• The past, present and future of indoor air chemistry

      Bekö, Gabriel; Carslaw, Nicola; Fauser, Patrick; Kauneliene, Violeta; Nehr, Sascha; Phillips, Gavin; Saraga, Dikaia; Schoemaecker, Coralie; Wierzbicka, Aneta; Querol, Xavier; et al. (Wiley, 2020-04-25)
      This is an editorial contribution to the Journal Indoor Air on the future direction of indoor air chemistry research.
    • Additively Manufactured Graphitic Electrochemical Sensing Platforms

      Foster, Christopher W; El Bardisy, Hadil M; Down, Michael P; Keefe, Edmund M; Smith, Graham C; Banks, Craig E; Manchester Metropolitan University (Foster, El Bardisy, Down, Keefe, Banks), University of Chester (Smith) (Elsevier, 2020-02-01)
      Additive manufacturing (AM)/3D printing technology provides a novel platform for the rapid prototyping of low cost 3D platforms. Herein, we report for the first time, the fabrication, characterisation (physicochemical and electrochemical) and application (electrochemical sensing) of bespoke nanographite (NG)-loaded (25 wt. %) AM printable (via fused deposition modelling) NG/PLA filaments. We have optimised and tailored a variety of NG-loaded filaments and their AM counterparts in order to achieve optimal printability and electrochemical behaviour. Two AM platforms, namely AM macroelectrodes (AMEs) and AM 3D honeycomb (macroporous) structures are benchmarked against a range of redox probes and the simultaneous detection of lead (II) and cadmium (II). This proof-of-concept demonstrates the impact that AM can have within the area of electroanalytical sensors.
    • A single parameter approach to enhance the microstructural and mechanical properties of beta Ti-Nb alloy via open-air fiber laser nitriding

      Chan, Chi-Wai; Chang, Xianwen; Bozorgzadeh, Mohammad Amin; Smith, Graham C; Lee, Seunghwan; Queen's University Belfast, Technical University of Denmark, University of Chester (Elsevier, 2019-12-13)
      In this study, the idea of applying open-air laser nitriding to improve the microstructural and mechanical properties of beta Ti-45 at.% Nb alloy was demonstrated. Surface cracking after laser nitriding is one of the main reasons impeding direct translation of the laser nitriding technique from the laboratories to industries as cracks can be the weak points to initiate mechanical and corrosion failures in long-term usage. With proper selection of duty cycle (DC) between 40% (modulated mode) and 100% (continuous wave, CW mode) to control the laser energy input and laser-material-gas interaction time, the cracking problems of laser nitriding can be alleviated and even solved. A crack-free and uniformly gold-coloured nitrided surface was successfully obtained at the DC of 40% in this study. The morphology, microstructure, composition and mechanical properties of the nitrided samples were studied and analysed by optical microscopy (OM), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Vickers micro-hardness tests. The OM results indicated that minimum overlapping between the laser tracks would give desirable results to obtain the crack-free surface. The measurements from the SEM micrographs indicated the depth of the laser-nitrided areas ranged between 22 and 43 µm. The XRD findings showed that a clear conversion of the TiNb surface to a nitride as a result of laser nitriding was observed. The maximum hardness, as measured by the Vickers method in cross-sections, lay in the range of 780 to 870 HV after laser nitriding. To summarise, control of DC to obtain a crack free and quality surface via fiber laser nitriding in open air is a simpler and quicker approach in comparison with the conventional substrate preheating and nitrogen (N) dilution approaches. The single-parameter approach is more efficient than parameter optimisation via design of experiments (DOE) employed in conventional methods.
    • Self-assembled nanostructures in ionic liquids facilitate charge storage at electrified interfaces

