Titania Sensors

SEM image of porous TiO2 layer after sensing at 500 °C prepared by drop-coating the FSP-made particles onto an alumina substrate interdigitated with gold electrodes.

Change in resistance of a FSP-made TiO2 sensor under exposure to isoprene during a forward and backward cycle in a dry O2/N2 atmosphere at 500 °C.

A. TELEKI, A. TRICOLI, AND S. E. PRATSINIS

Chemical gas sensors are used in a large variety of applications spanning from security and industrial safety to consumer products. Binary n-type semiconductor oxides such as tin oxide (SnO2), indium oxide (In2O3) or zinc oxide (ZnO) have been extensively investigated as gas-sensing materials since the 1950’s. These metal oxide sensors detect small amounts of a gaseous species present in air from a change in electrical resistance. Titanium dioxide (TiO2) in particular is ideal for environmental monitoring, as its sensor response is insensitive to ambient humidity in contrast to SnO2.

TiO2 nanoparticles were made by flame spray pyrolysis and the gas-sensing properties were tested by DC electrical measurements. A high sensitivity of the flame made TiO2 nanoparticles towards low concentrations of volatile organic compounds was shown. For example, the sensor resistance decreases under pulses of isoprene at low concentrations in a dry N2/O2 atmosphere. This behavior is typical for anatase titania as an n-type semiconductor. The response time was within a few seconds during the backward and forward cycle. The high stability and sensitivity of flame-made TiO2 nanoparticles demonstrated show the high potential for their use as gas sensing material.

Recent, relevant references:

• Sahm, T., L. Madler, A. Gurlo, N. Barsan, S. E. Pratsinis, and U. Weimar, "Flame spray synthesis of tin dioxide nanoparticles for gas sensing," Sens. Actuators, B, Chem 98, 148 (2004).
• Madler, L., T. Sahm, A. Gurlo, J.-D. Grunwaldt, N. Barsan, U. Weimar, and S. E. Pratsinis, "Sensing low concentrations of CO using flame-spray-made Pt/SnO2 nanoparticles," J. Nanoparticle Res. in press (2006).
• Madler, L., A. Roessler, S. E. Pratsinis, T. Sahm, A. Gurlo, N. Barsan, and U. Weimar, "Direct formation of highly porous gas-sensing films by in-situ thermophoretic deposition of flame-made Pt/SnO2 nanoparticles," Sens. Actuators, B, Chem 114, 283 (2006)
• Teleki, A., S.E. Pratsinis, K. Kalyanasundaram, and P.I. Gouma, "Sensing of organic vapors by flame-made TiO2 nanoparticles," Sens. Actuators, B, Chem 119, 683 (2006).