Split Ring Resonator (SRR) based metamaterials

Abstract Metamaterials are artificial materials that are known to produce extraordinary electromagnetic responses due to their constituent artificially-engineered micro- or nanostructures of dimensions smaller than that of the wavelength of light. The Split ring resonator (SRR) is such a nanostructure that forms the basic unit of a metamaterial. Since the dimensions of the SRRs are required to be smaller than the resonance wavelength, it becomes critical when response is required at the near infrared and optical wavelengths. In this thesis the various properties of the nanoscale SRRs are studied that resonates in the infrared and visible spectrum. The SRRs mentioned in this thesis are made of both aluminium and gold and have been fabricated on silicon and silica substrates using standard electron beam lithography (EBL) techniques. The effect of different metals (Al and Au) on the resonance of SRRs is studied. A substantial shift is reported, in the response of arrays of similarly sized SRRs, made respectively of aluminium and of gold. It is shown that by using aluminium based SRRs instead of gold; the magnetic resonance of SRRs can be shifted into the visible spectrum. The effect of titanium adhesion layers on the properties of SRRs are considered and it is shown that even a 2 nm thin layer of titanium can red-shift the SRR resonance by 20 nm. It is shown, that by adding asymmetry between the geometries of similar sizes SRRs, it is possible to produce a steeper resonance response, thereby increasing the quality factor of the SRRs. This steep response of asymmetric split ring resonators (A-SRRs) are utilised for the optical detection of very thin film organic compounds. It is further shown that by localising the organic compound to specific regions of the A-SRRs, greater enhancement in optical detection could be achieved. Finally, the same property of A-SRRs are utilised for the enhanced detection and differentiation between different DNA strands

Enhanced fano resonance of organic material films deposited on arrays of asymmetric split-ring resonators (A-SRRs)

Depositing very thin organic films on the surface of arrays of asymmetric split-ring resonators (A-SRRs) produces a shift in their resonance spectra that can be utilized for sensitive analyte detection. Here we show that when poly-methyl-methacrylate (PMMA) is used as an organic probe (analyte) on top of the A-SRR array, the phase and amplitude of a characteristic molecular Fano resonance associated with a carbonyl bond changes according to the spectral positions of the trapped mode resonance of the A-SRRs and their plasmonic reflection peaks. Furthermore, we localize blocks of PMMA at different locations on the A-SRR array to determine the effectiveness of detection of very small amounts of non-uniformly distributed analyte

Mapping the sensitivity of split ring resonators using a localized analyte

Split ring resonator (SRR) based metamaterials have frequently been demonstrated for use as optical sensors of organic materials. This is made possible by matching the wavelength of the SRR plasmonic resonance with a molecular resonance of a specific analyte, which is usually placed on top of the metal structure. However, systematic studies of SRRs that identify the regions that exhibit a high electric field strength are commonly performed using simulations. In this paper we demonstrate that areas of high electric field strength, termed “hot-spots,” can be found by localizing a small quantity of organic analyte at various positions on or near the structure. Furthermore, the sensitivity of the SRR to the localized analyte can be quantified to determine, experimentally, suitable regions for optical sensing

Studies in catalytic dehydrogenation: Part X-Syntheses of alkylsubstituted spirol[4,6]undecanes and dehydrogenation of 1-ethyl-8,9- benzospiro[4,6]undecane

768-77

Two-dimensional (2D) d-Silicates from abundant natural minerals

In the last decade, the materials community has been exploring new 2D materials (graphene, metallene, TMDs, TMCs, MXene, among others) that have unique physical and chemical properties. Recently, a new family of 2D materials, the so-called 2D silicates, have been proposed. They are predicted to exhibit exciting properties (such as high catalytic activity, piezoelectricity, and 2D magnetism). In the current work, we demonstrate a generic approach to the synthesis of large-scale 2D silicates from selected minerals, such as Diopside (d). Different experimental techniques were used to confirm the existence of the 2D structures (named 2D-d-silicates). DFT simulations were also used to gain insight into the structural features and energy harvesting mechanisms (flexoelectric response generating voltage up to 10 V). The current approach is completely general and can be utilized for large-scale synthesis of 2D silicates and their derivatives, whose large-scale syntheses have been elusive

Array metasurfaces for biomedical sensing at infra-red wavelengths

Detection and identification of biomedically significant molecules is an important application in infra-red (IR) spectroscopy. This presentation will consider some of the significant features of the different alternative building-block elements that can be used in array metasurfaces for enhanced detection sensitivity. The presentation will also address techniques and issues associated with the deposition and localisation of biological and organic chemical molecular material for detection and measurement using IR spectroscopy

Phonon Polaritons Assisted Extraordinary Transmission in α-MoO-Silver Grating and Its Application in Switching<sub/>

Sub-wavelength metal grating structures exhibit extraordinary transmission (EOT) due to constructive interference of surface plasmon polaritons (SPPs) tunneling. Phonon polaritons (PhPs) having several advantages over metal-supported plasmons, such as zero ohmic loss and larger propagation lengths, can further enhance the transmission. We propose the design of silver gratings filled with anisotropic Molybdenum Trioxide (&#x03B1; - MoO3) to exhibit EOT by utilizing PhPs. We also numerically demonstrate the tunability (amplitude) of EOT by introducing a layer of graphene nanoribbon in the proposed device and show its application as a mid-infrared switch with bandwidth of 650 nm. &#x03B1;-MoO3&#x002F;silver grating produces normalized transmission as high as &#x223C;5.5 for [100] and &#x223C;6 for [001] crystalline directions. This extraordinary effect is attributed to the formation of (i) hybrid modes, specifically cavity modes coupled with SPPs outside the reststrahlen band (RB) and (ii) cavity modes coupled with PhPs inside the RB. The reported work can be employed in diverse applications including molecular sensing, space communications, remote controlling and, imaging

Berechnung von Zuverlaessigkeits- und Sicherheitskenngroessen der Hardware periodisch gepruefter einkanaliger Automatisierungseinrichtungen

Copy held by UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Road Map to Understanding SARS-CoV-2 Clinico-Immunopathology and COVID-19 Disease Severity

SARS-CoV-2, a novel coronavirus, was first identified in Wuhan, China in December 2019. The rapid spread of the virus worldwide prompted the World Health Organization (WHO) to declare COVID-19 a pandemic in March 2020. COVID-19 discontinuing&rsquo;s a global health crisis. Approximately 80% of the patients infected with SARS-CoV-2 display undetectable to mild inflammation confined in the upper respiratory tract. In remaining patients, the disease turns into a severe form affecting almost all major organs predominantly due to an imbalance of innate and adaptive arms of host immunity. The purpose of the present review is to narrate the virus&rsquo;s invasion through the system and the host&rsquo;s reaction. A thorough discussion on disease severity is also presented regarding the behavior of the host&rsquo;s immune system, which gives rise to the cytokine storm particularly in elderly patients and those with comorbidities. A multifaceted yet concise description of molecular aspects of disease progression and its repercussion on biochemical and immunological features in infected patients is tabulated. The summary of pathological, clinical, immunological, and molecular accounts discussed in this review is of theranostic importance to clinicians for early diagnosis of COVID-19 and its management