      Mao, Xianwen; Brown, Paul; Cervinka, Citrad; Hazell, Gavin; Li, Hua; Ren, Yinying; Chen, Di; Atkin, Rob; Eastoe, Julian; Grillo, Isabelle; et al. (Springer Nature, 2019-08-12)
      Driven by the potential applications of ionic liquids (ILs) in many emerging electrochemical technologies, recent research efforts have been directed at understanding the complex ion ordering in these systems, to uncover novel energy storage mechanisms at IL–electrode interfaces. Here, we discover that surface-active ILs (SAILs), which contain amphiphilic structures inducing self-assembly, exhibit enhanced charge storage performance at electrified surfaces. Unlike conventional non amphiphilic ILs, for which ion distribution is dominated by Coulombic interactions, SAILs exhibit significant and competing van der Waals interactions owing to the non-polar surfactant tails, leading to unusual interfacial ion distributions. We reveal that, at an intermediate degree of electrode polarization, SAILs display optimum performance, because the low-charge-density alkyl tails are effectively excluded from the electrode surfaces, whereas the formation of non-polar domains along the surface suppresses undesired overscreening effects. This work represents a crucial step towards understanding the unique interfacial behaviour and electrochemical properties of amphiphilic liquid systems showing long-range ordering, and offers insights into the design principles for high-energy-density electrolytes based on spontaneous self-assembly behaviour.
    • Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential

      Halevesa, Eleftherios; Mavroidi, Barbara; Moschona, Alexandra; Hadjispyrou, Spyros; Salifoglou, Athanasios; Pelecanou, Maria; Litsardakis, George; Pantazaki, Anastasia; Swanson, Claudia H.; Smith, Graham C.; et al. (Elsevier, 2019-07-15)
      In this work novel magnetic cationic liposomal nanoformulations were synthesized for the encapsulation of a crystallographically defined ternary V(IV)-curcumin-bipyridine (VCur) complex with proven bioactivity, as potential anticancer agents. The liposomal vesicles were produced via the thin film hydration method employing N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP) and egg phosphatidylcholine lipids and were magnetized through the addition of citric acid surface-modified monodispersed magnetite colloidal magnetic nanoparticles. The obtained nanoformulations were evaluated for their structural and textural properties and shown to have exceptional stability and enhanced solubility in physiological media, demonstrated by the entrapment efficiency and loading capacity results and the in vitro release studies of their cargo. Furthermore, the generated liposomal formulations preserved the superparamagnetic behavior of the employed magnetic core maintaining the physicochemical and morphological requirements for targeted drug delivery applications. The novel nanomaterials were further biologically evaluated for their DNA interaction potential and were found to act as intercalators. The findings suggest that the positively charged magnetic liposomal nanoformulations can generate increased concentration of their cargo at the DNA site, offering a further dimension in the importance of cationic liposomes as nanocarriers of hydrophobic anticancer metal ion complexes for the development of new multifunctional pharmaceutical nanomaterials with enhanced bioavailability and targeted antitumor activity.
    • The effect of irradiation impinging on disparate anchoring configurations of polar-organic molecules adsorbed on bulk and thin-film metal surfaces

      Papadopoulos, Theodoros A.; Metz, Sebastian; Tang, Shu-Jung; University of Chester; Daresbury Laboratory; National Tsing-Hua University (Elsevier, 2019-07-11)
      The behavior of polar metal organic molecules, chloroaluminum phthalocyanine (ClAlPc), upon ultraviolet (UV) irradiation was investigated to evaluate the stability of the adsorption process on the Ag(111) thin film and bulk crystal. Angle-resolved photoelectron spectroscopy (ARPES) was mainly employed to measure the molecular energy states (MES) and vacuum level (VL) shift for 1-ML ClAlPc in the Cl-down configuration. A consistent trend was observed showing that ClAlPc in the Cl-down configuration is energetically more stable on the Ag thin-film surface than on the corresponding surface of the Ag bulk crystal. The intermediate adsorption state in tilted configuration during the irradiation impinging is identified by large positive VL shifts and broad spectra line shapes to infer a flipping mechanism from Cl-down to Cl-up configuration. Strain on the Ag thin films from the underlying mismatched Ge(111) substrate is considered to cause enlarged hollow sites on the Ag(111) thin-films, that anchor the Cl-down configuration more tightly on the thin-film surfaces, as confirmed by density functional theory (DFT) calculations.
    • Studies of black diamond as an antibacterial surface for gram negative bacteria: the interplay between chemical and mechanical bactericidal activity

