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Instruments / Technical Area	Publication Details	Published
I22-Small angle scattering & Diffraction	Exploring the nanostructures accessible to an organic surfactant atmospheric aerosol proxy Adam Milsom , Adam M. Squires , Isabel Quant , Nicholas J. Terrill , Steven Huband , Ben Woden , Edna Cabrera-Martinez , Christian Pfrang The Journal Of Physical Chemistry A 2 DOI: 10.1021/acs.jpca.2c04611 Diamond Proposal Number(s): [28020, 15121] Open Access Show Abstract ▼ Abstract: The composition of atmospheric aerosols varies with time, season, location, and environment. This affects key aerosol properties such as hygroscopicity and reactivity, influencing the aerosol’s impact on the climate and air quality. The organic fraction of atmospheric aerosol emissions often contains surfactant material, such as fatty acids. These molecules are known to form three-dimensional nanostructures in contact with water. Different nanostructures have marked differences in viscosity and diffusivity that are properties whose understanding is essential when considering an aerosol’s atmospheric impact. We have explored a range of nanostructures accessible to the organic surfactant oleic acid (commonly found in cooking emissions), simulating variation that is likely to happen in the atmosphere. This was achieved by changing the amount of water, aqueous phase salinity and by addition of other commonly coemitted compounds: sugars and stearic acid (the saturated analogue of oleic acid). The nanostructure was observed by both synchrotron and laboratory small/wide angle X-ray scattering (SAXS/WAXS) and found to be sensitive to the proxy composition. Additionally, the spacing between repeat units in these nanostructures was water content dependent (i.e., an increase from 41 to 54 Å in inverse hexagonal phase d-spacing when increasing the water content from 30 to 50 wt %), suggesting incorporation of water within the nanostructure. A significant decrease in mixture viscosity was also observed with increasing water content from ∼104 to ∼102 Pa s when increasing the water content from 30 to 60 wt %. Time-resolved SAXS experiments on levitated droplets of this proxy confirm the phase changes observed in bulk phase mixtures and demonstrate that coexistent nanostructures can form in droplets. Aerosol compositional and subsequent nanostructural changes could affect aerosol processes, leading to an impact on the climate and urban air pollution.	Sep 2022
I22-Small angle scattering & Diffraction	The evolution of surface structure during simulated atmospheric ageing of nano-scale coatings of an organic surfactant aerosol proxy Adam Milsom , Adam M. Squires , Maximilian W. A. Skoda , Philipp Gutfreund , Eleanore Mason , Nicholas J. Terrill , Christian Pfrang Environmental Science: Atmospheres DOI: 10.1039/D2EA00011C Diamond Proposal Number(s): [23096] Open Access Show Abstract ▼ Abstract: Atmospheric aerosol particles can be coated with organic material, impacting on aerosol atmospheric lifetime and urban air quality. Coatings of organic material are also found on indoor surfaces such as window glass. Oleic acid is a fatty acid surfactant which is abundant in cooking and marine aerosol emissions. Under ambient conditions it can self-assemble into lamellar bilayers (stacks) with its sodium salt. We found that nano-scale oleic acid-sodium oleate films spin-coated onto solid silicon substrates form a mixed-phase area of lamellar stacks and amorphous film. The coatings were subjected to simulated atmospheric ageing (ozonolysis and humidity changes) while the surface structure was followed by neutron reflectometry. We found that the orientation of lamellar stacks, which is known to affect the diffusivity of small molecules through them, was sensitive to humidity both in oxidised and pristine films. Lamellar bilayer stacks in oxidised films acquired ~11-fold more water in humid conditions (> 80 % relative humidity) compared to the unoxidised film, demonstrating a significant increase in film hygroscopicity after oxidation. Lamellar stacks, consisting only of starting materials, persisted at the end of simulated atmospheric ageing. These findings for atmospherically relevant nano-scale films corroborate previous work on micrometre-scale layers, thus demonstrating that fatty acid self-assembly could significantly increase the atmospheric lifetime of these molecules. The persistence of such semi-solid surfactant arrangements in the atmosphere has implications for the climate as well as urban and indoor air pollution.	May 2022
