Highly- sensitive to n-hexane vapors SPR sensor with an additional ZnO layer

Abstract

Offered, developed and experimentally tested in this work is the multilayer element highly sensitive to n-hexane vapors. This element is aimed to be used in the surface plasmon resonance (SPR) sensor with a plasmon-carrying gold layer covered with a sorption layer of zinc oxide (ZnO). The bandgap width inherent to these layers prepared using sol-gel technology reached Eg = 3.198...3.3 eV, in dependency on the oxide layer thickness. The bulk porosity of the layers was 15.5 up to 69.5 vol.%, also in dependency on the oxide layer thickness. The surface micro-roughness of ZnO layer with the optimal thickness close to 20 nm was increased by 4.4 times as compared with that of pure gold surface without ZnO layer. Sensory properties of sensitive elements were studied relatively to vapors of the following solvents in air: isopropanol, acetone and n-hexane. The highest sensitivity of the sensor was inherent to n-hexane. The response of SPR sensor, when using the additional ZnO layer of the optimal thickness 20 nm, was 4-fold increased from 247 up to 952 ang.sec., if comparing with the sensor without ZnO layer. The selectivity to hexane as compared with that for isopropanol and acetone in the case of the of ZnO-modified sensor was enhanced practically 2-fold from 3.1 up to 5.6 times. The obtained results can be applied to monitor n-hexane vapors in air.