Optical Mie Scattering by DNA-Assembled Three-Dimensional Gold Nanoparticle Superlattice Crystals

9 pags., 5 figs.Programmable assemblies of gold nanoparticles engineered with DNA have intriguing optical properties such as Coulomb-interaction-driven strong coupling, polaritonic response in the visible range, and ultralow dispersion dielectric response in the infrared spectral range. In this work, we demonstrate the optical Mie resonances of individual microcrystals of DNA-gold nanoparticle superlattices. Broadband hyperspectral mapping of both transmission and dark-field scattering reveal a polarization-insensitive optical response with distinct spectral features in the visible and near-infrared ranges. Experimental observations are supported by numerical simulations of the microcrystals under a resonant effective medium approximation in the regime of capacitively coupled nanoparticles. The study identifies a universal characteristic optical response which is defined by a band of multipolar Mie resonances, which only weakly depend on the crystal size and light polarization. The use of gold superlattice microcrystals as scattering materials is of interest for fields such as complex nanophotonics, thermoplasmonics, photocatalysis, sensing, and nonlinear optics.D.M., H.J.S., A.G.K., and O.L.M. acknowledge financial support by the Leverhulme Trust through Research Grant RPG-2018-251.Peer reviewe

Twist and shout: a surprising synergy between aryl and N-substituents defines the computed charge transport properties in a series of crystalline diketopyrrolopyrroles

This is the Accepted Manuscript version of an article accepted for publication in CyrstEngComm. Under embargo. Embargo end date: 22 November 2017. Jesus Calvo-Castrp, Sebastian Macza, Connor Thomson, Graeme Morris, Alan R. Kennedy and Callum J. McHugh, ‘Twist and shout: a surprising synergy between aryl and N-substituents defines the computed charge transport properties in a series of crystalline diketopyrrolopyrroles’, CrysEngComm, Vol 18(48): 9382-9390, first published online 22 November 2016, available at doi: 10.1039/C6CE02261HThe influence of systematic variation of aryl and N-substitution on predicted charge transport behaviour in a series of crystalline diketopyrrolopyrroles is evaluated. A correct combination of substituents is revealed to maximise those properties which dictate device performance in organic single crystals based upon this structural motif. For electron transport, furan and N-alkyl substitution emerge as optimal molecular design strategies, whilst phenyl structures bearing N-benzyl substituents are shown to offer the most significant promise as highly sought after crystalline hole transport materials.Peer reviewedFinal Accepted Versio

The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing

International audienceCurrent sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans

Tocilizumab in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Background: In this study, we aimed to evaluate the effects of tocilizumab in adult patients admitted to hospital with COVID-19 with both hypoxia and systemic inflammation. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. Those trial participants with hypoxia (oxygen saturation <92% on air or requiring oxygen therapy) and evidence of systemic inflammation (C-reactive protein ≥75 mg/L) were eligible for random assignment in a 1:1 ratio to usual standard of care alone versus usual standard of care plus tocilizumab at a dose of 400 mg–800 mg (depending on weight) given intravenously. A second dose could be given 12–24 h later if the patient's condition had not improved. The primary outcome was 28-day mortality, assessed in the intention-to-treat population. The trial is registered with ISRCTN (50189673) and ClinicalTrials.gov (NCT04381936). Findings: Between April 23, 2020, and Jan 24, 2021, 4116 adults of 21 550 patients enrolled into the RECOVERY trial were included in the assessment of tocilizumab, including 3385 (82%) patients receiving systemic corticosteroids. Overall, 621 (31%) of the 2022 patients allocated tocilizumab and 729 (35%) of the 2094 patients allocated to usual care died within 28 days (rate ratio 0·85; 95% CI 0·76–0·94; p=0·0028). Consistent results were seen in all prespecified subgroups of patients, including those receiving systemic corticosteroids. Patients allocated to tocilizumab were more likely to be discharged from hospital within 28 days (57% vs 50%; rate ratio 1·22; 1·12–1·33; p<0·0001). Among those not receiving invasive mechanical ventilation at baseline, patients allocated tocilizumab were less likely to reach the composite endpoint of invasive mechanical ventilation or death (35% vs 42%; risk ratio 0·84; 95% CI 0·77–0·92; p<0·0001). Interpretation: In hospitalised COVID-19 patients with hypoxia and systemic inflammation, tocilizumab improved survival and other clinical outcomes. These benefits were seen regardless of the amount of respiratory support and were additional to the benefits of systemic corticosteroids. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

Background: Many patients with COVID-19 have been treated with plasma containing anti-SARS-CoV-2 antibodies. We aimed to evaluate the safety and efficacy of convalescent plasma therapy in patients admitted to hospital with COVID-19. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]) is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. The trial is underway at 177 NHS hospitals from across the UK. Eligible and consenting patients were randomly assigned (1:1) to receive either usual care alone (usual care group) or usual care plus high-titre convalescent plasma (convalescent plasma group). The primary outcome was 28-day mortality, analysed on an intention-to-treat basis. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings: Between May 28, 2020, and Jan 15, 2021, 11558 (71%) of 16287 patients enrolled in RECOVERY were eligible to receive convalescent plasma and were assigned to either the convalescent plasma group or the usual care group. There was no significant difference in 28-day mortality between the two groups: 1399 (24%) of 5795 patients in the convalescent plasma group and 1408 (24%) of 5763 patients in the usual care group died within 28 days (rate ratio 1·00, 95% CI 0·93–1·07; p=0·95). The 28-day mortality rate ratio was similar in all prespecified subgroups of patients, including in those patients without detectable SARS-CoV-2 antibodies at randomisation. Allocation to convalescent plasma had no significant effect on the proportion of patients discharged from hospital within 28 days (3832 [66%] patients in the convalescent plasma group vs 3822 [66%] patients in the usual care group; rate ratio 0·99, 95% CI 0·94–1·03; p=0·57). Among those not on invasive mechanical ventilation at randomisation, there was no significant difference in the proportion of patients meeting the composite endpoint of progression to invasive mechanical ventilation or death (1568 [29%] of 5493 patients in the convalescent plasma group vs 1568 [29%] of 5448 patients in the usual care group; rate ratio 0·99, 95% CI 0·93–1·05; p=0·79). Interpretation: In patients hospitalised with COVID-19, high-titre convalescent plasma did not improve survival or other prespecified clinical outcomes. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Tungsten doped vanadium dioxide via atomic layer deposition with tailored thermochromic electrical and optical response

With the rise of world temperatures due to global warming, the importance of efficient cooling has increased drastically. Radiative coolers provide a route to effectively emit thermal energy into space. In areas with large diurnal ranges or seasonal temperature variations, however, constant cooling is undesired. Self-adaptive radiative coolers can produce large radiated power at high temperatures and reduced radiated power at low temperatures by passively varying their emissivity (ε). These devices rely upon thermochromic materials, which undergo large changes in their material, optical, and electrical response due to a temperature-driven phase transition. These transitions are induced through the addition of thermal energy by absorbing radiation, Joule heating, or conduction. One such material that exhibits these characteristics is vanadium dioxide - VO2 - a solid-solid phase change material that can reliably switch between its low temperature monoclinic and high-temperature rutile phase around 69 °C. By doping, the thermochromic response can be tailored, extending the material uses to areas including smart windows, memristors, and sensing. For these applications, thin-film devices provide a route for low-cost, lightweight structures with enhanced performance through smart metamaterial and multilayer design. The performance of such devices is highly dependent upon film quality and thickness control. By utilising the novel atomic layer deposition (ALD) of VO2 and W-doped VO2 thin films, devices were produced with adjusted thermochromic responses for a variety of optical and electrical applications. A patterned VO2 metasurface deposited upon an optimised Salisbury screen stack for enhanced infrared IR absorption was fabricated, creating a smart IR emitter with high visual transparency – a smart window. The VO2 thermal emitter demonstrated a tuneable IR emissivity (∆ε) of 0.26, with a 62 % improvement in solar transmittance by the metasurface patterned design compared to its planar counterpart, attributed to the reduced VO2 coverage. The device displays much greater radiated powers under daytime illumination owing to the increased high temperature ε of the device for terrestrial and space applications, displaying the suitability of the design for use in both environments. Reduction of the transition temperature of VO2 films to room temperature was demonstrated through doping with W. By varying the W/V cycle ratio during ALD deposition, five uniform W-doped VO2 stacks with different W concentrations were fabricated and characterised. Predictable control of the transition temperature was shown to be possible while maintaining material and optical performance. By parameterising their temperature dependent electrical response, a novel model was proposed to predict the thermochromic resistivity response of W:VO2 films based on their W doping at.%. Optimised multilayer W:VO2 device designs were then simulated for use as high-sensitivity microbolometers with extended phase transition responses across chosen operating temperature windows.To experimentally demonstrate the extended phase transition of multilayer doped W:VO2 stacks, several films were fabricated with thickness and W doping control using ALD. Three W:VO2 devices on high ε SiO2 were fabricated and optically tested, with each displaying a negative thermochromic ε response for optical stealth. Two additional multilayer W:VO2 devices were manufactured as high-sensitivity microbolometers across two operating temperature windows. Depth-resolved XPS verified a W gradient through the as-deposited films of ∆W ≈ 0.7 and 2.0 at.%. Their electrical thermochromic performances were assessed, with both stacks displaying a convoluted bi-layer response indicative of two distinct W:VO2 layers within a single film. This is the first demonstration of an extended phase transition multilayer W:VO2 device deposited by ALD, opening new pathways for VO2 material control.<br/

