Dipole polarization modulating of vinylene-linked covalent organic frameworks for efficient photocatalytic hydrogen evolution

Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.

Effect of vinylene carbonate as electrolyte additive on cycling performance of LiFePO_4/graphite cell at elevated temperature

Effects of film-forming additive on stability of electrode and cycling performance of LiFePO4/graphite cell at elevated temperature were studied. Two 18650 cells with and without VC additive were investigated by galvanostatic cycling, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis and Raman spectroscopy. The results show that in the presence of VC additive, dissolution of Fe from LiFePO4 material is greatly depressed and stability of graphite structure is improved; the additive can not only reduce reaction of electrolyte on surface of LiFePO4 electrode but also suppress reduction of solvent and thickening of the solid electrolyte interface （SEI） layer on graphite surface. Electrolyte with VC is considered to be a good candidate for improving cycling performance of the LiFePOa/graphite cell at elevated temperature.

Achieving long-cycling sodium-ion full cells in ether-based electrolyte with vinylene carbonate additive

Application of sodium-ion batteries is suppressed due to the lack of appropriate electrolytes matching cathode and anode simultaneously.Ether-based electrolytes,preference of anode materials,cannot match with high-potential cathodes failing to apply in full cells.Herein,vinylene carbonate(VC)as an additive into NaCF_(3) SO_(3)-Diglyme(DGM)could make sodium-ion full cells applicable without preactivation of cathode and anode.The assembled FeS@C||Na3 V2(PO_(4))_(3)@C full cell with this electrolyte exhibits long term cycling stability and high capacity retention.The deduced reason is additive VC,whose HOMO level value is close to that of DGM,not only change the solvent sheath structure of Na^(+),but also is synergistically oxidized with DGM to form integrity and consecutive cathode electrolyte interphase on Na3 V2(PO_(4))_(3)@C cathode,which could effectively improve the oxidative stability of electrolyte and prevent the electrolyte decomposition.This work displays a new way to optimize the sodium-ion full cell seasily with bright practical application potential.

INFLUENCE OF TRACES OF WATER ON THE SYNTHESIS AND ELECTROLUMINESCENCE PROPERTIES OF POLY(2-METHOXY, 5- (2' -ETHYLHEXYL OXY)- 1, 4-PHENYLENE VINYLENE)

It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease of Molecular weight of the poly(2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene) during the polymerization, which ultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPV prepared under dry conditions has an external quantum efficiency of above 2.0%.

Vinylene carbonate additive for EMITFSI-based electrolyte for Li/LiFePO_4 batteries

Ionic liquids have been paid much attention and are considered to replace the conventional organic electrolyte and solve the safety issues by virtue of nonvolatility,non-flammability,high ionic conductivity and extended electrochemical steady window.The paper introduces ionic liquids electrolyte on basis of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI),which shows a wide electrochemical window (0.5-4.5 V vs.Li+/Li),and is theoretically feasible as an electrolyte for Li/LiFePO4batteries to improve the safety.Linear sweep voltammetry (LSV) was performed to investigate the electrochemical stability window of the polymer electrolyte.Interfacial resistance for Li/electrolyte/Li symmetric cells and Li/electrolyte/LiFePO4 cells were studied by electrochemical impedance spectroscopy (EIS).The results showed that additive vinylene carbonate (VC) enhances the formation of solid electrolyte interphase film to protect lithium anodes from corrosion and improves the compatibility of ionic liquid electrolyte towards lithium anodes.Accordingly,Li/LiFePO4cells delivers the initial discharge capacity of 124 mAh g-1 at a current rate of 0.1C in the ionic liquid electrolyte (EMITFSI+0.8 mol L-1LiTFSI+5 wt%VC),and shows better cyclability than in the ionic liquid electrolyte without VC.

