Self-healable flexible luminescent films based on silk fibroin and graphene quantum dots

In this paper, thermally-stable, biocompatible and flexible luminescent films with self-healing capability were prepared by combining graphene quantum dots (GQDs) and silk fibroin (SF). Two methods were carried out to combine GQDs and SF: one is to feed silkworms with a GQDs diet and collect their cocoons; the other is to mix GQDs with SF solution directly. Then feeding GQDs/SF composite film and GQDs/SF mixing films of different mass ratios were prepared by natural air drying. The morphology, structure and performance of the SF films were characterized in detail. Results showed that the mixing composite films are flexible, luminescent and thermally stable. The more GQDs in the film, the stronger the luminescence is, in our case. The mixing films exhibit different light color under different excitations, the same with GQDs. However, fed GQDs in the silkworm seem to be playing a quenching effect on SF. It also showed that no new chemical bonds were formed between GQDs and SF, and the two were physically mixed, either by feeding or direct solution mixing. In addition, this fluorescent film also has the particular ability of self-healing by a drop of water. This new biocompatible film may have broad applications in fields of flexible display, biosensing, drug delivery and tissue engineering.