Luminous composite ultrathin films of CdTe quantum dots/silk fibroin co-assembled with layered doubled hydroxide: Enhanced photoluminescence and biosensor application

Abstract

Quantum dots (QDs) luminescent films are extensively applied to optoelectronics and optical devices. However, QDs aggregation results in the quenching of their fluorescence property which limits their practical applications to a greater extent. In order to resolve this issue, 3-mercaptopropionic acid (3-MPA) functionalized Cadmium Tellurium (CdTe) QDs were stabilized by silk fibroin (SB) and co-assembled with layered doubled hydroxide (LDH) to form (QDs@SF/LDH)n ultrathin films (UTFs) via the layer-by-layer (LBL) technique. UV–Vis absorption and fluorescence spectroscopy showed a stepwise and normal growth of the films upon increasing the number of deposition cycles. XRD and AFM studies confirmed the formation of a periodic layered structure and regular surface morphology of the thin films. As compared to (CdTe QDs/LDH)nUTFs, the (CdTe QDs@SF/LDH)nUTFs displayed fluorescence enhancement and longer fluorescent lifetime, both in solid states and aqueous solutions. Furthermore compared with the solution state, the fluorescence enhancement of SF-RC and SF-β are, respectively, 7 times and 17 times in the (CdTe QDs@SF/LDH)n UTFs, indicating that the LDH nanosheets favor the fluorescence enhancement effect on the CdTe QDs@SF. The fabricated materials displayed fluorescence response to a biological molecule such as immune globulin, lgG. Thus, the (CdTe QDs@SF/LDH)n UTFs has a potential to be used as biosensor. Keywords: CdTe quantum dots, Silk fibroin, Layered doubled hydroxide, Co-assembly, Fluorescence enhancement