Imperial College London

Prof Milo Shaffer

Faculty of Natural SciencesDepartment of Chemistry

Professor of Materials Chemistry
 
 
 
//

Contact

 

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

 
 
//

Assistant

 

Mr John Murrell +44 (0)20 7594 2845

 
//

Location

 

401BMolecular Sciences Research HubWhite City Campus

//

Summary

 

Publications

Publication Type
Year
to

301 results found

Govada L, Rubio N, Saridakis E, Balaskandan K, Leese HS, Li Y, Wang B, Shaffer MSP, Chayen Net al., 2022, Graphene-based nucleants for protein crystallization, Advanced Functional Materials, Vol: 32, ISSN: 1616-301X

Protein crystallization remains a major bottleneck for the determination of high resolution structures. Nucleants can accelerate the process but should ideally be compatible with high throughput robotic screening. Polyethylene glycol grafted (PEGylated) graphenes can be stabilized in water providing dispensable, nucleant systems. Two graphitic feedstocks are exfoliated and functionalized with PEG using a non-destructive, scalable, chemical reduction method, delivering good water dispersibility (80 and 750 µg mL−1 for large and small layers, respectively). The wide utility of these nucleants has been established across five proteins and three different screens, each of 96 conditions, demonstrating greater effectiveness of the dispersed PEGylated graphenes. Smaller numbers of larger, more crystalline flakes consistently act as better protein nucleants. The delivered nucleant concentration is optimized (0.1 mg mL−1 in the condition), and the performance benchmarked against existing state of the art, molecularly imprinted polymer nucleants. Strikingly, graphene nucleants are effective even when decreasing both the nucleant and protein concentration to unusually low concentrations. The set-up to scale-up nucleant production to liter volumes can provide sufficient material for wide implementation. Together with the optimized crystallization conditions, the results are a step forward toward practical synthesis of a readily accessible “universal” nucleant.

Journal article

Ishfaq A, Nguyen S, Greenhalgh ES, Shaffer MSP, Kucernak ARJ, Asp LE, Zenkert D, Linde Pet al., 2022, Multifunctional design, feasibility and requirements for structural power composites in future electric air taxis, Journal of Composite Materials, ISSN: 0021-9983

This study investigates the viability of implementing multifunctional structural power composites in a four-seater air taxi, the CityAirbus. For a given specific energy of the power source, the cruise endurance can be approximately doubled by using structural power composites as opposed to conventional batteries. Replacing all the eligible composite mass and batteries with structural power composites can reduce the CityAirbus weight by 25%. To achieve the current design performance, the minimum required elastic modulus, strength, specific energy and power for the structural power composite are 54 GPa, 203 MPa, 74 Wh/kg and 376 W/kg, respectively: current state-of-the-art structural power composites are now approaching this level of performance. Hence, structural power composites are considered feasible for adoption in the urban air mobility sector and have the potential to improve endurance and facilitate commercialization. This paper also discusses several key challenges that must be addressed to realize the adoption of structural power composites in future electric air taxis.

Journal article

Rubio N, Suter T, Rana Z, Clancy AJ, Masuda S, Au H, Coulter G, Sirisinudomkit P, McMillan PF, Howard CA, Mattevi C, Brett DJL, Shaffer MSPet al., 2022, Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 10, Pages: 20121-20127, ISSN: 2050-7488

Journal article

Bayazit MK, Yau HC, Leese H, Lee WJ, Shaffer MSPet al., 2022, Mono-Acetylenes as New Crosslinkers for All-Carbon Living Charge Carbon Nanotubide Organogels, CHEMISTRYSELECT, Vol: 7, ISSN: 2365-6549

Journal article

Wang J, Anthony DB, Fuentes CA, De Luca HG, Zhang D, Bismarck A, Van Vuure AW, Shaffer MSP, Seveno Det al., 2022, Wettability of carbon nanotube-grafted carbon fibers and their interfacial properties in polypropylene thermoplastic composite, Composites Part A: Applied Science and Manufacturing, Vol: 159, Pages: 1-10, ISSN: 1359-835X

