Oxidation‐Responsive Nanoassemblies for Light‐Enhanced Gene Therapy

Microenvironment‐responsive supramolecular assemblies have attracted great interest in the biomedical field due to their potential applications in controlled drug release. In this study, oxidation‐responsive supramolecular polycationic assemblies named CPAs are prepared for nucleic acid delivery via the host–guest interaction of β‐cyclodextrin based polycations and a ferrocene‐functionalized zinc tetraaminophthalocyanine core. The reactive oxygen species (ROS) can accelerate the disassembly of CPA/pDNA complexes, which would facilitate the release of pDNA in the complexes and further benefit the subsequent transfection. Such improvement in transfection efficiency is proved in A549 cells with high H₂O₂ concentration. Interestingly, the transfection efficiencies mediated by CPAs are also different in the presence or absence of light in various cell lines such as HEK 293 and 4T1. The single oxygen (¹O₂), produced by photosensitizers in the core of CPAs under light, increases the ROS amount and accelerates the disassembly of CPAs/pDNA complexes. In vitro and in vivo studies further illustrate that suppressor tumor gene p53 delivered by CPAs exhibits great antitumor effects under illumination. This work provides a promising strategy for the design and fabrication of oxidation‐responsive nanoassemblies with light‐enhanced gene transfection performance.     

A Targeted and FRET‐Based Ratiometric Fluorescent Nanoprobe for Imaging Mitochondrial Hydrogen Peroxide in Living Cells

Hydrogen peroxide (H₂O₂) is a prominent member of the reactive oxygen species family and plays crucial roles in living organisms, thus detecting H₂O₂ and elucidating its biological functions has become an important area of biological and biomedical research. Herein, a multifunctional fluorescent nanoprobe is demonstrated for detecting mitochondrial H₂O₂. The nanoprobe is prepared by covalently linking a mitochondria‐targeting ligand (triphenylphosphonium, TPP) and a H₂O₂ recognition element (PFl) onto carbon dots (CDs). For this nanoprobe, the CD serves as the carrier and the FRET donor. In the presence of H₂O₂, the PFl moieties on a CD undergo structural and spectral conversion, affording the nanoplatform a FRET‐based ratiometric probe for H₂O₂. The nanoprobe displays excellent water dispersibility, high sensitivity and selectivity, satisfactory cell permeability, and very low cytotoxicity. Following the living cell uptake, this nanoprobe can specifically target and stain the mitochondria; and it can detect the exogenous H₂O₂ in L929 cells, as well as the endogenously produced mitochondrial H₂O₂ in Raw 264.7 cells upon stimulation by PMA. This study shows that CDs can serve as promising nano‐carriers for fabricating practical multifunctional fluorescent nanosensors.     

Enhanced In Vitro Biocompatibility and Water Dispersibility of Magnetite and Cobalt Ferrite Nanoparticles Employed as ROS Formation Enhancer in Radiation Cancer Therapy

Efficient magnetic reactive oxygen species (ROS) formation enhancing agents after X‐ray treatment are realized by functionalizing superparamagnetic magnetite (Fe₃O₄) and Co‐ferrite (CoFe₂O₄) nanoparticles with self‐assembled monolayers (SAMs). The Fe₃O₄ and CoFe₂O₄ nanoparticles are synthesized using Massart's coprecipitation technique. Successful surface modification with the SAM forming compounds 1‐methyl‐3‐(dodecylphosphonic acid) imidazolium bromide, or (2‐{2‐[2‐hydroxy‐ethoxy]‐ethoxy}‐ethyl phosphonic acid provides biocompatibility and long‐term stability of the Fe₃O₄ and CoFe₂O₄ nanoparticles in cell media. The SAM‐stabilized ferrite nanoparticles are characterized with dynamic light scattering, X‐ray powder diffraction, a superconducting quantum interference device, Fourier transform infrared attenuated total reflectance spectroscopy, zeta potential measurements, and thermogravimetric analysis. The impact of the SAM‐stabilized nanoparticles on the viability of the MCF‐7 cells and healthy human umbilical vein endothelial cells (HUVECs) is assessed using the neutral red assay. Under X‐ray exposure with a single dosage of 1 Gy the intracellular SAM stabilized Fe₃O₄ and CoFe₂O₄ nanoparticles are observed to increase the level of ROS in MCF‐7 breast cancer cells but not in healthy HUVECs. The drastic ROS enhancement is associated with very low dose modifying factors for a survival fraction of 50%. This significant ROS enhancement effect by SAM‐stabilized Fe₃O₄ and CoFe₂O₄ nanoparticles constitutes their excellent applicability in radiation therapy.     

