Imperial College London

DrThomasMacdonald

Faculty of Natural SciencesDepartment of Chemistry

Research Associate
 
 
 
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t.macdonald

 
 
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Molecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
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42 results found

Lin C-T, Ngiam J, Xu S, Chang Y-H, Du T, Macdonald TJ, Durrant J, McLachlan Met al., 2020, Enhancing the operational stability of unencapsulated perovskite solar cells through Cu-Ag bilayer electrode incorporation, Journal of Materials Chemistry A, Vol: 8, Pages: 8684-8691, ISSN: 2050-7488

We identify a facile strategy that significantly reduces electrode corrosion and device degradation in unencapsulated perovskite solar cells (PSCs) operating in ambient air. By employing Cu-Ag bilayer top electrodes PSCs, we show enhanced operational lifetime compared with devices prepared from single metal (Al, Ag and Cu) analogues. Time-of-flight secondary ion mass spectrometry depth profiles indicate that the insertion of the thin layer of Cu (10nm) below the Ag (100nm) electrode significantly reduces diffusion of species originating in the perovskite active layer into the electron transport layer and electrode. X-ray diffraction (XRD) analysis reveals the mutually beneficial relationship between the bilayer metals, whereby the thermally evaporated Ag inhibits Cu oxidation and the Cu prevents interfacial reactions between the perovskite and Ag. The results here not only demonstrate a simple approach to prevent the electrode and device degradation that enhance lifetime and stability but also give an insight into ageing related ion migration and structural reorganisation.

Journal article

Portnoi M, Macdonald TJ, Sol C, Robbins TS, Li T, Schlafer J, Guldin S, Parkin IP, Papakonstantinou Iet al., 2020, All-Silicone-based distributed bragg reflectors for efficient flexible luminescent solar concentrators, Nano Energy, Vol: 70, Pages: 1-9, ISSN: 2211-2855

Luminescent Solar Concentrators (LSCs) have drawn huge interest recently as a technology to pave the way towards the seamless integration of photovoltaics to a range of high-value industries; from architecture and sports to leisure and consumer electronics. Additional device flexibility comes with the inherent ability to attain freeform shapes, expanding the possible fabrication methods, applications and retro-fitting techniques. Unfortunately, flexible LSCs suffer from curvature induced losses which can severely reduce their efficiency, inhibiting the potential of large-scale devices. In this work, we experimentally demonstrate an all-silicone based flexible LSC and Distributed Bragg Reflector (DBR) combination diminishing curvature induced losses. The DBRs, fabricated using scalable solution-based processes, exhibit optical properties precisely engineered to partner our LSCs, as well as high uniformity, resistance to temperature and curvature. Comprehensive modelling shows that for large-scale devices (1 m2) we can essentially decouple the performance of the LSC from curvature, steering the technology towards commercial viability.

Journal article

Hopper TR, Gorodetsky A, Jeong A, Krieg F, Bodnarchuk MI, Maimaris M, Chaplain M, Macdonald TJ, Huang X, Lovrincic R, Kovalenko MV, Bakulin AAet al., 2020, Hot carrier dynamics in perovskite nanocrystal solids: role of the cold carriers, nanoconfinement and the surface, Nano Letters, Vol: 20, Pages: 2271-2278, ISSN: 1530-6984

Carrier cooling is of widespread interest in the field of semiconductor science. It is linked to carrier-carrier and carrier-phonon coupling, and has profound implications for the photovoltaic performance of materials. Recent transient optical studies have shown that a high carrier density in lead-halide perovskites (LHPs) can reduce the cooling rate through a “phonon bottleneck”. However, the role of carrier-carrier interactions, and the material properties that control cooling in LHPs, are still disputed. To address these factors, we utilize ultrafast “pump-push-probe” spectroscopy on LHP nanocrystal (NC) films. We find that the addition of cold carriers to LHP NCs increases the cooling rate, competing with the phonon bottleneck. By comparing different NCs and bulk samples, we deduce that the cooling behavior is intrinsic to the LHP composition, and independent of the NC size or surface. This can be contrasted with other colloidal nanomaterials, where confinement and trapping considerably influence the cooling dynamics.

