Search

Most organic electrode materials (OEMs) for rechargeable batteries employ n‐type redox centers, whose redox potentials are intrinsically limited <3.0 V versus Li+/Li. However, p‐type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes. Herein, we report 5,11‐diethyl‐5,11‐dihydroindolo[3,2‐b]carbazole (DEICZ) as a novel p‐type OEM, exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X‐ray photoelectron spectroscopy. Finally, hybridization with single‐walled carbon nanotubes (SWCNT) improves the cycle stability and rate performance of DEICZ owing to the π–π interactions between the SWCNT and co‐planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4% of its initial specific capacity at 1‐C rate and also exhibits high‐rate capability, even performing well at 100‐C rate. Furthermore, we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode. [ABSTRACT FROM AUTHOR]

Interfacial engineering in organic–inorganic hybrid perovskite solar cells (PSCs) has attracted significant attention, aiming to achieve high‐performing and highly stable devices. Here, newly designed organic small molecules based on quinoxaline and triphenylamine for inverted type wide‐bandgap PSCs are introduced, with the objective of enhancing the interfacial properties between perovskite and NiOx hole transport layer (HTL). The incorporation of an organic interlayer effectively reduces the energy level offset between the HTL and wide‐bandgap perovskite, while passivating defects within the perovskite layer. It leads to improved charge extraction and minimized non‐radiative recombination at the interface. Furthermore, the enhanced interfacial characteristics and hydrophobicity contribute to the improvement of perovskite film quality, resulting in larger grain size and higher crystallinity. As a result, the power conversion efficiency (PCE) of the PSC is enhanced from 18.9% to 20.1% with the incorporation of the IQTPAFlu interlayer, accompanied by an increase in Voc to ≈1.3 V, achieving a significantly low Voc deficit of 0.46 V. And the IQTPAFlu‐based devices demonstrate stable and consistent performance over 500 h, with ≈91% of their initial PCE retained. The highly stable wide‐bandgap PSCs, characterized by high Voc and PCEs, hold great promise as potential candidates for tandem solar cells. [ABSTRACT FROM AUTHOR]

Doping of conjugated polymers (CPs) is a promising strategy to obtain solution‐processable and highly conductive films; however, the improvement in electrical conductivity is limited owing to the relatively poor carrier mobility of CPs. Herein, a CP with excellent molecular doping ability, i.e., poly[2‐([2,2'‐bithiophen]‐5‐yl)‐3,8‐difluoro‐5,10‐bis(5‐octylpentadecyl)‐5,10‐dihydroindolo[3,2‐b]indole] (PIDF‐BT) is wrapped onto the surface of single‐walled carbon nanotubes (SWCNTs). The resulting PIDF‐BT@SWCNT simultaneously achieves excellent solution dispersibility and a high electrical conductivity of over 5000 S cm−1 through AuCl3 doping. The doping mechanism is systematically studied using spectroscopic analysis, and the four‐probe field‐effect transistor based on the doped PIDF‐BT@SWCNT confirms a carrier mobility up to 138 cm2 V−1 s−1. The carrier‐transfer barrier energy is related to the Schottky barrier between the SWCNT and PIDF‐BT, which can be controlled by doping. Finally, when the doped PIDF‐BT@SWCNT is applied to a thermoelectric device, a power factor exceeding 210 μW m−1 K−2 is achieved because of its high electrical conductivity, even if the increased carrier density reduces the Seebeck coefficient. [ABSTRACT FROM AUTHOR]

To investigate the effect of a side chain on the electrical properties of a conjugated polymer (CP), we designed two different CPs containing alkyl and ethylene glycol (EG) derivatives as side chains on the same conjugated backbone with an electron donor-acceptor (D-A) type chain configuration. PTQ-T with an alkyl side chain showed typical p-type semiconducting properties, whereas PTQ-TEG with an EG-based side chain exhibited electrically conductive behavior. Both CPs generated radical species owing to their strong D-A type conjugated structure; however, the spin density was much greater in PTQ-TEG. X-ray photoelectron spectroscopy analysis revealed that the O atoms of the EG-based side chains in PTQ-TEG were intercalated with the conjugated backbone and increased the carrier density. Upon application to a field-effect transistor sensor for PTQ-T and resistive sensor for PTQ-TEG, PTQ-TEG exhibited a better NO2 detection capability with faster signal recovery characteristics than PTQ-T. Compared with the relatively rigid alkyl side chains of PTQ-T, the flexible EG-based side chains in PTQ-TEG have a higher potential to enlarge the free volume as well as improve NO2-affinity, which promotes the diffusion of NO2 in and out of the PTQ-TEG film, and ultimately resulting in better NO2 detection capabilities. [ABSTRACT FROM AUTHOR]

