Jonathan Coleman

Trinity College Dublin | TCD · School of Physics

Networks of nanowires and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the inter-particle junction resistance, a property that is challenging to minimise because it is difficult to measure. Here, we develop a simple model for conduction in networks of 1D...

Thin film networks of solution processed nanosheets show remarkable promise for use in a broad range of applications including strain sensors, energy storage, printed devices, textile electronics and more. While it is known that their electronic properties rely heavily on their morphology, little is known of their mechanical nature, a glaring omiss...

Solution‐processed photodetectors incorporating liquid‐phase‐exfoliated transition metal dichalcogenide nanosheets are widely reported. However, previous studies mainly focus on the fabrication of photoconductors, rather than photodiodes which tend to be based on heterojunctions and are harder to fabricate. Especially, there are rare reports on int...

Combining high-capacity electrodes with good rate performance is essential for maximising both energy and power density in Li-ion batteries. While much effort has been dedicated to increasing both capacity and rate performance, little consideration has been made as to how an increase in specific or volumetric capacity might directly affect rate per...

Transparent conductors (TCs) represent key components in many applications from optoelectronic devices to electromagnetic shielding. While commercial applications typically use thin films of indium tin oxide, this material is brittle and increasingly scarce, meaning higher performing and cheaper alternatives are sought after. Solution-processible m...

Functional conductive hydrogels are widely used in various application scenarios, such as artificial skin, cell scaffolds, and implantable bioelectronics. However, their novel designs and technological innovations are severely hampered by traditional manufacturing approaches. Direct ink writing (DIW) is considered a viable industrial‐production 3D‐...

Chemical sensing of water contamination by heavy metal ions is key as it represents a most severe environmental problem. Liquid-phase exfoliated two-dimensional (2D) transition metal dichalcogenides (TMDs) are suitable candidates for chemical sensing thanks to their high surface-to-volume ratio, sensitivity, unique electrical characteristics, and s...

Networks of solution-processed nanomaterials are becoming increasingly important across applications in electronics, sensing and energy storage/generation. Although the physical properties of these devices are often completely dominated by network morphology, the network structure itself remains difficult to interrogate. Here, we utilise FIB-SEM na...

Device performance of solution‐processed 2D semiconductors in printed electronics has been limited so far by structural defects and high inter‐flake junction resistance. Covalently interconnected networks of transition metal dichalcogenides potentially represent an efficient strategy to overcome both limitations simultaneously. Yet, the charge tran...

Additive manufacturing strategies are gaining more importance in the context of lithium-ion batteries. The rapid prototyping, reduced waste and complex 3D structures achievable are powerful and attractive tools that are out of the reach of current fabrication techniques. Additionally, thanks to the potential that these manufacturing techniques hold...

Piezoresistive nanocomposites are an important class of materials that allow the production of very sensitive strain sensors. Herein, a new class of piezoresistive nanocomposites prepared by mixing different types of 2D nanosheets is explored. In this way, three distinct types of nanocomposite are produced by mixing conducting and insulating nanosh...

The family of antiferromagnetic layered metal hexathiohypo diphosphates, M2P2S6 represents a versatile class of materials, particularly interesting for fundamental studies on magnetic properties in low dimensional structures, and yet exhibiting great potential for a broad variety of applications including catalysis, energy storage and conversion, a...

The investigation of high-mobility two-dimensional (2D) flakes beyond molybdenum disulfide (MoS2) will be necessary to create a library of high-mobility solution-processed networks that conform to substrates and remain functional over thousands of bending cycles. Here we report electrochemical exfoliation of large-aspect-ratio (>100) semiconducting...

Networks of solution-processed nanomaterials are important for multiple applications in electronics, sensing and energy storage/generation. While it is known that network morphology plays a dominant role in determining the physical properties of printed networks, it remains difficult to quantify network structure. Here, we utilise FIB-SEM nanotomog...

Liquid-phase exfoliation (LPE) has been introduced as a versatile and scalable production method for two-dimensional (2D) materials. This method yields dispersions that allow for the fabrication of printable and flexible electronic devices. However, the fabrication of uniform and homogeneous films from LPE dispersions with a performance similar to...

The scalable production of two-dimensional (2D) materials is needed to accelerate their adoption to industry. In this work, we present a low-cost in-line and enclosed process of exfoliation based on high-shear mixing to create aqueous dispersions of few-layer graphene, on a large scale with a Y w ~ 100% yield by weight and throughput of ϕ ~ 8.3 g h...

