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Abstract

We investigate the internal crystallinity of calcite crystals synthesized using two approaches: precipitation from solution and the ammonium carbonate diffusion method. Scanning electron microscopy (SEM) analyses reveal that the calcite products precipitated using both approaches had a well-defined rhombohedron shape, consistent with the euhedral crystal habit of the mineral. The internal structure of these calcite crystals was characterized using Bragg coherent diffraction imaging (BCDI) to determine the 3D electron density and the atomic displacement field. BCDI reconstructions for crystals synthesized using the ammonium carbonate diffusion approach have the expected euhedral shape, with internal strain fields and few internal defects. In contrast, the crystals synthesized by precipitation from solution have very complex external shapes and defective internal structures, presenting null electron density regions and pronounced displacement field distributions. These heterogeneities are interpreted as multiple crystalline domains, created by a non-classical crystallization mechanism where smaller nanoparticles coalescence into the final euhedral particles. The combined use of SEM, X-ray diffraction (XRD), and BCDI allows us to structurally differentiate calcite crystals grown with different approaches, opening new opportunities to understand how grain boundaries and internal defects alter calcite reactivity.

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Abstract

Photon recycling plays an important role in the light outcoupling of state-of-the-art solar cells and has been considered a necessary condition to achieve the radiative limit of open-circuit voltage (V OC) and efficiency. However, due to the impact of photon recycling on bulk and surface radiation of solar cells being overlooked, experimental demonstrations on the accuracy of existing photon recycling models are scarce and some contrary theoretical results also emerge. Here, we clarify the relationship between photon recycling and radiation processes, as well as the corresponding V OC losses of solar cells based on the principle of detailed balance. We show that weakening photon recycling is more effective to boost the device performance than enhancing it, promoting the theoretical efficiencies of solar cells, such as perovskite, Si, and GaAs, to 98.5%, 94.9%, and almost 100% of their radiative limit, respectively. Moreover, weakening photon recycling also helps to maintain higher efficiency when the internal radiative efficiency decreases, which benefits higher device stability. Our work provides an in-depth understanding of the role of photon recycling in solar cells and helps to push efficiency to a new limit.

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Abstract

Ultrafast short-wavelength infrared (SWIR) photodetection is of great interest for emerging automated vision and spatial mapping technologies. Colloidal quantum dots (QDs) stand out for SWIR photodetection compared to epitaxial (In,Ga)As or (Hg,Cd)Te semiconductors by their combining a size-tunable bandgap and a suitability for cost-effective, solution-based processing. However, achieving ultrafast, ns-level response time has remained an outstanding challenge for QD-based SWIR photodiodes (QDPDs). Here, we report on record 4 ns response time in PbS-based QDPDs that operate at SWIR wavelengths, a result reaching the requirement of SWIR LiDAR based on colloidal QDs. These ultrafast QDPDs combine a thin active layer to reduce the carrier transport time and a small area to inhibit slow capacitive discharging. By implementing a concentration gradient ligand exchange method, high-quality p-n junctions are fabricated in these ultrathin QDPDs. Moreover, these ultrathin QDPDs attain an external quantum efficiency of 42% at 1330 nm, due to a 2.5-fold enhanced light absorption through the formation of a Fabry-Perot cavity within the QDPD and the highly efficient extraction (98%) of photogenerated charge carriers from the PbS QD film. Based on these results, we estimate that a further increase of the charge-carrier mobility can lead to PbS QDPDs with sub-ns response time.

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Abstract

Constructing soft robotics with safe human-machine interactions requires low-modulus, high-power-density artificial muscles that are sensitive to gentle stimuli. In addition, the ability to resist crack propagation during long-term actuation cycles is essential for a long service life. Herein, for the first time, we propose a material design to combine all these desirable attributes in a single artificial muscle platform. Our design involves the molecular engineering of a liquid crystalline network with crystallizable segments and an ethylene glycol flexible spacer. A high degree of crystallinity could be afforded by utilizing aza-Michael chemistry to produce a low covalent crosslinking density, resulting in crack-insensitivity with a high fracture energy of 33720 J m−2 and a high fatigue threshold of 2250 J m−2. Such crack-resistant artificial muscle with tissue-matched modulus of 0.7 MPa can generate a high power density of 450 W kg−1 at a low temperature of 40 °C. Notably, because of the presence of crystalline domains in the actuated state, no crack propagation was observed after 500 heating-cooling actuation cycles under a static load of 220 kPa. This study points to a pathway for the creation of artificial muscles merging seemingly disparate, but desirable properties, broadening their application potential in smart devices.