The interfacial properties of carbon fiber (CF) reinforced thermoplastic composites depend strongly on the wettability and surface characteristics of the reinforcing fibers, and their compatibility with a chosen matrix. The interface between conventional fibers and thermoplastic matrices is generally weak, due to a lack of specific chemical interaction, especially in the case of polyolefins. Carbon nanotube-grafted-carbon fibers (CNT-g-CF) are considered to be potential reinforcements as they provide additional mechanical interlocking. Commercial CFs were successfully grafted with nanotubes using a continuous, and hence scalable, CVD method. X-ray photoelectron spectroscopy, Wilhelmy wetting measurements, and scanning electron microscopy confirmed the successful grafting and resulting hydrophobic surface chemistry, dominated by van der Waals interactions. The grafted CNTs, with diameters and lengths around 10 nm and 140 nm respectively, were well suited to improve the overall wettability and interfacial shear strength (+53.4 %) of the CNT-g-CF in a polypropylene matrix when compared to as-received unsized CFs.

Journal article

Yousefi N, Fisher SJ, Burgstaller C, Shaffer MSP, Bismarck Aet al., 2022, Hierarchical carbon fibre composites incorporating high loadings of carbon nanotubes, Composites Science and Technology, Vol: 222, ISSN: 0266-3538

Uncured solid bisphenol-A epoxy resins containing up to 20 wt% carbon nanotubes (CNTs) were prepared usingmelt blending in a high shear mixer. The extrudate was ground to produce fine nanocomposite (NC) powders.This simple method produced well-dispersed NC, with CNT agglomerate sizes below 1 μm. Consolidated NCsdisplayed improved tensile moduli and strengths up to 3.3 GPa (+32%) and 78 MPa (+19%), respectively at 15wt% CNT, compared to the pure cured epoxy matrix. The relatively high Tg of 39 ◦C for the uncured NC powderssimplified the manufacture of composite prepregs using wet powder impregnation. The prepregs were laminatedinto hierarchical carbon fibre reinforced composites with improved through-thickness properties. Interlaminarshear strength improved for intermediate CNT loadings in the matrix up to 65 MPa (10 wt% CNT, +19%) butdecreased at higher concentrations. Compression moduli remained constant irrespectively of CNT loading butcompression strength increased with a CNT loading of 2.5 wt% to 772 MPa (+31%). The mechanical propertiesof the hierarchical composites reflect good consolidation (void content <3%) and excellent fibre alignment(<±0.8◦). In addition to the improved mechanical properties, incorporation of CNTs improved the through-thickness electrical conductivity up to 115 S/m

Journal article

Valkova M, Anthony DB, Kucernak ARJ, Shaffer MSP, Greenhalgh ESet al., 2022, Predicting the mechanical behaviour of structural supercapacitor composites, Composites Part A: Applied Science and Manufacturing, Vol: 156, ISSN: 1359-835X

Multifunctional structural power composites may transform transport electrification, and other applications, but require performance and reliability improvements. Computational modelling has the potential to accelerate their development and deployment. This work addresses the lack of predictive models for the mechanical behaviour of structural supercapacitor composites exploiting carbon aerogel-modified carbon fabric electrodes. The elastic behaviour was investigated using finite element analysis of quasi-meso-scale periodic unit cell models, considering the effects of constituent properties, defects, stacking geometry, and boundary conditions. Nanoindentation was used to evaluate the Young’s modulus of carbon aerogel. Parametric modelling demonstrated a strong influence of the ply offset and matrix materials on the composite elastic properties. The initial numerical results overpredicted the actual performance measured from tensile and in-plane shear experiments in the literature. Optical, scanning electron and micro X-ray imaging revealed extensive pre-cracking and voidage in the physical laminates. Additional computational investigations showed that the pre-cracks were associated with a degradation of shear stiffness. The remaining performance gap was attributed to voidage. The present study highlights that challenges for mechanical performance and its prediction stem from the presence of processing defects and a lack of in-situ material data. Nevertheless, the models identify the potential of hierarchical laminates containing aerogels to generate sizable performance improvements, both in multifunctional and purely structural contexts.

