Choline chloride-based ternary deep band gap systems

The structural features derived by the UV-VIS spectroscopical analysis of five ternary eutectic systems containing
choline chloride as Hydrogen Bond Acceptor (HBA), and ethylene glycol and a second Hydrogen Bond Donor
(HBD, water, glycerol, methanol, ethanol, and 2-propanol), have been determined and described in terms of
band gap and Urbach energies (BGE and UE). In particular, the relationship between the molar composition of
the ternary eutectic systems and the BG and U energies was assessed through the Tauc plot methodology,
which revealed a peculiar behaviour of the system containing 2-propanol. Thus, a Design of Experiments
(DoE) approach, specifically a two-levels full factorial screening experiment, followed by a Surface Responding
Analysis (SRA), allowed to determine the influence of the composition and other operational parameters (temperature
and resting time) on the structural disorder of the final ternary eutectic system. An unprecedented effect
of the DES-aging was observed on the UE, indicating that the structure of these systems evolves during time by
increasing its order.