Imperial College London

Prof Milo Shaffer

Faculty of Natural SciencesDepartment of Chemistry

Professor of Materials Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5825m.shaffer Website

 
 
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Assistant

 

Mr John Murrell +44 (0)20 7594 2845

 
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Location

 

M221Royal College of ScienceSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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262 results found

Garcia Trenco A, White E, Shaffer M, Williams CKet al., 2016, A one-step Cu/ZnO Quasi-Homogeneous Catalyst for DME Production from Syn-gas, Catalysis Science & Technology, Vol: 6, Pages: 4389-4397, ISSN: 2044-4753

A simple one-pot synthetic method allows the preparation of hybrid catalysts, based on colloidal Cu/ZnO nanoparticles(NPs), used for the liquid phase synthesis of DME from syngas. The method obviates the high temperature calcinations andpre-reduction treatments typically associated with such catalysts. The hybrid catalysts are applied under typicalindustrially relevant conditions. The nature of the hybrid catalysts, the influence of the acid component, mass ratiobetween components, and Cu/Zn composition are assessed. The best catalysts comprise a colloidal mixture of Cu/ZnONPs, as the methanol synthesis component, and -Al2O3, as the methanol dehydration component. These catalysts showhigh DME selectivity (65-70 %C). Interestingly, the activity (relative to Cu content) is up to three times higher than that forthe reference hybrid catalyst based on the commercial Cu/ZnO/Al2O3 methanol synthesis catalyst. The hybrid catalysts arestable for at least 20 h time-on-stream, not showing any significant sintering of the Cu0phase. Post-catalysis,TEM/EDXshows that the hybrid catalysts consist of Cu0and ZnO NPs with an average size of 5-7 nm with -Al2O3 particles in closeproximity.

Journal article

Blaker JJ, Anthony DB, Tang G, Shamsuddin SR, Kalinka G, Weinrich M, Abdolvand A, Shaffer MSP, Bismarck Aet al., 2016, Property and shape modulation of carbon fibers using lasers, ACS Applied Materials & Interfaces, Vol: 8, Pages: 16351-16358, ISSN: 1944-8244

An exciting challenge is to create unduloid-reinforcing fibers with tailored dimensions to produce synthetic composites with improved toughness and increased ductility. Continuous carbon fibers, the state-of-the-art reinforcement for structural composites, were modified via controlled laser irradiation to result in expanded outwardly tapered regions, as well as fibers with Q-tip (cotton-bud) end shapes. A pulsed laser treatment was used to introduce damage at the single carbon fiber level, creating expanded regions at predetermined points along the lengths of continuous carbon fibers, whilst maintaining much of their stiffness. The range of produced shapes was quantified and correlated to single fiber tensile properties. Mapped Raman spectroscopy was used to elucidate the local compositional and structural changes. Irradiation conditions were adjusted to create a swollen weakened region, such that fiber failure occurred in the laser treated region producing two fiber ends with outwardly tapered ends. Upon loading the tapered fibers allow for viscoelastic energy dissipation during fiber pull-out by enhanced friction as the fibers plough through a matrix. In these tapered fibers, diameters were locally increased up to 53%, forming outward taper angles of up to 1.8°. The tensile strength and strain to failure of the modified fibers were significantly reduced, by 75% and 55%, respectively, ensuring localization of the break in the expanded region; however, the fiber stiffness was only reduced by 17%. Using harsher irradiation conditions, carbon fibers were completely cut, resulting in cotton-bud fiber end shapes. Single fiber pull-out tests performed using these fibers revealed a 6.75 fold increase in work of pull-out compared to pristine carbon fibers. Controlled laser irradiation is a route to modify the shape of continuous carbon fibers along their lengths, as well as to cut them into controlled lengths leaving tapered or cotton-bud shapes.

