The l-LSPR band of AuNRs typically appears in region (3), is more suitable for light harvesting, and its position can be precisely tuned during synthesis. It is also spectrally well-separated from Azo bands as presented for AzoGly-Au-2-CNFs. In summary, our approach enables efficient preparation of stable, hybrid materials with well-defined optical characteristics and maintained The main functionalities of any Azo-containing material are its photoswitchability, photo-, and thermostability (Figure ). Hence, to describe the photochromic behaviour, we subjected AzoGly-Au-2-CNFs hybrid sample to the alternate induction of the E-Z and Z-E isomerization of the photochromic component (Figure , left). The drop of the π→π * band upon UV (365 nm) irradiation and its rise upon irradiation at 436 nm (Figure ) indicate the occurrence of E-Z and Z-E isomerizations, respectively (Figure , right). The observed changes are coherent with photoswitching of pristine AzoGly (Figure ) and AzoGly-CNFs control sample (Figure ).