14,929 research outputs found
High-Efficiency Thermally Activated Delayed Fluorescence Emitters with High Horizontal Orientation and Narrow Deep-Blue Emission
No full textHighly efficient 10-(5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10H-dispiro[acridine-9,9 '-anthracene-10 ',9 ''-fluorene] (OBOtSAc) and 10-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10H-dispiro[acridine-9,9 '-anthracene-10 ',9 ''-fluorene] (tBuOBOtSAc) emitters, comprising almost perpendicularly linked rigid 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (OBO) electron acceptors and a rigid and linear tri-spiral acridine electron donor, are reported here. OBOtSAc and tBuOBOtSAc show deep-blue emission (lambda(max) = 452 and 446 nm) with narrow full width at half maximum (FWHM) values of 50 and 48 nm, respectively. Due to the rigid and twisted structures, and the appropriate singlet and triplet energy levels of both emitters, 10 wt% doped films of OBOtSAc and tBuOBOtSAc in a bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO) host show efficient thermally activated delayed fluorescence (TADF) emission and photoluminescence quantum yields (PLQYs) of 97% and 90%, respectively. Moreover, linear-shaped OBOtSAc and tBuOBOtSAc lead to excellent horizontal emitting dipole orientations (88% and 90%, respectively). Consequently, organic light-emitting diode (OLED) devices using OBOtSAc and tBuOBOtSAc exhibit maximum external quantum efficiencies (EQEs) of 31.2% and 28.2%, respectively, and Commission Internationale de l'eclairage (CIE) coordinates of (0.147, 0.092) and (0.149, 0.061), respectively.N
Multiple resonance thermally activated delayed fluorescence enhanced by halogen atoms
No full textWe synthesized halogen-substituted multiple-resonance (MR) thermally activated delayed fluorescence emitters, namely 2,12-dichloro-N,N,5,9-tetrakis(4-chlorophenyl)-5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracen-7-amine (Cl-MR) and 2,12-dibromo-N,N,5,9-tetrakis(4-bromophenyl)-5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracen-7-amine (Br-MR). Cl-MR and Br-MR exhibited a decreased delayed fluorescence lifetime and an enhanced reverse intersystem crossing rate without any changes in Delta E-ST and orbital distribution compared with a non-halogenated MR emitter. Cl-MR exhibited a high photoluminescence quantum yield (PLQY) of 85% and external quantum efficiency (EQE) of 17%; however, Br-MR did not exhibit any enhancement in the PLQY and EQE. The different performances of Cl-MR and Br-MR were rationalized by analysing the rate constants of the excited states and bond dissociation energies of the carbon-halogen bonds.N
Scheurvorming in jong beton: Onderzoek biedt nieuwe inzichten in de spanningsrelaxatie bij jong beton
No full textBeton is tijdens het verharden onderhevig aan thermische en autogene vervormingen. Wanneer deze worden verhinderd, resulteert dit in spanningen en het risico op scheurvorming, mede afhankelijk van relaxatie. Aan de TU Delft is onderzoek gedaan naar het effect van spanningsrelaxatie op scheurvorming in jong beton. In tegenstelling tot de verwachtingen, blijkt dat spanningsrelaxatie in de eerste twee dagen juist resulteert in een verhoogd risico op scheurvorming bij bepaalde constructies met verhinderde vervorming. Ook blijkt dat autogene zwelling daarbij een significante rol speelt, die tot op heden in de norm buiten beschouwing wordt gelaten.Materials and EnvironmentConcrete Structure
미세 유체 소자를 위한 전기화학 임피던스 바이오 센서의 설계와 특성 분석
No full text학위논문(박사) - 한국과학기술원 : 신소재공학과, 2005.2, [ x, 126 p. ]In the recent years, there has been a merger of microelectronics and biological sciences to develop what are called “Micro Total Analysis System ()”. To enhance the portability and disposability of microfabricated analysis systems, much work has been directed increasingly towards the development of on-chip detection for the direct interrogation of the electrical properties and behavior of biological species. In this thesis, electrochemical impedance sensors have demonstrated in terms of the feasibility of label-free deoxyribonucleic acid (DNA) detection and the frequency characteristics and design rule of coplanar impedance sensors. Glass-based