Analysis of photoluminescent chromophores obtained from a cellulose acetate and silica sphere composite

Abstract Photoluminescent chromophores obtained from cellulose acetate (CA) and silica sphere composites have been analyzed with field emission scanning electron microscope (FESEM), energy dispersive spectroscope (EDS) and photoluminescence (PL) spectroscope. Acetone was used as a solvent. Two different amounts of silica spheres (0.07 and 0.14 g) were mixed in 4.0 g of the CA solution and called SCA-A and SCA-B, respectively. According to the FESEM images, after soaking silica spheres in CA solution for 6 months, both SCA-A and SCA-B have large number of nanocracks on the surface of the spheres. The chromophores (SCA-A and SCA-B) are comprised of carbon (69.2 and 65.1 wt.%), nitrogen (8.8 and 10.3 wt.%), oxygen (20.8 and 12.4 wt.%), and silicon (1.2 and 12.2 wt.%), respectively. Although there is no nitrogen source, a significant amount of nitrogen was detected by EDS. The nitrogen could have originated from the trapped or reacted ammonia during the Stober process. The amount of silicon significantly increased with the increase of silica spheres. There were three characteristic PL peaks at 2.76 eV (450 nm), 2.49 eV (497 nm), and 2.33 eV (530 nm), which were caused the luminescence peak shift with different excitation wavelengths. The luminescence peak reduced with the increase of the radiation time for SCA-A. However, the luminescence peak slightly increased with the increase of the radiation time. This result implies that the SCA-A chromophore is unstable or intermediate state to become SCA-B.