A Sequentially Activated Probe for Imaging of Superoxide Anion and Peroxynitrite in PC12 Cells under Oxidative Stress.

Superoxide anion (O2·-) and peroxynitrite (ONOO-), two important oxidants under oxidative stress, coexist in complex cell and organism systems, playing crucial roles in various physiological and pathological processes, particularly in neurodegenerative diseases. Despite the absence of robust molecular tools capable of simultaneously visualizing O2·- and ONOO- in biosystems, the relationship between these two species remains understudied. Herein, we present sequentially activated fluorescent probe, DHX-SP, which exhibits exceptional selectivity and sensitivity toward O2·- and ONOO-. This probe enables precise imaging of these species in living PC12 cells under oxidative stress conditions using distinct fluorescence signal combinations. Furthermore, the probe DHX-SP has the ability to visualize changes in O2·- and ONOO- levels during ferroptosis of PC12 cells and in the Parkinson's disease model. These findings establish a connection between the crosstalk of the phosphorus group of O2·- and ONOO- in PC12 cells under oxidative stress.

Low-Solvent-Coordination Solvation Structure for Lithium-Metal Batteries via Electric Dipole-Dipole Interaction.

Unveiling inherent interactions among solvents, Li+ ions, and anions are crucial in dictating solvation-desolvation kinetics at the electrode/electrolyte interface. Developing an electrolyte with a low ion-transport barrier and minimal solvent coordination in its interfacial solvation structure is essential for forming an anion-derived solid-electrolyte interface, a key component for high-performance Li-metal batteries. In this study, we harness electric dipole-dipole synergistic interactions to formulate an electrolyte with significantly reduced interfacial solvent coordination. Operando characterization and theoretical analysis reveal that 2-fluoropyridine (FPy) with high dipole preferentially adsorbs onto the Li metal surface. The adsorbed FPy molecule squeezes succinonitrile in the primary solvation sheath through steric hindrance, leading to the formation of an inorganic-rich interphase. Consequently, the introduction of FPy enhances the reversible capacity of the LiCoO2||Li cell, which maintains a capacity of 143 mAh g-1 after 500 cycles at a 1C rate. Moreover, the cycle life of LiCoO2 batteries with a limited supply of lithium extends from 120 cycles to over 200 cycles. These findings offer a strategy that can be applied broadly to design interfacial solvation structures for various metal-ion/metal-based batteries.

Light Enables the Cathodic Interface Reaction Reversibility in Solid-State Lithium-Oxygen Batteries.

Limited triple-phase boundaries arising from the accumulation of solid discharge product(s) in solid-state cathodes (SSCs) pose a challenge to high-property solid-state lithium-oxygen batteries (SSLOBs). Light-assisted SSLOBs have been gradually explored as an ingenious system; however, the fundamental mechanisms of the SSCs interface behavior remain unclear. Here, we discovered that light assistance can enhance the fast inner-sphere charge transfer in SSCs and regulate the discharge products with spherical particles generated via the surface growth model. Moreover, the high photoelectron excitation and transportation capabilities of SSCs can retard cathodic catalytic decay by avoiding structural degradation of the cathode with a reduced charge voltage. The light-induced SSLOBs exhibited excellent stability (170 cycles) with a low discharge-charge polarization overpotential (0.27 V). Furthermore, transparent SSLOBs with exceptional flexibility, mechanical stability, and multiform shapes were fabricated for theory-to-practical applications in sunlight-induced batteries. Our study opens new opportunities for the introduction of solar energy into energy storage systems.

Dihydroxanthene-Based Near-infrared Fluorescent Probes for Monitoring Mitochondrial Viscosity in Living Cells and Mice.

Aberrant mitochondrial viscosity is closely associated with many diseases and cellular malfunctions. Thus, the development of reliable methods for monitoring mitochondrial viscosity variations has attracted considerable attention. Herein, through stepwise structural modulation of the dihydroxanthene fluorophore (DHX), we developed three NIR fluorescent probes, named DHX-V-1-3, for detecting mitochondrial viscosity. Among them, DHX-V-3 displayed the highest signal-to-noise ratio (67-fold) for viscosity with outstanding selectivity and showed excellent mitochondria targeting and immobilization ability. At the cellular level, the DHX-V-3 probe was successfully applied to image the mitochondrial viscosity in live cells upon treatment with lipopolysaccharide (LPS) or nystatin. Moreover, benefiting from its NIR emission and the increased depth of tissue imaging, DHX-V-3 demonstrated the ability to visualize the increased viscosity in LPS-treated mice.