Artificial Natural Killer Cells for Specific Tumor Inhibition and Renegade Macrophage Re‐Education

Natural killer (NK) cells can not only recognize and eliminate abnormal cells but also recruit and re‐educate immune cells to protect the host. However, the functions of NK cells are often limited in the immunosuppressive tumor microenvironment (TME). Here, artificial NK cells (designated as aNK) with minor limitations of TME for specific tumor killing and renegade macrophage re‐education are created. The red blood cell membrane (RBCM) cloaks perfluorohexane (PFC) and glucose oxidase (GOX) to construct the aNK. The aNK can directly kill tumor cells by exhausting glucose and generating hydrogen peroxide (H₂O₂). The generated H₂O₂ is also similar to cytokines and chemokines for recruiting immune cells and re‐educating survived macrophages to attack tumor cells. In addition, the oxygen‐carried PFC can strengthen the catalytic reaction of GOX and normalize the hypoxic TME. In vitro and in vivo experiments display that aNK with slight TME limitations exhibit efficient tumor inhibition and immune activation. The aNK will provide a new sight to treat tumor as the supplement of aggressive NK cells.     

Synergistic Amplification of Oxidative Stress–Mediated Antitumor Activity via Liposomal Dichloroacetic Acid and MOF‐Fe2+

Cancer cells are susceptible to oxidative stress; therefore, selective elevation of intracellular reactive oxygen species (ROS) is considered as an effective antitumor treatment. Here, a liposomal formulation of dichloroacetic acid (DCA) and metal–organic framework (MOF)‐Fe²⁺ (MD@Lip) has been developed, which can efficiently stimulate ROS‐mediated cancer cell apoptosis in vitro and in vivo. MD@Lip can not only improve aqueous solubility of octahedral MOF‐Fe²⁺, but also generate an acidic microenvironment to activate a MOF‐Fe²⁺‐based Fenton reaction. Importantly, MD@Lip promotes DCA‐mediated mitochondrial aerobic oxidation to increase intracellular hydrogen peroxide (H₂O₂), which can be consequently converted to highly cytotoxic hydroxyl radicals (?OH) via MOF‐Fe²⁺, leading to amplification of cancer cell apoptosis. Particularly, MD@Lip can selectively accumulate in tumors, and efficiently inhibit tumor growth with minimal systemic adverse effects. Therefore, liposome‐based combination therapy of DCA and MOF‐Fe²⁺ provides a promising oxidative stress–associated antitumor strategy for the management of malignant tumors.     

Dye‐Anchored MnO Nanoparticles Targeting Tumor and Inducing Enhanced Phototherapy Effect via Mitochondria‐Mediated Pathway

Phototherapy is a promising treatment method for cancer therapy. However, the various factors have greatly restricted phototherapy development, including the poor accumulation of photosensitizer in tumor, hypoxia in solid tumor tissue and systemic phototoxicity. Herein, a mitochondrial‐targeted multifunctional dye‐anchored manganese oxide nanoparticle (IR808@MnO NP) is developed for enhancing phototherapy of cancer. In this nanoplatform, IR808 as a small molecule dye acts as a tumor targeting ligand to make IR808@MnO NPs with capacity to actively target tumor cells and relocate finally in the mitochondria. Meanwhile, continuous production of oxygen (O₂) and regulation of pH induced by the high reactivity and specificity of MnO NPs toward mitochondrial endogenous hydrogen peroxide (H₂O₂) could effectively modulate tumor hypoxia and lessen the tumor subacid environment. Large amounts of reactive oxide species (ROS) are generated during the reaction process between H₂O₂ and MnO NPs. Furthermore, under laser irradiation, IR808 in IR808@MnO NPs turns O₂ into a highly toxic singlet oxygen (¹O₂) and generates hyperthermia. The results indicate that IR808@MnO NPs have the high efficiency of specific targeting of tumors, relieving tumor subacid environment, improving the tumor hypoxia environment, and generating large amounts of ROS to kill tumor cells. It is expected to have a wide application in treating cancer.     

