fig2

Figure 2. Energy harvested from ambient heat and photons, i.e., the energy charging process. First column: images of Azo-Cl (A) and Azo-OEt (D) samples on glass slides, showing the trans-crystals at the specific temperature, cis-liquid after UV light irradiation (365 nm) and cis-liquid after cooling, as indicated by the arrows. Second column: time-evolved UV-Vis absorption spectra of Azo-Cl (B) and Azo-OEt (E) under UV light of 365 nm. The spectra were normalized with respect to the isosbestic point at 279 nm for Azo-Cl and 302 nm for Azo-OEt, respectively. The arrows indicate the order of tests performed. Third column: the cis-isomer percentage of Azo-Cl (C) and Azo-OEt (F) vs. irradiation time.