The growing clinical demand for electrical stimulation-based therapies requires the development of novel conductive biomaterials that balance conductivity, biocompatibility, and mechanical performance. Traditional conductive materials often induce scarring, due to their stiffness and poor biocompatibility, presenting challenges to their clinical tr...

The development of sodium ion batteries will require high‐performance electrodes with very large areal capacity and reasonable rate performance. Although red phosphorus is a very promising electrode material, it has not yet fulfilled these requirements. Here, liquid phase exfoliation is used to convert solid red phosphorus into amorphous, quasi‐2D...

Vertically stacked metal-semiconductor-metal heterostructures, based on liquid-processed nanomaterials, hold great potential for various printed electronic applications. Here we describe the fabrication of such devices by spray-coating semiconducting tungsten disulfide (WS2) nanosheets onto indium tin oxide (ITO) bottom electrodes, followed by spra...

Iron oxide (Fe2O3) is an abundant and potentially low‐cost material for fabricating lithium‐ion battery anodes. Here, the growth of α‐Fe2O3 nano‐flowers at an electrified liquid–liquid interface is demonstrated. Sonication is used to convert these flowers into quasi‐2D platelets with lateral sizes in the range of hundreds of nanometers and thicknes...

For nearly 15 years, researchers have been using liquid‐phase exfoliation (LPE) to produce 2D nanosheets from layered crystals. This has yielded multiple 2D materials in a solution‐processable form whose utility has been demonstrated in multiple applications. It was believed that the exfoliation of such materials was enabled by the very large bondi...

In addition to improving parameters such as energy density and stability, it is important to maximise rate performance in lithium-ion batteries. While much work has focused on rate-limiting factors associated with the electrodes, much less attention has been paid to the effect of the separator on rate-performance. Here we perform a quantitative stu...

Developing high-performance cathode materials for lithium-ion batteries is necessary to maximise both energy and power density. One promising cathode material is iron trifluoride (FeF3) having a high theoretical capacity of 712 mAh/g, although achieving this value experimentally is challenging. Our previous works has shown that achievable capacity...

Although printed networks of semiconducting nanosheets have found success in a range of applications, conductive nanosheet networks are limited by low conductivities (<106 S m−1). Here, dispersions of silver nanosheets (AgNS) that can be printed into highly conductive networks are described. Using a commercial thermal inkjet printer, AgNS patterns...

Printed strain sensors will be important in applications such as wearable devices, which monitor breathing and heart function. Such sensors need to combine high sensitivity and low resistance with other factors such as cyclability, low hysteresis, and minimal frequency/strain-rate dependence. Although nanocomposite sensors can display a high gauge...

The ongoing miniaturization of devices and development of wireless and implantable technologies demand electromagnetic interference (EMI) shielding materials with customizability. Additive manufacturing of conductive polymer hydrogels with favourable conductivity and biocompatibility can offer new opportunities for EMI shielding applications. Howev...

Solution-processed networks of 2D nanosheets are promising for a range of applications in the field of printed electronics. However, the electrical performance of these networks — represented, for example, by the mobility — is almost always inferior to that of the individual nanosheets. In this Review, we highlight the central role that the inter-s...

Recently, it has been shown that it is possible to apply liquid-phase exfoliation to non-layered materials, yielding quasi-2D nanosheets. It has been proposed that even a slight bonding anisotropy in the starting crystal will lead to a platelet-like geometry, albeit with low aspect ratio. While this development opens the way to many previously unex...

Solution-processed semiconducting transition metal dichalcogenides are at the centre of an ever-increasing research effort in printed (opto)electronics. However, device performance is limited by structural defects resulting from the exfoliation process and poor inter-flake electronic connectivity. Here, we report a new molecular strategy to boost t...

While nanocomposite electromechanical sensors are expected to display reasonable conductivity and high sensitivity, little consideration is given to eliminating hysteresis and strain rate/frequency dependence from their response. For example, while G‐putty, a composite of graphene and polysiloxane, has very high electromechanical sensitivity, its e...

Conductive nanocomposites are often piezoresistive, displaying significant changes in resistance upon deformation, making them ideal for use as strain and pressure sensors. Such composites typically consist of ductile polymers filled with conductive nanomaterials, such as graphene nanosheets or carbon nanotubes, and can display sensitivities, or ga...

It is well-known that the morphology of nanostructured networks is closely linked to network proper-ties. However, controlling and characterizing the morphology of networks of 2D nanosheets has not been explored. In this work, we use networks of liquid-exfoliated graphene nanosheets as a model system to examine the relationship between network morp...

