Coordinate Covalent Research Articles

Chemical Energy Lights Up Europium‐Based Ultra‐bright Afterglow for Bioanalysis Application

Photochemical afterglow materials are gaining great attention for the property to continuously emit light after the excitation source is removed. However, their limited luminescence quantum yield (QY) and brightness hinder the use in biological applications. In this study, we introduce a novel photochemical afterglow system that combines a newly designed photoenergy cache unit (PCU) with an emitter through coordination covalent bonds. The PCU boasts a dark state to significantly emit photons only through chemiexcitation in the process of photochemical reactions, facilitating direct energy transfer to the emitter and resulting in bright afterglow. The related mechanisms further guided us to achieve the highest reported afterglow luminescence quantum yield of 27.5%. The system can be encapsulated and dispersed in aqueous solutions for in vivo bioimaging in living mice under mild and simple conditions (low concentration, low excitation power, short excitation time, short exposure time), and also for in vitro diagnostic through lateral flow immunoassay, enabling the highly sensitive detection of the inflammatory biomarker serum amyloid A (SAA) and demonstrating excellent correlation with clinical test results. This study offers new insights into enhancing luminescence QY and brightness of afterglow, highlighting the potential of such systems for further biomedical applications.

High Performance of Cs2AgBiBr6 Perovskite-based Photodetectors by Adding DEAC.

Perovskite-based photodetectors (PDs) are broadly utilized in optical communication, non-destructive testing, and smart wearable devices due to their ability to convert light into electrical signals. However, toxicity and instability hold back their mass production and commercialization. The lead-free Cs2AgBiBr6 double perovskite film, promised to be an alternative, is fabricated by electrophoretic deposition (EPD), which compromises film quality. Herein, we improved the quality of the Cs2AgBiBr6 films and the performance of PDs by adding N-acetylethylenediamine (DEAC) to Cs2AgBiBr6 perovskite precursor for EPD, in which the ligand DEAC provides a pair of lone electrons to Bi3+, forming coordinate covalent bonds. The optimized PDs have high detectivity, up to 4.4×1012 Jones, and high stability in the air. The high-performance, flexible Cs2AgBiBr6 perovskite PDs were fabricated on this basis, it also achieved the detectivity up to 3.2×1012 Jones with excellent bending cycle stability. These results propose a feasible approach to improving the crystallization of double perovskite thin films by introducing ligands during the EPD process. Furthermore, they demonstrate enhanced optoelectronic performance, indicating that this method is also applicable to halide perovskites, offering an effective strategy to improve their film quality.

Cellulose nanofiber-reinforced antimicrobial and antioxidant multifunctional hydrogel with self-healing, adhesion for enhanced wound healing.

Current conventional wound dressings used for wound healing are often characterized by restricted bioactivity and devoid of multifunctionality resulting in suboptimal treatment and prolonged healing. Despite recent advances, the simultaneous incorporation of excellent flexibility, good mechanical performance, self-healing, bioactivity, and adhesion properties into the dressings without complicating their efficacy while maintaining simple synthesis remains a grand challenge. Herein, we effectively synthesized hybrid hydrogels of cellulose nanofiber (CNF), polyvinyl alcohol (PVA), and curcumin-modified silver nanoparticles (cAg) through a one-step synthesis method based on hydrogen bonds, dynamic boronic ester bonds, and coordinate covalent bonds. A flexible high mechanical strength (tensile stress (231kPa) and compressive stress (1.23MPa), self-healing, adhesive, yet highly antioxidant and antimicrobial hydrogel (with improved activity against C. albicans, S. aureus, and E. coli) is successfully obtained. Concentric structure of the micropores endows the hydrogels, good biodegradability, and sustained drug release of silver and curcumin. More remarkably, the designed hydrogel dressings not only significantly enhance cell viability (over 98%) and cell proliferation but also promote angiogenesis, re-epithelialization, and deposition of collagen, all of which signal wound closure and substantiate the therapeutic effect of CNF/PB/cAg hydrogels in chronic wounds. These findings open up new perspectives for the design of wound healing hydrogels and beyond.