Journal article

Liberti E, Menzel R, Shaffer MS, McComb DWet al., 2016, Probing the size dependence on the optical modes of anatase nanoplatelets using STEM-EELS, Nanoscale, Vol: 8, Pages: 9727-9735, ISSN: 2040-3372

Anatase titania nanoplatelets with predominantly exposed {001} facets have been reported to have enhanced catalytic properties in comparison with bulk anatase. To understand their unusual behaviour, it is essential to fully characterize their electronic and optical properties at the nanometer scale. One way of assessing these fundamental properties is to study the dielectric function. Valence electron energy-loss spectroscopy (EELS) performed using a scanning transmission electron microscope (STEM) is the only analytical method that can probe the complex dielectric function with both high energy (<100 meV) and high spatial (<1 nm) resolution. By correlating experimental STEM-EELS data with simulations based on semi-classical dielectric theory, the dielectric response of thin (<5 nm) anatase nanoplatelets was found to be largely dominated by characteristic (optical) surface modes, which are linked to surface plasmon modes of anatase. For platelets less than 10 nm thick, the frequency of these optical modes varies according to their thickness. This unique optical behaviour prompts the enhancement of light absorption in the ultraviolet regime. Finally, the effect of finite size on the dielectric signal is gradually lost by stacking consistently two or more platelets in a specific crystal orientation, and eventually suppressed for large stacks of platelets.

Journal article

Menzel R, Iruretagoyena D, Wang Y, Bawaked SM, Mokhtar M, Al-Thabaiti SA, Basahel SN, Shaffer MSPet al., 2016, Graphene oxide/mixed metal oxide hybrid materials for enhanced adsorption desulfurization of liquid hydrocarbon fuels, Fuel, Vol: 181, Pages: 531-536, ISSN: 0016-2361

A series of mixed metal oxides (MMOs) adsorbents (MgAl-, CuAl- and CoAl-MMOs) were supported on graphene oxide (GO) through in-situ precipitation of layered double hydroxides (LDHs) onto exfoliated GO, followed by thermal conversion. The study shows that GO is an excellent support for the LDH-derived MMOs due to matching geometry and charge complementarity, resulting in a strong hybrid effect, evidenced by significantly enhanced adsorption performance for the commercially important removal of heavy thiophenic compounds from hydrocarbons. Fundamental liquid-phase adsorption characteristics of the MMO/GO hybrids are quantified in terms of adsorption equilibrium isotherms, selectivity and adsorbent regenerability. Upon incorporation of as little as 5 wt% GO into the MMO material, the organosulfur uptake was increased by up to 170%, the recycling stability was markedly improved and pronounced selectivity for thiophenic organosulfurs over sulfur-free aromatic hydrocarbons was observed.

Journal article

Herceg TM, Abidin MSZ, Greenhalgh ES, Shaffer MSP, Bismarck Aet al., 2016, Thermosetting hierarchical composites with high carbon nanotube loadings: En route to high performance, Composites Science and Technology, Vol: 127, Pages: 134-141, ISSN: 0266-3538

A wet powder impregnation route to manufacture carbon fibre reinforced thermoplastic composites was adapted to accommodate thermosetting matrices reinforced with high fractions (20 wt%/13.6 vol%) of multiwalled carbon nanotubes (CNTs). The produced carbon fibre prepregs were consolidated into laminates with fibre volume fractions of 50–58% and up to 6.1 vol% CNTs. Microscopic imaging confirmed successful consolidation at intermediate CNT loadings, but some voidage at the highest CNT loading due to the highly viscoelastic uncured matrix. Nonetheless, through-thickness electrical conductivity and Mode I interlaminar fracture toughness were enhanced by as much as 152% and 24% to unprecedented values of σ = 53 S m−1 and GIC = 840 J m−2, respectively. Fractographic characterisation indicated that crack deflection was the mechanism responsible for the improved fracture toughness. The material properties were shown to be strongly dependent on the microstructure of the matrix.

Journal article

Sweeney S, Leo BF, Chen S, Abraham-Thomas N, Thorley AJ, Gow A, Schwander S, Zhang JJ, Shaffer MS, Chung KF, Ryan MP, Porter AE, Tetley TDet al., 2016, Pulmonary surfactant mitigates silver nanoparticle toxicity in human alveolar type-I-like epithelial cells., Colloids and Surfaces B - Biointerfaces, Vol: 145, Pages: 167-175, ISSN: 1873-4367

