Australian and Italian researchers have developed a smart sensor that can detect single molecules in chemical and biological compounds – a highly valued function in medicine, security and defence.
The researchers from the University of New South Wales, Swinburne University of Technology, Monash University and the University of Parma in Italy used a chemical and biochemical sensing technique called surface-enhanced Raman spectroscopy (SERS), which is used to understand more about the make-up of materials.
They were able to greatly amplify the technique’s performance by taking advantage of metal nanostructures, which help generate ‘hotspots’ in close proximity to the metal surfaces.
Ref: Reversible gating of smart plasmonic molecular traps using thermoresponsive polymers for single-molecule detection. Nature Communications (9 November 2015) | DOI: 10.1038/ncomms9797
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 sensor was fabricated through electrostatic self-assembly of gold nanoparticles onto a gold/silica-coated silicon substrate, producing a high yield of uniformly distributed hotspots on the surface. 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.