Bioinspired molecular catalysts with a unique tricopper architecture for highly efficient oxygen reduction reaction.

In situ growth of intertwined trinuclear copper complexes (nCu3) on a cellulose-derived carbon support (CMC) produced a high-performance electrocatalyst (CMC-nCu3) for the oxygen reduction reaction (ORR), which demonstrated superior performance in zinc-air batteries compared to a commercial Pt/C catalyst. This work highlights the importance of copper-based molecular catalysts with rich and intertwined tricopper structures for boosting both ORR activity and stability.

Novel flexible fixed-time stability theorem and its application to sliding mode control nonlinear systems.

For the fixed-time nonlinear system control problem, a new fixed-time stability (FxTS) theorem and an integral sliding mode surface are proposed to balance the control speed and energy consumption. We discuss the existing fixed time inequalities and set up less conservative inequalities to study the FxTS theorem. The new inequality differs from other existing inequalities in that the parameter settings are more flexible. Under different parameter settings, the exact upper bound on settling time in four cases is discussed. Based on the stability theorem, a new integral sliding mode surface and sliding mode controller are proposed. The new control algorithm is successfully applied to the fixed-time control of chaotic four-dimensional Lorenz systems and permanent magnet synchronous motor systems. By comparing the numerical simulation results of this paper's method and traditional fixed-time sliding mode control (SMC), the flexibility and superiority of the theory proposed in this paper are demonstrated. Under the same parameter settings, compared to the traditional FxTS SMC, it reduces the convergence time by 18%, and the estimated upper bound of the fixed time reduction in waiting time is 41%. In addition, changing the variable parameters can improve the convergence velocity.

Creating Asymmetric Fe-N3C-N Sites in Single-Atom Catalysts Boosts Catalytic Performance for Oxygen Reduction Reaction.

Fine tuning of the metal site coordination environment of a single-atom catalyst (SAC) to boost its catalytic activity for oxygen reduction reaction (ORR) is of significance but challenging. Herein, we report a new SAC bearing Fe-N3C-N sites with asymmetric in-plane coordinated Fe-N3C and axial coordinated N atom for ORR, which was obtained by pyrolysis of an iron isoporphyrin on polyvinylimidazole (PVI) coated carbon black. The C@PVI-(NCTPP)Fe-800 catalyst exhibited significantly improved ORR activity (E1/2 = 0.89 V vs RHE) than the counterpart SAC with Fe-N4-N sites in 0.1 M KOH. Significantly, the Zn-air batteries equipped with the C@PVI-(NCTPP)Fe-800 catalyst demonstrated an open-circuit voltage (OCV) of 1.45 V and a peak power density (Pmax) of 130 mW/cm2, outperforming the commercial Pt/C catalyst (OCV = 1.42 V; Pmax = 119 mW/cm2). The density functional theory (DFT) calculations revealed that the d-band center of the asymmetric Fe-N3C-N structure shifted upward, which enhances its electron-donating ability, favors O2 adsorption, and supports O-O bond activation, thus leading to significantly promoted catalytic activity. This research presents an intriguing strategy for the designing of the active site architecture in metal SACs with a structure-function controlled approach, significantly enhancing their catalytic efficiency for the ORR and offering promising prospects in energy-conversion technologies.

Design and preliminary verification of a novel powered ankle-foot prosthesis: From the perspective of lower-limb biomechanics compared with ESAR foot.

