Imperial College London

ProfessorMaryRyan

Faculty of EngineeringDepartment of Materials

Vice-Dean (Research), Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6755m.p.ryan

 
 
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Location

 

B338Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

220 results found

Scatigno GG, Dong P, Ryan MP, Wenman MRet al., 2019, The effect of salt loading on chloride-induced stress corrosion cracking of 304L austenitic stainless steel under atmospheric conditions, Materialia, Vol: 8

© 2019 The effect of salt loading on chloride-induced stress corrosion cracking in 304 L was studied at atmospheric pressure. Stress relieved samples were uniaxially pre-strained to 5% and were loaded with nine levels of MgCl2, investigating Cl− deposition levels from 1.7 × 10−4 to 3.1 x 10−2 g cm−2. Samples were subject to 60 MPa stress, 90 °C at 70% relative humidity, for 480 h. A direct correlation between chloride deposition and the density of cracking and corrosion was observed between 5.7 × 10−4 and 1.96 × 10−2 g cm−2. Crack propagation rates were constant between salt loadings of 5.7 × 10−4 and 2.4 × 10−2 g cm−2 at 1–2 µm h−1.

Journal article

Parra-Puerto A, NG KL, Fahy K, Goode AE, Ryan MP, Kucernak Aet al., Supported transition metal phosphides: Activity survey for HER, ORR, OER and corrosion resistance in acid and alkaline electrolytes, ACS Catalysis, ISSN: 2155-5435

Carbon supported MxPy (M = Ni, Co, W, Cr and Mo) were prepared via pyrolysis using a very simple and scalable method utilizing non-toxic metal and phosphorous precursors. The electrochemical hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER) reactions and corrosion resistance under both acid and alkaline conditions were examined for all these catalysts and compared to the benchmark catalysts Pt/C (HER/ORR) and IrO2(OER). The highest activities were found in alkaline solutions for Co2P for HER and ORR and Ni2P for OER. Good activity for these was also found in acid for some of these reactions, although the catalysts suffered from susceptibility to corrosion. Co2P was further studied in an alkaline environment as it shows high catalytic activity towards the oxygen reduction reaction (ORR) without significant hysteresis. The onset potential (at 0.5 mA cm-2) obtained was 0.8 V and a Tafel slope value of 38 mV dec-1 with a maximum kinetic mass activity of 2870 A gCo-1 at 0.7 V (RHE). Utilising high resolution transmission electron microscopy (HRTEM) it is possible to observe high-surface area needle-like single crystal cobalt oxide structures on the surfaces of the Co2P particles at the beginning of the ORR. Hence the high rates of initial corrosion of the Co2P identified appear to be associated with the dissolution and precipitation of Cobalt oxide on the particle surface. The as-synthesised Co2P/C also shows good performance in an 8-hour stability test for the Oxygen Evolution Reaction (OER), carried out at 1.6 V vs. RHE in alkaline conditions, with negligible drop in current density over time. Interestingly, in an acidic environment the catalyst is very active towards 2-electron- oxygen reduction leading to H2O2 with high selectivity (85%). It is intriguing that the pH dependence on this catalyst towards the ORR is similar to that seen for gold.

Journal article

Gomez-Gonzalez MA, Koronfel MA, Goode AE, Al-Ejji M, Voulvoulis N, Parker JE, Quinn PD, Scott TB, Xie F, Yallop ML, Porter AE, Ryan MPet al., 2019, Spatially resolved dissolution and speciation changes of ZnO nanorods during short-term in situ incubation in a simulated wastewater environment, ACS Nano, Vol: 13, Pages: 11049-11061, ISSN: 1936-0851

Zinc oxide engineered nanomaterials (ZnO ENMs) are used in a variety of applications worldwide due to their optoelectronic and antibacterial properties with potential contaminant risk to the environment following their disposal. One of the main potential pathways for ZnO nanomaterials to reach the environment is via urban wastewater treatment plants. So far there is no technique that can provide spatiotemporal nanoscale information about the rates and mechanisms by which the individual nanoparticles transform. Fundamental knowledge of how the surface chemistry of individual particles change, and the heterogeneity of transformations within the system, will reveal the critical physicochemical properties determining environmental damage and deactivation. We applied a methodology based on spatially resolved in situ X-ray fluorescence microscopy (XFM), allowing observation of real-time dissolution and morphological and chemical evolution of synthetic template-grown ZnO nanorods (∼725 nm length, ∼140 nm diameter). Core-shell ZnO-ZnS nanostructures were formed rapidly within 1 h, and significant amounts of ZnS species were generated, with a corresponding depletion of ZnO after 3 h. Diffuse nanoparticles of ZnS, Zn3(PO4)2, and Zn adsorbed to Fe-oxyhydroxides were also imaged in some nonsterically impeded regions after 3 h. The formation of diffuse nanoparticles was affected by ongoing ZnO dissolution (quantified by inductively coupled plasma mass spectrometry) and the humic acid content in the simulated sludge. Complementary ex situ X-ray absorption spectroscopy and scanning electron microscopy confirmed a significant decrease in the ZnO contribution over time. Application of time-resolved XFM enables predictions about the rates at which ZnO nanomaterials transform during their first stages of the wastewater treatment process.

