“Nanobiotechnology for health-care”

Estimation of surface plasmon resonance conditions in optical sensors according to the Kretschmann scheme
A.D. Suprun, L.V. Shmeleva
 Department of Theoretical Physics, Faculty of Physics, Taras Shevchenko National University of Kyiv. Volodymyrska Street, 64/13, Kyiv-01601, Ukraine. 
E-mail: lshmel@univ.kiev.ua 

In the study of surface plasmon resonance (SPR) in optical sensors according to Kretschmann scheme, the structure "prism - metal nanolayer - air" is often considered. Such a structure is especially often considered in cases where test or illustrative calculations or measurements are performed.  Real sensors require the use of specific dielectrics or even dielectric mixtures. For example, in biosensors, the medium being analyzed (analyte) is a complex structure. Here water is the basic component. It transports a second component. This component is biological objects (such as viruses) called ligands. The ligand is adsorbed by the third component. It is called a receptor (proteins, DNA, etc.) and is rigidly attached to the metal nanolayer. As a result, the permittivity of the connected system the receptor plus ligand is changes. This is how the sensory effect is manifested.
In our research, the two most important characteristics of SPR for the system "prism - gold nanolayer - water" were calculated. These are the wavelength and resonant angle of incidence. Purpose of the research was to analyze the influence of water (the basic component in the biosensor analyte) on the wavelength and resonance angle of incidence in the gold nanolayer. The influence of water temperature on these characteristics is analyzed. The prospects of a production the measurer of laser radiation flow by a changing temperature of the analyte, which rises under the influence of laser radiation, in the Kretschman scheme are considered.
There are no such measurers today. It is fixed that the SPR wavelength can vary from 543 to 539 nm depending on the temperature in the range 0º – 100ºС. At the same time, the resonant angle of incidence varies from about 43º to 42º. This position of the angle (~ 43º at normal temperature conditions) corresponds to observations, and the range of change in 1º can be experimentally registered. The range of possible measurements of the magnitude of the radiation flux in the structure “prism - gold nanolayer - water” was also found. This range is 1–25 W/cm², in the temperature range 0º–100ºC.  Reserves found to extension this range.