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Radio observations of extra-galactic transients with the AMI-LA telescope

The Arcminute Microkelvin Imager – Large Array has been instrumental in the study of radio transients. In this talk I will give an overview of the current extragalactic transients monitoring program which is running on AMI -LA. To demonstrate the power of AMI -LA in improving our shock physics in extragalactic transients I will go through two examples of events where AMI -LA has been instrumental. Starting with the most relativistic systems: GRBs have been observed by AMI -LA from as early as 2012 with the ALARRM rapid follow up system. GRB 221009A , also known as the brightest of all time, has demonstrated the unparalleled temporal coverage achievable with AMI -LA from a few hours to over 100 days post burst. AMI -LA has also enabled us to draw conclusions that wouldn’t be possible with other facilities such as the jetted tidal disruption event AT2022cmc that was first reported in 2022. Due to the high cadence light curve with AMI -LA, we were able to prove for the first time, in a model independent manner that the radio emission originated from a highly relativistic outflow. Such a result has been vital in terms of our understand of tidal disruption events and can now infer the presence of off-axis jets such as AT2018hyz.

• Speaker: Dr. Lauren Rhodes (University of Oxford)
• Tuesday 30 April 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Abstract

The perovskite/Cu(InGa)Se2 (CIGS) tandem solar cells (TSCs) presents a compelling technological combination poised for the next generation of flexible and lightweight photovoltaic (PV) tandem devices, featuring a tunable bandgap, high power conversion efficiency (PCE), lightweight flexibility and enhanced stability and durability. Over the years, the imperative to enhance the performance of wide bandgap (WBG) perovskite solar cells (PSCs) has grown significantly, particularly in the context of a flexible tandem device. In this study, we introduce an all-round passivation (ARP) strategy known as Dual Passivation at Grains and Interfaces (DPGI) for WBG PSCs in perovskite/CIGS tandem structures. The implementation of DPGI is tailored to improve film crystallinity and passivate defects across the solar cell structure, leading to a substantial performance enhancement for WBG PSCs. Subsequently, both rigid and flexible tandem devices are assembled. Impressively, we successfully fabricated a fully flexible 4T perovskite/CIGS TSCs with a PCE of 26.57%, making it the highest value in this field and highlighting its potential applications in the next generation of flexible lightweight PV tandem devices.

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Nature Energy, Published online: 25 April 2024; doi:10.1038/s41560-024-01523-9

Getting a charge out of perovskites

Nature Energy, Published online: 25 April 2024; doi:10.1038/s41560-024-01521-x

Patterned membranes

Nature Energy, Published online: 25 April 2024; doi:10.1038/s41560-024-01524-8

Outweighing increased efficiency

Nature Energy, Published online: 25 April 2024; doi:10.1038/s41560-024-01522-w

Threshold for degradation

Nature Materials, Published online: 25 April 2024; doi:10.1038/s41563-024-01888-y

A strategy of on-device phase engineering of two-dimensional materials is proposed, allowing the in situ realization of various lattice phases with distinct stoichiometries and versatile functions.

Abstract

Phonon polaritons, the hybrid quasiparticles resulting from the coupling of photons and lattice vibrations, have gained significant attention in the field of layered van der Waals heterostructures. Particular interest has been paid to hetero-bicrystals composed of molybdenum oxide (MoO3) and hexagonal boron nitride (hBN), which feature polariton dispersion tailorable via avoided polariton mode crossings. In this work, we systematically study the polariton eigenmodes in MoO3-hBN hetero-bicrystals self-assembled on ultrasmooth gold using synchrotron infrared nanospectroscopy. We experimentally demonstrate that the spectral gap in bicrystal dispersion and corresponding regimes of negative refraction can be tuned by material layer thickness, and we quantitatively match these results with a simple analytic model. We also investigate polaritonic cavity modes and polariton propagation along “forbidden” directions in our microscale bicrystals, which arise from the finite in-plane dimension of the synthesized MoO3 micro-ribbons. Our findings shed light on the unique dispersion properties of polaritons in van der Waals heterostructures and pave the way for applications leveraging deeply sub-wavelength mid-infrared light matter interactions.