Journal article

Lin C-T, Lee J, Kim J, Macdonald TJ, Ngiam J, Xu B, Daboczi M, Xu W, Pont S, Park B, Kang H, Kim J-S, Payne DJ, Lee K, Durrant JR, McLachlan MAet al., 2020, Origin of open-circuit voltage enhancements in planar Perovskite solar cells induced by addition of bulky organic cations, Advanced Functional Materials, Vol: 30, ISSN: 1616-301X

The origin of performance enhancements in p‐i‐n perovskite solar cells (PSCs) when incorporating low concentrations of the bulky cation 1‐naphthylmethylamine (NMA) are discussed. A 0.25 vol % addition of NMA increases the open circuit voltage (Voc) of methylammonium lead iodide (MAPbI3) PSCs from 1.06 to 1.16 V and their power conversion efficiency (PCE) from 18.7% to 20.1%. X‐ray photoelectron spectroscopy and low energy ion scattering data show NMA is located at grain surfaces, not the bulk. Scanning electron microscopy shows combining NMA addition with solvent assisted annealing creates large grains that span the active layer. Steady state and transient photoluminescence data show NMA suppresses non‐radiative recombination resulting from charge trapping, consistent with passivation of grain surfaces. Increasing the NMA concentration reduces device short‐circuit current density and PCE, also suppressing photoluminescence quenching at charge transport layers. Both Voc and PCE enhancements are observed when bulky cations (phenyl(ethyl/methyl)ammonium) are incorporated, but not smaller cations (Cs/MA)—indicating size is a key parameter. Finally, it demonstrates that NMA also enhances mixed iodide/bromide wide bandgap PSCs (Voc of 1.22 V with a 1.68 eV bandgap). The results demonstrate a facile approach to maximizing Voc and provide insights into morphological control and charge carrier dynamics induced by bulky cations in PSCs.

Journal article

Ambroz F, Xu W, Gadipelli S, Brett DJL, Lin C-T, Contini C, McLachlan MA, Durrant JR, Parkin IP, Macdonald TJet al., 2019, Room Temperature Synthesis of Phosphine-Capped Lead Bromide Perovskite Nanocrystals without Coordinating Solvents, PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Vol: 37, ISSN: 0934-0866

Journal article

Macdonald TJ, Batmunkh M, Lin C-T, Kim J, Tune DD, Ambroz F, Li X, Xu S, Sol C, Papakonstantinou I, McLachlan MA, Parkin IP, Shapter JG, Durrant JRet al., 2019, Origin of performance enhancement in TiO2-carbon nanotube composite perovskite solar cells, Small Methods, Vol: 3, Pages: 1-10, ISSN: 2366-9608

Carbon nanotubes are shown to be beneficial additives to perovskite solar cells, and the inclusion of such nanomaterials will continue to play a crucial role in the push toward developing efficient and stable device architectures. Herein, titanium dioxide/carbon nanotube composite perovskite solar cells are fabricated, and device performance parameters are correlated with spectroscopic signatures of the materials to understand the origin of performance enhancement. By probing the charge carrier dynamics with photoluminescence and femtosecond transient absorption spectroscopy, the results indicate that charge transfer is not improved by the presence of the carbon nanotubes. Instead, carbon nanotubes are shown to passivate the electronic defect states within the titanium dioxide, which can lead to stronger radiative recombination in the titanium dioxide/carbon nanotube films. The defect passivation allows the perovskite solar cells made using an optimized titanium dioxide/carbon nanotube composite to achieve a peak power conversion efficiency of 20.4% (19% stabilized), which is one of the highest values reported for perovskite solar cells not incorporating a mixed cation light absorbing layer. The results discuss new fundamental understandings for the role of carbon nanomaterials in perovskite solar cells and present a significant step forward in advancing the field of high‐performance photovoltaics.

Journal article

Ambroz F, Donnelly JL, Wilden JD, Macdonald TJ, Parkin IPet al., 2019, Carboxylic Acid Functionalization at the Meso-Position of the Bodipy Core and Its Influence on Photovoltaic Performance., Nanomaterials (Basel), Vol: 9, ISSN: 2079-4991

Two bodipy dyes with different carboxylic acids on the meso-position of the bodipy core were prepared and used to sensitize TiO2 photoelectrodes. On the basis of spectroscopic characterization, the photoelectrodes were used to fabricate photoelectrochemical cells (PECs) for solar light harvesting. Photovoltaic measurements showed that both bodipy dyes successfully sensitized PECs with short-circuit current densities (JSC) two-fold higher compared to the control. The increase in generated current was attributed to the gain in spectral absorbance due to the presence of bodipy. Finally, the influence of co-sensitization of bodipy and N719 dye was also investigated and photovoltaic device performance discussed.

