Influence of the Local Field and Dipole-Dipole Interactions on the Spectral Characteristics of Simple Metals and Their Nanoparticles

The effect of dipole-dipole interactions of free electrons on the spectral characteristics of simple metals and their nanoparticles is analyzed using Drude theory and the model of the Lorentz local field. It is established that accounting for the dispersion of a local field under conditions of one-dimensional (1D) confinement based on the optical constants of the bulk metal allows the determination of its spectral micro-characteristics in the frequency region of the longitudinal collective motions of the free electrons. This corresponds to the spectra of the dielectric losses of bulk plasma oscillations. A similar procedure for three-dimensional (3D) confinement produces the spectrum of dielectric losses at the frequency of localized plasma oscillations. Using a number of simple metal examples, viz., Li, Na, and K, and also Al, Be, and Mg, it is shown that the frequencies of volume and localized plasma oscillations obtained from a model of dispersion of the local field in the long-wave limit are in good agreement with the actual frequencies of the plasma oscillations of the corresponding metals and the absorption maxima of their nanoparticles with a radius of 2–20 nm. It is shown that the frequencies of the main mode of longitudinal plasma oscillations and the absorption frequency of localized plasmons are well described using the dynamic theory of crystal lattice vibrations

Reversal and pinning of Curie point transformations in thin film piezoelectrics

The Curie point for a rhombohedral piezoelectric thin film was established by in situ micro-Raman spectroscopy. The hysteresis in phase reversal and specific thermal conditions for disrupting such reversal were determined

Raman spectroscopy as a tool for characterisation of liquid phase devices

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordIn this paper, we demonstrate how Raman spectroscopy can be an effective tool for the elucidation of the properties of liquid phase devices, looking at signal enhancement through to beam profiling

In-situ optical characterisation of the spatial dynamics of liquid crystalline nanocomposites

Liquid crystalline nanocomposites are a novel class of hybrid fluid materials, which are currently attracting significant interest from the photonics community. Such fluid nano-composites are based on low-dimensional nanoparticles (carbon nanotubes, graphene, transition metal dichalcogenides (TMDCs), metal nanoparticles etc.) dispersed in a fluidic host material. Liquid crystalline properties can either be provided by using a liquid crystal host fluid, or, through the solvent-induced self-assembly of particles. They possess a unique capability to interact with light, utilising many possibilities in plasmonics and quantum optics while they can also be integrated on Si chip by means of microfluidic technology. Integration of the nanocomposites on chip allows for dynamic control of the dispersed particle ordering through the application of various external stimuli. However, this dynamic control requires a suitable characterisation technique to fully understand the time evolution of metastructure formation. Integrated nanocomposites are characterised by the particle concentration at different points on chip, while the individual particles are defined by their sizes, xyz positions and orientation relative to the chip architecture. Here, we present a method by which all the required information for complete characterisation of the system can be obtained using a single spectroscopic technique- Raman spectroscopy- and how changes in the system can then be monitored during device operation. Liquid crystalline nanocomposites have been synthesised based on two-dimensional (2D) materials including graphene oxide (GO) and TMDCs dispersed in either commercially available liquid crystals or various organic solvents. We present both numerical analysis of the theoretical practicability of the use of Raman spectroscopy to extrapolate the desired nanocomposite properties and the experimental confirmation of the achievability of these measurements for the full range of synthesised nanocomposites

Ultra-sensitive label-free in-situ detection of dynamically driven self-assembly of 2D nanoplatelets on SOI chip

Fluid dispersed two-dimensional (2D) composite materials with dynamically tunable functional properties have recently emerged as a novel highly promising class of optoelectronic materials, opening up new routes not only for the emerging field of metamaterials but also to chip-scale multifunctional metadevices. However, in-situ monitoring and detection of the dynamic ordering of 2D nanoparticles on chip and during the device operation is still a huge challenge. Here we introduce a novel approach for on-chip, in-situ Raman characterisation of 2D-fluid composite materials incorporated into Si photonics chip. In this work the Raman signal for 2D nanoplatelets is selectively enhanced by Fabry-Perot resonator design of CMOS photonic-compatible microfluidic channels. This has then been extended to demonstrate the first in-situ Raman detection of the dynamics of individual 2D nanoplatelets, within a microfluidic channel. Our work paves the way for the first practicable realisation of 3D photonic microstructure shaping based on 2D-fluid composites and CMOS photonics platform.We acknowledge financial support from: the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the EPSRC Centre for Doctoral Training in Electromagnetic Metamaterials (Grant No. EP/L015331/1) and also via Grants No. EP/G036101/1, EP/M002438/1, and EP/M001024/1, Science Foundation Ireland Grant No. 12/IA/1300, the Ministry of Education and Science of the Russian Federation (Grant No. 14.B25.31.0002) and the Royal Society International Exchange Grant 2015/R3. The microfluidic structures were fabricated at Tyndall National Institute under the Science Foundation Ireland NAP368 and NAP94 programmes

Micro-Raman Study of Stress Distribution Generated in Silicon During Proximity Rapid Thermal Diffusion

proximity rapid thermal diffusion (RTD). A compressive stress was found on the whole silicon wafer after 15 s RTD. After 165 s RTD, the distribution of the stress across the wafer was found to be different: compressive at the edge and tensile at the middle. Thermal stress was relieved in the RTD wafers via slip dislocations. These slip dislocations were observed in the product wafers using optical microscopy. Slip lines propagated from the wafer edge to the wafer centre in eight preferred positions of maximum induced stress. The thermally induced stress and the slip dislocation density increased with time spent at the RTD peak temperature

Micro-Raman Mapping of 3C-SiC Thin Films Grown by Solid–Gas Phase Epitaxy on Si (111)

A series of 3C-SiC films have been grown by a novel method of solid–gas phase epitaxy and studied by Raman scattering and scanning electron microscopy (SEM). It is shown that during the epitaxial growth in an atmosphere of CO, 3C-SiC films of high crystalline quality, with a thickness of 20 nm up to few hundreds nanometers can be formed on a (111) Si wafer, with a simultaneous growth of voids in the silicon substrate under the SiC film. The presence of these voids has been confirmed by SEM and micro-Raman line-mapping experiments. A significant enhancement of the Raman signal was observed in SiC films grown above the voids, and the mechanisms responsible for this enhancement are discussed

NITRIC OXIDE – BIOCHEMICAL MARKER OF TUBERCULOSIS PATHOGENESIS

Role of nitric oxide in the pathogenesis of pulmonary tuberculosis has been studied in 77 patients with new infiltrate pulmonary tuberculosis and 34 patients with fibrous cavernous pulmonary tuberculosis. The level of cumulative and endogenous nitrite depended on the clinical form of tuberculosis: in infiltrate pulmonary tuberculosis patients it was within the limits of reference ranges, and in fibrous cavernous pulmonary tuberculosis patients it was significantly lower. Results of statistical analysis point out at the significant homogeneity (monofunctionality) of the set of rates, defining the level of NO metabolites in blood serum in infiltrate pulmonary tuberculosis, namely: impact of adenosine deaminase, levels of α1-protease inhibitor, ceruleoplasmin and age. On the contrary in case of fibrous cavernous pulmonary tuberculosis the diverse (multi-functional) complexes were detected including clinical blood rates providing influence on the reduction of NO level in blood. Nitric oxide in the patients with both clinical forms of tuberculosis correlated with classical markers of system inflammatory response, thus nitric oxide can be regarded as an integral component of inflammatory response with potential evaluation of prognosis of specific lesions during follow-up of changes