High-Throughput Imaging and Spectral Analysis of Gold Nanoparticles Through Waveguide Excitation

A waveguide (WG) excitation-based hyperspectral imaging (HSI) system equipped with a white-light source and Fourier transform spectrometer is presented. Both the microscopic images and spectra of spatially resolved gold nanoparticles (AuNPs) with sizes from 60 to 100 nm are taken at selected pixels. This system is also compared with the conventional one based on dark-field (DF) excitation using the same microscopic imaging setup. The spectral peaks and linewidths of imaged AuNPs are verified with finite-difference time-domain (FDTD) calculations. The high-throughput capability of our system is demonstrated with the bulk and surface refractive index (RI) sensing of AuNPs. The measured bulk wavelength sensitivity depends on the size of AuNPs and ranges from 120 to 262 nm/RIU for sizes between 60 and 100 nm. The surface RI sensing of AuNPs shows an index change of about 0.01 RIU for a three-layer stack of bovine serum albumin (BSA) adsorbed on 100-nm AuNPs, which agrees with our estimation.