Self-assembled and fluorescence enhancement of semiconductor nanoparticles induced by surfactant adsorption

When semiconductor colloidal CdS nanoparticles and nonylphenol are mixed together in dimethyl sulfoxide at room temperature, a self-assembling process is induced. In the course, the size tunable properties of CdS nanoparticles are amplified. A blue shift in the emission spectrum and a strong photoluminescence enhancement are observed without significant change in the absorption features of the colloidal nanoparticles. These results are attributed to the adsorption of nonylphenol onto the nanoparticles surface and to the association process of the surfactant molecules. The surfactant adsorption process provides a nanoparticle surface passivation and induces an associative phase that enlarges the photoluminescence stability. This strategy opens the possibility to improve simultaneously physicochemical and photoluminescence properties of nanocrystals in solution as well as to control their deposition on two-dimensional surfaces.