Growth dynamics of zinc selenide quantum dots: the role of oleic acid concentration and synthesis temperature on driving optical properties

The growth dynamics of zinc selenide quantum dots (ZnSe QDs) using oleic acid as stabilizer was addressed in this work. The QDs were synthesized by hot-injection method, using 2:1 and 10:1 oleic acid/zinc acetate ratio at 170, 190, and 210 °C. The syntheses were carried out for 30 min, 1, 2, and 3 h and the samples were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and UV-Vis spectroscopy. The QDs diameter was evaluated by Effective Mass Approximation theory from the optical band gap. Lower oleic acid/zinc acetate molar ratio resulted in smaller particles and narrower size distribution. These results, evaluated under the light of Classical Nucleation and Growth Theory, were attributed to a smaller solubility of the monomers in the oleic acid solution. This effect leads to an increased supersaturation, promoting faster nucleation and, eventually, diffusion controlled growth, resulting in particles with narrower size distribution.