Rational Design of MMP-Independent Near-Infrared Fluorescent Probes for Accurately Monitoring Mitochondrial Viscosity.

Mitochondrial viscosity affects metabolite diffusion and mitochondrial metabolism and is associated with many diseases. However, the accuracy of mitochondria-targeting fluorescent probes in measuring viscosity is unsatisfactory because these probes can diffuse from mitochondria during mitophagy with a decreased mitochondrial membrane potential (MMP). To avoid this problem, by incorporating different alkyl side chains into dihydroxanthene fluorophores (denoted as DHX), we developed six near-infrared (NIR) probes for the accurate detection of mitochondrial viscosity, and the sensitivity to viscosity and the mitochondrial targeting and anchoring capability of these probes increased by increasing the alkyl chain length. Among them, DHX-V-C12 had a highly selective response to viscosity variations with minimum interference from polarity, pH, and other biologically relevant species. Furthermore, DHX-V-C12 was used to monitor the mitochondrial viscosity changes of HeLa cells treated by ionophores (nystatin, monensin) or under starvation conditions. We hope that this mitochondrial targeting and anchoring strategy based on increasing the alkyl chain length will be a general strategy for the accurate detection of mitochondrial analytes, enabling the accurate study of mitochondrial functions.

Architecting FeNx on High Graphitization Carbon for High-Performance Oxygen Reduction by Regulating d-Band Center.

Fe single atoms and N co-doped carbon nanomaterials (Fe-N-C) are the most promising oxygen reduction reaction (ORR) catalysts to replace platinum group metals. However, high-activity Fe single-atom catalysts suffer from poor stability owing to the low graphitization degree. Here, an effective phase-transition strategy is reported to enhance the stability of Fe-N-C catalysts by inducing increased degree of graphitization and incorporation of Fe nanoparticles encapsulated by graphitic carbon layer without sacrificing activity. Remarkably, the resulted Fe@Fe-N-C catalysts achieved excellent ORR activity (E1/2  = 0.829 V) and stability (19 mV loss after 30K cycles) in acid media. Density functional theory (DFT) calculations agree with experimental phenomena that additional Fe nanoparticles not only favor to the activation of O2 by tailoring d-band center position but also inhibit the demetallization of Fe active center from FeN4 sites. This work provides a new insight into the rational design of highly efficient and durable Fe-N-C catalysts for ORR.

Tailoring the p-Band Center of NS Pair for Accelerating High-Performance Lithium-Oxygen Battery.

The local coordination environment of catalytical moieties directly determines the performance of electrochemical energy storage and conversion devices, such as Li-O2 batteries (LOBs) cathode. However, understanding how the coordinative structure affects the performance, especially for non-metal system, is still insufficient. Herein, a strategy that introduces S-anion to tailor the electronic structure of nitrogen-carbon catalyst (SNC) is proposed to improve the LOBs performance. This study unveils that the introduced S-anion effectively manipulates the p-band center of pyridinic-N moiety, substantially reducing the battery overpotential by accelerating the generation and decomposition of intermediate products Li1-3 O4 . The lower adsorption energy of discharging product Li2 O2 on NS pair accounts for the long-term cyclic stability by exposing the high active area under operation condition. This work demonstrates an encouraging strategy to enhance LOBs performance by modulating the p-band center on non-metal active sites.

A Near-Infrared Probe for Specific Imaging of Lipid Droplets in Living Cells.

Lipid droplets (LDs) are involved in various physiological processes and associated with cancer development, and are regarded as a potential tumor marker for cancer diagnosis. Monitoring LDs is of prior importance to understand their involvement in biological mechanisms and the early detection of cancers. Highly sensitive and specific noninvasive fluorescent probes are particularly desirable for imaging LDs and cancer diagnosis. Herein, according to the high-viscosity and low-polarity microenvironment in LDs, we developed four easily prepared LDs-specific probes based on noncharged merocyanines. Among them, LD-1 absorbs and emits in the near-infrared (NIR) region with a large Stokes shift. Importantly, LD-1 displayed high sensitivity to high viscosity and low polarity, which allowed it to show high LDs-targeting ability. In cell imaging, LD-1 successfully probed the changes in LDs in the presence of oleic acid or during ferroptosis and was used to distinguish cancer cells from normal cells.

