Size-Specific ZnO Quantum Dots as Onsager Cavity in Ooshika–Mataga–Lippert Equation

The influence of the surrounding solvent medium to a solute molecule in solution can be treated within the framework of Onsager reaction field model which is based on the assumption that the solute is reduced to a point dipole at the center of a spherical cavity inside the solvent that can be described as the homogeneous, polarizable medium of specific dielectric constant. When the solute molecules are excited in solution of the polar solvent, the changes in the photophysical properties of the solute are manifested through shifts in the maxima of absorption and fluorescence spectra and the observation can be interpreted in terms of the Ooshika–Mataga–Lippert equation. Over several decades, a wide variety of organic molecules as fluoroprobes have been explored to reveal the polarity of their immediate solvent environment. However, while these molecular probes, with diameters less than 10 A, have been employed so far in the literature as Onsager cavities, the limiting value of their radii has not been restr...