Building Sustainable Saturated Fatty Acid-Zinc Interfacial Layer toward Ultra-Stable Zinc Metal Anodes.

The commercialization pace of aqueous zinc batteries (AZBs) is seriously limited due to the uncontrolled dendrite growth and severe corrosion reaction of the zinc anode. Herein, a universal and extendable saturated fatty acid-zinc interfacial layer strategy for modulating the interfacial redox process of zinc toward ultrastable Zn metal anodes is proposed. The in situ complexing of saturated fatty acid-zinc interphases could construct an extremely thin zinc compound layer with continuously constructed zincophilic sites which kinetically regulates Zn nucleation and deposition behaviors. Furthermore, the multifunctional interfacial layer with internal hydrophobic carbon chains as a protective layer is efficient to exclude active water molecules from the surface and efficiently inhibit the surface corrosion of zinc. Consequently, the modified anode shows a long cycle life of over 4000 h at 5 mA cm-2. In addition, the assembled Zn||V2O5 full cells based on modified zinc anodes have excellent rate performance and long cycle stability.

Reactive Polymer as Artificial Solid Electrolyte Interface for Stable Lithium Metal Batteries.

Lithium (Li) metal anodes have the highest theoretical capacity and lowest electrochemical potential making them ideal for Li metal batteries (LMBs). However, Li dendrite formation on the anode impedes the proper discharge capacity and practical cycle life of LMBs, particularly in carbonate electrolytes. Herein, we developed a reactive alternative polymer named P(St-MaI) containing carboxylic acid and cyclic ether moieties which would in situ form artificial polymeric solid electrolyte interface (SEI) with Li. This SEI can accommodate volume changes and maintain good interfacial contact. The presence of carboxylic acid and cyclic ether pendant groups greatly contribute to the induction of uniform Li ion deposition. In addition, the presence of benzyl rings makes the polymer have a certain mechanical strength and plays a key role in inhibiting the growth of Li dendrites. As a result, the symmetric Li||Li cell with P(St-MaI)@Li layer can stably cycle for over 900 h under 1 mA cm-2 without polarization voltage increasing, while their Li||LiFePO4 full batteries maintain high capacity retention of 96 % after 930 cycles at 1C in carbonate electrolytes. The innovative strategy of artificial SEI is broadly applicable in designing new materials to inhibit Li dendrite growth on Li metal anodes.

Photoresponsive, Water-Soluble Supramolecular Dendronized Polymer with Specific Lysosome-Targetable Bioimaging Application in Living Cells.

A novel photoresponsive, water-soluble supramolecular dendronized polymer (SDP) is prepared through a γ -cyclodextrin (γ -CD)-coumarin host-guest interaction. The supramolecular formation, photoresponsive process, and fluorescence properties are investigated by nuclear magnetic resonance (NMR) techniques and spectrometric measurements. Upon different-wavelength light irradiation, this supramolecular polymer undergoes noncovalent polymer and covalent polymer conversion due to coumarin cycloaddition and cleavage reactions. In addition, SDP for bioimaging in Michigan Cancer Foundation-7 (MCF-7) cells is performed and results show that the obtained SDP has good biocompatibility and is lysosome-targetable. This research enriches the field of supramolecular dendrimers and the photo-stimulation response material may have application prospects in organelle-targeting applications.

Morphologies Transformation of BODIPY-Based Main Chain Supramolecular Polymers Amphiphiles: From Helical Nanowires to Nanosheets.

The aggregate morphologies of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) main chain supramolecular polymer amphiphiles (SPA) are tunable by a fine balance of different non-covalent interactions. When the BODIPY segments and sodium cholate are mixed in aqueous solution, they form SPA by electrostatic attraction and hydrogen-bonds. This SPA displays helical nanowires' morphology. After the third component dimeric ß-cyclodextrin (ß-CD-C) is added, the hydrogen bonds between the cholate are substituted by the host-guest interaction between cholate and ß-CD-C. Therefore, these SPA transform their aggregate morphologies into nanosheets' architecture. Therefore, a simple and effective way to regulate self-assembly by non-covalent forces is developed. This supramolecular method may provide an effective way to prepare various nanostructures in aqueous solution and show promising application in the future.

Amphiphilic BODIPY derivatives: the solvophobic effect on their photophysical properties and bioimaging in living cells.