Journal article

Schläefer J, Sol C, Li T, Malarde D, Portnoi M, Macdonald TJ, Laney SK, Powell MJ, Top I, Parkin IP, Papakonstantinou Iet al., 2019, Thermochromic VO2−SiO2 nanocomposite smart window coatings with narrow phase transition hysteresis and transition gradient width, Solar Energy Materials and Solar Cells, Vol: 200, Pages: 1-7, ISSN: 0927-0248

Thermochromic vanadium dioxide (VO2) window coatings hold the promise of reducing the energy consumption of the built environment by passively regulating solar heat gain in response to changing conditions. Composite materials with embedded VO2 particles have shown greatly improved optical performances compared with thin films, however they typically exhibit broadened phase transition hysteresis and gradient widths, which negatively impacts the overall performance. Here, we present a scalable one-step solution based synthesis for a thermochromic smart window coating based on a vanadium dioxide sol-gel containing silica (SiO2 nanoparticles. We compare the performance of our nanoparticle composite with thin film VO2 along with composites formed by mixing VO2 and SiO2 sol-gels and find that both composites achieve an acceptable visible transmittance ( 50%) along with a comparable and competitive solar modulation (12.5% and 16.8% respectively), roughly double that of the plain VO2 film (6.7%). However, our SiO2 nanoparticle containing composite also benefits from a narrow transition hysteresis and gradient width (9.4 ∘C and 2.9 ∘C respectively). We predict that this method may subsequently be combined with metal ion doping to control both the optical and phase transition characteristics to achieve composite films with high overall energy saving performances.

Journal article

Ambroz F, Sathasivam S, Lee R, Gadipelli S, Lin C, Xu S, Poduval RK, Mclachlan MA, Papakonstantinou I, Parkin IP, Macdonald TJet al., 2019, Influence of lithium and lanthanum treatment on TiO2 nanofibers and their application in n‐i‐p solar cells, ChemElectroChem, Vol: 6, Pages: 3590-3598, ISSN: 2196-0216

The addition of cations to TiO2 photoelectrodes is routinely accepted as a route to enhance the performance of conventional n‐i‐p solar cells. However, this is typically achieved in multiple steps or by the incorporation of expensive and hydroscopic cationic precursors such as lithium bis(trifluoromethanesulfonyl)imide. In addition, it is often unclear as to whether the incorporation of such cation sources is inducing “doping” or simply transformed into cationic oxides on the surface of the photoelectrodes. In this study, TiO2 nanofibers were produced through a simple electrospinning technique and modified by introducing lithium and lanthanum precursors in one step. Our results show that the addition of both cations caused minimal substitutional or interstitial doping of TiO2. Brunauer‐Emmett‐Teller measurements showed that lanthanum‐treated TiO2 nanofibers had an increase in surface area, which even exceeded that of TiO2 P25 nanoparticles. Finally, treated and untreated TiO2 nanofibers were used in n‐i‐p solar cells. Photovoltaic characteristics revealed that lanthanum treatment was beneficial, whereas lithium treatment was found to be detrimental to the device performance for both dye‐sensitized and perovskite solar cells. The results discuss new fundamental understandings for two of the commonly incorporated cationic dopants in TiO2 photoelectrodes, lithium and lanthanum, and present a significant step forward in advancing the field of materials chemistry for photovoltaics.

Journal article

Peveler WJ, Jia H, Jeen T, Rees K, Macdonald TJ, Xia Z, Chio W-IK, Moorthy S, Parkin IP, Carmalt CJ, Algar WR, Lee T-Cet al., 2019, Cucurbituril- mediated quantum dot aggregates formed by aqueous self- assembly for sensing applications, Chemical Communications, Vol: 55, Pages: 5495-5498, ISSN: 1359-7345

Self-assembled nanoparticles have important applications in energy systems, optical devices and sensors, via the formation of aggregates with controlled interparticle spacing. Here we report aqueous self-assembly of rigid macrocycle cucurbit[7]uril (CB[7]) and fluorescent quantum dots (QDs), and demonstrate the potential of the system for efficient energy transfer and sensing of small molecules.

Journal article

Batmunkh M, Vimalanathan K, Wu C, Bati ASR, Yu L, Tawfik SA, Ford MJ, Macdonald TJ, Raston CL, Priya S, Gibson CT, Shapter JGet al., 2019, Efficient production of phosphorene nanosheets via shear stress mediated exfoliation for low‐temperature perovskite solar cells, Small Methods, Vol: 3, Pages: 1-8, ISSN: 2366-9608

A simple and fast “top‐down” protocol is introduced herein to prepare solution processable few‐layer phosphorene nanosheets using vortex fluidic mediated exfoliation under near‐infrared (NIR) pulsed laser irradiation. This novel shear‐exfoliation method requires short processing times and produces highly crystalline, atomically thin phosphorene nanosheets (4.3 ± 0.4 nm). The as‐prepared phosphorene nanosheets are used as an effective electron transporting material (ETM) for low‐temperature processed, planar n‐i‐p perovskite solar cells (PSCs). With the addition of phosphorene, the average power conversion efficiency (PCE) increases from 14.32% to 16.53% with a maximum PCE of 17.85% observed for the phosphorene incorporated PSCs which is comparable to the devices made using the traditional high‐temperature protocol. Experimental and theoretical (density‐functional theory) investigations reveal the PCE improvements are due to the high carrier mobility and suitable band energy alignment of the phosphorene. The work not only paves the way for novel synthesis of 2D materials, but also opens a new avenue in using phosphorene as an efficient ETM in photovoltaic devices.

