Theory and applications of wide field surface plasmon resonance microscopy for discrete particles detection

Abstract

Detecting and characterizing nano-objects with low concentrations, such as biological particles, is a substantial challenge in analytical science. The wide-field surface plasmon resonance microscopy (WF-SPRM) can detect individual nano-objects in solutions and gas media bound to the sensor surface. Therefore, WF-SPRM can detect low nano-object concentrations because the image contains several square millimeters. In this work, the fundamental parameters for building highly sensitive WF-SPRM were optimized. WF-SPRM can detect individual nano-objects in solutions and gas media. Therefore, we derived a discrete particle model of SPR to describe the SPR sensor of discrete particle detection. Theoretical, numerical, and experimental analyses of the SPR detection principle were performed by considering discrete particle detection. Additionally, the influence on the SPR sensitivity of coating the gold/silver layer with a dielectric layer with varying refractive index is also studied. Different polyelectrolyte brushes, like polyacrylic acid, polyacrylic acid-polyethylene oxide, and polyacrylic acid/iodine, are used to validate the enhancement of the SPR sensitivity. Validation experiments are performed using polystyrene and silica nanoparticles of varying sizes. Finally, the surface plasmon coupling behavior between the localized surface plasmons (LSPs) of different shapes and sizes of metal nanostructures and the propagating surface plasmons (PSPs) of the metal surface is investigated by employing experimental, simulation, and theoretical approaches.