Increasing the energy density of lithium‐ion batteries requires the discovery of new electrode materials capable of achieving very high areal capacity. Here, liquid phase exfoliation is used to produce nanosheets of SnP3, a 2D material with extremely high theoretical capacity of 1670 mAh g⁻¹. These nanosheets can be fabricated into solution‐process...

The development of low-cost ultrafiltration membranes with relatively high flow rate and selectivity is an important goal which could improve access to clean water in the developing world. Here we demonstrate a method to infuse mixtures of graphene nanosheets and Teflon nanoparticles into ultra-cheap glass fibre membranes. Annealing the resultant c...

For battery electrodes, measured capacity decays as charge/discharge current is increased. Such rate-performance is usually characterised via galvanostatic charge-discharge measurements, experiments which are very slow, limiting the speed at which rate experiments can be completed. This is particularly limiting during mechanistic studies where many...

Batteries are increasingly used in energy-storage applications where a high power is needed in tandem with a high capacity, with electric vehicles being a great example. These batteries ideally deliver large amounts of current for extended periods with no compromise in capacity. However, as the rate is increased, the capacity that can be delivered...

Adding porosity to battery electrodes is sometimes useful for accommodating volumetric expansion, electrolyte access to active materials, or mitigating poor high-rate performance for thicker electrodes. Ordered macroporous electrode such as inverse opals, are a good model system: binder and conductive additive-free, interconnected electrically, hav...

Printed networks of insulating two-dimensional (2D) materials are promising for dielectric applications in printed electronic devices. However, this work has not really progressed beyond networks of boron nitride (BN) nanosheets displaying dielectric constants of <6. Here we use liquid-phase exfoliation to demonstrate the production of nanosheets f...

Simultaneous optimization of capacity and rate performance in battery electrodes would be much simplified by access to a simple equation relating rate performance to electrode thickness. Although a number of equations have been proposed, data on the effect of electrode thickness on rate performance are not extensive enough to identify the most appr...

Over the last fifteen years, two-dimensional (2D) materials have been studied and exploited for many applications. In many cases, 2D materials are formed by the exfoliation of layered crystals such as transition-metal disulphides. However, it has recently become clear that it is possible to exfoliate non-layered materials so long as they have a non...

Covalently tethering photosensitizers to catalytically active 1T-MoS 2 surfaces holds great promise for the solar-driven hydrogen evolution reaction (HER). Herein we report the preparation of two new Ru II complex functionalized MoS 2 hybrids [Ru II (bpy) 2 (phen)]-MoS 2 and [Ru II (bpy) 2 (py)Cl]-MoS 2 . The influence of covalent functionalization...

In article number 2002473, Izabela Jurewicz, Alan B. Dalton, and co‐workers fabricate high quality opal‐like photonic crystals containing graphene using evaporation‐driven self‐assembly of soft polymer colloids. The graphene enhanced photonic crystals are structurally colored materials that are iridescent, so their color changes with the viewing an...

For battery electrodes, measured capacity decays as charge/discharge current is increased. Such rate-performance is usually characterised via galvanostatic charge-discharge measurements, experiments which are very slow, limiting the speed at which rate experiments can be completed. This is particularly limiting during mechanistic studies where many...

The two-electron reduction of molecular oxygen represents an effective strategy to enable the green, mild and on-demand synthesis of hydrogen peroxide. Its practical viability, however, hinges on the development of advanced electrocatalysts, preferably composed of non-precious elements, to selectively expedite this reaction, particularly in acidic...

Demonstration of high-performance, all-printed transistors fabricated only from networks of two-dimensional nanosheets would represent a significant advance in printed electronics. However, such devices have only been shown to work via electrolytic gating. Under those circumstances, both channel-electrolyte and gate-electrolyte interfaces show sign...

Liquid phase exfoliation (LPE) is the principal method of producing two-dimensional (2D) materials such as graphene in large quantities with a good balance between quality and cost, and is now widely adopted by both the academic and industrial sectors. The fragmentation and exfoliation mechanisms involved have usually been simply attributed to the...

Liquid phase exfoliation is a commonly used method to produce 2D nanosheets from a range of layered crystals. However, such nanosheets display broad size and thickness distributions and correlations between area and thickness, issues that limit nanosheet application potential. To understand the factors controlling the exfoliation process, we have l...

As a recent addition to the family of Van der Waals layered crystals, indium selenide (InSe) possesses unique optoelectronic and photonic properties, enabling high-performance electronic devices for broad applications. Nevertheless, the lithium storage behavior of InSe flakes is thus largely unexplored due to its low electronic conductivity and cha...

