Physical and Analytical Chemistry Seminar
Lecturer: Prof. Vladimir M. Mirsky
Location: Faculty Seminar Room
Detection of nano- and microparticles of technical and biological origin by wide field surface plasmon microscopy
Detection and analysis of nano- and microparticles of different origin is an important task for chemical analytics, medical diagnostics, food industry, biotechnology, environmental monitoring and for many other fields of science and industry. For this purpose, a method based on the detection and analysis of minute signals in surface plasmon resonance images due to adsorption of single particles was developed.
The new technology allows one a real-time detection of interaction of single nanoparticles of different origin with a sensor surface. An adsorption of each nanoparticle leads to the characteristic diffraction 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 allows one to detect many hundreds of events in each frame or totally up to a million particles on the sensor surface; it leads to a very high dynamic range of counting and to a 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 (fruit juice, cosmetic formulations) was demonstrated.
To determine chemical composition of single nanoparticles separately, the wide field surface plasmon microscopy can be used as a tandem technique. For example, to analyze technical nanoparticles, it can be assisted by electrochemical system. In this case, the gold sensor surface is used both for plasmon microscopy and as a working electrode of an electrochemical cell. An application of a linear potential sweep to this electrode leads to electrochemical conversions of the nanoparticles and corresponding change in their refractive index; a 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.
The method of wide field surface plasmon microscopy can be applied for ultrasensitive detection and analysis of nano- and microparticles of biological (bacteria, viruses, exosomes), biotechnological, (liposomes, protein nanoparticles for drug delivery) or technical (metallic, oxides, plastic, etc.) origin as well as for investigation of interaction of nanoparticles with surfaces.