Accompanying increased commercial applications and production of silver nanomaterials is an increased probability of human exposure, with inhalation a key route. Nanomaterials that deposit in the pulmonary alveolar region following inhalation will interact firstly with pulmonary surfactant before they interact with the alveolar epithelium. It is therefore critical to understand the effects of human pulmonary surfactant when evaluating the inhalation toxicity of silver nanoparticles. In this study, we evaluated the toxicity of AgNPs on human alveolar type-I-like epithelial (TT1) cells in the absence and presence of Curosurf(®) (a natural pulmonary surfactant substitute), hypothesising that the pulmonary surfactant would act to modify toxicity. We demonstrated that 20nm citrate-capped AgNPs induce toxicity in human alveolar type I-like epithelial cells and, in agreement with our hypothesis, that pulmonary surfactant acts to mitigate this toxicity, possibly through reducing AgNP dissolution into cytotoxic Ag(+) ions. For example, IL-6 and IL-8 release by TT1 cells significantly increased 10.7- and 35-fold, respectively (P<0.01), 24h after treatment with 25μg/ml AgNPs. In contrast, following pre-incubation of AgNPs with Curosurf(®), this effect was almost completely abolished. We further determined that the mechanism of this toxicity is likely associated with Ag(+) ion release and lysosomal disruption, but not with increased reactive oxygen species generation. This study provides a critical understanding of the toxicity of AgNPs in target human alveolar type-I-like epithelial cells and the role of pulmonary surfactant in mitigating this toxicity. The observations reported have important implications for the manufacture and application of AgNPs, in particular for applications involving use of aerosolised AgNPs.

Journal article

Ruenraromgsak P, Chen S, Hu S, Melbourne J, Sweeney S, Thorley AJ, Skepper JN, Shaffer MSP, Tetley TD, Porter AEet al., 2016, Translocation of functionalized multi-walled carbon nanotubes across human pulmonary alveolar epithelium: dominant role of epithelial type 1 cells, ACS Nano, Vol: 10, Pages: 5070-5085, ISSN: 1936-086X

Uptake and translocation of short functionalized multi-walled carbon nanotubes (short-fMWCNTs) through the pulmonary respiratory epithelial barrier depend on physicochemical property and cell type. Two monoculture models, immortalized human alveolar epithelial type 1 (TT1) cells and primary human alveolar epithelial type 2 cells (AT2), which constitute the alveolar epithelial barrier, were employed to investigate the uptake and transport of 300 and 700 nm in length, poly(4-vinylpyridine)-functionalized, multi-walled carbon nanotubes (p(4VP)-MWCNTs) using quantitative imaging and spectroscopy techniques. The p(4VP)-MWCNT exhibited no toxicity on TT1 and AT2 cells, but significantly decreased barrier integrity (*p < 0.01). Uptake of p(4VP)-MWCNTs was observed in 70% of TT1 cells, correlating with compromised barrier integrity and basolateral p(4VP)-MWCNT translocation. There was a small but significantly greater uptake of 300 nm p(4VP)-MWCNTs than 700 nm p(4VP)-MWCNTs by TT1 cells. Up to 3% of both the 300 and 700 nm p(4VP)-MWCNTs reach the basal chamber; this relatively low amount arose because the supporting transwell membrane minimized the amount of p(4VP)-MWCNT translocating to the basal chamber, seen trapped between the basolateral cell membrane and the membrane. Only 8% of AT2 cells internalized p(4VP)-MWCNT, accounting for 17% of applied p(4VP)-MWCNT), with transient effects on barrier function, which initially fell then returned to normal; there was no MWCNT basolateral translocation. The transport rate was MWCNT length modulated. The comparatively lower p(4VP)-MWCNT uptake by AT2 cells is proposed to reflect a primary barrier effect of type 2 cell secretions and the functional differences between the type 1 and type 2 alveolar epithelial cells.

Journal article

Leese HS, Govada L, Saridakis E, Khurshid S, Menzel R, Morishita T, Clancy ARJ, White E, Chayen NE, Shaffer MSPet al., 2016, Reductively PEGylated carbon nanomaterials andtheir use to nucleate 3D protein crystals:a comparison of dimensionality, Chemical Science, Vol: 7, Pages: 2916-2923, ISSN: 2041-6539

A range of carbon nanomaterials, with varying dimensionality, were dispersed by a non-damaging and versatile chemical reduction route, and subsequently grafted by reaction with methoxy polyethylene glycol (mPEG) monobromides. The use of carbon nanomaterials with different geometries provides both a systematic comparison of surface modification chemistry and the opportunity to study factors affecting specific applications. Multi-walled carbon nanotubes, single-walled carbon nanotubes, graphite nanoplatelets, exfoliated few layer graphite and carbon black were functionalized with mPEG-Br, yielding grafting ratios relative to the nanocarbon framework between ca. 7 and 135 wt%; the products were characterised by Raman spectroscopy, TGA-MS, and electron microscopy. The functionalized materials were tested as nucleants by subjecting them to rigorous protein crystallization studies. Sparsely functionalized flat sheet geometries proved exceptionally effective at inducing crystallization of six proteins. This new class of nucleant, based on PEG grafted graphene-related materials, can be widely applied to promote the growth of 3D crystals suitable for X-ray crystallography. The association of the protein ferritin with functionalized exfoliated few layer graphite was directly visualized by transmission electron microscopy, illustrating the formation of ordered clusters of protein molecules critical to successful nucleation.

