A 2D Titanium Carbide MXene Flexible Electrode for High-Efficiency Light-Emitting Diodes

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAlthough several transparent conducting materials such as carbon nanotubes, graphene, and conducting polymers have been intensively explored as flexible electrodes in optoelectronic devices, their insufficient electrical conductivity, low work function, and complicated electrode fabrication processes have limited their practical use. Herein, a 2D titanium carbide (Ti3C2) MXene film with transparent conducting electrode (TCE) properties, including high electrical conductivity (≈11 670 S cm−1) and high work function (≈5.1 eV), which are achieved by combining a simple solution processing with modulation of surface composition, is described. A chemical neutralization strategy of a conducting-polymer hole-injection layer is used to prevent detrimental surface oxidation and resulting degradation of the electrode film. Use of the MXene electrode in an organic light-emitting diode leads to a current efficiency of ≈102.0 cd A−1 and an external quantum efficiency of ≈28.5% ph/el, which agree well with the theoretical maximum values from optical simulations. The results demonstrate the strong potential of MXene as a solution-processable electrode in optoelectronic devices and provide a guideline for use of MXenes as TCEs in low-cost flexible optoelectronic devices.

Microbial communities in aerosol generated from cyanobacterial bloom-affected freshwater bodies: an exploratory study in Nakdong River, South Korea

Toxic blooms of cyanobacteria, which can produce cyanotoxins, are prevalent in freshwater, especially in South Korea. Exposure to cyanotoxins via ingestion, inhalation, and dermal contact may cause severe diseases. Particularly, toxic cyanobacteria and their cyanotoxins can be aerosolized by a bubble-bursting process associated with a wind-driven wave mechanism. A fundamental question remains regarding the aerosolization of toxic cyanobacteria and cyanotoxins emitted from freshwater bodies during bloom seasons. To evaluate the potential health risk of the aerosolization of toxic cyanobacteria and cyanotoxins, the objectives of this study were as follows: 1) to quantify levels of microcystin in the water and air samples, and 2) to monitor microbial communities, including toxic cyanobacteria in the water and air samples. Water samples were collected from five sites in the Nakdong River, South Korea, from August to September 2022. Air samples were collected using an air pump with a mixed cellulose ester membrane filter. Concentrations of total microcystins were measured using enzyme-linked immunosorbent assay. Shotgun metagenomic sequencing was used to investigate microbial communities, including toxic cyanobacteria. Mean concentrations of microcystins were 960 μg/L ranging from 0.73 to 5,337 μg/L in the water samples and 2.48 ng/m3 ranging from 0.1 to 6.8 ng/m3 in the air samples. In addition, in both the water and air samples, predominant bacteria were Microcystis (PCC7914), which has a microcystin-producing gene, and Cyanobium. Particularly, abundance of Microcystis (PCC7914) comprised more than 1.5% of all bacteria in the air samples. This study demonstrates microbial communities with genes related with microcystin synthesis, antibiotic resistance gene, and virulence factors in aerosols generated from cyanobacterial bloom-affected freshwater body. In summary, aerosolization of toxic cyanobacteria and cyanotoxins is a critical concern as an emerging exposure route for potential risk to environmental and human health

Backbone-driven host-dopant miscibility modulates molecular doping in NDI conjugated polymers

Molecular doping is the key to enabling organic electronic devices, however, the design strategies to maximize doping efficiency demands further clarity and comprehension. Previous reports focus on the effect of the side chains, but the role of the backbone is still not well understood. In this study, we synthesize a series of NDI-based copolymers with bithiophene, vinylene, and acetylenic moieties (P1G, P2G, and P3G, respectively), all containing branched triethylene glycol side chains. Using computational and experimental methods, we explore the impact of the conjugated backbone using three key parameters for doping in organic semiconductors: energy levels, microstructure, and miscibility. Our experimental results show that P1G undergoes the most efficient n-type doping owed primarily to its higher dipole moment, and better host–dopant miscibility with N-DMBI. In contrast, P2G and P3G possess more planar backbones than P1G, but the lack of long-range order, and poor host–dopant miscibility limit their doping efficiency. Our data suggest that backbone planarity alone is not enough to maximize the electrical conductivity (σ) of n-type doped organic semiconductors, and that backbone polarity also plays an important role in enhancing σ via host–dopant miscibility. Finally, the thermoelectric properties of doped P1G exhibit a power factor of 0.077 μW m(−1) K(−2), and ultra-low in-plane thermal conductivity of 0.13 W m(−1)K(−1) at 5 mol% of N-DMBI, which is among the lowest thermal conductivity values reported for n-type doped conjugated polymers