Journal article

Oates RP, Murawski J, Hor C, Shen X, Weber DJ, Oezaslan M, Shaffer MSP, Stephens IELet al., 2022, How to Minimise Hydrogen Evolution on Carbon Based Materials?, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 169, ISSN: 0013-4651

Journal article

Pernice MF, Qi G, Senokos E, Anthony DB, Nguyen S, Valkova M, Greenhalgh E, Shaffer M, Kucernak Aet al., 2022, Mechanical, electrochemical and multifunctional performance of a CFRP/carbon aerogel structural supercapacitor and its corresponding monofunctional equivalents, Multifunctional Material, Vol: 5

Journal article

Xu Z, Tonry C, Beckwith C, Kao A, Wong H, Shaffer MSP, Pericleous K, Li Qet al., 2022, High-speed imaging of the ultrasonic deagglomeration of carbon nanotubes in water, JOM, Vol: 74, ISSN: 1047-4838

Ultrasonic treatment is effective in deagglomerating and dispersing nanoparticles in various liquids. However, the exact deagglomeration mechanisms vary for different nanoparticle clusters, owing to different particle geometries and inter-particle adhesion forces. Here, the deagglomeration mechanisms and the influence of sonotrode amplitude during ultrasonication of multiwall carbon nanotubes in de-ionized water were studied by a combination of high-speed imaging and numerical modeling. Particle image velocimetry was applied to images with a higher field of view to calculate the average streaming speeds distribution. These data allowed direct comparison with modeling results. For images captured at higher frame rates and magnification, different patterns of deagglomeration were identified and categorized based on different stages of cavitation zone development and for regions inside or outside the cavitation zone. The results obtained and discussed in this paper can also be relevant to a wide range of carbonaceous and other high aspect ratio nanomaterials.

Journal article

Lamoriniere S, Jones MP, Ho K, Kalinka G, Shaffer MSP, Bismarck Aet al., 2022, Carbon nanotube enhanced carbon Fibre-Poly(ether ether ketone) interfaces in model hierarchical composites, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 221, ISSN: 0266-3538

Journal article

Leese HS, Tejkl M, Vilar L, Georgi L, Yau HC, Rubio N, Reixach E, Buk J, Jiang Q, Bismarck A, Hahn R, Shaffer MSPet al., 2022, High-k dielectric screen-printed inks for mechanical energy harvesting devices, MATERIALS ADVANCES, Vol: 3, Pages: 1780-1790

Journal article

Navarro Suarez A, Shaffer M, 2022, Designing structural electrochemical energy storage systems: a perspective on the role of device chemistry, Frontiers in Chemistry, Vol: 9, ISSN: 2296-2646

Structural energy storage devices (SESDs), designed to simultaneously store electrical energy and withstand mechanical loads, offer great potential to reduce the overall system weight in applications such as automotive, aircraft, spacecraft, marine and sports equipment. The greatest improvements will come from systems that implement true multifunctional materials as fully as possible. The realization of electrochemical SESDs therefore requires the identification and development of suitable multifunctional structural electrodes, separators, and electrolytes. Different strategies are available depending on the class of electrochemical energy storage device and the specific chemistries selected. Here, we review existing attempts to build SESDs around carbon fiber (CF) composite electrodes, including the use of both organic and inorganic compounds to increase electrochemical performance. We consider some of the key challenges and discuss the implications for the selection of device chemistries.

Journal article

Rubio N, Au H, Coulter GO, Guetaz L, Gebel G, Mattevi C, Shaffer MSPet al., 2021, Effect of graphene flake size on functionalisation: quantifying reaction extent and imaging locus with single Pt atom tags, Chemical Science, Vol: 12, Pages: 1-13, ISSN: 2041-6520

Here, the locus of functionalisation on graphene-related materials and the progress of the reaction is shown to depend strongly on the starting feedstock. Five characteristically different graphite sources were exfoliated and functionalized using a non-destructive chemical reduction method. These archetypical examples were compared via a model reaction, grafting dodecyl addends, evaluated with TGA-MS, XPS and Raman data. A general increase in grafting ratio (ranging from 1.1 wt% up to 25 wt%) and an improvement in grafting stoichiometry (C/R) were observed as flake radius decreased. Raman spectrum imaging of the functionalised natural flake graphite identified that grafting is directed towards flake edges. This behaviour was further corroborated, at atomistic resolution, by functionalising the graphene layers with bipyridine groups able to complex single platinum atoms. The distribution of these groups was then directly imaged using aberration-corrected HAADF-STEM. Platinum atoms were found to be homogeneously distributed across smaller graphenes; in contrast, a more heterogeneous distribution, with a predominance of edge grafting was observed for larger graphites. These observations show that grafting is directed towards flake edges, but not necessary at edge sites; the mechanism is attributed to the relative inaccessibility of the inner basal plane to reactive moieties, resulting in kinetically driven grafting nearer flake edges. This phenomenology may be relevant to a wide range of reactions on graphenes and other 2d materials.

