The effect of measurement parameters on the performance of the sensors in the detection of organic compound vapours

Abstract

We reported the successful fabrication of sensors composed of three sensing materials, TiO2, CNPs and CA. The sensing materials were characterised using XPS, P-XRD and HRTEM. Three sensors were fabricated by varying the mass of TiO2 in the composites (mass ratio of 1:1:3, 3:1:3, and 6:1:3). The fabricated sensors were exposed to mesitylene, octanal, 3-pentanone and 4-methyl-1-hexene vapours at room temperature. The sensors response were measured using two parameters, relative resistance (ΔR) and impedance (ΔZ) at 25 kHz. The sensor with a high concentration of TiO2 in the composites (sensor C mass ratio of 6:1:3) did not respond to any of the analyte vapour at all, however, the remaining two sensors did respond to all the analyte vapour except 4-methyl-1-hexene vapour and were highly sensitive towards to mesitylene and octanal vapour. A direct relationship between the sensitivity of the sensors and the number of electrons produced during the redox reaction by the analyte vapour was observed. With the high number of electrons produced by the analyte the sensors become more sensitive towards the analytes. The sensitivity of the sensors towards the analytes depends on the choice of parameters, by changing the resistance parameter to impedance, we did observe that sensor A became highly sensitive towards octanal vapour. The sensors response and recovery time were also studied and was found that the response time was faster in the impedance parameter but slow in recovery time. On the contrary, the recovery time was shorter in the resistance parameter.

Keywords

• Solid-state sensor
• Chemi-impedance
• Metal oxides
• Sensitivity
• VOCs