Covalently Bonded Ni Sites in Black Phosphorene with Electron Redistribution for Efficient Metal‑Lightweighted Water Electrolysis

The metal-lightweighted electrocatalysts for water splitting are highly desired for sustainable and economic hydrogen energy deployments,but challengeable.In this work,a low-content Ni-functionalized approach triggers the high capability of black phosphorene(BP)with hydrogen and oxygen evolution reaction(HER/OER)bifunctionality.Through a facile in situ electro-exfoliation route,the ionized Ni sites are covalently functionalized in BP nanosheets with electron redistribution and controllable metal contents.It is found that the as-fabricated Ni-BP electrocatalysts can drive the water splitting with much enhanced HER and OER activities.In 1.0 M KOH electrolyte,the optimized 1.5 wt%Nifunctionalized BP nanosheets have readily achieved low overpotentials of 136 mV for HER and 230 mV for OER at 10 mA cm^(−2).Moreover,the covalently bonding between Ni and P has also strengthened the catalytic stability of the Ni-functionalized BP electrocatalyst,stably delivering the overall water splitting for 50 h at 20 mA cm^(−2).Theoretical calculations have revealed that Ni–P covalent binding can regulate the electronic structure and optimize the reaction energy barrier to improve the catalytic activity effectively.This work confirms that Ni-functionalized BP is a suitable candidate for electrocatalytic overall water splitting,and provides effective strategies for constructing metal-lightweighted economic electrocatalysts.

Novel therapeutic approaches for hepatitis B virus covalently closed circular DNA

Hepatitis B virus(HBV) infection is a major global health problem. Although current therapies, such as the use of nucleos(t)ide analogs, inhibit HBV replication efficiently, they do not eliminate covalently closed circular DNA(ccc DNA), which persists in hepatocyte nuclei. As HBV ccc DNA is a viral transcription template, novel therapeutic approaches to directly target HBV ccc DNA are necessary to completely eradicate persistent HBV infections. HBV ccc DNA levels in HBV-infected human liver cells are extremely low; thus, more reliable and simple measurement methods are needed to correctly monitor their levels during therapeutic treatment. Although reverse transcription-polymerase chain reaction or Southern blot procedures are currently used in research studies, these methods are not completely reliable and are also time-consuming and labor-intensive. Genome editing technologies, such as zinc finger nucleases, transcription activator-like effector nucleases, and the clustered regularly interspaced short palindromic repeats/Cas9(CRISPR/Cas9) system, which are designed to target specific DNA sequences, represent highly promising potential therapeutic tools. In particular, the CRISPR/Cas9 system is an easily customizable sequencespecific nuclease with high flexibility and may be the most feasible approach to target HBV ccc DNA. Further research to develop easier, safer, and more effective protocols should be pursued.

Intracellular interferon signalling pathways as potential regulators of covalently closed circular DNA in the treatment of chronic hepatitis B

250 million people worldwide continue to be chronically infected with the virus.While patients may be treated with nucleoside/nucleotide analogues,this only suppresses HBV titre to sub-detection levels without eliminating the persistent HBV covalently closed circular DNA(cccDNA)genome.As a result,HBV infection cannot be cured,and the virus reactivates when conditions are favorable.Interferons(IFNs)are cytokines known to induce powerful antiviral mechanisms that clear viruses from infected cells.They have been shown to induce cccDNA clearance,but their use in the treatment of HBV infection is limited as HBVtargeting immune cells are exhausted and HBV has evolved multiple mechanisms to evade and suppress IFN signalling.Thus,to fully utilize IFN-mediated intracellular mechanisms to effectively eliminate HBV,instead of direct IFN administration,novel strategies to sustain IFN-mediated anti-cccDNA and antiviral mechanisms need to be developed.This review will consolidate what is known about how IFNs act to achieve its intracellular antiviral effects and highlight the critical interferon-stimulated gene targets and effector mechanisms with potent anti-cccDNA functions.These include cccDNA degradation by APOBECs and cccDNA silencing and transcription repression by epigenetic modifications.In addition,the mechanisms that HBV employs to disrupt IFN signalling will be discussed.Drugs that have been developed or are in the pipeline for components of the IFN signalling pathway and HBV targets that detract IFN signalling mechanisms will also be identified and discussed for utility in the treatment of HBV infections.Together,these will provide useful insights into design strategies that specifically target cccDNA for the eradication of HBV.

