*3.3. Spectroscopic Ellipsometric Studies*

The spectroscopic measurements were carried out with two sets of samples: the first set was thermally treated at 170 ◦C for 3 h i.e., identical treatment to the samples studied by single wavelength ellipsometry except that the treatment was performed in air; the second set of samples was exposed to 320 ◦C degrees for 1 h in air in order to suppress any dimensional changes under exposure to water and to remove water and organic residues from the pores.

The calculated extinction coefficients, *k*, for the films in air, water and 4 mM Cu2<sup>+</sup> solution are presented in Table S1. These *k* values are averaged over three different samples and the deviations from the average value are in the range (0.6–1) <sup>×</sup> <sup>10</sup>−<sup>3</sup> with the exception of 3 <sup>×</sup> <sup>10</sup>−<sup>3</sup> for the TEOS-only (170 ◦C) samples. Immersion does not lead to any substantial change in *k*, nor is some trend observed. This demonstrates that the absorption of the films at the wavelengths used in this study is negligible.
