A universal approach to dual-metal-atom catalytic sites confined in carbon dots for various target reactions.

Here, a molecular-design and carbon dot-confinement coupling strategy through the pyrolysis of bimetallic complex of diethylenetriamine pentaacetic acid under low-temperature is proposed as a universal approach to dual-metal-atom sites in carbon dots (DMASs-CDs). CDs as the "carbon islands" could block the migration of DMASs across "islands" to achieve dynamic stability. More than twenty DMASs-CDs with specific compositions of DMASs (pairwise combinations among Fe, Co, Ni, Mn, Zn, Cu, and Mo) have been synthesized successfully. Thereafter, high intrinsic activity is observed for the probe reaction of urea oxidation on NiMn-CDs. In situ and ex situ spectroscopic characterization and first-principle calculations unveil that the synergistic effect in NiMn-DMASs could stretch the urea molecule and weaken the N-H bond, endowing NiMn-CDs with a low energy barrier for urea dehydrogenation. Moreover, DMASs-CDs for various target electrochemical reactions, including but not limited to urea oxidation, are realized by optimizing the specific DMAS combination in CDs.

Anionic Ionomer: Released Surface-Immobilized Cations and an Established Hydrophobic Microenvironment for Efficient and Durable CO2-to-Ethylene Electrosynthesis at High Current over One Month.

Electrosynthesis of multicarbon products, such as C2H4, from CO2 reduction on copper (Cu) catalysts holds promise for achieving carbon neutrality. However, maintaining a steady high current-level C2H4 electrosynthesis still encounters challenges, arising from unstable alkalinity and carbonate precipitation caused by undesired ion migration at the cathode under a repulsive electric field. To address these issues, we propose a universal "charge release" concept by incorporating tiny amounts of an oppositely charged anionic ionomer (e.g., perfluorinated sulfonic acid, PFSA) into a cationic covalent organic framework on the Cu surface (cCOF/PFSA). This strategy effectively releases the hidden positive charge within the cCOF, enhancing surface immobilization of cations to impede both outward migration of generated OH- and inward migration of cations, inhibiting carbonate precipitation and creating a strong alkaline microenvironment. Meanwhile, the ionomer's hydrophobic chains create a hydrophobic environment within the cCOF, facilitating efficient gas transport. In situ characterizations and theoretical calculations demonstrate that the cCOF/PFSA catalyst establishes a hydrophobic strong alkaline microenvironment, optimizing the adsorption strength and configuration of *CO intermediates to promote the C2H4 formation. The optimized catalyst achieves a 70.5% Faradaic efficiency for C2H4 with a partial current density over 470 mA cm-2. Notably, it delivers a high single-pass carbon efficiency of 96.5% for CO2RR and sustains an exceptional stability over 760 h. When implemented in a large-area MEA electrolyzer and a 5-cell MEA stack, the system achieves an industrial current of 15 A and continuous C2H4 production exceeding 19 mL min-1, marking a significant step toward industrial feasibility in CO2RR-to-C2H4 conversion.

Advanced Nanocarbons Toward two-Electron Oxygen Electrode Reactions for H2O2 Production and Integrated Energy Conversion.

Hydrogen peroxide (H2O2) plays a pivotal role in advancing sustainable technologies due to its eco-friendly oxidizing capability. The electrochemical two-electron (2e-) oxygen reduction reaction and water oxidation reaction present an environmentally green method for H2O2 production. Over the past three years, significant progress is made in the field of carbon-based metal-free electrochemical catalysts (C-MFECs) for low-cost and efficient production of H2O2 (H2O2EP). This article offers a focused and comprehensive review of designing C-MFECs for H2O2EP, exploring the construction of dual-doping configurations, heteroatom-defect coupling sites, and strategic dopant positioning to enhance H2O2EP efficiency; innovative structural tuning that improves interfacial reactant concentration and promote the timely release of H2O2; modulation of electrolyte and electrode interfaces to support the 2e- pathways; and the application of C-MFECs in reactors and integrated energy systems. Finally, the current challenges and future directions in this burgeoning field are discussed.

Interface Engineering Overall Seawater Splitting of Self-Supporting CeOx@NiCo2O4 Arrays.

