The technology of Wide Field Surface Plasmon Microscopy (WF-SPRM) provides a real-time detection of interaction of single nanoparticles of different origin with a sensor surface. Adsorption of each nanoparticle leads to a characteristic image whose intensity depends on the size and chemical composition of the particle. A number of the nanoparticle – surface binding events per time and surface area characterizes volume concentration. A large monitored surface area of the sensor surface (~1.2 mm2) allows one to detect many hundreds of binding events in each frame or totally up to a million particles on the sensor surface; this leads to the very high dynamic range of counting and to the correspondingly high dynamic range in the concentration scale. Depending on the type of particles and experimental conditions, the detection limit for aqueous samples can be below 100 nanoparticles per microliter. Stable analysis of nanoparticles in very complex environments (wines, fruit juices, cosmetics) was demonstrated. To determine chemical composition of single nanoparticles, the WF-SPRM was coupled with electrochemical analysis: applying a linear potential sweep, the adsorbed nanoparticles can be subjected to electrochemical conversion, leading to the change of their refractive index; the value of the electrical potential of this conversion characterizes the material of the particular nanoparticle. Notably, such analysis is performed simultaneously but independently for each adsorbed particle.
Although the WF-SPRM technology was initially developed for analytics of engineered nanoparticles, it can be also applied in many other fields of science, for example, in bioanalytics (detection of viruses, liposomes, exosomes, bacteria), colloid chemistry (investigation of interaction of colloid particles with different surfaces) or electrochemistry (investigation of initial stages of electrochemical nucleation).