A novel powered ankle-foot prosthesis is designed. The effect of wearing the novel prosthesis and an energy-storage-and-return (ESAR) foot on lower-limb biomechanics is investigated to preliminarily evaluate the design. With necessary auxiliary materials, a non-amputated subject (a rookie at using prostheses) is recruited to walk on level ground with an ESAR and the novel powered prostheses separately. The results of the stride characteristics, the ground reaction force (GRF) components, kinematics, and kinetics in the sagittal plane are compared. Wearing the powered prosthesis has less prolongation of the gait cycle on the unaffected side than wearing the ESAR foot. Wearing ESAR or proposed powered prostheses influences the GRF, kinematics, and kinetics on the affected and unaffected sides to some extent. Thereinto, the knee moment on the affected side is influenced most. Regarding normal walking as the reference, among the total of 15 indexes, the influences of wearing the proposed powered prosthesis on six indexes on the affected side (ankle's/knee's/hip's angles, hip's moment, and Z- and X-axis GRF components) and five indexes on the unaffected side (ankle's/knee's/hip's angles and ankle's/hip's moments) are slighter than those of wearing the ESAR foot. The influences of wearing the powered prosthesis on two indexes on the unaffected side (knee's moment and X-axis GRF component) are similar to those of wearing the ESAR foot. The greatest improvement of wearing the powered prosthesis is to provide further plantarflexion after reaching the origin of the ankle joint before toe-off, which means that the designed powered device can provide further propulsive power for the lifting of the human body's centre of gravity during walking on level ground. The results demonstrate that wearing the novel powered ankle-foot prosthesis benefits the rookie in recovering the normal gait more than wearing the ESAR foot.

Enhancing oxygen reduction activity of dinuclear copper complexes loaded on an N-doped carbon support via a low-temperature pyrolysis strategy.

Bioinspired by the active sites of multicopper oxidases (MCOs), bi/multinuclear copper complexes have attracted great attention in promoting catalytic activity for the oxygen reduction reaction (ORR). Herein, we report the preparation of a Cu-N-C electrocatalyst Cu-BPOZ@CNB-400 for efficient ORR, which was obtained by low temperature pyrolysis of a dinuclear 2,5-bis(2-pyridyl)-1,3,4-oxadiazole (BPOZ) copper complex loaded on a N-doped carbon support at 400 °C. Cu-BPOZ@CNB-400 exhibited a half-wave potential (E1/2) of 0.86 V vs. RHE for the ORR in 0.1 M KOH solution, which was significantly higher than that of the Cu-BPOZ@CNB-800 (E1/2 = 0.83 V) catalyst treated under high temperature (at 800 °C) and the control catalyst Cu-Phen@CNB-400 (E1/2 = 0.82 V) derived from low-temperature-treatment (at 400 °C) of a mononuclear phenanthroline-coordinated-Cu complex loaded on a N-doped carbon support. When Cu-BPOZ@CNB-400 was applied as the cathode catalyst in zinc-air batteries a maximum power density (Pmax) of 127 mW cm-2 could be achieved, demonstrating comparable catalyst performance to the commercial 20 wt% Pt/C (Pmax = 122 mW cm-2) and the control Cu-Phen@CNB-400 catalyst (Pmax = 105 mW cm-2) under similar experimental conditions. Low-temperature pyrolysis of dinuclear copper complexes on a carbon support improved the charge transfer efficiency, inhibited metal aggregation, and could produce highly dispersed Cu-N-C catalysts with dinuclear copper sites for promoting the 4e--reduction selectivity of the ORR. It thus provides a cost-effective approach for the controllable fabrication of efficient ORR catalysts to be applied for energy conversion devices.

A Recursive Non-Uniform Sampling Estimator for Asynchronous Nonlinear Systems.

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.

Coordination polymer derived Fe-N-C electrocatalysts with high performance for the oxygen reduction reaction in Zn-air batteries.