      Dunseath, Olivia; Smith, E. J. W.; Al-Jeda, T.; Smith, J. A.; King, Sophie; May, Paul W.; Nobbs, Angela H.; Hazell, Gavin; Welch, Colin C.; Su, Bo; et al. (Nature, 2019-06-19)
      ‘Black silicon’ (bSi) samples with surfaces covered in nanoneedles of length ~5 μm were fabricated using a plasma etching process and then coated with a conformal uniform layer of diamond using hot filament chemical vapour deposition to produce ‘black diamond’ (bD) nanostructures. The diamond needles were then chemically terminated with H, O, NH2 or F using plasma treatment, and the hydrophilicity of the resulting surfaces were assessed using water droplet contact-angle measurements, and scaled in the order O > H ≈NH2 >F, with the F-terminated surface being superhydrophobic. The effectiveness of these differently terminated bD needles in killing the Gram-negative bacterium E. coli was semiquantified by Live/Dead staining and fluorescence microscopy, and visualised by environmental scanning electron microscopy. The total number of adhered bacteria was consistent for all the nanostructured bD surfaces at around 50% of the value for the flat diamond control. This, combined with a chemical bactericidal effect of 20–30%, shows that the nanostructured bD surfaces supported significantly fewer viable E. coli than flat surfaces. Moreover, the bD surfaces were particularly effective at preventing the establishment of bacterial aggregates – a precursor to biofilm formation. The percentage of dead bacteria also decreased as a function of hydrophilicity. These results are consistent with a predominantly mechanical mechanism for bacteria death based on the stretching and disruption of the cell membrane, combined with an additional effect from the chemical nature of the surface.
    • The physicochemical investigation of hydrothermally reduced textile waste and application within carbon-based electrodes

      Randviir, Edward P.; Kanou, Omar; Liauw, Christopher M.; Miller, Gary; Andrews, Hayley; Smith, Graham C.; Manchester Metropolitan University; University of Chester (Royal Society of Chemistry, 2019-04-10)
      Textile waste is on the rise due to the expanding global population and the fast fashion market. Large volumes of textile waste are increasing the need for new methods for recycling mixed fabric materials. This paper employs a hydrothermal conversion route for a polyester/cotton mix in phosphoric acid to generate carbon materials (hydrochars) for electrochemical applications. A combination of characterization techniques revealed the reaction products were largely comprised of two major components. The first is a granular material with a surface C : O ratio of 2 : 1 interspersed with phosphorous and titanium proved using energy dispersive X-ray spectroscopy, and the other is a crystalline material with a surface C : O ratio of 3 : 2 containing no phosphorous or titanium. The latter material was found via X-ray diffraction and differential scanning calorimetry to be terephthalic acid. Electrochemical experiments conducted using the hydrochar as a carbon paste electrode demonstrates an increase in current response compared to carbon reference materials. The improved current responses, intrinsically related to the surface area of the material, could be beneficial for electrochemical sensor applications, meaning that this route holds promise for the development of a cheap recycled carbon material, using straightforward methods and simple laboratory reagents.
    • New Quinoline-Based Heterocycles as Anticancer Agents Targeting Bcl-2

      Hamdy, Rania; Elseginy, Samia A.; Ziedan, Noha I.; Jones, Arwyn T.; Westwell, Andrew D. (MDPI, 2019-04-02)
      The Bcl-2 protein has been studied as an anticancer drug target in recent years, due to its gatekeeper role in resisting programmed cancer cell death (apoptosis), and the design of BH3 domain mimetics has led to the clinical approval of Venetoclax (ABT-199) for the treatment of chronic lymphocytic leukaemia. In this work we extend our previous studies on the discovery of indole-based heterocycles as Bcl-2 inhibitors, to the identification of quinolin-4-yl based oxadiazole and triazole analogues. Target compounds were readily synthesized via a common aryl-substituted quinolin-4-carbonyl-N-arylhydrazine-1-carbothioamide (5a⁻b) intermediate, through simple variation of the basic cyclisation conditions. Some of the quinoline-based oxadiazole analogues (e.g. compound 6i) were found to exhibit sub-micromolar anti-proliferative activity in Bcl-2-expressing cancer cell lines, and sub-micromolar IC50 activity within a Bcl2-Bim peptide ELISA assay. The Bcl-2 targeted anticancer activity of 6i was further rationalised via computational molecular modelling, offering possibilities to extend this work into the design of further potent and selective Bcl-2 inhibitory heteroaromatics with therapeutic potential.
    • Next Generation Additive Manufacturing: Tailorable Graphene/Polylactic(acid) Filaments Allow the Fabrication of 3D Printable Porous Anodes for Utilisation within Lithium-Ion Batteries