Three conjugated polymers (CPs) containing indolocarbazole‐based similar conjugated frameworks are designed to investigate the NO2 detection capability of field‐effect transistor (FET) sensors. The partly linear aliphatic side chain strengthens the crystallization tendency of the CPs, but the crystallinity is critically degraded when introducing an ethylene oxide (EO)‐modified side chain to the same conjugated framework. Although the highly crystalline morphology of the CP helps to achieve high hole mobility, the NO2 response rate of the CP‐based FET sensor is severely deteriorated because of the suppression of NO2 diffusion into the CP matrix. The polar and flexible EO‐modified side chain is helpful to improve the NO2‐affinity of the CPs and induce favorable pathways for NO2 diffusion, ultimately providing enhanced detectivity with better NO2‐response characteristics. As a result, despite low charge carrier mobility due to pure amorphous nature, the CP with EO‐modified side chains provides an exceptional sensitivity of 180%/ppm upon NO2 (100 ppb) exposure for 50 s, including distinct detectivity toward other environmentally abundant harmful polar gases, such as SO2, NO, and NH3. [ABSTRACT FROM AUTHOR]

Intrinsic characteristics of organic semiconductor‐based hole transport materials (HTMs) such as facile synthesizability, energy level tunability, and charge transport capability have been highlighted as crucial factors determining the performances of perovskite photovoltaic (PV) cells. However, their properties in the excited state have not been actively studied, although PVs are operated under solar illumination. Here, the characteristics of organic HTMs in their excited state such as transition dipole moment can be a decisive factor that can improve built‐in potential of PVs, consequently enhancing their charge extraction property as well as reducing carrier recombination. Moreover, the aggregation property of organic semiconductors, which has been an essential factor for high‐performance organic HTMs to improve their carrier transport property, can induce a synergistic effect with their excited state property for the high‐efficiency perovskite PVs. Additionally, it is also confirmed that their optical bandgaps, manipulated to have their absorption in the UV region, are beneficial to block UV light that degrades the quality of perovskite, consequently improving the stability of perovskite PV in p–i–n configuration. As a proof‐of‐concept, a model system, composed of triarylamine and imidazole‐based organic HTMs, is designed, and it is believed that this strategy paves a way toward high‐performance and stable perovskite PV devices. [ABSTRACT FROM AUTHOR]

Conventional chemical doping processes for conjugated polymers (CPs) often degrade the film morphology or cause unsatisfactory doping efficiency owing to the aggregation formation between charged species or insufficient dopant diffusion. In this work, a new strategic doping method, "hybrid doping," is suggested for maximizing the doping efficiency of CPs without hampering the surface morphology of the CP films. The advantage of hybrid doping is that it combines mixture blending and sequential soaking processes. Based on systemic characterizations including spectroscopic, structural, and electrical analyses, it is revealed that hybrid doping enables whole area doping for the crystalline and amorphous regions of CP films, and thus an unprecedentedly high electrical conductivity of up to 81.5 and 639.1 S cm−1, for poly(3‐hexylthiophene) P3HT and poly (2‐([2,2′‐bithiophen]‐5‐yl)‐3,8‐difluoro‐5,10‐bis(5‐octylpentadecyl)‐5,10‐dihydroindolo [3,2‐b]indole) (PIDF‐BT), respectively, is achieved. Furthermore, the exceptional electrical conductivity compensates a reduced Seebeck coefficient, resulting in excellent power factors up to 26.8 and 76.1 μW m−1 K−2 for thermoelectric devices based on doped‐P3HT and PIDF‐BT films, respectively, which is among the highest levels for semiconducting CPs. Hybrid doping is a strategic approach for the simultaneous optimization of electrical conductivity and thermoelectric properties of various CPs. [ABSTRACT FROM AUTHOR]