Journal article

Patrick PS, Bogart LK, Macdonald TJ, Southern P, Powell MJ, Zaw-Thin M, Voelcker NH, Parkin IP, Pankhurst QA, Lythgoe MF, Kalber TL, Bear JCet al., 2019, Surface radio-mineralisation mediates chelate-free radiolabelling of iron oxide nanoparticles, Chemical Science, Vol: 10, Pages: 2592-2597, ISSN: 2041-6520

We introduce the concept of surface radio-mineralisation (SRM) to describe the chelate-free radiolabelling of iron-oxide and ferrite nanoparticles. We demonstrate the effectiveness of SRM with both 111In and 89Zr for bare, polymer-matrix multicore, and surface-functionalised magnetite/maghemite nanoparticles; and for bare Y3Fe5O12 nanoparticles. By analogy with geological mineralisation (the hydrothermal deposition of metals as minerals in ore bodies or lodes) we demonstrate that the heat-induced and aqueous SRM process deposits radiometal-oxides onto the nanoparticle or core surfaces, passing through the matrix or coating if present, without changing the size, structure, or magnetic properties of the nanoparticle or core. We show in a mouse model followed over 7 days that the SRM is sufficient to allow quantitative, non-invasive, prolonged, whole-body localisation of injected nanoparticles with nuclear imaging.

Journal article

Elmas S, Macdonald TJ, Skinner W, Andersson M, Nann Tet al., 2019, Copper Metallopolymer Catalyst for the Electrocatalytic Hydrogen Evolution Reaction (HER), Polymers, Vol: 11, Pages: 1-11, ISSN: 2073-4360

Conjugated polymers with stabilizing coordination units for single-site catalytic centers are excellent candidates to minimize the use of expensive noble metal electrode materials. In this study, conjugated metallopolymer, POS[Cu], was synthesized and fully characterized by means of spectroscopical, electrochemical, and photophysical methods. The copper metallopolymer was found to be highly active for the electrocatalytic hydrogen generation (HER) in an aqueous solution at pH 7.4 and overpotentials at 300 mV vs. reversible hydrogen electrode (RHE). Compared to the platinum electrode, the obtained overpotential is only 100 mV higher. The photoelectrochemical tests revealed that the complexation of the conjugated polymer POS turned its intrinsically electron-accepting (p-type) properties into an electron-donor (n-type) with photocurrent responses ten times higher than the organic photoelectrode.

Journal article

Peveler WJ, Packman H, Alexander S, Chauhan RR, Hayes LM, Macdonald TJ, Cockcroft JK, Rogers S, Aarts DGAL, Carmalt CJ, Parkin IP, Bear JCet al., 2018, A new family of urea-based low molecular-weight organogelators for environmental remediation: the influence of structure, Soft Matter, Vol: 14, Pages: 8821-8827, ISSN: 1744-683X

Gelation processes grant access to a wealth of soft materials with tailorable properties, in applications as diverse as environmental remediation, biomedicine and electronics. Several classes of self-assembling gelators have been studied and employ non-covalent bonds to direct assembly, but recently attention has come to focus on how the overall shape of the gelator molecule impacts its gelation. Here we study a new sub-family of low molecular weight organogelators and explore how steric rearrangement influences their gelation. The gels produced are characterised with X-ray diffraction and small-angle neutron scattering (SANS) to probe their ex situ and in situ gelation mechanisms. The best examples were then tested for environmental remediation applications, gelling petrol and oils in the presence of water and salts.

Journal article

Ambroz F, Macdonald TJ, Martis V, Parkin IPet al., 2018, Evaluation of the BET theory for the characterization of meso and microporous MOFs, Small Methods, Vol: 2, Pages: 1-17, ISSN: 2366-9608

Surface area determination with the Brunauer–Emmett–Teller (BET) method is a widely used characterization technique for metal–organic frameworks (MOFs). Since these materials are highly porous, the use of the BET theory can be problematic. Several researchers have evaluated the BET method to gain insights into the usefulness of the obtained results and interestingly, their findings are not always consistent. In this review, the suitability of the BET method is discussed for MOFs that have a diverse range of pore widths below the diameters of N2 or Ar and above 20 Å. In addition, the surface area of MOFs that are obtained by implementing different approaches, such as grand canonical Monte Carlo simulations, calculations from the crystal structures or based on experimental N2, Ar, or CO2 adsorption isotherms, are compared and evaluated. Inconsistencies in the state‐of‐the‐art are also noted. Based on the current literature, an overview is provided of how the BET method can give useful estimations of the surface areas for the majority of MOFs, but there are some crucial and specific exceptions which are highlighted in this review.

