Solvent-directed femtosecond laser ablation: tuning phase and defect engineering in hybrid CdPS₃/CdS nanostructures

The limited visible-light absorption of wide-bandgap van der Waals crystals fundamentally restricts their utility in solar energy conversion. Here, we report the application of a surfactant-free, solvent-directed laser synthesis strategy to engineer the phase and optoelectronic properties of cadmium phosphorus trisulfide (CdPS₃). By exploiting the non-equilibrium thermodynamics of femtosecond pulsed laser ablation in liquid (fs-PLAL), we demonstrate a tunable transition from the stoichiometric ternary phase to a highly active binary-rich heterostructure. While ablation in water preserves the monoclinic CdPS₃ lattice, the reducing environment of isopropanol triggers the formation of CdS quantum dots and metallic cadmium defect sites. This solvent-induced phase engineering transforms the ultraviolet-active host into a robust visible-light photocatalyst. The resulting hybrid CdPS₃/CdS nanocolloids exhibit superior charge separation efficiency, driven by Schottky-like metal-semiconductor junctions, achieving ∼90% degradation of methylene blue under 532 nm irradiation within 30 minutes. This work establishes fs-PLAL as a scalable defect-engineering tool for complex ternary layered materials, offering a new design of high-performance metal-thiophosphate-based photocatalysts.