Exploring advanced electrocatalysts for overall seawater splitting is of great significance for large-scale green hydrogen production in which interface engineering has been considered as an effective strategy to enhance the intrinsic activities of the electrocatalysts. In this work, CeOx-modified NiCo2O4 nanoneedle arrays are designed and constructed in situ grown on Ni foam (NF) through a facile two-step synthesis method. Density functional theory calculations reveal that the strong interaction between CeOx and NiCo2O4 can regulate the electronic states of metal surfaces and optimize the electronic structures of the materials, essentially improving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) properties. Specifically, in alkaline electrolytes, CeOx@NiCo2O4/NF exhibits superior electrocatalytic activities and stabilities, requiring overpotentials of 238 mV for the OER and 144 mV for the HER to achieve a current density of 10 mA cm-2. When applied to a simulated seawater splitting device, the CeOx@NiCo2O4/NF also maintains a battery voltage of 1.66 V to reach 10 mA cm-2 and exhibits good stability for over 60 h, with high faradic efficiencies (FEs) close to 100% for both the OER and HER.

Regulation of fadR on the ROS defense mechanism in Shewanalla oneidensis.

Protein FadR is known as a fatty acid metabolism global regulator that sustains cell envelope integrity by changing the profile of fatty acid. Here, we present its unique participation in the defense against reactive oxygen species (ROS) in the bacterium. FadR contributes to defending extracellular ROS by maintaining the permeability of the cell membrane. It also facilitates the ROS detoxification process by increasing the expression of ROS neutralizers (KatB, KatG, and AhpCF). FadR also represses the leakage of ROS by alleviating the respiratory action conducted by terminal cytochrome cbb3-type heme-copper oxidases (ccoNOQP). These findings suggest that FadR plays a comprehensive role in modulating the bacterial oxidative stress response, instead of merely strengthening the cellular barrier against the environment. This study sheds light on the complex mechanisms of bacterial ROS defense and offers FadR as a novel target for ROS control research.

Electrochemical C-N coupling of CO2 and nitrogenous small molecules for the electrosynthesis of organonitrogen compounds.

Electrochemical C-N coupling reactions based on abundant small molecules (such as CO2 and N2) have attracted increasing attention as a new "green synthetic strategy" for the synthesis of organonitrogen compounds, which have been widely used in organic synthesis, materials chemistry, and biochemistry. The traditional technology employed for the synthesis of organonitrogen compounds containing C-N bonds often requires the addition of metal reagents or oxidants under harsh conditions with high energy consumption and environmental concerns. By contrast, electrosynthesis avoids the use of other reducing agents or oxidants by utilizing "electrons", which are the cleanest "reagent" and can reduce the generation of by-products, consistent with the atomic economy and green chemistry. In this study, we present a comprehensive review on the electrosynthesis of high value-added organonitrogens from the abundant CO2 and nitrogenous small molecules (N2, NO, NO2-, NO3-, NH3, etc.) via the C-N coupling reaction. The associated fundamental concepts, theoretical models, emerging electrocatalysts, and value-added target products, together with the current challenges and future opportunities are discussed. This critical review will greatly increase the understanding of electrochemical C-N coupling reactions, and thus attract research interest in the fixation of carbon and nitrogen.

Main-Group Metal-Nonmetal Dynamic Proton Bridges Enhance Ammonia Electrosynthesis.

The electrochemical nitrogen reduction reaction (eNRR) is a crucial process for the sustainable production of ammonia (NH3) for energy and agriculture applications. However, the reaction's efficiency is highly dependent on the activation of the inert N≡N bond, which is hindered by the electron back-donation to the π* orbitals of the N≡N bond, resulting in low eNRR capacity. Herein, we report a main-group metal-nonmetal (O-In-S) eNRR catalyst featuring a dynamic proton bridge, with In-S serving as the polarization pair and O functioning as the dynamic electron pool. In situ spectroscopic analysis and theoretical calculations reveal that the In-S polarization pair acts as asymmetric dual-sites, polarizing the N≡N bond by concurrently back-donating electrons to both the πx* and πy* orbitals of N2, thereby overcoming the significant band gap limitations, while inhibiting the competitive hydrogen evolution reaction. Meanwhile, the O dynamic electron pool acts as a "repository" for electron storage and donation to the In-S polarization pair. As a result, the O-In-S dynamic proton bridge exhibits exceptional NH3 yield rates and Faradaic efficiencies (FEs) across a wide potential window of 0.3 V, with an optimal NH3 yield rate of 80.07±4.25 µg h-1 mg-1 and an FE of 38.01±2.02 %, outperforming most previously reported catalysts.

