Fine control over the physicochemical structures of carbon electrocatalysts is important for improving the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable ...Zn–air batteries. Covalent organic frameworks (COFs) are considered good candidate carbon materials because their structures can be precisely controlled. However, it remains a challenge to impart bifunctional electrocatalytic activities for both the ORR and OER to COFs. Herein, a pyridine‐linked triazine covalent organic framework (PTCOF) with well‐defined active sites and pores is readily prepared under mild conditions, and its electronic structure is modulated by incorporating Co nanoparticles (CoNP‐PTCOF) to induce bifunctional electrocatalytic activities for the ORR and OER. The CoNP‐PTCOF exhibits lower overpotentials for both ORR and OER with outstanding stability. Computational simulations find that the p‐band center of CoNP‐PTCOF down‐shifted by charge transfer, compared to pristine PTCOF, facilitate the adsorption and desorption of oxygen intermediates on the pyridinic carbon active sites during the reactions. The Zn–air battery assembled with bifunctional CoNP‐PTCOF exhibits a small voltage gap of 0.83 V and superior durability for 720 cycles as compared with a battery containing commercial Pt/C and RuO2. This strategy for modulating COF electrocatalytic activities can be extended for designing diverse carbon electrocatalysts.
Pyridine‐linked triazine covalent organic framework (PTCOF) with well‐defined carbon active sites and pores is readily prepared, and its electronic structure is effectively modulated by incorporating Co nanoparticles into the framework (CoNP‐PTCOF) to improve the bifunctional electrocatalytic activity for the oxygen reduction reaction and oxygen evolution reaction in Zn–air batteries. A rechargeable Zn–air battery with bifunctional CoNP‐PTCOF exhibits outstanding performance with superior durability.
Organic solid electrolytes offer an effective route for safe and high‐energy‐density all‐solid‐state Li metal batteries. However, it remains a challenge to devise a new strategy to promote the ...dissociation of strong ion pairs and the transport of ionic components in organic solid electrolytes. Herein, a zwitterionic covalent organic framework (Zwitt‐COF) with well‐defined chemical and pore structures is prepared as a solid electrolyte capable of accelerating the dissociation and transport of Li ions. The Zwitt‐COF solid electrolyte exhibits a high room‐temperature ionic conductivity of 1.65 × 10−4 S cm−1 with a wide electrochemical stability window. Besides, the Zwitt‐COF solid electrolyte displays stable Li plating/stripping behavior via effective inhibition of the formation of Li dendrites and dead Li, leading to superior long‐term cycle performance with retention of 99% discharge capacity and 98% Coulombic efficiency in an all‐solid‐state Li‐metal battery. Theoretical simulations reveal that the incorporation of zwitterionic groups into COF can facilitate the dissociation of strong ion pairs and reconstruct the AA‐stacking configuration by dissociative adsorption of Li+ ions on Zwitt‐COF producing linear hexagonal ion channels in the Zwitt‐COF solid electrolyte. This strategy based on Zwitt‐COF can provide an alternative way to construct various solid‐state Li batteries.
A zwitterionic covalent organic framework (Zwitt‐COF) is developed as a solid electrolyte for all‐solid‐state Li‐metal batteries. The Zwitt‐COF solid electrolyte exhibits a high room‐temperature ionic conductivity with a wide electrochemical window, leading to superior long‐term cycle performance in the battery. Theoretical simulations reveal that Zwitt‐COF promotes the dissociation of Li‐ion pairs and provides ion channels for effective Li+ transport.
Human behavior (e.g., the response to any incoming information) has very complex forms and is based on the response to consecutive external stimuli entering varied sensory receptors. Sensory ...adaptation is an elementary form of the sensory nervous system known to filter out irrelevant information for efficient information transfer from consecutive stimuli. As bioinspired neuromorphic electronic system is developed, the functionality of organs shall be emulated at a higher level than the cell. Because it is important for electronic devices to possess sensory adaptation in spiking neural networks, the authors demonstrate a dynamic, real‐time, photoadaptation process to optical irradiation when repeated light stimuli are presented to the artificial photoreceptor. The filtered electrical signal generated by the light and the adapting signal produces a specific range of postsynaptic states through the neurotransistor, demonstrating changes in the response according to the environment, as normally perceived by the human brain. This successfully demonstrates plausible biological sensory adaptation. Further, the ability of this circuit design to accommodate changes in the intensity of bright or dark light by adjusting the sensitivity of the artificial photoreceptor is demonstrated. Thus, the proposed artificial photoreceptor circuits have the potential to advance neuromorphic device technology by providing sensory adaptation capabilities.
Sol–gel‐derived neurotransistors integrated with perovskite‐based photodetectors are designed to serve as an artificial optoelectronic device array, which experimentally demonstrates the emulation of the dynamic adaptation process of the biological visual nervous system. The fundamental properties of biological adaptation, such as accuracy and desensitization behaviors, are characterized. These results enable post‐synaptic responses to be manipulated to obtain external‐environment‐dependent encoded images.
