Naked eye plasmonic indicator with multi-responsive polymer brush as signal transducer and amplifier.

For decades, plasmonic nanostructures have been used as important optical sensing platforms, however, the necessity of sensitive optical instruments for detection greatly limits their practical application. Herein, a multi-responsive naked eye plasmonic indicator has been prepared through introduction of a responsive polymer brush (PNIPAm) into the cavity of a Ag nanovolcano array (Ag NVA). According to the phase change of the PNIPAm brush under different external conditions, the as-prepared Ag NVA shows responsive monochromatic colors, which allow the Ag NVA to serve as a plasmonic indicator detected by the naked eye. Importantly, the as-prepared Ag NVA also possesses a rapid response rate as well as excellent repeatability, and is compatible with conventional micro-fabrication methods. All of these excellent features make the as-prepared Ag NVA an attractive candidate for future optical indicating and intelligent color display applications.