Label-Free Imaging of Single Nanoparticles Using Total Internal Reflection-Based Leakage Radiation Microscopy

Label-free, fast, and single nanoparticle detection is demanded for the in situ monitoring of nano-pollutants in the environment, which have potential toxic effects on human health. We present the label-free imaging of single nanoparticles by using total internal reflection (TIR)-based leakage radiation microscopy. We illustrate the imaging of both single polystyrene (PS) and Au nanospheres with diameters as low as 100 and 30 nm, respectively. As both far-field imaging and simulated near-field electric field intensity distribution at the interface showed the same characteristics, i.e., the localized enhancement and interference of TIR evanescent waves, we confirmed the leakage radiation, transforming the near-field distribution to far-field for fast imaging. The localized enhancement of single PS and Au nanospheres were compared. We also illustrate the TIR-based leakage radiation imaging of single polystyrene nanospheres with different incident polarizations. The TIR-based leakage radiation microscopy method is a competitive alternative for the fast, in situ, label-free imaging of nano-pollutants.

SURFACE PLASMON EXCITATION AND MANIPULATION IN DISORDERED TWO-DIMENSIONAL NANOPARTICLE ARRAYS

We present experimental and numerical results of simultaneous surface plasmon polariton (SPP) excitation and in-plane manipulation with random arrays of gold nanoparticles. The recorded images were obtained by using leakage radiation microscopy (LRM) for the excitation wavelength of 633 nm and for different densities of particles. The numerical model makes use of a composed analytic Green dyadic which takes into account near- and far-field regions, with the latter being approximated by the part describing the scattering via excitation of SPP. The LRM optical images obtained are related to the calculated SPP intensity distributions demonstrating that the developed approach can be successfully used in studies of systems of closely spaced arrays.