Single-Atom Tailored Hierarchical Transition Metal Oxide Nanocages for Efficient Lithium Storage.

Mitigating the mechanical degradation and enhancing the ionic/electronic conductivity are critical but challengeable issues toward improving electrochemical performance of conversion-type anodes in rechargeable batteries. Herein, these challenges are addressed by constructing interconnected 3D hierarchically porous structure synergistic with Nb single atom modulation within a Co3 O4 nanocage (3DH-Co3 O4 @Nb). Such a hierarchical-structure nanocage affords several fantastic merits such as rapid ion migration and enough inner space for alleviating volume variation induced by intragrain stress and optimized stability of the solid-electrolyte interface. Particularly, experimental studies in combination with theoretical analysis verify that the introduction of Nb into the Co3 O4 lattice not only improves the electron conductivity, but also accelerates the surface/near-surface reactions defined as pesudocapacitance behavior. Dynamic behavior reveals that the ensemble design shows huge potential for fast and large lithium storage. These features endow 3DH-Co3 O4 @Nb with remarkable battery performance, delivering ≈740 mA h g-1 after ultra-long cycling of 1000 times under a high current density of 5 A g-1 . Importantly, the assembled 3DH-Co3 O4 @Nb//LiCoO2 pouch cell also presents a long-lived cycle performance with only ≈0.059% capacity decay per cycle, inspiring the design of electrode materials from both the nanostructure and atomic level toward practical applications.

Selectively Coupling Ru Single Atoms to PtNi Concavities for High-Performance Methanol Oxidation via d-Band Center Regulation.

Single atom tailored metal nanoparticles represent a new type of catalysts. Herein, we demonstrate a single atom-cavity coupling strategy to regulate performance of single atom tailored nano-catalysts. Selective atomic layer deposition (ALD) was conducted to deposit Ru single atoms on the surface concavities of PtNi nanoparticles (Ru-ca-PtNi). Ru-ca-PtNi exhibits a record-high activity for methanol oxidation reaction (MOR) with 2.01 A mg-1 Pt . Also, Ru-ca-PtNi showcases a significant durability with only 16 % activity loss. Operando electrochemical Fourier transform infrared spectroscopy (FTIR) and theoretical calculations demonstrate Ru single atoms coupled to cavities accelerate the CO removal by regulating d-band center position. Further, the high diffusion barrier of Ru single atoms in concavities accounts for excellent stability. The developed Ru-ca-PtNi via single atom-cavity coupling opens an encouraging pathway to design highly efficient single atom-based (electro)catalysts.

Unveiling the Nature of Pt Single-Atom Catalyst during Electrocatalytic Hydrogen Evolution and Oxygen Reduction Reactions.

Single-atom catalysts (SACs) have attracted significant attention due to their superior catalytic activity and selectivity. However, the nature of active sites of SACs under realistic reaction conditions is ambiguous. In this work, high loading Pt single atoms on graphitic carbon nitride (g-C3 N4 )-derived N-doped carbon nanosheets (Pt1 /NCNS) is achieved through atomic layer deposition. Operando X-ray absorption spectroscopy (XAS) is performed on Pt single atoms and nanoparticles (NPs) in both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The operando results indicate that the total unoccupied density of states of Pt 5d orbitals of Pt1 atoms is higher than that of Pt NPs under HER condition, and that a stable Pt oxide is formed during ORR on Pt1 /NCNS, which may suppress the adsorption and activation of O2 . This work unveils the nature of Pt single atoms under realistic HER and ORR conditions, providing a deeper understanding for designing advanced SACs.

Shack-Hartmann wavefront sensing using spatial-temporal data from an event-based image sensor.

An event-based image sensor works dramatically differently from the conventional frame-based image sensors in a way that it only responds to local brightness changes whereas its counterparts' output is a linear representation of the illumination over a fixed exposure time. The output of an event-based image sensor therefore is an asynchronous stream of spatial-temporal events data tagged with the location, timestamp and polarity of the triggered events. Compared to traditional frame-based image sensors, event-based image sensors have advantages of high temporal resolution, low latency, high dynamic range and low power consumption. Although event-based image sensors have been used in many computer vision, navigation and even space situation awareness applications, little work has been done to explore their applicability in the field of wavefront sensing. In this work, we present the integration of an event camera in a Shack-Hartmann wavefront sensor and the usage of event data to determine spot displacement and wavefront estimation. We show that it can achieve the same functionality but with substantial speed and can operate in extremely low light conditions. This makes an event-based Shack-Hartmann wavefront sensor a preferable choice for adaptive optics systems where light budget is limited or high bandwidth is required.