Developing high performance noble-metal-free electrocatalysts as an alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) in energy conversion devices is highly desirable. We report herein the preparation of a coordination-polymer (CP)-derived Fe/CP/C composite as an electrocatalyst for the ORR with excellent activity and stability both in solution and in Zn-air batteries. The Fe/CP/C catalyst was obtained from the pyrolysis of an iron porphyrin Fe(TPP)Cl (5,10,15,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride) grafted Zn-coordination polymer with dangling functional groups 4,4'-oxybisbenzoic acid and 4,4'-bipyridine ligands. The Fe/CP/C catalyst showed much higher ORR activity with a half-wave potential (E1/2) of 0.90 V (vs. RHE) than the Fe/C catalyst (E1/2 = 0.85 V) derived from the carbon-black-supported Fe porphyrins in 0.1 M KOH solution. When Fe/CP/C was used as the cathode electrocatalyst in Zn-air batteries (ZABs), the ZABs achieved a significantly higher open circuit voltage (OCV = 1.43 V) and maximum power density (Pmax = 142.8 mW cm-2) compared with Fe/C (OCV = 1.38 V, Pmax = 104.5 mW cm-2) and commercial 20 wt% Pt/C (OCV = 1.41 V, Pmax = 117.6 mW cm-2). Using dangling functional groups in CP to increase the loading efficiency of iron porphyrins offered a facile method to prepare high-performance noble-metal-free electrocatalysts for the ORR, which may provide promising applications to energy conversion devices.

Event-Triggered State Filter Estimation for Nonlinear Systems with Packet Dropout and Correlated Noise.

This paper begins by exploring the challenge of event-triggered state estimations in nonlinear systems, grappling with packet dropout and correlated noise. A communication mechanism is introduced that determines whether to transmit measurement values based on whether event-triggered conditions are violated, thereby minimizing redundant communication data. In designing the filter, noise decorrelation is initially conducted, followed by the integration of the event-triggered mechanism and the unreliable network transmission system for state estimator development. Subsequently, by combining the three-degree spherical-radial cubature rule, the numerical implementation steps of the proposed state estimation framework are outlined. The performance estimation analysis highlights that by adjusting the event-triggered threshold appropriately, the estimation performance and transmission rate can be effectively balanced. It is established that when there is a lower bound on the packet dropout rate, the covariance matrix of the state estimation error remains bounded, and the stochastic stability of the state estimation error is also confirmed. Ultimately, the algorithm and conclusions that are proposed in this paper are validated through a simulation example of a target tracking system.

Preparation and Properties of Atomic-Oxygen Resistant Polyimide Films Based on Multi-Ring Fluoro-Containing Dianhydride and Phosphorus-Containing Diamine.

Colorless and transparent polyimide (CPI) films with good atomic oxygen (AO) resistance and high thermal endurance are highly required in low earth orbit (LEO) space exploration. Conventional CPI films based on fluoro-containing 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) have been widely used in space applications. However, the AO erosion yields and glass transition temperatures (Tg) of the 6FDA-based CPI films have to be modified in order to meet the severe serving environments. In the current work, novel CPI films based on a multi-ring fluoro-containing 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylicdianhydride (6FCDA) monomer were developed. In order to enhance the AO resistance of the derived CPI film, a phosphorus-containing aromatic diamine, 2,5-bis[(4-aminophenoxy)phenyl]diphenylphosphine oxide (BADPO) was used to polymerize with the dianhydride to create the organo-soluble resin. Then, two phosphorus-containing CPI films (PPI), including PPI-1 (6FDA-BADPO) and PPI-2 (6FCDA-BADPO) were prepared by thermally curing of the PPI solutions at elevated temperatures. The PPI films maintained good optical transparency with transmittance values over 80% at a wavelength of 450 nm. PPI-2 exhibited a Tg value of 311.0 °C by differential scanning calorimetry (DSC) measurement, which was 46.7 °C higher than that of the PPI-1 counterpart (Tg = 264.3 °C). In addition, the PPI-2 film showed a coefficient of linear thermal expansion (CTE) value of 41.7 × 10-6/K in the range of 50~250 °C, which was apparently lower than that of the PPI-1 sample (CTE = 49.2 × 10-6/K). Lastly, both of the two PPI films exhibited good AO resistance with the erosion yields (Ey) of 6.99 × 10-25 cm3/atom for PPI-1 and 7.23 × 10-25 cm3/atom for PPI-2 at an exposure flux of 5.0 × 1020 atoms/cm2. The Ey values of the current PPI films were obviously lower than that of the standard polyimide (PI) film based on pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) (Ey = 3.0 × 10-24 cm3/atom).

