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Determination of the formation of bright molecular fluorphores during the synthesis of pyrene-derived CNDs, through extensive separation and systematic characterization.

Fluorescent carbon nanodots (CDs) have been highlighted as promising semiconducting materials due to their outstanding chemical and optical properties. However, the intrinsic heterogeneity of CDs has impeded a clear understanding of the mechanisms behind their photophysical properties. In this study, as-prepared CDs are fractionated via chromatography to reduce their structural and chemical heterogeneity and analyzed through ensemble and single-particle spectroscopies. Many single particles reveal fluorescence intensity fluctuations between two or more discrete levels with bi-exponential decays. While the intrinsic τ1 components are uniform among single particles, the τ2 components from molecule-like emissions spans a wider range of lifetimes, reflecting the inhomogeneity of the surface states. Furthermore, it is concluded that the relative population and chemical states of surface functional groups in CDs have a significant impact on emissive states, brightness, blinking, stability, and lifetime distribution of photoluminescence.

The excellent contrast ratio, visibility, and advantages in producing thin and light displays let organic light emitting diodes change the paradigm of the display industry. To improve future display technologies, higher electroluminescence efficiency is needed. Herein, the detailed study of the non-radiative decay mechanism employing density functional theory calculations is carried out and a simple, general strategy for the design of the ancillary ligand is formulated. It is shown that steric bulk properly directed towards the phenylisoquinoline ligands can significantly reduce the non-radiative decay rate., Though Ir-based dopants with ancillary ligands are attractive for realizing efficient organic light-emitting diodes, a strategy for designing these materials remains elusive. Here, the authors report a design strategy for heteroleptic triplet OLED emitters featuring functionalized ancillary ligands.

Correction for ‘Identifying molecular fluorophore impurities in the synthesis of low-oxygen-content, carbon nanodots derived from pyrene’ by Nadeesha L. Kothalawala et al., New J. Chem., 2022, DOI: https://doi.org/10.1039/d2nj00430e.

In this paper, we discuss the use of radar sensor to localize an airborne platform using a proposed rotation-invariant template matching algorithm based on data fusion. If a digital elevation model (DEM) under the platform is measured by radar, it can be used to estimate the position of the platform through comparing a pre-recorded DEM of large area through template matching. We implemented four different rotation-invariant template-matching algorithms and compared their performances from the perspective of position estimation accuracy and computational complexity. Based on the investigations, we chose a Fourier transform-based method that utilizes the characteristic of magnitude invariance with the shift of the original data. To improve the position estimation by providing more information, the gradients of DEM were derived. To combine the total error cost from the original DEM and its gradient, we employ an adaptive weighting inspired by the information theory. A higher weight is given to data that have more information. The information is measured as entropy, which is the inverse of the probability that the error cost is the minimum out of all possible error costs in the template-matching process. Through the suggested adaptive weighting, the position estimation accuracy has been increased by 16.04% compared with the uniform weighting. Compared with only using a DEM, the use of gradients of DEM improves the accuracy by 55.37%.

This study proposes a modeling process of equivalent terrains to reduce the computational load and time of a full- wave electromagnetic (EM) simulation. To verify the suitability of the proposed process, an original terrain model with a size of 3 m × 3 m is equivalently quantized based on the minimum range resolution of a radar, and the radar image of the quantized model is compared with that of the original model. The results confirm that the simulation time can be reduced from 407 hours to 162 hours without a significant distortion of the radar images, and an average estimation error of the quantized model (20.4 mm) is similar to that of the original model (20.3 mm).

In this paper, multidirectional light-control reflective (LCR) films are developed in order to create an active reflective structure that will enhance the image brightness and contrast ratio of reflective dye-doped polymer-dispersed liquid crystal (D-PDLC) displays at lower viewing angles. Advantages of LCR films are that their production is low cost and they require a simple photolithographic fabrication method. The optimum design prism-type light-control reflective film succeeded in minimising the surface scattering effect; thus, the contrast ratio is much enhanced. The symmetric and asymmetric LCR films produced multidirectional scattering that enhances the reflectance at lower viewing angles, which has importance in future display applications. In particular, the prism LCR film has been found to be more influential on the reflectance of D-PDLC films due to multidirectional scattering of light by non-symmetric arrays. The improvement in contrast ratio has been confirmed by the enhancement of optical pr...

Dye-doped PDLC has a high probability to be used as reflective optical shutter due to its good reflectance compared to normal PDLC or LC shutter structures. The black state can be significantly enhanced by the minimized surface scattering between polymer and LC surface, which makes a harmful result to the contrast ratio, one of most important factors for optical shutter. To remove this scattering effect, we have developed new combinational structure, consisted of guest dye-doped LC (DLC) and dye-doped PDLC (DPDLC). In the newly fabricated dye-doped PDLC structure, the front location of dye-doped LC layer can remove the light scattering effect of the surface of single dye PDLC structure. The proposed process can also remove the randomly distributed dyes in polymer area of dye PDLC. This technique enhances the reflectance as well as the contrast ratio.