Dataset supporting the thesis titled &quot;Tungsten Doped Vanadium Dioxide via Atomic Layer Deposition with Tailored Thermochromic Electrical and Optical Response&quot;

This dataset supports the thesis entitled &#39;Tungsten Doped Vanadium Dioxide via Atomic Layer Deposition with Tailored Thermochromic Electrical and Optical Response&#39;, awarded by the University of Southampton in 2024 DESCRIPTION OF THE DATA: The attached dataset is in support of the data presented in this thesis. Data presented in Chapters 4 and 5 is published and accessible online, with the DOI&#39;s listed in the Related publications section below. Data is presented in the attached .xlsx file, split by tabs corresponding to the associated Figure number in the thesis. Ellipsometry data is not inlcuded in these data files. Data for Figure 32 can be found in full in Figure S2 and 3. Figures 49, 50, 51 data is extracted from the resistivity data presented in Figure 48. This dataset contains: Data collected on a set of W-doped VO2 thin films deposited via ALD for tailored optical and electrical responses. These were measured using a wide range of spectroscopic and electrical measurement tools including: Depth resolved and surface X-ray Photoelectron spectroscopy; Raman spectroscopy; Hall Probe measurements; Fourier-Transform Infrared spectroscopy; Date of data collection: 10/20 - 04/24</span

Fabrication of Large-Area Metal Oxide Infrared Metasurfaces

We present recent developments for the fabrication of functional metasurfaces in the mid- and long-wave infrared using 200mm wafer scale nanofabrication techniques. Our results include deep-UV scanner lithography of multi-band metasurfaces with tailored reflectivities in the two atmospheric windows. Also we will show recent results on smart radiative cooling metasurfaces based on atomic layer deposition of W:VO2

Wafer‐Scale 200 mm Metal Oxide Infrared Metasurface with Tailored Differential Emissivity Response in the Atmospheric Windows

International audienceMetasurfaces with sub-wavelength nanoscale features have emerged as a platform to achieve desirable electromagnetic responses. However, it remains technically challenging to fabricate metasurfaces in large size and at low cost for mass production. This work demonstrates a 200 mm wafer-scale Al:ZnO metasurface coating based on deep-UV lithography. The metasurfaces are targeted to achieve infrared (IR) reflectivity and emissivity characteristics at bandwidths across the two atmospheric windows in the IR spectrum. The wafers demonstrate a high uniformity of optical response with tailored reflectivity of around 50% at the 3–5 µm mid-wave IR band and less than 10% at the 8–13 µm long-wave IR band. This article furthermore shows that the design principle allows achieving a wide range of dual-band reflectivity values using a single underlying materials stack, offering a versatile platform. The proposed approach is compatible with CMOS-compatible mass-production manufacturing and brings IR metasurface coatings closer to commercially relevant and scalable technology

Dataset to support the journal article: VO2 Metasurface Smart Thermal Emitter with High Visual Transparency for Passive Radiative Cooling Regulation in Space and Terrestrial Applications

Simulation results and optical spectra of devices, the dataset consists of a single excel file with spreadsheet for each subfigure/figure presented in the paper</span