Orally-Delivered, Cytokine-Engineered Extracellular Vesicles for Targeted Treatment of Inflammatory Bowel Disease.

The use of orally-administered therapeutic proteins for treatment of inflammatory bowel disease (IBD) has been limited due to the harsh gastrointestinal environment and low bioavailability that affects delivery to diseased sites. Here, a nested delivery system, termed Gal-IL10-EVs (C/A) that protects interleukin 10 (IL-10) from degradation in the stomach and enables targeted delivery of IL-10 to inflammatory macrophages infiltrating the colonic lamina propria, is reported. Extracellular vesicles (EVs) carrying IL-10 are designed to be secreted from genetically engineered mammalian cells by a plasmid system, and EVs are subsequently modified with galactose, endowing the targeted IL-10 delivery to inflammatory macrophages. Chitosan/alginate (C/A) hydrogel coating on Gal-IL10-EVs enables protection from harsh conditions in the gastrointestinal tract and favorable delivery to the colonic lumen, where the C/A hydrogel coating is removed at the diseased sites. Gal-IL10-EVs control the production of reactive oxygen species (ROS) and inhibit the expression of proinflammatory cytokines. In a murine model of colitis, Gal-IL10-EVs (C/A) alleviate IBD symptoms including inflammatory responses and disrupt colonic barriers. Taken together, Gal-IL10-EVs (C/A) features biocompatibility, pH-responsive drug release, and macrophage-targeting as a therapeutic platform for oral delivery of bioactive proteins for treating intestinal diseases.

Synthesis and Characterization of Organo-Soluble Polyimides Based on Polycondensation Chemistry of Fluorene-Containing Dianhydride and Amide-Bridged Diamines with Good Optical Transparency and Glass Transition Temperatures over 400 °C.

Polymeric optical films with light colors, good optical transparency and high thermal resistance have gained increasing attention in advanced optoelectronic areas in recent years. However, it is somewhat inter-conflicting for achieving the good optical properties to the conventional thermal resistant polymers, such as the standard aromatic polyimide (PI) films, which are well known for the excellent combined properties and also the deep colors. In this work, a series of wholly aromatic PI films were prepared via the polycondensation chemistry of one fluorene-containing dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (FDAn) and several aromatic diamines with amide linkages in the main chain, including 9,9-bis [4-(4-aminobenzamide)phenyl]fluorene (FDAADA), 2,2'-bis(trifluoromethyl)-4,4'-bis[4-(4-aminobenzamide)] biphenyl (ABTFMB), and 2,2'-bis(trifluoromethyl)-4,4'-bis[4-(4-amino-3-methyl)benzamide] biphenyl (MABTFMB). The derived FLPI-1 (FDAn-FDAADA), FLPI-2 (FDAn-ABTFMB) and FLPI-3 (FDAn-MABTFMB) resins showed good solubility in the polar aprotic solvents, such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO). The solution-processing FDAn-PI films exhibited good optical transmittance over 80.0% at a wavelength of 500 nm (T500), yellow indices (b*) in the range of 1.01-5.20, and haze values lower than 1.0%. In addition, the FDAn-PI films showed low optical retardance with optical retardation (Rth) values in the range of 31.7-390.6 nm. At the same time, the FDAn-PI films exhibited extremely high glass transition temperatures (Tg) over 420 °C according to dynamic mechanical analysis (DMA) tests. The FDAn-PI films showed good dimensional stability at elevated temperatures with linear coefficients of thermal expansion (CTE) in the range of (31.8-45.8) × 10-6/K.

Design, Synthesis and Properties of Semi-Alicyclic Colorless and Transparent Polyimide Films with High Glass Transition Temperatures and Low Retardation for Potential Applications in Flexible Electronics.

