Nonanal Sensor Fabrication Using Aldol Condensation Reaction Inside Alkali-Resistant Porous Glass

Monitoring the gases released during breathing or via the skin has gained significance towards diagnosing diseases. In this study, a sensor chip capable of detecting nonanal gas, which is known to be a marker of lung cancer, was developed. The gas detection agent used was vanillin, which underwent aldol condensation with nonanal in the presence of a basic catalyst, resulting in the formation of an unsaturated aldehyde. Porous glass was used as the reaction field to carry the detection agent. Alkali-resistant porous glass was chosen because conventional porous glasses show low durabilities under basic conditions, as they primarily consist of SiO₂. Nonanal can be detected through changes in the absorption spectrum of the sensor. An accumulate-type sensor was used in this study, which exhibited a linear relationship between the degree of absorption changes at 470 nm and nonanal concentration in the 60 ppb-1.3 ppm range. Therefore, this biological marker gas sensor is effective for the early diagnosis of diseases. The alkali-resistant porous glass sensor chip exhibited a higher degree of absorption change than the conventional porous glass sensor chip.