Hybrid Protein Nano‐Reactors Enable Simultaneous Increments of Tumor Oxygenation and Iodine‐131 Delivery for Enhanced Radionuclide Therapy

It is hard for current radionuclide therapy to render solid tumors desirable therapeutic efficacy owing to insufficient tumor‐targeted delivery of radionuclides and severe tumor hypoxia. In this study, a biocompatible hybrid protein nanoreactor composed of human serum albumin (HSA) and catalase (CAT) molecules is constructed via glutaraldehyde‐mediated crosslinking. The obtained HSA‐CAT nanoreactors (NRs) show retained and well‐protected enzyme stability in catalyzing the decomposition of H₂O₂ and enable efficient labeling of therapeutic radionuclide iodine‐131 (¹³¹I). Then, it is uncovered that such HSA‐CAT NRs after being intravenously injected into tumor‐bearing mice exhibit efficient passive tumor accumulation as vividly visualized under the fluorescence imaging system and gamma camera. As the result, such HSA‐CAT NRs upon tumor accumulation would significantly attenuate tumor hypoxia by decomposing endogenous H₂O₂ produced by cancer cells to molecular oxygen, and thereby remarkably improve the therapeutic efficacy of radionuclide ¹³¹I. This study highlights the concise preparation of biocompatible protein nanoreactors with efficient tumor homing and hypoxia attenuation capacities, thus enabling greatly improved tumor radionuclide therapy with promising potential for future clinical translation.     

Near‐Infrared Upconversion Mesoporous Cerium Oxide Hollow Biophotocatalyst for Concurrent pH‐/H2O2‐Responsive O2‐Evolving Synergetic Cancer Therapy

Tumor hypoxia is typically presented in the central region of solid tumors, which is mainly caused by an inadequate blood flow and oxygen supply. In the conventional treatment of hypoxic human tumors, not only the oxygen‐dependent photodynamic therapy (PDT), but also antitumor drug‐based chemotherapy, is considerably limited. The use of direct oxygen delivering approach with oxygen‐dependent PDT or chemotherapy may potentiate the reactive oxygen species (ROS)‐mediated cytotoxicity of the drug toward normal tissues. Herein, a synergetic one‐for‐all mesoporous cerium oxide upconversion biophotocatalyst is developed to achieve intratumorally endogenous H₂O₂‐responsive self‐sufficiency of O₂ and near‐infrared light controlled PDT simultaneously for overcoming hypoxia cancer. Furthermore, the sufficient O₂ plays an important role in overcoming the chemotherapeutic drug‐resistant cancer caused by hypoxia, therefore inducing tumor cell apoptosis significantly.     

Toxic Reactive Oxygen Species Enhanced Synergistic Combination Therapy by Self‐Assembled Metal‐Phenolic Network Nanoparticles

