A Simple Molecular Design Strategy for Delayed Fluorescence toward 1000 nm.

Harnessing the near-infrared (NIR) region of the electromagnetic spectrum is exceedingly important for photovoltaics, telecommunications, and the biomedical sciences. While thermally activated delayed fluorescent (TADF) materials have attracted much interest due to their intense luminescence and narrow exchange energies (ΔEST), they are still greatly inferior to conventional fluorescent dyes in the NIR, which precludes their application. This is because securing a sufficiently strong donor-acceptor (D-A) interaction for NIR emission alongside the narrow ΔEST required for TADF is highly challenging. Here, we demonstrate that by abandoning the common polydonor model in favor of a D-A dyad structure, a sufficiently strong D-A interaction can be obtained to realize a TADF emitter capable of photoluminescence (PL) close to 1000 nm. Electroluminescence (EL) at a peak wavelength of 904 nm is also reported. This strategy is both conceptually and synthetically simple and offers a new approach to the development of future NIR TADF materials

Fc-Optimized Anti-CD25 Depletes Tumor-Infiltrating Regulatory T Cells and Synergizes with PD-1 Blockade to Eradicate Established Tumors

CD25 is expressed at high levels on regulatory T (Treg) cells and was initially proposed as a target for cancer immunotherapy. However, anti-CD25 antibodies have displayed limited activity against established tumors. We demonstrated that CD25 expression is largely restricted to tumor-infiltrating Treg cells in mice and humans. While existing anti-CD25 antibodies were observed to deplete Treg cells in the periphery, upregulation of the inhibitory Fc gamma receptor (FcγR) IIb at the tumor site prevented intra-tumoral Treg cell depletion, which may underlie the lack of anti-tumor activity previously observed in pre-clinical models. Use of an anti-CD25 antibody with enhanced binding to activating FcγRs led to effective depletion of tumor-infiltrating Treg cells, increased effector to Treg cell ratios, and improved control of established tumors. Combination with anti-programmed cell death protein-1 antibodies promoted complete tumor rejection, demonstrating the relevance of CD25 as a therapeutic target and promising substrate for future combination approaches in immune-oncology

Fc Effector Function Contributes to the Activity of Human Anti-CTLA-4 Antibodies.

With the use of a mouse model expressing human Fc-gamma receptors (FcγRs), we demonstrated that antibodies with isotypes equivalent to ipilimumab and tremelimumab mediate intra-tumoral regulatory T (Treg) cell depletion in vivo, increasing the CD8+ to Treg cell ratio and promoting tumor rejection. Antibodies with improved FcγR binding profiles drove superior anti-tumor responses and survival. In patients with advanced melanoma, response to ipilimumab was associated with the CD16a-V158F high affinity polymorphism. Such activity only appeared relevant in the context of inflamed tumors, explaining the modest response rates observed in the clinical setting. Our data suggest that the activity of anti-CTLA-4 in inflamed tumors may be improved through enhancement of FcγR binding, whereas poorly infiltrated tumors will likely require combination approaches

Design and Frabication of Optical Li+ Sensors for Application in Li-ion Batteries

