Disordered plasmonic substrate-based wide-field super-resolution imaging

We have investigated the feasibility of disordered plasmonic nanocomposites for super-resolution imaging. Annealing-based nanocomposite substrate has a great potential in biomedical optical and sensing technology because it can be mass-produced without difficult manufacturing processes. We introduce a new approach for wide-field super-resolution fluorescence imaging based on the nanocomposite island substrates, which we call nanospeckle illumination microscopy (NanoSIM). Near-field speckle patterns produced on disordered nanoisland substrates can help reconstruction of high-resolution fluorescence images with appropriate basis images. We have acquired basis images using azimuthal scanning illumination (ASI). Each ASI produces nonuniform nanoscale near-field speckles which can excite fluorescent dyes within a subdiffraction-limited area. While exploiting the random nature of plasmonic nanocomposite, NanoSIM does not require any specific polarization state to be maintained for ASI. We have tested NanoSIM to obtain super-resolved mages of molecules on the HeLa cell membrane. The full-width-at-half maximum was shown to improve by more than three times over the diffraction-limit with 360 basis images. Reconstructed images of gangliosides distribution on the HeLa cell suggest that fewer basis images may produce almost the same resolution with a shorter computation time. The optical resolution and sensitivity of disordered plasmonic substrate can be further enhanced by controlling the geometrical features of nanoislands structure.