Journal article

Suter TAM, Clancy AJ, Rubio Carrero N, Heitzmann M, Guetaz L, Shearing PR, Mattevi C, Gebel G, Howard CA, Shaffer MSP, McMillan PF, Brett DJLet al., 2021, Scalable sacrificial templating to increase porosity and platinum utilisation in graphene-based polymer electrolyte fuel cell electrodes, Nanomaterials, Vol: 11, Pages: 1-13, ISSN: 2079-4991

Polymer electrolyte fuel cells hold great promise for a range of applications but require advances in durability for widespread commercial uptake. Corrosion of the carbon support is one of the main degradation pathways; hence, corrosion-resilient graphene has been widely suggested as an alternative to traditional carbon black. However, the performance of bulk graphene-based electrodes is typically lower than that of commercial carbon black due to their stacking effects. This article reports a simple, scalable and non-destructive method through which the pore structure and platinum utilisation of graphene-based membrane electrode assemblies can be significantly improved. Urea is incorporated into the catalyst ink before deposition, and is then simply removed from the catalyst layer after spraying by submerging the electrode in water. This additive hinders graphene restacking and increases porosity, resulting in a significant increase in Pt utilisation and current density. This technique does not require harsh template etching and it represents a pathway to significantly improve graphene-based electrodes by introducing hierarchical porosity using scalable liquid processes.

Journal article

Karadotcheva E, Nguyen SN, Greenhalgh ES, Shaffer MSP, Kucernak ARJ, Linde Pet al., 2021, Structural Power Performance Targets for Future Electric Aircraft, Energies, Vol: 14, Pages: 6006-6006

The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites &gt;200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites &gt;400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight.

Journal article

Wendong Q, Dent J, Arrighi V, Cavalcanti L, Shaffer MSP, Shirshova Net al., 2021, Biphasic epoxy-ionic liquid structural electrolytes: minimising feature size through cure cycle and multifunctional block-copolymer addition, Multifunctional Materials, Vol: 4, Pages: 1-12, ISSN: 2399-7532

Structural electrolytes provide mechanical properties approaching structural resin combined with a high degree of ionic conductivity. Here, structural electrolytes based on bisphenol A diglycidyl ether and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIM-TFSI) were synthesised through reaction induced phase separation (RIPS) using isophorone diamine (iPDA) as a curing agent. The microstructure and properties of the resulting materials were controlled through both the initial formulations and the curing temperature. Curing at room temperature generated a bi-continuous structure and improved both mechanical performance and ionic conductivity of the resulting structural electrolytes. The balance between properties can be systematically adjusted; for example, a promising Young's modulus of 800 MPa was obtained simultaneously with an ionic conductivity of 0.28 mS cm−1, for a formulation containing 35 vol% EMIM-TFSI. The lengthscale of the structural features was reduced by an order of magnitude by introducing multifunctional block-copolymers (MF-bcP) based on glycidyl methacrylate (GMA) and quaternised (2-dimethylamino)ethyl methacrylate (DMAEMA). Small angle neutron scattering (SANS), obtained during curing, identified at least two structural phases of different length scale, for the formulations containing MF-bcP, in agreement with microstructures observed using scanning electron microscopy. Such structural electrolytes may be required when using structural electrodes that also have finer characteristic lengthscales. The addition of the MF-bcP to formulations containing 35 vol% EMIM-TFSI produced structural electrolytes with a Young's modulus of 530 MPa and an ionic conductivity of 0.64 mS cm−1.

Journal article

Qi G, Nguyen S, Anthony DB, Kucernak ARJ, Shaffer MSP, Greenhalgh ESet al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, ISSN: 2399-7532

Multifunctional structural supercapacitors based on carbon fibre electrodes (CF) and structural electrolytes (SEs) can realise multifunctionality by simultaneously bearing load and providing electrochemical energy storage. Structural supercapacitor constituents (i.e. electrodes and electrolytes) have undergone significant development to enhance their electrochemical and mechanical properties. However, the fabrication of fully functional devices presents a number of practical challenges to achieve optimal multifunctional properties, particularly those associated with assembly and lamination. This work investigated the effect of separator selection and processing parameters on the electrochemical performance of structural supercapacitors, as well as evaluating the repeatability of the SE filming process. Two layers of glass fibre fabrics were the most effective separator for preventing short-circuiting of the structural supercapacitors. The weight fraction of the SE matrix had a significant effect on the capacitance, energy and power of the structural supercapacitors. By addressing such fabrication challenges, high performance structural supercapacitors can be manufactured with greater reproducibility and at larger scales such that they are suitable for integration in industrial applications.