Assembly of Silicate-Phenolic Network Coatings with Tunable Properties for Controlled Release of Small Molecules.

Engineered coatings are pivotal for tailoring the surface properties and release profiles of materials for applications across diverse areas. However, developing robust coatings that can both encapsulate and controllably release cargo is challenging. Herein, a dynamic covalent coordination assembly strategy is used to engineer robust silicate-based coatings, termed silicate-phenolic networks (SPNs), using sodium metasilicate and phenolic ligands (tannic acid, gallic acid, pyrogallol). The coatings are pH-responsive (owing to the dynamic covalent bonding), and their hydrophobicity can be tuned upon their post-functionalization with hydrophobic gallates (propyl, octyl, lauryl gallates). The potential of the SPN coatings for the controlled release of small molecules, such as urea (a widely used fertilizer), is demonstrated-controlled release of urea in soil is achieved in response to different pHs (up to 7 days) and different hydrophobicity (up to 14 days). Furthermore, leveraging the presence of silicon (within the coating) and post-functionalization of the SPN coatings with metal ions (Fe3+, Cu2+, Zn2+) generates a multipurpose delivery system for the sustained release of micronutrient fertilizers, and silicon and metal ions, over 28 and 14 days, respectively. These SPN coatings have potential applications beyond agriculture, including nutrient delivery, separations, food packaging, and medical device fabrication.

Modification Strategies and Prospects for Enhancing the Stability of Black Phosphorus.

Black phosphorus is a two-dimensional layer material with promising applications due to its many excellent physicochemical properties, including high carrier mobility, ambipolar field effect and unusual in-plane anisotropy. Currently, BP has been widely used in biomedical engineering, photocatalysis, semiconductor devices, and energy storage electrode materials. However, the unique structure of BP makes it highly chemically active, leading to its easy oxidation and degradation in air, which limits its practical applications. Recently, researchers have proposed a number of initiatives that can address the environmental instability of BP, and the application of these physical and chemical passivation techniques can effectively enhance the environmental stability of BP, including four modification methods: covalent functionalization, non-covalent functionalization, surface coordination, physical encapsulation and edge passivation. This review highlights the mechanisms of the above modification techniques in addressing the severe instability of BP in different application scenarios, as well as the advantages and disadvantages of each method. This review can provide guidance for more researchers in studying the marvellous properties of BP and accelerate the practical application of BP in different fields.

Metal-Based Drug-DNA Interactions and Analytical Determination Methods.

DNA structure has many potential places where endogenous compounds and xenobiotics can bind. Therefore, xenobiotics bind along the sites of the nucleic acid with the aim of changing its structure, its genetic message, and, implicitly, its functions. Currently, there are several mechanisms known to be involved in DNA binding. These mechanisms are covalent and non-covalent interactions. The covalent interaction or metal base coordination is an irreversible binding and it is represented by an intra-/interstrand cross-link. The non-covalent interaction is generally a reversible binding and it is represented by intercalation between DNA base pairs, insertion, major and/or minor groove binding, and electrostatic interactions with the sugar phosphate DNA backbone. In the present review, we focus on the types of DNA-metal complex interactions (including some representative examples) and on presenting the methods currently used to study them.

A self-healing, long-lasting adhesive, lignin-based polyvinyl alcohol organo-hydrogel for strain-sensing applications

Hydrogel-based flexible sensors have garnered considerable interest in the fields of soft electronics, robotics, and human-machine interfaces. For better practical applications, integrating multiple properties—such as self-adhesive, anti-freeze, anti-volatile, self-healing, and antibacterial—into a single gel for flexible sensors remains a challenge. In this paper, a multifunctional lignin-based polyvinyl alcohol gel, containing dynamic covalent bonds, hydrogen bonds, and coordination bonds, is constructed by a simple one-pot method, in which ethylene glycol/water chosen as a binary solvent and KI as a conductive medium. The resulting organogel exhibits self-healing, long-lasting adhesion, UV shielding, antibacterial properties, excellent frost resistance (−20 °C), and volatile resistance properties. In addition, the organogel-based sensor demonstrates satisfactory sensitivity in detecting joint movements and facial expressions. This study provides a new strategy for developing a versatile flexible sensor through the introduction of renewable and bio-based lignin, promising applications in the fields of wearable electronics.