The enhancement of electro-optical properties in reflective-type dye polymer dispersed liquid crystal (PDLC) has been achieved by applying an additional white PDLC layer along with dye PDLC layer. This newly modified structure that consists of white PDLC layer and scattering reflector acts as an active reflector. In this practice, an additional arrangement of a polymer barrier layer is made-up over white PDLC layer, to block the absorption of any solution from dye PDLC. The contrast ratio of this new configuration is almost doubled with low driving voltage and high ON reflectance. Simultaneously, the “off” state has been observed darker than single layer dye PDLC structure. This new configuration can be potentially significant for various display applications such as E-paper, outdoor billboard, and flexible display. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Treatment of AlMe3 with 2 equiv of 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tert-pentylphenol (Lig1H) or 2-tert-butyl-6-(5-chloro-2H-benzo[d][1,2,3] triazol-2-yl)-4-methylphenol (Lig2H) and subsequent addition of ROH afford monomeric and heteroleptic (OR)AlL2 complexes [R = C6H5, L = Lig1, 1; R = p-C6H4Ph, L = Lig1, 2; R = C6H5, L = Lig2, 3; R = p-C6H4Ph, L = Lig2, 4]. The simple reaction between a quantitative amount of water and compound 1 gave the novel dimeric aluminum complex 5 bridged by an oxygen atom. The crystal structures of 1, 3, and 5 determined from X-ray diffraction studies reveal pentacoordination geometry around the Al center with the preference for the slightly distorted trigonal-bipyramidal geometry. Monomeric complexes 1−4 showed emissions of the blue region (475 nm) with broad emission areas (half-width of peak = 150 nm) in the emission spectrum with high quantum yield. Dimeric aluminum complex 5 with enhanced thermal stability has a similar absorption and emission pattern to complexe...

The purpose of this study was to develop an optimal path planning program for autonomous speed sprayer in orchard. A digital map which contained coordinate information and entity information including height, width, radius of main stem, and disease of a trees was developed to build an optimal path. The digital map, dynamic programming and order-picking algorithm were used for planning an optimal path for autonomous speed sprayers. When this algorithm applied to rectangular-shaped orchards to travel whole trees, the developed program planned the same working path and same traveling distance as those of created by conventional method. But for irregular-shaped orchards, developed program planned differently and 5.06% shorter path than conventional method. When applied to create path for multi-selected trees, irregular-shaped orchards showed 13.9% shorter path and also rectangular-shaped orchards showed 9.1% shorter path. The developed program always planned shorter path than the path created by conventional method despite of variation of shape of orchards.

We present a novel affine projection algorithm (APA) which dynamically selects input vectors in order to improve convergence performance. The optimum selection of the input vectors is derived by the largest decrease of the mean-square deviation. The experimental results show that the proposed algorithm has a fast convergence speed and a small steady-state error compared to the conventional APA. In addition, the proposed algorithm retains a low overall computational complexity.

We present a novel affine projection algorithm which reduces complexity by selecting a subset of input regressors at every iteration. The optimal selection of input regressors is derived by comparing the cost functions based on the principle of minimum disturbance. The proposed algorithm shows good convergence performance with various experimental results

For the development of blue-emitting Ir(III) complexes, a set of new ligands, 2-(3-Y-phenyl)-4-methoxypyridine where Y denotes an electron-withdrawing cyanyl (cpmpH) or acetyl group (apmpH), were designed and synthesized. The phosphorescent Ir complexes, IrL2(pic) (L = cpmp; 1, apmp; 2, pic = 2-picolinate) were synthesized via chloro-bridged dimers, [IrL2Cl]2 and characterized by NMR spectra and elemental anaylses. 1 and 2 show bluish-green light with the PL maxima of 476 and 481 nm, respectively and blue-shifted emission compared to green phosphorescent Ir(ppy)2(pic). The solution PL efficiency of 1 and 2 is 0.12 and 0.09, respectively.

In this paper, we propose a novel multi-view generation framework that considers the spatiotemporal consistency of each synthesized multi-view. Rather than independently filling in the holes of individual generated images, the proposed framework gathers hole information from each synthesized multi-view image to a reference viewpoint. The method then constructs a hole map and a SVRL (single view reference layer) at the reference viewpoint before restoring the holes in the SVRL, thereby generating a spatiotemporally consistent view. A hole map is constructed using depth information of the reference viewpoint and the input/output baseline length ratio. Thus, the holes in the SVRL can also represent holes in other multi-view images. To achieve temporally consistent hole filling in the SVRL, the restoration of holes in the current SVRL is performed by propagating the pixel value of the previous SVRL. Further hole filling is performed using a depth- and exemplar-based inpainting method. The experimental results showed that the proposed method generates high-quality spatiotemporally consistent multi-view images in various input/output environments. In addition, the proposed framework decreases the complexity of the hole-filling process by reducing repeated hole filling.

