Poster on Reactivity of Oxidising Radicals with Functionalised Surfaces for 27th International Symposium on Gas Kinetics and Related Phenomena 2024
Creators: name: Wolstenholme-Hogg, Amy
name: Iqbal, Naeem
name: Chechik, Victor
Publisher: name: Zenodo
Year: 2024
Subjects: radical
junctionless nanowire transistor
environmental monitoring
gas sensor
air quality monitoring
atmospheric radicals
atmospheric chemistry
air quality
air chemistry
electronic sensors
free radicals
air pollution

description: Abstract:

Atmospheric radicals hugely influence the chemical processes that determine atmospheric composition and thus their detection is critical for understanding our atmosphere. As a result, there is a need for the development of new radical detection methods which are low-cost, manufacturable and can be easily deployed. The overall aim of this project is to develop self-assembled monolayer (SAM) functionalised semiconductor sensors, which electrically detect short-lived atmospheric radicals in real time. SAMs have grown in interest for their potential applications in gas sensing, predominantly for the detection of volatile organic compounds (1). In this study, we have investigated the reactivity of oxidizing radicals with self-assembled monolayers (SAMs), focusing particularly on the lateral spreading (autoxidation) of radical reactions throughout the monolayer chains. This investigation will give an indication to the lifetime of the radical sensors and influence the organic molecule which will be selected to functionalise the semiconductor sensors.

Exposure of SAMs of model organic compounds, such as alkanes, alkenes, perfluoroalkanes and arenes, to He/O2/H2O plasma generated .OH has been investigated. The concentration of .OH has been modelled at increasing distances between the functionalised silica surface and the plasma jet, using a 1-D kinetics  model. The reactivity has been analysed by a series of characterisation techniques, such as contact angle analysis, NMR, and fluorescence spectroscopy. It was observed that the rate of degradation of various organic molecules upon exposure to .OH were similar, with an exception to perfluoroalkane monolayers which degraded at a relatively slower rate.

To further investigate the lateral spreading of radical reactions throughout the monolayers, a methodology has been developed using silica nanoparticles functionalized with mixed monolayers of organic chains and a chromophore. The degree of degradation of the neighbouring organic chains upon UV light activation is monitored by cleaving the molecules from the surface of the silica nanoparticles and quantified by NMR and GC-MS. Results show that the lateral spreading of radical reactions does occur due to observing a decrease in mass of the neighbouring organic chains. Depending on the functionality of the organic chain, different rates of degradation are observed. Mechanistic features of these processes with different types of surface-attached organic molecules will be discussed with the aid of kinetic modelling. The rates of autoxidation of various organic molecules within monolayer systems will provide valuable information for the longevity of SAMs, particularly when utilized for sensing purposes.

 

References

1.           Singh M, Kaur N, Comini E. The role of self-assembled monolayers in electronic devices. Journal of Materials Chemistry C. 2020;8(12):3938-55.
description: Amy Wolstenholme-Hogg presented this poster for the The 27th International Symposium on Gas Kinetics and Related Phenomena. The conference served as an open forum for the presentation and discussion of the latest experimental and theoretical research on a wide range of topics related to gas phase chemical kinetics

RADICAL represents a 'Fundamental Breakthrough in Detection of Atmospheric Free Radicals'.

Find out more on the RADICAL project website: radical-air.eu

The RADICAL project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 899282.