Machine learning models and computational simulation techniques for prediction of anti-corrosion properties of novel benzimidazole derivatives

The present paper delves into the development of predictive models for the optimum prediction of inhibition efficiencies and anti-corrosion properties of newly designed benzimidazole compounds in an HCl medium. Density functional theory (DFT) was used to obtain the molecular descriptors. 17 descriptors considered as input variables were reduced to 9 after redundant variables were eliminated using the variance inflation factor (VIF). Machine learning models such as random forest regression (Rf), K-nearest neighbor (KNN), and gradient boosting (GB) were used to develop a predictive model using data from 50 benzimidazole derivatives whose inhibition efficiencies for steel alloy in HCl medium have been determined experimentally and are available in the literature. The cross-validation (CV) technique was used to evaluate the predictive capability of the models. KNN gave the best result with a coefficient of correlation (R2) of 0.654, compared to GB (0.591) and RF (0.512). Subsequently, the three models were used to predict the inhibition efficiencies of three novel benzimidazole compounds. The corrosion inhibition efficiency of three newly developed benzimidazole compounds was 91 % - 98.5 % when assessed with the best-performing model, K-nearest neighbor (KNN) with MSBAH recording the highest value of 98.5 %. Fukui indices parameters fk+k,fk−k,andf2(r) showed that both the electrophilic and nucleophilic sites are concentrated around specific atoms most of whom are heteroatoms that participate actively in electron-donor and acceptor interaction with the metal atom leading to the formation of coordinate covalent bonds. The results of electron distribution and Fukui dual descriptors support the results of the predictive model. The study also revealed that machine learning algorithms in conjunction with DFT and MD simulation is an innovative technique for the prediction of anti-corrosion properties of newly designed molecules such as corrosion inhibition efficiencies, and mechanism of inhibitor adsorption on metal/alloy surfaces exposed to an aggressive environment. This technique can be harnessed in proffering solutions to acid corrosion especially those that occur during descaling operation.

Double-bridged N–B←N bipyridyl-based airfoil-shaped small molecule dyes: π-bridge regulation on photovoltaic performance

The double-bridged N–B←N bipyridine unit (BNBP) with boron-nitrogen covalent bond and coordination bond can reduce the electronic energy level of the π-conjugated system, resulting in a reduction of band gap and a red shift in the absorption spectrum. Embedding the BNBP building block into organic optoelectronic materials provides a novel possibility in molecule design. In this paper, under the guidance of density functional theory (DFT) calculations, a series of 3D “airfoil-shaped” small molecule donors (SMDs) have been designed and successfully synthesized through Sonogashira, Suzuki and Stille coupling reactions. BNBP is adopted as the central electron-withdrawing unit and strong electron-rich triphenylamine (TPA) as the terminal group. The novel “airfoil-shaped” structure plays a supporting role in reducing the carrier recombination in the active layer. It reveals that molecular design engineering can achieve the expected results by the following steps: Firstly, the introduction of electron-rich alkoxy groups into the end of TPA through side chain engineering helps to improve the solubility and film-forming properties of the materials. Then, the π-bridge regulation not only extends the conjugate structure, but also plays a crucial role in the regulation of photovoltaic properties. It is worth noting that the compound BNBP(3TTPA)2 was synthesized by introducing thiophene oligomer into BNBP-based SMDs for the first time. Finally, the compound BNBP(EDPPTPA)2 was constructed by combining BNBP with DPP dye unit. Its narrow band gap is only 1.36 eV, which is one of the narrowest band gaps in small molecular organic-boron materials. In particular, compared with the starting compound BNBP(ETPA)2, the synergistic effects of DPP and BNBP broaden the edge absorption wavelength to 814 nm, resulting in a red shift of 170 nm. The power conversion efficiency (PCE) of 4.48 % is obtained in BNBP(EDPPTPA)2-based bulk heterojunction (BHJ) organic solar cells (OSCs), which is more than twice that of reference compound BNBP(ETPA)2. This work provides important references for the future development of 3D BNBP-based organic-boron SMDs and the structural regulation of materials through molecular engineering.

