Dr Carol Crean


Reader in Physical and Materials Chemistry
+44 (0)1483 686640
30 AZ 03
08:15 - 17:00 (Mon-Thurs) 08:15 - 14.15 (Fri)

Academic and research departments

School of Chemistry and Chemical Engineering.

About

Areas of specialism

Materials Chemistry; Flexible electrode materials; Textile electrodes for healthcare applications; Materials for Energy storage

University roles and responsibilities

  • Director of Employability

    My qualifications

    BSc (Hons) in Chemistry with German
    Dublin City University, Ireland
    PhD in Chemistry
    Dublin City University, Ireland
    Graduate Certificate in Learning and Teaching
    University of Surrey, UK

    Research

    Research interests

    Research collaborations

    Supervision

    Postgraduate research supervision

    Completed postgraduate research projects I have supervised

    Teaching

    Publications

    Joydip Ghosh, Joseph O’Neill, Mateus G. Masteghin, Isabel Braddock, Carol Crean, Robert Dorey, Hayden Salway, Miguel Anaya, Justin Reiss, Douglas Wolfe, Paul Sellin (2023)Surfactant-Dependent Bulk Scale Mechanochemical Synthesis of CsPbBr 3 Nanocrystals for Plastic Scintillator-Based X-ray Imaging, In: ACS Applied Nano Materials American Chemical Society

    We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr3/PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr3 NC-loaded nanocomposite disc.

    Joseph O'Neill, Joydip Ghosh, Suad Alghamdi, Isabel Braddock, Carol Crean, Robert Dorey, Roma Mulholland, Sion Richards, Matthew Wilson, Hayden Salway, Miguel Anaya, Justin Reiss, Douglas Wolfe, Paul Sellin (2024)Hydrothermal and Mechanosynthesis of Mixed‐Cation Double Perovskite Scintillators for Radiation Detection, In: Advanced Optical Materials12(2)2301335 Wiley

    This article details work performed on the synthesis and characterization of an inorganic mixed‐cation double halide perovskite, Cs 2 Ag .6 Na .4 In .85 Bi .15 Cl 6 (CANIBIC). Single crystals have been created via a hydrothermal reaction, milled into a powder, and pressed into pellets, while nanocrystals have been directly synthesized via mechanosynthesis. A computational model is constructed to predict the X‐ray diffraction pattern of CANIBIC; this model aligns very well with the X‐ray diffraction pattern measured for CANIBIC crystal powder. This model can therefore be developed in the future as a tool to predict lattice parameters and crystal structures of other novel double‐halide perovskites. Photoluminescence spectra obtained from each format show broad emission centered at 630 nm, as is typical for self‐trapped exciton emission; self‐trapped exciton emission is also confirmed by investigating photoluminescence intensity as a function of laser power. Nanocomposites are produced via the loading of nanocrystals of CANIBIC into PMMA. Although nanocomposite disks consisting of a small proportion of CANIBIC nanocrystals in PMMA have a smaller mass attenuation coefficient than a pressed pellet of CANIBIC, these disks have comparatively bright radioluminescence due to their optical transparency. These nanocomposite disks are therefore a particularly useful format for the practical use of the CANIBIC scintillator.

    Simone Caroline Mathias, Marius Amerio-Cox, Toni Louise Jackson, David Douce, Ashley Sage, Peter Luke, Richard Sleeman, Carol Crean, Patrick Sears (2023)Selectivity of Explosives Analysis with Ambient Ionization Single Quadrupole Mass Spectrometry: Implications for Trace Detection, In: Journal of the American Society for Mass Spectrometry35(1)pp. 50-61 ACS

    Ambient ionization (AI) is a rapidly growing field in mass spectrometry (MS). It allows for the direct analysis of samples without any sample preparation, making it a promising technique for the detection of explosives. Previous studies have shown that AI can be used to detect a variety of explosives, but the exact gas-phase reactions that occur during ionization are not fully understood. This is further complicated by differences in mass spectrometers and individual experimental set ups between researchers. This study investigated the gas-phase ion reactions of five different explosives using a variety of AI techniques coupled to a Waters QDa mass spectrometer to identify selective ions for explosive detection and identification based on the applied ambient ionization technique. The results showed that the choice of the ion source can have a significant impact on the number of ions observed. This can affect the sensitivity and selectivity of the data produced. The findings of this study provide new insights into the gas-phase ion reactions of explosives and could lead to the development of more sensitive and selective AI-based methods for their detection.

    C.S Nagi, S.L Ogin, I Mohagheghian, C Crean, A.D Foreman (2018)Interlaminar Toughening of Carbon Fibre Reinforced Polymers using Graphene / Thermoplastic Inserts European Society for Composite Materials

    This paper outlines preliminary work developing graphene modified thermoplastic inserts to be used for the toughening of CFRP. The paper outlines laminate manufacture, mechanical testing and fracture analysis of graphene modified CFRP.

