The air inside the cabin of civilian and military aircraft can be contaminated with harmful volatile organic compounds (VOCs) from engine bleeding air. As such, there is a demand for reliable, sensitive and highly selective sensors to monitor the range of possible VOCs that may contaminate air quality during the flight. Currently employed chemical sensors are bulky, expensive, and usually lack specificity to handle more complex chemical environments. As an alternative, sensors using bio-recognition elements (BREs), usually consisting of peptides or nucleic acids, tend to show marked improvement in sensitivity and selectivity given the high specificity that can be found in biomolecules.  For example, our team is developing carbon nanotube (CNT) chemiresistors functionalized with peptide-based BREs as miniaturized VOC sensors, where the BRE’s affinity to various VOCs and its binding to the CNT are anticipated to govern sensor outputs. Therefore, it is crucial to better evaluate the biotic/abiotic interface at the sensor surface to help better understand how this interface influences sensor properties.<br/>In this presentation, we examine the biotic/abiotic interface for five VOC-binding using near edge X-ray absorption fine structure spectroscopy (NEXAFS).  Using N K-edge measurements, the conformation and orientation of the BREs were evaluated at graphene and Si surfaces, where their respective orientations were determined using the peptide conformation model (PCM). Experiments were performed on bare substrates and on those exposed to acetone and IPA, two models VOCs found in engine bleed air. We have found that both the initial sequence of the BRE influences morphology and alignment at the biotic/abiotic interface, which is future perturbed under exposure to VOCs. These experiments are useful to help understand how VOCs modulate the biotic/abiotic interface that is ultimately responsible for VOC sensing. Overall, those findings can help to develop more accurate and feasible sensitive BRE-based VOC sensors.

Probing morphology and orientation of VOC binding peptides at biotic/abiotic surfaces using near-edge X-ray absorption fine-structure spectroscopy

ACS Spring 2022

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