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Abstract

High performance organic solar cells (OSCs) are usually realized by using thermal post-treatment and/or additive, which can induce the formation of metastable morphology, leading to unfavorable device stability. In terms of the industrial production, the development of high efficiency as-cast OSCs is crucially important, but it remains a great challenge to obtain appropriate active layer morphology and high power conversion efficiency (PCE). Here, efficient as-cast OSCs are constructed via introducing a new polymer acceptor PY-TPT with a high dielectric constant into the D18:L8-BO blend to form a double-fibril network morphology. Besides, the incorporation of PY-TPT enables an enhanced dielectric constant and lower exciton binding energy of active layer. Therefore, efficient exciton dissociation and charge transport are realized in D18:L8-BO:PY-TPT based device, affording a record-high PCE of 18.60% and excellent photostability in absence of post-treatment. Moreover, green solvent-processed devices, thick-film (300 nm) devices, and module (16.60 cm2) are fabricated, which show PCEs of 17.45%, 17.54% and 13.84%, respectively. This work brings new insight into the construction of efficient as-cast devices, pushing forward the practical application of OSCs.

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Abstract

The advancement of mRNA-based immunotherapies for cancer is highly dependent on the effective delivery of RNA payloads using ionizable lipid nanoparticles (LNPs). However, the clinical application of these therapies is hindered by variable mRNA expression among different cancer types and the risk of systemic toxicity. The transient expression profile of mRNA further complicates this issue, necessitating frequent dosing and thus increasing the potential for adverse effects. Addressing these challenges, we utilized a high-throughput combinatorial method to synthesize and screen LNPs that efficiently deliver circular RNA (circRNA) to lung tumors. Our lead LNP, H1L1A1B3, demonstrated a fourfold increase in circRNA transfection efficiency in lung cancer cells over ALC-0315, the industry-standard LNPs, while providing potent immune activation. A single intratumoral injection of H1L1A1B3 LNPs, loaded with circRNA encoding interleukin-12 (IL-12), induced a robust immune response in a Lewis lung carcinoma model, leading to marked tumor regression. Immunological profiling of treated tumors revealed substantial increments in CD45+ leukocytes and enhanced infiltration of CD8+ T cells, underscoring the ability of H1L1A1B3 LNPs to modulate the tumor microenvironment favorably. These results highlight the potential of tailored LNP platforms to advance RNA drug delivery for cancer therapy, broadening the prospects for RNA immunotherapeutics.

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Abstract

The poor bulk-phase and interphase stability, attributable to adverse internal stress, impede the cycling performance of silicon microparticles (μSi) anodes and its commercial application for high-energy-density lithium-ion batteries. In this work, we propose a groundbreaking gradient-hierarchically ordered conductive (GHOC) network structure, ingeniously engineered to enhance the stability of both bulk-phase and the solid electrolyte interphase (SEI) configurations of μSi. Within the GHOC network architecture, two-dimensional transition metal carbides (Ti3C2T x ) acts as a conductive “brick”, establishing a highly conductive inner layer on μSi, while the porous outer layer, composed of one-dimensional Tempo-oxidized cellulose nanofibers (TCNF) and polyacrylic acid (PAA) macromolecule, functions akin to structural “rebar” and “concrete”, effectively preserves the tightly interconnected conductive framework though multiple bonding mechanisms, including covalent and hydrogen bonds. Additionally, Ti3C2Tx enhances the development of a LiF-enriched SEI. Consequently, the μSi-MTCNF-PAA anode presents a high discharge capacity of 1413.7 mAh g−1 even after 500 cycles at 1.0 C. Moreover, a full cell, integrating LiNi0.8Mn0.1Co0.1O2 with μSi-MTCNF-PAA, exhibits a capacity retention rate of 92.0% following 50 cycles. This GHOC network structure could offer an efficacious pathway for stabilizing both the bulk-phase and interphase structure of anode materials with high volumetric strain.

