Luminescence Study of Water-Soluble CdS Nanoparticles Produced by Femtosecond Laser Ablation at High Laser Fluence

Water-soluble CdS nanoparticles (NPs) with excellent colloidal stability were produced by femtosecond laser ablation at high laser fluence. The transmission electron microscope image of the obtained NPs exhibited a presence of two populations, characterized by low and high size dispersions, with different mean particle sizes. A comprehensive optical spectroscopy study of the NPs was carried out, and the results indicated a close correlation between the distribution properties and the luminescence characteristics. By analyzing the photoluminescence spectra of the CdS NPs synthesized under different focusing conditions, we revealed that the formation of the two-peak NPs distributions is related to the breakdown-induced plasma in water at such high laser fluence. However, this plasma-related ablation could manifest itself in the production of highly dispersed population, whereas the formation of the low-dispersed one is mainly attributed to the pure radiation-related ablation. This work will help us take advantage of the ultrapulse laser to synthesize favorable water-soluble semiconductors NPs for biosensing and labeling applications.