Journal article

Ferguson A, Khan U, Walsh M, Lee KY, Bismarck A, Shaffer MS, Coleman JN, Bergin SDet al., 2016, Understanding the dispersion and assembly of bacterial cellulose in organic solvents, Biomacromolecules, Vol: 17, Pages: 1845-1853, ISSN: 1526-4602

The constituent nanofibrils of bacterial cellulose are of interest to many researchers because of their purity and excellent mechanical properties. Mechanisms to disrupt the network structure of bacterial cellulose (BC) to isolate bacterial cellulose nanofibrils (BCN) are limited. This work focuses on liquid-phase dispersions of BCN in a range of organic solvents. It builds on work to disperse similarly intractable nanomaterials, such as single-walled carbon nanotubes, where optimum dispersion is seen for solvents whose surface energies are close to the surface energy of the nanomaterial; bacterial cellulose is shown to disperse in a similar fashion. Inverse gas chromatography was used to determine the surface energy of bacterial cellulose, under relevant conditions, by quantifying the surface heterogeneity of the material as a function of coverage. Films of pure BCN were prepared from dispersions in a range of solvents; the extent of BCN exfoliation is shown to have a strong effect on the mechanical properties of BC films and to fit models based on the volumetric density of nanofibril junctions. Such control offers new routes to producing robust cellulose films of bacterial cellulose nanofibrils.

Journal article

Shaffer MSP, Diba M, Fam DWH, Boccaccini Aet al., 2016, Electrophoretic deposition of graphene-related materials: A review of the fundamentals, Progress in Materials Science, Vol: 82, Pages: 83-117, ISSN: 1873-2208

The Electrophoretic Deposition (EPD) of graphene-related materials (GRMs) is an attractive strategy for a wide range of applications. This review paper provides an overview of the fundamentals and specific technical aspects of this approach, highlighting its advantages and limitations, in particular considering the issues that arise specifically from the behaviour and dimensionality of GRMs. Since obtaining a stable dispersion of charged particles is a pre-requisite for successful EPD, the strategies for suspending GRMs in different media are discussed, along with the resulting influence on the deposited film. Most importantly, the kinetics involved in the EPD of GRMs and the factors that cause deviation from linearity in Hamaker’s Law are reviewed. Side reactions often influence both the efficiency of deposition and the nature of the deposited material; examples include the reduction of graphene oxide (GO) and related materials, as well as the decomposition of the suspension medium at high potentials. The microstructural characteristics of GRM deposits, including their degree of reduction and orientation, strongly influence their performance in their intended function. These factors will also determine, to a large extent, the commercial potential of this technique for applications involving GRMs, and are therefore discussed here.

Journal article

De Marco MDM, Markoulidis F, Menzel R, Bawaked S, Mokhtar M, Al-Thabaiti S, Basahel S, Shaffer Met al., 2016, Cross-linked single-walled carbon nanotube aerogel electrodes via reductive coupling chemistry, Journal of Materials Chemistry A, Vol: 4, Pages: 5385-5389, ISSN: 2050-7496

Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties.

Journal article

Herceg TM, Yoon S-H, Abidin MSZ, Greenhalgh ES, Bismarck A, Shaffer MSPet al., 2016, Thermosetting nanocomposites with high carbon nanotube loadings processed by a scalable powder based method, Composites Science and Technology, Vol: 127, Pages: 62-70, ISSN: 0266-3538

A powder based processing route was developed to allow manufacturing of thermosettingnanocomposites with high (20 wt%) carbon nanotube (CNT) loading fractions. Adaptation ofhigh shear mixing methods, as used in thermoplastic processing, ensured that the CNTs werewell distributed and dispersed even at the highest loadings. By minimising flow distances,compression moulding of powders ensured that the CNTs did not agglomerate duringconsolidation, and yielded a percolated CNT network in a nanocomposite with excellentelectrical and thermal conductivities of 67 S m-1and 0.77 W m-1 K-1, respectively. Unusually,the CNTs provided effective mechanical reinforcement at even the highest loadings;embrittlement is minimised by avoiding large scale inhomogeneities and the maximummeasured Young’s modulus (5.4 GPa) and yield strength (90 MPa) could make thenanocomposite an attractive matrix for continuous fibre composites. The macromechanicalmeasurements were interpolated using micromechanical models that were previouslysuccessfully applied at the nanoscale.