Engineering functional nanomaterials with high therapeutic efficacy and minimum side effects has increasingly become a promising strategy for cancer treatment. Herein, a reactive oxygen species (ROS) enhanced combination chemotherapy platform is designed via a biocompatible metal‐polyphenol networks self‐assembly process by encapsulating doxorubicin (DOX) and platinum prodrugs in nanoparticles. Both DOX and platinum drugs can activate nicotinamide adenine dinucleotide phosphate oxidases, generating superoxide radicals (O₂^??). The superoxide dismutase‐like activity of polyphenols can catalyze H₂O₂ generation from O₂^??. Finally, the highly toxic HO^? free radicals are generated by a Fenton reaction. The ROS HO^? can synergize the chemotherapy by a cascade of bioreactions. Positron emission tomography imaging of ⁸⁹Zr‐labeled as‐prepared DOX@Pt prodrug Fe³⁺ nanoparticles (DPPF NPs) shows prolonged blood circulation and high tumor accumulation. Furthermore, the DPPF NPs can effectively inhibit tumor growth and reduce the side effects of anticancer drugs. This study establishes a novel ROS promoted synergistic nanomedicine platform for cancer therapy.     

Flexible,Flame‐Resistant,and Dendrite‐Impermeable Gel‐Polymer Electrolyte for Li–O2/Air Batteries Workable Under Hurdle Conditions

Gel‐polymer electrolytes are considered as a promising candidate for replacing the liquid electrolytes to address the safety concerns in Li–O₂/air batteries. In this work, by taking advantage of the hydrogen bond between thermoplastic polyurethane and aerogel SiO₂ in gel polymer, a highly crosslinked quasi‐solid electrolyte (FST‐GPE) with multifeatures of high ionic conductivity, high mechanical flexibility, favorable flame resistance, and excellent Li dendrite impermeability is developed. The resulting gel‐polymer Li–O₂/air batteries possess high reaction kinetics and stabilities due to the unique electrode–electrolyte interface and fast O₂ diffusion in cathode, which can achieve up to 250 discharge–charge cycles (over 1000 h) in oxygen gas. Under ambient air atmosphere, excellent performances are observed for coin‐type cells over 20 days and for prototype cells working under extreme bending conditions. Moreover, the FST‐GPE electrolyte also exhibits durability to protect against fire, dendritic Li, and H₂O attack, demonstrating great potential for the design of practical Li–O₂/air batteries.     

Dynamic Antifouling of Catalytic Pores Armed with Oxygenic Polyoxometalates

A novel stimuli‐responsive strategy against the irreversible fouling of porous materials and surfaces is presented herein. This is based on the molecular design of catalytic pore walls that foster a chemo‐mechanical, self‐cleaning behavior under neutral pH and mild conditions of pressure and temperature. This approach builds on bioinspired remediation mechanisms involving natural catalase enzymes for H₂O₂ dismutation and endogenous oxygen production. It is thus demonstrated that a very efficient antifouling activity is observed when the material pores are armed with oxygen evolving catalysts that are known to liberate nascent oxygen gas when exposed to H₂O₂ as chemical trigger. To this aim, the catalase‐like behavior of the tetra‐ruthenium substituted polyoxometalate (Ru₄(SiW₁₀)₂), has been exploited for in‐pore oxygen evolution so to induce an active fluid mixing and the displacement of foulant particles. The present study includes the fabrication of hybrid polymeric films with porous architecture embedding Ru₄(SiW₁₀)₂ as artificial catalase to guarantee the material self‐defense against pore occlusion and oxidative damage with aqueous H₂O₂ as mild chemical effector. The self‐catalytic “in‐pore” remediation is readily applied to various materials/interfaces with porous texture and high surface area with the aim to provide long‐lasting functional performances.     

Reversible Chemical Tuning of Charge Carriers for Enhanced Photoelectrochemical Conversion and Probing of Living Cells

