Porphyrin molecules are often used for sensor engineering to improve sensitivity and selectivity to specific analytes. It is important to understand how the porphyrin HOMO-LUMO levels deplete surface states during functionalization of solid state sensors. Additionally, the effect of functionalization on the analyte sensing mechanism is significant to overall gas sensor design. We have previously studied the impact of the hemin porphyrin on the sensitivity of an InAs device with respect to NO and NO2 gases. We are currently exploring methods to optimize functionalization with porphyrins to enhance NOx detection. Our preliminary results from x-ray photoelectron spectroscopy of porphyrinated surfaces show changes in the InAs valence band maximum that indicate electron transfer at the interface. Furthermore, the samples’ responses to controlled gases are evaluated by monitoring real-time van der Pauw resistivity data.
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