Journal article

Leo BF, Fearn S, Gonzalez-Carter D, Theodorou I, Ruenraroengsak P, Goode A, Mcphail D, Dexter DT, Shaffer MSP, Chung KF, Porter AE, Ryan MPet al., 2019, Label-free TOF-SIMS imaging of sulfur producing enzymes inside microglia cells following exposure to silver nanowires, Analytical Chemistry, Vol: 91, Pages: 11098-11107, ISSN: 0003-2700

There are no methods sensitive enough to detect enzymes within cells, without the use of analyte labelling. Here we show that it is possible to detect protein ion signals of three different H2S-synthesizing enzymes inside microglia after pre-treatment with silver nanowires (AgNW) using time of flight-secondary ion mass spectrometry (TOF-SIMS). Protein fragment ions, including the fragment of amino acid (C4H8N+ - 70 amu), fragments of the sulfur producing cystathionine-containing enzymes and the Ag+ ion signal could be detected without the use of any labels; the cells were mapped using the C4H8N+ amino acid fragment. Scanning electron microscopy imaging and energy dispersive x-ray chemical analysis showed that the AgNWs were inside the same cells imaged by TOF-SIMS and transformed chemically into crystalline Ag2S within cells in which the sulfur producing proteins were detected. The presence of these sulfur producing cystathionine-containing enzymes within the cells was confirmed by Western Blots and confocal microscopy images of fluorescently labelled antibodies against the sulfur producing enzymes. Label-free ToF-SIMS is very promising for the label-free identification of H2S-contributing enzymes and their cellular localization in biological systems. The technique could in future be used to identify which of these enzymes are most contributory.

Journal article

Ruenraroengsak P, Kiryushko D, Theodorou IG, Klosowski MM, Taylor ER, Niriella T, Palmieri C, Yagüe E, Ryan MP, Coombes RC, Xie F, Porter AEet al., 2019, Frizzled-7-targeted delivery of zinc oxide nanoparticles to drug-resistant breast cancer cells, Nanoscale, Vol: 11, Pages: 12858-12870, ISSN: 2040-3364

There is a need for novel strategies to treat aggressive breast cancer subtypes and overcome drug resistance. ZnO nanoparticles (NPs) have potential in cancer therapy due to their ability to potently and selectively induce cancer cell apoptosis. Here, we tested the in vitro chemotherapeutic efficacy of ZnONPs loaded via a mesoporous silica nanolayer (MSN) towards drug-sensitive breast cancer cells (MCF-7: estrogen receptor-positive, CAL51: triple-negative) and their drug-resistant counterparts (MCF-7TX, CALDOX). ZnO-MSNs were coated on to gold nanostars (AuNSs) for future imaging capabilities in the NIR-II range. Electron and confocal microscopy showed that MSN-ZnO-AuNSs accumulated close to the plasma membrane and were internalized by cells. High-resolution electron microscopy showed that MSN coating degraded outside the cells, releasing ZnONPs that interacted with cell membranes. MSN-ZnO-AuNSs efficiently reduced the viability of all cell lines, and CAL51/CALDOX cells were more susceptible than MCF7/MCF-7-TX cells. MSN-ZnO-AuNSs were then conjugated with the antibody to Frizzled-7 (FZD-7), the receptor upregulated by several breast cancer cells. We used the disulphide (S-S) linker that could be cleaved with a high concentration of glutathione normally observed within cancer cells, releasing Zn2+ into the cytoplasm. FZD-7 targeting resulted in approximately three-fold amplified toxicity of MSN-ZnO-AuNSs towards the MCF-7TX drug-resistant cell line with the highest FZD-7 expression. This study shows that ZnO-MSs are promising tools to treat triple-negative and drug-resistant breast cancers and highlights the potential clinical utility of FZD-7 for delivery of nanomedicines and imaging probes specifically to these cancer types.

