Dr Stephen David Worrall MRSC was appointed as a Lecturer in Chemistry, based in the Chemical Engineering and Applied Chemistry department of School of Engineering and Applied Science, in August 2019.
Prior to joining Aston University his research career had been based at the University of Manchester. Starting with an MChem in Chemistry under the supervision of Dr Andrew Horn in 2012 he then completed a PhD in Nanoscience in 2016 under the joint supervision of Professor Robert Dryfe and Dr Martin Attfield. This was followed by two post doctoral research positions. The first was in Atmospheric Chemistry, working for Professor Carl Percival and Professor Hugh Coe, as part of the APHH Beijing project. The second was in 2D material nanocomposites, working for Professor Sarah Haigh and Dr Steve Edmondson, as part of the DISCOVERER project.
His primary research interests are focused upon the interface between metal-organic frameworks (MOF) and electrochemistry.
1) In situ investigations of the mechanisms of electrochemical MOF coating formation.
2) Computationally guided synthesis of new MOFs via electrochemical techniques.
3) Electrochemical applications of MOFs; catalysis, charge storage and data storage.
He also has a supporting interest in developing coatings of two-dimensional materials; both for aerospace applications and for the synthesis of composite coatings with MOFs for electrochemical applications.
Additionally he has an ongoing collaboration focused upon the measurement and interpretation of solid state vapour pressure data towards improving the modelling of aerosols in the atmosphere.
Areas of Expertise (10)
Thin Films and Nanotechnology
Thin Film Deposition
University of Manchester: Ph.D., Nanoscience 2016
University of Manchester: M.Chem., Chemistry 2012
- Member of the Royal Society of Chemistry
Media Appearances (2)
Clean Air Zone: Birmingham reports drop in emissions
BBC News online
Dr Stephen Worrall a lecturer in chemistry at Aston University said the figures were encouraging, but a full-year cycle of data was required. "It's really positive news," he said. "We knew vehicle numbers in the city centre were looking positive anyway, but in the most polluting category they're dropping really steadily - it's the proportion that we needed, evidence on nitrous dioxide levels, so that's really good information from the council."
CAZ: Driver numbers within Birmingham zone drop by 6,000
BBC News online
Although the full impact will not be clear until 2022, Dr Stephen Worrall - an atmospheric chemist at the university - said before charging was introduced, the number of daily non-compliant vehicles driving within the zone was an average of 18,787, but this dropped to 11,850 for the remainder of June with the last reported daily average of 10,800 for August.
Chemical characterisation of benzene oxidation products under high- and low-NOx conditions using chemical ionisation mass spectrometryAtmospheric Chemistry and Physics
Michael Priestley, Thomas J Bannan, Michael Le Breton, Stephen D Worrall, Sungah Kang, Iida Pullinen, Sebastian Schmitt, Ralf Tillmann, Einhard Kleist, Defeng Zhao, Jürgen Wildt, Olga Garmash, Archit Mehra, Asan Bacak, Dudley E Shallcross, Astrid Kiendler-Scharr, Åsa M Hallquist, Mikael Ehn, Hugh Coe, Carl J Percival, Mattias Hallquist, Thomas F Mentel, Gordon McFiggans
Aromatic hydrocarbons are a class of volatile organic compounds associated with anthropogenic activity and make up a significant fraction of urban volatile organic compound (VOC) emissions that contribute to the formation of secondary organic aerosol (SOA). Benzene is one of the most abundant species emitted from vehicles, biomass burning and industry. An iodide time-of-flight chemical ionisation mass spectrometer (ToF-CIMS) and nitrate ToF-CIMS were deployed at the Jülich Plant Atmosphere Chamber as part of a series of experiments examining benzene oxidation by OH under high- and low-NOx conditions, where a range of organic oxidation products were detected. The nitrate scheme detects many oxidation products with high masses, ranging from intermediate volatile organic compounds (IVOCs) to extremely low volatile organic compounds (ELVOCs), including C12 dimers. In comparison, very few species with C≥6 and O≥8 were detected with the iodide scheme, which detected many more IVOCs and semi-volatile organic compounds (SVOCs) but very few ELVOCs and low volatile organic compounds (LVOCs). A total of 132 and 195 CHO and CHON oxidation products are detected by the iodide ToF-CIMS in the low- and high-NOx experiments respectively...
Effect of methacrylic acid and pendant vinyl groups on the mechanical properties of highly stretchable core–shell nanostructured films deposited from waterPolymer Chemistry
James Turton, Stephen Worrall, Muhamad S Musa, Amir H Milani, Yichao Yao, Peter Shaw, David Ring, Brian R Saunders
2021 With the continued drive to develop elastomers, improved methods are required to decrease the environmental impact of their preparation. Previously, such systems used Zn-based salts to form nanostructured ionomeric elastomers which had high modulus values, but only limited stretchability. Here, we investigate highly stretchable, additive-free, nanostructured films that are formed simply by casting aqueous core–shell nanoparticle dispersions and drying. The nanoparticles have a poly(n-butylacrylate) (PBA) core and the shell contains a crosslinked copolymer of BA, acrylonitrile (AN), methacrylic acid (MAA) and 1,4-butanediol diacrylate (BDDA). The nanostructured films are shown to be highly stretchable (up to 1300%) and their toughness increases linearly with MAA content. The latter is due to hydrogen-bonding between the –COOH groups and AN. The core–shell nanoparticles are subsequently functionalised using glycidyl methacrylate (GMA) and the films heated to provide additional covalent crosslinking. We show that the vinyl group content can be evaluated using Raman spectroscopy. The latter also enables the monitoring of nanoparticle functionalisation by the reaction with GMA. Radical coupling of the vinyl groups upon heating of the films is shown to increase both the modulus and toughness of the films. Our new nanostructured films provide an alternative, additive-free, environmentally friendly approach for the preparation of highly stretchable water-based elastomers.
Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO_x in BeijingAtmospheric Chemistry and Physics
Lisa K Whalley, Eloise J Slater, Robert Woodward-Massey, Chunxiang Ye, James D Lee, Freya Squires, James R Hopkins, Rachel E Dunmore, Marvin Shaw, Jacqueline F Hamilton, Alastair C Lewis, Archit Mehra, Stephen D Worrall, Asan Bacak, Thomas J Bannan, Hugh Coe, Carl J Percival, Bin Ouyang, Roderic L Jones, Leigh R Crilley, Louisa J Kramer, William J Bloss, Tuan Vu, Simone Kotthaus, Sue Grimmond, Yele Sun, Weiqi Xu, Siyao Yue, Lujie Ren, W Joe F Acton, C Nicholas Hewitt, Xinming Wang, Pingqing Fu, Dwayne E Heard
2021 Measurements of OH, HO2, complex RO2 (alkene-and aromatic-related RO2) and total RO2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2:8 × 107 molecule cm-3, HO2 peaking at 1 × 109 molecule cm-3 and the total RO2 concentration reaching 5:5×109 molecule cm-3. OH reactivity (k.OH/) peaked at 89 s-1 during the night, with a minimum during the afternoon of 22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbvh-1) under the very low NO conditions (< 0:5ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings...
Key Role of NO3 Radicals in the Production of Isoprene Nitrates and Nitrooxyorganosulfates in BeijingEnvironmental Science and Technology
Jacqueline F Hamilton, Daniel J Bryant, Peter M Edwards, Bin Ouyang, Thomas J Bannan, Archit Mehra, Alfred W Mayhew, James R Hopkins, Rachel E Dunmore, Freya A Squires, James D Lee, Mike J Newland, Stephen D Worrall, Asan Bacak, Hugh Coe, Carl Percival, Lisa K Whalley, Dwayne E Heard, Eloise J Slater, Roderic L Jones, Tianqu Cui, Jason D Surratt, Claire E Reeves, Graham P Mills, Sue Grimmond, Yele Sun, Weiqi Xu, Zongbo Shi, Andrew R Rickard
2021 The formation of isoprene nitrates (IsN) can lead to significant secondary organic aerosol (SOA) production and they can act as reservoirs of atmospheric nitrogen oxides. In this work, we estimate the rate of production of IsN from the reactions of isoprene with OH and NO3 radicals during the summertime in Beijing. While OH dominates the loss of isoprene during the day, NO3 plays an increasingly important role in the production of IsN from the early afternoon onwards. Unusually low NO concentrations during the afternoon resulted in NO3 mixing ratios of ca. 2 pptv at approximately 15:00, which we estimate to account for around a third of the total IsN production in the gas phase. Heterogeneous uptake of IsN produces nitrooxyorganosulfates (NOS). Two mono-nitrated NOS were correlated with particulate sulfate concentrations and appear to be formed from sequential NO3 and OH oxidation. Di- and tri-nitrated isoprene-related NOS, formed from multiple NO3 oxidation steps, peaked during the night. This work highlights that NO3 chemistry can play a key role in driving biogenic–anthropogenic interactive chemistry in Beijing with respect to the formation of IsN during both the day and night.
Low-NO atmospheric oxidation pathways in a polluted megacityAtmospheric Chemistry and Physics
Mike J Newland, Daniel J Bryant, Rachel E Dunmore, Thomas J Bannan, W Joe F Acton, Ben Langford, James R Hopkins, Freya A Squires, William Dixon, William S Drysdale, Peter D Ivatt, Mathew J Evans, Peter M Edwards, Lisa K Whalley, Dwayne E Heard, Eloise J Slater, Robert Woodward-Massey, Chunxiang Ye, Archit Mehra, Stephen D Worrall, Asan Bacak, Hugh Coe, Carl J Percival, C Nicholas Hewitt, James D Lee, Tianqu Cui, Jason D Surratt, Xinming Wang, Alastair C Lewis, Andrew R Rickard, Jacqueline F Hamilton
2021 The impact of emissions of volatile organic compounds (VOCs) to the atmosphere on the production of secondary pollutants, such as ozone and secondary organic aerosol (SOA), is mediated by the concentration of nitric oxide (NO). Polluted urban atmospheres are typically considered to be "high-NO"environments, while remote regions such as rainforests, with minimal anthropogenic influences, are considered to be "low NO". However, our observations from central Beijing show that this simplistic separation of regimes is flawed. Despite being in one of the largest megacities in the world, we observe formation of gas- and aerosol-phase oxidation products usually associated with low-NO "rainforest-like"atmospheric oxidation pathways during the afternoon, caused by extreme suppression of NO concentrations at this time. Box model calculations suggest that during the morning high-NO chemistry predominates (95 %) but in the afternoon low-NO chemistry plays a greater role (30 %). Current emissions inventories are applied in the GEOS-Chem model which shows that such models, when run at the regional scale, fail to accurately predict such an extreme diurnal cycle in the NO concentration. With increasing global emphasis on reducing air pollution, it is crucial for the modelling tools used to develop urban air quality policy to be able to accurately represent such extreme diurnal variations in NO to accurately predict the formation of pollutants such as SOA and ozone.