Kinetics of ZnO nanoparticle formation via fluorescence measurements

The kinetics of ZnO nanoparticles was examined by fluorescence measurements. Emission peak intensities of the ZnO nanoparticles synthesized at different conditions were monitored during wet-chemical reactions. It was shown that the three stages of the reaction; nucleation, growth, and reaching the average size, can be followed by means of the fluorescence intensities corresponding to both band-edge (∼375 nm, ∼445 nm, and ∼485 nm) and deep-trap (∼520 nm and ∼545 nm) transitions. With both higher stirring velocity and temperature the particle formation is faster. Although the nucleation time is not affected by stirring velocity, higher temperature causes faster reaction rate in all stages including nucleation. This method can be used for controlling the size of the nanoparticles. -- Highlights: • We studied the mechanism of particle growth for ZnO nanoparticles by fluorescence measurements. • We observed that the exitonic levels showed different behaviors; some of which are size dependent. But, all the deep-trap transitions are size dependent. • We observed that both higher stirring velocity and temperature accelerate the particle formation. • We developed a quasi in-situ monitoring method which gives qualitative information about the reaction steps; it can be developed for controlling the size of the nanoparticles