Journal article

Pang JS, Theodorou IG, Centeno A, Petrov PK, Alford NM, Ryan MP, Xie Fet al., 2019, Tunable three-dimensional plasmonic arrays for large near-infrared fluorescence enhancement, ACS Applied Materials & Interfaces, Vol: 11, Pages: 23083-23092, ISSN: 1944-8244

Metal-enhanced fluorescence (MEF), resulting from the near-field interaction of fluorophores with metallic nanostructures, has emerged as a powerful tool for dramatically improving the performance of fluorescence-based biomedical applications. Allowing for lower autofluorescence and minimal photoinduced damage, the development of multifunctional and multiplexed MEF platforms in the near-infrared (NIR) windows is particularly desirable. Here, a low-cost fabrication method based on nanosphere lithography is applied to produce tunable three-dimensional (3D) gold (Au) nanohole–disc arrays (Au-NHDAs). The arrays consist of nanoscale glass pillars atop nanoholes in a Au thin film: the top surfaces of the pillars are Au-covered (effectively nanodiscs), and small Au nanoparticles (nanodots) are located on the sidewalls of the pillars. This 3D hole–disc (and possibly nanodot) construct is critical to the properties of the device. The versatility of our approach is illustrated through the production of uniform and highly reproducible Au-NHDAs with controlled structural properties and tunable optical features in the NIR windows. Au-NHDAs allow for a very large NIR fluorescence enhancement (more than 400 times), which is attributed to the 3D plasmonic structure of the arrays that allows strong surface plasmon polariton and localized surface plasmon resonance coupling through glass nanogaps. By considering arrays with the same resonance peak and the same nanodisc separation distance, we show that the enhancement factor varies with nanodisc diameter. Using computational electromagnetic modeling, the electric field enhancement at 790 nm was calculated to provide insights into excitation enhancement, which occurs due to an increase in the intensity of the electric field. Fluorescence lifetime measurements indicate that the total fluorescence enhancement may depend on controlling excitation enhancement and therefore the array morphology. Our findings provide important in

Journal article

Sk MH, Qi J, Al-Qahtani N, Abdullah AM, Laycock N, Ryan MP, Williams DEet al., 2019, Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel (vol 166, C3233, 2019), JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: X3-X3, ISSN: 0013-4651

Journal article

Sk MH, Qi J, Abdullah AM, Laycock N, Ryan MP, Williams DEet al., 2019, Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: C3233-C3240, ISSN: 0013-4651

Journal article

Koronfel MA, Goode AE, Gomez-Gonzalez MA, Nelson Weker J, Simões TA, Brydson R, Quinn P, Toney MF, Hart A, Porter AE, Ryan MPet al., Chemical Evolution of CoCrMo Wear Particles: an In-Situ Characterisation Study, The Journal of Physical Chemistry C, ISSN: 1932-7447

Journal article

Hadden JHL, Ryan MP, Riley DJ, 2019, Examining the charging behaviour of nickel hydroxide nanomaterials, Electrochemistry Communications, Vol: 101, Pages: 47-51, ISSN: 1388-2481

To investigate the depth of charging at the material surface, batches of nickel hydroxide nanoparticles were hydrothermally synthesised in the range 3–450 nm. Any surfactant added was removed post synthesis using ozone. The capacity per gram (Cs) increased and the capacity per unit area (CA) was constant with decreasing particle size down to 20 nm. Further reduction in particle size resulted in a decrease in both CS and CA, suggesting the Ni(OH)2 is charged to a depth in the order of 10 nm at the charging rate studied. The results obtained have implications in the design of Ni(OH)2 electrodes in charge storage applications.

Journal article

Guo L, Lovell E, Wilson N, Burdett P, Cohen LF, Ryan MPet al., 2019, The electrochemical behaviour of magnetocaloric alloys La(Fe,Mn,Si)13Hx under magnetic field conditions, Chemical Communications, Vol: 55, Pages: 3642-3645, ISSN: 1359-7345

The degradation mechanism of La(Fe,Mn,Si)13Hx has been examined under conditions representative of the complex operating parameters of a refrigeration cycle. The magnetic field effects are found to be dominated by magneto-transport and are most significant when the material is in its paramagnetic state - resulting in significantly accelerated corrosion rates.

Journal article

Theodorou I, Ruenraroengsak P, Carter D, Jiang Q, Yague E, Aboagye E, Coombes RC, Porter AE, Ryan M, Xie Fet al., 2019, Towards multiplexed near-infrared cellular imaging using gold nanostar arrays with tunable fluorescence enhancement, Nanoscale, Vol: 11, Pages: 2079-2088, ISSN: 2040-3364

Sensitive detection of disease biomarkers expressed by human cells is critical to the development of novel diagnostic and therapeutic methods. Here we report that plasmonic arrays based on gold nanostar (AuNS) monolayers enable up to 19-fold fluorescence enhancement for cellular imaging in the near-infrared (NIR) biological window, allowing the application of low quantum yield fluorophores for sensitive cellular imaging. The high fluorescence enhancement together with low autofluorescence interference in this wavelength range enable higher signal-to-noise ratio compared to other diagnostic modalities. Using AuNSs of different geometries and therefore controllable electric field enhancement, cellular imaging with tunable enhancement factors is achieved, which may be useful for the development of multicolour and multiplexed platforms for a panel of biomarkers, allowing to distinguish different subcell populations at the single cell level. Finally, the uptake of AuNSs within HeLa cells and their high biocompatibility, pave the way for novel high-performance in vitro and in vivo diagnostic platforms.

