Tuning of the Dispersion of Ligand-Free ZnO Quantum Dots in Polymer Matrices with Exfoliated Nanoplatelets
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This paper concerns the experimental observation of dispersion tuning ligand-free ZnO quantum dots down to the single-particle level, in polymer matrices, through the use of exfoliated ZrP nanoplatelets. High- resolution transmission electron microscopy and optical transmission spectroscopy reveal that the degree of dispersion depends strongly on the relative volume fractions of each nanoscale constituent, and polymer nanocomposites prepared with this method exhibit nearly identical optical transmittance spectra to that of their neat counterparts. Dynamic and kinetic analyses and control experiments involving the dispersion of ZnO in organic solvents using nanoplatelets suggest that the dispersion mechanism likely involves nanoplatelets locally and transiently altering the thermodynamic character of the matrix, perhaps through polarization. Hence, quantum dots achieve their dispersed state through more favorable interactions with the surrounding medium brought about by the presence of nearby diffusing nanoplatelets. This work demonstrates the ability to stabilize nanoscale particles without the use of covalent functionalization or physisorbed macromolecules and at a low dispersant volume fraction. Furthermore, the broad applicability of these results could extend into many areas of nanocomposites research. 2009 American Chemical Society.