    J O'Neill, J Ghosh, S Alghamdi, I Braddock, C Crean, R Dorey, R Mulholland, S Richards, M Wilson, H Salway, M Anaya, J Reiss, D Wolfe, P Sellin (2023)Hydrothermal and Mechanosynthesis of Mixed-Cation Double Perovskite Scintillators for Radiation Detection Wiley

    Publication status: Published Funder: STFC; doi: http://dx.doi.org/10.13039/501100000271 Funder: Rutherford Appleton Laboratory; doi: http://dx.doi.org/10.13039/100014570 AbstractThis article details work performed on the synthesis and characterization of an inorganic mixed‐cation double halide perovskite, Cs2Ag.6Na.4In.85Bi.15Cl6 (CANIBIC). Single crystals have been created via a hydrothermal reaction, milled into a powder, and pressed into pellets, while nanocrystals have been directly synthesized via mechanosynthesis. A computational model is constructed to predict the X‐ray diffraction pattern of CANIBIC; this model aligns very well with the X‐ray diffraction pattern measured for CANIBIC crystal powder. This model can therefore be developed in the future as a tool to predict lattice parameters and crystal structures of other novel double‐halide perovskites. Photoluminescence spectra obtained from each format show broad emission centered at 630 nm, as is typical for self‐trapped exciton emission; self‐trapped exciton emission is also confirmed by investigating photoluminescence intensity as a function of laser power. Nanocomposites are produced via the loading of nanocrystals of CANIBIC into PMMA. Although nanocomposite disks consisting of a small proportion of CANIBIC nanocrystals in PMMA have a smaller mass attenuation coefficient than a pressed pellet of CANIBIC, these disks have comparatively bright radioluminescence due to their optical transparency. These nanocomposite disks are therefore a particularly useful format for the practical use of the CANIBIC scintillator.

    Joseph O'Neill, Isabel Braddock, Carol Crean, Joydip Ghosh, Mateus Masteghin, Sion Richards, Matthew Wilson, Paul Sellin (2023)Development and characterisation of caesium lead halide perovskite nanocomposite scintillators for X-ray detection, In: Frontiers in physics10 Frontiers Media Sa

    We present work on the development of mixed-halide perovskite (CsPbClx Br(1-x)) nanocrystal scintillators for X-ray detection applications. The effect of the varying the halide composition on the resulting peak emission and light yield is discussed, with the CsPbBr3 materials displaying the greatest light yield. These perovskite nanocrystals were successfully loaded into PMMA, an inert plastic, at 2% mass weighting and the responses of these composites were compared to that of their colloidal dispersions. The composites were also characterised in terms of the radioluminescent light yield and decay response, alongside their X-ray sensitivity, in which the PMMA-CsPbBr3 composites again outperformed the materials containing Cl- anions.

    Joydip Ghosh, Joseph O'Neill, Mateus G Masteghin, Isabel Braddock, Carol Crean, Robert Dorey, Hayden Salway, Miguel Anaya, Justin Reiss, Douglas Wolfe, Paul Sellin (2023)Surfactant-Dependent Bulk Scale Mechanochemical Synthesis of CsPbBr3 Nanocrystals for Plastic Scintillator-Based X-ray Imaging American Chemical Society (ACS)

    We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr3/PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr3 NC-loaded nanocomposite disc.

    Logan J. Forth, Harry Gibbard, Stephanie Biddlecombe, Isabel Braddock, Carol Crean, Jia C. Khong, Mingqing Wang, Robert Speller, Kwang L. Choy, Paul Sellin, Rob Moss (2020)Polycrystalline Perovskite X-ray Detectors, In: 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)pp. 1-3 IEEE

    Metal-halide perovskite materials have begun to attract much attention recently for their potential use in radiation detection applications. This interest is mainly due to their favourable semi-conductive properties, high electron density, ease of manufacture and relatively low cost compared to popular detector materials. In this paper we investigate inorganic caesium lead bromide (CsPbBr3). Polycrystalline powder samples were produced by solution growth and simple 'sandwich' devices were fabricated. The powder was manually ground and then pressed to form pellets of a few mm thickness. Gold planar electrodes were deposited on the top and bottom perovskite surfaces by evaporation and were connected to an external circuit. We have made comparative measurements of the photoluminescence (PL), dark current and temporal radiation response. The PL measurements showed stable emissions centred at 525 nm for CsPbBr 3 ' which is typical of these materials and within a useful range for this application. A CsPbBr3 device was exposed to X-rays and demonstrates a good increase in photocurrent over the dark current under both positive and negative bias with a sensitivity of 33.8 µCGy −1 air cm −2 and the temporal response was determined to be ~40 ms by measuring the photocurrent decay after X-ray illumination.

    John Varcoe, Rachida Bance-Souahli, Arup Chakraborty, Mehdi Choolaei, Carol Crean, Carlos Giron Rodriguez, Bjørt Óladóttir Joensen, Judy Lee, Arun Prakash Periasamy, Ihtasham Salam, Brian Seger, Daniel Whelligan, Terrence Willson (2022)The Latest Developments in Radiation-Grafted Anion-Exchange Polymer Electrolytes for Low Temperature Electrochemical Systems, In: Meeting abstracts (Electrochemical Society)MA2022-01(35)pp. 1443-1443 The Electrochemical Society, Inc
    Sutthima Sriprasertsuk, John R. Varcoe, Carol Crean (2021)Reduced Graphene Oxide Fibre Electrodes for Drug Sensing, In: Proceedings68(18) MDPI AG

    Reduced graphene oxide (rGO) fibre electrodes and their ability to sense paracetamol (as model drug) were studied. rGO was electrodeposited onto carbon fibre by two different approaches: potentiostatic deposition and cyclic voltammetry (CV) in the presence of graphene oxide solution. Carbon fibre electrodes coated with rGO (after five CV cycles) could sense paracetamol with an oxidation peak at 0.62 V (vs. Ag/AgCl). The limit of detection of this fibre sensor was found to be 36.3 µM with a linear range of 50–500 µM of paracetamol (R2 = 0.9901).