Journal article

Said SA, Roberts CS, Lee JK, Shaffer MSP, Williams CKet al., 2021, Direct organometallic synthesis of carboxylate intercalated layered zinc hydroxides for fully exfoliated functional nanosheets, Advanced Functional Materials, Vol: 31, Pages: 1-11, ISSN: 1616-301X

Intercalation of organic anions into 2D materials can enable exfoliation, improve dispersion stability, increase surface area, and provide useful functional groups. In layered metal hydroxides, intercalation of bulk structures is commonly achieved by cumbersome and typically incomplete anion exchange reactions. In contrast, here, a series of carboxylate-intercalated layered zinc hydroxides (LZH-R) are synthesized directly, at room temperature, by reacting an organozinc reagent with a precise sub-stoichiometric quantity of the desired carboxylic acid and water. A range of carboxylic acids are used to make new LZH-R materials which are crystalline, soluble, and functionalized, as established by X-ray diffraction, spectroscopic, and microscopy techniques. When R is an alkyl ether carboxylate, this direct synthesis method results in the spontaneous exfoliation of the LZH-R into monolayer nanosheets with high yields (70–80%) and high solubilities in alcohols and water of up to 180 mg mL−1. By altering the carboxylate ligand, functional groups suitable for post-synthetic modification or for detection by fluorescence are also introduced. These examples demonstrate a versatile synthetic route for functional exfoliated nanosheets.

Journal article

Bayazit MK, Xiong L, Jiang C, Moniz SJA, White E, Shaffer MSP, Tang Jet al., 2021, Defect-Free Single-Layer Graphene by 10 s Microwave Solid Exfoliation and Its Application for Catalytic Water Splitting, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 28600-28609, ISSN: 1944-8244

Journal article

Nguyen S, Millereux A, Pouyat A, Greenhalgh E, Shaffer M, Kucernak A, Linde Pet al., 2021, Conceptual multifunctional design, feasibility and requirements for structural power in aircraft cabins, Journal of Aircraft: devoted to aeronautical science and technology, Vol: 58, Pages: 677-687, ISSN: 0021-8669

This paper presents a theoretical investigation into the potential use of structural power composites in regional aircraft passenger cabins and the corresponding challenges to widespread use, including fire-resistance, long-term cycling performance, and cost. This study focusses on adapting sandwich floor panels with structural power composite face sheets, designed to power the in-flight entertainment system. Using a simple mechanical model to define the structural requirements, based on state-of-the-art laminated structural power composites, a series of electrochemical energy storage performance targets were calculated: a specific energy > 144 Wh/kg, a specific power > 0.29 kW/kg, an in-plane elastic modulus > 28 GPa and in-plane tensile and compressive strengths > 219 MPa. Significantly, the use of a distributed energy storage system offered a significant range of other mass and cost savings, associated with a simplified power system, and the use of ground-generated electrical energy. For an Airbus A220-100, the analysis predicted potential mass and volume savings of approximately 260 kg and 510 land annual reductions in CO2and NOx emissions of approximately 280 tonnes and 1.2 tonnes respectively. This extended design analysis of a specific component highlights both the far-reaching implications of implementing structural power materials and the potential extensive systemic benefits.

Journal article

Moore J, Paineau E, Launois P, Shaffer Met al., 2021, Continuous binder-free fibers of pure imogolite nanotubes, ACS Applied Materials and Interfaces, Vol: 13, Pages: 17940-17947, ISSN: 1944-8244

Imogolite nanotubes display a range of useful properties and provide an ideal material system to study the assembly of nanomaterials into macroscopic fibers. A method of wet spinning pure, binder-free imogolite fibers has been developed using double walled germanium imogolite nanotubes. Nanotube aspect ratio can be controlled during the initial synthesis and is critical to the spinning process. Fibers made from short nanotubes (<100 nm) have very low gel strengths, whilst dopes with longer nanotubes (500-1000 nm) are readily spinnable. The tensile behaviour of the resulting imogolite nanotube fibers is strongly influenced by relative humidity (RH), with a modulus of 30 GPa at 10% RH compared to 2.8 GPa at 85% RH, as well as a change in failure mode. This result highlights the importance of inter nanotube interactions in such assemblies and provides a useful strategy for further exploration. Interestingly, in the absence of a matrix phase, a degree of misorientation appears to improve load transfer between the individual INTs within the porous fiber, likely due to an increase of the number of inter-particle contacts. Imogolite nanotubes are an appealing analogue to other nanotube fiber systems, and it is hoped that learnings from this system can also be used to improve carbon nanotube fibers.

