Nano Endoscopy with Plasmon-Enhanced Fluorescence for Sensitive Sensing Inside Ultrasmall Volume Samples.

Plasmon-enhanced fluorescence (PEF) generally requires the samples settled on a metal substrate and the effective enhancement distance is less than 100 nm, which limit its application in intracellular sensing. Herein, we report a nano endoscopy with PEF effect for sensing analytes inside the extremely small volume samples. The nano endoscopy was fabricated by assembling single nanoporous gold nanowire (PGNW) on the tip of a tungsten needle. It was accurately manipulated to insert into a micro droplet, and an effective sensing was realized at micrometre scale with submicrometer resolution. By taking lysozyme as a model sensing target, a 23-fold improvement of sensitivity was obtained, comparing with that of smooth gold nanowire (SGNW). These results indicated that the nano endoscopy can realize a high spatial resolution sensing, showing its potential application in intracellular sensing.