    Rachel Smith, Mona Sweilam, John Varcoe, Carol Crean (2020)Thread-Based Sensors, In: Proceedings32(1) MDPI AG

    Fiber and textile-based chemical sensors are emerging tools which target minimally invasive monitoring. Fiber-shaped electrodes are a versatile design for wearable applications since the fiber architecture allows for straightforward integration into textiles facilitating the principle of “wear-and-forget”. Skin and wound care would benefit from real-time pH monitoring, which can indicate wound health and the physiological condition of the skin. A further application of wearable chemical sensors is therapeutic drug monitoring.

    John R. Varcoe, Carol Crean (2020)Polypyrrole Fibre Electrodes for Drug Sensing, In: Proceedings32(1) MDPI AG

    Polypyrrole (PPy) fibre electrodes and their ability to sense paracetamol (as a model drug) in addition to interferents such as ascorbic acid and dopamine were studied. PPy was electrodeposited onto carbon fibre (CF) through electropolymerisation using cyclic voltammetry in the presence of two different counter anions: potassium nitrate (KNO3) and sodium dodecyl sulfate (SDS). PPy with SDS as dopant could sense paracetamol with an oxidation peak at 0.55 V vs. Ag/AgCl. The limit of detection of this fibre sensor was found to be 1 µM with a linear range of 1–100 µM of paracetamol (R2 = 0.985).

    RACHIDA BANCE-SOUALHI, MOHAMMADMEHDI CHOOLAEI, SIAN ALICE FRANKLIN, TERRENCE WILLSON, Judy Lee, DANIEL KEITH WHELLIGAN, CAROL CREAN, JOHN VARCOE (2021)Radiation-grafted anion-exchange membranes for reverse electrodialysis: a comparison of N,N,N′,N′-tetramethylhexane-1,6-diamine crosslinking (amination stage) and divinylbenzene crosslinking (grafting stage), In: Dataset The Royal Society of Chemistry

    Radiation-grafted anion-exchange membranes (RG-AEM) are being developed to evaluate a range of chemistries that have relevance to a variety of electrochemical applications including reverse electrodialysis (RED) salinity gradient power. RG-AEMs are typically fabricated using an electron-beam activated (peroxidated) polymer substrate film. These activated films are first grafted with a monomer, such as vinylbenzyl chloride (VBC) and then reacted with a variety of tertiary amines to yield the desired RG-AEMs. The amination process forms covalently bound quaternary ammonium (QA) head-groups that allow the RG-AEMs to conduct anions such as Cl−. RG-AEMs are of interest as they exhibit high conductivities (100 mS cm−1 at elevated temperatures when containing Cl− anions). However, the current generation of RG-AEMs have two main Achilles' heels: (1) they exhibit low permselectivities; and (2) they exhibit a high degree of swelling in water. Introducing covalent crosslinking into ion-exchange membranes is a well-known strategy to overcome these issues but it often comes with a price – a significantly lowered conductivity (raised in situ resistance). Therefore, the level of crosslinking must be carefully optimised. RG-AEMs can be primarily crosslinked using two methods: (1) introduction of a divinyl monomer into the monomer mixture used during grafting; or (2) introduction of a diamine agent into the amination process. This study looks into both methods where either divinylbenzene (DVB) is added into the grafting mixture or N,N,N′,N′-tetramethylhexane-1,6-diamine (TMHDA) is added into the amination mixture. We show that on the balance of two application-relevant properties (resistances in aqueous NaCl (0.5 mol dm−3) solution and permselectivity), the diamine crosslinking method is the most effective for RG-AEMs being used in RED cells.

    Rachida Bance-Soualhi, Carol Crean, Henryk Herman, Saima Islania, Cheuk Ying Lai, Mariya Tencheva, John R. Varcoe, Daniel Whelligan (2020)A Raman Spectroscopic Study of Radiation-Grafted Anion-Exchange Membranes Containing Different Anions, In: Meeting abstracts (Electrochemical Society)MA2020-01(38)pp. 1641-1641

    Anion exchange membranes (AEM) are being developed for use in a variety of electrochemical energy systems, such as alkaline membrane fuel cells, AEM-based electrolysers, reverse electrodialysis (RED), and redox flow batteries (RFB). The AEMs used will contain a variety of anions, depending on the application. For fuel cells and electrolysers (H 2 generating or CO 2 conversion), then alkaline anions such as OH - , CO 3 2- , and HCO 3 - are important. For RED cells and RFBs, non-alkali anions such as Cl - , HSO 4 - , and SO 4 2- are more relevant. If an AEM is synthesised using a methyl iodide reaction, then monitoring the ion-exchange of the resulting "as-synthesised" I - forms to other forms, such as Cl - , is important as it is well known that it can be difficult to completely ion-exchange soft anions such as I - out of AEMs (particularly those containing aromatic cationic groups). This presentation will highlight some initial results obtained from an on-going Raman spectroscopic study of radiation-grafted AEMs (RG-AEM). This study was initiated to see if Raman spectro-microscopy can be used to identify the anion form of a RG-AEM by looking at the shifts and intensity changes of Raman peaks as a function of anion. The RG-AEMs will be made from either the grafting of vinylbenzyl chloride onto ETFE (followed by reaction with amines such as trimethylamine, imidazole and pyridine) or the grafting of alternative monomers such as vinylpyridine onto ETFE (followed by reaction with methyl iodide). The below Figure shows Raman spectra (Renishaw inVia Raman microscope: 785 nm laser, 1800 lines mm -1 grating, and x20 objective giving a Airy spot diameter of ca. 3 μm) of a RG-AEM made from the grafting of vinylpyridine onto ETFE films (with a final methyl iodide reaction) in both the I - and Cl - forms (three spectra each): . Figure 1