Journal article

Lourenco C, Macdonald TJ, Gavriilidis A, Allan E, MacRobert AJ, Parkin IPet al., 2018, Effects of bovine serum albumin on light activated antimicrobial surfaces, RSC Advances: an international journal to further the chemical sciences, Vol: 8, Pages: 34252-34258, ISSN: 2046-2069

Bovine serum albumin (BSA) is currently recommended as an interfering substance to emulate organic soiling, in evaluating the efficacy of disinfectants. The European Standard recommends 0.03% BSA to test clean conditions and 0.3% for dirty conditions. Reactive oxygen species are known to exert excellent antimicrobial activity with low specificity against a broad range of pathogens. Herein, we present our data from the first study of the effects of the addition of BSA on the antibacterial activity of light activated antimicrobial surfaces. Light activated antimicrobial surfaces were made from polyurethane swell-encapsulated with gold nanoparticles (AuNPs) coated with the light active triarylmethane dye, crystal violet (PU-AuNP-CV). The antibacterial efficacy of the antimicrobial substrates was tested against two strains of Staphylococcus aureus 8325-4, a well-characterised laboratory strain and MRSA 4742, a recent clinical isolate, in the presence of 0.1% to 1% BSA by irradiating the substrates with a fluorescent lamp (300 lux). After 6 hours of irradiation, the number of surviving bacteria was determined. The results showed that BSA reduced the antibacterial efficacy of all the PU-AuNP-CV surfaces with increasing BSA concentrations resulting in a progressive reduction in antibacterial activity towards the bacteria tested. However, the light activated surfaces did perform well at 0.1 and 0.25% BSA levels, showing they may have potential for real world environments with low levels of organic soiling.

Journal article

Macdonald TJ, Ambroz F, Batmunkh M, Li Y, Kim D, Contini C, Poduval R, Liu H, Shapter JG, Papakonstantinou I, Parkin IPet al., 2018, TiO2 nanofiber photoelectrochemical cells loaded with sub-12 nm AuNPs: size dependent performance evaluation, Materials Today Energy, Vol: 9, Pages: 254-263, ISSN: 2468-6069

Incorporation of gold nanoparticles (AuNPs) into titanium dioxide (TiO2) photoelectrodes has been used traditionally to increase the performance of photoelectrochemical cells (PECs) through their tailored optical properties. In contrast to larger AuNPs, previous studies have suggested that smaller AuNPs are the most catalytic or effective at increasing the photovoltaic (PV) performance of TiO2 photoelectrodes based on PECs. Despite this, AuNPs are often only compared between sizes of 12–300 nm in diameter due to the most common synthesis, the Turkevich method, being best controlled in this region. However, the optimum radius for citrate-capped AuNPs sized between 5 and 12 nm, and their influence on the PV performances has not yet been investigated. In addition to using AuNPs in the photoelectrodes, replacing traditional TiO2 NPs with one-dimensional nanofibers (NFs) is a promising strategy to enhance the PV efficiency of the PECs due their capability to provide a direct pathway for charge transport. Herein, we exploit the advantages of two different nanostructured materials, TiO2 NFs and sub-12 nm AuNPs (5, 8, 10, and 12 nm), and fabricate composite based photoelectrodes to conduct a size dependent performance evaluation. The PECs assembled with 8 nm AuNPs showed ∼20% improvement in the average power conversion efficiency compared to the control PECs without AuNPs. The highest performing PEC achieved a power conversion efficiency of 8%, which to the best of our knowledge, is among the highest reported for scattering layers based on pure anatase TiO2 NFs. On the basis of our comprehensive investigations, we attribute this enhanced device performance using 8 nm AuNPs in the TiO2 NF photoelectrodes to the improved spectral absorption, decreased series resistance, and an increase in electron transport and injection rate leading to an increase in current density and fill factor.

