L-cystine-assisted synthesis of bismuth sulfide with well-aligned nanoflakes

Bismuth sulfide (Bi₂S₃) with were synthesized by the L-cystine-assisted approach in the presence of L-cystine, which served as both the sulfur source and the directing molecule in the formation of Bi₂S₃ nanostructures. The X-ray powder diffraction pattern shows that the products are orthorhombic Bi₂S₃ phase with cell constants as a=1.1141 nm, b=1.1304 nm, c=0.3978 nm. The quantification of X-ray photoelectron spectra analysis peaks gives a mole ratio of 2.0:2.9 for Bi to S. Field-emission scanning electron microscopy photographs reveal that the structure of the as-prepared Bi₂S₃ consists of flowerlike patterns with well-aligned nanoflakes, and the thickness of nanoflakes is approximately 20 nm. The reaction duration plays a key role in the crystallization and morphology-controlled synthesis of Bi₂S₃ crystallites. The formation mechanism for the Bi₂S₃ flowerlike with well-aligned nanoflakes is also discussed.