The oxygen reduction reaction (ORR) is one of the most important reactions in life processes and energy conversion systems. To alleviate global warming and the energy crisis, the development of ...high‐performance electrocatalysts for the ORR for application in energy conversion and storage devices such as metal–air batteries and fuel cells is highly desirable. Inspired by the biological oxygen activation/reduction process associated with heme‐ and multicopper‐containing metalloenzymes, iron and copper‐based transition‐metal complexes have been extensively explored as ORR electrocatalysts. Herein, an outline into recent progress on non‐precious‐metal electrocatalysts for the ORR is provided; these electrocatalysts do not require pyrolysis treatment, which is regarded as desirable from the viewpoint of bioinspired molecular catalyst design, focusing on iron/cobalt macrocycles (porphyrins, phthalocyanines, and corroles) and copper complexes in which the ORR activity is tuned by ligand variation/substitution, the method of catalyst immobilization, and the underlying supporting materials. Current challenges and exciting imminent developments in bioinspired ORR electrocatalysts are summarized and proposed.
An outline of recent progress on non‐precious‐metal electrocatalysts for the oxygen reduction reaction (ORR) is presented from the viewpoint of bioinspired molecular catalyst design, with a focus on iron/cobalt macrocycles and copper complexes in which the ORR activity is tuned by ligand modification, the method of catalyst immobilization, and the underlying supporting materials (see scheme).
Two organo‐soluble polyimide (PI) resins were prepared from a tricyclic fluoro‐containing dianhydride 9,9‐bis(trifluoromethyl)xanthene‐2,3,6,7‐tetracarboxylic dianhydride (6FCDA) and aromatic diamine ...of 2,2‐bis4‐(4‐aminophenoxy)phenylhexafluoropropane (BDAF) for PI‐IIa and 1,3‐bis(3‐aminophenoxy)benzene (133APB) for PI‐IIb, respectively. For comparison, two analogous PIs were prepared from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and the same diamines to afford PI‐Ia (6FDA‐BDAF) and PI‐Ib (6FDA‐133APB), respectively. Incorporation of the rigid and planar xanthene units in the 6FCDA‐PIs obviously decreased the solubility of the resins in organic solvents. Flexible and tough PI films were fabricated from the PI solutions in N,N‐dimethylacetamide (DMAc). The PI films derived from the rigid and planar 6FCDA dianhydride exhibited obviously enhance thermal stability, and high‐temperature dimensional stability. For example, PI‐IIa (6FCDA‐BDAF) showed the glass transition temperature (Tg) and coefficient of linear thermal expansion (CTE) values of 311.5°C and 50.5 × 10−6/K, respectively, which were all superior to those of the PI‐Ia counterpart (Tg = 264.6°C; CTE = 55.4 × 10−6/K). In addition, the 6FCDA‐PI films maintained the intrinsically excellent optical transparency of the fluoro‐containing PI films and showed the comparable optical properties to those of the 6FDA‐PI films. As for the properties highly related to the space applications, all the PI films exhibited low solar absorptivity (α) values of 0.18–0.20 and the good thermal emissivity (ε) values in the range of 0.68–0.70. PI‐Ia (6FDA‐BDAF) and PI‐IIa (6FCDA‐BDAF) films showed the similar atomic oxygen erosion behaviors with the standard Kapton® type of PI film derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA).
Fluoro‐containing polyimide film with improved thermal stability and low solar absorptivity
Nitric oxide (NO) is an endogenously produced biological signaling compound, involved not only in various physiological processes but also in cancer biology. The potential therapeutic applications of ...NO in regulation of vascular tone, anticancer, antibacterial, anti‐inflammatory, and wound healing processes has resulted in an explosion of research interest in NO donor compounds and in related materials capable of delivering NO to desired sites. Transition‐metal nitrosyls such as those of ruthenium (Ru‐NOs) are photolabile NO donors from which NO release can be manipulated on demand by application of light. This enables control of spatiotemporal delivery and of optimal NO dosage at a desired site and time. In this microreview we highlight advances of the past few years in rational ligand design, the sensitization of metal nitrosyls (especially Ru‐NOs) by use of light from ultraviolet (UV) to near‐infrared (NIR) wavelengths for efficient NO release, and integration of metal nitrosyls with various nanoplatforms for photocontrolled targeted NO delivery.