    J. R. Kelly, Khaled Yahya Alqurashi, Carol Crean, H.R.D. Filgueiras, Zhe Chen, Hang Wong (2019)High Gain Beam Steerable Phased Array Incorporating Reconfigurable Parasitics formed from Liquid Metal, In: 2019 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC)pp. 235-238 IEEE

    This paper presents a beam switchable antenna for use as the radiating element within a phased array and shows how it can be used to increase the scan angle range of a phased array. The radiating element consists of a driven dipole and a series of directors. A group of 3 directors are aligned along each of the 2 beam switching directions. The directors are formed from liquid metal. By moving the liquid metal from one set of directors to the other it is possible to switch the beam direction between ± 25 ° . The novel radiating element is used within a phase array. By employing a combination of beam switching at the element factor level and beam steering at the array factor level we are able to obtain an ±9 ° (i.e. 18 ° total) increase in the scan angle range at the expense of a slight reduction in the realized gain.

    W Lee, Carol Crean, John Varcoe, Rachida Bance-Soualhi (2017)A Raman spectro-microscopic investigation of ETFE-based radiation-grafted anion-exchange membranes, In: RSC Advances7pp. 47726-47737 Royal Society of Chemistry

    This study used Raman spectro-microscopy to investigate the synthesis and degradation of radiation-grafted anion-exchange membranes (RG-AEM) made using 50 μm thick poly(ethylene-co-tetrafluoroethylene) (ETFE) films, vinylbenzyl chloride (VBC) monomer, and 1-methylpyrrolidine (MPY) amination agent. The data obtained confirmed the operation of the grafting-front mechanism. VBC grafting times of 1 and 4 h led to low degrees of grafting homogeneity, while 72 h led to extreme levels of grafting that resulted in mechanically weak RG-AEMs due to the excessive H2O contents. A grafting time of 16 h was optimal yielding a RG-AEM with an ion-exchange capacity (IEC) of 2.06 ± 0.02 mmol g-1 (n = 3). An excess of grafting was detected at the surface of this RG-AEM (at least within the first few μm of the surface). This RG-AEM was then degraded in O2-purged aqueous KOH (1.0 mol dm-3) for 14 d at 80 °C. Degradation was detected throughout the RG-AEM cross-section, where the Raman data was quantitatively consistent with the loss of IEC. A slight excess of degradation was detected at the surface of the RG-AEM. Degradation involved the loss of whole benzyl-1-methypyrrolidinium grafted units as well as the direct attack on the pendent (cationic) pyrrolidinium groups by the hydroxide anions.

    Jose Garcia-Torres, Carol Crean (2017)Multilayered Flexible Fibers with High Performance for Wearable Supercapacitor Applications, In: Advanced Sustainable Systems2(2)1700143 Wiley

    Multilayered flexible fibers, consisting of carbon black-carbon nanotube fibers, manganese oxides and conducting polymers, were fabricated for use as electrodes in supercapacitors. Carbon-based fibers were initially prepared by wet-spinning using carbon-based nanomaterials (carbon black and carbon nanotubes) and chitosan as a matrix. Subsequent coatings with manganese oxides and conducting polymers form a multilayered structure. Different MnO2 crystalline structures (ε-MnO2, γ-MnO2) were grown onto the fibre by electrodeposition and different conducting polymers (polyethylenedioxythiophene and polypyrrole) used as a conductive wrapping. Each layer improved the performance of the fibre by adding different functionalities. While MnO2 improved the capacitance of the fibre, the presence of conducting polymers creates a conductive network increasing the capacitance further and conferring cycling stability. Capacitance values up 600 F g-1 and capacitance retention of 90% can be achieved with these multilayered hybrid fibers. A symmetric supercapacitor device, prepared from two hybrid fibres showed no significant change in properties when the device was bent, demonstrating their potential in flexible electronic devices and wearable energy systems.

    Emily A. M. Smith, Yuqing Liu, Chris Stirling, David J. Watson, Robert C. T. Slade, Jun Chen, Carol Crean (2019)Plasma functionalisation of few-layer graphenes and carbon nanotubes for graphene microsupercapacitors, In: Electrochimica Acta Elsevier

    Plasma processing, as a commercial and large-scale technology, was used to functionalize few-layer graphene (FLG) and multi-walled carbon nanotubes (MWCNT) in this work. The successful functionalities of FLG and MWCNT have been confirmed by elemental microanalysis, X-ray photoelectron spectroscopy, acid-base titration and zeta potential measurements. With the assistance of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT/PSS), a water-dispersible and conductive polymer, a composite of functionalized FLG and MWCNT was fabricated into large-size flexible films and also interdigitated microelectrodes for microsupercapacitor application via simple and scalable techniques (i.e. doctor blading and laser-etching). When normalised by volume and area, the device made from FLG(NH3)-MWCNT(Acid) (19.9 F cm-3 at 5 mV s-1 and 12.2 F cm-3 at 200 mV s-1) and FLG-MWCNT(Acid) (19.5 mF cm-2 at 5 mV s-1 and 12.8 mF cm-2 at 200 mV s-1) show the best performing composites, respectively, indicating how effective functionalization of FLG and MWCNT is for the enhancement of electrochemical capacitance. In-situ Raman microscopy confirmed the reversible pseudo-capacitive behaviour of electrode materials and the stable electrochemical performance of the devices. The facile techniques used in this work and the good device performance show their great potential for wearable applications.