Accelerated Proton-Coupled Electron Transfer via Engineering Palladium Sub-Nanoclusters for Scalable Electrosynthesis of Hydrogen Peroxide.

Electrosynthesis of H2O2 from oxygen reduction reaction via a two-electron pathway is vital as an alternative for the energy-intensive anthraquinone process. However, this process is largely hindered in neutral and alkaline conditions due to sluggish kinetics associated with the transformation of intermediate O2* into OOH* via proton-coupled electron transfer sourced from slow water dissociation. Herein, we developed Pd sub-nanoclusters on the nickel ditelluride nanosheets (Pd SNCs/NiTe2) to enhance the performance of H2O2 electrosynthesis. The newly-developed Pd SNCs/NiTe2 exhibited a H2O2 selectivity of as high as 99 % and a positive shift of onset potential up to 0.81 V. Combined theoretical calculations and experimental studies (e.g., X-ray absorption and attenuated total reflectance-Fourier transform infrared spectra measurements) revealed that the Pd sub-nanoclusters supported by NiTe2 nanosheets efficiently reduced the energy barrier of water dissociation to generate more protons, facilitating the proton feeding kinetics. When used in a flow cell, Pd SNCs/NiTe2 cathode efficiently produced H2O2 with a maximum yield rate of 1.75 mmol h-1 cm-2 and a current efficiency of 95 % at 100 mA cm-2. Further, an accumulated H2O2 concentration of 1.43 mol L-1 was reached after 10 hours of continuous electrolysis, showing the potential for practical H2O2 electrosynthesis.

MiR146a modulates chondrogenesis of bone marrow mesenchymal stem cells by modulating Lsm11 expression.

MicroRNAs play a critical role in bone marrow mesenchymal stem cell (MSC) chondrogenesis and regulate the progression of joint regeneration in osteoarthritis. Our previous research confirmed that miR146a relieves osteoarthritis by modulating cartilage homeostasis. However, few studies have revealed the relationship between miR146a and the chondrogenesis of MSCs, and the exact mechanisms remain unclear. This study aimed to determine the function of miR146a in the chondrogenic differentiation of MSCs and the potential mechanisms involved. MiR146a expression increased during chondrogenesis. MiR146a knockout (KO) led to the increased chondrogenesis of MSCs compared to that in wild-type (WT) MSCs, whereas the overexpression of miR146a by mimics resulted in the decreased chondrogenesis of MSCs, as determined by the mRNA expression of collagen, type II, alpha 1 (COL2A1), aggrecan, cartilage oligomeric matrix protein (COMP), and matrix metallopeptidase 13 (MMP13). Furthermore, cartilage defects could be treated better when injected with spheres induced from miR146aKO MSCs than from WT MSCs, indicating that miR146a inhibits chondrogenesis in vivo. In addition, based on miRNA-mRNA prediction analysis and a dual-luciferase reporter assay, we observed that the deletion of miR146a led to the increased expression of Lsm11 during chondrogenesis and demonstrated that miR146a targeted Lsm11 by binding to its 3'-untranslated region (UTR) and inhibited its translation. The inhibition of Lsm11 by silencing RNA (siRNA) reversed the increased ability of chondrogenesis by knocking out miR146a both in vivo and in vitro, suggesting that miR146a inhibits chondrogenesis by directly inhibiting Lsm11 in MSCs, which may be a novel target for treating osteoarthritis.

Bionic Mineralization toward Scalable MOF Films for Ampere-Level Biomass Upgrading.

