Length and composition tunable Sb–Bi–S nanowires for optoelectronic devices prepared via an isostructure-favored solvothermal synthesis

We report the ethylene glycol-mediated solvothermal synthesis of the continuous solid solution (Sb _1-xBi _x) ₂S ₃ (0 < x < 1) with 1D nanostructures (nanowires and nanorods). The ternary products show a broad variation in Bi:Sb composition ratios (53:47–7:93), length-to-diameter aspect ratios (2.7–66.2), and optical bandgap energies (1.36–1.55 eV) as well as an enhanced photocurrent (e.g., (Sb _1-xBi _x) ₂S ₃ with x = 0.22 is three times higher than pure Sb ₂S ₃ ). The gradual shift of peak positions in the XRD patterns and the uniform distributions of Bi, Sb and S elements in EDS mapping prove the formation of single-phase (Sb _1-xBi _x) ₂S ₃ solid solution. Its formation is due to an isostructure-favored alloying mechanism, since Sb ₂S ₃ and Bi ₂S ₃ possess the same orthorhombic structure (space group: Pnma) and the similar lattice constants. The substitution of Bi for Sb isovalent cations can shorten the lengths of ternary alloyed Sb–Bi–S nanowires and transfer them to low aspect-ratio nanorods at high Bi/Sb precursor ratios. The dependence of the lengths on Bi/Sb ratios is reasonably interpreted considering the differences in the number of nuclei at different amounts of Bi ions and the covalency of Bi–S and Sb–S bonds during the alloying process.