    Rachel E. Smith, Stella Totti, Eirini Velliou, Paola Campagnolo, Suzanne M. Hingley-Wilson, Neil I. Ward, John R. Varcoe, Carol Crean (2019)Development of a novel highly conductive and flexible cotton yarn for wearable pH sensor technology, In: Sensors and Actuators B: Chemical287pp. 338-345 Elsevier

    The simple and effective approach of “dipping and drying” cotton yarn in a dispersion of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNT) resulted in the development of a highly conductive and flexible cotton fibres. Subsequent polyaniline (PANi) deposition yielded electrodes with significant biocompatible and antibacterial properties that could be fabricated (alongside quasi-reference electrodes) into solid-state wearable pH sensors, which achieve rapid, selective, and Nernstian responses (-61 ± 2 mV pH-1) over a wide pH range (2.0 – 12.0), even in a pH-adjusted artificial sweat matrix. This development represents an important progression towards the realisation of real-time, on-body, wearable sensors.

    Daniel O. Reid, Rachel Smith, Jose Garcia-Torres, John J. Watts, Carol Crean (2019)Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing, In: Sensors19(19)4213pp. 1-10 MDPI

    There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 μm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm−1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.

    Jose Garcia-Torres, Carol Crean, Elisa Vallés (2017)Co-Ni-carbon flexible composite fibres for directional magnetic actuation, In: Materials & Design141pp. 9-16 Elsevier

    Flexible microcomponents are being widely employed in the microelectronic industry; however; they suffer from a lack of complex movement. To address this problem, we have developed flexible, electrically conductive, magnetic composite fibres showing complex motion in three dimensions with the capacity to be selectively actuated. Flexible carbon-based fibres were prepared by wet-spinning and were subsequently modified by electrodepositing Co-Ni. The high aspect ratio of the fibre (40 μm diameter, 3.5 cm length) causes a directional dependence in the magnetostatic energy, which will allow for anisotropic actuation of the composite. Thus, the application of magnetic fields allows for a precise control of the movement with high reproducibility and accuracy.

    Jose Garcia-Torres, Alexander J. Roberts, Robert C.T. Slade, Carol Crean (2019)One-step wet-spinning process of CB/CNT/MnO2 nanotubes hybrid flexible fibres as electrodes for wearable supercapacitors, In: Electrochimica Acta296pp. 481-490 Elsevier

    Fibres made from different nanostructured carbons (carbon black (CB)), carbon nanotubes (CNT) and CB/CNT were successfully developed by wet-spinning. The variation of dispersion conditions (carbon nanomaterial concentration, dispersant/Carbon nanomaterial concentration ratio, CB/CNT concentration ratio, pH) resulted in different electrochemical performance for each type of fibres. Fibres with the best capacitance values (10 F g-1) and good cycling stability (89%) were obtained from fibres containing 10% carbon black and 90% carbon nanotubes. A solid-state supercapacitor was fabricated by assembling the CB/CNT fibres resulting in 9.2 F g-1 electrode capacitance. Incorporation of 0.2 wt.% birnessite-type potassium manganese oxide nanotubes dramatically increased the capacitance of the fibres up to 246 F g-1 due to the high specific capacitance of birnessite phase and the tubular nature of the nanomaterial.

    Khaled Alqurashi, James R. Kelly, Zhengpeng Wang, Carol Crean, Raj Mittra, Mohsen Khalily, Yue Gao (2020)Liquid Metal Bandwidth-Reconfigurable Antenna, In: IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS19(1)pp. 218-222 Institute of Electrical and Electronics Engineers

    This letter shows how slugs of liquid metal can be used to connect/disconnect large areas of metalization and achieve a radiation performance not possible by using conventional switches. The proposed antenna can switch its operating bandwidth between ultrawideband and narrowband by connecting/disconnecting the ground plane for the feedline from that of the radiator. This could be achieved by using conventional semiconductor switches. However, such switches provide point-like contacts. Consequently, there are gaps in electrical contact between the switches. Surface currents, flowing around these gaps, lead to significant back radiation. In this letter, the slugs of a liquid metal are used to completely fill the gaps. This significantly reduces the back radiation, increases the bore-sight gain, and produces a pattern identical to that of a conventional microstrip patch antenna. Specifically, the realized gain and total efficiency are increased by 2 dBi and 24%, respectively. The antenna has potential applications in wireless systems employing cognitive radio (CR) and spectrum aggregation.

    José García-Torres, Carol Crean (2018)Ternary composite solid-state flexible supercapacitor based on nanocarbons/manganese dioxide/PEDOT:PSS fibres, In: Materials & Design155pp. 194-202 Elsevier

    Flexible fibre supercapacitors were fabricated by wet-spinning from carbon nanotube/carbon black dispersions, followed by straightforward surface treatments to sequentially deposit MnO2 and PEDOT:PSS to make ternary composite fibres. Dip coating the fibres after the initial wet-spinning coagulation creates a simple solution-based continuous process to produce fibre-based energy storage. Well-controlled depositions were achieved and have been optimised at each stage to yield the highest specific capacitance. A single ternary composite fibre exhibited a specific capacitance of 351 F g−1. Two ternary composite fibre electrodes were assembled together in a parallel solid-state device, with polyvinyl alcohol/H3PO4 gel used as both an electrolyte and a separator. The assembled flexible device exhibited a high specific capacitance of 51.3 F g−1 with excellent both charge-discharge cycling (84.2% capacitance retention after 1000 cycles) and deformation cycling stability (82.1% capacitance retention after 1000 bending cycles).

