circular dichroism. Impedance spectroscopy was used to measure the electronic behavior of Bi₂S₃NPs at various temperatures and frequencies. The dielectric measurements on the NPs show high dielectric polarizations. Furthermore, it was observed that the synthesized Bi₂S₃NPs inhibited bacterial strains (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) and demonstrated substantial antibacterial activity.