Role of hepatitis B virus in development of hepatocellular carcinoma:Focus on covalently closed circular DNA

Chronic infection with hepatitis B virus(HBV)remains a major global health problem,especially in developing countries.It may lead to prolonged liver damage,fibrosis,cirrhosis,and hepatocellular carcinoma.Persistent chronic HBV infection is related to host immune response and the stability of the covalently closed circular DNA(cccDNA)in human hepatocytes.In addition to being essential for viral transcription and replication,cccDNA is also suspected to play a role in persistent HBV infections or hepatitis relapses since cccDNA is very stable in non-dividing human hepatocytes.Understanding the pathogenicity and oncogenicity of HBV components would be essential in the development of new diagnostic tools and treatment strategies.This review summarizes the role and molecular mechanisms of HBV cccDNA in hepatocyte transformation and hepatocarcinogenesis and current efforts to its detection and targeting.

Electrocatalysis of NADH Oxidation with 3,4-Dihydroxybenzoic Acid Covalently Bound to Self-assembled

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Synthesis and Luminescence Properties of SBA-15 Functionalized with Covalently Bonded Terbium-Benzoic Acid Complex

Novel hybrid materials containing covalently bonded Terbium-benzoic acid complex in mesoporous silicaSBA-15 (denoted as Tb-SBA-15 ) were prepared via co-condensation of tetrethoxysilane (TEOS) and N-(4-benzoicacid-yl), N'-(propyltriethoxysilyl) urea (denoted as PABI).XRD, FTIR and luminescence spectroscopy were employed to characterize Tb-SBA-15.When monitored by the ligand absorption wavelength (270 nm), Tb-SBA-15 displays the emission of Tb3+ (5D4→7Fj (j = 6, 5, 4, 3 ) transition) due to the energy transfer from the ligands to Tb3+.

SPECTROSCOPIC STUDIES ON A HETEROMETALLOBINUCLEAR COMPLEX IN WHICH Ru(BPY)_3^(2+)WAS COVALENTLY ATTACHED TO N_i^-(CYCLAM)^(2+)

The spectroscopic properties for a recently synthesized hetero-metallo- binuclear complex Ru(bpy)_2 (bpy-cyclam-Ni)^(4+)(3)and its related complexes 1 and 2 were investigated by UV-vis and emission spectral methods.A drastic quenching of fluorescence from the Ru(bpy)_3^(2+) subunit by the covalently attached quencher sub- unit Ni(cyclam)^(2+) was observed for complex 3,and the mechanism was discussed.

<i>β</i>-cyclodextrin Covalently Functionalized Single-Walled Carbon Nanotubes: Synthesis, Characterization and a Sensitive Biosensor Platform

In this study, we presented the preparation of β-cyclodextrin (β-CD) covalently functionalized single-walled carbon nanotubes (SWCNTs) and its application in modifying the solid glass carbon electrode (GCE). Cyclic voltammetry (CV) method was employed to evaluate the performance of the modified GCE. Solubility experiment indicated the conjugation of SWCNTs and β-CD, SWCNTs-β-CD with 8 wt% β-CD content could be well dispersed in water. High-resolution transmission electron microscopy (HRTEM) demonstrated that the aggregated SWCNTs bundle were effectively exfoliated to small bundle, even individual tube. The β-CD component was grafted on the side walls as well as tips of SWCNTs, and the grafted β-CD component was not uniformly coated on the surface of SWCNTs. The CV measurements indicated the performance of the GCE modified by SWCNTs-β-CD was better than that of the GCE modified by the hybrid of SWCNTs/β-CD, where ascorbic acid (AA) and uric acid (UA) were selected as a prelimiltary substrate to evaluate it. The enhanced performance of the modified GCE should be ascribed to the integration of the excellent electrocatalytic property of SWCNTs with the inclusion ability of β-CD to analyte molecule.

Covalently integrated core-shell MOF@COF hybrids as efficient visible-light-driven photocatalysts for selective oxidation of alcohols

Building a covalently connected structure with accelerated photo-induced electrons and charge-carrier separation between semiconductors could enhance the photocatalytic performance.In this work,we report a facile and novel seed growth method to coat NH2-MIL-125 MOFs with crystalline and porous covalent organic frameworks(COFs)materials and form a range of NH2-MIL-125@TAPB-PDA nanocomposites with different thicknesses of COF shell.The introduction of appropriate content of COF could not only modify the intrinsic electronic and optical properties,but also enhance the photocatalytic activity distinctly.Especially,NH2-MIL-125@TAPB-PDA-3 with COF shell thickness of around 20nm exhibited the highest yield(94.7%)of benzaldehyde which is approximately 2.5 and 15.5 times as that of parental NH2-MIL-125 and COF,respectively.The promoted photocatalytic performance of hybrid materials was mainly owing to the enhanced photo-induced charge carriers transfer between the MOF and COF through the covalent bond.In addition,a possible mechanism to elucidate the process of photocatalysis was explored.Therefore,this kind of MOF-based photocatalysts possesses great potentials in future green organic synthesis.