A facile, solution method for reversible tuning of oxygen vacancies inside TiO₂ nanowires, in which the reducing treatment of TiO₂ by NaBH₄ leads to 2.4‐fold increase of photocurrent density, compared to pristine TiO₂ nanowires, is reported. Subsequent oxidizing treatment using KMnO₄ or annealing in air can reset the photocurrent density to the original values. The incident photo‐to‐current conversion efficiency measurement exhibits that the reduced TiO₂ nanowires present both enhanced photoactivity in both UV and visible regions. Density functional theory calculations reveal that the oxygen vacancies in the reduced TiO₂ cause defect states in the band structure and result in enhanced carrier density and conductivity. In addition, the enhanced solar energy‐driven photoelectrochemical conversion allows real‐time, sensitive chemical probing of living cells that are directly grown on the TiO₂ nanowire photoanodes. As proofs‐of‐concept, after functionalized with horseradish peroxidase (HRP) on the surface, the reduced TiO₂ NWs demonstrate sensitive, real‐time monitoring of the H₂O₂ levels in several distinctive living cell lines, with the lowest detectable H₂O₂ concentration of 7.7 nm . This reversible tuning of oxygen vacancies suggests a facile means for transition metal oxides, with enhanced photoconversion activity and electrochemical sensitivity.     

A Cascade Enzyme System Integrating Peroxidase Mimic with Catalase for Linear Range Expansion of H2O2 Assay: A Mechanism and Application Study

Peroxidase (POD) Nanozyme-based hydrogen peroxide (H₂O₂) detection is popular, but hardly adapt to high concentration of H₂O₂ owing to narrow linear range (LR) and low LR maximum. Here, a solution of combining POD and catalase (CAT) is raised to expand the LR of H₂O₂ assay via decomposing part of H₂O₂. As a proof of concept, a cascade enzyme system (rGRC) is constructed by integrating ruthenium nanoparticles (RuNPs), CAT and graphene together. The rGRC-based sensor does perform an expanded LR and higher LR maximum for H₂O₂ detection. Meanwhile, it is confirmed that LR expansion is closely associated with apparent K_m of rGRC, which is determined by the relative enzyme activity between CAT and POD both in theory and in experiment. At last, rGRC is successfully used to detect high concentration of H₂O₂ (up to 10 mm ) in contact lens care solution, which performs higher assay accuracy (close to 100% recovery at 10 mm of H₂O₂) than traditional POD nanozymes. This study brings up a kind of POD/CAT cascade enzyme system and provides a new concept for accurate and facile H₂O₂ detection. Additionally, it replenishes a new enzyme-substrate model of achieving the same pattern with competitive inhibition in enzyme reactions.     

Self-Propelled Ultrasmall AuNPs-Tannic Acid Hybrid Nanozyme with ROS-Scavenging and Anti-Inflammatory Activity for Drug-Induced Liver Injury Alleviation

Developing nanomedicines with superior reactive oxygen species (ROS) scavenging capability has emerged as a promising strategy in treating ROS-related diseases, for example, drug-induced liver injury. However, designing nanoscavengers with the self-propelling ability to scavenge ROS actively remains challenging. Here, a self-propelled silica-supported ultrasmall gold nanoparticles-tannic acid hybrid nanozyme (SAuPTB) is designed that can effectively alleviate acetaminophen (APAP)-induced liver injury by scavenging excessive ROS and regulating inflammation. SAuPTB exhibits multienzyme activity and displays significantly enhanced diffusion under hydrogen peroxide (H₂O₂). This in vitro research shows that SAuPTB can effectively eliminate ROS, increasing the viability of H₂O₂-stimulated cells and reducing the cytotoxicity of APAP/H₂O₂-treated AML12 cells. The in vivo studies show that SAuPTB can accumulate at inflammatory sites in mouse liver, resulting in the decrease of alanine aminotransferase, aspartate aminotransferase, and ROS, reduction in pro-inflammatory cytokines and chemokines, hence reduced hepatocyte necrosis, liver injury, and mortality. Furthermore, SAuPTB activates the nuclear erythroid 2-related factor 2 pathway to upregulate antioxidative genes and reduce oxidative stress. Finally, the liver shows decreased high mobility group box 1 and F4/80⁺ macrophages, suggesting an anti-inflammatory response. This work provides a novel design strategy of nanozymes for ROS-related disease treatment.     