I22-Small angle scattering & Diffraction	The impact of molecular self-organisation on the atmospheric fate of a cooking aerosol proxy Adam Milsom , Adam Squires , Andrew D. Ward , Christian Pfrang Atmospheric Chemistry And Physics 22, 4895 - 4907 DOI: 10.5194/acp-22-4895-2022 Diamond Proposal Number(s): [21663] Open Access Show Abstract ▼ Abstract: Atmospheric aerosols influence the climate via cloud droplet nucleation and can facilitate the long range transport of harmful pollutants. The lifetime of such aerosols can therefore determine their environmental impact. Fatty acids are found in organic aerosol emissions with oleic acid, an unsaturated fatty acid, being a large contributor to cooking emissions. As a surfactant, oleic acid can self-organise into nanostructured lamellar bilayers with its sodium salt, and this self-organisation can influence reaction kinetics. We developed a kinetic multi-layer model-based description of decay data we obtained from laboratory experiments of the ozonolysis of coated films of this self-organised system, demonstrating a decreased diffusivity for both oleic acid and ozone due to lamellar bilayer formation. Diffusivity was further inhibited by a viscous oligomer product forming in the surface layers of the film. Our results indicate that nanostructure formation can increase the reactive half-life of oleic acid by an order of days at typical indoor and outdoor atmospheric ozone concentrations. We are now able to place nanostructure formation in an atmospherically meaningful and quantifiable context. These results have implications for the transport of harmful pollutants and the climate.	Apr 2022
I22-Small angle scattering & Diffraction	An organic crystalline state in ageing atmospheric aerosol proxies: spatially resolved structural changes in levitated fatty acid particles Adam Milsom , Adam M. Squires , Jacob A. Boswell , Nicholas J. Terrill , Andrew D. Ward , Christian Pfrang Atmospheric Chemistry And Physics 21, 15003 - 15021 DOI: 10.5194/acp-21-15003-2021 Diamond Proposal Number(s): [20541, 21663] Open Access Show Abstract ▼ Abstract: Organic aerosols are key components of the Earth's atmospheric system. The phase state of organic aerosols is known to be a significant factor in determining aerosol reactivity, water uptake and atmospheric lifetime – with wide implications for cloud formation, climate, air quality and human health. Unsaturated fatty acids contribute to urban cooking emissions and sea spray aerosols. These compounds, exemplified by oleic acid and its sodium salt, are surface-active and have been shown to self-assemble into a variety of liquid-crystalline phases upon addition of water. Here we observe a crystalline acid–soap complex in acoustically levitated oleic acid–sodium oleate particles. We developed a synchrotron-based simultaneous small-angle and wide-angle X-ray scattering (SAXS and WAXS)–Raman microscopy system to probe physical and chemical changes in the proxy during exposure to humidity and the atmospheric oxidant ozone. We present a spatially resolved structural picture of a levitated particle during humidification, revealing a phase gradient consisting of a disordered liquid crystalline shell and crystalline core. Ozonolysis is significantly slower in the crystalline phase compared with the liquid phase, and a significant portion (34 ± 8 %) of unreacted material remains after extensive oxidation. We present experimental evidence of inert surface layer formation during ozonolysis, taking advantage of spatially resolved simultaneous SAXS–WAXS experiments. These observations suggest that atmospheric lifetimes of surface-active organic species in aerosols are highly phase-dependent, potentially impacting climate, urban air quality and long-range transport of pollutants such as polycyclic aromatic hydrocarbons (PAHs).	Oct 2021