Synthesis and Characterization of Barley Starch-g-Polyacrylamide with Zinc Sulphate (ZnSO4) Metal Salt

There has been extensive interest from researchers in utilizing the natural biopolymer as a reinforcement material in thermoplastic composite. Growing research has been carried out on natural biopolymer reinforcement thermoplastic composites due to their low processing cost. Starch, a natural carbohydrate biopolymer due to its biodegradability and versatility, has become a subject of industrial and academic studies for many decades. Grafting of starch on various monomers increased the hydrophilicity and hydrophobicity. High viscosity, thermal stability, biodegradability, good film-forming properties, and water absorption capacity are some properties shown by the graft co-polymerization of starch. The present work was conducted to synthesize the barley starch-g-polyacrylamide-based composite material. In this research the effect of different weight percentages of metal (?10%) on different properties of starch-g- polyacrylamide (20% and 80%) composite was studied. The analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (X-ray), and scanning electron microscope (SEM) were used for the characterization of composite material. The composition of the synthesized composite was assessed by FTIR which confirmsthe functionalization of the prepared composite and there is a strong interaction between composite and metal due to coordinate covalent bonds. XRD defines the crystalline structure of the composite the morphological changes were studied by SEM.

Thiol-ene Click Chemistry Synthesis of L-Cysteine-Grafted Graphene Oxide As a New Corrosion Inhibitor for Q235 Steel in Acidic Environment.

l-cysteine, as an eco-friendly and nontoxic corrosion inhibitor, was directly covalently linked to the carbon/carbon double bonds of the GO flakes by a thiol-ene click reaction to avoid decreasing the number of hydrophilic oxygen-containing polar functionalities. The corrosion inhibition performances of Cys-GO toward Q235 steel (QS) in diluted hydrochloric acid were studied by electrochemical methods. The corrosion was a charge transfer-controlled process, and Cys-GO manifested as a mixed-type corrosion inhibitor. The corrosion inhibition efficiency (η) for QS showed a first-increase-and-then-decrease trend with increasing Cys-GO concentrations. The optimum concentration of Cys-GO was 15 mg L-1, and the according η value was up to 90%. The Cys-GO adsorbed on the QS surface to form a protective barrier was responsible for the efficient corrosion inhibition. Langmuir adsorption isotherm model was fitted well with the experiment data, indicating a monolayer adsorption. Furthermore, the coordinate covalent bonds, π-back-donation effect, and electrostatic attraction were responsible for the Cys-GO adsorption on the QS surface.

Organic cage-based frameworks: from synthesis to applications

The investigation of organic cage-based frameworks (OCFs) has attracted increasing attention over the past decade due to their versatile synthetic methods and broad property range resulting from the unique combination of porous organic cages (POCs) with diverse framework materials, including porous organic polymers (POPs), metal-organic frameworks (MOFs), and supramolecular organic frameworks (SOFs). Nevertheless, a comprehensive summary of the research advancements in OCFs remains elusive in the literature. This review addresses this gap by providing a detailed overview of the development of OCF-based materials from both synthetic and applicative perspectives. The discussion begins with systematically exploring design principles and common strategies for elaborating OCFs, achieved by rational selection of bond-forming routes suitable for various POC monomers, including covalent bonds, coordination bonds, and supramolecular interactions. Subsequently, the review highlights the functional attributes derived from the distinctive structural features of OCFs, showcasing their task-specific applications in adsorption/separation, catalysis, membrane technology, and other fields. Lastly, the article summarizes the opportunities and challenges anticipated as the exploration of the OCF family continues to advance in material science.

Time-series analysis of rhenium(I) organometallic covalent binding to a model protein for drug development.

