Fabrication of freestanding silk fibroin films containing Ag nanowires/NaYF₄:Yb,Er nanocomposites with metal-enhanced fluorescence behavior

Abstract

Solar cells containing upconversion nanoparticles (UCNPs) used as a power source in biomedical nanosystems have attracted great interest. However, such solar cells further need to be developed because their substrate materials should be biocompatible, flexible and highly luminescent. Here, we report that freestanding silk fibroin (SF) films containing a mesh of silver nanowires (AgNWs) and β-NaYF4:Yb,Er nanocrystals with metal-enhanced fluorescence behavior can be fabricated. The freestanding composite films exhibit properties such as good optical transparency, conductivity and flexibility. Furthermore, they show significantly enhanced upconversion fluorescence due to surface plasmon polaritons (SPPs) of AgNWs compared to the SF-UCNP films without AgNWs. The freestanding composite films with metal-enhanced fluorescence behavior show great promise for future applications in self-powered nanodevices such as cardiac pacemakers, biosensors and nanorobots.

Recent progress in the development of upconversion nanomaterials in bioimaging and disease treatment

“…Noble metals such as a silver shell modified on the surface of UCNPs can enhance UCL efficiency by surface plasmon coupled emission to produce a multimodal hybrid material, which can be used for photothermal therapy [ 121 ]. By adjusting the thickness of the silver layer, the wavelength of the UCNP surface plasmon resonance can be adjusted to 980 nm, and bioimaging by upconversion emission can be performed simultaneously under single wavelength illumination [ 122 ]. Similarly to the magnetite nanoparticle modification method, silver nanoparticles occupy the thiol group on the surface of the UCNP for nucleation behavior.…”

Emerging plasmonic nanostructures for controlling and enhancing photoluminescence

“… 34 When UCNP-nanorod heterodimers were excited with light polarised along the longitudinal axis of the Au nanorod, a two-fold luminescence signal intensity increase was observed in single-particle measurements. The same nanocrystals hybridised with Ag nanowires were harnessed as a potential power source for solar cells in optically transparent free-standing silk fibroin films, 35 with precise and reliable distance control between UCNPs and nanoantennae achieved using polyelectrolyte multilayers as tuneable dielectric spacers. 36 Once the LSPR absorption wavelength was matched with the excitation wavelength of UCNPs, a maximum 23-fold enhancement was accomplished using an 8 nm spacer.…”

Wet‐Spinning Fabrication of Flexible Conductive Composite Fibers from Silver Nanowires and Fibroin

“…Accordingly, the diameter, morphology, and mechanical properties of the obtained RSF fibers can be conveniently modified . The spinning process is also able to endow the fibers with diverse optical, electrical, and biofunctional properties by the addition of various functional fillers during fabrication . In the case of conductive RSF fibers, some pioneering studies have been published.…”

“…15 The spinning process is also able to endow the fibers with diverse optical, electrical, and biofunctional properties by the addition of various functional fillers during fabrication. 2,16,17 In the case of conductive RSF fibers, some pioneering studies have been published. For example, Fang et al fabricated tough regenerated silk fibers with multiwalled CNTs via a wetspinning process.…”