I22-Small angle scattering & Diffraction	The hygroscopicity and reactivity of fatty acid atmospheric aerosol proxies are affected by nanostructure Adam Milsom , Adam Squires , Nicholas Terrill , Andrew Ward , Christian Pfrang EGU General Assembly 2021 DOI: 10.5194/egusphere-egu21-7326 Open Access Show Abstract ▼ Abstract: Atmospheric aerosol hygroscopicity and reactivity play a significant role in determining aerosol fate, and are affected by composition and other physical properties. Organic aerosol emissions contain fatty acids, along with sugars such as fructose. As surfactants, fatty acids organise into a range of nanostructures (3-D molecular arrangements), dependent on water content and mixture composition. In this study, we were able to demonstrate (and quantify) that the chemical reactivity of this proxy is dependent on its 3-D molecular arrangement. Furthermore, we have determined the effect of each observed nanostructure on hygroscopicity by measuring the swelling of these nanostructures as a function of relative humidity. We did this by coating capillaries with a fatty acid/sugar as a mixture for an urban aerosol, and following structural changes with simultaneous Small-Angle X-ray Scattering (SAXS) and Raman microscopy, at a synchrotron X-ray source. SAXS measured the nano-structural parameters required to follow both the reaction kinetics (ozonolysis) and hygroscopic swelling of each nanostructure. Raman microscopy provided complementary kinetic information and supported these findings. We found that the molecular arrangement of surfactant material has an impact on both the chemical kinetics and hygroscopicity. This has implications for the persistence of particulate matter in the urban environment and surfactant material in the atmosphere.	Mar 2021
I22-Small angle scattering & Diffraction	The persistence of a proxy for cooking emissions in megacities: a kinetic study of the ozonolysis of self-assembled films by simultaneous Small & Wide Angle X-ray Scattering (SAXS/WAXS) and Raman microscopy Adam Milsom , Adam M. Squires , Ben Woden , Nicholas J. Terrill , Andrew D. Ward , Christian Pfrang Faraday Discussions DOI: 10.1039/D0FD00088D Diamond Proposal Number(s): [21663, 23096] Open Access Show Abstract ▼ Abstract: Cooking emissions account for a significant proportion of the organic aerosol emitted into the urban environment and high pollution events have been linked to an increased organic content on urban particulate matter surfaces. We present a kinetic study on surface coatings of self-assembled (semi-solid) oleic acid-sodium oleate cooking aerosol proxies undergoing ozonolysis. We found a clear film thickness-dependent kinetic behaviour and measured the effect of the organic phase on the kinetics for this system. In addition to the thickness-dependent kinetics, we show that significant fractions of unreacted proxy remain at the end of extensive ozone exposure and that this effect scales approximately linearly with film thickness, suggesting that a late-stage inert reaction product may form to inhibit reaction progress – effectively building up an inert crust. We determine this by using a range of simultaneous analytical techniques; most notably Small-Angle X-ray Scattering (SAXS) has been used for the first time to measure reaction kinetics of films of a wide range of thicknesses from ca. 0.59 to 73 µm with films < 10 µm thick being of potential atmospheric relevance. These observations have implications for the evolution of particulate matter in the urban environment, potentially extending the atmospheric lifetimes of harmful aerosol components and affecting the local urban air quality and climate.	Sep 2020
E02-JEM ARM 300CF I22-Small angle scattering & Diffraction	3D nanostructured palladium with single diamond architecture for enhanced catalytic activity Matthew Burton , Anand Selvam , Jake Lawrie-Ashton , Adam M. Squires , Nicholas Terrill , Iris Nandhakumar Acs Applied Materials & Interfaces DOI: 10.1021/acsami.8b13230 Diamond Proposal Number(s): [14925, 10330, 16964] Show Abstract ▼ Abstract: Fuel cells are a key new green technology that have applications in both transport and portable power generation. Carbon supported platinum (Pt) is used as an anode and cathode electrocatalyst in low-temperature fuel cells fuelled with hydrogen or low molecular weight alcohols. The cost of Pt and the limited world supply are significant barriers to the widespread use of these types of fuel cells. Compara-tively palladium has a three times higher abundance in the Earth’s crust. Here a facile, low temperature and scalable synthetic route to-wards 3D nanostructured palladium (Pd) employing electrochemical templating from inverse lyotropic lipid phases is presented. The obtained single diamond morphology Pd nanostructures exhibited excellent catalytic activity and stability towards methanol, ethanol and glycerol oxidation compared to commercial Pd black and the nanostructure was verified by small-angle X-ray scattering (SAXS), scanning tunneling electron microscopy (STEM) as well as by cyclic voltammetry (CV).	Oct 2018
