Narrowband Deep-Blue Multi-Resonance Induced Thermally Activated Delayed Fluorescence: Insights from the Theoretical Molecular Design

Multi-resonance thermal activated delayed fluorescence (MR-TADF) has been promising with large oscillator strength and narrow full width at half maxima of luminescence, overcoming the compromise of emission intensity and energy criteria of traditional charge transfer TADF frameworks. However, there are still limited theoretical investigations on the excitation mechanism and systematic molecular manipulation of MR-TADF structures. We systematically study the highly localized excitation (LE) characteristics based on typical blue boron-nitrogen (BN) MR-TADF emitters and prove the potential triangular core with theoretical approaches. A design strategy by extending the planar π-conjugate core structure is proposed to enhance the multiple resonance effects. Moreover, several substituted groups are introduced to the designed core, achieving color-tunable functions with relatively small energy split and strong oscillator strength simultaneously. This work provides a theoretical direction for molecular design strategy and a series of potential candidates for highly efficient BN MR-TADF emitters.

Understanding Disorder in Rectangular Dielectric Microcavity CROWs (Project Report 0642603-Y2)

This NSF-funded project [0642603] is a five-year (60 months) CAREER (Faculty Early Career Development Program) unified research and education development program, which focused on the physics and applications of optical waveguiding in the CROW (Coupled Resonator Optical Waveguide) structure. The CROW structure is suitable as the foundation of this project because it offers a very high four-wave mixing (FWM) nonlinearity based on the slow-light effects on each of the pump, signal and idler modes. The triple resonance effects can result in a large improvement of the nonlinear coefficient even with a modest improvement of the slowing factor. However, understanding the effects of disorder in CROWs is important, since it can limit the amount of slowing that can be achieved, and hence, the enhancement of slow-light enhanced nonlinearity.

Неэмпирический анализ изотопических сдвигов и резонансных эффектов в инфракрасном спектре высокого разрешения фреона-22 (CHF-=SUB=-2-=/SUB=-Cl), обогащенного -=SUP=-13-=/SUP=-C

The IR transmittance spectrum of an isotopic mixture of chlorodifluoromethane (CHF2Cl, Freon-22) with a 33% fraction of 13C and a natural ratio of chlorine isotopes was measured in the frequency range 1400-740 cm–1 with a resolution of 0.001 cm–1 at a temperature of 20C. An ab initio calculation of the structure and sextic potential energy surface and surfaces of the components of the dipole moment has been carried out by the the electronic quantum-mechanical method of Möller-Plesset, MP2/cc-pVTZ. Then the potential was optimized by replacing the harmonic frequencies with the frequencies calculated by the electronic method of coupled clusters, CCSD(T)/aug-cc-pVQZ. The fundamental and combination frequencies were calculated using the operator perturbation theory of Van Vleck (CVPTn) of the second and fourth order (n=2,4). Resonance effects were modeled using an additional variational calculation in the basis up to fourfold VCI excitation (4). The average prediction error for the fundamental frequencies of the 12C isotopologues was ~1.5 cm–1. The achieved accuracy made it possible to reliably predict the isotopic frequency shifts of the 13C isotopologues. It is shown that the strong Fermi resonance ν4/2ν6 dominates in the 12C isotopologues and is practically absent in 13C. The literature assumption [Spectrochim. Acta A, 44: 553] about the splitting of ν1 (CH) due to the resonance ν1/ν2+ν7+ν9 is confirmed. The coefficients of the polyadic quantum number are determined. The analysis made it possible to carry out a preliminary identification of the centers of the vibrational-rotational bands of isotopologues 13CHF235Cl и 13CHF237Cl in the spectrum of the mixture in preparation for individual analyzes of the vibrational-rotational structures of individual vibrational transitions.

