Figure 4
From: Single molecule detection from a large-scale SERS-active Au79Ag21 substrate
Single molecule detection of DNA adenine molecules.
(a) Typical Raman map of adenine (10−9 M) (left), corresponding optical microscopic image (middle) and their overlay image (right). The hot spots can be directly observed at the narrower gaps of the wrinkled nanoporous film. (b) Fluctuation field intensity with 3 chained hot spots (adenine 10−9 M). The configuration is analogous to the “superlenses” with a linear chain of nanocavities suggested by computer simulations30. Raman map size: 4.0 × 5.5 μm2. The spectral interval is 250 nm. (c) SERS spectrum of 10−9 M adenine taken from a hot spot. (d) Single molecule SERS spectrum of 10−12 M adenine with selective Raman bands. The laser excitation is 785 nm.