Journal article

McInnes S, Macdonald T, Parkin I, Nann T, Voelcker Net al., 2018, Electrospun composites of polycaprolactone and porous silicon nanoparticles for the tunable delivery of small therapeutic molecules, Nanomaterials, Vol: 8, Pages: 205-205, ISSN: 2079-4991

This report describes the use of an electrospun composite of poly(ε-caprolactone) (PCL) fibers and porous silicon (pSi) nanoparticles (NPs) as an effective system for the tunable delivery of camptothecin (CPT), a small therapeutic molecule. Both materials are biodegradable, abundant, low-cost, and most importantly, have no known cytotoxic effects. The composites were treated with and without sodium hydroxide (NaOH) to investigate the wettability of the porous network for drug release and cell viability measurements. CPT release and subsequent cell viability was also investigated. We observed that the cell death rate was not only affected by the addition of our CPT carrier, pSi, but also by increasing the rate of dissolution via treatment with NaOH. This is the first example of loading pSi NPs as a therapeutics nanocarrier into electronspun PCL fibers and this system opens up new possibilities for the delivery of molecular therapeutics.

Journal article

Seo DH, Batmunkh M, Fang J, Murdock AT, Yick S, Han Z, Shearer CJ, Macdonald TJ, Lawn M, Bendavid A, Shapter JG, Ken Ostrikov Ket al., 2018, Ambient air synthesis of multi-layer CVD graphene films for low-cost, efficient counter electrode material in dye-sensitized solar cells, FlatChem, Vol: 8, Pages: 1-8, ISSN: 2452-2627

Graphene holds great promise as a substitute counter electrode (CE) material to replace the conventional Pt in dye-sensitized solar cells (DSSCs). However, lengthy chemical processing with hazardous chemicals, high production cost and the poor quality of the graphene flakes produced impedes their utilization as a CE material in DSSCs. Herein, we demonstrate a low-cost synthesis of multi-layer graphene films using a thermal chemical vapour deposition (CVD) process in an ambient-air environment without expensive compressed gases while using a renewable source namely soybean oil. Utilization of our low-cost graphene film in DSSCs exhibits excellent electrocatalytic activity and high electrical conductivity, and thus delivers superior photovoltaic (PV) efficiency compared to the devices fabricated with graphene films produced from commonly adopted chemical methods. Even though no additional treatments such as heteroatom doping are applied, our low-cost graphene showed great promise in DSSCs. Further enhancement in the efficiency of our multi-layer graphene film based DSSCs is readily achievable by applying simple functional treatments (for example SOCl2). Finally, material cost analysis of our multi-layer graphene film compared to commercial Pt electrode suggests that we can reduce the CE material cost by five fold, making our CVD graphene film a realistic option for application in commercial DSSC systems.

Journal article

Batmunkh M, Macdonald TJ, Peveler WJ, Bati ASR, Carmalt CJ, Parkin IP, Shapter JGet al., 2017, Plasmonic gold nanostars incorporated into high-efficiency perovskite solar cells, ChemSusChem: chemistry and sustainability, energy and materials, Vol: 10, Pages: 3750-3753, ISSN: 1864-5631

Incorporating appropriate plasmonic nanostructures into photovoltaic (PV) systems is of great utility for enhancing photon absorption and thus improving device performance. Herein, the successful integration of plasmonic gold nanostars (AuNSs) into mesoporous TiO2 photoelectrodes for perovskite solar cells (PSCs) is reported. The PSCs fabricated with TiO2‐AuNSs photoelectrodes exhibited a device efficiency of up to 17.72 %, whereas the control cells without AuNSs showed a maximum efficiency of 15.19 %. We attribute the origin of increased device performance to enhanced light absorption and suppressed charge recombination.

Journal article

Poduval RK, Noimark S, Colchester R, Macdonald T, Parkin IP, Desjardins A, Papakonstantinou Iet al., 2017, Optical fiber laser ultrasound transmitter with electrospun composite for minimally invasive medical imaging, Opto-Acoustic Methods and Applications in Biophotonics III, Publisher: SPIE

Conference paper

Ambroz F, Macdonald TJ, Nann T, 2017, Trends in aluminium-based intercalation batteries, Advanced Energy Materials, Vol: 7, Pages: 1-16, ISSN: 1614-6832

Over the last decade, optimizing energy storage has become significantly important in the field of energy conversion and sustainability. As a result of immense progress in the field, cost‐effective and high performance batteries are imperative to meeting the future demand of sustainability. Currently, the best performing batteries are lithium‐ion based, but limited lithium (Li) resources make research into alternatives essential. In recent years, the performance of aluminium‐ion batteries has improved remarkably in all battery‐relevant metrics, which renders them a promising alternative. Compared with monovalent Li‐ion batteries, aluminium (Al) cations can carry three positive charges, which could result in higher energy densities. This review describes recent developments in Al‐based cathode materials. The major goal of this review is to highlight strengths and weaknesses of various different approaches and provide guidelines for future research.