With significant advances in metal-organic framework (MOF) nanostructure preparation, however, the facile synthesis of large-scale MOF films with precise control of the interface structure and surface chemistry is still challenging to achieve with satisfactory performance. Herein, we introduce a universal strategy bridging metal corrosion chemistry and bionic mineralization to synthesize 16 MOF films on 7 metal supports under ambient conditions. The robustness to explore unlimited libraries of MOF films (e.g., carboxylate-, N-heterocycle-, phenolic-, and phosphonate-MOFs) on supports is evoked by independently regulating the metal redox behavior, electrolyte properties, and organic ligands along with hydrogen evolution or oxygen reduction, which offers the basic guidelines for regulating the microstructure and composition of MOFs on the Pourbaix diagram. In conjunction with multiple manufacturing methods, we demonstrated proof of concept for "printing" a large variety of MOF patterns from micrometer to meter scales. Furthermore, a large-area electrolyzer (64 cm2) devised enables 5-hydroxymethylfurfural oxidation to achieve a record-breaking current of 3.0 A at 1.63 V with 2,5-furandicarboxylic acid production, leading to the simultaneous production of H2 gas and valuable feedstocks. The improved electrocatalytic activity for significantly boosting the 5-hydroxymethylfurfural oxidation exemplifies one of the functional MOF films for given applications beyond biomass upgrading.

Hydrophobic, Ultrastable Cuδ+ for Robust CO2 Electroreduction to C2 Products at Ampere-Current Levels.

Copper (Cu) is the only known material that can efficiently electrocatalyze CO2 to value-added multicarbon products. Owing to the instability of the Cuδ+ state and microscopic structure in reactions, Cu catalysts are still facing big challenges with low selectivity and poor durability, particularly at high current densities. Herein, we report a rational one-step surface coordination approach for the synthesis of Cu dendrites with an ultrastable Cuδ+ state and hydrophobicity (Cu CF), even after exposure to air for over 6 months. As a result, Cu CF exhibited a C2 FE of 90.6% at a partial current density of 453.3 mA cm-2 in a flow cell. A 400 h stable electrolysis at 800 mA and even a ground-breaking stable operation at a large industrial current of 10 A were achieved in the membrane electrode assembly (MEA) form. We further demonstrated a continuous production of C2H5OH solution with 90% relative purity at 600 mA over 50 h in a solid-electrolyte reactor. Spectroscopy and computation results suggested that Cu(II) carboxylate coordination species formed on the surface of Cu CF, which ensured the stability of the Cuδ+ state and hydrophobicity. As a result, rich active sites and a stable three-phase interface on the catalyst surface were achieved, along with the optimized *CO adsorption strength and adsorption configuration. The mixed *CO adsorption configurations on Cu CF made the *CO dimerization process easier, which promoted the conversion of CO2 to C2 products. This work provides a promising paradigm for the design and development of Cu-based catalysts with ultrahigh stability under industrial current densities.

Carbon-Based Electrocatalysts for Acidic Oxygen Reduction Reaction.

Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best-known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large-scale applications. Recent breakthroughs in carbon-based metal-free electrochemical catalysts (C-MFECs) show great potential for earth-abundant carbon materials as low-cost metal-free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C-MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure-property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed.

Carbon Electrode Materials for Advanced Potassium-Ion Storage.

Tremendous progress has been made in the field of electrochemical energy storage devices that rely on potassium-ions as charge carriers due to their abundant resources and excellent ion transport properties. Nevertheless, future practical developments not only count on advanced electrode materials with superior electrochemical performance, but also on competitive costs of electrodes for scalable production. In the past few decades, advanced carbon materials have attracted great interest due to their low cost, high selectivity, and structural suitability and have been widely investigated as functional materials for potassium-ion storage. This article provides an up-to-date overview of this rapidly developing field, focusing on recent advanced and mechanistic understanding of carbon-based electrode materials for potassium-ion batteries. In addition, we also discuss recent achievements of dual-ion batteries and conversion-type K-X (X=O2 , CO2 , S, Se, I2 ) batteries towards potential practical applications as high-voltage and high-power devices, and summarize carbon-based materials as the host for K-metal protection and possible directions for the development of potassium energy-related devices as well. Based on this, we bridge the gaps between various carbon-based functional materials structure and the related potassium-ion storage performance, especially provide guidance on carbon material design principles for next-generation potassium-ion storage devices.

Accelerated Transfer and Spillover of Carbon Monoxide through Tandem Catalysis for Kinetics-boosted Ethylene Electrosynthesis.