Journal article

Sirisinudomkit P, Senokos E, Rubio Carrero N, Shaffer Met al., 2021, Reductive processing of single walled carbon nanotubes for high volumetric performance supercapacitors, Materials Advances, Vol: 2, Pages: 1981-1992, ISSN: 2633-5409

Intrinsically, single walled carbon nanotubes (SWCNTs) are excellent candidates for electrochemical double layer supercapacitor (EDLC) electrodes, owing to their high electrical conductivity, high accessible surface area, and high aspect ratio/connectivity, which provide exceptional intrinsic gravimetric energy and power densities. However, in practice, local bundling due to strong intertube van der Waals interactions reduces the effective surface area; at larger scales, the bundling also creates low density networks that limit the volumetric electrochemical performance of practical electrodes. In this study, reductive charging is used to dissolve individual SWCNTs and assemble them to form relatively dense (0.34 g cm−3), thick (38 μm) ‘buckypaper’ electrodes, with high electrical conductivity (>400 S cm−1). Intermediate charging ratios (C : Na = 10 : 1) and carbon concentrations (0.125 M) provide greater SWCNT solubilisation and individualisation, and correlate with maximum volumetric capacitance of 74 F cmelectrode−3 at 10 mV s−1 in 1 M H2SO4. These optimised half-cell electrodes were implemented in full symmetric cell devices, prepared in both aqueous and ionic liquid electrolytes, using a bespoke bacterial cellulose (BC) ultrathin separator (7 microns) to minimize parasitic mass/volume. The full cell performance in ionic liquid reached maximum energy and power densities of 2.6 Wh kg−1 (2.2 mWh cm−3), and 10.2 kW kg−1 (8.3 W cm−3), respectively, normalised by the total mass and volume of device (electrodes, electrolyte, and separator; no separate current collector is needed). The relatively effective transfer of half-cell to full-cell performance is encouraging but could be optimized further in future. Appropriate normalisations for supercapacitor electrodes and devices are discussed in detail. Thin BC-based separators have wide applicability to other electrochemical devices.

Journal article

Lee C, Greenhalgh E, Shaffer M, Panesar Aet al., 2020, Optimized microstructures for multifunctional structural electrolytes, Multifunctional Materials, Vol: 2, ISSN: 2399-7532

Multifunctional structural materials offer compelling opportunities to realize highly efficient products. However, the need to fulfil disparate functions generates intrinsically conflicting physical property demands. One attractive strategy is to form a bi-continuous architecture of two disparate phases, each addressing a distinct physical property. For example, structural polymer electrolytes combine rigid and ion-conducting phases to deliver the required mechanical and electrochemical performance. Here, we present a general methodology, based on topology optimization, to identify optimal microstructures for particular design considerations. The numerical predictions have been successfully validated by experiments using 3D printed specimens. These architectures are directly relevant to multifunctional structural composites whilst the methodology can easily be extended to identify optimal microstructural designs for other multifunctional material embodiments.

Journal article

Rehman MAU, Chen Q, Braem A, Shaffer M, Boccaccini Aet al., 2020, Electrophoretic deposition of carbon nanotubes: recent progress and remaining challenges, International Materials Reviews, Vol: 66, Pages: 533-562, ISSN: 0950-6608

Electrophoretic deposition (EPD) is a powerful technique to assemble carbon nanotube (CNT) coatings and composite films with controlled architectures. This comprehensive review of the EPD of CNTs and CNT-containing composites focuses on achievements within the last 15 years and ongoing challenges. Stable CNT suspensions are a pre-requisite for successful EPD and have been prepared by a variety of strategies, discussed here. The resulting film microstructure is determined by the initial feedstock, the suspension, and the EPD approach applied, as well as a variety of EPD processing parameters. Nanocomposites can be prepared via co-deposition, sequential deposition, or post-deposition treatments, to introduce metallic, ceramic or polymeric phases. There are numerous potential applications for both homogeneous and patterned CNT films, including as structural reinforcements for composites, as field emission, energy storage and conversion devices, as well as in biomedical applications. The advantages and disadvantages of EPD processing in these contexts are discussed.

