Controlled synthesis of ZnS quantum dots with cubic crystallinity by laser ablation in solution

In this work, we propose using the pulsed laser ablation technique in solution as a 'chemical-free' method for forming biatomic or multiatomic semiconductor quantum dots. In particular, we present the results of the formation and characterization of ZnS nanoparticles by laser ablation in solution as a case study for all semiconductors of the III and IV groups. We obtain results comparable to those obtained by chemical methods without the use of surfactants and without changing the crystallinity of the precursor target. Colloidal solutions of nanoparticles with different dimensions were obtained by varying the irradiation time during laser ablation. A study of the morphology and changes in the band edge indicates the formation of ZnS quantum dots with dimensions <4 nm for an irradiation time of less than 10 s. The changes in the band edge were studied in terms of the effective mass approximation model, which indicates, for low irradiation times, the formation of quantum dots with radii ranging from 2.5–2.8 nm and band edges ranging from 4.21–4.15 eV. Raman measurements indicate that quantum dots have the same crystallinity as bulk grains, while photoluminescence measurements clearly show a rearrangement of Zn and S atoms, eliminating the vacancies defects of the bulk material.