Three novel amphiphilic BODIPY derivatives were prepared and their photophysical properties in THF/water mixtures with varying fractions of water were investigated. BDP-1 could self-assemble into different vesicle architectures in aqueous solution, while BDP-2 and BDP-3 with more hydrophilic abilities formed spherical and worm-like micelles. The BODIPY derivatives could be absorbed by HeLa cells and showed no apparent toxicity during the course of the test. In particular, unlike traditional amines or morpholinyl functionalized lysosome fluorescent probes, BDP-1 nanovesicles without targeted groups exhibit red emission and show effective lysosome biological imaging. Co-staining experiments with lysosome specific trackers further confirmed the disassembly of BDP-1 nanovesicles in lysosomes. This research provides a new avenue of using probes without targeting the structural unit to stain special organelles and shows potential applications in cell imaging fields.

A ferrocene-azobenzene derivative showing unprecedented phase transition and better solubility upon UV irradiation.

The ferrocene-aspartic acid-azobenzene derivative 1 showing an unprecedented photoinduced crystal-liquid phase transition at an elevated temperature and better solubility in organic solvents has been successfully reported.

BODIPY-based fluorescent thermometer as a lysosome-targetable probe: how the oligo(ethylene glycols) compete photoinduced electron transfer.

A novel BODIPY-based fluorescent thermometer, which shows a lysosome-targeting property, was successfully prepared. Due to the electron-donating ability of the oligo(ethylene glycols), the photoinduced electron-transfer pathway from morpholine to BODIPY dye is blocked. The fluorescence of the thermometer quenched by intramolecular rotation at room temperature was progressively enhanced during heating due to the increased microviscosity around the fluorophore.

BODIPY-based oligo(ethylene glycol) dendrons as fluorescence thermometers: when thermoresponsiveness meets intramolecular electron/charge transfer.

The temperature-dependent photophysical properties of a series of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives with different oligo(ethylene glycol) (OEG) dendrons were investigated. Weak fluorescence emission was observed for these BODIPY derivatives in dilute solution with low viscosity. BDP-G0 and BDP-G1-TEG exhibit a high quantum yield in viscous glycerol solutions, contrary to the moderate and little fluorescence enhancement for BDP-G1 and BDP-G2 under the same conditions. The photoinduced electron transfer (PET) may have quenched the fluorescence, as supported by calculation. Interestingly, the thermoresponsive BODIPY derivatives show heat-induced luminescence enhancement with a high signal-to-noise ratio and their emission maxima are dependent on the structures of branched tri(ethylene glycol) moieties. Finally, preliminary studies on the BODIPY derivatives as intracellular fluorescence indicators in living HeLa cells were carried out.

Functional Polymers as Artificial Solid Electrolyte Interfaces for Stabilizing Lithium Metal Anode.

The practical implementation of the lithium metal anode (LMA) has long been pursued due to its extremely high specific capacity and low electrochemical equilibrium potential. However, the unstable interfaces resulting from lithium ultrahigh reactivity have significantly hindered the use of LMA. This instability directly leads to dendrite growth behavior, dead lithium, low Coulombic efficiency, and even safety concerns. Therefore, artificial solid electrolyte interfaces (ASEI) with enhanced physicochemical and electrochemistry properties have been explored to stabilize LMA. Polymer materials, with their flexible structures and multiple functional groups, offer a promising way for structurally designing ASEIs to address the challenges faced by LMA. This Concept demonstrates an overview of polymer ASEIs with different functionalities, such as providing uniform lithium ion and single-ion transportation, inhibiting side reactions, possessing self-healing ability, and improving air stability. Furthermore, challenges and prospects for the future application of polymeric ASEIs in commercial lithium metal batteries (LMBs) are also discussed.

Near-Infrared BODIPY Photosensitizer for Modulating Mitochondrial Fusion Proteins and Inhibiting Choroidal Neovascularization.

Photosensitizers have emerged as cytotoxic reactive oxygen species (ROS) activators in photodynamic therapy (PDT), which induced cell apoptosis. As the major contributors to ROS and oxidative stress, mitochondria play an important role in cell apoptosis. Although there are many reports about near-infrared 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as photosensitizers (PSs) for PDT, this kind of PS has rarely been used for treating mitochondrial function and choroidal neovascularization application at the same time. Herein, a novel near-infrared PS (BDP2) characterized by good water solubility, long wavelength excitation, and high ROS quantum yield has been made. Under near-infrared light irradiation, BDP2 would generate ROS with high yield, induce a mitochondrial morphology change, and trigger cell apoptosis by changing the fusion protein level. Deep investigation revealed that BDP2 can cause oxidative stress, break the balance between fusion and fission of mitochondrial dynamics protein through decreasing fusion protein MFN2 and OPA1 expression, and finally cause cell apoptosis. Due to these characteristics, the BDP2 PS was used to treat choroidal neovascularization in animal models and can inhibit neovascularization.

