• Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential

      Halevesa, Eleftherios; Mavroidi, Barbara; Swanson, Claudia H; Smith, Graham C; Moschona, Alexandra; Hadjispyrou, Spyros; Salifoglou, Athanasios; Pantazakie, Anastasia; Pelecanou, Maria; Litsardakis, George; 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.
    • Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential.

      Halevas, Eleftherios; email: lefterishalevas@gmail.com; Mavroidi, Barbara; Swanson, Claudia H; Smith, Graham C; Moschona, Alexandra; Hadjispyrou, Spyros; Salifoglou, Athanasios; Pantazaki, Anastasia A; Pelecanou, Maria; Litsardakis, George (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. [Abstract copyright: Copyright © 2019 Elsevier Inc. All rights reserved.]
    • 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.
    • 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.
    • Evidence of Lipid Exchange in Styrene Maleic Acid Lipid Particle (SMALP) Nanodisc Systems

      Hazell, Gavin; Arnold, Thomas; Tognoloni, Cecilia; Barker, Robert; Clifton, Luke; Steinke, Nina-Juliane; Edler, Karen; University of Chester, University of Bath, University of Dundee, ISIS, Diamond Light Source (American Chemical Society, 2016-10-14)
      Styrene-alt-maleic Acid lipid particles (SMALPs) are self-assembled discoidal structures composed of a polymer belt and a segment of lipid bilayer, which are capable of encapsulating membrane proteins directly from the cell membrane. Here we present evidence of the exchange of lipids between such “nanodiscs” and lipid monolayers adsorbed at either solid-liquid or air-liquid interfaces. This behavior has important implications for the potential uses of nanodiscs, including the potential to control lipid composition within nanodiscs containing membrane proteins
    • 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
    • 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.
    • 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
    • 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. (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 kgJ at a production rate of 2.2 × 10 kgs . 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. [Abstract copyright: Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.]
    • 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.
    • 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.
    • 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.
    • Diamond-coated ‘black Si’ as a promising material for high-surface-area electrochemical electrodes and antibacterial surfaces

      May, Paul W.; Clegg, Michael; Silva, T.; Zanin, H.; Fatibello-Filho, O.; Celorrio, V.; Fermin, David; Welch, Colin C.; Hazell, Gavin; Fisher, Leanne E.; et al. (Royal Society of Chemistry, 2016-08-08)
      This report describes a method to fabricate high-surface-area boron-doped diamond (BDD) electrodes using so-called ‘black silicon’ (bSi) as a substrate. This is a synthetic nanostructured material that contains high-aspect-ratio nano-protrusions, such as spikes or needles, on the Si surface produced via plasma etching. We now show that coating a bSi surface composed of 15-μm-high needles conformably with BDD produces a robust electrochemical electrode with high sensitivity and high electroactive area. A clinically relevant demonstration of the efficacy of these electrodes is shown by measuring their sensitivity for detection of dopamine (DA) in the presence of an excess of uric acid (UA). Finally, the nanostructured surface of bSi has recently been found to generate a mechanical bactericidal effect, killing both Gram-negative and Gram-positive bacteria at high rates. We will show that BDD-coated bSi also acts as an effective antibacterial surface, with the added advantage that being diamond-coated it is far more robust and less likely to become damaged than Si.
    • Magnetically Responsive Materials based on Polymeric Ionic Liquids and Graphene Oxide for Water Clean-up

      Hazell, Gavin; Hinojosa-Navarro, Miguel; McCoy, Thomas; Tabor, Rico; Eastoe, Julian; University of Chester, University of Bristol, Monash University (Elsevier, 2015-11-14)
      Hypothesis Owing to attractive interactions between negatively charged graphene oxide (GO) and a paramagnetic cationic polyelectrolyte (polyallydimethylammonium chloride with a FeCl4− counterion (Fe-polyDADMAC) it should be possible to generate magnetic materials. The benefit of using charge-based adsorption is that the need to form covalently linked magnetic materials is offset, which is expected to significantly reduce the time, energy and cost to make such responsive materials. These systems could have a wide use and application in water treatment. Experiments Non-covalent magnetic materials were formed through the mixing of Fe-pDADMAC and GO. A systematic study was conducted by varying polymer concentration at a fixed GO concentration. UV–Vis was used to confirm and quantify polymer adsorption onto GO sheets. The potential uses of the systems for water purification were demonstrated. Findings Fe-polyDADMAC adsorbs to the surface of GO and induces flocculation. Low concentrations of the polymer (<9 mmol/L) favour flocculation, whereas higher concentrations (>20 mmol/L) induce restabilization. Difficult-to-recover gold nanoparticles can be separated from suspensions as well as the pollutant antibiotic tetracycline. Both harmful materials can be magnetically recovered from the dispersions. This system therefore has economical and practical applications in decontamination and water treatment.
    • Surfactants at the design limit

      Hazell, Gavin; Czajka, Adam; Eastoe, Julian; University of Chester, University of Bristol (American Chemical Society, 2015-08-04)
      This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, γcmc. Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence γcmc. By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter ϕcmc represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that ϕcmc is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.
    • 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.
    • 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.
    • 3D printed graphene based energy storage devices

      Foster, Christopher W.; Down, Michael P.; Zhang, Yan; Ji, Xiaobo; Rowley-Neale, Samuel J.; Smith, Graham C.; Kelly, Peter J.; Banks, Craig E.; Manchester Metropolitan University; University of Chester; Central South University Changsha (Springer Nature, 2017-03-03)
      3D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices’ to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (−0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (−0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised.