Metal nanoparticles for microscopy and spectroscopy

Metal nanoparticles interact strongly with light due to a resonant response of their free electrons. These ‘plasmon’ resonances appear as very strong extinction and scattering for particular wavelengths, and result in high enhancements of the local field compared to the incident electric field. In this chapter we introduce the reader to the optical properties of single plasmon particles as well as finite clusters and periodic lattices, and discuss several applications

A bimetallic nanoantenna for directional colour routing

Recent progress in nanophotonics includes demonstrations of meta-materials displaying negative refraction at optical frequencies, directional single photon sources, plasmonic analogies of electromagnetically induced transparency and spectacular Fano resonances. The physics behind these intriguing effects is to a large extent governed by the same single parameter—optical phase. Here we describe a nanophotonic structure built from pairs of closely spaced gold and silver disks that show phase accumulation through material-dependent plasmon resonances. The bimetallic dimers show exotic optical properties, in particular scattering of red and blue light in opposite directions, in spite of being as compact as ∼λ3/100. These spectral and spatial photon-sorting nanodevices can be fabricated on a wafer scale and offer a versatile platform for manipulating optical response through polarization, choice of materials and geometrical parameters, thereby opening possibilities for a wide range of practical applications

Directed emission of CdSe nanoplatelets originating from strongly anisotropic 2D electronic structure

ntrinsically directional light emitters are potentially important for applications in photonics including lasing and energy-efficient display technology. Here, we propose a new route to overcome intrinsic efficiency limitations in light-emitting devices by studying a CdSe nanoplatelets monolayer that exhibits strongly anisotropic, directed photoluminescence. Analysis of the two-dimensional k-space distribution reveals the underlying internal transition dipole distribution. The observed directed emission is related to the anisotropy of the electronic Bloch states governing the exciton transition dipole moment and forming a bright plane. The strongly directed emission perpendicular to the platelet is further enhanced by the optical local density of states and local fields. In contrast to the emission directionality, the off-resonant absorption into the energetically higher 2D-continuum of states is isotropic. These contrasting optical properties make the oriented CdSe nanoplatelets, or superstructures of parallel-oriented platelets, an interesting and potentially useful class of semiconductor-based emitters

Breaking the diffusion limit with super-hydrophobic delivery of molecules to plasmonic nanofocusing SERS structures

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Coloured heat

Stanford University researchers have demonstrated the potential of single SiC whiskers to function as narrowband infrared emitters that have controllable emission characteristics.Peer reviewe

Outcome measures for clinical trials in paediatric IBD: an evidence-based, expert-driven practical statement paper of the paediatric ECCO committee.

OBJECTIVE: Although paediatric-onset IBD is becoming more common, few medications have a registered paediatric indication. There are multiple hurdles to performing clinical trials in children, emphasising the importance of choosing an appropriate outcome measure, which can facilitate enrolment, and thereby also drug approval. The aim of this consensus statement is to highlight paediatric specific issues and key factors critical for the optimal conduct of paediatric IBD trials. DESIGN: The Paediatric European Crohn's and Colitis Organisation (ECCO) committee has established an international expert panel to determine the best outcome measures in paediatric IBD, following a literature search and a modified Delphi process. All recommendations were endorsed by at least 80% agreement. RESULTS: Recognising the importance of mucosal healing (MH), the panel defined steroid-free MH as primary outcome measure for all drugs of new category with one or two postintervention endoscopies per trial (at 8-12 weeks and/or 54 weeks). Since endoscopic evaluation is a barrier for recruitment in children, trials with medications already shown to induce MH in children or adults, could use paediatric-specific disease activity scores as primary outcome, including a modified Paediatric Crohn's Disease Activity Index in Crohn's disease and the Paediatric Ulcerative Colitis Activity Index in UC. Secondary outcomes should include safety issues, MR enterography-based damage and inflammatory scores (in Crohn's disease), faecal calprotectin, quality of life scales, and a patient-reported outcome. CONCLUSIONS: It is crucial to perform paediatric trials early in the development of new drugs in order to reduce off-label use of IBD medication in children. The thoughtful choice of feasible and standardised outcome measures can help move us towards this goal