Metal-based complexes with their unique chemical properties, including multiple oxidation states, radio-nuclear capabilities and various coordination geometries yield value as potential pharmaceuticals. Understanding the interactions between metals and biological systems will prove key for site-specific coordination of new metal-based lead compounds. This study merges the concepts of target coordination with fragment-based drug methodologies, supported by varying the anomalous scattering of rhenium along with infrared spectroscopy, and has identified rhenium metal sites bound covalently with two amino acid types within the model protein. A time-based series of lysozyme-rhenium-imidazole (HEWL-Re-Imi) crystals was analysed systematically over a span of 38 weeks. The main rhenium covalent coordination is observed at His15, Asp101 and Asp119. Weak (i.e. noncovalent) interactions are observed at other aspartic, asparagine, proline, tyrosine and tryptophan side chains. Detailed bond distance comparisons, including precision estimates, are reported, utilizing the diffraction precision index supplemented with small-molecule data from the Cambridge Structural Database. Key findings include changes in the protein structure induced at the rhenium metal binding site, not observed in similar metal-free structures. The binding sites are typically found along the solvent-channel-accessible protein surface. The three primary covalent metal binding sites are consistent throughout the time series, whereas binding to neighbouring amino acid residues changes through the time series. Co-crystallization was used, consistently yielding crystals four days after setup. After crystal formation, soaking of the compound into the crystal over 38 weeks is continued and explains these structural adjustments. It is the covalent bond stability at the three sites, their proximity to the solvent channel and the movement of residues to accommodate the metal that are important, and may prove useful for future radiopharmaceutical development including target modification.

Fabrication and Application of Ag@SiO2/Au Core-Shell SERS Composite in Detecting Cu2+ in Water Environment.

A sensitive and simple method for detecting Cu2+ in the water source was proposed by using surface-enhanced Raman scattering spectroscopy (SERS) based on the Ag@SiO2/Au core-shell composite. The Ag@SiO2 SERS tag was synthesized by a simple approach, in which Ag nanoparticles were first embedded with Raman reporter PATP and next coated with a SiO2 shell. The Ag@SiO2 nanoparticles had strong stability even in a high-concentration salty solution, and there were no changes to their properties and appearance within one month. The Ag@SiO2/Au composite was fabricated through a controllable self-assemble process. L-cysteine was decorated on the surface of a functionalized Ag@SiO2/Au composite, as the amino and carboxyl groups of it can form coordinate covalent bond with Cu2+, which shows that the Ag@SiO2/Au composite labelled with L-cysteine has excellent performance for the detection of Cu2+ in aqueous media. In this study, the SERS detection of Cu2+ was carried out using Ag@SiO2 nanoparticles, and the limit of detection (LOD) as low as 0.1 mg/L was achieved.

Reduced Schiff base as novel two-faced sensor for the detection of iron(III) and carbonate ions

The reduced Schiff base–naphthalene-2-ol (RSB) can be utilized as multifunctional probe to detect both Fe3+ and CO32–. The complexation was formed through coordinate covalent bond between Fe3+ and RSB, and through hydrogen bond between CO32– and RSB. The characterizations were investigated by UV–visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy and confirmed by density functional theory (DFT) calculation. The quenching mechanism of RSB with Fe3+ and CO32– were described through inner filter effect (IFE) and static quenching (SQ), respectively. Furthermore, the quenching of RSB was correlated to the concentrations of Fe3+ (R2 = 0.9966) and CO32– (R2 = 0.9954) within a linear range of 1 – 50 ppm. The limit of detection (LOD) and limit of quantification (LOQ) for Fe3+ were determined as 0.75 ppm and 2.52 ppm, respectively. Meanwhile, for CO32–, the LOD and LOQ were 0.27 ppm and 2.73 ppm, respectively. Finally, we demonstrate the application of RSB which can be easily synthesized and obtained with high yield to samples containing Fe3+ and CO32– with concentrations correlated to LOD and LOQ values.