Polyvinylpyrrolidone-Coordinated Single-Site Platinum Catalyst Exhibits High Activity for Hydrogen Evolution Reaction.

The essence of developing a Pt-based single-atom catalyst (SAC) for hydrogen evolution reaction (HER) is the preparation of well-defined and stable single Pt sites with desired electrocatalytic efficacy. Herein, we report a facile approach to generate uniformly dispersed Pt sites with outstanding HER performance via a photochemical reduction method using polyvinylpyrrolidone (PVP) molecules as the key additive to significantly simplify the synthesis and enhance the catalytic performance. The as-prepared catalyst displays remarkable kinetic activities (20 times higher current density than the commercially available Pt/C) with excellent stability (76.3 % of its initial activity after 5000 cycles) for HER. EXAFS measurements and DFT calculations demonstrate a synergetic effect, where the PVP ligands and the support together modulate the electronic structure of the Pt atoms, which optimize the hydrogen adsorption energy, resulting in a considerably improved HER activity.

Dicyanoisophorone-Based Near-Infrared-Emission Fluorescent Probe for Detecting NAD(P)H in Living Cells and in Vivo.

NADH and NADPH are ubiquitous coenzymes in all living cells that play vital roles in numerous redox reactions in cellular energy metabolism. To accurately detect the distribution and dynamic changes of NAD(P)H under physiological conditions is essential for understanding their biological functions and pathological roles. In this work, we developed a near-infrared (NIR)-emission fluorescent small-molecule probe (DCI-MQ) composed of a dicyanoisophorone chromophore conjugated to a quinolinium moiety for in vivo NAD(P)H detection. DCI-MQ has the advantages of high water solubility, a rapid response, extraordinary selectivity, great sensitivity (a detection limit of 12 nM), low cytotoxicity, and NIR emission (660 nm) in response to NAD(P)H. Moreover, the probe DCI-MQ was successfully applied for the detection and imaging of endogenous NAD(P)H in both living cells and tumor-bearing mice, which provides an effective tool for the study of NAD(P)H-related physiological and pathological processes.

Au-Se-Bond-Based Nanoprobe for Imaging MMP-2 in Tumor Cells under a High-Thiol Environment.

The gold nanosensors based on the Au-S bond have been widely applied to biochemical detections. However, signal distortion caused by biothiols has been seldom mentioned and urgently needs to be solved. Herein, we designed a novel but easily assembled gold nanoprobe by coupling a selenol-modified peptide with FITC onto the gold nanoparticle's surface via an Au-Se bond for fluorescence imaging of a tumor marker matrix, metalloproteinases 2 (MMP-2). Compared to the Au-S probes, the Au-Se probes display high thermal stability and a very good anti-interference ability toward glutathione under simulated physiological conditions. More importantly, the Au-Se nanoprobe exhibits a high-fidelity fluorescent signal toward MMP-2, effectively avoiding interference caused by high levels of thiol compounds in vivo. In addition, in vivo experiments further proved that no significant signal intensity change for the tumor cells treated by the Au-Se probes was observed before and after eliminating glutathione. Hence, we believe such Au-Se probes with in vivo glutathione interfering resistance offer new routes and perspectives in biology and medicine in the future.

Simultaneous Detection of Mitochondrial Hydrogen Selenide and Superoxide Anion in HepG2 Cells under Hypoxic Conditions.

