Polypyrrole Nanoribbon Based Nano Gas Sensors Sergio Hernandez, Nicha Chartuprayoon and Nosang V. Myung Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA 92521Abstract Introduction & Motivation Polypyrrole nanoribbon is an effective sensing material because of high sensitivity and good stability. The simplicity of processing polymers together with chemically tunable properties makes them ideal materials for electronic, optoelectronic and electromechanical devices. Conducting polymer (i.e. polypyrrole) nanoribbon based gas sensors were fabricated using Lithography Patterned Nanowire Electrodeposition (LPNE) which combines the advantages of top-down lithographic patterning and bottom-up electrodeposition to form high density nanostructures in pre-determined location. The synthesized polypyrrole nanoribbons were used as sensing/transducing materials to detect various analytes including water vapor, acetone, methanol, ethanol, isopropanol, MEK, and carbon dioxide. The change of resistance upon exposure to analytes was monitor by applying a constant voltage of 0.5 V. The preliminary results show that polypyrrole nanoribbons are highly sensitive to VOCs with greatest sensitivity toward methanol. In the future work, the sensing performance will be further improved by functionalizing them with other materials. Objectives Wafer Scale Fabrication of PPy Nanoribbons Gas Sensing Apparatus Electrical conductivity at Room Temperature Temperature Dependent Measurement Resistance = 5.64 MΩ Conductivity = 5.91 S/cm 410μm Summary Future Work Acknowledgements Reference Resistance and Sensitivity of Alcohol Group Resistance and Sensitivity of the Ketone Group Lithographically Patterned Nanowire Electrodeposition (LPNE) P-type Si wafer with 1000Å SiO 2 layer Deposition 100nm thickness of sacrificial layer (Ni) Spin coating of photoresist (PR) S1813 Electropolymerization of PPy Electrolyte: 0.5M Pyyrole + 0.2M LiClO 4 Eapplied = 0.7V vs. SCE with Pt counter electrode Exposure under UV light for 7 second Develop pattern in developer(AZ400Z)-water mixture solution Chemical etching with Ni Etchant TFB Electrochemical etching Electrolyte: 0.1M KCl + 24mM HCl Eapplied = 0.02V vs. SCE with Pt counter electrode Removal of Ni by 2% HNO 3 Removal of PR by acetone Integration of gold electrode by lift-off photolithography Thickness of chrome = 20 nm Thickness of gold = 180 nm E SiO 2 layer Ni The main objective is to analyze the sensing of analytes such as water vapor, acetone, methanol, ethanol, isopropanol, MEK, and carbon dioxide using polypyrrole nanoribbons as a sensing materials. Eventually we will try to improve the sensitivity by functionalizing the polypyrrole nanoribbons with other materials. I acknowledge my mentor and graduate student Dr. Myung and Nicha Chartuprayoon from the department of Chemical and Environmental Engineering, in the University of California, Riverside; and the Financial support from the BRITE program and the University of California, Riverside. 15 meV/K 60 meV/K In the future work, the sensing performance of the polypyrrole nanoribbons will be further improved by functionalizing them with other materials such as gold, palladium and platinum. Water vapor had a very high negative response. In the alcohol group methanol, ethanol, and isopropanol was tested; with methanol clearly having the highest response, and ethanol the lowest. In the ketone group MEK and Acetone was tested; MEK having the highest response. Comparing both groups it is clear that the alcohol group produced the higher response. Even ethanol had a larger response than MEK. Carbon Dioxide was also tested; however it seems to produce no response. 1. Skotheim, T. A.; Reynolds, J. R., Handbook of conducting polymers. 3rd ed.; CRC: Boca Raton, Fla., 2007; p 2 v. 2. Menke, E. J.; Thompson, M. A.; Xiang, C.; Yang, L. C.; Penner, R. M. Nature Materials 2006, 5, (11), Conducting polymers are new class of material with fascinating electron-transport behavior that provides them with many technical applications. The simplicity of processing polymers together with chemically tunable properties makes them especially useful in electronic, optoelectronic and electromechanical devices. One such area where the conducting polymers have shown great promise is in sensory applications. In an attempt to increase the sensitivity of sensing materials, research has focused in utilizing nanowires as their primary focus. In our research we are using polypyrrole nanoribbons as sensing materials, because they are highly sensitive and relatively stable. A variation of polypyrrole nanostructures fabrication techniques have been developed such as template synthesis and dip-pen lithography; however they require expensive equipment such as AFM, FIB and E-Beam Lithography. Additionally, the device assembling process is very extensive. On the other hand Lithographically Patterned Nanowire Electrodeposition (LPNE) technique has been demonstrated as cost- effective technique in fabrication of nanowires in pre-determined locations on substrates with precisely controlled height and width. Another notable characteristic of this technique is that it combines photholithography and electrodeposition approaches.