Multi-band Broad Emission Properties of Fluoren-9-one Oxime Chemically and Physically Confined in a Photoactive Polyphenylsilsesquioxane Network Matrix

The fluoren-9-one oxime luminophore (FO) was covalently incorporated into a photoactive polyphenylsilsesquioxane matrix (PSQ) by an in situ two-step process using different molar ratios of FO and C₆H₅SiCl₃ in an aprotic solvent in the presence of triethylamine base. The infrared (FT-IR), electronic (UV–Vis) and photoluminescence (PL) studies of these materials are reported. Their infrared spectra at room temperature and softening properties suggest that the PSQ matrix adopts a ladder structure rather than a polyhedral cubic cage. The phenyl-based PSQ matrix (C₆H₅PSQ) fluoresces in the violet region at ~325 nm when photo-excited at 270 but relatively photo-passive if excited at 320 nm. However, the untethered free FO luminophore exhibits multi-band PL properties with two intense overlapping emission bands in the blue–green region at 450 and 474 nm, and a moderately intense violet band at 340 nm which suggests the existence of multiple excited states. However, the FO–C₆H₅PSQ composite systems emit violet and blue-greenish light centered, respectively, at ~330 and ~470 nm when photo-excited at 270 nm. On the other hand the violet band was found to disappear when the composites are excited at 320 nm. The blue-greenish band remains irrespective of the mode of FO incorporation into the PSQ matrix being covalently attached or physically doped. PL studies on these materials show that emission by the PSQ matrix has an observable effect on broad band emission of the FO luminophore centers.