Monitoring biomolecular interaction with 1-d plasmonic nanostructure by using dark field microscopy

This study presents an imaging technique combining multi-functional dark field microscopy (DFM) with spectroscopy to image the nanostructures of different formats of optical disks and identify their optical properties by absorption spectra. The resolution of this DFM system is determined using one-dimension nanostructure with lengths from 160 nm to 600 nm. The pattern sizes are confirmed by atomic force microscopy (AFM). The results show that DFM resolution is about 160 nm with the current setup, and the resulting DFM image size appears to be slightly larger than a AFM image. We then deposited a 50 nm gold film on top of these nanostructures and measured their absorption spectra to identify the relationship between surface plasmon resonance (SPR) spectra and one-dimensional nanostructures. The immobilization of streptavidin on the surface of the gold-coated nanostructure causes changes in the absorption spectrum ranging from 450nm to 650nm.