microchannel chips were fabricated using micromachining technology, and Pt thin-film microelectrodes, as coplanar impedance sensors, were integrated on them. In chapter 4, DNA detection method based on dielectric properties was described. From capacitance-frequency measurements at various interelectrode distances and ionic concentrations, a significant difference between the deionized (DI) water and the TE buffer (tris-HCl + ethylenediaminetetraacetic acid (EDTA)) was observed. This was discussed from the viewpoint of interfacial phenomena, such as the electrical double layer and Faradaic reactions, the dielectric constant related to the conductivity, and the capacitance inversely proportional to the interelectrode distance. From the nondependence of capacitance on interelectrode distance in the low-frequency region of the TE buffer, we focused on the electrode-electrolyte interface and explained the behavior observed using the double layer model and Fradaic reactions. The addition of ions and molecules increased capacitance due to the diffusive mobile layer and the Faradaic reaction at the electrode-electrolyte interface. The addition of DNA molecules (10ng/㎕) resulted in an increase in capacitance and dielectric loss in the TE buffer at low frequency. It is feasible to use dielectric properties for rapid and dir...한국과학기술원 : 신소재공학과
Dual-functional turn-on fluorescent probe for discriminative sulfite and sulfide detection via organic/aqueous ratio tuning and its application in real samples
No full text© 2022Sulfite and sulfide are substances commonly present in food, biological and industrial processes. While excess amounts of these anions can elicit physiological disorders in humans, there are only limited examples of probes capable of selectively detecting both of them. In this study, we present a sulfite/sulfide dual-functional probe 1 based on a dimethylaminonaphthalene-oxazaborine fluorophore and a dicyanovinyl reaction site. Probe 1 enabled a highly selective detection of sulfite under acetonitrile/tris buffer (85:15, v/v), discriminating sulfite from common interfering species such as sulfide, cyanide, and biothiols. The probe fully responded to sulfite within 4 min, with an 18-fold increase in the fluorescence intensity. Besides, probe 1 was also able to selectively sense sulfide in pure acetonitrile, while displaying a detection limit as low as 96 nM. Mechanistic studies revealed that a large 170 nm Stokes shift of the probe after sulfite/sulfide detection can be ascribed to the nucleophilic addition of sulfite/sulfide to the dicyanovinyl moiety, which broke the conjugation system between the fluorophore scaffold and the dicyanovinyl group, thereby triggering the intramolecular charge transfer effect. Finally, the probe displayed good capability for sensing sulfite and sulfide in real samples with good recoveries, proving its potential in the determination of sulfite and sulfide concentrations for real-life applications.N
Iridium(III) complex-based phosphorescent and electrochemiluminescent dual sensor for selective detection of glutathione
No full textGlutathione (GSH) is the most abundant biological thiol and involved in antioxidant defense systems in human cells. Lack of GSH increases the risk of oxidative stress, resulting in the progression of cancer. Therefore, a selective detection method for GSH is highly required. Herein, we report phosphorescent and electrochemiluminescent dual sensors (1-3) based on iridium complexes for the selective detection of GSH. These sensors have a 1,10-phenanthroline-5,6-dione (pdo) ancillary ligand as a common reaction site for GSH. Reduction of the pdo moiety to 1,10-phenanthroline-5,6-diol (phen(OH)2) upon reaction of sensors with GSH triggered fluorescence turn-on response and electrochemiluminescence turn-off response with high selectivity for GSH. Sensing mechanisms were elucidated by DFT calculations and cyclic voltammetry. Sensor 1 was successfully applied to determination of GSH concentrations in human serum samples by ECL methods.N
A photoluminescent and electrochemiluminescent probe based on an iridium(III) complex with a boronic acid-functionalised ancillary ligand for the selective detection of mercury(II) ions