Solid-Contact Perchlorate Sensor with Nanomolar Detection Limit Based on Cobalt Phthalocyanine Ionophores Covalently Attached to Polyacrylamide

Novel solid-contact perchlorate sensors based on cobalt phthalocyanine-C-monocarboxylic acid (I), and cobalt phthalocyanine-C,C,C,C-tetracarboxylic acid (II) as free ionophores and covalently attached to polyacryla- mide (PAA)—ionophores III and IV, respectively were prepared. The all solid-state sensors were constructed by the application of a thin film of a polymer cocktail containing a phthalocyanine ionophore and cetyltrimethylammonium bromide (CTMAB) as a lipophilic cationic additive onto a gold electrode precoated with the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) as an ion and electron transducer. The sensor with 10.3% of ionophore (III) covalently attached to plasticizer-free poly (butyl methacrylate-co-do- decyl methacrylate) (PBDA) exhibited a good selectivity for perchlorate and discriminated many ions, in- cluding F–, Cl–, Br–, I–, SCN–, , S2– and . The covalent attachment of the ionophore to the polymer resulted in a near-Nernstian anionic slope of –62.3 mV/decade whereas a super-Nernstian slope of –79.9 mV/ decade was obtained for the free ionophore. The sensor covered a linear concentration range of 5 × 10–9 - 1 × 10–2 mol?L–1 with a lower detection limit (LDL) of 1 × 10–9 mol?L–1 and gave a stable response over a pH range of 4 - 10.5. The all-solid state sensors were utilized for the selective flow injection potentiometric determination of perchlorate in natural water and human urine samples in the nanomolar concentration range.

DL-Serine covalently modified multinuclear lanthanide-implanted arsenotungstates with fast photochromism

A series of DL-serine covalently modified multinuclear lanthanide implanted arsenotungstates K_(2)[{Ln(H_(2)O)_(7)}_(2){As_(4)W_(44)O_(137)(OH)_(18)(H_(2)O)_(2)(DL-Ser)_(2)}{Ln_(2)(H_(2)O)_(5)(DL-Ser)}_(2)]·65H_(2)O(DL-Ser=DL-serine,Ln=La(1),Ce(2),Pr(3))are obtained.Crystal structure analysis shows that these compounds are isomorphic and contain the basic[{As_(4)W_(44)O_(137)(OH)_(18)(H_(2)O)_(2)(DL-Ser)_(2)}{Ln_(2)(H_(2)O)_(5)(DL-Ser)}_(2)]^(8–)polyoxoanion constituted by two{As_(2)W_(19)O_(59)(OH)_(8)(H_(2)O)}^(6–)subunits,a[W_(6)O_(2)_(3)(OH)_(2)(DL-Ser)_(2)]_(14)–fragment,and two embedded[Ln_(2)(H_(2)O)_(5)(DL-Ser)]^(5+)groups,which further build into one dimensional linear chainlike structure via two peripheral Ln^(3+)ions.Most remarkably,these compounds exhibit rapid photochromic behaviors,which changed color quickly from white(1),yellow(2),green(3)to blue(1),brown(2)and glaucous(3)in ten minutes under UV irradiation,and that the colors gradually recovered in the dark for approximately 22 h.

Nested real-time quantitative polymerase chain reaction assay for detection of hepatitis B virus covalently closed circular DNA

Background Successful treatment of hepatitis B can be achieved only if the template for hepatitis B virus （HBV） DNA replication, the covalently closed circular HBV DNA （cccDNA） can be completely cleared. To date, detecting cccDNA remains clinically challenging. The purpose of this study was to develop a nested real-time quantitative polymerase chain reaction （PCR） assay for detecting HBV cccDNA in peripheral blood mononuclear cells （PBMCs） and bone marrow mononuclear cells （MMNCs）. Methods Based on the structural differences between HBV cccDNA and HBV relaxed circular DNA （rcDNA）, two pairs of primers were synthesized as well as a downstream TaqMan probe. Blood and bone marrow samples were collected from hepatitis B patients and healthy controls. To remove rcDNA, samples were incubated with mung bean nuclease and the resultant purified HBV cccDNA was then amplified by nested real-time fluorescence quantitative PCR. The cccDNA levels were calculated using a positive standard. Results The nested real-time fluorescence quantitative PCR method for HBV cccDNA was successful, with a linear range of 3.0×10^2 copies/ml to 3.9×10^8 copies/ml. Of the 25 PBMC samples and 7 MMNC samples obtained from chronic hepatitis B or liver cirrhosis patients, 3 MMNC samples and 9 PBMC samples were positive for HBV cccDNA, while all of the 21 PBMC samples from healthy controls were negative. Conclusion The nested real-time fluorescence quantitative PCR may be used as an important tool for detecting cccDNA in hepatitis B patients.