Backbone-Driven Host-Dopant Miscibility Modulates Molecular Doping In NDI Conjugated Polymers

Molecular doping is the key to enabling organic electronic devices, however, the design strategies to maximize doping efficiency demands further clarity and comprehension. Previous reports focus on the effect of the side chains, but the role of the backbone is still not well understood. In this study, we synthesize a series of NDI-based copolymers with bithiophene, vinylene, and acetylenic moieties (P1G, P2G, and P3G, respectively), all containing branched triethylene glycol side chains. Using computational and experimental methods, we explore the impact of the conjugated backbone using three key parameters for doping in organic semiconductors: energy levels, microstructure, and miscibility. Our experimental results show that P1G undergoes the most efficient n-type doping owed primarily to its higher dipole moment, and better host–dopant miscibility with N-DMBI. In contrast, P2G and P3G possess more planar backbones than P1G, but the lack of long-range order, and poor host–dopant miscibility limit their doping efficiency. Our data suggest that backbone planarity alone is not enough to maximize the electrical conductivity (σ) of n-type doped organic semiconductors, and that backbone polarity also plays an important role in enhancing σ via host–dopant miscibility. Finally, the thermoelectric properties of doped P1G exhibit a power factor of 0.077 μW m−1 K−2, and ultra-low in-plane thermal conductivity of 0.13 W m−1K−1 at 5 mol% of N-DMBI, which is among the lowest thermal conductivity values reported for n-type doped conjugated polymers

Conducting Polymers as Anode Buffer Materials in Organic and Perovskite Optoelectronics

This review focuses on the importance and the key functions of anode interfacial layers based on conducting polymers in organic and organic-inorganic hybrid perovskite optoelectronics. Insertion of a buffer layer between electrode and semiconducting layers is the most common and effective way to control interfacial properties and eventually improve device characteristics, such as luminous efficiency in light-emitting diodes and power conversion efficiency in solar cells. Conducting polymers are considered as one of the most promising materials for future organic and organic-inorganic hybrid electronics because of advantages such as a simple film-forming process and ease of tailoring electrical and physical properties; as a result, using these polymers is compatible with the production of large-area, low-cost, and solution-processed flexible optoelectronic devices. This review introduces the limitations of anode buffer layers based on conducting polymers and then we will provide recent research trends of material engineering to overcome these problems.

A 0.8-to-2.3GHz Quadrature Error Corrector with Correctable Error Range of 101.6ps Using Minimum Total Delay Tracking and Asynchronous Calibration On-Off Scheme for DRAM Interface

As data transfer rates increase, clock frequencies used for high-speed data paths also increase. Thus, multiphase clocks are typically utilized in DRAMs to relax timing margins because of the reduced timing budget. However, phase errors between multiphase clocks, due to device mismatch, degrade the valid data sampling window. To reduce phase error, several multiphase correction schemes have been proposed [1]-[4]. The active poly-phase filter-based open-loop scheme exhibits a small RMS jitter contribution, but the remaining phase error after the error correction is considerably varied and large in its operating frequency range [1]. A distributed delay-locked loop (DLL) [2] offers the smallest RMS jitter, but the residual phase error is non-negligible as well due to the mismatch of error detection circuits in each calibration loop. The phase error corrector with a relaxation oscillator-based phase detector is also susceptible to the mismatch [3]. The digital DLL-based scheme adopts a shared digital feedback loop to eliminate the effect of mismatch [4]. However, it shows a larger RMS jitter contribution than the distributed DLL due to quantization noise and the increased clock path delay. Since the delay of in-phase clock is always fixed at the mid-point, overall set of codes of digitally-controlled delay lines (DCDLs) may not be at their optimum in terms of jitter. Because jitter and total delay of clock paths are increased more than necessary, it leads to degradation of the data eye. In this paper, an improved quadrature error corrector (QEC), the calibration of which starts from the minimum delay code over all DCDLs, is proposed along with an asynchronous and seamless-calibration on-off scheme for the reduction of power consumption in the operating state after calibration.N

A Stereoselective Access to Cyclic cis-1,2-Amino Alcohols from trans-1,2-Azido Alcohol Precursors