Effect of Chemical Doping and Ion Implantation on Cond uctivity of Poly(p-phenylene vinylene) Derivatives

The surface conductivity of poly [ 2-methoxy-5-（3＇-methyl） butoxy]-p-phenylene vinylene （PMOMBOPV） films doped with FeCl3 and H2SO4 by chemical method and implanted by N^＋ ions was studied and the comparison of environmental stability of conductive behavior was also investigated. The energy and dose of N^＋ ions were in the rang 15～35 keV and 3. 8×10^15～9. 6×10^16 ions/cm^2, respectively. The conductivity of PMOMBOPV film was enhanced remarkably with the increases of the energy and dose of N^＋ ions. For example, the conductivity of PMOMBOPV film was 3. 2×10^-2S/cm when ion implantation was performed with an energy of 35 keV at a dose of 9. 6 × 10^14 ions/cm^2 , which was almost seven orders of magnitude higher than that of film unimplanted. The environmental stability of conductive behavior for ionimplanted film was much better than that of chemical doped films. Moreover, the conductive activation energy of ion-implanted films was measured to be about 0.17 eV.

PROPERTIES AND SYNTHESIS OF NEW SUPPORTS FOR IMMOBILIZATION OF ENZYMES BY COPOLYMERIZATION OF VINYLENE CARBONATE AND METHACRYLIC ACID

Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.

INVESTIGATIONS ON VINYLENE CARBONATE Ⅰ. PREPARATION AND PROPERTIES OF POLY-(VINYLENEC ARBONATE)

Bulk polymerization of vinylene carbonate using t-butylperoxypivalate at 40℃gave colourless, high molecular weight poly(vinylene carbonate) (PVCA). Solutions of PVCA in acetone and DMF are not stable at 25℃and this degradation was studied. From measurements in DMF with unfractionated PVCA a Mark-Houwink equation was obtained:

Tuning the optoelectronic properties of vinylene linked perylenediimide dimer by ring annulation at the inside or outside bay positions for fullerene-free organic solar cells

Among various perylenediimide(PDI)-based small molecular non-fullerene acceptors(NFAs),PDI dimer can effectively avoid the excessive aggregation of single PDI and improve the photovoltaic performance.However,the twist of perylene core in PDI dimer will destroy the effective conjugation.Thus,ring annulation of PDI dimer is a feasible method to balance the film quality and electron transport,but the systematic study has attracted few attentions.Herein,we choose a simple vinylene linked PDI dimer,V-PDI2,and then conduct further studies on the structure-property-performance relationship of four kinds of derived fused-PDI dimers,namely V-TDI2,V-FDI2,V-PDIS2 and V-PDISe2 respectively.The former two are incorporated thianaphthene and benzofuran at the inside bay positions,and the latter two are fused thiophene and selenophene at the outside bay positions,respectively.Theoretical calculations reveal the inside-and outside-fused structures largely affect the skeleton configuration,the former two tend to be planar structure and the latter two maintain the distorted backbone.The photovoltaic characterizations show that the inside-fused PDI dimers offer high open circuit voltage(VOC),while the outside-fused PDI dimers afford large short-circuit current density(JSC).This variation tendency results from the reasonably tunable energy levels,light absorption,molecular crystallinity and film morphology.As a result,PBDB-T:V-PDISe2 device exhibits the highest power conversion efficiency(PCE)of 6.51%,and PBDB-T:VFDI2 device realizes the highest VOC of 1.00 V.This contribution indicates that annulation of PDI dimers in outside or inside bay regions is a feasible method to modulate the properties of PDI-based non-fullerene acceptors.

SYNTHESIS OF SOLUBLE POLY(3-HEXYL-2,5-THIENYLENE VINYLENE) FROM THIOPHENE

Soluble poly(3-hexyl-2,5-thienylene vinylene) (PHTV) was readily synthesized from thiophene in a yield better than that of the precursor method to prepare poly(thienylene vinylene) (PTV). The bandgap of the polymer is about 1.8 eV, which is comparable with that of PTV. Owing to the introduction of alkyl side groups onto the backbone of the polymer, it can be dissolved in common organic solvents such as chloroform, THF and toluene. The synthesis of soluble PHTV is a very important approach to preventing oxidation and to improving the properties and the processbility of the PTV. The existence of alkyl side groups in PHTV does not affect its, bandgap and thermal properties as compared with PTV. After doping with FeCl3, the conductivity of PHTV is as high as 1.1 x 10(-2) S/cm. The soluble PHTV can be easily transformed into thin film with much better quality than that of the PTV film prepared by the traditional precursor method, which is very important for fabricating devices with good properties.