Journal article

Theodorou I, Jiang Q, Malms L, Xie X, Coombes RC, Aboagye E, Porter AE, Ryan M, Xie Fet al., 2018, Fluorescence enhancement from single gold nanostars: towards ultra-bright emission in the first and second near-infrared biological windows, Nanoscale, Vol: 10, Pages: 15854-15864, ISSN: 2040-3364

Gold nanostars (AuNSs) are promising agents for the development of high-performance diagnostic devices, by enabling metal enhanced fluorescence (MEF) in the physiological near-infrared (NIR) and second near-infrared (NIR-II) windows. The local electric field near their sharp tips and between their branches can be enhanced by several orders of magnitude, holding great promise for large fluorescence enhancements from single AuNS particles, rather than relying on interparticle coupling in nanoparticle substrates. Here, guided by electric field simulations, two different types of AuNSs with controlled morphologies and plasmonic responses in the NIR and NIR-II regions are used to investigate the mechanism of MEF from colloidal AuNSs. Fluorophore conjugation to AuNSs allows significant fluorescence enhancement of up to 30 times in the NIR window, and up to 4-fold enhancement in the NIR-II region. Together with other inherent advantages of AuNSs, including their multispike morphology offering easy access to cell membranes and their large surface area providing flexible multifunctionality, AuNS are promising for the development of in vivo imaging applications. Using time-resolved fluorescence measurements to deconvolute semi-quantitatively excitation enhancement from emission enhancement, we show that a combination of enhanced excitation and an increased radiative decay rate, both contribute to the observed large enhancement. In accordance to our electric field modelling, however, excitation enhancement is the component that varies most with particle morphology. These findings provide important insights into the mechanism of MEF from AuNSs, and can be used to further guide particle design for high contrast enhancement, enabling the development of MEF biodetection technologies.

Journal article

Qin H, Wu D, Sathian J, Xie X, Ryan M, Xie Fet al., 2018, Tuning the upconversion photoluminescence lifetimes of NaYF4:Yb3+, Er3+ through lanthanide Gd3+ doping, Scientific Reports, Vol: 8, ISSN: 2045-2322

The multiplexing capacity of conventional fluorescence materials are significantly limited by spectral overlap and background interference, mainly due to their short-lived fluorescence lifetimes. Here, we adopt a novel Gd3+ doping strategy in NaYF4 host materials, realized tuning of upconversion photoluminescence (UCPL) lifetimes at selective emissions. Time-correlated single-photon counting (TCSPC), was applied to measure the photoluminescence lifetimes accurately. We demonstrated the large dynamic range of lifetimes of upconversion nanoparticles with good upconversion quantum yields, mainly owing to the dominance of high efficient energy transfer upconversion mechanism. The exceptional tunable properties of upconversion materials allow great potential for them to be utilized in biotechnology and life sciences.

Journal article

Ellis T, Chiappi M, García-Trenco A, Al-Ejji M, Sarkar S, Georgiou TK, Shaffer MSP, Tetley TD, Schwander S, Ryan MP, Porter AEet al., 2018, Multimetallic microparticles increase the potency of rifampicin against intracellular mycobacterium tuberculosis, ACS Nano, Vol: 12, Pages: 5228-5240, ISSN: 1936-0851

Mycobacterium tuberculosis ( M.tb) has the extraordinary ability to adapt to the administration of antibiotics through the development of resistance mechanisms. By rapidly exporting drugs from within the cytosol, these pathogenic bacteria diminish antibiotic potency and drive the presentation of drug-tolerant tuberculosis (TB). The membrane integrity of M.tb is pivotal in retaining these drug-resistant traits. Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) are established antimicrobial agents that effectively compromise membrane stability, giving rise to increased bacterial permeability to antibiotics. In this work, biodegradable multimetallic microparticles (MMPs), containing Ag NPs and ZnO NPs, were developed for use in pulmonary delivery of antituberculous drugs to the endosomal system of M.tb-infected macrophages. Efficient uptake of MMPs by M.tb-infected THP1 cells was demonstrated using an in vitro macrophage infection model, with direct interaction between MMPs and M.tb visualized with the use of electron FIB-SEM tomography. The release of Ag NPs and ZnO NPs within the macrophage endosomal system increased the potency of the model antibiotic rifampicin by as much as 76%, realized through an increase in membrane disorder of intracellular M.tb. MMPs were effective at independently driving membrane destruction of extracellular bacilli located at the exterior face of THP1 macrophages. This MMP system presents as an effective drug delivery vehicle that could be used for the transport of antituberculous drugs such as rifampicin to infected alveolar macrophages, while increasing drug potency. By increasing M.tb membrane permeability, such a system may prove effectual in improving treatment of drug-susceptible TB in addition to M.tb strains considered drug-resistant.