A series of conjugated polymers (CPs) sharing the same conjugated framework were designed to investigate their detection capability of near infrared light (1000 nm). Through engineering of the CP side-chains, both the light harvesting efficiency and the degree of dark current, which are crucial parameters for determining the performance of photo-detectors, were intercorrelated with the miscibility of CP with n-type PC71BM and the energy level configuration of the inverted-type device architecture. Based on the morphological analysis of the active layer, 2EO-PDBF, containing ethylene glycol units in the side-chain, was found to form enlarged CP:PC71BM interfaces, resulting in superior photo-responsivity compared to other CPs bearing aliphatic side chains. In addition, it was verified that the relatively shallow lowest energy level (LUMO) of 2EO-PDBF suppressed the generation of dark current by serving as an energetic barrier against electron injection from the Ag electrode. Consequently, due to both the reduced dark current and ameliorated photocurrent in 2EO-PDBF compared to those of other CPs with the same conjugated framework, a superior photo-detectivity exceeding 2 × 1012 Jones was attained at 1000 nm with a rapid response time (350 and 410 μs for the rise and decay times, respectively). The obtained results clearly provide plausible design strategies for CPs to limit the dark current and to improve the light harvesting efficiencies of organic photo-detectors. [ABSTRACT FROM AUTHOR]

Developing electrical organic conductors is challenging because of the difficulties involved in generating free charge carriers through chemical doping. To devise a novel doping platform, the doping capabilities of four designed conjugated polymers (CPs) are quantitatively characterized using an AC Hall‐effect device. The resulting carrier density is related to the degree of electronic coupling between the CP repeating unit and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ), and doped PIDF‐BT provides an outstanding electrical conductivity, exceeding 210 S cm−1, mainly due to the doping‐assisted facile carrier generation and relatively fast carrier mobility. In addition, it is noted that a slight increment in the electron‐withdrawing ability of the repeating unit in each CP diminishes electronic coupling with F4‐TCNQ, and severely deteriorates the doping efficiency including the alteration of operating doping mechanism for the CPs. Furthermore, when PIDF‐BT with high doping capability is applied to the hole transporting layer, with F4‐TCNQ as the interfacial doping layer at the interface with perovskite, the power conversion efficiency of the perovskite solar cell improves significantly, from 17.4% to over 20%, owing to the ameliorated charge‐collection efficiency. X‐ray photoelectron spectroscopy and Kelvin probe analyses verify that the improved solar cell performance originates from the increase in the built‐in potential because of the generation of electric dipole layer. [ABSTRACT FROM AUTHOR]

This paper systematically compares the gas sensing properties of organic field‐effect transistors (OFETs) based on patterned 5,11‐bis(triethylsilylethynyl)anthradithiophene (TES‐ADT) films, by adopting TES‐ADT crystal arrays of various shapes and dimensions. The patterning and crystallization of spin‐cast TES‐ADT layers are achieved by the use of a solvent‐containing engraved polydimethylsiloxane (PDMS) mold. Decreasing width of the TES‐ADT pattern enhances gas sensing performance, as well as field‐effect mobility of OFETs. The decreased grain boundary density at narrower line width contributes to the increase of field‐effect mobility. On the other hand, the increased sensing performance is mainly due to the increased area of crystal edges, which provides a diffusion pathway for gas molecules to arrive at the semiconductor‐dielectric interface. This study provides new perspectives on the diffusion pathway of gas molecules in OFET‐based gas sensor, and will be useful for the design of active channel to boost the gas sensing properties of OFETs. [ABSTRACT FROM AUTHOR]

Some companies in Korea have sold beds which contain a processed product containing monazite powder. Consumers may receive external exposure by radiation emitted by progeny radionuclides in uranium and thorium, and internal exposure through the breathing of radon progeny radionuclides produced in the decay chain. Thus, in this study, age specific dose conversion factors (mSv y−1 Bq−1) by external exposure and dose conversion factors by internal exposure (mSv y−1 per Bq m−3) were derived. Besides, a dose assessment program were developed to calculate dose by taking into account real conditions. And the age specific dose was evaluated using the radioactive concentration measured by the NSSC. As a results, external exposure was assessed to get effective doses in the range of 0.00086 to 0.0015 mSv y−1 by external exposure and a committed effective doses in the range of 1.3 to 12.26 mSv y−1 by internal exposure for all age groups. [ABSTRACT FROM AUTHOR]