    Mona N. Sweilam, John R. Varcoe, Carol Crean (2018)Fabrication and Optimization of Fiber-Based Lithium Sensor: A Step towards Wearable Sensors for Lithium Drug Monitoring in Interstitial Fluid, In: ACS Sensors3(9)pp. 1802-1810 American Chemical Society

    A miniaturized, flexible fiber-based lithium sensor was fabricated from low-cost cotton using a simple, repeatable dip-coating technique. This lithium sensor is highly suited for ready-to-use wearable applications and can be used directly without the preconditioning steps normally required with traditional ion-selective electrodes. The sensor has a stable, rapid and accurate response over a wide Li+ concentration range that spans over the clinically effective and the toxic concentration limits for lithium in human serum. The sensor is selective to Li+ in human plasma even in the presence of a high concentration of Na+ ions. This novel sensor concept represents a significant advance in wearable sensor technology which will target lithium drug monitoring from under the skin.

    Mona N. Sweilam, Sarah F. Cordery, Stella Totti, Eirini G. Velliou, Paola Campagnolo, John R. Varcoe, M. Begoña Delgado-Charro, Carol Crean (2020)Textile-based non-invasive lithium drug monitoring: a proof-of-concept study for wearable sensing, In: Biosensors and Bioelectronics150111897 Elsevier

    Flexible wearable chemical sensors are emerging tools which target diagnosis and monitoring of medical conditions. One of the potential applications of wearable chemical sensors is therapeutic drug monitoring for drugs that have a narrow therapeutic range such as lithium. We have investigated the possibility of developing a fibre-based device for non-invasive lithium drug monitoring in interstitial fluid. A flexible cotton-based lithium sensor was coupled with a carbon fibre-based reference electrode to obtain a potentiometric device. In vitro reverse iontophoresis experiments were performed to extract Li+ from under porcine skin by applying a current density of 0.4 mA cm-2 via two electrodes. Carbon fibre-based reverse iontophoresis electrodes were fabricated and used instead of a conventional silver wire-based version and comparable results were obtained. The fibre-based Li+ sensor and reference electrodes were capable of determining the Li+ concentration in samples collected via reverse iontophoresis and the results compared well to those obtained by ion chromatography. Additionally, biocompatibility of the used materials have been tested. Promising results were obtained which confirm the possibility of monitoring lithium in interstitial fluid using a wearable sensor.

    Arup Chakraborty, Ihtasham Salam, Mehdi Choolaei, Judy Yu-Ting Lee, Carol Crean, Daniel Keith Whelligan, Rachida Bance-Soualhi, John Varcoe (2023)Changes in permselectivity of radiation-grafted anion-exchange membranes with different cationic headgroup chemistries are primarily due to water content differences †, In: Materials Advances4pp. 2099-2105 Royal Society of Chemistry

    In a prior paper [Bance-Soualhi et al., J. Mater. Chem. A, 2021, 9, 22025], we showed that the crosslinking of radiation-grafted anion-exchange membranes (RG-AEM) was necessary to obtain high enough apparent permselectivities for use in applications such as (reverse)electrodialysis. However, a separate result in this prior study suggested that comparable AEMs (similar ion-exchange capacity, IEC, and backbone chemistry) with different cationic headgroups may yield different balances between permselectivity and conductivity. This short follow-up study compares the permselectivities and Cl À conductivities of a series of non-crosslinked RG-AEMs with either aliphatic quaternary ammonium headgroups (N-benzyl-N-methylpiperidinium, MPIP, and benzyltrimethylammonium, TMA) or aromatic cationic headgroups (N-benzylpyridinium, PYR, or 1-benzyl-2,3-dimethylimidazolium, DMI). We show that a change in the headgroup chemistry modified the permselectivity-conductivity balance of the RG-AEM, but this was primarily due to the different headgroups inducing varying intrinsic water contents: higher water content RG-AEMs yield lower permselectivites. As also expected from this water content observation, higher IEC variants yielded RG-AEMs with lower permselectivities. The addition of N,N,N 0 ,N 0-tetramethylhexane-1,6-diamine-(TMHDA)-based ionic crosslinking to a DMI-based RG-AEM also raised permselectivity, confirming the observation of the prior study also applies to aromatic headgroup RG-AEMs. In summary, high IEC AEMs containing imidazolium-type headgroups along with an optimal amount of ionic crosslinking could be promising and warrant more study (i.e. a comparison of RG-AEMs with cheaper, more scalable non-RG-analogues that contain these attributes).

    SUAD SAEED ALGHAMDI, S BENNETT, CAROL CREAN, Joydip Ghosh , Harry Gibbard, Robert Moss , Justin Reiss, Douglas Wolfe, PAUL JONATHAN SELLIN (2022)Polycrystalline Formamidinium Lead Bromide X-ray Detectors, In: Applied sciences12(4)2013 MDPI
    M Schulz, C Crean, R Brinkhuis, R.P Sear, J.L Keddie (2021)Determination of parameters for self-stratification in bimodal colloidal coatings using Raman depth profiling, In: Progress in Organic Coatings157106272 Elsevier B.V

    In waterborne mixtures of colloidal particles with differing sizes, the spontaneous stratification of one species of particle in a coating – driven by diffusiophoresis - offers the possibility to tailor the surface properties. However, despite strong research interest in stratification in recent years, the acceptable range of experimental parameters has not been fully explored, and the extent of stratification that is achievable has not yet been quantified. Here, we study the stratification of bimodal mixtures of waterborne polyurethane particles mixed with larger acrylic particles. We use ultra-low angle microtoming to prepare cross-sections of coating samples and analyse compositions quantitatively with Raman mapping. We use this method to obtain high-resolution depth profiles of the polyurethane phase in the coating with spacing between measurements corresponding to a few tens of nm. We experimentally test a model of diffusiophoresis and observe stratification when the processing parameters (evaporation rates, film thickness, and volume fraction of small particles) fall within the required range. Samples that exhibit stratification have top layer thicknesses on the order of tens of μm, which is a significant depth for exploitation in coatings aiming to modify surface properties. To guide the design of coatings in applications, we draw on the model to define the range of parameters in which self-stratification is expected. Our results provide a fundamental understanding that will enable the fabrication of tailored coatings in which the properties of the surface differ from the bulk material.