Journal article

Wang T, Centeno A, Darvill D, Pang J, Ryan MP, Xie Fet al., 2018, Tuneable fluorescence enhancement over nanostructured ZnO arrays with controlled morphology, Physical Chemistry Chemical Physics, Vol: 21, Pages: 14828-14834, ISSN: 1463-9076

Zinc oxide (ZnO) nanorods (NRs) have been demonstrated as a promising platform for enhanced fluorescence-based sensing. It is, however, desirable to achieve a tuneable fluorescence enhancement with these platforms so that the fluorescence output can be adjusted based on the real need. Here we show that the fluorescence enhancement can be tuned by changing the diameter of the ZnO nanorods, simply controlled by potassium chloride (KCl) concentration during synthesis, using arrays of previously developed aligned NRs (a.k.a. aligned NR forests) and nanoflowers (NFs). Combining the experimental results obtained from ZnO nanostructures with controlled morphology and computer-aided verification, we show that the fluorescence enhancement factor increases when ZnO NRs become thicker. The fluorescence enhancement factor of NF arrays is shown to have a much stronger dependency on the rod diameter than that of aligned NR arrays. We prove that the morphology of nanostructures, which can be controlled, can be an important factor for fluorescence enhancement. Our (i) effort towards understanding the structure–property relationships of ZnO nanostructured arrays and (ii) demonstration on tuneable fluorescence enhancement by nanostructure engineering can provide some guidance towards the rational design of future fluorescence amplification platforms potentially for bio-sensing.

Journal article

Sk MH, Abdullah AM, Qi J, Ko M, Ingham B, Laycock N, Ryan MP, Williams DEet al., 2018, The effects of Cr/Mo micro-alloying on the corrosion behavior of carbon steel in CO2-saturated (sweet) brine under hydrodynamic control, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 165, Pages: C278-C288, ISSN: 0013-4651

The effects of micro-alloying of plain carbon steel with Cr and Mo on the corrosion behavior in CO2-saturated (sweet) brine (0.5 MNaCl, pH 6.6) environment, under hydrodynamic conditions, at 80◦C were investigated. Crystalline siderite/chukanovite scalesformed on all the alloys. Analysis of potentiostatic current transient data suggest that there exists a synergistic interaction betweenCr and Mo, which induces more rapid crystallization of the scale compared to Mo-free steels. Increasing the Mo content alsosuppressed the transport-dependent dissolution current passing through the initially-present amorphous surface film. TEM imagesof the FIB-sectioned corrosion scales confirm that the corrosion scale formed on 1Cr0.7Mo is comparatively thinner and yet offersgreater protectiveness when compared to the plain carbon steel.

Journal article

Botelho D, Leo BF, Massa C, Sarkar S, Tetley T, Chung KF, Chen S, Ryan MP, Porter A, Atochina-Vasserman EN, Zhang J, Schwander S, Gow AJet al., 2018, Exposure to silver nanospheres leads to altered respiratory mechanics and delayed immune response in an in vivo Murine model, Frontiers in Pharmacology, Vol: 9, ISSN: 1663-9812

Here we examine the organ level toxicology of both carbon black (CB) and silver nanoparticles (AgNP). We aim to determine metal-specific effects to respiratory function, inflammation and potential interactions with lung lining fluid (LLF). C57Bl6/J male mice were intratracheally instilled with saline (control), low (0.05 μg/g) or high (0.5 μg/g) doses of either AgNP or CB 15 nm nanospheres. Lung histology, cytology, surfactant composition and function, inflammatory gene expression, and pulmonary function were measured at 1, 3, and 7 days post-exposure. Acutely, high dose CB resulted in an inflammatory response, increased neutrophilia and cytokine production, without alteration in surfactant composition or respiratory mechanics. Low dose CB had no effect. Neither low nor high dose AgNPs resulted in an acute inflammatory response, but there was an increase in work of breathing. Three days post-exposure with CB, a persistent neutrophilia was noted. High dose AgNP resulted in an elevated number of macrophages and invasion of lymphocytes. Additionally, AgNP treated mice displayed increased expression of IL1B, IL6, CCL2, and IL10. However, there were no significant changes in respiratory mechanics. At day 7, inflammation had resolved in AgNP-treated mice, but tissue stiffness and resistance were significantly decreased, which was accompanied by an increase in surfactant protein D (SP-D) content. These data demonstrate that the presence of metal alters the response of the lung to nanoparticle exposure. AgNP-surfactant interactions may alter respiratory function and result in a delayed immune response, potentially due to modified airway epithelial cell function.

Journal article

Koronfel MA, Goode AE, Weker JN, Tay SER, Stitt CA, Simoes TA, Mosselmans JFW, Quinn P, Brydson R, Hart A, Toney MF, Porter AE, Ryan MPet al., 2018, Understanding the reactivity of CoCrMo-implant wear particles, npj Materials Degradation, Vol: 2, ISSN: 2397-2106

CoCrMo-based metal-on-metal hip implants experienced unexpectedly high failure rates despite the high wear and corrosion resistance of the bulk material. Although they exhibit a lower volumetric wear compared to other implant materials, CoCrMo-based implants produced a significantly larger 'number' of smaller wear particles. CoCrMo is nominally an extremely stable material with high Cr content providing passivity. However, despite the Co:Cr ratio in the original alloy being 2:1; chemical analyses of wear particles from periprosthetic tissue have found the particles to be composed predominately of Cr species, with only trace amounts of Co remaining. Here a correlative spectroscopy and microscopy approach has shown that these particles dissolve via a non-stoichiometric, and geometrically inhomogeneous, mechanism similar to de-alloying. This mechanism is previously unreported for this material and was not apparent in any of the regulatory required tests, suggesting that such tests are insufficiently discriminating.

Journal article

Zhang Y, Cao M, Lv H, Wei J, Gu Y, Liu D, Zhang W, Ryan MP, Wu Xet al., 2018, Electrodeposited nanometer-size IrO2/Ti electrodes with 0.3 mg IrO2 cm(-2) for sludge dewatering electrolysers, ELECTROCHIMICA ACTA, Vol: 265, Pages: 507-513, ISSN: 0013-4686

Journal article

Cal E, Qi J, Preedy O, Chen S, Boldrin D, Branford WR, Vandeperre L, Ryan MPet al., 2018, Functionalised magnetic nanoparticles for uranium adsorption with ultra-high capacity and selectivity, Journal of Materials Chemistry A, Vol: 6, Pages: 3063-3073, ISSN: 2050-7496

The removal of radioactive contaminants from the environment for safe and efficient waste disposal is a critical challenge, requiring the development of novel selective and high-capacity sequestering materials. In this paper the design of superparamagnetic iron oxide nanoparticles (SPIONs) as highly efficient magnetic-sorbent structures for uranium (U(VI)) separation is described. The nanosorbent was developed by surface functionalisation of single crystalline magnetite (Fe3O4) nanoparticles with a phosphate-based complex coating. This new design allowed for the development of a magnetically separable ultra-effective sorbent, with a measured U(VI) sorption capacity of ∼2333 mg U per g Fe (1690 mg U per g Fe3O4 NP), significantly higher than everything previously reported. Based on TEM analysis, it is proposed that these properties are the result of a multi-layer ligand structure, which enables a high degree of U-incorporation compared to conventional surface-ligand systems. Moreover, the phosphate-NP construct ((PO)x-Fe3O4) shows exceptionally high specificity for the sequestration of U(VI) in solution at pH 7. Adsorption tests in the presence of competing ions, such as Sr(II), Ca(II) and Mg(II), showed high selectivity of the nanoparticles for U(VI) and extremely rapid kinetics of contaminant removal from solution, with the total amount of uranyl ions being removed after only 60 seconds of contact with the NPs. The results presented in this paper highlight the potential of such a phosphate-functionalised magnetic nanosorbent as a highly effective material for the remediation of U(VI) from contaminated water and industrial scenarios.

Journal article

Hassan Sk M, Abdullah AM, Ryan MP, Ko M, Williams DE, Laycock N, Ingham Bet al., 2018, Mo-mediated corrosion behaviour of 1 Cr - Carbon steel in sweet medium under hydrodynamic control, ISSN: 0361-4409

© 2018 by NACE International. The effects of micro-alloying of plain carbon steel with Mo (0.7 wt.%) in the presence of 1 wt.% Cr on the corrosion behaviour and scale protectiveness in CO2 saturated (sweet) brine (0.5 M NaCl) environment, under hydrodynamic conditions, at 80°C in a slightly acidic environment (pH 6.6) were investigated. Potentiostatic current transients suggest that there exists a synergistic interaction of Cr and Mo, which induces more rapid scale crystallization compared to the Mo-free steel. The presence of Mo also suppressed the current passing through corrosion scale. SEM images suggested that 1Cr.0.7Mo steel induced formation of thinner scale with better protectiveness compared to their non-Mo counterparts. From the mechanistic perspective, we suggest that the addition of small amounts of Mo induces formation of a crystalline scale at short times and then it accelerates the growth of that crystalline layer, by modifying the local environment at the steel surface. Modeling of this hypothesis is currently in progress.

Conference paper

Meyer N, Rivera LR, Ellis T, Qi J, Ryan MP, Boccaccini ARet al., 2018, Bioactive and Antibacterial Coatings Based on Zein/Bioactive Glass Composites by Electrophoretic Deposition, COATINGS, Vol: 8, ISSN: 2079-6412

Journal article

Skinner SJ, ryan MP, pramana S, cavallaro A, li C, handoko A, Chan KW, walker RJ, Regoutz A, herrin J, Yeo BS, Payne DJ, kilner JAet al., 2017, Crystal structure and surface characteristics of Sr-doped GdBaCo2O6-δ double perovskites: oxygen evolution reaction and conductivity, Journal of Materials Chemistry A, Vol: 6, Pages: 5335-5345, ISSN: 2050-7496

A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.

Journal article

Luongo G, Perez JE, Kosel J, Georgiou TK, Regoutz A, Payne DJ, Stevens MM, Porter AE, Dunlop IEet al., 2017, Scalable high-affinity stabilization of magnetic iron oxide nanostructures by a biocompatible antifouling homopolymer, ACS Applied Materials and Interfaces, Vol: 9, Pages: 40059-40069, ISSN: 1944-8244

Iron oxide nanostructures have been widely developed for biomedical applications, due to their magnetic properties and biocompatibility. In clinical application, the stabilization of these nanostructures against aggregation and non-specific interactions is typically achieved using weakly anchored polysaccharides, with better-defined and more strongly anchored synthetic polymers not commercially adopted due to complexity of synthesis and use. Here, we show for the first time stabilization and biocompatibilization of iron oxide nanoparticles by a synthetic homopolymer with strong surface anchoring and a history of clinical use in other applications, poly(2-methacryloyloxyethy phosphorylcholine) (poly(MPC)). For the commercially important case of spherical particles, binding of poly(MPC) to iron oxide surfaces and highly effective individualization of magnetite nanoparticles (20 nm) are demonstrated. Next-generation high-aspect ratio nanowires (both magnetite/maghemite and core-shell iron/iron oxide) are furthermore stabilized by poly(MPC)-coating, with nanowire cytotoxicity at large concentrations significantly reduced. The synthesis approach is exploited to incorporate functionality into the poly(MPC) chain is demonstrated by random copolymerization with an alkyne-containing monomer for click-chemistry. Taking these results together, poly(MPC) homopolymers and random copolymers offer a significant improvement over current iron oxide nanoformulations, combining straightforward synthesis, strong surface-anchoring and well-defined molecular weight.

Journal article

Theodorou IG, Muller KH, Chen S, Goode AE, Yufit V, Ryan MP, Porter AEet al., 2017, Silver Nanowire Particle Reactivity with Human Monocyte-Derived Macrophage Cells: Intracellular Availability of Silver Governs Their Cytotoxicity, ACS BIOMATERIALS SCIENCE & ENGINEERING, Vol: 3, Pages: 2336-2347, ISSN: 2373-9878

Silver nanowires (AgNWs) are increasingly being used in the production of optoelectronic devices, with manufacturing processes posing a risk for occupational exposures via inhalation. Although some studies have explored the environmental effects of AgNWs, few data exist on human health effects. Alveolar macrophages are central in the clearance of inhaled fibers from the lungs, with frustrated phagocytosis often stated as a key determinant for the onset of inflammatory reactions. However, the mechanisms through which fully ingested AgNWs interact with, degrade, and transform within primary macrophages over time, and whether the reactivity of the AgNWs arises due to ionic or particulate effects, or both, are poorly understood. Here, a combination of elemental quantification, 3D tomography, analytical transmission electron microscopy (TEM), and confocal microscopy were employed to monitor the uptake, intracellular Ag+ availability, and processing of AgNWs of two different lengths (1 and 10 μm) inside human monocyte-derived macrophages (HMMs). Using AgNO3 and spherical silver nanoparticles (AgNPs) as a comparison, the amount of total bioavailable/intracellular Ag highly correlated to the cytotoxicity of AgNWs. The 10 μm AgNWs were completely internalized in HMMs, with numerous lysosomal vesicles observed in close vicinity to the AgNWs. Following cellular uptake, AgNWs dissolved and transformed intracellularly, with precipitation of AgCl as well as Ag2S. These transformation processes were likely due to AgNW degradation in the acidic environment of lysosomes, leading to the release of Ag+ ions that rapidly react with Cl– and SH– species of the cell microenvironment. Our data suggest that, in HMMs, not only frustrated phagocytosis but also the extent of intracellular uptake and dissolution of AgNWs dictates their cytotoxicity.