Polyimide (PI) optical films with high glass transition temperatures (high-Tg), high optical transparency, and low optical retardations (low-Rth) are highly desired in advanced optoelectronic applications. However, the standard PI films usually suffer from deep colors, high optical anisotropies and limited Tg values. In the current work, a series of semi-alicyclic colorless and transparent PI (CPI) films were developed from hydrogenated pyromellitic dianhydride stereoisomers, 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride, and fluorene-containing diamines, including 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(3-fluoro-4-aminophenyl)fluorene, respectively. The derived CPI films showed Tg values higher than 420 °C according to differential scanning calorimetry measurements. In addition, the fluorene-based CPI film showed optical transmittances higher than 80% at the wavelength of 400 nm, with yellow indices in the range of 0.60~1.01 and haze values below 3.0%. The CPI films showed average refractive indices from 1.5407 to 1.6309, extremely low birefringence at the level of minus fourth power of ten, and further exhibited quite low optical retardations below 10 nm.

A mitochondria-targeted multifunctional nanoplatform combining carbon monoxide delivery with O2-independent free radical burst under 1064 nm light irradiation for efficient hypoxic tumor therapy.

In situ mitochondrial oxidative stress amplification is an effective strategy to improve efficacy of cancer treatment. In this work, a tumor and mitochondria dual-targeted multifunctional nanoplatform CMS@AIPH@PDA@COTPP@FA (CAPCTF) was prepared, in which a thermally decomposable radical initiator AIPH was loaded inside the mesoporores of CuxMoySz (CMS) nanoparticles with polydopamine (PDA) covered films that were further covalently functionalized by a mitochondria-targeted CO donor (COTPP) and a directing group of folic acid (FA). The prepared CAPCTF nanoplatform selectively accumulated in cancer cells and further targeted the mitochondrial organelle where carbon monoxide (CO) and O2-independent free radicals (•OH/•R) were in situ generated upon 1064 nm laser irradiation. Furthermore, the CMS nanocarrier was capable of depleting the GSH overexpressed in the tumor microenvironment (TME), thus preventing free radical scavenging. As a result, the CAPCTF nanoplatform exhibited outstanding in vitro and in vivo antitumor efficacy under hypoxic conditions. This provides an innovative strategy that combines O2-independent free radicals (•OH/•R) generation, CO delivery and GSH consumption to amplify intracellular oxidative stresses and induce mitochondrial dysfunction, thus leading to cancer cells eradication, which may have significant implications for personalized hypoxic tumor treatment.

Anti-Tumor Immunity Induced by a Ternary Membrane System Derived From Cancer Cells, Dendritic Cells, and Bacteria.

Cancer vaccines generally are limited by insufficient tumor-specific cellular immunogenicity. Herein, a potent "ABC" ternary membrane-derived vaccine system blended from antigen-presenting mature dendritic cell membranes ("A"), bacterial E. coli cytoplasmic membranes ("B"), and cancer cell membranes ("C") is developed using a block-copolymer micelle-enabled approach. The respective ABC membrane components provide for a source of cellular immune communication/activation and enhanced accumulation in lymph nodes (A), immunological adjuvant (B), and tumor antigens (C). The introduction of dendritic cell (DC) membranes enables multiple cell-to-cell communication and powerful immune activation. ABC activates dendritic cells and promotes T-cell activation and proliferation in vitro. In vivo, ABC is 14- and 304-fold more immunogenic than binary (BC) and single (C) membrane vaccines, and immunization with ABC enhances the frequency of tumor-specific cytotoxic T lymphocytes, leading to an 80% cure rate in tumor-bearing mice. In a surgical resection and recurrence model, ABC prevents recurrence with vaccination from autologous cancer membranes, and therapeutic effects are observed in a lung metastasis model even with heterologous cancer cell membranes. ABCs formed from human cancer patient-derived tumor cells activate human monocyte-derived dendritic cells (moDC). Taken together, the ternary ABC membrane system provides the needed functional components for personalized cancer immunotherapy.