      Foster, Christopher W.; Zou, Guo-Qiang; Jiang, Yunling; Down, Michael P.; Liauw, Christopher M.; Ferrari, Alejandro Garcia-Miranda; Ji, Xiaobo; Smith, Graham C.; Kelly, Peter J.; Banks, Craig E.; et al. (Wiley, 2019-04-02)
      Herein, we report the fabrication and application of Li-ion anodes for utilisation within Li-ion batteries, which are fabricated via additive manufacturing/3D printing (fused depo- sition modelling) using a bespoke graphene/polylactic acid (PLA) filament, where the graphene content can be readily tailored and controlled over the range 1–40 wt. %. We demon- strate that a graphene content of 20 wt. % exhibits sufficient conductivity and critically, effective 3D printability for the rapid manufacturing of 3D printed freestanding anodes (3DAs); simplifying the components of the Li-ion battery negating the need for a copper current collector. The 3DAs are physicochemcally and electrochemically characterised and possess sufficient conductivity for electrochemical studies. Critically, it is found that if the 3DAs are used in Li-ion batteries the specific capacity is very poor but can be significantly improved through the use of a chemical pre-treatment. Such treatment induces an increased porosity, which results in a 200-fold increase (after anode stabilisation) of the specific capacity (ca. 500 mAhg-1 at a current density of 40 mAg-1). This work significantly enhances the field of additive manufacturing/3D printed graphene based energy storage devices demonstrating that useful 3D printable batteries can be realised
    • A novel ‘bottom-up’ synthesis of few- and multi-layer graphene platelets with partial oxidation via cavitation

      Price, Richard J.; Ladislaus, Paul I.; Smith, Graham C.; Davies, Trevor J.; University of Chester (Price, Davies, Smith), Thomas Swan Ltd (Ladislaus) (Elsevier, 2019-03-28)
      The transient cavitation of diaromatic components such as 1-methylnaphthalene has been used to produce graphene platelets in a ‘bottom-up’ synthesis via the high temperature (>5000 K) conditions that are generated inside collapsing bubbles. Acoustic cavitation produced yields of 5.7×10−11 kgJ−1 at a production rate of 2.2×10−9 kgs−1. This can be improved by generating cavitation hydrodynamically, thus making commercial scale production viable. Hydrodynamic cavitation produced platelets with larger lateral dimensions (≥2 μm) than those formed by acoustic cavitation (10–200 nm). The partially oxidised nature of the platelets enables their covalent chemical functionalisation, which was achieved by combining suitable molecules in the reaction medium to affect a one-pot formation and functionalisation of graphene
    • Chemical ionization quadrupole mass spectrometer with an electrical discharge ion source for atmospheric trace gas measurement

      Eger, Philipp G.; Helleis, Frank; Schuster, Gerhard; Phillips, Gavin J.; Lelieveld, Jos; Crowley, John N.; Max Planck Institute for Chemistry; University of Chester (Copernicus Publications, 2019-03-26)
      We present a chemical ionization quadrupole mass spectrometer (CI-QMS) with a radio-frequency (RF) discharge ion source through N2∕CH3I as a source of primary ions. In addition to the expected detection of PAN, peracetic acid (PAA) and ClNO2 through well-established ion–molecule reactions with I− and its water cluster, the instrument is also sensitive to SO2, HCl and acetic acid (CH3C(O)OH) through additional ion chemistry unique to our ion source. We present ionization schemes for detection of SO2, HCl and acetic acid along with illustrative datasets from three different field campaigns underlining the potential of the CI-QMS with an RF discharge ion source as an alternative to 210Po. The additional sensitivity to SO2 and HCl makes the CI-QMS suitable for investigating the role of sulfur and chlorine chemistry in the polluted marine and coastal boundary layer.
    • Fibre laser treatment of beta TNZT titanium alloys for load-bearing implant applications: Effects of surface physical and chemical features on mesenchymal stem cell response and Staphylococcus aureus bacterial attachment