B21-High Throughput SAXS	Complex three-dimensional self-assembly in proxies for atmospheric aerosols C. Pfrang , K. Rastogi , Edna Cabrera-Martinez , A. M. Seddon , C. Dicko , A. Labrador , T. S. Plivelic , N. Cowieson , A. M. Squires Nature Communications 8 DOI: 10.1038/s41467-017-01918-1 Diamond Proposal Number(s): [16578] Open Access Show Abstract ▼ Abstract: Aerosols are significant to the Earth’s climate, with nearly all atmospheric aerosols containing organic compounds that often contain both hydrophilic and hydrophobic parts. However, the nature of how these compounds are arranged within an aerosol droplet remains unknown. Here we demonstrate that fatty acids in proxies for atmospheric aerosols self-assemble into highly ordered three-dimensional nanostructures that may have implications for environmentally important processes. Acoustically trapped droplets of oleic acid/sodium oleate mixtures in sodium chloride solution are analysed by simultaneous synchrotron small-angle X-ray scattering and Raman spectroscopy in a controlled gas-phase environment. We demonstrate that the droplets contained crystal-like lyotropic phases including hexagonal and cubic close-packed arrangements of spherical and cylindrical micelles, and stacks of bilayers, whose structures responded to atmospherically relevant humidity changes and chemical reactions. Further experiments show that self-assembly reduces the rate of the reaction of the fatty acid with ozone, and that lyotropic-phase formation also occurs in more complex mixtures more closely resembling compositions of atmospheric aerosols. We suggest that lyotropic-phase formation likely occurs in the atmosphere, with potential implications for radiative forcing, residence times and other aerosol characteristics.	Nov 2017
I22-Small angle scattering & Diffraction	3D semiconducting nanostructures via inverse lipid cubic phases M. R. Burton , C. Lei , P. A. Staniec , N. J. Terrill , A. M. Squires , N. M. White , Iris S. Nandhakumar Scientific Reports 7 DOI: 10.1038/s41598-017-06895-5 Diamond Proposal Number(s): [14925, 10330] Open Access Show Abstract ▼ Abstract: Well-ordered and highly interconnected 3D semiconducting nanostructures of bismuth sulphide were prepared from inverse cubic lipid mesophases. This route offers significant advantages in terms of mild conditions, ease of use and electrode architecture over other routes to nanomaterials synthesis for device applications. The resulting 3D bicontinous nanowire network films exhibited a single diamond topology of symmetry Fd3m (Q227) which was verified by Small angle X-ray scattering (SAXS) and Transmission electron microscopy (TEM) and holds great promise for potential applications in optoelectronics, photovoltaics and thermoelectrics.	Jul 2017
I07-Surface & interface diffraction	Watching mesoporous metal films grow during templated electrodeposition with in situ SAXS Samuel J. Richardson , Matthew R. Burton , Xiatong Luo , Paul A. Staniec , Iris S. Nandhakumar , Nick J. Terrill , Joanne M. Elliott , Adam M. Squires Nanoscale DOI: 10.1039/C7NR03321D Diamond Proposal Number(s): [10330] Show Abstract ▼ Abstract: In this paper, we monitor real-time growth of mesoporous platinum during electrodeposition using small-angle X-ray scattering (SAXS). Previously we have demonstrated that platinum films featuring ‘single diamond’ (Fd3m) morphology can be produced from ‘double diamond’ (Pn3m) lipid cubic phase templates; the difference in symmetry provides additional scattering signals unique to the metal. Taking advantage of this, we present simultaneous in situ SAXS / electrochemical measurement as the platinum nanostructures grow within the lipid template. This measurement allows us to correlate the nanostructure appearance with the deposition current density and to monitor the evolution of orientational and lateral ordering of the lipid and platinum during deposition and after template removal. In other periodic metal nanomaterials deposited within any of the normal topology liquid crystal, mesoporous silica or block copolymer templates previously published, the template and emerging metal have the same symmetry, so such a study has not previously been possible.	Jun 2017

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