Li-ion batteries have redefined expectations for consumer electronics and are the key technology in enabling the electrification of road transport. Their contribution to decarbonisation only stands to increase in the coming decades as demand for Li-ion batteries continues to soar. However, as production continues to accelerate, maximising device-level level sustainability over the lifetime of cells, modules, and battery packs is of increasing importance. Currently, there is a broad suite of techniques available in laboratory settings for the analysis of Li-ion battery performance and degradation during operation. Studying batteries using these techniques has led to the design of safer, longer-lasting batteries over the past few decades. However, most of these techniques use large and/or expensive instrumentation or require the design of bespoke cells and are therefore not applicable as methods for monitoring commercial battery systems in the field. Currently, only a small collection of non-disruptive diagnostic techniques are available for these applications. In addition, these techniques generally measure broad metrics, which are extrapolated using statistical methods to estimate and predict cell performance, often resulting in systematic underutilisation of battery systems. Optical techniques offer a potential solution to this problem owing to their low-cost, facile integration as part of commercial battery systems and their potential to monitor a range of mechanical, thermal, and chemical parameters through the application of optical fibres. By providing specific and detailed data in real-time, optical techniques coupled with a smart battery management system have the potential to improve battery lifetimes, reduced safety risks, and facilitate more advanced characterisation ahead of end-of-life protocols (e.g., re-use, recycling, etc). In this thesis, we discuss the development of a novel optical sensing platform for monitoring [Li+] in battery electrolytes. The first chapter introduces key concepts around the basic operation of Li-ion batteries and the degradation processes that lead to loss of performance during their operation. Following this, the range of *in situ* and *in operando* techniques that have facilitated our current understanding of processes occurring inside Li-ion batteries are discussed as well as the state-of-the-art in the application of optical techniques. This chapter ends with a summary of the thesis and its objectives and serves as an introduction to the context in which this work was originally formulated. The second chapter begins with an introduction to the field of optically active organic molecules, ionophores, and their convergence to form highly selective and sensitive optical chemosensors. Subsequently, the design, synthesis, and characterisation of two novel Li+-selective fluorescent chemosensors based on a naphthalene diimide core are described. Although both displayed poor solubility in salt-solvent systems reflective of the conditions in a Li-ion battery electrolyte, they were deemed to be a promising starting point for the development of a solid-supported chemosensor-based optical sensing platform for our applications. Chapter III starts with a summary of the fabrication and operation principles of planar and nanoparticle optodes as well as their application as part of optical fibre sensors. Following this is a discussion of potential strategies for the immobilisation of a chemosensor onto a solid support for applications as an optode sensor. Subsequently, the chapter describes the optimisation of experimental parameters towards the development of a fabrication procedure for planar optodes functionalised with one of the novel chemosensors synthesised in Chapter II. The final planar optodes used a silica-based substrate loaded with a mesoporous surface film, which is functionalised with a modified derivative of the chemosensor. Characterisation of the planar optodes demonstrated their promising properties for monitoring [Li+] selectively in concentration ranges and solution conditions relevant to Li-ion battery electrolytes. This chapter also summarises attempts to apply the same fabrication procedure for the functionalisation of optical fibres to form ‘dip probes.’ However, these were largely unsuccessful. To further characterise the properties of the optode sensor in emission mode, the planar optodes were integrated as part of microfluidic devices. This provided precise control over liquid samples on the optode surface and enabled full characterisation of their Li+-sensing capabilities in emission mode. Chapter IV provides a summary of this data, which showed the planar optodes to possess the necessary sensitivity and selectivity for application as an emission mode concentration sensor in battery electrolytes. In addition, the platform was shown to demonstrate strong cyclability, a rapid time response, and a level of spatial resolution that suggested the optodes could be applied for dynamic chemical imaging using fluorescence microscopy. Chapter V is the final chapter and describes the application of the optode-based microfluidic devices for two proof-of-concept experiments. Firstly, ex-situ [Li+] measurements were taken using the devices on a pristine electrolyte and electrolyte extracted from a Li-ion pouch cell after cycling. These results provided a quantitative indication of bulk Li+ depletion in the electrolyte during cycling with a comparable level of accuracy to ICP-OES measurements run in parallel. Secondly, simple experimental conditions were designed to establish the ability of the optodes to track the evolution of Li+ concentration gradients in solution with time. These experiments yielded the first recorded example of spatial Li+ tracking using a solid-supported optical sensor to our knowledge. Modelling of the diffusion data showed that the experimental results could provide a comparative estimation of the Li+ self-diffusion coefficients for different solvent systems.PhD fully-funded by The Faraday Institutio

Research data supporting "Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and conjugated polymers"

Compressed (.zip) folder containing data from normalized photoluminescence spectra of M3TTM and M2TTM-3PCz radicals and PFMTTM polyradical in 0.1 mM toluene solutions (Fig1c.xlsx); normalized steady-state emission spectra of MxTTM radicals in 0.1 mM toluene solutions (Fig3a.xlsx) and emission kinetics in the 580-610 nm region showing rapid emission following 520 nm excitation (Fig3b.xlsx); normalized steady-state emission spectra of MxTTM radicals in 8 wt% evaporated films in CBP showing increasing emission red-shift and linewidth broadening with decreasing mesitylation (Fig.3c.xlsx) and total emission kinetics in the range of 550-880 nm following 520 nm excitation using 100 fs pulses with fluence 5 μJ cm-2 (Fig3d.xlsx), inset shows early time kinetics (Fig3dInset.xlsx); time-gated photoluminescence spectra of 8 wt% M2TTM radical in CBP film showing monomer emission at nanosecond times and exciplex emission at microsecond times (Fig3e.xlsx); dynamics of emission of MxTTM radicals in CBP films showing time dependence of peak emission wavelength (Fig3f1.xlsx) and integrated photoluminescence counts in the range of 550-880 nm (Fig3f2.xlsx); external quantum efficiency versus current density (Fig4b.xlsx) and current density-voltage-luminance characteristics of organic light-emitting diodes with M2TTM-3PCz radical as the emitter (Fig4c.xlsx); normalized photoluminescence spectrum of the light-emitting layer of 5 wt% M2TTM-3PCz doped CBP film following 405 nm excitation and normalized electroluminescence spectrum of the device at 0.2 mA cm-2 (Fig4d.xlsx); computational atomic coordinates of optimized MxTTM structures in the ground and excited states calculated at the UB3LYP(D3)/def2-SVP and UCAM-B3LYP(D3)/def2-SVP levels of theory, respectively (MxTTM_coordinates.docx).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreements No. 891167, No. 859752 and No. 886066, from the European Research Council under the European Union’s Horizon 2020 research and innovation programme grant agreement No. 101020167 and from the Engineering and Physical Sciences Research Council NanoDTC, EP/S003126/1, EP/S022953/1

Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and conjugated polymers.