Enhanced Chemodynamic Therapy Mediated by a Tumor-Specific Catalyst in Synergy with Mitophagy Inhibition Improves the Efficacy for Endometrial Cancer

Chemodynamic therapy (CDT) relies on the tumor microenvironment (e.g., high H₂O₂ level) responsive Fenton-like reactions to produce hydroxyl radicals (·OH) against tumors. However, endogenous H₂O₂ is insufficient for effective chemodynamic responses. An NAD(P)H: quinone oxidoreductase 1 (NQO1)^high catalase (CAT)^low therapeutic window for the use of NQO1 bioactive drug β-lapachone (β-Lap) is first identified in endometrial cancer (EC). Accompanied by NADH depletion, NQO1 catalyzes β-Lap to produce excess H₂O₂ and initiate oxidative stress, which selectively suppress NQO1^high EC cell proliferation, induce DNA double-strand breaks, and promote apoptosis. Moreover, shRNA-mediated NQO1 knockdown or dicoumarol rescues NQO1^high EC cells from β-Lap-induced cytotoxicity. Arginine-glycine-aspartic acid (RGD)-functionalized iron-based metal-organic frameworks (MOF(Fe)) further promote the conversion of the accumulated H₂O₂ into highly oxidative ·OH, which in turn, exacerbates the oxidative damage to RGD-positive target cells. Furthermore, mitophagy inhibition by Mdivi-1 blocks a powerful antioxidant defense approach, ultimately ensuring the anti-tumor efficacy of stepwise-amplified reactive oxygen species signals. The tumor growth inhibition rate (TGI) is about 85.92%. However, the TGI of MOF(Fe)-based synergistic antitumor therapy decreases to only 50.46% in NQO1-deficient KLE tumors. Tumor-specific chemotherapy and CDT-triggered therapeutic modality present unprecedented therapeutic benefits in treating NQO1^high EC.     

Thread‐Like Radical‐Polymerization via Autonomously Propelled (TRAP) Bots

Micromotor‐mediated synthesis of thread‐like hydrogel microstructures in an aqueous environment is presented. The study utilizes a catalytic micromotor assembly (owing to the presence of a Pt layer), with an on‐board chemical reservoir (i.e., polymerization mixture), toward thread‐like radical‐polymerization via autonomously propelled bots (i.e., TRAP bots). Synergistic coupling of catalytically active Pt layer, together with radical initiators (H₂O₂ and FeCl₃ (III)), and PEGDA monomers preloaded into the TRAP bot, results in the polymerization of monomeric units into elongated thread‐like hydrogel polymers coupled with self‐propulsion. Interestingly, polymer generation via TRAP bots can also be triggered in the absence of hydrogen peroxide for cellular/biomedical application. The resulting polymeric hydrogel microstructures are able to entrap living cells (NIH 3T3 fibroblast cells), and are easily separable via a centrifugation or magnetic separation (owing to the presence of a Ni layer). The cellular biocompatibility of TRAP bots is established via a LIVE/DEAD assay and MTS cell proliferation assay (7 days observation). This is the first study demonstrating real‐time in situ hydrogel polymerization via an artificial microswimmer, capable of enmeshing biotic/abiotic microobjects in its reaction environment, and lays a strong foundation for advanced applications in cell/tissue engineering, drug delivery, and cleaner technologies.     

Self‐Supplying O2 through the Catalase‐Like Activity of Gold Nanoclusters for Photodynamic Therapy against Hypoxic Cancer Cells

Photodynamic therapy (PDT) typically involves oxygen (O₂) consumption and therefore suffers from greatly limited anticancer therapeutic efficacy in tumor hypoxia. Here, it is reported for the first time that amine‐terminated, PAMAM dendrimer‐encapsulated gold nanoclusters (AuNCs‐NH₂) can produce O₂ for PDT via their intrinsic catalase‐like activity. The AuNCs‐NH₂ not only show optimum H₂O₂ consumption via the catalase‐like activity over the physiological pH range (i.e., pH 4.8–7.4), but also extend such activity to acidic conditions. The possible mechanism is deduced from that the enriched tertiary amines of dendrimers are easily protonated in acidic solutions to facilitate the preadsorption of OH on the metal surface, thereby favorably triggering the catalase‐like reaction. By taking advantage of the exciting feature on AuNCs‐NH₂, the possibility to supply O₂ via the catalase‐like activity of AuNCs‐NH₂ for PDT against hypoxia of cancer cells was further studied. This proof‐of‐concept study provides a simple way to combine current O₂‐dependent cancer therapy of PDT to overcome cancer cell hypoxia, thus achieving more effective anticancer treatments.     