This microreview describes recent major advances in the integration of metal nitrosyls with various nanoplatforms for photocontrolled nitric oxide delivery.
Recent research and development of colorless and optically transparent polyimide (CPI) films have been reviewed. CPI films possess both of the merits of conventional aromatic PI films and common ...polymer optical film; thus have been widely investigated as components for microelectronic and optoelectronic fabrications. The current review coveres the latest research and development for CPI films, including synthesis chemistry, manufacturing process, and engineering applications. Especially, this review focuses on the applications of CPI films as flexible substrates for optoelectrical devices, such as flexible active matrix organic light emitting display devices (AMOLEDs), flexible printing circuit boards (FPCBs), and flexible solar cells.
The oxygen reduction reaction (ORR) is one of the most important reactions in both life processes and energy conversion systems. The replacement of noble‐metal Pt‐based ORR electrocatalysts by ...nonprecious‐metal catalysts is crucial for the large‐scale commercialization of automotive fuel cells. Inspired by the mechanisms of dioxygen activation by metalloenzymes, herein we report a structurally well‐defined, bio‐inspired ORR catalyst that consists of a biomimetic model compound—an axial imidazole‐coordinated porphyrin—covalently attached to multiwalled carbon nanotubes. Without pyrolysis, this bio‐inspired electrocatalyst demonstrates superior ORR activity and stability compared to those of the state‐of‐the‐art Pt/C catalyst in both acidic and alkaline solutions, thus making it a promising alternative as an ORR electrocatalyst for application in fuel‐cell technology.
Bio‐inspired catalyst defeats Pt: A biomimetic electrocatalyst for the oxygen reduction reaction (ORR) has been covalently grafted onto multiwalled carbon nanotubes. Without pyrolysis, this bio‐inspired catalyst, in which an axial imidazole‐coordinated porphyrin mimics the active site of O2‐activating heme‐containing enzymes, shows superior ORR activity and stability compared to the state‐of‐the‐art Pt/C catalyst in both acidic and alkaline solutions.
A novel cancer cell lysosome-targetable multifunctional NO-delivery nanoplatform (Lyso-Ru-NO@FA@C-TiO2) (1) was developed. It selectively targets folate-receptor overexpressed cancer cells and ...specifically locates within the lysosome organelle to which NO and reactive oxygen species are simultaneously released upon 808 nm NIR light irradiation. The dual-targeted nanoplatform (1) demonstrated the highest anticancer efficacy compared with nontargeted counterparts under NIR light sensitization.
The oxygen reduction reaction (ORR) is essential in many life processes and energy conversion systems. It is desirable to design transition metal molecular catalysts inspired by enzymatic oxygen ...activation/reduction processes as an alternative to noble‐metal‐Pt‐based ORR electrocatalysts, especially in view point of fuel cell commercialization. We have fabricated bio‐inspired molecular catalysts electrografted onto multiwalled carbon nanotubes (MWCNTs) in which 5,10,15,20‐tetra(pentafluorophenyl) iron porphyrin (iron porphyrin FeF20TPP) is coordinated with covalently electrografted axial ligands varying from thiophene to imidazole on the MWCNTs’ surface. The catalysts’ electrocatalytic activity varied with the axial coordination environment (i. e., S‐thiophene, N‐imidazole, and O‐carboxylate); the imidazole‐coordinated catalyst MWCNTs‐Im‐FeF20TPP exhibited the highest ORR activity among the prepared catalysts. When MWCNT‐Im‐FeF20TPP was loaded onto the cathode of a zinc−air battery, an open‐cell voltage (OCV) of 1.35 V and a maximum power density (Pmax) of 110 mW cm−2 were achieved; this was higher than those of MWCNTs‐Thi‐FeF20TPP (OCV=1.30 V, Pmax=100 mW cm−2) and MWCNTs‐Ox‐FeF20TPP (OCV=1.28 V, Pmax=86 mW cm−2) and comparable with a commercial Pt/C catalyst (OCV=1.45 V, Pmax=120 mW cm−2) under similar experimental conditions. This study provides a time‐saving method to prepare covalently immobilized molecular electrocatalysts on carbon‐based materials with structure–performance correlation that is also applicable to the design of other electrografted catalysts for energy conversion.
