Tuning localized plasmons in nanostructured substrates for surface-enhanced Raman scattering

Comprehensive reflectivity mapping of the angular dispersion of nanostructured arrays comprising of inverted pyramidal pits is demonstrated. By comparing equivalently structured dielectric and metallic arrays, diffraction and plasmonic features are readily distinguished. While the diffraction features match expected theory, localised plasmons are also observed with severely flattened energy dispersions. Using pit arrays with identical pitch, but graded pit dimensions, energy scaling of the localised plasmon is observed. These localised plasmons are found to match a simple model which confines surface plasmons onto the pit sidewalls thus allowing an intuitive picture of the plasmons to be developed. This model agrees well with a 2D finite-difference time-domain simulation which shows the same dependence on pit dimensions. We believe these tuneable plasmons are responsible for the surface-enhancement of the Raman scattering (SERS) of an attached layer of benzenethiol molecules. Such SERS substrates have a wide range of applications both in security, chemical identification, environmental monitoring and healthcare

Molecules in the mirror: how SERS backgrounds arise from the quantum method of images

The Raman coupling of light to molecular vibrations is strongly modified when they are placed near a plasmonic metal surface, with the appearance of a strong broad continuum background in addition to the normal surface-enhanced Raman scattering (SERS) peaks. Using a quantum method of images approach, we produce a simple but quantitative explanation of the inevitable presence of the background, due to the resistive damping of the image molecule. This model thus suggests new strategies for enhancing the SERS peak to background ratio

Benefit `myths'? The accuracy and inaccuracy of public beliefs about the benefits system

There is a widespread assumption that increasingly negative public attitudes to the benefits system are due to ‘myths’ held by the British public. However, there is little prior research on whether the public believe these ‘myths’, nor critical scrutiny of benefit ‘truths’. This paper therefore investigates what British people believe about the benefits system, and the extent to which these beliefs can be regarded as correct. To do this, we use 46 measures from 18 datasets, and compare these perceptions to true figures obtained from a variety of sources. We find that – against expectations – there are some areas where people misperceive the benefits system in ways that do not seem likely to lead to harsh attitudes, or where the public are (on average) relatively accurate. Yet overall, our evidence shows that the British public do have low levels of understanding of the benefits system, primarily in ways that seem likely to undermine public support. People wildly overestimate unemployment benefits compared to pensions, and also overestimate how much unemployment claimants without children receive. Half of people believe that out-of-work benefit claims have risen in the past fifteen years, whereas they have fallen noticeably. And while it is difficult to know the true level of benefit fraud exactly, the public overestimate fraud compared to any reasonable figure. We conclude by discussing the implications for both understanding and changing attitudes towards benefits

Seeing Quantised Polaritons without Condensation

Exciton polaritons in high quality semiconductor microcavities can travel long macroscopic distances (>100μm) due to their ultra-light effective mass. The polaritons are repelled from the optically-pumped exciton reservoirs where they are formed, however their spatial dynamics is not as expected for point-like particles. Instead we show polaritons emitted into waveguides travel orthogonally to the repulsive potential gradient, and can only be explained if they are emitted as macroscopic delocalised quantum particles, even before they form Bose condensates

Localized Nanogap Plasmonics for Extreme nanophotonics from ultrathin metallic gaps

Ultrathin dielectric gaps between metals can trap plasmonic optical modes with surprisingly low loss and with volumes below 1nm3. We review the origin and subtle properties of these modes, and show how they can be well accounted for by simple models. Particularly important is the mixing between radiating antenna and confined nanogap modes, which is extremely sensitive to precise nano-geometry, right down to the single atom level. Coupling nanogap plasmons to electronic and vibronic transitions yields a host of phenomena including single-molecule strong coupling and molecular optomechanics, opening access to atomic-scale chemistry and material science, and quantum metamaterials. Ultimate low-energy devices such as robust bottom-up assembled single-atom switches are thus in prospect

Disabled but not deserving? The perceived deservingness of disability welfare benefit claimants

While disability benefits make up the largest group of claimants in high-income countries, we know surprisingly little about which disabled people are seen as ‘deserving’ benefits, nor whether different people in different countries judge deservingness-related characteristics similarly. This is surprising given they are increasingly the focus of retrenchment, which often affirms the deservingness of ‘truly deserving’ disabled people while focusing cuts and demands on those ‘less deserving’. This paper addresses this gap using two vignette-based factorial survey experiments: (i) the nine-country ‘Stigma in Global Context-Mental Health Study’ (SGC-MHS); (ii) a new YouGov survey in Norway/the UK, together with UK replication. I find a hierarchy of symptoms/impairments, from wheelchair use (perceived as most deserving), to schizophrenia and back pain, fibromyalgia, depression, and finally asthma (least deserving). Direct manipulations of deservingness-related characteristics also influence judgements, including membership of ethnic/racial ingroups and particularly blameworthiness and medical legitimation. In contrast, the effects of work ability, age and work history are relatively weak, particularly when compared to the effects on unemployed claimants. Finally, for non-disabled unemployed claimants, I confirm previous findings that right-wingers respond more strongly to deservingness-related characteristics, but Norwegians and Britons respond similarly. For disabled claimants, however, the existing picture is challenged, with e.g. Britons responding more strongly to these characteristics than Norwegians. I conclude by drawing together the implications for policy, particularly the politics of disability benefits, the role of medical legitimation, and the legitimacy challenges of the increasing role of mental health in disability benefit recipiency

Hot electron science in plasmonics and catalysis: what we argue about.

Hot electron photochemistry has made strong claims for improved control of chemical reactions. Here I discuss these claims in the light of a plethora of model experiments and theories, asking what are the key issues to solve. I particularly highlight the need to understand nanoscale thermal hot-spots, thermal gradients, and thermal transport, as well as the conventional optical confinement in plasmonics. I note how the 'direct electron transfer' process seems to dominate, and resembles well known 'indirect excitons' in semiconductor quantum wells. I believe a crucial advance still required is a prototype nano-confined geometry which allows reactants and products to access a well-controlled metallic atomic surface

Reality science

Another panel reviewing grants. Hours of argument when, with the funding available, only the top-rated one will get funded. I sigh. Surely there might be other ways..

Perceptions of social mobility in Britain are characterised by a strange paradox

How meritocratic do Britons think their country is? The question of perceptions has been relatively understudied but is nonetheless important. Declan Gaffney and Ben Baumberg find that while people overwhelmingly agree that children from richer families have more opportunities, they also believe that family wealth is a relatively minor factor in determining outcomes. Factors like hard work and ambition are seen as much more important