Statistical analysis of SERS substrate: silver nanoparticle Langmuir-Blodgett film as an example
Wei-Liang Chen1*, Yi-Hsin Huang1, Hui-Yu Cheng1, Tsung-Rong Kuo2, Yu-Ming Chang1
1Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
2College of Biomedical Engineering, Taipei Medical University, Taipei, Taiwan
* presenting author:Wei-Liang Chen,
With single-molecule sensitivity, surfaced enhanced Raman scattering (SERS) has promised to be a powerful tool from chemical analysis to bio-sensors. However, problem with large signal fluctuations to reproducibility have impeded SERS from widespread application. The fabrication of SERS substrate with large and uniform enhancement has always been a ultimate research goal for many years. In this study, we propose to perform statistical analysis to quantify the distribution and time variation of hot spots in a SERS substrate. The studied substrate consists of a monolayer of colloidal silver nanoparticle (AgNP) made with Langmuir-Blodgett (LB) technique. The synthesis of the colloidal AgNPs involves the use of polyvinylpyrolidone (PVP) as a shape controlling agent which remains on the surface of the nanoparticle. Using PVP as an analyte, we investigate the temporal and spatial variation of SERS from the hot spots of AgNP LB film by performing time-lapsed Raman mapping of a selected area of AgNP LB film, then using the total Raman signal intensity as an estimate of the SERS enhancement factor. By analyzing the enhancement probability distribution, it allows us to quantitatively characterize the performance of SERS substrates and to realize the possible mechanism causing the large enhancement variation in SERS substrates.

Keywords: SERS, spectroscopy, silver nanoparticle, Langmuir-Blodgett