The color optical switching device by polymer network liquid crystal (PNLC) with color filter on a specular reflector shows excellent performance; white reflectance of 22%, color gamut of 32%, and contrast ratio up to 50:1 in reflective mode measurement. The view-angle dependence of the reflectance can be adjusted by changing the PNLC thickness. The color chromaticity shown by the device is close to the limit value of color filters, and its value nearly remains with respect to the operating voltage. These optical properties of the device can be explained from the prediction based on multiple interactions between the light and the droplets of liquid crystal. The high reflectance, vivid color image, and moderate responds time allow the PNLC device to drive good color moving image. It can widely extend the applications of the reflective device.

The optical properties and the theoretical prediction of color optical shutter with dye-doped polymer network liquid crystal (PNLC) were investigated. The view-angle dependence of reflectance according to the bias conditions showed distinctive characteristics, which could be explained from the effects of dye absorption and path length. It was also shown that the thickness dependence of reflectance was strongly influenced by the light-scattering coefficient. Our experimental results matched up well with the theoretical prediction based on the light scattering of liquid crystals in polymer network and the absorption of dichroic dye. This work indicates potential to improve the optical device using dye-doped liquid crystal-polymer composite.

Showing their true colors? Full emission color tuning in the visible region can be achieved with salen-aluminum complexes that are electronically modulated at C5 of the phenoxide ring in the salen moiety. Emission spectra for various substituents R(5) are shown (EWG: electron-withdrawing group, EDG: electron-donating group).A series of salen-aluminum complexes, [{(R(5))(2)-salen(3-tBu)(2)}Al(OC(6)H(4)-p-C(6)H(5))] (salen=N,N'-bis(salicylidene)ethylenediamine; R(5)=H (1), tBu (2), Br (3), Ph (4), OMe (5), NMe(2) (6)) and [{5,5'-(NMe(3))(2)-salen(3-tBu)(2)}Al(OC(6)H(4)-p-C(6)H(5))][OTf](2) (7; OTf=CF(3)SO(3)) that are electronically modulated directly at C5 of the phenoxide ring in the salen moiety has been prepared. The crystal structures of 1, 4, 6, and 7 determined by X-ray diffraction reveal distorted square-pyramidal geometries around the Al atoms. Complexes 1-7 are all air-stable in both the solid and solution states and have high thermal stability (decomp 313-338 degrees C). Differential scanning calorimetric analyses show that they can form amorphous glasses with glass transition temperatures of 95-132 degrees C depending on the C5 substituent. UV/Vis absorption spectra of the complexes exhibit major bands at lambda=338-413 nm assignable to salen-centered pi-pi* transitions with a gradual red shift of the absorption maximum wavelengths as the substituent is varied from an electron-withdrawing (NMe(3)) to an electron-donating group (NMe(2)). The maxima in the emission spectra of 1-7 occur over the entire visible region, ranging from lambda=438 nm for 7 to lambda=599 nm for 6, with high fluorescence quantum efficiencies of up to Phi=0.40 for 4 in solution. DFT calculations suggest that the low-energy electronic transitions in 1-7 are characterized by HOMO(-i)-LUMO(+1) (i=1 for 1-6 or i=4 for 7) transitions localized on the salen moiety, with much involvement of the C5 position in the HOMO(-i). Thus, the electronic alteration at the C5 position of the phenoxide ring, which mainly affects the HOMO(-i) energy levels of salen-Al luminophores, is responsible for the observed emission color-tuning properties over the entire visible region.

A discrete heterodinuclear Al (III)/Ir (III) complex shows bright-orange light emission when used as an active layer in host-dopant assembly organic light-emitting diodes based on a solution process.

The organic light-emitting diodes (OLEDs) employing complex [salen(tBu)4Al(OC6H4-p-C6H5)] (4) as a hole-blocking layer produced stable green EL emission of Ir(ppy)3 irrespective of changing current density and showed higher brightness and device efficiency than the BAlq-based device.

Affine projection algorithm, which updates the weight vector based on several previous input vectors, is an useful adaptive filter to improve the convergence speed of LMS-type filter. However, the computational complexity of adaptation algorithm highly depends on the number of input vectors used for update. In this paper, we propose affine projection algorithm with selective regressors whose purpose is to reduce complexity by selecting a subset of input regressors at every iteration. The optimal selection of input regressors is derived by comparing the cost functions based on the principle of minimum disturbance. The new algorithms show good convergence performance as attested to by various experimental results.

A color-reflective optical shutter structure has been studied using polymer-stabilized liquid crystal (PSLC) devices with a specular reflector. The combined effect of an LC, a polymer, a color dye, and a specular reflector results in a high performance of a reflective-mode optical shutter as well as of a simple structure with a fast response time capable of smooth moving images. The reflectance is up to 40%, one of highest for reflective devices, whose response times are fast enough to provide video speed response (

Various type color PDLC structures have been characterized on a glass and a plastic substrate for reflective mode color display. The standard PDLC and the black diachronic dye mixed PDLC structure with color filter (RGB) show a good black state with high color purity and 256 gray levels, even though both structures have a dark color images. Color dichroic dye (RGB/CMY) mixed PDLC cells promise a good white reflectance. The problem of using color dye system is the enhancement of a poor black state. Using new CMY color based filter with black dye PDLC shutter structure can improve a white state with a proper color vision.