No full textExposure to mercury(ii) ions (Hg2+) can cause various diseases such as Minamata disease, acrodynia, Alzheimer's disease, and Hunter-Russell syndrome, and even organ damage. Therefore, real-time and accurate monitoring of Hg2+ in environmental samples is crucial. In this study, we report a photoluminescent (PL) and electrochemiluminescent (ECL) probe based on a cyclometalated Ir(iii) complex for the selective detection of Hg2+. The introduction of a reaction site, o-aminomethylphenylboronic acid, on the ancillary ligands allowed a prompt transmetalation reaction to take place between Hg2+ and boronic acid. This reaction resulted in significant decreases of the PL and ECL signals due to the photo-induced electron transfer from the Ir(iii) complex to the Hg2+ ions. The probe was applied to the selective detection of Hg2+, and the signal changes revealed a linear correlation with Hg2+ concentrations in the range of 0-10 mu M (LOD = 0.72 mu M for PL, 8.03 nM for ECL). The designed probe allowed the successful quantification of Hg2+ in tap water samples, which proves its potential for the selective detection of Hg2+ in environmental samples.N
Spiro-type TADF emitters based on acridine donors and anthracenone acceptor
No full textTwo rigid spiro-type TADF emitters (CBZANQ, PXZANQ) were designed and synthesized via a two-step route. CBZANQ and PXZANQ both contain an anthracenone acceptor along with a carbazole-acridine-fused donor and a phenoxazine-acridine-fused donor, respectively, where each donor and acceptor are linked by a spiro bridge to form D-sigma-A structures with an orthogonal arrangement. Both CBZANQ and PXZANQ have the difference between the singlet and triplet energy values (Delta E-ST) of 0.05 eV and 0.03 eV, respectively, which are sufficiently small for efficient triplet harvesting. CBZANQ with a weak electron donor (carbazole) exhibited a weak intramolecular charge transfer (ICT) character, resulting in a low photoluminescence quantum yield (PLQY) of 18%. On the other hand, when combined with a strong electron donor (phenoxazine), PXZANQ exhibited a strong ICT character, resulting in a high PLQY of 71%. Organic light-emitting diode (OLED) devices based on CBZANQ emitter and bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) host exhibited sky-blue electroluminescence (EL) at 492 nm with a low external quantum efficiency (EQE) of 6.7%. Conversely, the OLED devices fabricated using PXZANQ emitter and DPEPO host exhibited green emission at 528 nm, along with a high EQE of 22.1%. Additionally, the efficiency of PXZANQ-based devices remained high at high luminance, indicating relatively small efficiency roll-off (13.9% EQE under 500 cd/m(2)).N
Highly Selective Electrochemiluminescence Chemosensor for Sulfide Enabled by Hierarchical Reactivity
No full textHydrogen sulfide (H2S) is a well-known toxic gas with the odor of rotten eggs. Several reaction-based electrochemiluminescence (ECL) chemosensors for H2S have been developed; however, no homogeneous ECL probe with high selectivity toward H2Sinaqueous media has been reported. Herein, we report an iridium(III) complex-based ECLchemodosimetric probe employing two 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) groups known as a photo-induced electron transfer quencher and a reaction site for the selective detection of H2S; the detection mechanism involves H2S being clearly distinguished frombiothiols based on the different cleavage rates of the two NBD groups and extremely weakECL interferences caused by reaction by-products. The probe was rationally designed toimprove selectivity toward H2S within the ECL analysis platform by enabling the removal of nonspecific background signals observedvia fluorescence analysis. This analytical system exhibited remarkable selectivity toward H2S, a rapid reaction rate, and high sensitivity (LOD= 57 nM) compared to conventional fluorescence methods. Furthermore, the probe could successfully quantify H2S in tap water samples and commercial ammonium sulfide solutions ,which demonstrates the effectiveness of this probe infield monitoring.N
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