1. IMPROVED PERFORMANCE OF GAS SENSORS BASED ON ZINC STANNATE NANOSTRUCTURES Aarthy Sivapunniyam 1

2. 2 LPG Detection Lowest Explosion limit : 20000 ppm Introduction Ammonia Maximum exposure limit : 300 ppm Prototype of LPG sensor developed at COEN

3. Center of Excellence in Nanotechnology @ AIT Objective 3  To design and fabricate highly sensitive gas sensor - detection of low concentration of toxic gases - LPG and ammonia

4. Center of Excellence in Nanotechnology @ AIT 5 micron Total sensing area: 2.5×10 -11 m 2 ZnO Nanorods ZnO thin film Total sensing area: 1.202 × 10 -8 m 2 Area increased 480 times 5 micron 500 nm 30 nm Nanosensors for gas sensing

5. Time Resistance Gas Leak Sensor Alert Nano Sensor Working principle T = 250°C

6. Center of Excellence in Nanotechnology @ AIT 6 Zinc nitrate and HMT at 90 o C Seeded glass substrate Zinc stannate based nanorods Tin chloride and sodium hydroxide ZnSnO 3 based sensor on glass substrate Sensor

7. Center of Excellence in Nanotechnology @ AIT 7 1μm Characterisation of nanostructures Length : 4μm Avg.dia~250nm 1μm 10μm  ZnSnO 3 microcubes : 1-8μm 5μm  ZnO nanorods  ZnSnO 3 microcubes

8. Center of Excellence in Nanotechnology @ AIT Characterization of gas sensor Test gas Air Control valve Computer Electrometer Temp Controller Spent gas exhaust Thermocouple Heater GPIB Probes Pressure regulator Gas sensor test chamber 8 Sensitivity, Selectivity and Stability Sensitivity (%) = [(R a - R g ) / R a ] ×100

9. Center of Excellence in Nanotechnology @ AIT 9 T = 250°C S = 34% 2250 ppm S = 35% 2400 ppm S = 44% 2700 ppm S = 63% 3000 ppm Time(s) Resistance (MΩ) T = 250°C 3000 ppm 1000 ppm 5000 ppm 7000 ppm 9000 ppm  Sensor response to varying LPG concentration  ZnO nanorods based sensor  ZnSnO 3 microcubes based sensor Sensor typeMax S (%) acheived ZnSnO 3 63 % (3000 ppm) ZnO58 % (9000 ppm)

10. Center of Excellence in Nanotechnology @ AIT 10 Sensitivity (%) Concentration of ammonia (ppm) 250°C 200°C 300°C  Sensor response to varying ammonia concentration  S= 86 % for 9000 ppm ammonia @ 250°C

11. Center of Excellence in Nanotechnology @ AIT 11 T = 250°C 2250 ppm Time(s) Resistance (MΩ) 2400 ppm 2700 ppm 3000 ppm 2250 ppm 2400 ppm 2700 ppm 3000 ppm 2250 ppm 2400 ppm 2700 ppm  Repeatability test for varying LPG concentration

12. Center of Excellence in Nanotechnology @ AIT 12  ZnO nanorods based sensor on alumina substrate  Length 3μm 6mm 3mm 1.5mm 6mm  Nickel plated electrodes  Bare alumina substrate  Avg diameter 100nm  ZnO nanorods

13. Center of Excellence in Nanotechnology @ AIT 13 Resistance (MΩ) Time(s) T = 250°C S= 36% 10000 ppm S= 31% 8900 ppm S= 25.5% 6700 ppm S= 14.3% 4500 ppm S= 11.2% 3000 ppm Resistance (MΩ) Time(s) T = 250°C S = 63% 9300 ppm S = 66% 10000 ppm S = 57% 7500 ppm S = 54% 5600 ppm S = 48% 3700 ppm S = 35% 2250 ppm  Sensor response to varying LPG concentration  Sensor response to varying ammonia concentration ZnO NR Sensor on alumina Max S (%) acheived LPG36 for 10000 ppm Ammonia63 for 9300 ppm

14. Center of Excellence in Nanotechnology @ AIT 14 Conclusions  Maximum sensitivity - 63% for 3000 ppm LPG and 86% for 9300 ppm ammonia at 250°C for zinc stannate based sensor  Improvement of sensitivity compared to ZnO nanorods based sensor (58% for 9000 ppm LPG at 250°C)

15. Center of Excellence in Nanotechnology @ AIT 15 Acknowledgements  Prof. Joydeep Dutta – For supporting me in all my research pursuits and generous allocation of his time  Prof. Gabor.L.Hornyak – For his invaluable support and wisdom he invested in my education  Dr. Chanchana Thanachayanont- For her continuous support and encouragement  All members of COEN at AIT

16. Center of Excellence in Nanotechnology @ AIT 16