Large-Scale
Hot Spot Engineering for Quantitative
SERS at the Single-Molecule Scale
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Abstract
Quantitative surface enhanced Raman
spectroscopy (SERS) requires
precise control of Raman enhancement factor and detection uniformity
across the SERS substrate. Here, we show that alkanethiolate ligand-regulated
silver (Ag) nanoparticle films can be used to achieve quantitative
SERS measurements down to the single-molecule level. The two-dimensional
hexagonal close-packed superlattices of Ag nanoparticles formed in
these films allow for SERS detection over a large area with excellent
uniformity and high Raman enhancement factor. In particular, the SERS
signal from the thiolate ligands on Ag nanoparticle surfaces can be
utilized as a stable internal calibration standard for reproducible
quantitative measurements. We demonstrate the capability of quantitative
SERS by measuring the areal densities of crystal violet molecules
embedded in an ultrathin spin-on-glass detection “hot zone”,
which is a planar and uniformly enhanced region several nanometers
above the Ag nanoparticles. The Raman measurement results exhibit
a linear response over a wide dynamic range of analyte concentration