Journal article

Chayen N, shaffer, govada, Khurshid, Kassen, Leese H S, Hu S, Menzel, Chain B, Saridakiset al., 2016, Exploring Carbon Nanomaterial Diversity for Nucleation of Protein Crystals, Scientific Reports, Vol: 6, ISSN: 2045-2322

Controlling crystal nucleation is a crucial step in obtaining high quality protein crystals for structure determination by X-ray crystallography. Carbon nanomaterials (CNMs) including carbon nanotubes, graphene oxide, and carbon black provide a range of surface topographies, porosities and length scales; functionalisation with two different approaches, gas phase radical grafting and liquid phase reductive grafting, provide routes to a range of oligomer functionalised products. These grafted materials, combined with a range of controls, were used in a large-scale assessment of the effectiveness for protein crystal nucleation of 20 different carbon nanomaterials on five proteins. This study has allowed a direct comparison of the key characteristics of carbon-based nucleants: appropriate surface chemistry, porosity and/or roughness are required. The most effective solid system tested in this study, carbon black nanoparticles functionalised with poly(ethylene glycol) methyl ether of mean molecular weight 5000, provides a novel highly effective nucleant, that was able to induce crystal nucleation of four out of the five proteins tested at metastable conditions.

Journal article

Woodward RT, Fam DWH, Anthony DB, Hong J, McDonald TO, Petit C, Shaffer MSP, Bismarck Aet al., 2016, Hierarchically porous carbon foams from pickering high internal phase emulsions, Carbon, Vol: 101, Pages: 253-260, ISSN: 0008-6223

Carbon foams were produced from a macroporous poly(divinylbenzene) (poly(DVB) precursor, synthesized by polymerizing the continuous but minority phase of water-in-oil high internal phase emulsions (HIPEs) stabilized by molecular and/or particulate emulsifiers. Both permeable and non-permeable hierarchically porous carbon foams, or ‘carboHIPEs’, were prepared by carbonization of the resulting macroporous polymers at 800 °C. The carbon yields were as high as 26 wt.% of the original polymer. CarboHIPEs retain the pore structure of the macroporous polymer precursor, but with surface areas of up to 505 m2/g and excellent electrical conductivities of 81 S/m. Contrary to some previous reports, the method does not require further modification, such as sulfonation or additional crosslinking of the polyHIPE prior to carbonization, due to the inherently crosslinked structure of poly(DVB). The use of a pourable, aqueous emulsion-template enables simple moulding, minimises waste and avoids the strong acid treatments used to remove many conventional solid-templates. The retention of the macroporous structure is coupled with the introduction of micropores during carbonization, producing hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.

Journal article

Anthony DB, Shaffer MSP, 2016, Process for producing carbon-nanotube grafted substrate, WO 2016009207 A1

The present invention relates to a process for producing a carbon nanotube-grafted substrate, the process comprising: providing a substrate having catalytic material deposited thereon; and synthesising carbon nanotubes on the substrate by a chemical vapour deposition process in a reaction chamber; characterised in that the process comprises providing a counter electrode, applying a potential difference to the substrate in relation to the counter electrode and maintaining the potential difference of the substrate in relation to the counter electrode during the chemical vapour deposition process.

Patent

Clancy ARJ, Bayazit M, shaffer M, Hodge S, Chen S, Menzelet al., 2015, Carbon nanotube anions for the preparation of gold nanoparticle-nanocarbon hybrids, Chemical Communications, Vol: 52, Pages: 1934-1937, ISSN: 1364-548X

Gold nanoparticles (AuNPs) can be evenly deposited on singlewalledcarbon nanotubes (SWCNTs) via the reduction of the highlystable complex, chloro(triphenylphosphine) gold(I), with SWCNTanions (‘nanotubides’). This methodology highlights the unusualchemistry of nanotubides and provides a blueprint for thegeneration of many other hybrid nanomaterials.

