Anatoli A. Beloglazov

Surface plasmon resonance interferometry for biological and chemical sensing

Abstract Surface plasmon resonance (SPR) interferometry is reported as a novel technique for biological and chemical sensing, which employs not only the amplitude of a resonantly reflected light wave, but its phase as well. In this connection, the phase behavior under SPR has been comprehensively described by theoretical analysis, numerical simulations, and a number of experiments. Near optimum SPR conditions, a resonant phase dependence is step-like, the ‘step’ being at the reflectivity minimum. For SPR-based sensors, the slope of the ‘step’ can always be made by several orders steeper than that of the resonant reflectivity contour. The ‘step’ has been imaged by the fringe of a 2-dimensional interference pattern where one coordinate was the incidence angle, and the other was the phase. The inversion of the ‘step’ has been observed for the first time during antigen–antibody binding, when the system passes through the optimum SPR conditions. Monitoring the inversion provides for ultra-high sensitivity to an analyte while recording angular position of the ‘step’, does for dynamic range as wide as that of traditional SPR sensors. The SPR interferometry technique has confirmed theoretical findings and opened up new possibilities for (bio)chemical sensing.

Phase-polarisation contrast for surface plasmon resonance biosensors.

A technique of phase-polarisation contrast (PPC) for the enhancement of the contrast of a surface plasmon resonance (SPR) intensity profile is proposed and experimentally realised. The technique exploits the peculiarities of light phase and polarisation behaviour under SPR. It applies to non-optimum SPR coupling conditions and enables one to lower the resonant minimum of reflected intensity nearly to zero, and hence to increase substantially the ratio of the intensity from the resonance to that at the minimum. We observed the contrast enhancement by more than one order of magnitude when we applied the PPC scheme. The PPC can be efficiently employed in commercial SPR sensors, as it significantly reduces restrictions on allowable parameters of SPR-supporting metal films and biomolecular layers immobilised on them, facilitates SPR observation, and increases the accuracy of SPR shift measurements.

Silicon-based surface plasmon resonance chemical sensors

Abstract A silicon-based surface plasmon resonance (SPR) technique has been successfully applied to NO2 sensing at ppm level using devices with uncoated and phthalocyanine-coated gold films. Surface-enhanced Raman scattering (SERS) has been used as an additional data-acquisition channel capable of providing spectroscopic selectivity and amplified sensitivity. Reversible responses of both SERS and SPR-induced photosignals produced by Au-on-Si grating structures coated with thin 18-crown-6 H2pc phthalocyanine films are simultaneously recorded for exposures of the films to 10 ppm of NO2 in air. Possible sensing applications are discussed.

Carbon nitride — prospects for ultimate performance of superhard materials

Abstract In order to deposit thin solid films containing covalently bonded carbon nitride as a major matrix component, several different techniques for deposition were explored. They included reactive pulsed laser deposition, reactive DC magnetron sputtering and laser ablation of a frozen ethanol/liquid N2 double layer system. Surface analysis techniques showed that the concentrations of nitrogen were as high as 20 to 25 at% in the bulk and up to 40 at% in the upper layers of the resulting a-C a-CN x films. The covalent bond of nitrogen to carbon was identified. It is similar to the nitrogen bonds in silicon nitride and boron nitride.

Study of biochemical reactions in thin organic films by means of evanescent optical wave

Abstract An optical biosensor has been developed for detection of pesticides, based on the evanescent optical wave technique. The concentration of the pesticide was measured in liquid. We specially originated a core complex of photosystem II film on a cheap disposable element. A setup on the basis of the Kretschmann arrangement was improved by using a computer-controlled angular scanning system. The detection concentration limits were 10−11 M for dinitrophenole and 10−10 M for paraoxon. The results obtained show the perspective of the integral method for detection of different kinds of pesticides at extremely low concentration levels of 0.1 ppb.

Silicon-based surface plasmon resonance combined with surface-enhanced Raman scattering for chemical sensing

A Si-based surface plasmon resonance (SPR) technique has been successfully applied to NO2 sensing at ppm level, with estimated detectability at less than 100 ppb. Surface-enhanced Raman scattering (SERS) has been used in this scheme as an inherent additional data acquisition channel capable of providing spectroscopic selectivity and amplified sensitivity. The behavior of both the SERS spectrum and the SPR-induced photosignal produced by Au-on-Si grating structures coated with thin 18-crown-6 metal-free phthalocyanine films was simultaneously recorded for exposure of the films to 10 ppm of NO2 in air and its reversal in clean air. Both responses have been found to be reversible. The combination of Si-based SPR and SERS looks promising for thin-film and surface explorations, both in fundamental and sensor applications.

Optoelectronical gas sensors based on surface plasmon resonance in Si-structure

The concept of surface plasmon resonance chemical sensors based on Si substrate is developed which combines a number of advantages of both optical and microelectronical approaches to investigate gaseous media. This type of the gas sensor has been made and tested for the first time. A reversible response to ntirogen dioxide at the level of ppm concentrations has been recorded.

Pesticide sensing by surface-plasmon resonance

An optical biosensor has been developed for detection of pesticides, based on surface plasmon resonance (SPR) technique. Concentration of the pesticides was measured in liquid or gas. We specially originated organic film on a disposable element. A setup on the base of Kretschmann arrangement was improved by using a computer-controlled angular scanning system. The detection concentration limit of dinitrophenole (DNP) was 10-9 M. Some samples exhibited effect down to 10-11 M of DNP. The results obtained provide reason for further development of SPR sensor as applied to pesticides monitoring.