      Donaghy, Clare L.; McFadden, Ryan; Smith, Graham C.; Kelaini, Sophia; Carson, Louise; Malinov, Savko; Margariti, Andriana; Chan, Chi-Wai; Queens University Belfast; University of Chester (MDPI, 2019-03-12)
      A mismatch in bone and implant elastic modulus can lead to aseptic loosening and ultimately implant failure. Selective elemental composition of titanium (Ti) alloys coupled with surface treatment can be used to improve osseointegration and reduce bacterial adhesion. The biocompatibility and antibacterial properties of Ti-35Nb-7Zr-6Ta (TNZT) using fibre laser surface treatment were assessed in this work, due to its excellent material properties (low Young’s modulus and non-toxicity) and the promising attributes of fibre laser treatment (very fast, non-contact, clean and only causes changes in surface without altering the bulk composition/microstructure). The TNZT surfaces in this study were treated in a high speed regime, specifically 100 and 200 mm/s, (or 6 and 12 m/min). Surface roughness and topography (WLI and SEM), chemical composition (SEM-EDX), microstructure (XRD) and chemistry (XPS) were investigated. The biocompatibility of the laser treated surfaces was evaluated using mesenchymal stem cells (MSCs) cultured in vitro at various time points to assess cell attachment (6, 24 and 48 h), proliferation (3, 7 and 14 days) and differentiation (7, 14 and 21 days). Antibacterial performance was also evaluated using Staphylococcus aureus (S. aureus) and Live/Dead staining. Sample groups included untreated base metal (BM), laser treated at 100 mm/s (LT100) and 200 mm/s (LT200). The results demonstrated that laser surface treatment creates a rougher (Ra value of BM is 199 nm, LT100 is 256 nm and LT200 is 232 nm), spiky surface (Rsk > 0 and Rku > 3) with homogenous elemental distribution and decreasing peak-to-peak distance between ripples (0.63 to 0.315 m) as the scanning speed increases (p < 0.05), generating a surface with distinct micron and nano scale features. The improvement in cell spreading, formation of bone-like nodules (only seen on the laser treated samples) and subsequent four-fold reduction in bacterial attachment (p < 0.001) can be attributed to the features created through fibre laser treatment, making it an excellent choice for load bearing implant applications. Last but not least, the presence of TiN in the outermost surface oxide might also account for the improved biocompatibility and antibacterial performances of TNZT.
    • Nanodiamond based surface modified screen-printed electrodes for the simultaneous voltammetric determination of dopamine and uric acid.

      Baccarin, Marina; Rowley-Neale, Samuel J.; Cavalheiro, Éder T. G.; Smith, Graham C.; Banks, Craig E. (2019-02-22)
      The electroanalytical detection of the neurotransmitter dopamine (DA) in the presence of uric acid (UA) is explored for the first time using commercially procured nanodiamonds (NDs). These are electrically wired via surface modification upon screen-printed graphite macroelectrodes (SPEs). The surface coverage of the NDs on the SPEs was explored in order to optimize electroanalytical outputs to result in well-resolved signals and in low limits of detection. The (electro)analytical outputs are observed to be more sensitive than those achieved at bare (unmodified) SPEs. Such responses, previously reported in the academic literature have been reported to be electrocatalytic and have been previously attributed to the presence of surface sp2 carbon and oxygenated species on the surface of the NDs. However, XPS analysis reveals the commercial NDs to be solely composed of nonconductive sp3 carbon. The low/negligible electroconductivity of the NDs was further confirmed when ND paste electrodes were fabricated and found to exhibit no electrochemical activity. The electroanalytical enhancement, when using NDs electronically wired upon SPEs, is attributed not to the NDs themselves being electrocatalytic, as reported previously, but rather changes in mass transport where the inert NDs block the underlying electroactive SPEs and create a random array of graphite microelectrodes. The electrode was applied to simultaneous sensing of DA and UA at pH 5.5. Figures of merit include (a) low working potentials of around 0.27 and 0.35 V (vs. Ag/AgCl); and (b) detection limits of 5.7 × 10-7 and 8.9 × 10-7 M for DA and UA, respectively. Graphical abstract The electroanalytical enhancement of screen-printed electrodes modified with inert/non-conductive nanodiamonds is due to a change in mass transfer where the inert nanodiamonds facilitate the production of a random microelectrode array.
    • High performing AgNW transparent conducting electrodes with a sheet resistance of 2.5 Ω Sq−1 based upon a roll-to-roll compatible post-processing technique