Journal article

De Luca F, Menzel R, Blaker JJ, Birkbeck J, Bismarck A, Shaffer MSPet al., 2015, Nacre-nanomimetics: Strong, Stiff, and Plastic, ACS APPLIED MATERIALS & INTERFACES, Vol: 7, Pages: 26783-26791, ISSN: 1944-8244

Journal article

Iruretagoyena D, Huang X, Shaffer MSP, Chadwick Det al., 2015, Influence of Alkali Metals (Na, K, and Cs) on CO2 Adsorption by Layered Double Oxides Supported on Graphene Oxide, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 54, Pages: 11610-11618, ISSN: 0888-5885

Journal article

Yau H, Shaffer MSP, 2015, Sonochemical Degradation of N-Methylpyrrolidone and Its Influence on Single Walled Carbon Nanotube Dispersion, Chemical Communications, Vol: 51, Pages: 16621-16624, ISSN: 1364-548X

Sonicating pure N-methyl pyrrolidone (NMP) rapidly produces contaminating organic nanoparticles, at increasing concentration with time, as investigated by AFM, as well as UV-vis, IR and NMR spectroscopies. The contamination issue affects nanotube, and likely other nanomaterial, dispersions processed by sonication in organic solvents.

Journal article

Javaid A, Ho KKC, Bismarck A, Steinke JHG, Shaffer MSP, Greenhalgh ESet al., 2015, Carbon fibre-reinforced poly(ethylene glycol) diglycidylether based multifunctional structural supercapacitor composites for electrical energy storage applications, Journal of Composite Materials, Vol: 50, Pages: 2155-2163, ISSN: 1530-793X

Journal article

Goode AE, Gonzalez Carter DA, Motskin M, Pienaar IS, Chen S, Hu S, Ruenraroengsak P, Ryan M, Shaffer MSP, Dexter DT, Porter AEet al., 2015, High resolution and dynamic imaging of biopersistence and bioreactivity of extra and intracellular MWNTs exposed to microglial cells, Biomaterials, Vol: 70, Pages: 57-70, ISSN: 1878-5905

Multi-walled carbon nanotubes (MWNTs) are increasingly being developed both as neuro-therapeutic drug delivery systems to the brain and as neural scaffolds to drive tissue regeneration across lesion sites. MWNTs with different degrees of acid oxidation may have different bioreactivities and propensities to aggregate in the extracellular environment, and both individualised and aggregated MWNTs may be expected to be found in the brain. Before practical application, it is vital to understand how both aggregates and individual MWNTs will interact with local phagocytic immune cells, the microglia, and ultimately to determine their biopersistence in the brain. The processing of extra- and intracellular MWNTs (both pristine and when acid oxidised) by microglia was characterised across multiple length scales by correlating a range of dynamic, quantitative and multi-scale techniques, including: UV-vis spectroscopy, light microscopy, focussed ion beam scanning electron microscopy and transmission electron microscopy. Dynamic, live cell imaging revealed the ability of microglia to break apart and internalise micron-sized extracellular agglomerates of acid oxidised MWNT, but not pristine MWNTs. The total amount of MWNTs internalised by, or strongly bound to, microglia was quantified as a function of time. Neither the significant uptake of oxidised MWNTs, nor the incomplete uptake of pristine MWNTs affected microglial viability, pro-inflammatory cytokine release or nitric oxide production. However, after 24 hrs exposure to pristine MWNTs, a significant increase in the production of reactive oxygen species was observed. Small aggregates and individualised oxidised MWNTs were present in the cytoplasm and vesicles, including within multilaminar bodies, after 72 hours. Some evidence of morphological damage to oxidised MWNT structure was observed including highly disordered graphitic structures, suggesting possible biodegradation. This work demonstrates the utility of dynamic, quant

Journal article

Clancy AJ, Melbourne J, Shaffer MSP, 2015, A one-step route to solubilised, purified or functionalised single-walled carbon nanotubes, Journal of Materials Chemistry A, Vol: 3, Pages: 16708-16715, ISSN: 2050-7496

Reductive dissolution is a promising processing route for single walled carbon nanotubes (SWCNTs) thatavoids the damage caused by ultrasonication and aggressive oxidation whilst simultaneously allowingaccess to a wealth of SWCNT functionalisation reactions. Here, reductive dissolution has been simplifiedto a single one-pot reaction through the use of sodium naphthalide in dimethylacetamide allowingdirect synthesis of SWCNT Na+ solutions. Gram quantities of SWCNTs can be dissolved at concentrationsover 2 mg mL 1. These reduced SWCNT solutions can easily be functionalised through the addition ofalkyl halides; reducing steric bulk of the grafting moiety and increasing polarisability of the leaving groupincreases the extent of functionalisation. An optimised absolute sodium concentration of 25 mM isshown to be more important than carbon to metal ratio in determining the maximum degree offunctionalisation. This novel dissolution system can be modified for use as a non-destructive purificationroute for raw SWCNT powder by adjusting the degree of charging to dissolve carbonaceous impurities,catalyst particles and defective material, before processing the remaining SWCNTs.