Designed carbazole-based novel fluorophores (TPCA0M and TPCA6M) exhibit a sensitive response to toxic and explosive nitroaromatic compounds (NACs) via complex formation, and their detection sensitivity or selectivity can be demonstrated by comparing their emission-quenching rate constant or the adoption of similar-structured aromatic compounds as a negative control. The results of time-resolved fluorescence spectroscopy indicate that the static quenching mechanism is involved in NAC detection. In addition, it has been demonstrated by UV-visible and 1H-NMR spectroscopy studies that the emission quenching of the devised fluorophores originated from complex formation with NACs. The difference in the detection sensitivity of the fluorophores for the corresponding NACs can be connected to both the different steric effects of the fluorophores and the degree of energy off-set between the fluorophores and the NACs. A porous membrane-type detection platform, fabricated with TPCA0M, was found to be effective even at a TNT concentration of 1 ppb within 5 s, which reflects both the instantaneous detection capability and the exceptional sensitivity of the designed fluorometric chemosensors. [ABSTRACT FROM AUTHOR]

As a protective layer for deformable displays, we synthesized ladder-type polysilsesquioxanes (LPSQs) containing cyclic epoxy as a curable unit. The mechanical properties after photo- and thermal-curing of LPSQs with a small amount of added Al2O3 nanoparticles were compared with those of the pure LPSQs. The prepared LPSQ-Al2O3 nanocomposites and the pure LPSQs exhibited comparable optical transparencies and thermal stabilities. In addition, the degree of conversion of the applied epoxy units in LPSQs and the resulting mechanical properties, as monitored by Fourier transform infrared spectroscopy and nanoindentation tests, indicated that the addition of nanoparticles to LPSQs moderately enhanced the epoxy conversion rate and remarkably improved the wear resistance, including hardness, after photo-/thermal-curing processes. The LPSQ-Al2O3 nanocomposites achieved higher wear resistance than epoxy-silica nanocomposites containing similar curable functional groups and reinforcing fillers (silica). The excellent mechanical properties of the LPSQ-Al2O3 nanocomposites could be attributed to three-dimensionally interconnected networks of organic-inorganic hybrid-type chemical structures in the LPSQ as well as additional reinforcement from amine-functionalized Al2O3 nanoparticles covalently interconnected with the LPSQ. We believe that the devised LPSQ-Al2O3 nanocomposites could serve effectively as a wear-resistant platform for deformable display windows. [ABSTRACT FROM AUTHOR]

A colorimetric chemosensor adopting polydiacetylene derivatives was rationally designed to detect malondialdehyde (MDA) as a potential food spoilage indicator. A newly developed diacetylene monomer containing an active methylene group effectively reacted with the aldehyde units of the MDA molecule via Knoevenagel-type condensation and resulted in a C=C bond, judging from the results of FT-IR spectroscopy. When the monomer was incorporated into polydiacetylene liposomes, they exhibited a strong change in color from blue to red in the presence of MDA molecules, even though their sensitivity was partly affected by the feed ratio of the applied diacetylene monomers during liposome preparation. In addition, it was verified that the devised MDA chemosensor selectively responded to the divalent MDA, rather than the monovalent butanal. The detection limit of the optimized MDA chemosensor was about 250 μM in solution, but when a film-type MDA chemosensor was fabricated through the accumulation of the liposomes on top of a nylon membrane and then applied, the detection limit improved dramatically, reaching down to 10 μM at room temperature, even by judging the change in color with the naked eye. To confirm that the change of the resulting Hue angle can reflect the detection sensitivity of the MDA chemosensor under different experimental conditions, CIELAB analysis was conducted with the film-type MDA sensor. The results indicated that the Hue angle changed according to the MDA concentration, and the resulting slope can be quantitatively correlated with the sensitivity of the colorimetric detection system. [ABSTRACT FROM AUTHOR]

