Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Single-molecule surface-enhanced Raman spectroscopy SERS has attracted increasing interest for chemical and biochemical sensing.
Many conventional substrates have a broad distribution of SERS enhancements, which compromise reproducibility and result in slow response times for single-molecule detection. Here we report a smart plasmonic sensor that can reversibly trap a single molecule at hotspots for rapid single-molecule detection. The hotspots were isolated with a monolayer of a thermoresponsive polymer poly N -isopropylacrylamide , which act as gates for molecular trapping at the hotspots. The sensor shows not only a good SERS reproducibility but also a capability to repetitively trap and release molecules for single-molecular sensing.
The single-molecule sensitivity is experimentally verified using SERS spectral blinking and bianalyte methods. Surface-enhanced Raman spectroscopy SERS is one of the few techniques that are capable of detecting and identifying chemical and biological compounds with single-molecule sensitivity 1 , 2 , 3 , 4 , 5 , 6.
This technique takes advantage of plasmonic metal nanostructures to amplify Raman signals. A unique feature of these metal nanostructures is they show a resonant oscillation of their conduction electrons on light irradiation. This light-matter interaction leads to an enormous electromagnetic field enhancement in the close vicinity of the metal surfaces. Although the importance of hotspots has been both experimentally and theoretically demonstrated for SERS sensing 1 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , the fraction of analytes adsorbed to the hotspots for a conventional SERS substrate is extremely small due to the low spatial occupation of hotspots per unit area 14 , There is therefore a prevailing need for the development of innovative SERS substrates that have a large number of uniformly distributed hotspots and the analyte molecules can be confined only at the hotspots.
Several concepts have been developed with the aim to adsorb target analytes only at the hotspots The most straightforward one is the isolation of hotspots with a chemically inert material.