Cu-based catalysts have been widely applied in electroreduction of carbon dioxide (CO2 ER) to produce multicarbon (C2+ ) feedstocks (e.g., C2 H4 ). However, the high energy barriers for CO2 activation on the Cu surface is a challenge for a high catalytic efficiency and product selectivity. Herein, we developed an in situ *CO generation and spillover strategy by engineering single Ni atoms on a pyridinic N-enriched carbon support with a sodalite (SOD) topology (Ni-SOD/NC) that acted as a donor to feed adjacent Cu nanoparticles (NPs) with *CO intermediate. As a result, a high C2 H4 selectivity of 62.5 % and an industrial-level current density of 160 mA cm-2 at a low potential of -0.72 V were achieved. Our studies revealed that the isolated NiN3 active sites with adjacent pyridinic N species facilitated the *CO desorption and the massive *CO intermediate released from Ni-SOD/NC then overflowed to Cu NPs surface to enrich the *CO coverage for improving the selectivity of CO2 ER to C2 H4 .

Single-atom Iron Catalyst with Biomimetic Active Center to Accelerate Proton Spillover for Medical-level Electrosynthesis of H2 O2 Disinfectant.

Electrosynthesis of H2 O2 has great potential for directly converting O2 into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical-level H2 O2 production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (FeSA -NS/C). The newly-developed FeSA -NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H2 O2 at a high current of 100 mA cm-2 with a record high H2 O2 selectivity of 90 %. An accumulated H2 O2 concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally-designed catalytic active center with the atomic Fe site stabilized by three-coordinated nitrogen atoms and one-sulfur atom (Fe-N3 S-C). It was further found that the replacement of one N atom with S atom in the classical Fe-N4 -C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H2 O2 electrosynthesis.

Carbon-based metal-free electrocatalysts: from oxygen reduction to multifunctional electrocatalysis.

Since the discovery of N-doped carbon nanotubes as the first carbon-based metal-free electrocatalyst (C-MFEC) for oxygen reduction reaction (ORR) in 2009, C-MFECs have shown multifunctional electrocatalytic activities for many reactions beyond ORR, such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), and hydrogen peroxide production reaction (H2O2PR). Consequently, C-MFECs have attracted a great deal of interest for various applications, including metal-air batteries, water splitting devices, regenerative fuel cells, solar cells, fuel and chemical production, water purification, to mention a few. By altering the electronic configuration and/or modulating their spin angular momentum, both heteroatom(s) doping and structural defects (e.g., atomic vacancy, edge) have been demonstrated to create catalytic active sites in the skeleton of graphitic carbon materials. Although certain C-MFECs have been made to be comparable to or even better than their counterparts based on noble metals, transition metals and/or their hybrids, further research and development are necessary in order to translate C-MFECs for practical applications. In this article, we present a timely and comprehensive, but critical, review on recent advancements in the field of C-MFECs within the past five years or so by discussing various types of electrocatalytic reactions catalyzed by C-MFECs. An emphasis is given to potential applications of C-MFECs for energy conversion and storage. The structure-property relationship for and mechanistic understanding of C-MFECs will also be discussed, along with the current challenges and future perspectives.

Electrocatalysis for CO2 conversion: from fundamentals to value-added products.

The continuously increasing CO2 released from human activities poses a great threat to human survival by fluctuating global climate and disturbing carbon balance among the four reservoirs of the biosphere, earth, air, and water. Converting CO2 to value-added feedstocks via electrocatalysis of the CO2 reduction reaction (CO2RR) has been regarded as one of the most attractive routes to re-balance the carbon cycle, thanks to its multiple advantages of mild operating conditions, easy handling, tunable products and the potential of synergy with the rapidly increasing renewable energy (i.e., solar, wind). Instead of focusing on a special topic of electrocatalysts for the CO2RR that have been extensively reviewed elsewhere, we herein present a rather comprehensive review of the recent research progress, in the view of associated value-added products upon selective electrocatalytic CO2 conversion. We initially provide an overview of the history and the fundamental science regarding the electrocatalytic CO2RR, with a special introduction to the design, preparation, and performance evaluation of electrocatalysts, the factors influencing the CO2RR, and the associated theoretical calculations. Emphasis will then be given to the emerging trends of selective electrocatalytic conversion of CO2 into a variety of value-added products. The structure-performance relationship and mechanism will also be discussed and investigated. The outlooks for CO2 electrocatalysis, including the challenges and opportunities in the development of new electrocatalysts, electrolyzers, the recently rising operando fundamental studies, and the feasibility of industrial applications are finally summarized.

