Facile Synthesis of Urchin-like Hierarchical Microstructures of Bismuth Sulfide by a Couette-Taylor Reactor at Room Temperature.

We reported a room-temperature synthesis of urchin-like hierarchical Bi2S3 microstructures using a Couette-Taylor (CT) reactor, which leverages vortex flow dynamics for improved morphological control. This method enables the rapid formation of Bi2S3 nanostructures via coprecipitation of Bi3+ and S2- precursors, followed by a short stabilization step, whereas traditional synthesis routes typically require high temperatures, high pressures, and long reaction times. Comparative experiments using a static glass vial showed that hierarchical structures can form under quiescent conditions, but introducing Taylor vortex flow in the CT reactor promotes the formation of more uniform and densely packed spherical microarchitectures with an average diameter of 2 ± 0.19 μm. These structures are composed of radially aligned nanofibers with lengths of 406.33 ± 42.16 nm and diameters of 10-30 nm. Systematic variation of the rotation speed revealed a strong correlation between the flow regime and final morphology, with optimal particle uniformity and anisotropy achieved at 150 rpm. Structural and compositional characterization confirmed the formation of crystalline, stoichiometric, and highly pure Bi2S3. Overall, this work demonstrates vortex-assisted flow synthesis in a CT reactor as a versatile and scalable approach for producing morphology-tailored nanomaterials under mild conditions, with potential applicability to both batch and continuous production systems.