Quantitative Estimate of the Resonance Effects in some Unsaturated, Monocyclic, and Aromatic Hydrocarbons Based on the Renewed Optical Exaltations

: The present review discusses a new viewpoint on refractometry as the oldest experimental physical method, whose scientific potential in the estimation of structural effects in organic chemistry has been missed so far. The author demonstrates that upon certain adjustment and redesign of refractometry, this potential can be tapped and successfully used to determine a type of Π-electron interaction, delocalization degree of Π-electrons in organic compounds, and to perform quantitative estimates of resonance effects in unsaturated, (polycyclic) aromatic, and other polyconjugated systems (e.g., fullerenes). The method for accurate separation of molar refraction into additive and constitutive components was suggested; the method is based on the specially developed additive scheme. It was revealed that the negative deviations from additivity for cycloalkanes depend linearly on the number of carbon atoms in the ring. Excellent linear correlations between renewed optical exaltations, the number of Π-electrons in a conjugated system, and experimentally found resonance energy (determined from hydrogenation heat values) were demonstrated. Angular coefficients of the correlation series (ρ-constants) are considered as a criterion of classification, which characterizes the degree of mobility of Π-electrons in the conjugated system of a given type. It is emphasized that the development of methods for precise measurement of the constitutive components of molar refraction may become a useful additional source of information about resonance and other effects in organic and polymer chemistry.

An Analysis of Kikuchi Lines Observed with a RHEED Apparatus for a TiO2-Terminated SrTiO3 (001) Crystal

In this study, electron diffraction patterns observed under high vacuum conditions for an SrTiO3 surface were interpreted in detail while paying special attention to the features of inelastic effects. The surface of the SrTiO2 was carefully prepared to enforce its termination with single domains of TiO2 layers at the top. The inelastic patterns were interpreted using analytical models. Two types of Kikuchi lines are recognized in this paper: those which can be described with the Bragg law and those which appear due to surface wave resonance effects. However, we also discuss that there exists a formal connection between the two types of the Kikuchi lines observed.

Numerical Approach for Detecting the Resonance Effects of Drilling during Assembly of Aircraft Structures

This paper is devoted to the development of a numerical approach that allows quick detection of the conditions favorable for the beginning of noticeable vibrations during drilling. The main novelty of the proposed approach lies in taking into account the deviations of the assembled compliant parts during non-stationary contact analysis by means of variation simulation. The approaches to stationary analysis of assembly quality are expanded and generalized for modeling such non-stationary effects as vibration and resonance. The numerical procedure is based on modeling the stress–strain state of the assembled structures by solving the corresponding transient contact problem. The use of Guyan reduction, the node-to-node contact model and the application of the generalized α method allow the reformulation of the contact problem in terms of a series of quadratic programming problems. The algorithm is thoroughly tested and validated with commercial software. The efficiency of the developed numerical procedure is illustrated by analysis of the test joints of two aircraft panels. The unsteady process of drilling the panels with periodic drilling force was simulated. The influence of deviations in the shape of the parts on the non-stationary interlayer gap was modeled by setting different initial gaps between parts. It is shown that the oscillation amplitudes of the interlayer gap depend on the initial gaps and do not correlate with the mean value of the stationary residual gap. Thus, non-stationary analysis provides new information about the quality of the assembly process, and it should be applied if the assembly process includes periodic impact on the assembled parts.

Synthesis and Characterisation of Core-shell Gold Nanoparticles

<p>Technology developed at Victoria University of Wellington by Professor James H. Johnston and Dr Kerstin Lucas allows for the colouring of high quality wool fibres using spherical gold nanoparticles. Gold nanoparticles have interesting colours and optical properties due to surface plasmon resonance effects and, using this technology, a boutique range of colours can be imparted onto wool fibres. The colour of gold nanoparticles is determined by their size and shape, hence the colour range achievable using spherical nanoparticles is limited to those obtained by changing the particle diameter and degree of aggregation of these particles. This limitation can be overcome by using gold nanoparticles of different shapes in conjunction with other materials. This research details the synthesis and characterisation of gold nanoshells on spherical silica cores and their use for the colouring of wool. Silica cores were used in this research as they are reasonably chemically inert and so serve as a stable substrate for the gold shells. Silica spheres are also easily prepared in a manner that allows control over the final particle diameter. Several syntheses of these core-shell particles have been previously devised however they are not suitable for commercial use. Such syntheses involve many time-consuming steps, high temperatures or light-sensitive reagents. Synthetic methods set out in this research involve a novel in-situ seeding of gold nanoparticles for the growth of the shells eliminating the step of growing gold nanoparticles ex-situ commonly involved in other synthetic schemes. The need for light-sensitive reducing agents is eliminated by the use of other reductants such as sodium borohydride and hydroxylamine. All steps of the synthetic schemes are carried out at less than 100 °C. Several methods of synthesising core-shell particles are outlined in this research, which achieved varying degrees of success. Many syntheses investigated successfully produced core-shell particles but also left many silica spheres without the desired gold shell coating. This was not a problem for the proposed application of colouring wool. As silica is easily dispersed in water and does not have the same affinity to bind to wool as gold does, the silica spheres without gold shells simply wash off after colouring. This allowed the core-shell particles synthesised in this research to be successfully used to colour wool fibres and achieve a shade of purple not previously obtained using the earlier methodologies.</p>