Precise control over doping of photocatalysts is required to modulate their photocatalytic activity in visible light‐driven reactions. Here, a single precursor‐employing bottom‐up approach is ...developed to produce different heteroatom‐doped graphene quantum dots (GQDs) with unique photocatalytic activities. The solvothermal reaction of a norepinephrine precursor with redox active and condensable moieties effectively produces both nitrogen/sulfur codoped GQDs (NS‐GQDs) and nitrogen‐doped GQDs (N‐GQDs) by simply varying solvents (from dimethyl sulfoxide to water) under microwave irradiation. As‐prepared NS‐GQDs and N‐GQDs show similar lateral sizes (3–4 nm) and heights (1–2 nm), but they include different dopant types and doping constitution and content, which lead to changes in photocatalytic activity in aerobic oxidative coupling reactions of various amines. NS‐GQDs exhibit much higher photocatalytic activity in reactions under visible light than N‐GQDs and oxygen‐doped GQDs (O‐GQDs). The mechanism responsible for the outstanding photocatalytic activity of NS‐GQDs in visible light‐driven oxidative coupling reactions of amines is also fully investigated.
Modulation of the photocatalytic activity of heteroatom‐doped graphene quantum dots (GQDs) is reported. A single precursor, norepinephrine, is used to effectively produce N,S‐co‐doped GQDs and N‐doped GQDs under microwave irradiation. Tailoring dopant types, constitution, and content imparts much higher photocatalytic activity to N,S‐codoped GQDs than N‐doped GQDs and O‐doped GQDs in the visible‐light‐driven oxidative coupling reaction of various amines.
Effective photocatalysts and their surface engineering are essential for the efficient conversion of solar energy into chemical energy in photocatalyzed organic transformations. Herein, we report an ...effective approach for structuring Pd nanoparticles (NPs) on exfoliated 2H-WS2 nanosheets (WS2/PdNPs), resulting in hybrids with extraordinary photocatalytic activity in Suzuki reactions under visible light. Pd NPs of different sizes and densities, which can modulate the photocatalytic activity of the as-prepared WS2/PdNPs, were effectively structured on the basal plane of 2H-WS2 nanosheets via a sonic wave-assisted nucleation method without any reductants at room temperature. As the size of Pd NPs on WS2/PdNPs increased, their photocatalytic activity in Suzuki reactions at room temperature increased substantially. In addition, it was found that protic organic solvents play a crucial role in activating WS2/PdNPs catalysts in photocatalyzed Suzuki reactions, although these solvents are generally considered much less effective than polar aprotic ones in the conventional Suzuki reactions promoted by heterogeneous Pd catalysts. A mechanistic investigation suggested that photogenerated holes are transferred to protic organic solvents, whereas photogenerated electrons are transferred to Pd NPs. This transfer makes the Pd NPs electron-rich and accelerates the rate-determining step, i.e., the oxidative addition of aryl halides under visible light. WS2/PdNPs showed the highest turnover frequency (1244 h–1) for photocatalyzed Suzuki reactions among previously reported photocatalysts.
The preparation of an itaconic acid‐based oligomer and its polymerization with acrylic acid via aqueous solution copolymerization are described herein for application as novel superabsorbent polymers ...(SAPs). The structure of the SAP is characterized using Fourier transform infrared (FT‐IR) spectroscopy. In addition, the absorption properties of the SAPs with various oligomer contents and degrees of monomer neutralization are evaluated by measuring the free absorbency, centrifuge retention capacity (CRC), and absorbency under load (AUL) in 0.9 wt% saline solution. Further, the gel strengths and thermal stabilities are examined via rheological thermo gravimetric analyses. The results demonstrate that the introduction of the IA‐based oligomer into the SAP network is improves the AUL, gel strength, and thermal stability of the SAP. We found the best performance of an SAP using IA‐based oligomer with a CRC of 36.7 and AUL of 22.7 g/g.
In order to effectively detect the contact state between the operator and the collaborative robot, a sensor with excellent external force detection performance is needed. The existing force/torque ...sensor and joint torque sensor, which are the two main external force sensors methods in cooperative robots, have limitations; only the force exerted at the end effector is detected, and it induces a low stiffness in the overall structure which affects the control performance. In the case of sensorless collision detection methods that utilize the current sensor that is used for motor control, the estimation of the performance of external force is sensitive to the sensor noise and dynamic model accuracy only to the extent that it can be used for collision detection. In this paper, we propose a strain gauge-based three-axis sensor of a cylindrical shape, which is often used as a link in a robot. By integrating sensors with robot links, the external force can be precisely measured without compromising the stiffness and is decoupled with joint disturbances, such as motor friction. Sensor calibration is conducted using static load evaluation equipment, and the reliability of collision detection is confirmed by comparing the theoretical/structural analysis results. Through the weight test and sensor characteristic evaluation, the performance and output stability are validated.