    Sutthima Sriprasertsuk, Simone C. Mathias, John R. Varcoe, Carol Crean (2021)Polypyrrole-coated carbon fibre electrodes for paracetamol and clozapine drug sensing, In: Journal of Electroanalytical Chemistry897115608 Elsevier

    Polypyrrole (PPy) fibre electrodes were studied to determine their ability to sense paracetamol (as a model drug) in the presence of the interferents dopamine and ascorbic acid. PPy was electropolymerised onto carbon fibres using cyclic voltammetry in the presence of two different counter anions: sodium dodecyl sulfate (SDS) and potassium nitrate (KNO3). The surface of the PPy.SDS and PPy.KNO3 fibre electrodes was characterised using Raman spectroscopy and scanning electron microscopy. The PPy.SDS-coated carbon fibre had a 14-fold larger electrochemical surface area compared to a bare carbon fibre (calculated using the Randles-Sevcik equation). The use of a large counter anion as dopant (dodecyl sulfate) produced fibres with a greater drug sensing response (cf. the use of smaller nitrate anion). The use of the PPy.SDS fibre electrode in differential pulse voltammetry (DPV) allowed sensing of paracetamol with a detection limit (3σ S/N) of 34 µM. For the anodic peak current (0.5 V vs. Ag/AgCl), a linear response range was observed for 50–500 µM. At a paracetamol concentration of 100 µM, the DPV anodic peak current (at 0.5 V vs. Ag/AgCl) was unaffected by the addition of interferents: 100 µM dopamine and 100 µM ascorbic acid. A real-world application of drug sensing was trialled with the anti-psychotic medication clozapine; where the PPy.SDS carbon fibre could sense clozapine with a detection limit of (3σ S/N) of 6 µM and a sensitivity of 15 μA cm−2 μmol−1 L.

    Isabel Helen Balbir Braddock, Maya Al Sid Cheikh, Joydip Ghosh, Roma Eve Mulholland, Joseph Gerard O'Neill, Vlad Stolojan, Carol Crean, Stephen Sweeney, Paul Jonathan Sellin (2022)Formamidinium Lead Halide Perovskite Nanocomposite Scintillators, In: Nanomaterials (Basel, Switzerland)12(13) Mdpi

    While there is great demand for effective, affordable radiation detectors in various applications, many commonly used scintillators have major drawbacks. Conventional inorganic scintillators have a fixed emission wavelength and require expensive, high-temperature synthesis; plastic scintillators, while fast, inexpensive, and robust, have low atomic numbers, limiting their X-ray stopping power. Formamidinium lead halide perovskite nanocrystals show promise as scintillators due to their high X-ray attenuation coefficient and bright luminescence. Here, we used a room-temperature, solution-growth method to produce mixed-halide FAPbX(3) (X = Cl, Br) nanocrystals with emission wavelengths that can be varied between 403 and 531 nm via adjustments to the halide ratio. The substitution of bromine for increasing amounts of chlorine resulted in violet emission with faster lifetimes, while larger proportions of bromine resulted in green emission with increased luminescence intensity. By loading FAPbBr(3) nanocrystals into a PVT-based plastic scintillator matrix, we produced 1 mm-thick nanocomposite scintillators, which have brighter luminescence than the PVT-based plastic scintillator alone. While nanocomposites such as these are often opaque due to optical scattering from aggregates of the nanoparticles, we used a surface modification technique to improve transmission through the composites. A composite of FAPbBr(3) nanocrystals encapsulated in inert PMMA produced even stronger luminescence, with intensity 3.8 x greater than a comparative FAPbBr(3)/plastic scintillator composite. However, the luminescence decay time of the FAPbBr(3)/PMMA composite was more than 3 x slower than that of the FAPbBr(3)/plastic scintillator composite. We also demonstrate the potential of these lead halide perovskite nanocomposite scintillators for low-cost X-ray imaging applications.

    MALIN SCHULZ, R Brinkhuis, CAROL CREAN, RICHARD PHILIP LLEWELLYN SEAR, JOSEPH LOUIS KEDDIE (2022)Suppression of self-stratification in colloidal mixtures with high Péclet numbers, In: Soft matter18(13)pp. 2512-2516 RSC

    The non-equilibrium assembly of bimodal colloids during evaporative processes is an attractive means to achieve gradient or stratified layers in thick films. Here, we show that the stratification of small colloids on top of large is prevented when the viscosity of the continuous aqueous phase is too high. We propose a model where a too narrow width of the gradient in concentration of small colloids suppresses the stratification.

