ANYL 295 |
| We describe the use of gold and palladium monolayer-protected cluster (MPC) films for chemiresistive vapor and hydrogen sensing, respectively. These MPCs are comprised of a 1-5 nm diameter metallic core surrounded by a monolayer of organomercaptan molecules, usually alkanethiolates. Our work on gold MPCs involves fundamental studies on the effect of reducing the size of the films to the microscale/nanoscale on the sensor characteristics for volatile organic compounds, using toluene and isopropanol as model vapors. Reduction of size leads to reduced stability, irreversibility, and lower signal-to-noise. A simple dithiol cross-linking procedure imparts stability and reversibility into microscale films and gentle heating improves signal-to-noise. Also, as dithiol cross-linking increases, the response to vapors decreases due to reduced film flexibility. Drop-cast films of Pd MPCs are easy to construct and are useful for hydrogen sensing down to technologically relevant concentrations (0.1%) following an ozone activation process. Heat treatment also leads to increased hydrogen sensitivity, but the sensing mechanism and sensitivity is different from ozone and depends on the temperature. This talk will focus on the optimal conditions and the sensing mechanism for chemiresistive vapor sensing with microscale/nanoscale films of gold MPCs and hydrogen sensing with palladium MPCs. |
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Analytical Approaches: Sensors
8:30 AM-11:50 AM, Thursday, 14 September 2006 Moscone Center -- Room 123, Oral
Division of Analytical Chemistry |