Journal article

Canever N, Hughson F, Macdonald TJ, Nann Tet al., 2017, Electrospinning of Photocatalytic Electrodes for Dye-sensitized Solar Cells., J Vis Exp

This work demonstrates a protocol to fabricate a fiber-based photoanode for dye-sensitized solar cells, consisting of a light-scattering layer made of electrospun titanium dioxide nanofibers (TiO2-NFs) on top of a blocking layer made of commercially available titanium dioxide nanoparticles (TiO2-NPs). This is achieved by first electrospinning a solution of titanium (IV) butoxide, polyvinylpyrrolidone (PVP), and glacial acetic acid in ethanol to obtain composite PVP/TiO2 nanofibers. These are then calcined at 500 °C to remove the PVP and to obtain pure anatase-phase titania nanofibers. This material is characterized using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The photoanode is prepared by first creating a blocking layer through the deposition of a TiO2-NPs/terpineol slurry on a fluorine-doped tin oxide (FTO) glass slide using doctor blading techniques. A subsequent thermal treatment is performed at 500 °C. Then, the light-scattering layer is formed by depositing a TiO2-NFs/terpineol slurry on the same slide, using the same technique, and calcinating again at 500 °C. The performance of the photoanode is tested by fabricating a dye-sensitized solar cell and measuring its efficiency through J-V curves under a range of incident light densities, from 0.25-1 Sun.

Journal article

Poduval RK, Noimark S, Colchester RJ, Macdonald TJ, Parkin IP, Desjardins AE, Papakonstantinou Iet al., 2017, Optical fiber ultrasound transmitter with electrospun carbon nanotube-polymer composite, Applied Physics Letters, Vol: 110, Pages: 223701-1-223701-5, ISSN: 0003-6951

All-optical ultrasound transducers are promising for imaging applications in minimally invasive surgery. In these devices, ultrasound is transmitted and received through laser modulation, and they can be readily miniaturized using optical fibers for light delivery. Here, we report optical ultrasound transmitters fabricated by electrospinning an absorbing polymer composite directly onto the end-face of optical fibers. The composite coating consisting of an aqueous dispersion of multi-walled carbon nanotubes (MWCNTs) in polyvinyl alcohol was directly electrospun onto the cleaved surface of a multimode optical fiber and subsequently dip-coated with polydimethylsiloxane (PDMS). This formed a uniform nanofibrous absorbing mesh over the optical fiber end-face wherein the constituent MWCNTs were aligned preferentially along individual nanofibers. Infiltration of the PDMS through this nanofibrous mesh onto the underlying substrate was observed and the resulting composites exhibited high optical absorption (>97%). Thickness control from 2.3 μm to 41.4 μm was obtained by varying the electrospinning time. Under laser excitation with 11 μJ pulse energy, ultrasound pressures of 1.59 MPa were achieved at 1.5 mm from the coatings. On comparing the electrospun ultrasound transmitters with a dip-coated reference fabricated using the same constituent materials and possessing identical optical absorption, a five-fold increase in the generated pressure and wider bandwidth was observed. The electrospun transmitters exhibited high optical absorption, good elastomer infiltration, and ultrasound generation capability in the range of pressures used for clinical pulse-echo imaging. All-optical ultrasound probes with such transmitters fabricated by electrospinning could be well-suited for incorporation into catheters and needles for diagnostics and therapeutic applications.

Journal article

Batmunkh M, Macdonald TJ, Shearer CJ, Bat-Erdene M, Wang Y, Biggs MJ, Parkin IP, Nann T, Shapter JGet al., 2017, Carbon nanotubes in TiO2nanofiber photoelectrodes for high-performance Perovskite solar cells, Advanced Science, Vol: 4, Pages: 1-11, ISSN: 2198-3844

1D semiconducting oxides are unique structures that have been widely used for photovoltaic (PV) devices due to their capability to provide a direct pathway for charge transport. In addition, carbon nanotubes (CNTs) have played multifunctional roles in a range of PV cells because of their fascinating properties. Herein, the influence of CNTs on the PV performance of 1D titanium dioxide nanofiber (TiO2 NF) photoelectrode perovskite solar cells (PSCs) is systematically explored. Among the different types of CNTs, single‐walled CNTs (SWCNTs) incorporated in the TiO2 NF photoelectrode PSCs show a significant enhancement (≈40%) in the power conversion efficiency (PCE) as compared to control cells. SWCNTs incorporated in TiO2 NFs provide a fast electron transfer within the photoelectrode, resulting in an increase in the short‐circuit current (J sc) value. On the basis of our theoretical calculations, the improved open‐circuit voltage (V oc) of the cells can be attributed to a shift in energy level of the photoelectrodes after the introduction of SWCNTs. Furthermore, it is found that the incorporation of SWCNTs into TiO2 NFs reduces the hysteresis effect and improves the stability of the PSC devices. In this study, the best performing PSC device constructed with SWCNT structures achieves a PCE of 14.03%.

