Extremely short-length surface plasmon resonance sensors

The impact of the system design on the control of coupling between planar waveguide modes and surface plasmon polaritons (SPP) is analyzed. We examine how the efficiency of the coupling can be enhanced by an appropriate dimensioning of a multi-layer device structure without using additional gratings. We demonstrate that by proper design the length of the device can be dramatically reduced through fabrication a surface plasmon resonance sensor based on the SPP-photon transformation rather then on SPP dissipation

Research of Structural, Strength and Thermal Properties of ZrO₂—CeO₂ Ceramics Doped with Yttrium

In this work, using a mechanochemical solid-phase synthesis method, ZrO2—CeO2 ceramics doped with yttrium were obtained, which have great prospects for use as a basis for dispersed nuclear fuel materials or inert nuclear fuel matrices. The purpose of this work was to study the formation of the ZrO2—CeO2 phase composition, depending on the concentration of yttrium dopant, as well as to study their structural and strength properties. The relevance of this study is in obtaining new data on the properties of composite ceramics based on oxides having a cermet structure, as well as the effect of doping with yttrium on increasing the resistance of ceramics to deformation and thermal properties. During the studies, the dynamics of the phase transformations depending on the concentration of the dopant, as well as changes in the structural characteristics and dislocation density, were established. It was found that at a dopant concentration of 0.25 mol, the main phase in the structure was Ce3ZrO8–triclinic P1 (1), the formation of which led to an increase in the mechanical and strength properties of the ceramics as well as a 1.5-fold increase in the thermal conductivity coefficient

The Role of Plasmon-Generated Near Fields for Enhanced Circular Dichroism Spectroscopy

Plasmon-enhanced circular dichroism has established itself as a promising candidate to push the limits of molecular handedness detection to the extremes, namely, toward a monolayer or even to a single molecule. A multitude of intricate mechanisms, both chemical and physical, have to contribute individually or in unison to an enhancement that is large enough that it may bridge the several orders of magnitude of lacking signal strength when detecting small analyte quantities in a circular dichroism scheme. Here, we assess in isolation the contribution arising from electromagnetic interactions between a homogeneous chiral medium and plasmonic structures. Using a suitably modified full-field electromagnetic simulation environment, we are able to investigate the viability of various canonical achiral and chiral plasmonic configurations for substrate-enhanced chiroptical spectroscopy. A clear hierarchy in enhancement factors is revealed that places achiral plasmonic gap antennas at the top, thus outperforming its chiral equivalent, the Born–Kuhn-type plasmonic dimer. Moreover, the importance of coplanarity of the incident rotating circular polarization field vector with the resonantly enhanced field vector in the plasmonic hot-spot is demonstrated. Taking everything into account, we obtain an enhancement of 3 orders of magnitude from purely electromagnetic interactions, thereby charting this part of the CD enhancement landscape

Graphene Plasmon Reflection by Corrugations

Graphene plasmons (GPs) exhibit extreme confinement of the associated electromagnetic fields. For that reason, they are promising candidates for controlling light in nanoscale devices. However, despite the ubiquitous presence of surface corrugations in graphene, very little is known on how they affect the propagation of GPs. Here we perform a comprehensive theoretical analysis of GP scattering by both smooth and sharp corrugations. For smooth corrugations, we demonstrate that scattering of GPs depends on the dielectric environment, being strongly suppressed when graphene is placed between two dielectrics with the same refractive indices. We also show that sharp corrugations can act as effective GP reflectors, even when their dimensions are small in comparison with the GP wavelength. Additionally, we provide simple analytical expressions for the reflectance of GPs valid in an ample parametric range. Finally, we connect these results with potential experiments based on scattering scanning near-field optical microscopy (s-SNOM) showing how to extract the GP reflectance from s-SNOM images

High Catalytic Activity of Vanadium Complexes in Alkane Oxidations with Hydrogen Peroxide: An Effect of 8‑Hydroxyquinoline Derivatives as Noninnocent Ligands

Five monomeric oxovanadium­(V) complexes [VO­(OMe)­(N^∩O)₂] with the nitro or halogen substituted quinolin-8-olate ligands were synthesized and characterized using Fourier transform infrared, ¹H and ¹³C NMR, high-resolution mass spectrometry–electrospray ionization as well as X-ray diffraction and UV–vis spectroscopy. These complexes exhibit high catalytic activity toward oxidation of inert alkanes to alkyl hydroperoxides by H₂O₂ in aqueous acetonitrile with the yield of oxygenate products up to 39% and turnover number 1780 for 1 h. The experimental kinetic study, the C₆D₁₂ and ¹⁸O₂ labeled experiments, and density functional theory (DFT) calculations allowed to propose the reaction mechanism, which includes the formation of HO· radicals as active oxidizing species. The mechanism of the HO· formation appears to be different from those usually accepted for the Fenton or Fenton-like systems. The activation of H₂O₂ toward homolysis occurs upon simple coordination of hydrogen peroxide to the metal center of the catalyst molecule and does not require the change of the metal oxidation state and formation of the HOO· radical. Such an activation is associated with the redox-active nature of the quinolin-8-olate ligands. The experimentally determined activation energy for the oxidation of cyclohexane with complex [VO­(OCH₃)­(5-Cl-quin)₂] (quin = quinolin-8-olate) is 23 ± 3 kcal/mol correlating well with the estimate obtained from the DFT calculations

Strong Plasmon Reflection at Nanometer-Size Gaps in Monolayer Graphene on SiC

We employ tip-enhanced infrared near-field microscopy to study the plasmonic properties of epitaxial quasi-free-standing monolayer graphene on silicon carbide. The near-field images reveal propagating graphene plasmons, as well as a strong plasmon reflection at gaps in the graphene layer, which appear at the steps between the SiC terraces. When the step height is around 1.5 nm, which is two orders of magnitude smaller than the plasmon wavelength, the reflection signal reaches 20% of its value at graphene edges, and it approaches 50% for step heights as small as 5 nm. This intriguing observation is corroborated by numerical simulations and explained by the accumulation of a line charge at the graphene termination. The associated electromagnetic fields at the graphene termination decay within a few nanometers, thus preventing efficient plasmon transmission across nanoscale gaps. Our work suggests that plasmon propagation in graphene-based circuits can be tailored using extremely compact nanostructures, such as ultranarrow gaps. It also demonstrates that tip-enhanced near-field microscopy is a powerful contactless tool to examine nanoscale defects in graphene

Strong Plasmon Reflection at Nanometer-Size Gaps in Monolayer Graphene on SiC

We employ tip-enhanced infrared near-field microscopy to study the plasmonic properties of epitaxial quasi-free-standing monolayer graphene on silicon carbide. The near-field images reveal propagating graphene plasmons, as well as a strong plasmon reflection at gaps in the graphene layer, which appear at the steps between the SiC terraces. When the step height is around 1.5 nm, which is two orders of magnitude smaller than the plasmon wavelength, the reflection signal reaches 20% of its value at graphene edges, and it approaches 50% for step heights as small as 5 nm. This intriguing observation is corroborated by numerical simulations, and explained by the accumulation of a line charge at the graphene termination. The associated electromagnetic fields at the graphene termination decay within a few nanometers, thus preventing efficient plasmon transmission across nanoscale gaps. Our work suggests that plasmon propagation in graphene-based circuits can be tailored using extremely compact nanostructures, such as ultra-narrow gaps. It also demonstrates that tip-enhanced near-field microscopy is a powerful contactless tool to examine nanoscale defects in graphene.Comment: Nano Letters (2013); manuscript + supporting informatio