Previous studies proposed that sodium selenite (Na2SeO3) was reduced to hydrogen selenide (H2Se) and that H2Se subsequently reacted with oxygen to generate superoxide anion (O2•-), resulting in tumor cell oxidative stress and apoptosis. However, under the hypoxic conditions of a solid tumor, the anticancer mechanism of sodium selenite remains unclear. To reveal the exact anticancer mechanism of selenite in the real tumor microenvironment, we developed a mitochondria-targeting fluorescent nanosensor, Mito-N-D-MSN, which was fabricated from mesoporous silica nanoparticles (MSNs) loaded with two small-molecule fluorescent probes and a triphenylphosphonium ion as a mitochondria-targeting moiety. With Mito-N-D-MSN, the fluctuations in the contents of mitochondrial hydrogen selenide (H2Se) and superoxide anion (O2•-) in HepG2 cells induced by Na2SeO3 were investigated in detail under normoxic and hypoxic conditions. The results showed that the mitochondrial H2Se content increased gradually, while the O2•- content remained unchanged in HepG2 cells under hypoxic conditions, which indicated that the anticancer mechanism of selenite involves nonoxidative stress in the real tumor microenvironment.

Cyclic Regulation of the Sulfilimine Bond in Peptides and NC1 Hexamers via the HOBr/H2Se Conjugated System.

The sulfilimine bond (-S═N-), found in the collagen IV scaffold, significantly stabilizes the architecture via the formation of sulfilimine cross-links. However, precisely governing the formation and breakup process of the sulfilimine bond in living organisms for better life functions still remains a challenge. Hence, we established a new way to regulate the breaking and formation of the sulfilimine bond through hydrogen selenide (H2Se) and hypobromous acid (HOBr), which can be easily controlled at simulated physiological conditions. This novel strategy provides a circulation regulation system to modulate the sulfilimine bond in peptides and NC1 hexamers, which can offer a substantial system for further study of the physiological function of collagen IV.

Avoiding Thiol Compound Interference: A Nanoplatform Based on High-Fidelity Au-Se Bonds for Biological Applications.

Gold nanoparticles (Au NPs) assembled through Au-S covalent bonds have been widely used in biomolecule-sensing technologies. However, during the process, detection distortions caused by high levels of thiol compounds can still significantly influence the result and this problem has not really been solved. Based on the higher stability of Au-Se bonds compared to Au-S bonds, we prepared selenol-modified Au NPs as an Au-Se nanoplatform (NPF). Compared with the Au-S NPF, the Au-Se NPF exhibits excellent anti-interference properties in the presence of millimolar levels of glutathione (GSH). Such an Au-Se NPF that can effectively avoid detection distortions caused by high levels of thiols thus offers a new perspective in future nanomaterial design, as well as a novel platform with higher stability and selectivity for the in vivo application of chemical sensing and clinical therapies.

High-Quantum-Yield Mitochondria-Targeting Near-Infrared Fluorescent Probe for Imaging Native Hypobromous Acid in Living Cells and in Vivo.

The discovery that hypobromous acid (HOBr) can regulate the activity of collagen IV has attracted great attention. However, HOBr as an important reactive small molecule has hardly ever been studied using a detection method suitable for organisms. Herein, a high-quantum-yield mitochondria-targeting near-infrared (NIR) fluorescent probe for HOBr, RhSN-mito, was designed. RhSN-mito was easily obtained by the Suzuki cross-coupling reaction. The test results show that RhSN-mito can rapidly respond to HOBr with ultrasensitivity and high selectivity. The achievement of ultrasensitivity lies in the high signal-to-noise ratio and the highest fluorescence quantum yield of the reaction product (ΦF = 0.68) in the near-infrared region, as far as we know. RhSN-mito is successfully applied to image native HOBr in mitochondria of HepG2 cells and zebrafish. Thus, RhSN-mito is a powerful tool for detecting native HOBr in vivo and is expected to provide a method to further study the physiological and pathological functions related to HOBr.

Highly Selective Fluorescent Probe for Imaging H2Se in Living Cells and in Vivo Based on the Disulfide Bond.

Hydrogen selenide (H2Se) is an important metabolite of dietary Se compounds and has been implicated in various pathological and physiological processes. The development of highly sensitive and selective methods for the sensing of H2Se is therefore very important. Herein, we developed a fluorescent probe (hemicyanine (Hcy)-H2Se) for detecting H2Se based on a new H2Se-specific receptor unit, 1,2-dithiane-4,5-diol. Hcy-H2Se showed high selectivity toward H2Se over thiols (RSH), hydrogen sulfide (H2S), and selenocysteine (Sec) and was further exploited for the fluorescence imaging of H2Se both in living cells and in vivo. Furthermore, with the aid of Hcy-H2Se, we demonstrated that H2Se can be generated and gradually accumulated in HepG2 cells under hypoxic conditions and in the solid tumor after treatment with Na2SeO3.