Preparation and Characterization of Light-Colored Polyimide Nanocomposite Films Derived from a Fluoro-Containing Semi-Alicyclic Polyimide Matrix and Colloidal Silica with Enhanced High-Temperature Dimensionally Stability.

Light-colored and transparent polyimide (PI) films with good high-temperature dimensional stability are highly desired for advanced optoelectronic applications. However, in practice, the simultaneous achievement of good optical and thermal properties in one PI film is usually difficult due to the inter-conflicting molecular design of the polymers. In the present work, a series of PI-SiO2 nanocomposite films (ABTFCPI) were developed based on the PI matrix derived from hydrogenated pyromellitic anhydride (HPMDA) and an aromatic diamine containing benzanilide and trifluoromethyl substituents in the structure, 2,2'-bis(trifluoromethyl)-4,4'-bis [4-(4-aminobenzamide)]biphenyl (ABTFMB). The inorganic SiO2 fillers were incorporated into the nanocomposite films in the form of colloidal nanoparticles dispersed in the good solvent of N,N-dimethylacetamide (DMAc) for the PI matrix. The derived ABTFCPI nanocomposite films showed good film-forming ability, flexible and tough nature, good optical transparency, and good thermal properties with loading amounts of SiO2 up to 30 wt% in the system. The ABTFCPI-30 film with a SiO2 content of 30 wt% in the film showed an optical transmittance of 79.6% at the wavelength of 400 nm (T400) with a thickness of 25 µm, yellow index (b*) of 2.15, and 5% weight loss temperatures (T5%) of 491 °C, which are all comparable to those the pristine ABTFCPI-0 matrix without filler (T400 = 81.8%; b* = 1.77; T5% = 492 °C). Meanwhile, the ABTFCPI-30 film exhibited obviously enhanced high-temperature dimensional stability with linear coefficients of thermal expansion (CTE) of 25.4 × 10-6/K in the temperature range of 50 to 250 °C, which is much lower than that of the AMTFCPI-0 film (CTE = 32.7 × 10-6/K).

A Multifunctional Nanozyme with NADH Dehydrogenase-Like Activity and Nitric Oxide Release under Near-Infrared Light Irradiation as an Efficient Therapeutic for Antimicrobial Resistance Infection and Wound Healing.

In recent years, antimicrobial resistance (AMR) has become one of the greatest threats to human health. There is an urgent need to develop new antibacterial agents to effectively treat AMR infection. Herein, a novel nanozyme platform (Cu,N-GQDs@Ru-NO) is prepared, where Cu,N-doped graphene quantum dots (Cu,N-GQDs) are covalently functionalized with a nitric oxide (NO) donor, ruthenium nitrosyl (Ru-NO). Under 808 nm near-infrared (NIR) light irradiation, Cu,N-GQDs@Ru-NO demonstrates nicotinamide adenine dinucleotide (NADH) dehydrogenase-like activity for photo-oxidizing NADH to NAD+ , thus disrupting the redox balance in bacterial cells and resulting in bacterial death; meanwhile, the onsite NIR light-delivered NO effectively eradicates the methicillin-resistant Staphylococcus aureus (MRSA) bacterial and biofilms, and promotes wound healing; furthermore, the nanozyme shows excellent photothermal effect that enhances the antibacterial efficacy as well. With the combination of NADH dehydrogenase activity, photothermal therapy, and NO gas therapy, the Cu,N-GQDs@Ru-NO nanozyme displays both in vitro and in vivo excellent efficacy for MRSA infection and biofilm eradication, which provides a new therapeutic modality for effectively treating MRSA inflammatory wounds.

Imaging of Gastrointestinal Tract Ailments.