Journal article

Michaeloudes C, Seiffert J, Chen S, Ruenraroengsak P, Bey L, Theodorou IG, Ryan M, Cui X, Zhang J, Shaffer M, Tetley T, Porter AE, Chung KFet al., 2020, Effect of silver nanospheres and nanowires on human airway smooth muscle cells: role of sulfidation, Nanoscale Advances, Vol: 2, Pages: 5635-5647, ISSN: 2516-0230

Background: The toxicity of inhaled silver nanoparticles on contractile and pro-inflammatory airway smooth muscle cells (ASMCs) that control airway calibre is unknown. We explored the oxidative activities and sulfidation processes of the toxic-inflammatory response. Method: Silver nanospheres (AgNSs) of 20 nm and 50 nm diameter and silver nanowires (AgNWs), short S-AgNWs, 1.5 μm and long L-AgNWs, 10 μm, both 72 nm in diameter were manufactured. We measured their effects on cell proliferation, mitochondrial reactive oxygen species (ROS) release and membrane potential, and also performed electron microscopic studies. Main results and findings: The greatest effects were observed for the smallest particles with the highest specific surface area and greatest solubility that were avidly internalised. ASMCs exposed to 20 nm AgNSs (25 μg mL−1) for 72 hours exhibited a significant decrease in DNA incorporation (−72.4%; p < 0.05), whereas neither the 50 nm AgNSs nor the s-AgNWs altered DNA synthesis or viability. There was a small reduction in ASMC proliferation for the smaller AgNS, although Ag+ at 25 μL mL−1 reduced DNA synthesis by 93.3% (p < 0.001). Mitochondrial potential was reduced by both Ag+ (25 μg mL−1) by 47.1% and 20 nm Ag NSs (25 μg mL−1) by 40.1% (*both at p < 0.05), but was not affected by 50 nm AgNSs and the AgNWs. None of the samples showed a change in ROS toxicity. However, malondialdehyde release, associated with greater total ROS, was observed for all AgNPs, to an extent following the geometric size (20 nm AgNS: 213%, p < 0.01; 50 nm AgNS: 179.5%, p < 0.01 and L-AgNWs by 156.2%, p < 0.05). The antioxidant, N-acetylcysteine, prevented the reduction in mitochondrial potential caused by 20 nm AgNSs. The smaller nanostructures were internalised and dissolved within the ASMCs with the formation of non-reactive silver sulphide (Ag2S) on their surface, but with very little uptake of L-AgNWs. When A

Journal article

De Luca H, Anthony D, Greenhalgh E, Bismarck A, Shaffer Met al., 2020, Piezoresistive structural composites reinforced by carbon nanotube-grafted quartz fibres, Composites Science and Technology, Vol: 198, Pages: 1-12, ISSN: 0266-3538

Nano-engineered fibre/matrix interfaces can improve state-of-the-art fibre-reinforced composites. Grafting carbon nanotubes (CNTs) to high temperature quartz glass fibres produces “hairy” or “fuzzy” fibres, which combine reinforcements at micrometre and nanometre length scales. Fuzzy quartz fibres were produced continuously, reel-to-reel, on whole tows, in an open chemical vapour deposition reactor. The resulting uniform coverage of 200 nm long CNTs increased the interfacial shear strength with epoxy (90.3 ± 2.1 MPa) by 12% compared to the commercially-sized counterpart, as measured by single fibre pull-out tests. The improved interfacial properties were confirmed at the macroscale using unidirectional hierarchical bundle composites, which exhibited a delayed onset of fibre/matrix debonding. Although the quartz fibres are electrically insulating, the grafted CNT create a conductive path, predominantly parallel to the fibres. To explore the applicability for structural health monitoring, the resistivity was recorded in situ during mechanical testing, and correlated with simultaneous acoustic emission data. The baseline resistivity parallel to the fibres (ρ0 = 3.9 ± 0.4 × 10−1 Ω m) displayed a linear piezoresistive response (K = 3.64) until failure at ca. 2.1% strain, also referred to as "gauge factor”, a two-fold improvement over traditional resistance strain gauges (e.g. constantan). Hierarchical, fuzzy quartz fibres, therefore, simultaneously enhance both structural and sensing performance, offering multifunctional opportunities in large composite parts.