Recent advances in the study of hepatitis B virus covalently closed circular DNA

Chronic hepatitis B infection is caused by hepatitis B virus(HBV) and a total cure is yet to be achieved. The viral covalently closed circular DNA(ccc DNA) is the key to establish a persistent infection within hepatocytes. Current antiviral strategies have no effect on the pre-existing ccc DNA reservoir. Therefore, the study of the molecular mechanism of ccc DNA formation is becoming a major focus of HBV research. This review summarizes the current advances in ccc DNA molecular biology and the latest studies on the elimination or inactivation of ccc DNA, including three major areas:(1) epigenetic regulation of ccc DNA by HBV X protein,(2) immune-mediated degradation,and(3) genome-editing nucleases. All these aspects provide clues on how to finally attain a cure for chronic hepatitis B infection.

Anthraquinone Covalently Modified Carbon Nanotubes for Efficient and Steady Electrocatalytic H2O2 Generation

Anthraquinone(AQ)modified carbon materials could be endowed with significantly improved oxygen re-duction reaction(ORR)activity.However,the application of these materials in the generation of hydrogen peroxide(H2O2)has been rarely investigated.For this motivation,AQ covalently modified carbon nanotube(AQ-CNT)was pur-posely synthesized for H2O2 generation.It was found that the cumulative H2O2 concentration reached up to 187.18 mg(Lh)over AQ(40)-CNT catalyst,nearly 2.0 times higher than that over CNT,and being superior to those over most carbon materials reported.The enhanced activity stemmed from the improved mass transfer fficiency of oxygen and the enhanced electrocatalytic activity.Noteworthily,the AQ(40)-CNT material exhibited satisfactory stability for H2O2 generation,which was ascribed to the strong interaction force of C-N covalent bond.The present work could provide a vital idea for designing electrode material with simultancously improved activity and stability for H2O2 gencration.

Advances of Electrochemical and Electrochemiluminescent Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks(COFs),a rapidly developing category of crystalline conjugated organic polymers,possess highly ordered structures,large specific surface areas,stable chemical properties,and tunable pore microenvironments.Since the first report of boroxine/boronate ester-linked COFs in 2005,COFs have rapidly gained popularity,showing important application prospects in various fields,such as sensing,catalysis,separation,and energy storage.Among them,COFs-based electrochemical(EC)sensors with upgraded analytical performance are arousing extensive interest.In this review,therefore,we summarize the basic properties and the general synthesis methods of COFs used in the field of electroanalytical chemistry,with special emphasis on their usages in the fabrication of chemical sensors,ions sensors,immunosensors,and aptasensors.Notably,the emerged COFs in the electrochemiluminescence(ECL)realm are thoroughly covered along with their preliminary applications.Additionally,final conclusions on state-of-the-art COFs are provided in terms of EC and ECL sensors,as well as challenges and prospects for extending and improving the research and applications of COFs in electroanalytical chemistry.

Challenges and Opportunities in Preserving Key Structural Features of 3D-Printed Metal/Covalent Organic Framework

Metal-organic framework(MOF)and covalent organic framework(COF)are a huge group of advanced porous materials exhibiting attractive and tunable microstructural features,such as large surface area,tunable pore size,and functional surfaces,which have significant values in various application areas.The emerging 3D printing technology further provides MOF and COFs(M/COFs)with higher designability of their macrostructure and demonstrates large achievements in their performance by shaping them into advanced 3D monoliths.However,the currently available 3D printing M/COFs strategy faces a major challenge of severe destruction of M/COFs’microstructural features,both during and after 3D printing.It is envisioned that preserving the microstructure of M/COFs in the 3D-printed monolith will bring a great improvement to the related applications.In this overview,the 3D-printed M/COFs are categorized into M/COF-mixed monoliths and M/COF-covered monoliths.Their differences in the properties,applications,and current research states are discussed.The up-to-date advancements in paste/scaffold composition and printing/covering methods to preserve the superior M/COF microstructure during 3D printing are further discussed for the two types of 3D-printed M/COF.Throughout the analysis of the current states of 3D-printed M/COFs,the expected future research direction to achieve a highly preserved microstructure in the 3D monolith is proposed.

