MODELLING AND RESEARCH OF THE PROPERTIES OF PLASTIC SUBSTRATES OF GAS SENSORS BASED ON SURFACE PLASMON RESONANCE

Gas sensors based on surface plasmon resonance (SPR) are used in many areas of research (biological, chemical, medical, etc.), but such research is still quite expensive. Analysis of literary sources shows that special optical glass, in particular BK-7 or SF-11, is most often used as the substrate material for the sensitive element. These materials are expensive and require complex processing technologies. The use of plastic as a substrate material is a promising approach. Numerical mathematical modeling shows that the position of the SPR angles and the sensitivity of the sensor depend on the refractive index (RI) of the substrate material. The angles shift to a larger side when the RI of the substrate decreases and also depend on the selected laser wavelength. For a laser with a wavelength of 650 nanometers, the angles shift from 41.28° to 48.08° when the RI of the material decreases. For the 850 nanometer laser, the angle shift is smaller: from 40.31° to 46.67°. The angle shift for 650 nanometers is larger, resulting in higher sensitivity. Also, the sensitivity of the sensor depends on the magnitude of the change in the RI of the gas medium. For a 650 nanometer laser, the difference is from 55.30 degrees per refractive index unit (deg./RIU) to 60.54 deg./RIU for polycarbonate and from 70.38 deg./RIU to 81.28 deg./RIU for polydimethylsiloxane. For the 850 nanometer laser, this difference ranges from 50.90 deg./RIU to 54.67 deg./RIU for polycarbonate and from 63.86 deg./RIU to 71.63 deg./RIU for polydimethylsiloxane. As a result of the study, it is shown that the use of a material with a lower RI increases the sensitivity of the gas sensor, which expands the range of its applications. The sensitive element on the polydimethylsiloxane substrate increases the sensitivity of the gas sensor by 17% compared to the gold film on the BK-7 glass substrate. In this way, the expediency of using polydimethylsiloxane as a substitute for more expensive optical glass as a substrate material for the sensitive element of gas environment sensors based on SPR has been established.