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Sequence-Based Determinants of Aggregation within Protein Condensates

Complex cellular landscapes of proteins include the dense, liquid-like droplet state and the solid-like amyloid state, in addition to the native state. The amyloid state, which is often pathological, can be formed through the deposition pathway from the native state and through the condensation pathway from the droplet state. I present a uniform framework to describe both pathways and identify mutations biasing towards these aggregation mechanisms. The droplet landscape model is a sequence-based, generic approach that simultaneously estimates the probability of droplet formation and the likelihood of state conversion. The method exploits that the interactions driving the droplet state sample disordered binding modes, whereas those governing the amyloid state sample ordered binding modes, which can simultaneously be estimated from sequence without information on the interaction partners. In addition, we predict the multiplicity of binding modes, that a given protein region can sample under different cellular conditions. I will demonstrate the application of the droplet landscape approach to both pathological and functional aggregates, in particular predicting mutations associated with amyotrophic lateral sclerosis and those facilitating muscle lineage development.

References M. Vendruscolo, M Fuxreiter (2022) Protein Condensation Diseases: Therapeutic Opportunities. Nat Commun 13, 5500, doi: 10.1038/s41467-022-32940-7 Hatos A, Tosatto SCE , Vendruscolo M, Fuxreiter M. (2022) FuzDrop on AlphaFold: visualizing the sequence-dependent propensity of liquid-liquid phase separation and aggregation of proteins. Nucleic Acids Res. 50(W1), W337 -44 Gönczi M., Teixeira JMC , Barrera-Vilarmau S., Mediani L. , Antoniani F. , Nagy TM, Fehér K., Ráduly Z., Ambrus V., Tőzsér J., Barta E., Kövér KE., Csernoch L., Carra S. , Fuxreiter M. (2023) Alternatively spliced exon regulates context-dependent MEF2D higher-order assembly during myogenesis Nature Communications 14, 1329. Horvath A, Vendruscolo M, Fuxreiter M. (2022) Sequence-based Prediction of the Cellular Toxicity Associated with Amyloid Aggregation within Protein Condensates Biochemistry 61, 2461-2469.

• Speaker: Professor Monika Fuxreiter, University of Padova
• Wednesday 01 May 2024, 14:30-15:30
• Venue: Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.
• Series: Theory - Chemistry Research Interest Group; organiser: Lisa Masters.

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Energy Environ. Sci., 2024, Accepted Manuscript
DOI: 10.1039/D3EE03004K, Review Article Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Thomas Webb, Saif Ahmed Haque
The development of perovskite solar cells (PSCs) has gone from strength to strength over the last decade, enabling low-cost, flexible and high-efficiency photovoltaic devices. However, the significance of molecular iodine...
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Ocean, ice, and the spherical cow

“Consider a spherical cow in the vacuum…” – that’s how most physics problems start. A very simplified version of the real world that we can wrap our heads around and find answers using pencil and paper. Numerical models that simulate the components of the climate system are no different: we start simple and build it up as scientific knowledge of the system advances and technology allows us to explore smaller-scale processes. My research focuses on understanding ice-ocean interactions, focusing on the behaviour of icebergs and their impacts in the polar oceans, using said models. Join me as I explain my journey towards drawing a cow that looks less like a balloon and more like a quadruped.

• Speaker: Juliana Marson, University of Manitoba
• Wednesday 01 May 2024, 14:00-15:00
• Venue: BAS Seminar Room 1; https://bas-ac-uk.zoom.us/j/93676773793.
• Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Dr Birgit Rogalla.

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Title to be confirmed

Abstract not available

• Speaker: Hannah Dawson, University of Tasmania
• Wednesday 22 May 2024, 13:00-14:00
• Venue: BAS Seminar Room 1; https://bas-ac-uk.zoom.us/j/91268978510.
• Series: British Antarctic Survey - Polar Oceans seminar series; organiser: Dr Birgit Rogalla.

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A Mathematician’s Journey into Biology: Collaboration, Creativity & Opportunities

Abstract not available

• Speaker: Professor Rachel Bearon, Professor of Mathematical Biology and Executive Dean of the Faculty of Natural, Mathematical & Engineering Sciences, KCL
• Thursday 16 May 2024, 12:00-13:00
• Venue: Centre for Mathematical Sciences MR2, CMS.
• Series: Rouse Ball Lectures; organiser: Sarah Jefferys.

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