Solvent-Directed Femtosecond Laser Ablation: Tuning Phase and Defect Engineering in Hybrid CdPS3/CdS Nanostructures

TL;DR

Wide-bandgap CdPS3 limits visible-light solar applications. The authors use a surfactant-free fs-PLAL approach with solvent control to steer phase and defect formation, producing water-synthesized CdPS3 and IPA-induced CdS/Cd0-rich CdPS3/CdS hybrids. The resulting visible-light-active hybrids exhibit enhanced charge separation via Schottky-like interfaces, achieving about 90% degradation of Methylene Blue within 30 minutes under 532 nm light. This solvent-directed defect engineering with fs-PLAL offers a scalable route to design metal-thiophosphate-based photocatalysts for solar-energy conversion and environmental remediation.

Abstract

The limited visible-light absorption of wide-bandgap van der Waals crystals fundamentally restricts their utility in solar energy conversion. Here, we report 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.

Figures (4)

• Figure 1: (a) Crystal structure of bulk CdPS3; b) Scheme of experimental setup for femtosecond pulsed laser ablation in liquid.
• Figure 2: Structural and elemental characterization of CdPS3/CdS nanoparticles synthesized in different solvents. Typical (a-c) TEM images, (d-f) corresponding SAED patterns, and (g-i) EDX spectra of CdPS3 NPs synthesized in (a, d, g) deionized (DI) water, (b, e, h) acetonitrile (ACN), and (c, f, i) isopropanol (IPA). (j) Comparison of the Raman spectra of a bulk CdPS3 crystal with NPs synthesized in IPA, ACN, and DI water. k) Spatially resolved elemental analysis of NPs in ACN, demonstrating distinct CdPS3 and CdS NPs.
• Figure 3: Photoluminescence (PL) spectra of CdPS3/CdS colloids in different solvents. a) PL of ACN, DI water and IPA colloids at 390 nm excitation; b) and c) PL signal of colloidal solutions at excitation of 390 nm in DI water and ACN, correspondingly, deconvoluted into two distinct Gaussian peaks; d) PL of ACN, DI water and IPA colloids at 440 nm excitation; e) and f) PL signal of colloidal solutions at excitation of 440 nm in DI water and ACN, correspondingly, showing a distinct Gaussian peak.
• Figure 4: (a) Schematic of the experimental setup. (b) Time-resolved Raman spectra of the photocatalytic system containing a 1:1 mixture of MB in isopropanol and a colloidal suspension of CdPS3 nanoparticles. (c, d) Intensity of the MB Raman peak at 1625 $cm^{-1}$ as a function of time for samples in different solutions: (c) DI water and (d) IPA.