Journal article

Finley JM, Shaffer MSP, Pimenta S, 2020, Data-driven intelligent optimisation of discontinuous composites, Composite Structures, Vol: 243, Pages: 1-19, ISSN: 0263-8223

Fibre composites, and especially aligned discontinuous composites (ADCs), offer enormous versatility in composition, microstructure, and performance, but are difficult to optimise, due to their inherent variability and myriad permutations of microstructural design variables. This work combines an accurate yet efficient virtual testing framework (VTF) with a data-driven intelligent Bayesian optimisation routine, to maximise the mechanical performance of ADCs for a number of single- and multi-objective design cases. The use of a surrogate model helps to minimise the number of optimisation iterations, and provides a more accurate insight into the expected performance of materials which feature significant variability. Results from the single-objective optimisation study show that a wide range of structural properties can be achieved using ADCs, with a maximum stiffness of 505 GPa, maximum ultimate strain of 3.94%, or a maximum ultimate strength of 1.92 GPa all possible. A moderate trade-off in performance can be achieved when considering multi-objective optimisation design cases, such as an optimal ultimate strength & ultimate strain combination of 982 MPa and 3.27%, or an optimal combination of 720 MPa yield strength & 1.91% pseudo-ductile strain.

Journal article

Clancy AJ, Au H, Rubio N, Coulter GO, Shaffer MSPet al., 2020, Understanding and controlling the covalent functionalisation of graphene, Dalton Transactions, Vol: 49, Pages: 10308-10318, ISSN: 1477-9226

Chemical functionalisation is one of the most active areas of graphene research, motivated by fundamental science, the opportunities to adjust or supplement intrinsic properties, and the need to assemble materials for a broad array of applications. Historically, the primary consideration has been the degree of functionalisation but there is growing interest in understanding how and where modification occurs. Reactions may proceed preferentially at edges, defects, or on graphitic faces; they may be correlated, uncorrelated, or anti-correlated with previously grafted sites. A detailed collation of existing literature data indicates that steric effects play a strong role in limiting the extent of reaction. However, the pattern of functionalisation may have important effects on the resulting properties. This article addresses the unifying principles of current graphene functionalisation technologies, with emphasis on understanding and controlling the locus of functionalisation.

Journal article

Leung AHM, García-Trenco A, Phanopoulos A, Regoutz A, Schuster ME, Pike SD, Shaffer MSP, Williams CKet al., 2020, Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol, Journal of Materials Chemistry A, Vol: 8, Pages: 11282-11291, ISSN: 2050-7488

Doped-ZnO nanoparticles, capped with dioctylphosphinate ligands, are synthesised by the controlled hydrolysis of a mixture of organometallic precursors. Substitutional doping of the wurtzite ZnO nanoparticles with 5 mol% Mg(II), Al(III) and Cu(I) is achieved by the addition of sub-stoichiometric amounts of the appropriate dopant [(n-butyl)(sec-butyl)magnesium, triethylaluminium or mesitylcopper] to diethylzinc in the precursor mixture. After hydrolysis, the resulting colloidal nanoparticles (sizes of 2–3 nm) are characterised by powder X-ray crystallography, transmission electron microscopy, inductively-coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. A solution of the doped-ZnO nanoparticles and colloidal Cu(0) nanoparticles [M:ZnO : Cu = 1 : 1] are applied as catalysts for the hydrogenation of CO2 to methanol in a liquid-phase continuous flow stirred tank reactor [210 °C, 50 bar, CO2 : H2 = 1 : 3, 150 mL min−1, mesitylene, 20 h]. All the catalyst systems display higher rates of methanol production and better stability than a benchmark heterogeneous catalyst, Cu–ZnO–Al2O3 [480 μmol mmolmetal−1 h−1], with approximately twice the activity for the Al(III)-doped nanocatalyst. Despite outperforming the benchmark catalyst, Mg(II) doping is detrimental towards methanol production in comparison to undoped ZnO. X-Ray photoelectron spectroscopy and transmission electron microscopy analysis of the most active post-catalysis samples implicate the migration of Al(III) to the catalyst surface, and this surface enrichment is proposed to facilitate stabilisation of the catalytic ZnO/Cu interfaces.

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00386229&limit=30&person=true