Broadband SERS Enhancement by DNA Origami Assembled Bimetallic Nanoantennas with Label-Free Single Protein Sensing

Engineering hotspots in surface-enhanced Raman spectroscopy (SERS) through precisely controlled assembly of plasmonic nanostructures capable of expanding intense field enhancement are highly desirable to enhance the potentiality of SERS as a label-free optical tool for single molecule detection. Inspired by DNA origami technique, we constructed plasmonic dimer nanoantennas with a tunable gap decorated with Ag-coated Au nanostars on origami. Herein, we demonstrate the single-molecule SERS enhancements of three dyes with emission in different spectral regions after incorporation of single dye molecules in between two nanostars. The enhancement factors (EFs) achieved in the range of 10(9)-10(10) for all the single dye molecules, under both resonant and nonresonant excitation conditions, would enable enhanced photostability during time-series measurement. We further successfully explored the potential of our designed nanoantennas to accommodate and detect a single thrombin protein molecule after selective placement in the wide nanogap of 10 nm. Our results suggest that such nanoantennas can serve as a broadband SERS enhancer and enable specific detection of target biological molecules with single-molecule sensitivity.

Automated summary

Engineering hotspots in surface-enhanced Raman spectroscopy (SERS) by precisely controlling the assembly of plasmonic nanostructures can enhance the potential of SERS for single molecule detection. Plasmonic dimer nanoantennas with tunable gaps showed significant enhancements for single dye molecules, and were able to detect a single thrombin protein molecule in a 10 nm wide nanogap. These engineered nanoantennas have the potential to serve as a broadband SERS enhancer for specific detection of biological molecules with single-molecule sensitivity.