Recently, metabolic glycoengineering with bioorthogonal click reactions has focused on improving the tumor targeting efficiency of nanoparticles as delivery vehicles for anticancer drugs or imaging ...agents. It is the key technique for developing tumor‐specific metabolic precursors that can generate unnatural glycans on the tumor‐cell surface. A cathepsin B‐specific cleavable substrate (KGRR) conjugated with triacetylated N‐azidoacetyl‐d‐mannosamine (RR‐S‐Ac3ManNAz) was developed to enable tumor cells to generate unnatural glycans that contain azide groups. The generation of azide groups on the tumor cell surface was exogenously and specifically controlled by the amount of RR‐S‐Ac3ManNAz that was fed to target tumor cells. Moreover, unnatural glycans on the tumor cell surface were conjugated with near infrared fluorescence (NIRF) dye‐labeled molecules by a bioorthogonal click reaction in cell cultures and in tumor‐bearing mice. Therefore, our RR‐S‐Ac3ManNAz is promising for research in tumor‐specific imaging or drug delivery.
A cathepsin B‐specific metabolic precursor can incorporate azide molecules as chemical receptors onto the tumor‐cell surface. The generated azide groups enable tumor‐specific fluorescence imaging through a bioorthogonal click reaction both in vitro and in vivo.
It is very challenging to accurately quantify the amounts of amyloid peptides Aβ40 and Aβ42, which are Alzheimer's disease (AD) biomarkers, in blood owing to their low levels. This has driven the ...development of sensitive and noninvasive sensing methods for the early diagnosis of AD. Here, an approach for the synthesis of Ag nanogap shells (AgNGSs) is reported as surface‐enhanced Raman scattering (SERS) colloidal nanoprobes for the sensitive, selective, and multiplexed detection of Aβ40 and Aβ42 in blood. Raman label chemicals used for SERS signal generation modulate the reaction rate for AgNGSs production through the formation of an Ag‐thiolate lamella structure, enabling the control of nanogaps at one nanometer resolution. The AgNGSs embedded with the Raman label chemicals emit their unique SERS signals with a huge intensity enhancement of up to 107 and long‐term stability. The AgNGS nanoprobes, conjugated with an antibody specific to Aβ40 or Aβ42, are able to detect these AD biomarkers in a multiplexed manner in human serum based on the AgNGS SERS signals. Detection is possible for amounts as low as 0.25 pg mL−1. The AgNGS nanoprobe‐based sandwich assay has a detection dynamic range two orders of magnitude wider than that of a conventional enzyme‐linked immunosorbent assay.
Silver nanogap shells (AgNGSs) with a controllable nanogap size are prepared by modulating the nucleation reaction kinetics using various Raman label chemicals. AgNGSs are successfully employed as colloidal surface‐enhanced Raman scattering (SERS) nanoprobes emitting intense and stable SERS signals for the sensitive, selective, and multiplexed detection of Alzheimer's disease biomarkers, Aβ40 and Aβ42 in human serum.
Tumor targetability and site-specific drug release of therapeutic nanoparticles are key factors for effective cancer therapy. In this study, poly(ethylene glycol) (PEG)-conjugated hyaluronic acid ...nanoparticles (P-HA-NPs) were investigated as carriers for anticancer drugs including doxorubicin and camptothecin (CPT). P-HA-NPs were internalized into cancer cells (SCC7 and MDA-MB-231) via receptor-mediated endocytosis, but were rarely taken up by normal fibroblasts (NIH-3T3). During in vitro drug release tests, P-HA-NPs rapidly released drugs when incubated with cancer cells, extracts of tumor tissues, or the enzyme Hyal-1, which is abundant in the intracellular compartments of cancer cells. CPT-loaded P-HA-NPs (CPT-P-HA-NPs) showed dose-dependent cytotoxicity to cancer cells (MDA-MB-231, SCC7, and HCT 116) and significantly lower cytotoxicity against normal fibroblasts (NIH-3T3) than free CPT. Unexpectedly, high concentrations of CPT-P-HA-NPs demonstrated greater cytotoxicity to cancer cells than free CPT. An in vivo biodistribution study indicated that P-HA-NPs selectively accumulated into tumor sites after systemic administration into tumor-bearing mice, primarily due to prolonged circulation in the blood and binding to a receptor (CD44) that was overexpressed on the cancer cells. In addition, when CPT-P-HA-NPs were systemically administrated into tumor-bearing mice, we saw no significant increases in tumor size for at least 35 days, implying high antitumor activity. Overall, P-HA-NPs showed promising potential as a drug carrier for cancer therapy.
PDF