    James B Robinson, Kai Xi, Vasant Kumar, Andrea C Ferrari, Heather Au, Maria-Magdalena Titirici, Andres Parra-Puerto, Anthony R Kucernak, Samuel D S Fitch, Nuria Garcia-Araez, Zachary L Brown, Mauro Pasta, Liam Furness, Alexander J Kibler, Darren A Walsh, Lee R Johnson, Conrad Holc, Graham N Newton, Neil R Champness, Foivos Markoulidis, Carol Crean, Robert C T Slade, Eleftherios I Andritsos, Qiong Cai, Shumaila Babar, Teng Zhang, Constantina Lekakou, Nivedita Kulkarni, Alexander J E Rettie, Rhodri Jervis, Michael Cornish, Monica Marinescu, Gregory Offer, Zhuangnan Li, Liam Bird, Clare P Grey, Manish Chhowalla, Daniele Di Lecce, Rhodri E Owen, Thomas S Miller, Dan J L Brett, Sebastien Liatard, David Ainsworth, Paul R Shearing (2022)2021 roadmap on lithium sulfur batteries, In: JPhys Energy3(3)031501 IOP Publishing

    Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space.

    Ahmad I. Ayesh, SUAD SAEED ALGHAMDI, Belal Salah, S.H. Bennett, CAROL CREAN, PAUL JONATHAN SELLIN (2022)High sensitivity H2S gas sensors using lead halide perovskite nanoparticles, In: Results in physics35105333 Elsevier
    WILLIAM LOCKLEY, Carol Crean, John R Varcoe Modern Raman spectromicroscopy: Some early investigations with deuterated compounds, In: JOURNAL OF LABELLED COMPOUNDS & RADIOPHARMACEUTICALS5pp. 465-466 Wiley

    Raman spectroscopy is used less commonly than other spectroscopic techniques by isotopic chemists. The University of Surrey has recently become a regional centre for the technique following our acquisition of a powerful high-resolution multi-laser Raman spectromicroscope (Renishaw inVia, model RE04, via EPSRC grant EP/M022749/1). This poster reports some early experience with the technique as applied to the analysis of deuterated compounds. The spectrometer is based around Raman scattering from any of five lasers ranging from the ultraviolet to blue, green, red and near infrared (244–785 nm). The sampling beam has an area of just 2-10µm and hence the spectrometer has the ability to automatically scan tiny sample areas, offering the possibility of obtaining Raman imaging for 2-D and (via confocality) even 3-D samples. Investigations into isotopic applications of these multidimensional abilities are in progress.  The high resolution of the system also enables excellent spectra to be recorded from very tiny samples, e.g. from a small part of this 200µm crystal of [2H8]naphthalene.  The poster provides examples of the following advantages when deuterated compounds are analysed by Raman:Improved sensitivity is available via powerful lasers and digital spectral accumulationRapid generation of high quality one-dimensional Raman spectra from various sample typesLow matrix effects for glass enables direct analysis within ordinary sealed glass lab vialsHigh spectral and spacial resolution provides the ability to work with tiny samples/areasHighly specific results, as vibrational modes can be very sensitive to isotopic substitutionDirect quantitative analysis of isotopic mixtures is possible by selecting the appropriate peaksLow background from silicagel means TLC & HPTLC applications are possibleSurface enhanced Raman spectra (SERS) can be simply obtained via stable silver colloids

    N Gilmartin, C Crean (2014)Nanoparticle technologies in detection science, In: RSC Detection Science2014-J(3)pp. 116-141
    C Crean, C Mcgeough, R O'Kennedy (2012)Wearable biosensors for medical applications, In: Biosensors for Medical Applicationspp. 301-330 Woodhead Publishing

    Over the past decade, the design and development of wearable sensors for biomedical applications has garnered considerable attention in the scientifi c community and in industry. This chapter aims to review research conducted into wearable sensors for healthcare monitoring. Acceptance of this approach in observation of physiological data depends strongly on the cost, wearability, usability and performance of such devices. An outline of body sensor network systems (and applications of wearable computing devices) is provided with a summary of electronic textiles. A synopsis of the clinical applications of this type of technology is given at the end of the chapter © 2012 Woodhead Publishing Limited All rights reserved.

    C.S. Nagi, S.L. Ogin, I. Mohagheghian, C. Crean, A.D. Foreman (2018)Interlaminar Toughening of Carbon Fibre Reinforced Polymers using Graphene / Thermoplastic Inserts, In: Proceedings of ECCM 18 - 18th European Conference on Composite Materials European Society for Composite Materials

    This paper outlines preliminary work developing graphene modified thermoplastic inserts to be used for the toughening of CFRP. The paper outlines laminate manufacture, mechanical testing and fracture analysis of graphene modified CFRP.

    Khaled Yahya Alqurashi, Carol Crean, James R. Kelly, Tim W. C. Brown, Mohsen Khalily (2019)Liquid Metal Application for Continuously Tunable Frequency Reconfigurable Antenna, In: Proceedings of the 13th European Conference on Antennas and Propagation (EuCAP 2019) Institute of Electrical and Electronics Engineers (IEEE)

    This paper presents two different designs for frequency reconfigurable antennas capable of continuous tuning. The radiator, for both antenna designs, is a microstrip patch, formed from liquid metal, contained within a microfluidic channel structure. Both patch designs are aperture fed. The microfluidic channel structures are made from polydimethylsiloxane (PDMS). The microfluidic channel structure for the first design has a meander layout and incorporates rows of posts. The simulated antenna provides a frequency tuning range of approximately 118% (i.e. 4.36 GHz) over the frequency range from 1.51 GHz to 5.87 GHz. An experimental result for the fully filled case shows a resonance at 1.49 GHz (1.3% error compared with the simulation). Experienced rheological behavior of the liquid metal necessitates microfluidic channel modifications. For that reason, we modified the channel structure used to realise the radiating patch for the second design. Straight channels are implemented in the second microfluidic device. According to simulation the design yields a frequency tuning range of about 77% (i.e. 3.28 GHz) from 2.62 GHz to 5.90 GHz.