Alkyl Thiophene Vinylene Electropolimerization in C₈mimPF₆, Potential Use in Solar Cells

We report the electrosynthesis of a novel semiconductor polymer based on alkyl vinylthiophene derivative in the presence of an ionic liquid (IL). The polymerization was performed under galvanostatic conditions and the polymer was studied as potential donor component of a multilayer heterojunction organic solar cell (OSC). The monomer used was (E)-1,2-di-(3-octyl-2-thienyl) vinylene (OTV) and the IL used for the electropolymerization was 1-octyl-3-methylimidazole hexafluorophosphate C8mimPF6. Optical properties, stability and morphology of the polymer were analyzed using FT-IR, UV-vis, Raman and XPS spectroscopy. Voltammetry analysis and scanning electron microscopy (SEM-EDX) were also performed on the polymer. The OSC assembled with the polymer of OTV was used as electro donor and C60 as acceptor. Molybdenum trioxide (MoO3) and bathocuproine (BCP) were used as buffer layer between anode and cathode respectively. I-V curves, in the dark and under AM 1.5 solar simulator were performed to measure its efficiency.

The Synthesis and Electronic Characteristics of Poly(p-Phenylene Vinylene) Derivatives

A series of soluble poly(p-phenylene vinylene) (PPV) derivatives were synthesized through dehydrochlorination with the p-metaoxy phenol as starting materials. The electronic characteristics of PPV derivatives were studied.

Investigation of Intrachain Exciton Diffusion of MEH-PPV in Solution with Different Polarity

Femtosecond time-resolved transient grating technique was adopted to insight into the intra-chain exciton diffusion of MEH-PPV in solution with different polarity. Broadband white-light continuum was introduced as the probe to observe the transient absorption and the femtosecond time-resolved transient grating information simultaneously. The vibrational dephasing behaviors, single exciton relaxation, and population relaxation dynamics of MEH-PPV were systematically investigated. The result shows that the relaxation processes of the sample solution will be accelerated in the solvent with larger polarity.

Synthesis and Characterization of Poly(1-methoxy-4-octyloxy)-Para-Phenylene Vinylen for Light-Emitting Diodes Application

In this study, the conjugated polymer, poly(1-methoxy-4-octyloxy)-para-phenylene vinylene (MO-p-PPV) was synthesized and characterized. MO-p-PPV was synthesized according to Gilch polymerization mechanism by using 4-methoxyphenol as starting material in the presence of potassium tert-butoxide (1M in THF). The product was further purified by multiple precipitations in different solvents such as methanol, tetrahydrofuran, isopropyl alcohol and hexane. The final product was dried to afford MO-p-PPV as a red solid. The resulting polymer was completely soluble in common organic solvents. The structure of monomer and optical properties of polymer were characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy, UV-vis spectroscopy, and fluorescence spectroscopy. The UV-vis spectrum showed absorption maxima for MO-p-PPV at 491 nm. Similarly, fluorescence spectrum showed λmax emission at 540 nm.

Mechanochromism of polyurethane based on folding-unfolding of cyano-substituted oligo(p-phenylene)vinylene dimer

The incorporation of mechanophores,motifs that transform mechanical stimulus into chemical reaction or optical variation,allows creating materials with stressresponsive properties.The most widely used mechanophore generally features a weak bond,but its cleavage is typical an irreversible process.Here,we showed that this problem can be solved by folding–unfolding of a molecular tweezer.We systematically studied the mechanochromic properties of polyurethanes with cyano-substituted oligo(p-phenylene)vinylene(COP)tweezer(DPU).As a control experiment,a class of polyurethanes containing only a single COP moiety(MPU)was also prepared.The DPU showed prominent mechanochromic properties,due to the intramolecular folding–unfolding of COP tweezer under mechanical stimulus.The process was efficient,reversible and optical detectable.However,due to the disability to form either intramolecular folding or intermolecular aggregation,the MPU sample was mechanical inert.