A unique one-pot synthesis of cyclic cis-1,2-amino alcohols from trans-1,2-azido alcohol precursors was developed. The key step is highlighted by the stereoselective reduction of the cyclic alpha-alkoxy imines, which could be prepared from the corresponding azides by ruthenium catalysis under photolytic conditions. Remarkably, this unprecedented reaction pathway offers a stereodivergent access to structurally diverse cyclic 1,2-amino alcohols.X1143Nsciescopu

Gastric Inflation in Prehospital Cardiopulmonary Resuscitation: Aspiration Pneumonia and Resuscitation Outcomes

Background: Gastric inflation (GI) can induce gastric regurgitation and subsequent aspiration pneumonia, which can prolong intensive care unit stay. However, it has not been verified in patients with out-of-hospital cardiac arrest (OHCA). This study aimed to investigate the incidence of GI during prehospital resuscitation and its effect on aspiration pneumonia and resuscitation outcomes in patients with out-of-hospital cardiac arrest. Methods: This was a multicenter, retrospective, observational study. Patients with non-traumatic OHCA aged >19 years who had been admitted to the emergency department were enrolled. Patients who received mouth-to-mouth ventilation during bystander cardiopulmonary resuscitation (CPR) were excluded from the evaluation owing to the possibility of GI following bystander CPR. Patients who experienced cardiac arrest during transportation to the hospital who were treated by the emergency medical service (EMS) personnel, and those with a nasogastric tube at the time of chest or abdominal radiography were also excluded. Radiologists independently reviewed plain chest or abdominal radiographs immediately after resuscitation to identify GI. Chest computed tomography performed within 24 h after return of spontaneous circulation was also reviewed to identify aspiration pneumonia. Results: Of 499 patients included in our analysis, GI occurred in approximately 57% during the prehospital resuscitation process, and its frequency was higher in a bag-valve mask ventilation group (n = 70, 69.3%) than in the chest compression-only cardiopulmonary resuscitation (n = 31, 55.4%), supraglottic airway (n = 180, 53.9%), and endotracheal intubation groups (n = 3, 37.5%) (p = 0.031). GI was inversely associated with initial shockable rhythm (adjusted odds ratio [OR] 0.53; 95% confidence interval [CI]: 0.30–0.94). Aspiration pneumonia was not associated with GI. Survival to hospital discharge and favorable neurologic outcomes were not associated with GI during prehospital resuscitation. Conclusions: GI in patients with OHCA was not associated with the use of different airway management techniques

A 370-fJ/b, 0.0056 mm(2)/DQ, 4.8-Gb/s DQ Receiver for HBM3 with a Baud-Rate Self-Tracking Loop

This paper presents a data (DQ) receiver for HBM3 with a self-tracking loop that tracks a phase skew between DQ and data strobe (DQS) due to a voltage or thermal drift. The self-tracking loop achieves low power and small area by utilizing an analog-assisted baud-rate phase detector. The proposed pulse-to-charge (PC) phase detector (PD) converts the phase skew to a voltage difference and detects the phase skew from the voltage difference, An offset calibration scheme that can compensates for a mismatch of the PD is also proposed. The proposed calibration scheme operates without any additional sensing circuits by taking advantage of the write training of HBM, Fabricated in 65 nm CMOS, the DQ receiver shows a power efficiency of 370 fJ/b at 4,8 Gb/s and occupies 0.0056 mm(2). The experimental results show that the DQ receiver operates without any performance degradation under a 10% supply variation.N

A 2D Titanium Carbide MXene Flexible Electrode for High‐Efficiency Light‐Emitting Diodes

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAlthough several transparent conducting materials such as carbon nanotubes, graphene, and conducting polymers have been intensively explored as flexible electrodes in optoelectronic devices, their insufficient electrical conductivity, low work function, and complicated electrode fabrication processes have limited their practical use. Herein, a 2D titanium carbide (Ti3C2) MXene film with transparent conducting electrode (TCE) properties, including high electrical conductivity (≈11 670 S cm−1) and high work function (≈5.1 eV), which are achieved by combining a simple solution processing with modulation of surface composition, is described. A chemical neutralization strategy of a conducting-polymer hole-injection layer is used to prevent detrimental surface oxidation and resulting degradation of the electrode film. Use of the MXene electrode in an organic light-emitting diode leads to a current efficiency of ≈102.0 cd A−1 and an external quantum efficiency of ≈28.5% ph/el, which agree well with the theoretical maximum values from optical simulations. The results demonstrate the strong potential of MXene as a solution-processable electrode in optoelectronic devices and provide a guideline for use of MXenes as TCEs in low-cost flexible optoelectronic devices.N