Antibacterial adhesive based on oxidized tannic acid-chitosan for rapid hemostasis

Currently, bacterial infections and bleeding interfere with wound healing, and multifunctional hydrogels with appropriate blood homeostasis, skin adhesion, and antibacterial activity are desirable. In this study, chitosan-based hydrogels were synthesized using oxidized tannic acid (OTA) and Fe3+ as cross-linkers (CS-OTA-Fe) by forming covalent, non-covalent, and metal coordination bonds between Fe3+ and OTA. Our results demonstrated that CS-OTA-Fe hydrogels showed antibacterial properties against Gram-positive bacteria (Staphylococcus aureus)and Gram-negative bacteria (Escherichia coli), low hemolysis rate (< 2 %), rapid blood clotting ability, in vitro (< 2 min), and in vivo (90 s) in mouse liver bleeding. Additionally, increasing the chitosan concentration from 3 wt% to 4.5 wt% enhanced cross-linking in the network, leading to a significant improvement in the strength (from 106 ± 8 kPa to 168 ± 12 kPa) and compressive modulus (from 50 ± 9 kPa to 102 ± 14 kPa) of hydrogels. Moreover, CS-OTA-Fe hydrogels revealed significant adhesive strength (87 ± 8 kPa) to the cow's skin tissue and cytocompatibility against L929 fibroblasts. Overall, multifunctional CS-OTA-Fe hydrogels with tunable mechanical properties, excellent tissue adhesive, self-healing ability, good cytocompatibility, and fast hemostasis and antibacterial properties could be promising candidates for biomedical applications.

Enantioselective transformation of phytoplankton-derived dihydroxypropanesulfonate by marine bacteria.

Chirality, a fundamental property of matter, is often overlooked in the studies of marine organic matter cycles. Dihydroxypropanesulfonate (DHPS), a globally abundant organosulfur compound, serves as an ecologically important currency for nutrient and energy transfer from phytoplankton to bacteria in the ocean. However, the chirality of DHPS in nature and its transformation remain unclear. Here, we developed a novel approach using chiral phosphorus-reagent labeling to separate DHPS enantiomers. Our findings demonstrated that at least one enantiomer of DHPS is present in marine diatoms and coccolithophores, and that both enantiomers are widespread in marine environments. A novel chiral-selective DHPS catabolic pathway was identified in marine Roseobacteraceae strains, where HpsO and HpsP dehydrogenases at the gateway to DHPS catabolism act specifically on R-DHPS and S-DHPS, respectively. R-DHPS is also a substrate for the dehydrogenase HpsN. All three dehydrogenases generate stable hydrogen bonds between the chirality-center hydroxyls of DHPS and highly conserved residues, and HpsP also form coordinate-covalent bonds between the chirality-center hydroxyls and Zn2+, which determines the mechanistic basis of strict stereoselectivity. We further illustrated the role of enzymatic promiscuity in the evolution of DHPS metabolism in Roseobacteraceae and SAR11. This study provides the first evidence of chirality's involvement in phytoplankton-bacteria metabolic currencies, opening a new avenue for understanding the ocean organosulfur cycle.

ROS-responsive hydrogels: from design and additive manufacturing to biomedical applications.

Hydrogels with intricate 3D networks and high hydrophilicity have qualities resembling those of biological tissues, making them ideal candidates for use as smart biomedical materials. Reactive oxygen species (ROS) responsive hydrogels are an innovative class of smart hydrogels, and are cross-linked by ROS-responsive modules through covalent interactions, coordination interactions, or supramolecular interactions. Due to the introduction of ROS response modules, this class of hydrogels exhibits a sensitive response to the oxidative stress microenvironment existing in organisms. Simultaneously, due to the modularity of the ROS-responsive structure, ROS-responsive hydrogels can be manufactured on a large scale through additive manufacturing. This review will delve into the design, fabrication, and applications of ROS-responsive hydrogels. The main goal is to clarify the chemical principles that govern the response mechanism of these hydrogels, further providing new perspectives and methods for designing responsive hydrogel materials.

Functional structures assembled based on Au clusters with practical applications.

