Water-soluble CdS nanoparticles have been prepared by femtosecond laser(100 fs

800 nm

FL)ablation of a bulk CdS target in water.Being performed in a controllable contamination-free environment

this method makes possible the production of nanomaterials without impurities.The morphology and the optical characteristics were studied through transmission electronic microscopic

UV-Vis optical absorption

and room temperature photoluminescence.The results indicated that the obtained water soluble CdS quantum dots fabricated by femtosecond laser ablation have small size and narrow size distribution.As well

these quantum dots were found to be exceptionally stable in air for at least 6 months.In addition

under the excitation of 300 nm

the photoluminescence of the CdS quantum dots ablated in water shows a band-edge emission peaked at 420 nm with FWHM of 62 nm.The above-mentioned characteristics make these CdS nanoparticles of great attraction for potential application in biological labeling.This work demonstrates that the FL ablation is a simple but effective method for preparation of high quality quantum dots.