Synthesis of CdS nanocrystals by electron beam irradiation of a Cd2+–mercaptopropionic acid aqueous solution

We investigated a simple route for synthesizing CdS nanocrystals (NCs) via irradiation of a CdCl2 + mercaptopropionic acid (MPA) aqueous solution with a 10-MeV electron beam without using any additional sulfur precursors or stabilizers. When the concentration of the MPA was fixed to 2.5 mM, the morphology and optical properties of the NCs were changed by varying the CdCl2 concentration. Based on transmission electron microscopy (TEM) imaging, a 0.4 mM concentration of CdCl2 (the-MPA rich case) created only spherical quantum dots (QDs) with an average diameter of 6.6 nm. When the concentration of CdCl2 was increased to 5 mM (the cadmium-rich case), nanorods with an average diameter of 5.3 nm and an average aspect ratio of 8.2 were formed along with QDs with diameter of 4.9 nm. The crystalline structures of the NCs were verified to be hexagonal.

► CdS NCs are formed by e-beam irradiation of CdCl2 + MPA aqueous solution.
► CdS molecules are released from Cd2+ − MPA complex by energetic electrons.
► Only QDs are formed under a MPA-rich condition.
► NRs and QDs are formed under a cadmium-rich condition.