Covalently Cross-Linked and Mechanochemiluminescent Polyolefins Capable of Self-Healing and Self-Reporting

Compared with non-cross-linked and dynamically covalent polymers,covalently cross-linked networks are irreplaceableinmany areas;however,they aredifficult to repair once fractured,due to limited polymer chain diffusion after cross-linking.Herein,the authors have reported a newkind of permanently cross-linked polyolefin,which when attached with amide side groups,yieldmechanically robust yet readily repairablematerials.A key is to use low cross-linking density,which enables satisfactory elasticity and chain mobility for thermodynamically favored healing.Another key is to incorporate dense hydrogen bonds that can undergo reversible associations.These factors jointly promise polyolefin networks with good mechanical properties and self-healing performance(recovered spontaneously up to 96%of its original tensile strength).More importantly,by means of mechanochemiluminescence from 1,2-dioxetane,which serves as the cross-linker and built-in self-reporting stress probe,a microscopic evaluation of how the chain entanglement proceeds upon healing and how failure occurs in the network can be obtained.

Metal-free two-dimensional phosphorene-based electrocatalyst with covalent P-N heterointerfacial reconstruction for electrolyte-lean lithium-sulfur batteries

The use of lithium-sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes.Two-dimensional(2D)few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium-sulfur battery electrocatalysts,which,however,have limitations of restricted catalytic activity and poor electrochemical/chemical stability.To resolve these issues,we developed a multifunctional metal-free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen-doped carbon-coated multiwalled carbon nanotubes(denoted c-FBP-NC).The experimental characterizations and theoretical calculations show that the formed polarized P-N covalent bonds in c-FBP-NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides,thus alleviating the shuttle effect.Meanwhile,the robust 1D-2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer.Impressively,with c-FBP-NC as the sulfur host,the battery shows a high areal capacity of 7.69 mAh cm^(−2) under high sulfur loading of 8.74 mg cm^(−2) and a low electrolyte/sulfur ratio of 5.7μL mg^(−1).Moreover,the assembled pouch cell with sulfur loading of 4 mg cm^(−2) and an electrolyte/sulfur ratio of 3.5μL mg^(−1) shows good rate capability and outstanding cyclability.This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry,demonstrating great potential in lithium-sulfur batteries.

All‑Covalent Organic Framework Nanofilms Assembled Lithium‑Ion Capacitor to Solve the Imbalanced Charge Storage Kinetics

Free-standing covalent organic framework(COFs)nanofilms exhibit a remarkable ability to rapidly intercalate/de-intercalate Li^(+) in lithium-ion batteries,while simultaneously exposing affluent active sites in supercapacitors.The development of these nanofilms offers a promising solution to address the persistent challenge of imbalanced charge storage kinetics between battery-type anode and capacitor-type cathode in lithium-ion capacitors(LICs).Herein,for the first time,custom-made COFBTMB-TP and COFTAPB-BPY nanofilms are synthesized as the anode and cathode,respectively,for an all-COF nanofilm-structured LIC.The COFBTMB-TP nanofilm with strong electronegative–CF3 groups enables tuning the partial electron cloud density for Li^(+) migration to ensure the rapid anode kinetic process.The thickness-regulated cathodic COFTAPB-BPY nanofilm can fit the anodic COF nanofilm in the capacity.Due to the aligned 1D channel,2D aromatic skeleton and accessible active sites of COF nanofilms,the whole COFTAPB-BPY//COFBTMB-TP LIC demonstrates a high energy density of 318 mWh cm^(−3) at a high-power density of 6 W cm^(−3),excellent rate capability,good cycle stability with the capacity retention rate of 77%after 5000-cycle.The COFTAPB-BPY//COFBTMB-TP LIC represents a new benchmark for currently reported film-type LICs and even film-type supercapacitors.After being comprehensively explored via ex situ XPS,7Li solid-state NMR analyses,and DFT calculation,it is found that the COFBTMB-TP nanofilm facilitates the reversible conversion of semi-ionic to ionic C–F bonds during lithium storage.COFBTMB-TP exhibits a strong interaction with Li^(+) due to the C–F,C=O,and C–N bonds,facilitating Li^(+) desolation and absorption from the electrolyte.This work addresses the challenge of imbalanced charge storage kinetics and capacity between the anode and cathode and also pave the way for future miniaturized and wearable LIC devices.