NOISES - Nitrous Oxide In-Situ Environmental Sensors

Nitrous oxide (N2O) is a critical greenhouse gas and a potent ozone-depleting agent. Knowing its environmental occurrence and fate is critical for climate change science but there is currently no chemical strategy to measure nitrous oxide in the oceans. This project aims to solve this problem by creating a custom-designed molecule that undergoes a chemical reaction with nitrous oxide, resulting in a detectable colour change. This process will then be adapted to work in complex environmental samples such as seawater. The process will be incorporated into a prototype mini-analyser device that is able to detect the colour change, and hence determine the level of nitrous oxide dissolved in the sample. When deployed such devices could make many measurements of even low levels of nitrous oxide, filling the gaps in our measurements (and therefore understanding) of nitrous oxide in the marine environment. This will be the first development step towards a sensor which can potentially be deployed in the sea or on unmanned robots, to measure nitrous oxide in areas such as the deep sea, or polar oceans, which are hazardous and/or hard to access to scientists. In the longer term, by combining custom chemical synthesis with ocean technology design and engineering, this project will establish a pipeline of new chemistry solutions to solve other critical problems relating to measurement of chemicals in the sea using sensors. The use of sensors on robots, moorings, floats and drifters, also enables measurements with a much lower energy use and hence carbon footprint than the traditional collection of water samples (e.g. with a research ship, or person in the field) and later laboratory analysis. Therefore, the development of sensors is essential for marine science to reach the UK's goal of Net Zero whilst maintaining or extending its capability.

Widespread in-situ measurement of nitrous oxide (N2O) is critical for reducing uncertainty in oceanographic process studies, radiative gas flux estimates and therefore for our understanding of climate change and its drivers. For example these measurements are critical for estimation and understanding of ocean N2O sinks in polar regions. N2O is also important in agricultural and industrial processes and impacts, and the availability of a low-cost sensor would have wide impacts. Without in situ sensors for dissolved N2O, we are currently reliant on collection and lab analysis of water samples. This reduces the amount of data in both space and time as well as risking quality through sample degradation between acquisition and analysis. Sampling is also energy/carbon intensive (requiring ships and personnel): a block to the UK's commitment to Net Zero. In contrast, using sensors remotely deployed can reduce associated emissions by a factor of ~1000 (see UKRI's Net Zero Oceanographic Capability report). This project will design and synthesise novel chemodosimeter molecules that can react rapidly (and selectively) with N2O, despite the notorious lack of reactivity of this particular analyte. These will incorporate reporter motifs whose absorption spectra are modulated upon reaction with N2O, leading to changes in the visible region. These will be formulated into a colorimetric assay suitable for use with the National Oceanographic Centre's 'lab-on-chip' (LoC) device, to enable measurement of environmental samples with complex seawater matrices. Co-development of these molecules between the two collaborating institutions allows scope for them to be tailored to the specification of the LoC technology and vice versa, so allowing improvement of limit of detection and selectivity over interferences. A proof of concept prototype will be created to demonstrate applicability of the assay to the LoC platform and develop specifications for a potential future in-situ LoC N2O sensor.