Promoting CO2 Electroreduction Kinetics on Atomically Dispersed Monovalent ZnI Sites by Rationally Engineering Proton-Feeding Centers.

Electrocatalytic reduction of CO2 (CO2 RR) to value-added chemicals is of great significance for CO2 utilization, however the CO2 RR process involving multi-electron and proton transfer is greatly limited by poor selectivity and low yield. Herein, We have developed an atomically dispersed monovalent zinc catalyst anchored on nitrogenated carbon nanosheets (Zn/NC NSs). Benefiting from the unique coordination environment and atomic dispersion, the Zn/NC NSs exhibit a superior CO2 RR performance, featuring a high current density up to 50 mA cm-2 with an outstanding CO Faradaic efficiency of ≈95 %. The center ZnI atom coordinated with three N atoms and one N atom that bridges over two adjacent graphitic edges (Zn-N3+1 ) is identified as the catalytically active site. Experimental results reveal that the twisted Zn-N3+1 structure accelerates CO2 activation and protonation in the rate-determining step of *CO2 to *COOH, while theoretical calculations elucidate that atomically dispersed Zn-N3+1 moieties decrease the potential barriers for intermediate COOH* formation, promoting the proton-coupled CO2 RR kinetics and boosting the overall catalytic performance.

Tumor Necrosis Factor Receptor Associated Factor 3 Modulates Cartilage Degradation through Suppression of Interleukin 17 Signaling.

Interleukin 17A (IL-17A) is critical in the pathogenesis of autoimmune diseases through driving inflammatory cascades. However, the role of IL-17 in osteoarthritis (OA) is not well understood. Tumor necrosis factor-receptor-associated factor 3 (TRAF3) is a receptor proximal negative regulator of IL-17 signaling. It remains unclear whether TRAF3 exerts regulatory effects on cartilage degradation and contributes to the pathogenesis of OA. In this study, we found that TRAF3 notably suppressed IL-17-induced NF-κB and mitogen-activated protein kinase activation and, subsequently, the production of matrix-degrading enzymes. TRAF3 depletion enhanced IL-17 signaling, along with increased matrix-degrading enzyme production. In vivo, cartilage destruction caused by surgery-induced OA was alleviated markedly both in 1l17a-deficient mice and in TRAF3 transgenic mice. In contrast, silencing TRAF3 through adenoviruses worsened cartilage degradation in experimental OA. Moreover, the destructive effect of IL-17 on cartilage was abolished in TRAF3 transgenic mice in an IL-17 intra-articular injection animal model. Similarly, genetic deletion of IL-17 blocked TRAF3 knockdown-mediated promotion of cartilage destruction, suggesting that the protective effect of TRAF3 on cartilage is mediated by its suppression of IL-17 signaling. Collectively, our results suggest that TRAF3 negatively regulates IL-17-mediated cartilage degradation and pathogenesis of OA, and may serve as a potential new therapy target for OA.

Understanding of catalytic ROS generation from defect-rich graphene quantum-dots for therapeutic effects in tumor microenvironment.

Owing to their low cost, high catalytic efficiency and biocompatibility, carbon-based metal-free catalysts (C-MFCs) have attracted intense interest for various applications, ranging from energy through environmental to biomedical technologies. While considerable effort and progress have been made in mechanistic understanding of C-MFCs for non-biomedical applications, their catalytic mechanism for therapeutic effects has rarely been investigated. In this study, defect-rich graphene quantum dots (GQDs) were developed as C-MFCs for efficient ROS generation, specifically in the H2O2-rich tumor microenvironment to cause multi-level damages of subcellular components (even in nuclei). While a desirable anti-cancer performance was achieved, the catalytic performance was found to strongly depend on the defect density. It is for the first time that the defect-induced catalytic generation of ROS by C-MFCs in the tumor microenvironment was demonstrated and the associated catalytic mechanism was elucidated. This work opens a new avenue for the development of safe and efficient catalytic nanomedicine.