Luminescence properties of silk cocoon derived carbonaceous fluorescent nanoparticles/PVA hybrid film

• Emission color tunable carbonaceous fluorescent nanoparticles (CFNs) were synthesized by carbonizing of silk cocoon.
• Quantum yield of the CFNs is as high as 23%.
• Hybrid CFNs/PVA thin film was obtained.
• Afterglow emission from hybrid CFNs/PVA thin film was observed for the first time.

Carbonaceous fluorescent nanoparticles (CFNs) with broad particle distribution were synthesized by thermal-treatment using carbonation of silk cocoon as raw materials. The experimental results showed tunable emission wavelength of the nanoparticles. The quantum yield of the CFNs was calculated to be 23%. A CFNs/PVA hybrid thin film was prepared from a blend of the CFNs with polyvinyl alcohol (PVA) showing interesting green afterglow which could be observed by naked eyes. The afterglow spectrum revealed that the CFNs/PVA thin film had a broad afterglow emission peak located at 520 nm. The afterglow intensity decay curve of the film showed visually recognizable period longer than 140 s. The PVA–PVA hydrogen bonding in the PVA matrix may play a key role for the afterglow.