      Kumar, Dinesh; Stoichkov, Vasil; Brousseau, Emmanuel; Smith, Graham C.; Kettle, Jeff; Bangor University; University of Chester; Cardiff University (Royal Society of Chemistry, 2019-02-12)
      The report of transparent and conducting silver nanowires (AgNWs) that produce remarkable electrical performance, surface planarity and environmental stability is given. This research presents an innovative process that relies on three sequential steps, which are roll-to-roll (R2R) compatible; thermal embossing, infrared sintering and plasma treatment. This process leads to the demonstration of a conductive film with a sheet resistance of 2.5Ω/sq and high transmittance, thus demonstrating the highest reported figure-of-merit in AgNWs to date (FoM = 933). A further benefit of the process is that the surface roughness is substantially reduced compared to traditional AgNW processing techniques. Finally, consideration of the long-term stability is given by developing an accelerated life test process that simultaneously stresses the applied bias and temperature. Regression line fitting shows that a ∼150-times improvement in stability is achieved at ‘normal operational conditions’ when compared to traditionally deposited AgNW films. X-ray photoelectron spectroscopy (XPS) is used to understand the root cause of the improvement in long-term stability, which is related to reduced chemcial changes in the AgNWs.
    • Next-Generation Additive Manufacturing of Complete Standalone Sodium-Ion Energy Storage Architectures

      Down, Michael P.; Martinez-Perinan, Emiliano; Foster, Christopher W.; Lorenzo, Encarnacion; Smith, Graham C.; Banks, Craig E.; Manchester Metropolitan University (Down, Martinez-Perinan, Foster, Banks), Universidad Autonoma Madrid (Lorenzo), University of Chester (Smith) (Wiley, 2019-02-10)
      The first entirely AM/3D-printed sodium-ion (full-cell) battery is reported herein, presenting a paradigm shift in the design and prototyping of energy- storage architectures. AM/3D-printing compatible composite materials are developed for the first time, integrating the active materials NaMnO2 and TiO2 within a porous supporting material, before being AM/3D- printed into a proof-of-concept model based upon the basic geometry of commercially existing AA battery designs. The freestanding and completely AM/3D-fabricated device demonstrates a respectable performance of 84.3 mAh g-1 with a current density of 8.43 mA g-1; note that the structure is typically comprised of 80% thermoplastic, but yet, still works and functions as an energy-storage platform. The AM/3D-fabricated device is critically benchmarked against a battery developed using the same active materials, but fabricated via a traditional manufacturing method utilizing an ink-based/doctor-bladed methodology, which is found to exhibit a specific capacity of 98.9 mAh m-2 (116.35 mAh g-1). The fabrication of fully AM/3D-printed energy-storage architectures compares favorably with traditional approaches, with the former providing a new direction in battery manufacturing. This work represents a paradigm shift in the technological and design considerations in battery and energy-storage architectures
    • In-depth synthetic, physicochemical and in vitro biological investigation of a new ternary V(IV) antioxidant material based on curcumin.

