Fabrication of nanostructured zinc oxide-based gas sensor for the detection of volatile organic compounds markers of lung cancer

Lung cancer being one of the most prevalent cause of death worldwide has been extensively studied and correlated to volatile organic compounds (VOC) that are present in breath. As such, aldehydes namely pentanal, hexanal, octanal, and nonanal have endogenous origin that indicates the presence of lung cancer. Detection of these VOCs are studied with the use of nanostructured zinc oxide (ZnO) as sensing element. ZnO nanowires synthesized at optimized growth parameters using horizontal vapor phase growth (HVPG) technique was used due to its unique properties in gas sensing applications. Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray (EDX) were used to verify the growth of ZnO nanowire structures. Further characterization using Sourcemeter was used to measure its resistance and resistivity based on the I-V graph. The sensor substrate wire set-up is connected to the sourcemeter for resistance measurements as exposed to the different gas concentration of aldehydes. A simple gas sensing measurements of three sensors were done at the static headspace gas concentration of the identified VOCs. The sensor response of ZnO(1) towards different gas concentrations ranges from 5.84% to 38.08%. For ZnO(2) sensor, the sensor repsonse to different gas concentrations ranges from 7.11% to 21.87%. While for ZnO(3) sensor the sensor response values ranges from 10.01% to 68.55%. Response time varies but it was observed that octanal gas has the longest response while pentanal has the fastest response. 2D plot using principal component analysis (PCA) showed that the sensor response values of each gases is different which confirms selectivity. Sensor with close or similar resistivity also exhibit repeatable results. The characterization of the ZnO nanowire sensor towards the identified VOC markers of lung cancer is a great contribution towards the development of portable gas sensing device that may be complementary tool for screening lung cancer