High quality opal-like photonic crystals containing graphene are fabricated using evaporation-driven self-assembly of soft polymer colloids. A miniscule amount of pristine graphene within a colloidal crystal lattice results in the formation of colloidal crystals with a strong angle-dependent structural color and a stop band that can be reversibly s...

The propensity of many 2D materials to oxidize in ambient conditions can complicate production and limit applications potential. Here we describe ambient liquid phase exfoliation of GeS, a layered material known for its chemical instability. Ambient exfoliation in organic solvents such as N-methyl-pyrrolidone yields good quality multi-layer GeS nan...

Graphene-based materials are of increasing interest for their potential use in biomedical applications. However, there is a need to gain a deeper understanding of how graphene modulates biological responses before moving towards clinical application. Innate immune training is a recently described phenomenon whereby cells of the innate immune system...

Liquid phase exfoliation has progressed in recent years to become a common method of production for 2D materials. During exfoliation, surfactants can be used to stabilize the nanosheets against reaggregation. Here, using WS2 as a model system, we explore the effect of varying surfactant type and concentration on the yield and dimensions of the exfo...

Two dimensional materials show great potential for use in battery electrodes and are believed to be particularly promising for high-rate applications. However, there does not seem to be much hard evidence for the superior rate-performance of 2D materials compared to non-2D materials. To examine this point, we have analyzed published rate-performanc...

Ferroelectricity in ultrasonically exfoliated flakes of the layered Aurivillius oxide Bi5Ti3Fe0.5Co0.5O15 with a range of thicknesses is studied. These flakes have relatively large areas (linear dimensions many times the film thickness), thus classifying them as 2D materials. It is shown that ferroelectricity can exist in flakes with thicknesses of...

While it is well-known that electronic conductivity of electrodes has a critical impact on rate-performance in batteries, this relationship has been quantified only by computer simulations. Here we investigate the relationship between electrode electronic conductivity and rate-performance in a model system of Lithium-Nickel-Manganese-Cobalt-Oxide (...

We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a ‘hands-on’ approach, providing practical details and procedures as derived from literature as well as from the authors’ experience, in order to enable the reader to reproduc...

Monitoring the uptake, micro-environment and fate of micro or nano scaled particulate materials in cells is of paramount importance for the emerging fields of toxicology and medicine. Such particulate materials are known to interfere with colorimetric assays and many such assays record only a single end-point. Therefore, there is a need for a label...

The dielectric constant, which defines the polarization of the media, is a key quantity in condensed matter. It determines several electronic and optoelectronic properties important for a plethora of modern technologies from computer memory to field effect transistors and communication circuits. Moreover, the importance of the dielectric constant i...

Analyzing rate-performance data in battery electrodes is greatly facilitated by access to simple analytical models. Here we describe a number of simple equations for fitting capacity-rate data. These equations output fit parameters, such as the characteristic time, which quantify rate-performance. This characteristic time can be linked to mechanist...

The dielectric constant, which defines the polarization of the media, is a key quantity in condensed matter. It determines several electronic and optoelectronic properties important for a plethora of modern technologies from computer memory to field effect transistors and communication circuits. Moreover, the importance of the dielectric constant i...

Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natu...

Two dimensional materials show great potential for use in battery electrodes and are believed to be particularly promising for high-rate applications. However, there does not seem to be much hard evidence for the superior rate-performance of 2D materials compared to non-2D materials. To examine this point, we have analyzed published rate-performanc...

While it is well-known that electrode conductivity has a critical impact on rate-performance in battery electrodes, this relationship has been quantified only by computer simulations. Here we investigate the relationship between electrode conductivity and rate-performance in Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) cathodes filled with various q...

Due to their reduced dimensionality, 2D materials show intriguing optical properties and strong light matter interaction. In particular group VI transition metal dichalcogenides (TMDs) have been extensively studied and proof of principle optical applications demonstrated. Most studies to date focus on individual mono-or bilayered micromechanically-...

For battery electrodes, measured capacity decays as charge/discharge current is increased. Such rate-performance is important from a practical perspective and is usually characterised via galvanostatic charge-discharge measurements. However, such measurements are very slow, limiting the number of rate experiments which are practical in a given proj...

Recent advances in the liquid-phase exfoliation (LPE) of layered materials have facilitated significant progress in the creation of functional inks. While ethanol/water blends have been shown to yield reasonable nanosheet dispersions with the potential for refinement into printable inks, the exfoliated mass is typically too low for practical use. H...

Among other things, battery electrodes need to display large absolute capacities coupled with high rate performance. However, enhancing areal capacity, for example via increased electrode thickness, results in reductions in rate performance. The basis for this negative correlation has not been studied in a quantitative fashion. Here, a semiempirica...