1,721,029 research outputs found
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
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
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
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
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
Efficient blue organic electrochemiluminescence luminophore based on a pyrenyl-phenanthroimidazole conjugate
No full textA pyrenyl-phenanthroimidazole (Py-PI) conjugate emitted strong blue electrochemiluminescence (ECL) emission via the reductive-oxidation co-reactant pathway, with an ECL efficiency 3.3 times higher than that of the 9,10-diphenylanthracene (DPA) reference compound.N
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
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
Fully rubbery synaptic transistors made out of all-organic materials for elastic neurological electronic skin
No full textNeurologic function implemented soft organic electronic skin holds promise for wide range of applications, such as skin prosthetics, neurorobot, bioelectronics, human-robotic interaction (HRI), etc. Here, we report the development of a fully rubbery synaptic transistor which consists of all-organic materials, which shows unique synaptic characteristics existing in biological synapses. These synaptic characteristics retained even under mechanical stretch by 30%. We further developed a neurological electronic skin in a fully rubbery format based on two mechanoreceptors (for synaptic potentiation or depression) of pressure-sensitive rubber and an all-organic synaptic transistor. By converting tactile signals into Morse Code, potentiation and depression of excitatory postsynaptic current (EPSC) signals allow the neurological electronic skin on a human forearm to communicate with a robotic hand. The collective studies on the materials, devices, and their characteristics revealed the fundamental aspects and applicability of the all-organic synaptic transistor and the neurological electronic skin
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