Investigation on the sensing mechanism and feasibility of ITO based liquid sensor

Abstract

We proposed a new liquid sensor by using anIndium Tin Oxide (ITO)for the detection of hazardous noxious substances (HNS).Porous ITO layer was formed on a quartz substrate by a simple printing methodsubsequently characterized by using X ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM).Sensor characteristics were testedat room temperature without additional heating process. The resistance change (δR) was linearly correlated with the NH4OH concentration in the seawater solution as shown in the Fig. 1.The mechanism of sensor response has been discussed in terms of tworeactions one is the redox reaction, the other is the formation of electrical double layer (EDL) on the ITO layer surface. It revealed almost linear output signal up to theNH4OH concentrations of 15%. Sensitivity of the sensor showed small temperature dependency (dS/dT=0.083 %/oC) within 5~35oC range. Both results imply that ITO is a good candidate for liquid HNS sensor. In additionto that,to specify the chemicalexactly, we confirmedthe response of the ITOlayer along with the pH of the solution. In summary, we have investigated on the sensing mechanism and the feasibility of ITObased liquid sensor for the application to HNS detection.