Gastrointestinal (GI) disorders comprise a diverse range of conditions that can significantly reduce the quality of life and can even be life-threatening in serious cases. The development of accurate and rapid detection approaches is of essential importance for early diagnosis and timely management of GI diseases. This review mainly focuses on the imaging of several representative gastrointestinal ailments, such as inflammatory bowel disease, tumors, appendicitis, Meckel's diverticulum, and others. Various imaging modalities commonly used for the gastrointestinal tract, including magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT), and photoacoustic tomography (PAT) and multimodal imaging with mode overlap are summarized. These achievements in single and multimodal imaging provide useful guidance for improved diagnosis, staging, and treatment of the corresponding gastrointestinal diseases. The review evaluates the strengths and weaknesses of different imaging techniques and summarizes the development of imaging techniques used for diagnosing gastrointestinal ailments.

Contracted Fe-N5-C11 Sites in Single-Atom Catalysts Boosting Catalytic Performance for Oxygen Reduction Reaction.

Promoting the catalyst performance for oxygen reduction reaction (ORR) in energy conversion devices through controlled manipulation of the structure of catalytic active sites has been a major challenge. In this work, we prepared Fe-N-C single-atom catalysts (SACs) with Fe-N5 active sites and found that the catalytic activity of the catalyst with shrinkable Fe-N5-C11 sites for ORR was significantly improved compared with the catalyst bearing normal Fe-N5-C12 sites. The catalyst C@PVI-(TPC)Fe-800, prepared by pyrolyzing an axial-imidazole-coordinated iron corrole precursor, exhibited positive shifted half-wave potential (E1/2 = 0.89 V vs RHE) and higher peak power density (Pmax = 129 mW/cm2) than the iron porphyrin-derived counterpart C@PVI-(TPP)Fe-800 (E1/2 = 0.81 V, Pmax = 110 mW/cm2) in 0.1 M KOH electrolyte and Zn-air batteries, respectively. X-ray absorption spectroscopy (XAS) analysis of C@PVI-(TPC)Fe-800 revealed a contracted Fe-N5-C11 structure with iron in a higher oxidation state than the porphyrin-derived Fe-N5-C12 counterpart. Density functional theory (DFT) calculations demonstrated that C@PVI-(TPC)Fe-800 possesses a higher HOMO energy level than C@PVI-(TPP)Fe-800, which can increase its electron-donating ability and thus help achieve enhanced O2 adsorption as well as O-O bond activation. This work provides a new approach to tune the active site structure of SACs with unique contracted Fe-N5-C11 sites that remarkably promote the catalyst performance, suggesting significant implications for catalyst design in energy conversion devices.

Cellular membrane-targeting ruthenium complexes as efficient photosensitizers for broad-spectrum antibacterial activity.

A ruthenium complex [Ru(phen)2(phen-5-amine)-C14] (Ru-C14) with broad-spectrum antibacterial activity was designed and synthesized; positively charged Ru-C14 could target bacteria via electrostatic interactions and showed high binding effectiveness to cell membranes. In addition, Ru-C14 could act as a photosensitizer. Under 465 nm light irradiation, Ru-C14 could generate 1O2, thus disrupting the bacterial intracellular redox balance and leading to bacterial death. Ru-C14 also exhibited minimum inhibitory concentration values of 6.25 µM against Escherichia coli and 3.125 µM against Staphylococcus aureus; these values are lower than those of streptomycin and methicillin. This work combined the merits of cell membrane targeting and photodynamic therapy for antibacterial activity. The findings might open up a new avenue for effective anti-infection treatment and other medical applications.

A P-doped PtNi alloy supported on N,C-doped TiO2 nanosheets as a stable electrocatalyst for the oxygen reduction reaction in an acidic electrolyte.

A P-doped PtNi alloy loaded on N,C-doped TiO2 nanosheets (P-PtNi@N,C-TiO2) exhibited excellent activity and durability for the oxygen reduction reaction (ORR) in 0.1 M HClO4 solution with mass (4×) and specific (6×) activity several times higher than those of commercial 20 wt% Pt/C, respectively. The P dopant mitigated the dissolution of Ni and strong interactions between the catalyst and the N,C-TiO2 support inhibited catalyst migration. This provides a new approach for the design of high-performance non-carbon-supported low-Pt catalysts to be used in harsh acidic environments.