Synthesis and Characterisation of Core-shell Gold Nanoparticles

<p>Technology developed at Victoria University of Wellington by Professor James H. Johnston and Dr Kerstin Lucas allows for the colouring of high quality wool fibres using spherical gold nanoparticles. Gold nanoparticles have interesting colours and optical properties due to surface plasmon resonance effects and, using this technology, a boutique range of colours can be imparted onto wool fibres. The colour of gold nanoparticles is determined by their size and shape, hence the colour range achievable using spherical nanoparticles is limited to those obtained by changing the particle diameter and degree of aggregation of these particles. This limitation can be overcome by using gold nanoparticles of different shapes in conjunction with other materials. This research details the synthesis and characterisation of gold nanoshells on spherical silica cores and their use for the colouring of wool. Silica cores were used in this research as they are reasonably chemically inert and so serve as a stable substrate for the gold shells. Silica spheres are also easily prepared in a manner that allows control over the final particle diameter. Several syntheses of these core-shell particles have been previously devised however they are not suitable for commercial use. Such syntheses involve many time-consuming steps, high temperatures or light-sensitive reagents. Synthetic methods set out in this research involve a novel in-situ seeding of gold nanoparticles for the growth of the shells eliminating the step of growing gold nanoparticles ex-situ commonly involved in other synthetic schemes. The need for light-sensitive reducing agents is eliminated by the use of other reductants such as sodium borohydride and hydroxylamine. All steps of the synthetic schemes are carried out at less than 100 °C. Several methods of synthesising core-shell particles are outlined in this research, which achieved varying degrees of success. Many syntheses investigated successfully produced core-shell particles but also left many silica spheres without the desired gold shell coating. This was not a problem for the proposed application of colouring wool. As silica is easily dispersed in water and does not have the same affinity to bind to wool as gold does, the silica spheres without gold shells simply wash off after colouring. This allowed the core-shell particles synthesised in this research to be successfully used to colour wool fibres and achieve a shade of purple not previously obtained using the earlier methodologies.</p>

Bi-funtional resonance effects of plasmon-induced transparency and Fano-like response using an asymmetry metamaterial resonator consisting of three metallic strips at terahertz frequency

Bi-functional metamaterial resonance device operated at terahertz frequency is designed in this paper. It is composed of three metallic strips, in which two parallel metallic strips having the identical dimensions are arranged in the longitudinal direction, and a single metallic strip deviated from the center position is arranged in the horizontal direction. Bi-functional resonance effects of plasmon-induced transparency (PIT) and Fano-like response are simultaneously obtained in this simple metamaterial structure. The formation mechanisms of the two resonance effects are analyzed with the aid of the near-field distributions and the dependence of structure parameters on the whole resonance performance. Results further show that the metallic strip placed horizontally plays an important role in adjusting the resonance response of the metamaterial resonator. More importantly, when the deviation value of the metallic strip in the horizontal direction exceeds a certain amount, for example 10 μm, the metamaterial resonator can realize the effective regulation from bi-functional resonance to single-functional PIT effect. Our proposed structure can be used as valuable platform for ideas to inspire the design of novel electro-optic devices.

Generalized Kerker effect in dielectric antennas for enhanced backscattering modulation

Enhancement of electromagnetic signal modulation is one of the key problems for modern contactless communication systems. Using resonance effects allows to achieve significant interaction between an electromagnetic wave and matter of an antenna, providing opportunity to control scattering. This work demonstrates efficiency of multipole engineering based on Mie theory for dielectric core-shell antennas, particularly we show that generalized Kerker effect is a useful tool for backscattering modulation magnification. Our approach allows to manipulate scattering properties of devices without increasing their size by using all-dieletric concept.