Influence of the Acid–Base Component of Surface Energy on Optical Properties of Immobilized Dyes

Spectral properties of dyes change upon attachment to surfaces which need to be understood. While the effects of surface properties affecting the changes such as Brønsted acidity is well-covered, that of surface energy components is not well studied. In this work, two dyes with different number of carboxylic groups were attached on three surfaces (PET, PDMS, and silicon). It was observed the “surface energy components” rather than “total surface free energy” were more pertinent in explaining changes in the spectral properties of the immobilized dyes. An increase in the basic component of surface energy favored monomer formation, while a decrease favored agglomeration. Thus, tuning the spectra of a dye by using surfaces with different surface energy components enables use of the dye for different applications. As an application, dye attached on PET substrate showed promise as optical pH sensor in the range of pH 7–10