      Papadopoulos, Theodoros A.; Smith, Graham C.; Halevas, Eleftherios; Salifoglou, Athanasios; Swanson, Claudia H.; Hatzidimitriou, Antonios; Katsipis, George; Pantazaki, Anastasia; Sanakis, I.; Mitrikas, George; et al. (Elsevier, 2018-11-06)
      Curcumin is a natural product with a broad spectrum of beneficial properties relating to pharmaceutical applications, extending from traditional remedies to modern cosmetics. The biological activity of such pigments, however, is limited by their solubility and bioavailability, thereby necessitating new ways of achieving optimal tissue cellular response and efficacy as drugs. Metal ion complexation provides a significant route toward improvement of curcumin stability and biological activity, with vanadium being a representative such metal ion, amply encountered in biological systems and exhibiting exogenous bioactivity through potential pharmaceuticals. Driven by the need to optimally increase curcumin bioavailability and bioactivity through complexation, synthetic efforts were launched to seek out stable species, ultimately leading to the synthesis and isolation of a new ternary V(IV)-curcumin-(2,2’-bipyridine) complex. Physicochemical characterization (elemental analysis, FT-IR, Thermogravimetry (TGA), UV-Visible, NMR, ESI-MS, Fluorescence, X-rays) portrayed the solid-state and solution properties of the ternary complex. Pulsed-EPR spectroscopy, in frozen solutions, suggested the presence of two species, cis- and trans-conformers. Density Functional Theory (DFT) calculations revealed the salient features and energetics of the two conformers, thereby complementing EPR spectroscopy. The well-described profile of the vanadium species led to its in vitro biological investigation involving toxicity, cell metabolism inhibition in S. cerevisiae cultures, Reactive Oxygen Species (ROS)-suppressing capacity, lipid peroxidation, and plasmid DNA degradation. A multitude of bio-assays and methodologies, in comparison to free curcumin, showed that it exhibits its antioxidant potential in a concentration-dependent fashion, thereby formulating a bioreactivity profile supporting development of new efficient vanado-pharmaceuticals, targeting (extra)intra-cellular processes under (patho)physiological conditions.
    • Insights into HOx and ROx chemistry in the boreal forest via measurement of peroxyacetic acid, peroxyacetic nitric anhydride (PAN) and hydrogen peroxide

      Crowley, John N.; Pouvesle, Nicolas; Phillips, Gavin J.; Axinte, Raoul; Fischer, Horst; Petaja, Tuukka; Noelscher, Anke C.; Williams, Jonathan; Hens, Korbinian; Harder, Hartwig; et al. (European Geosciences Union, 2018-09-21)
      Unlike many oxidised atmospheric trace gases, which have numerous production pathways, peroxyacetic acid (PAA) and PAN are formed almost exclusively in gas-phase reactions involving the hydroperoxy radical (HO2), the acetyl peroxy radical (CH3C(O)O2) and NO2 and are not believed to be directly emitted in significant amounts by vegetation. As the self-reaction of HO2 is the main photochemical route to hydrogen peroxide (H2O2), simultaneous observation of PAA, PAN and H2O2 can provide insight into the HO2 budget. We present an analysis of observations taken during a summertime campaign in a boreal forest that, in addition to natural conditions, was temporarily impacted by two biomass-burning plumes. The observations were analysed using an expression based on a steady-state assumption using relative PAA-to-PAN mixing ratios to derive HO2 concentrations. The steady-state approach generated HO2 concentrations that were generally in reasonable agreement with measurements but sometimes overestimated those observed by factors of 2 or more. We also used a chemically simple, constrained box model to analyse the formation and reaction of radicals that define the observed mixing ratios of PAA and H2O2. After nudging the simulation towards observations by adding extra, photochemical sources of HO2 and CH3C(O)O2, the box model replicated the observations of PAA, H2O2, ROOH and OH throughout the campaign, including the biomass-burning-influenced episodes during which significantly higher levels of many oxidized trace gases were observed. A dominant fraction of CH3O2 radical generation was found to arise via reactions of the CH3C(O)O2 radical. The model indicates that organic peroxy radicals were present at night in high concentrations that sometimes exceeded those predicted for daytime, and initially divergent measured and modelled HO2 concentrations and daily concentration profiles are reconciled when organic peroxy radicals are detected (as HO2) at an efficiency of 35%. Organic peroxy radicals are found to play an important role in the recycling of OH radicals subsequent to their loss via reactions with volatile organic compounds.
    • Oxidation processes in the eastern Mediterranean atmosphere: evidence from the modelling of HOx measurements over Cyprus