Effect of phosphoric acid on the performance of low antimony grid of Pb‐acid cell under constant current charging and discharging

Effect of phosphoric acid on the performance of Pb‐1.7%Sb grid of lead‐acid cell is studied in 5 M H₂SO₄ by cyclic galvanostatic polarization and impedance spectroscopy. An increase in capacitance to a maximum is recorded during the initial stages of the electro‐reduction of PbO₂ into Pb(II) compounds and attributed to concurrent compositional and dimensional changes. These changes include removal of O₂ bubbles, insertion of large amounts of H₂SO₄ and H₂O. Efficiency of PbO₂ formation decreases, while its rate of self‐discharge increases with increasing the charging current and in the presence of H₃PO₄. The charge capacity increases with increasing the discharging current due to the decrease in the self‐discharge. The charge capacity is lower in the presence of H₃PO₄. On increasing the cycle number, the corrodibility of the grid increases, because more layers of the surface Pb are involved in the self‐discharge. H₃PO₄ significantly retards the effect of cycle number.     

Bioinspired Superhydrophobic Fe3O4@Polydopamine@Ag Hybrid Nanoparticles for Liquid Marble and Oil Spill

Fe₃O₄ nanoparticles (NPs) with Ag NPs evenly distributed on the surface are fabricated by using polydopamine (PDA) as the intermediate layer. Silanization and thiol chemistry are used to firmly combine the Fe₃O₄@ PDA core and outer surface Ag NPs. The spherical and hybrid nanoparticles are termed Fe₃O₄@PDA@Ag NPs, which possess a core–shell and hierarchical structure. After surface modification with 1H,1H,2H,2H‐perfluorodecanethiol, the hybrid Fe₃O₄@PDA@Ag NPs become highly hydrophobic. Slight rolling of a water droplet on the as‐prepared NPs causes the formation of a “liquid marble”, which is capable of performing remote actuation on various solid surfaces, such as glass sheet, paper, plastic, textile, and ceramic, and at the liquid–air interface using a permanent magnet. Liquid marbles with self‐assembled NPs on the liquid surface have potential to act as a miniaturized reactor for manipulation of inner liquid droplet with high positioning precision. In addition, the Fe₃O₄@PDA@Ag NPs are multifunctional and can be applied for oil/water separation and antibacterial purpose.     

Sodium‐Oxygen Batteries: A Comparative Review from Chemical and Electrochemical Fundamentals to Future Perspective

Alkali metal‐oxygen (Li‐O₂, Na‐O₂) batteries have attracted a great deal of attention recently due to their high theoretical energy densities, comparable to gasoline, making them attractive candidates for application in electrical vehicles. However, the limited cycling life and low energy efficiency (high charging overpotential) of these cells hinder their commercialization. The Li‐O₂ battery system has been extensively studied in this regard during the past decade. Compared to the numerous reports of Li‐O₂ batteries, the research on Na‐O₂ batteries is still in its infancy. Although, Na‐O₂ batteries show a number of attractive properties such as low charging overpotential and high round‐trip energy efficiency, their cycling life is currently limited to a few tens of cycles. Therefore, understanding the chemistry behind Na‐O₂ cells is critical towards enhancing their performance and advancing their development. Chemical and electrochemical reactions of Na‐O₂ batteries are reviewed and compared with those of Li‐O₂ batteries in the present review, as well as recent works on the chemical composition and morphology of the discharge products in these batteries. Furthermore, the determining kinetics factors for controlling the chemical composition of the discharge products in Na‐O₂ cells are discussed and the potential research directions toward improving Na‐O₂ cells are proposed.