Journal article

Iruretagoyena D, Shaffer MSP, Chadwick D, 2015, Layered Double Oxides Supported on Graphene Oxide for CO2 Adsorption: Effect of Support and Residual Sodium, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 54, Pages: 6781-6792, ISSN: 0888-5885

Journal article

Theodorou IG, Botelho D, Schwander S, Zhang J, Chung KF, Tetley TD, Shaffer MSP, Gow A, Ryan MP, Porter AEet al., 2015, Static and Dynamic Microscopy of the Chemical Stability and Aggregation State of Silver Nanowires in Components of Murine Pulmonary Surfactant, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 49, Pages: 8048-8056, ISSN: 0013-936X

Journal article

Sweeney S, Theodorou IG, Zambianchi M, Chen S, Gow A, Schwander S, Zhang JJ, Chung KF, Shaffer MS, Ryan MP, Porter AE, Tetley TDet al., 2015, Silver nanowire interactions with primary human alveolar type-II epithelial cell secretions: contrasting bioreactivity with human alveolar type-I and type-II epithelial cells., Nanoscale, Vol: 7, Pages: 10398-10409, ISSN: 2040-3372

Inhaled nanoparticles have a high deposition rate in the alveolar units of the deep lung. The alveolar epithelium is composed of type-I and type-II epithelial cells (ATI and ATII respectively) and is bathed in pulmonary surfactant. The effect of native human ATII cell secretions on nanoparticle toxicity is not known. We investigated the cellular uptake and toxicity of silver nanowires (AgNWs; 70 nm diameter, 1.5 μm length) with human ATI-like cells (TT1), in the absence or presence of Curosurf® (a natural porcine pulmonary surfactant with a low amount of protein) or harvested primary human ATII cell secretions (HAS; containing both the complete lipid as well as the full protein complement of human pulmonary surfactant i.e. SP-A, SP-B, SP-C and SP-D). We hypothesised that Curosurf® or HAS would confer improved protection for TT1 cells, limiting the toxicity of AgNWs. In agreement with our hypothesis, HAS reduced the inflammatory and reactive oxygen species (ROS)-generating potential of AgNWs with exposed TT1 cells. For example, IL-8 release and ROS generation was reduced by 38% and 29%, respectively, resulting in similar levels to that of the non-treated controls. However in contrast to our hypothesis, Curosurf® had no effect. We found a significant reduction in AgNW uptake by TT1 cells in the presence of HAS but not Curosurf. Furthermore, we show that the SP-A and SP-D are likely to be involved in this process as they were found to be specifically bound to the AgNWs. While ATI cells appear to be protected by HAS, evidence suggested that ATII cells, despite no uptake, were vulnerable to AgNW exposure (indicated by increased IL-8 release and ROS generation and decreased intracellular SP-A levels one day post-exposure). This study provides unique findings that may be important for the study of lung epithelial-endothelial translocation of nanoparticles in general and associated toxicity within the alveolar unit.

Journal article

Melbourne J, Clancy A, Seiffert J, Skepper J, Tetley TD, Shaffer MS, Porter Aet al., 2015, An investigation of the carbon nanotube - Lipid interface and its impact upon pulmonary surfactant lipid function., Biomaterials, Vol: 55, Pages: 24-32, ISSN: 1878-5905

