Thesis is devoted to the study of the properties of metal nanoparticles based on silver and gold, as well as chalcogenide clusters incorporated into the polymer matrix.
A new direction of analytical technology is the development of biosensors – bioanalytical devices that combine the best features of bioelements (selectivity), as well as physical transducers (high sensitivity and accuracy). One of the most important problems of biosensor technologies is the formation of a biorecognizable membrane that contains immobilized bioelements, in particular enzymes. Biosensors are not only the subject of basic and applied research, but also an important commercial product of industrialized countries.
In recent years, the use of nanosized materials in combination with bioselective elements (enzymes) for the development of technologies for the production of bionanomaterials with catalytic properties is of particular interest. This is due to the fact that the main features of nanosized materials are that they have a large surface area, the ability to adsorb, the formation of strong bonds with adsorbed particles and high electrochemical activity. Increased ability to ion exchange allows the creation of bionanoparticles (bound enzymes on the surface of nanoparticles) with their subsequent use in biosensors. It is expected that the nanocomposite layers, in which the polymer matrix is the base implanted with metal nanoparticles and/or semiconductor clusters, will retain the immobilized enzyme well in the middle of the biorecognizable film and will have improved electrochemical and mechanical properties. It is assumed that the modification of such nanocomposite layer of working electrodes will combine the total ability of nanoparticles/clusters and the enzyme to promote enzymatic and electrochemical reactions, as well as increase the life of the coated bioelectrode.
Development of new polymeric materials with the necessary characteristics and their subsequent application in biosensors is of fundamental importance. The development of nanotechnology allows creating bioselective elements based on metal nanoparticles and semiconductor clusters. Such approaches help to achieve a high concentration of the enzyme in the biorecognizable membrane, and thus expand the range of linearity and increase the sensitivity and selectivity of the biosensor to the studied analytes. Therefore, the study of the properties of metal nanoparticles and semiconductor clusters in polymer composites is an urgent problem, in particular, for the creation of highly efficient biosensor systems.
In the thesis, the regularities of the evolution of silver ions implanted in a pure polymer matrix and a polymer matrix containing chalcogenide clusters are established. By using local X-ray spectral analysis, it is found that implanted silver ions are adsorbed by As2S3 clusters. Thus, hybrid systems As2S3+Ag are formed, which play an important role in the creation of new amperometric biosensors. A kinetic model of the formation of hybrid systems As2S3+Ag in a polymer matrix is proposed. This takes into account the role of radiation-stimulated diffusion of implanted silver ions, which establishes a stationary uniform distribution of silver ions in the process of ion implantation. Thus, in the layers surrounding the chalcogenide clusters, the ion density is the same as in the surrounding space. The solution of the kinetic equations gives the dose dependence of the accumulation of adsorbed Ag ions in chalcogenide clusters and the formation of As2S3+Ag clusters. The interaction of Au nanoparticles with the enzyme laccase is studied. The optimal ratio of nanoparticle and enzyme volumes is determined. A nonlinear relationship is established between these volumes by which the volume of bound enzyme on which its catalytic activity depends can be regulated. The catalytic properties of gold nanoparticles depending on their size and structure are studied. It is found that the enzymatic effect increases with decreasing size of gold nanoparticles, provided that their crystal structure is preserved. Therefore, XRD analysis of gold nanoparticles was performed to confirm their crystal structure. Studies showed an increase in the sensitivity of bioelectrodes of laccase-based amperometric biosensors using enzyme-bound gold nanoparticles. These bionanoparticles combine with the polymer matrix of the ureasil/As2S3 composite, forming a polymer-enzyme-metal nanoparticles system that enables the sensor to function. It is shown that the discovered properties of silver and gold nanoparticles can be used to improve and create new biosensor systems.
