SERS mapping in langmuir-blodgett films and single-molecule detection

Research output: Contribution to journalArticle


Plasmon-enhanced spectroscopic techniques have expanded single-molecule detection (SMD) and are revolutionizing areas such as bio-imaging and single-cell manipulation. Surface-enhanced (resonance) Raman scattering (SERS or SERRS) combines high sensitivity with molecularfingerprint information at the single-molecule level. Spectra originating from single-molecule SERS experiments are rare events, which occur only if a single molecule is located in a hot-spot zone. In this spot, the molecule is selectively exposed to a significant enhancement associated with a high, local electromagnetic field in the plasmonic substrate. Here, we report an SMD study with an electrostatic approach in which a Langmuir film of a phospholipid with anionic polar head groups (PO 4 -) was doped with cationic methylene blue (MB), creating a homogeneous, two-dimensional distribution of dyes in the monolayer. The number of dyes in the probed area of the Langmuir-Blodgett (LB) film coating the Ag nanostructures established a regime in which single-molecule events were observed, with the identification based on direct matching of the observed spectrum at each point of the mapping with a reference spectrum for the MB molecule. In addition, advanced fitting techniques were tested with the data obtained from micro-Raman mapping, thus achieving real-time processing to extract the MB single-molecule spectra.


  • Pedro H.B. Aoki
  • Eduardo G.E. Carreon
  • Diogo Volpati
  • Milton H. Shimabukuro
  • Carlos J.L. Constantino
  • Ricardo F. Aroca
  • Osvaldo N. Oliveira
  • Fernando V. Paulovich
External organisations
  • São Paulo State University
  • University of São Paulo
  • University of Windsor
Research areas and keywords


  • SERS, Single-molecule detection (SMD), Visual data exploration
Original languageEnglish
Pages (from-to)563-569
Number of pages7
JournalApplied Spectroscopy
Issue number5
Publication statusPublished - 2013 May 1
Publication categoryResearch
Externally publishedYes