pH and thermoresponsive Ag/polyelectrolyte hybrid thin films for tunable metal-enhanced fluorescence

In this paper, Ag nanoparticles were prepared by the in situ growth of Ag seeds in polyelectrolytes multilayered film matrixes to form Ag nanoparticle-containing hybrid multilayered films. The hybrid films can realize a controllable MEF effect of adsorbed indocyanine green (ICG) fluorophores with pH- and thermoresponsive PAA/PNIPAM interlayer films. According to the interaction distance dependent nature, the nanocomposite films exhibited different MEF behaviours with the PAA/PNIPAM films of different layer numbers. Moreover, the MEF behaviour can be well tuned by varying the temperature or the pH of the external environments due to the unique responsive swelling-shrinking properties of PAA/PNIPAM interlayer films. We obtained an increase of up to 28 times for the weak fluorescence of ICG fluorophores. It is anticipated that this nanocomposite film with controllable MEF effects can be applied for responsive fluorescence detection and imaging.