Multiwalled carbon nanotubes (MWCNTs) are now synthesized on a large scale, increasing the risk of occupational inhalation. However, little is known of the MWCNT-pulmonary surfactant (PS) interface and its effect on PS functionality. The Langmuir-Blodgett trough was used to evaluate the impact of MWCNTs on fundamental properties of PS lipids which influence PS function, i.e. compression resistance and maximum obtainable pressure. Changes were found to be MWCNT length-dependent. 'Short' MWCNTs (1.1 μm, SD = 0.61) penetrated the lipid film, reducing the maximum interfacial film pressure by 10 mN/m (14%) in dipalmitoylphosphatidylcholine (DPPC) and PS, at an interfacial MWCNT-PS lipid mass ratio range of 50:1 to 1:1. 'Long' commercial MWCNTs (2.1 μm, SD = 1.2) caused compression resistance at the same mass loadings. 'Very long' MWCNTs (35 μm, SD = 19) sequestered DPPC and were squeezed out of the DPPC film. High resolution transmission electron microscopy revealed that all MWCNT morphologies formed DPPC coronas with ordered arrangements. These results provide insight into how nanoparticle aspect ratio affects the interaction mechanisms with PS, in its near-native state at the air-water interface.

Journal article

Brown NJ, Garcia-Trenco A, Weiner J, White ER, Allinson M, Chen Y, Wells PP, Gibson EK, Hellgardt K, Shaffer MSP, Williams CKet al., 2015, From Organometallic Zinc and Copper Complexes to Highly Active Colloidal Catalysts for the Conversion of CO2 to Methanol, ACS Catalysis, Vol: 5, Pages: 2895-2902, ISSN: 2155-5435

A series of zinc oxide and copper(0) colloidal nanocatalysts, produced by a one-pot synthesis, are shown to catalyze the hydrogenation of carbon dioxide to methanol. The catalysts are produced by the reaction between diethyl zinc and bis(carboxylato/phosphinato)copper(II) precursors. The reaction leads to the formation of a precatalyst solution, characterized using various spectroscopic (NMR, UV–vis spectroscopy) and X-ray diffraction/absorption (powder XRD, EXAFS, XANES) techniques. The combined characterization methods indicate that the precatalyst solution contains copper(0) nanoparticles and a mixture of diethyl zinc and an ethyl zinc stearate cluster compound [Et4Zn5(stearate)6]. The catalysts are applied, at 523 K with a 50 bar total pressure of a 3:1 mixture of H2/CO2, in the solution phase, quasi-homogeneous, hydrogenation of carbon dioxide, and they show high activities (>55 mmol/gZnOCu/h of methanol). The postreaction catalyst solution is characterized using a range of spectroscopies, X-ray diffraction techniques, and transmission electron microscopy (TEM). These analyses show the formation of a mixture of zinc oxide nanoparticles, of size 2–7 nm and small copper nanoparticles. The catalyst composition can be easily adjusted, and the influence of the relative loadings of ZnO/Cu, the precursor complexes and the total catalyst concentration on the catalytic activity are all investigated. The optimum system, comprising a 55:45 loading of ZnO/Cu, shows equivalent activity to a commercial, activated methanol synthesis catalyst. These findings indicate that using diethyl zinc to reduce copper precursors in situ leads to catalysts with excellent activities for the production of methanol from carbon dioxide.

Journal article

Marchetti M, Shaffer MSP, Zambianchi M, Chen S, Superti F, Schwander S, Gow A, Zhang JJ, Chung KF, Ryan MP, Porter AE, Tetley TDet al., 2015, Adsorption of surfactant protein D from human respiratory secretions by carbon nanotubes and polystyrene nanoparticles depends on nanomaterial surface modification and size, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, Vol: 370, ISSN: 0962-8436

Journal article

Chen S, Goode AE, Skepper JN, Thorley AJ, Seiffert JM, Chung KF, Tetley TD, Shaffer MSP, Ryan MP, Porter AEet al., 2015, Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments, Journal of Microscopy, Vol: 261, Pages: 157-166, ISSN: 1365-2818

Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinized. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data. Lay description: With increasing commercialization of silver nanomaterials (AgNMs) comes a concomitant need to understand occupational health, public safety and environmental implications of these materials. Nanoscale studies of the complex bio-nano interface lie at the heart of technical challenges. Despite numerous reports, there is no consensus regarding biological mechanisms enacted by AgNMs. Powerful new electron microscopy techniques can be used to visualize the interaction of the AgNMs with tissues. However, it is extremely difficult to

Journal article

Menzel R, Barg S, Miranda M, Anthony DB, Bawaked SM, Mokhtar M, Al-Thabaiti SA, Basahel SN, Saiz E, Shaffer MSPet al., 2015, Joule Heating Characteristics of Emulsion-Templated Graphene Aerogels, ADVANCED FUNCTIONAL MATERIALS, Vol: 25, Pages: 28-35, ISSN: 1616-301X

Journal article

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