      Mallik, Chinmay; Tomsche, Laura; Bourtsoukidis, Efstratios; Crowley, John N.; Derstroff, Bettina; Fischer, Horst; Hafermann, Sascha; Hueser, Imke; Javed, Umar; Kessel, Stephan; et al. (Copernicus Publications, 2018-07-31)
      The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: Europe, Africa, and Asia. The chemical processing of air masses over this region has implications not only for the air quality but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the northwest of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe. The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides, and other major HOx (OH+HO2) sources and sinks in a low-NOx environment (<100pptv of NO). The model simulations for OH agreed to within 10% with in situ OH observations. Model simulations for HO2 agreed to within 17% of the in situ observations. However, the model strongly under-predicted HO2 at high terpene concentrations, this under-prediction reaching up to 38% at the highest terpene levels. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene-generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene-generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed about one-third of the total OH production, and the maximum recycling efficiency was about 0.7. CO, which was the largest OH sink, was also the largest HO2 source. The lowest HOx production and losses occurred when the air masses had higher residence time over the oceans.
    • Magnetron Sputter-Coated Nanoparticle MoS2 Supported on Nanocarbon: A Highly Efficient Electrocatalyst toward the Hydrogen Evolution Reaction

      Rowley-Neale, Samuel J.; Ratova, Marina; Fugita, Lucas; Smith, Graham C.; Gaffar, Amer; Kulczyk-Malecka, Justyna; Kelly, Peter J.; Banks, Craig E.; Manchester Metropolitan niversity (Rowley-Neale, Ratova, Gaffar, Kulczyk-Malecka, Kelly, Banks), University of Chester (Smith), University Soa Paula (Fugita) (American Chemical Society, 2018-07-03)
      The design and fabrication of inexpensive highly efficient electrocatalysts for the production of hydrogen via the hydrogen evolution reaction (HER) underpin a plethora of emerging clean energy technologies. Herein, we report the fabrication of highly efficient electrocatalysts for the HER based on magnetron-sputtered MoS2 onto a nanocarbon support, termed MoS2/C. Magnetron sputtering time is explored as a function of its physiochemical composition and HER performance; increased sputtering times give rise to materials with differing compositions, i.e., Mo4+ to Mo6+ and associated S anions (sulfide, elemental, and sulfate), and improved HER outputs. An optimized sputtering time of 45 min was used to fabricate the MoS2/C material. This gave rise to an optimal HER performance with regard to its HER onset potential, achievable current, and Tafel value, which were −0.44 (vs saturated calomel electrode (SCE)), −1.45 mV s−1, and 43 mV dec−1, respectively, which has the highest composition of Mo4+ and sulfide (MoS2). Electrochemical testing toward the HER via drop casting MoS2/C upon screen-printed electrodes (SPEs) to electrically wire the nanomaterial is found to be mass coverage dependent, where the current density increases up to a critical mass (ca. 50 μg cm−2), after which a plateau is observed. To allow for a translation of the bespoke fabricated MoS2/C from laboratory to new industrial applications, MoS2/C was incorporated into the bulk ink utilized in the fabrication of SPEs (denoted as MoS2/C-SPE), thus allowing for improved electrical wiring to the MoS2/C and resulting in the production of scalable and reproducible electrocatalytic platforms. The MoS2/C-SPEs displayed far greater HER catalysis with a 450 mV reduction in the HER onset potential and a 1.70 mA cm−2 increase in the achievable current density (recorded at −0.75 V (vs SCE)), compared to a bare/unmodified graphitic SPE. The approach of using magnetron sputtering to modify carbon with MoS2 facilitates the production of mass-producible, stable, and effective electrode materials for possible use in electrolyzers, which are cost competitive to Pt and mitigate the need to use time-consuming and low-yield exfoliation techniques typically used to fabricate pristine MoS2.