Journal article

Theodorou I, Jawad Z, Jiang Q, Aboagye E, Porter A, Ryan M, Xie Fet al., 2017, Gold Nanostar Substrates for Metal Enhanced Fluorescence through the First and Second Near-Infrared Windows, Chemistry of Materials, Vol: 29, Pages: 6916-6926, ISSN: 1520-5002

Gold nanostars (AuNSs) are receiving increasing attention for their potential applications in bionanotechnology because of their unique optical properties related to their complex branched morphology. Their sharp features allow strong localized surface plasmon resonances, tunable in the near-infrared (NIR) region, and large enhancements of local electromagnetic fields. Here, the application of AuNSs in metal-enhanced fluorescence (MEF) in the NIR and second NIR (NIR-II) biological windows is explored for the first time. NIR/NIR-II fluorophores are incorporated onto monolayers of AuNSs with tunable plasmonic responses. Over 320-fold fluorescence enhancement is achieved in the NIR, confirming that AuNS substrates are promising NIR-MEF platforms for the development of ultrasensitive biosensing applications. Using fluorescence lifetime measurements to semiquantitatively deconvolute the excitation enhancement from emission enhancement, as well as modeling to simulate the electric field enhancement, we show that a combination of enhanced excitation and an increased radiative decay rate, accompanied by an increase in the quantum yield, contribute to the observed large enhancement. AuNSs with different morphological features exhibit significantly different excitation enhancements, indicating the important role of the particle morphology on the magnitude of electromagnetic field enhancement and the resulting enhancement factor. Importantly, enhancement factors of up to 50-fold are also achieved in the NIR-II region, suggesting that this system holds promise for the future development of bright probes for NIR/NIR-II biosensing and bioimaging.

Journal article

Qin H, Shamso A, Centeno A, Theodorou I, Mihai A, Ryan M, Xie Fet al., 2017, Enhancing the upconversion photoluminescence of hexagonal phase NaYF4:Yb3+, Er3+ nanoparticles by mesoporous gold films, Physical Chemistry Chemical Physics, Vol: 19, Pages: 19159-19167, ISSN: 1463-9076

Efficient enhancement of photoluminescence in rare-earth activated upconversion materials is of great significance for their practical applications in various fields. In this work{,} three-dimensional mesoporous gold films were fabricated by a low-cost and facile dealloying approach to improve the upconversion photoluminescence efficiency. The mesoporous Au films exhibit good chemical stability{,} large-area uniformity and abundant distribution of porous nanospaces. Varying the time of the dealloying process leads to modification of pore size distribution{,} surface roughness and residual Ag content{,} resulting in effective tuning the wavelength of the broadband localized surface plasmon resonance (LSPR). Enhancement factors were identified to be a function of the dealloying time. With the optimized upconversion photoluminescence enhancement a 41-fold increase was achieved with the mesoporous gold substrate which had been dealloyed for 8 days. These results pave the way to overcome the limitation of poor upconversion efficiency for widespread practical applications in life sciences and energy applications.

Journal article

Pramana SS, Cavallaro A, Qi J, Nicklin CL, Ryan MP, Skinner SJet al., 2017, Understanding surface structure and chemistry of single crystal lanthanum aluminate, Scientific Reports, Vol: 7, ISSN: 2045-2322

The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600°C) and chamber pressure of 10-10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10-6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

Journal article

Gonzalez Carter DA, Leo BF, Ruenraroengsak P, Chen S, Goode A, Theodorou I, Chung KF, Carzaniga R, Shaffer M, Dexter D, Ryan M, Porter Aet al., 2017, Silver nanoparticles reduce brain inflammation and related neurotoxicity through induction of H2S-synthesizing enzymes, Scientific Reports, Vol: 7, ISSN: 2045-2322

Silver nanoparticles (AgNP) are known to penetrate into the brain and cause neuronal death. However, there is a paucity in studies examining the effect of AgNP on the resident immune cells of the brain, microglia. Given microglia are implicated in neurodegenerative disorders such as Parkinson’s disease (PD), it is important to examine how AgNPs affect microglial inflammation to fully assess AgNP neurotoxicity. In addition, understanding AgNP processing by microglia will allow better prediction of their long term bioreactivity. In the present study, the in vitro uptake and intracellular transformation of citrate-capped AgNPs by microglia, as well as their effects on microglial inflammation and related neurotoxicity were examined. Analytical microscopy demonstrated internalization and dissolution of AgNPs within microglia and formation of non-reactive silver sulphide (Ag2S) on the surface of AgNPs. Furthermore, AgNP-treatment up-regulated microglial expression of the hydrogen sulphide (H2S)-synthesizing enzyme cystathionine-γ-lyase (CSE). In addition, AgNPs showed significant anti-inflammatory effects, reducing lipopolysaccharide (LPS)-stimulated ROS, nitric oxide and TNFα production, which translated into reduced microglial toxicity towards dopaminergic neurons. Hence, the present results indicate that intracellular Ag2S formation, resulting from CSE-mediated H2S production in microglia, sequesters Ag+ ions released from AgNPs, significantly limiting their toxicity, concomitantly reducing microglial inflammation and related neurotoxicity.

Journal article

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