The advancement of gold nanoclusters (Au NCs) has given rise to a new era in fabricating functional materials due to their controllable morphology, stable optical properties, and excellent biocompatibility. Assemblies based on Au NCs demonstrate significant potentiality in constructing multiple structures as acceptable agents in applications such as sensing, imaging technology, and drug delivery systems. In addition, the assembled strategies illustrate the integration mechanism between each component while facing material requirement. It is necessary to provide supplementary and comprehensive reviews on the assembled functional structures (based Au NCs), which hold promise for applications and could expand their functional range and potential applications. This review focuses on the assembled structures of Au NCs in combination with metals, metal oxides, and non-metal materials, which are intricately arranged through various interaction forces including covalent bonds and metal coordination, resulting in a diverse array of multifunctional Au NC assemblies. These assemblies have widespread applications in fields such as biological imaging, drug delivery, and optical devices. The review concludes by highlighting the challenges and future prospects of Au NC assemblies, emphasizing the importance of continued research to advance nanomaterial assembly innovation.

Improving the Cyclic Reversibility of Layered Li-Rich Cathodes by Combining Oxygen Vacancies Introduction and Surface Fluorination

Layered-type Li-rich cathode materials have attracted significant attention for the next generation Li-ion batteries, but their poor reversibility in terms of both voltage and capacity upon cycling are as prominent as their high capacity. Irreversible oxygen redox activity and surface deterioration have been deemed as the root cause and direct cause for their poor performance, respectively. To mitigate those issues, we introduce substantial amounts of oxygen vacancies into layered-type Li1.2Ni0.2Co0.2Mn0.4O2 by using CaH2 as a reduction agent. Reduced samples show higher reversible capacity due to the increased cation redox participation, but still sustain poor cyclic performance. With further fluorination to reduced Li1.2Ni0.2Co0.2Mn0.4O2-x by using NH4HF2, the reversible capacity reached 270 mAh/g and maintained its 99% after 100 cycles. STEM-EELS detects deeper F signals rather than just on surface as direct fluorination methods show, and HAXPES patterns indicate there are both ionic and covalent fluorine coordination. These results demonstrate that by the combination of oxygen deficiency introduction and surface fluorination, some F- ions could occupy the sites of oxygen vacancies near the surface rather than sole LiF generation on the surface, which illuminates a new strategy to modify the cathode materials for Li-ion batteries. The Ni0.2Co0.2Mn0.4(OH)1.6 precursor was prepared by the coprecipitation of NiSO4, CoSO4 and MnSO4, and then mixed with LiOH. The mixture was calcined with oxygen flow at 900 ℃ to obtain pristine Li1.2Ni0.2Co0.2Mn0.4O2. The pristine Li1.2Ni0.2Co0.2Mn0.4O2 was reduced by the appropriate amount of CaH2 in a vacuumed glass tube at 260 ℃, then the reduced Li1.2Ni0.2Co0.2Mn0.4O1.85 was mixed with various amounts of NH4HF2 and sintered at 450 ℃ with argon flow. Hard X-ray photoemission spectroscopy (HAXPES, at BL46XU in SPring-8) was used to investigate the coordination state of fluorine ions. The electrodes of different samples were prepared by slurrying the active material, acetylene black, and PVDF with a weight ratio of 8:1:1, then coating on the Al foil. The 2032-type coin cells were assembled for the electrochemical test. The counter electrode was lithium metal and the electrolyte was 1 M LiPF6 in EC and EMC solvent (3:7 by volume). The charge-discharge test was operated on an automatic cycling and data recording system (HJ1001SD8, Hokuto Denko). Fig. 1a shows the F 1s HAXPES spectra of fluorinated samples which were synthesized by subjecting reduced Li1.2Ni0.2Co0.2Mn0.4O1.85 to chemical fluorination using NH4HF2. When F is 0.1 stoichiometry, F ions are more covalent which implies they could mainly occupy the oxygen vacancy sites near surface. Further fluorination increased the intensity of LiF on surface. The cyclic performance of four samples is shown in Fig. 1b. The pristine sample suffered from the severe capacity decay whose drastic oxygen redox activity is deemed to cause various deterioration [1]. Direct fluorination of pristine sample had some positive effect to the cyclic performance because of the reported interface stabilization [2]. The initial capacity of the reduced sample is higher than pristine sample owing to the increased cation redox contribution, but its cyclability is still poor especially after long cycles. The important point to note is the combination of reduction and fluorination significantly improved both the capacity and cyclic performance upon 100 cycles, and the coordination and role of fluorine ions could be different from the conventional fluorination strategy. Figure 1