Three novel triarylamine derivatives (TPACs: TPAC0M, TPAC2M and TPAC3M), sharing the same conjugation scaffold but possessing different numbers of methoxy units, were designed for high performance hole transport materials (HTMs) of p–i–n planar perovskite solar cells (PSCs). Cyclic voltammetry and absorption results showed that their energy levels would be beneficial to work as HTMs of PSCs, and time-resolved photoluminescence and transient photo-voltage studies proved that TPAC-based PSCs had better charge extraction and more suppressed non-radiative recombination properties than PEDOT:PSS-based PSCs, leading to superior power conversion efficiency (PCE). We confirmed that the methoxy units introduced to the triarylamine derivatives did not cause noticeable changes in their optical properties, such as absorption and bandgap, electrical conductance, measured by conductive atomic force microscopy, and mobility, but the charge extraction and recombination behaviors of TPAC-based PSCs could be improved by increasing the number of methoxy units in the arylamine moiety. X-ray photoelectron spectroscopy revealed that methoxy units could act as a Lewis base passivating the defect sites at the interface between HTM and perovskite, consequently resulting in an increase of their PCE to 17.54% without any dopants. [ABSTRACT FROM AUTHOR]

Biologically active novel piperidin-4-one oxime carbamates were synthesized from 3-ethyl-1-methyl-2,6-diphenylpiperidin-4-one oxime, 1,1′-carbonyldiimidazole ( CDI), and primary or secondary amines in the presence of sodium hydride as base. Commercially available, cheaper, and safer CDI was utilized as carbonyl source, instead of toxic phosgene/triphosgene and carbon monoxide. The devised method is feasible for primary and secondary amines to make their corresponding oxime carbamate derivatives, through oxime-imidazolide intermediate, in high yield. When the antimicrobial activity of obtained oxime carbamate derivatives was investigated in comparison with streptomycin and amphotericin B as standards, the oxime carbamate containing heteroaromatic thiazole ring exhibits outstanding antimicrobial effectiveness, regardless of bacterial or fungal types. [ABSTRACT FROM AUTHOR]

A simple solution-based soft-contact printing process that could easily generate sub-100 nm nanopatterns having negligible thickness of residual layer was developed. In this process, the thickness of residual layer could be significantly decreased by controlling the concentration of nanoink or by utilizing nanoink having high curing point. Furthermore, the additional sonication process, introduced to the soft-printing process, could facilitate further decreasing the thickness of residual layer. Consequently, ZnO nanostructures having negligible residual layer were successfully fabricated, and Ag nanostructures having 63.1% average transmittance were demonstrated. We expect that our printing process can be utilized to fabricate semitransparent conductor for various optoelectronic devices by optimizing the dimensional parameters of nanopatterns. [ABSTRACT FROM AUTHOR]

Summary Objectives An outbreak of joint and cutaneous infections among patients who had been injected at a single clinic in South Korea was investigated. Methods In this retrospective case–control study, 61 cases were diagnosed based on symptoms and signs of septic arthritis or cutaneous infection that developed after injections at the clinic between April and September 2012; 64 controls were investigated by administering questionnaires on risk factors and analyzing the clinic medical records. An environmental investigation was performed, and clinical specimens of the cases were analyzed by pulsed-field gel electrophoresis. Results All cases were injected with triamcinolone. A greater number of triamcinolone injections (adjusted odds ratio 4.3, 95% confidence interval 1.5–12.1 for six or more visits, compared with one or two visits) was associated with the development of an infection. In the clinic, only the triamcinolone injection was prepared by mixing with lidocaine and normal saline, and an alcohol swab was prepared using boiled tap water by members of the clinic staff. Although injected medications and environmental cultures were not found to be responsible, a single strain of Mycobacterium massiliense was isolated from the affected sites of 16 cases. Conclusions Repeated injection of triamcinolone contaminated with NTM from the clinic environment may have caused this post-injection outbreak. [ABSTRACT FROM AUTHOR]

A novel conjugated polymer, TdTB, having an alternating configuration of electron donor and acceptor was synthesized for organic photovoltaic (OPV) application. Intramolecular charge transfer made TdTB exhibit bimodal-shaped absorption in visible region, which secured about 4% power conversion efficiency (PCE) via enhanced absorption efficiency. OPV cells could be further optimized by means of additive-assisted annealing or additional super critical CO 2 liquid treatment after additive annealing, and more developed TdTB aggregation was achieved. Consequently, their performances were dramatically improved about 17% and 33%, compared to the non-annealed PV cell, giving 4.65 and 5.27% PCEs, respectively. [ABSTRACT FROM AUTHOR]