Journal article

Mange Y, Chandrasekaran S, Hollingsworth N, Voelcker N, Parkin I, Nann T, Macdonald Tet al., 2017, {Ni4O4} cluster complex to enhance the reductive photocurrent response on silicon nanowire photocathodes, Nanomaterials, Vol: 7, Pages: 33-33, ISSN: 2079-4991

Metal organic {Ni4O4} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW) photocathodes. {Ni4O4} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni4O4} clusters with SiNWs gave a current density of −16 mA/cm2, which corresponds to an increase in current density of 60% when compared to bare SiNWs. The composite electrode was fully characterised and shown to be an efficient and stable photocathode for water splitting.

Journal article

du Toit H, Macdonald TJ, Huang H, Parkin IP, Gavriilidis Aet al., 2017, Continuous flow synthesis of citrate capped gold nanoparticles using UV induced nucleation, RSC Advances: an international journal to further the chemical sciences, Vol: 7, Pages: 9632-9638, ISSN: 2046-2069

A new approach for synthesising gold nanoparticles of controlled size in the presence of trisodium citrate is presented. UV light is employed as a photoinitiator for the reduction of Au(III) by citrate. The UV induced nucleation takes place in a glass capillary tube (0.8 mm internal diameter) illuminated by a series of germicidal UVC lamps. This has been coupled sequentially with a heated coil to accelerate growth. In this way the processes of nucleation and growth are effectively separated. Slug flow is utilised in order to avoid tube fouling using heptane as segmenting fluid. Increasing UV intensity and temperature of the growth section lead to decrease of nanoparticle size, whilst varying UV exposure time results in a nonmonotonic effect on particle size. By varying UV intensity from 0 to 1461 mW cm−2 at a contant exposure time of 10 s, and a constant growth time of 20 min, the nanoparticles obtained range in size from 9.5 ± 1.3 nm to 36.1 ± 6.9 nm at a low growth temperature of 60 °C, and 6.6 ± 0.8 nm to 14.2 ± 6.4 nm at a high growth temperature of 100 °C.

Journal article

Macdonald TJ, Wu K, Sehmi SK, Noimark S, Peveler WJ, du Toit H, Voelcker NH, Allan E, MacRobert AJ, Gavriilidis A, Parkin IPet al., 2016, Thiol-capped gold nanoparticles swell-encapsulated into polyurethane as powerful antibacterial surfaces under dark and light conditions, Scientific Reports, Vol: 6, Pages: 1-11, ISSN: 2045-2322

A simple procedure to develop antibacterial surfaces using thiol-capped gold nanoparticles (AuNPs) is shown, which effectively kill bacteria under dark and light conditions. The effect of AuNP size and concentration on photo-activated antibacterial surfaces is reported and we show significant size effects, as well as bactericidal activity with crystal violet (CV) coated polyurethane. These materials have been proven to be powerful antibacterial surfaces against both Gram-positive and Gram-negative bacteria. AuNPs of 2, 3 or 5 nm diameter were swell-encapsulated into PU before a coating of CV was applied (known as PU-AuNPs-CV). The antibacterial activity of PU-AuNPs-CV samples was tested against Staphylococcus aureus and Escherichia coli as representative Gram-positive and Gram-negative bacteria under dark and light conditions. All light conditions in this study simulated a typical white-light hospital environment. This work demonstrates that the antibacterial activity of PU-AuNPs-CV samples and the synergistic enhancement of photoactivity of triarylmethane type dyes is highly dependent on nanoparticle size and concentration. The most powerful PU-AuNPs-CV antibacterial surfaces were achieved using 1.0 mg mL−1 swell encapsulation concentrations of 2 nm AuNPs. After two hours, Gram-positive and Gram-negative bacteria were reduced to below the detection limit (>4 log) under dark and light conditions.

Journal article

Elmas S, Beelders W, Nash J, Macdonald TJ, Jasieniak M, Griesser HJ, Nann Tet al., 2016, Photo-doping of plasma-deposited polyaniline (PAni), RSC ADVANCES, Vol: 6, Pages: 70691-70699, ISSN: 2046-2069

Journal article

Macdonald TJ, Tune DD, Dewi MR, Bear JC, McNaughter PD, Mayes AG, Skinner WM, Parkin IP, Shapter JG, Nann Tet al., 2016, SWCNT photocathodes sensitised with InP/ZnS core-shell nanocrystals, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 4, Pages: 3379-3384, ISSN: 2050-7526

Journal article

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