A time‐saving electrografting method (within a couple of minutes) for the covalent functionalization of carbon nanotube surfaces with an imidazole or thiophene ligand that is axially coordinated with iron porphyrin as electrocatalyst for the oxygen reduction reaction (ORR) has been demonstrated. The N‐imidazole‐coordinated catalyst, MWCNT‐Im‐FeF20TPP, exhibited the highest ORR activity followed by the S‐thiophene and O‐carboxylate axially coordinated catalysts.
In this paper, we consider the problem of asynchronous estimation in the presence of packet losses for the randomly sampling nonlinear system. Packet losses occur at the control input and at the ...measurement side. Firstly, the synchronization of the asynchronous sampling system is realized by weighting the state of the adjacent state update points. Secondly, the projection theorem is used to estimate the system state at the sampling time. Due to modeling errors and unmodeled dynamics, obtaining an accurate dynamic model is challenging. Therefore, observation inference based on interpolation techniques is proposed to solve the asynchronous estimation problem. Furthermore, the algorithm is extended to multi-sensor systems to obtain a distributed fusion estimator. Finally, simulation experiments are conducted to validate the effectiveness of the algorithm.
Two colorless and transparent polyimide (CPI) films with enhanced high‐temperature dimensional stability and solution‐processability were prepared from the methyl‐substituted benzanilide containing ...organo‐soluble polyimide (PI) resins. For this target, a new aromatic diamine, 2,3′‐dimethyl‐4,4′‐diaminobenzanilide (MMDABA) was synthesized. The methyl substituents were expected to endow the derived PI resins good solubility and rigid‐rod benzanilide units can efficiently reduce the coefficients of thermal expansion (CTE) of the derived CPI films. CPI‐a and CPI‐b were prepared by the one‐step thermal polycondensation from MMDABA with hydrogenated pyromellitic dianhydride for CPI‐a and hydrogenated 3,3′,4,4′‐biphenyltetracarboxylic dianhydride for CPI‐b, respectively. The derived PI resins were soluble in polar aprotic solvents. Colorless and transparent CPI‐a and CPI‐b films were prepared from the PI solutions and the subsequent 280°C curing. The CPI films showed good transparency in visible light and transmittances higher than 80% at 450 nm and yellowness index (b*) below 2.0. More importantly, the derived CPI‐a film showed the glass transition temperature (Tg) of 417.5°C and the CTE value of 46.9 × 10−6/K in the range of 50–250°C. Apparently, incorporation of alkyl‐substituted benzanilide units achieved good balance among solution‐processability, high‐temperature dimensional stability, and optical properties.
A hollow mesoporous manganese dioxide-based (H-MnO2) multifunctional nanoplatform, H-MnO2 @AFIPB@PDA@Ru-NO@FA (MAPRF NPs), was prepared for synergistic cancer treatment, in which a histone ...deacetylase inhibitor AFIPB was loaded in its hollow cavity and a ruthenium nitrosyl donor (Ru-NO) and a folic acid (FA) targeting group were covalently decorated on its covered polydopamine (PDA) layer. The MAPRF NPs showed tumor microenvironment (TME)-responsive properties of depletion of glutathione (GSH) to disrupt the antioxidant defense system and on-demand drug delivery. And the released Mn2+ further catalyzed the decomposition of endogenous H2O2 to produce highly toxic hydroxyl radicals (·OH) for enhanced chemodynamic therapy (CDT). Furthermore, upon 808 nm light irradiation MAPRF NPs exhibited controlled nitric oxide (NO) delivery and simultaneously produced significant photothermal effect. Consequently, MAPRF NPs showed high mortality toward cancer cells in the presence of 808 nm light irradiation. This work provides a paradigm of multimodal synergistic therapy that combines NO-based gas therapy with TME modulation for efficient antitumor therapy.
A novel mesoporous MnO2-based multifunctional nanoplatform exhibited near-infrared light-controlled nitric oxide delivery, tumor microenvironment (TME)-responsive release of a histone deacetylase inhibitor and TME modulation for efficient multimodal synergistic antitumor therapy. Display omitted
•A hollow mesoporous MnO2-based multifunctional NO-releasing nanoplatform was prepared.•Tumor microenvironment-responsive of GSH depletion and hydroxyl radical production.•Controlled NO delivery and photothermal effect was achieved upon 808 nm light irradiation.•It showed high mortality toward cancer cells under 808 nm light irradiation.•Synergistic multimodal therapies were attributed to the enhanced antitumor efficiency.
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