Acknowledgements: We thank Dr Andrew Bond for carrying out the X-ray crystallography measurements and data analysis at the Yusuf Hamied Department of Chemistry, University of Cambridge. P.M., R.C. and W.Z. have received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreements No. 891167, No. 859752 and No. 886066. We acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme grant agreement No. 101020167 (R.H.F., P.M., E.G., S.G.) and the Engineering and Physical Sciences Research Council NanoDTC, EP/S003126/1, EP/S022953/1 (S.G.).Neutral π-radicals have potential for use as light emitters in optoelectronic devices due to the absence of energetically low-lying non-emissive states. Here, we report a defect-free synthetic methodology via mesityl substitution at the para-positions of tris(2,4,6-trichlorophenyl)methyl radical. These materials reveal a number of novel optoelectronic properties. Firstly, mesityl substituted radicals show strongly enhanced photoluminescence arising from symmetry breaking in the excited state. Secondly, photoexcitation of thin films of 8 wt% radical in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl host matrix produces long lived (in the order of microseconds) intermolecular charge transfer states, following hole transfer to the host, that can show unexpectedly efficient red-shifted emission. Thirdly, covalent attachment of carbazole into the mesitylated radical gives very high photoluminescence yield of 93% in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl films and light-emitting diodes with maximum external quantum efficiency of 28% at a wavelength of 689 nm. Fourthly, a main-chain copolymer of the mesitylated radical and 9,9-dioctyl-9H-fluorene shows red-shifted emission beyond 800 nm

Current indoor allergen levels of fungi and cats, but not house dust mites, influence allergy and asthma in adults with high dust mite exposure

C1 - Journal Articles Referee

A solution-processable near-infrared thermally activated delayed fluorescent dye with a fused aromatic acceptor and aggregation induced emission behavior

The unique synergy of properties offered by an efficient and processable near-infrared thermally activated delayed fluorescent (NIR TADF) dye could be transformative across research fields. Here, a solution-processable NIR TADF material is demonstrated (CAT-TPE). Good solubility is achieved through the use of a new tetraphenylethylene (TPE)-based triphenylamine electron donor. TADF is confirmed through variable temperature time-resolved measurements at a peak photoluminescence (PL) wavelength of 842 nm in a solution-processed film. An OLED with good roll-off characteristics for a solution-processed NIR TADF device is reported with electroluminescence λmax > 700 nm. CAT-TPE also demonstrates classic aggregation induced emission (AIE) behavior, being more emissive when aggregated than in solution with all PL > 700 nm. This work opens the door to the considerably enhanced structural diversity of solution-processable NIR TADF and will inform the design of future high efficiency AIE NIR TADF materials

Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs

Acknowledgements: P. L. D. Santos and D. Credgington are acknowledged for their contribution to important discussion at the beginning of this project. A. P. Monkman is acknowledged for the use of facilities at Durham University for the time-resolved PL measurements. H.-H.C. acknowledges George and Lilian Schiff Foundation for PhD studentship funding. D.G.C. acknowledges the Herchel Smith fund for an early career fellowship. A.J.G. thanks the Leverhulme Trust for an Early Career Fellowship (ECF-2022-445). V.R.-G. acknowledges the Faraday Institution Degradation Project (grant no. FIRG001 and FIRG024). J.Y. acknowledges support from a UK Research and Innovation (UKRI) Frontier Grant (no. EP/X029900/1), awarded via the European Research Council Starting Grant 2021 scheme. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC, grant nos. EP/M005143/1 and EP/S003126/1). H.-H.C. and R.H.F. acknowledge the European Research Council for European Union’s Horizon 2020 research and innovation programme grant agreement no. 101020167.Funder: George and Lilian Schiff Foundation for Ph.D. studentship fundingFunder: Herchel Smith fundHyperfluorescence shows great promise for the next generation of commercially feasible blue organic light-emitting diodes, for which eliminating the Dexter transfer to terminal emitter triplet states is key to efficiency and stability. Current devices rely on high-gap matrices to prevent Dexter transfer, which unfortunately leads to overly complex devices from a fabrication standpoint. Here we introduce a molecular design where ultranarrowband blue emitters are covalently encapsulated by insulating alkylene straps. Organic light-emitting diodes with simple emissive layers consisting of pristine thermally activated delayed fluorescence hosts doped with encapsulated terminal emitters exhibit negligible external quantum efficiency drops compared with non-doped devices, enabling a maximum external quantum efficiency of 21.5%. To explain the high efficiency in the absence of high-gap matrices, we turn to transient absorption spectroscopy. It is directly observed that Dexter transfer from a pristine thermally activated delayed fluorescence sensitizer host can be substantially reduced by an encapsulated terminal emitter, opening the door to highly efficient ‘matrix-free’ blue hyperfluorescence