Project 2009

PROBLEM Development and mathematical modeling of a potentiometric ammonia gas sensor INTRODUCTION Sensor A sensor is a device that measures a physical / chemical quantity and converts into a signal which can be read by an observer or by an instrument. In a potentiometric sensor the concentration of an analyte is monitored by measuring change in potential at zero current. The potential change in the system results due to change in pH, complexation etc. during the reaction of the analyte with the detector element. Literature review A few examples of ammonia gas sensors are given below: a. An optical fiber-based [1] evanescent gaseous ammonia sensor was designed and developed. The sensing dye, bromocresol purple (BCP), was immobilized in the substitutional cladding using sol–gel process. b. Another ammonia sensor dealt with the fabrication of sensors from single-walled carbon nanotubes (SWNTs) [2] of 1.2 nm in diameters by a screen-printing method. These sensors were exposed to ammonia (NH3) gas at room temperature with nitrogen as the carrier gas. c. Pd2+ doped ZnO nanotetrapods [3] were prepared and studied for the detection of ammonia. The gas sensors developed were featured by combination of a quartz crystal as a transducer and Pd2+ doped ZnO nanotetrapods as a sensing element. Our ammonia gas sensor Most of the present ammonia gas sensors are costly (based on nanoparticles of novel metals or carbon nanotubes) or imported (field effect transistor based) or has less sensitivity (optical methods). We have planned to develop a potentiometric gas sensor for ammonia where the sensor design will be as shown in figure 1. Copper working electrode Copper reference electrode Nessler’s reagent soaked filter paper

Figure 1. schematic of proposed ammonia gas sensor Here Nessler’s reagent will be used as detector element. Ammonia will form a complex with the reagent which will result in a potentiometric response. A mathematical model of the sensor will also be developed. References 1. Sensors and Actuators B: chemical, 2006, 110(2), 252-259 (Jung Hwan Cho, Kyung Jin Na, Young Woung Kim & Gi Joon Jeon) 2. Sensors and Actuators B: chemical 2006, 113(1), 341-346(Abhay A.Sagade &Ramphal Sharma)

3. Colloids and surfaces A: Physicochemical and engineering aspects, 2006, 276 (13), 59-64(Karl Crowley & Aoife Morrin)