Enhanced Photophysical Properties of Bi₂S₃/AgBiS₂ Nanoheterostructures Synthesized via Ag(I) Cation Exchange-Mediated Transformation of Binary Bi₂S₃
2020
Paul, Sumana | Dalal, Biswajit | Jana, Rajkumar | Shit, Arnab | Datta, Ayan | De, Subodh Kumar
Nanoheterostructures with multiple components and interfaces have gained much attention due to their promising photophysical properties. Here, we have synthesized rod-shaped Bi₂S₃/AgBiS₂ heterostructures via a cation exchange reaction, starting from the binary parent compound Bi₂S₃. The effective ionic radius of monovalent Ag⁺ ion is proved to be the key factor for the intercalation of Ag⁺ ions into the consecutive layers of the orthorhombic Bi₂S₃ (212) plane and finally for the total conversion of Bi₂S₃ to AgBiS₂. Incorporation of Ag⁺ ions into the Bi₂S₃ matrix keeps the morphology of the system intact during this total conversion process. The feasibility of this transformation has been well understood through heat of reaction energy required to exchange one Bi and S atom with an Ag atom using density functional theory based on first-principle calculations. A type-I band alignment is observed at the interface of the Bi₂S₃/AgBiS₂ heterostructure, which has been confirmed from cyclic voltammetry studies. Due to the low band offset between conduction bands of Bi₂S₃ and AgBiS₂, electrons can easily move from one component to another through the interface, which improves the photoactivity of the nanoheterostructure. The high light absorption coefficient of both Bi₂S₃ and AgBiS₂ is proved to be the most effective for the enhancement of the photoinduced properties.
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