Cationic Conjugated Oligomers for Efficient and Rapid Antibacterial Photodynamic Therapy via Both Type Ⅰ and Type Ⅱ Pathways

Recently,photodynamic therapy(PDT)has attracted wide attention due to its less susceptibility to drug resistance,broad-spectrum biocidal activity and biosafety in normal tissues.However,the traditional photosensitizers(Ps)face the disadvantage of poor therapeutic efficacy due to the requirement of an aerobic environment to generate ^(1)O_(2) through Type Ⅱ pathway.Herein,we designed and synthesized a novel cationic conjugated oligomer oligo(phenylene vinylene)(OPV)and studied its antibacterial photodynamic activity against both Gram-negative Escherichia coli(E.coli)and Gram-positive bacteria methicillin-resistant Staphylococcus aureus(MRSA).Importantly,the OpV can rapidly produce reactive oxygen species(ROs)through double pathways,Type Ⅰ and Ⅱ mechanism under white light irradiation,and efficiently kill E.coli and MRSA at a nanomolar level.The dual type photosensitizing capability makes OPV promising for enhanced PDT to treat pathogens and tumors in complex environments.

Synthesis of aminoisoquinolines via Rh-catalyzed[4+2]annulation of benzamidamides with vinylene carbonate

A new strategy is developed for the synthesis of 1-aminoisoquinoline derivatives.This Rh(III)-catalyzed[4+2]annulation reaction employs benzamidines as efficient directing groups and the vinylene carbonate as an acetylene surrogate.Additionally,the reaction features broad substrate scopes and good yields,only producing carbonate anion as byproduct.

Low-cost and efficient organic solar cells based on polythiopheneand poly(thiophene vinylene)-related donors

At present,most of state-of-the-art power conversion efficiencies(PCEs)of organic solar cells(OSCs)are achieved from the photoactive materials involving donor–acceptor(D–A)copolymer donors.It is well known that the complicated molecular structure of D–A copolymers means the tedious synthesis,which brings about severe cost issue and poor scalability for the industrial production.Therefore,to develop application-oriented OSCs,considerable attention should be paid on simplifying the chemical structures of polymer donors.Polythiophene(PT)and poly(thiophene vinylene)(PTV)derivatives should be among the simplest polymer donors,and OSCs based on them have made some breakthroughs in past 2 years.Here,we briefly introduce the recent advances of OSCs based on low-cost polymers including poly(3-hexylthiophene)(P3HT),PT derivatives,and PTV derivatives,respectively,and emphasize the importance of modulating energy levels,preaggregation effect,and D/A miscibility for the past progress as well as the future development.At last,we also propose some challenges demanding prompt solution for realizing practical application of OSCs,aiming at providing guidance and stimulating new ideas for further research.

Lewis Acid Catalyzed Synthesis of Vinylene Linked Two Dimensional Covalent Organic Frameworks

Comprehensive Summary Vinylene linked covalent organic frameworks(cOFs)have drawn extensive attention due to their desirable stability,carbon conjugation and opto-electronic properties.Suitable catalyst is a key factor in the synthesis of vinylene linked COFs,and proton acids and bases are widely reported as catalysts so far.Herein,we report the synthesis of vinylene linked cOFs using Lewis acid ZnCl2 as catalyst for the first time.Four COFs with hexagonal pores of different sizes are synthesized by the reaction of 2,4,6-trimethyl triazine and a series of aromaticaldehydes.

Covalent Organic Frameworks with trans-Dimensionally Vinylene-linked π-Conjugated Motifs

Vinylene-linked covalent organic frameworks(COFs) are a class of promising porous organic materials that feature fully π-conjugated structures, high crystallinity, permanent porosity, ultrahigh chemical stability, and extraordinary optoelectronic properties. Over the past 5 years, this kind of material has been witnessed rapid development either in chemical synthesis or in potential applications. In this review, we summarize the chemistry to synthesize vinylene-linked COFs, especially the synthetic strategies involving activation of aryl methyl groups for condensation reaction. We then scrutinize the state-of-the-art development in properties and functions of this kind of COFs. Our own opinions on the further development of the vinylene-linked COFs are also presented for discussion.