Stabilizing Lithium Metal Batteries by Synergistic Effect of High Ionic Transfer Separator and Lithium-Boron Composite Material Anode.

The development of lithium (Li) metal batteries (LMBs) has been limited by problems, such as severe dendrite growth, drastic interfacial reactions, and large volume change. Herein, an LMB (8AP@LiB) combining agraphene oxide-poly(ethylene oxide) (PEO) functionalized polypropylene separator (8AP) with a lithium-boron (LiB) anode is designed to overcome these problems. Raman results demonstrate that the PEO chain on 8AP can influence the Li+ solvation structure in the electrolyte, resulting in Li+ homogeneous diffusion and Li+ deposition barrier reduction. 8AP exhibits good ionic conductivity (4.9 × 10-4 S cm-1), a high Li+ migration number (0.88), and a significant electrolyte uptake (293%). The 3D LiB skeleton can significantly reduce the anode volume changes and local current density during the charging/discharging process. Therefore, 8AP@LiB effectively regulates the Li+ flux and promotes the uniform Li deposition without dendrites. The Li||Li symmetrical cells of 8AP@LiB exhibit a high electrochemical stability of up to 1000 h at 1 mA cm-2 and 5 mAh cm-2. Importantly, the Li||LiFePO4 full cells of 8AP@LiB achieve an impressive 2000 cycles at 2C, while maintaining a high-capacity retention of 86%. The synergistic effect of the functionalized separator and LiB anode might provide a direction for the development of high-performance LMBs.

Experimental investigation on the mechanism of chelation-assisted, copper(II) acetate-accelerated azide-alkyne cycloaddition.

A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)(2)) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and (1)H NMR assays are developed for monitoring the reaction progress in two different solvents, methanol and acetonitrile. Solvent kinetic isotopic effect and premixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)(2) suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)(2) in mediating a 2-picolylazide-involved AAC reaction than the fully reduced Cu(OAc)(2). Finally, the discontinuous kinetic behavior that has been observed by us and others in copper(I/II)-mediated AAC reactions is explained by the likely catalyst disintegration during the course of a relatively slow reaction. Complementing the prior mechanistic conclusions drawn by other investigators, which primarily focus on the copper(I)/alkyne interactions, we emphasize the kinetic significance of copper(I/II)/azide interaction. This work not only provides a mechanism accounting for the fast Cu(OAc)(2)-mediated AAC reactions involving chelating azides, which has apparent practical implications, but suggests the significance of mixed-valency dinuclear copper species in catalytic reactions where two copper centers carry different functions.

Balance between fluorescence enhancement and association affinity in fluorescent heteroditopic indicators for imaging zinc ion in living cells.

A fluorescent heteroditopic indicator for the zinc(II) ion possesses two different zinc(II) binding sites. The sequential coordination of zinc(II) at the two sites can be transmitted into distinct fluorescence changes. In the heteroditopic ligand system that our group developed, the formations of mono- and dizinc(II) complexes along an increasing gradient of zinc(II) concentration lead to fluorescence enhancement and an emission bathochromic shift, respectively. The extents of these two changes determine the sensitivity and, ultimately, the effectiveness of the heteroditopic indicator in quantifying zinc(II) ion over a large concentration range. In this work, a strategy to increase the degree of fluorescence enhancement upon the formation of the monozinc(II) complex of a heteroditopic ligand under simulated physiological conditions is demonstrated. Fluorination of the pyridyl groups in the pentadentate N,N,N'-tris(pyridylmethyl)ethyleneamino group reduces the apparent pK(a) value of the high-affinity site, which increases the degree of fluorescence enhancement as the monozinc(II) complex is forming. However, fluorination impairs the coordination strength of the high-affinity zinc(II) binding site, which in the triply fluorinated ligand reduces the binding strength to the level of the low-affinity 2,2'-bipyridyl. The potential of the reported ligands in imaging zinc(II) ion in living cells was evaluated. The subcellular localization properties of two ligands in five organelles were characterized. Both benefits and deficiencies of these ligands were revealed, which provides directions for the near future in this line of research.

Supramolecular Engineering Strategy to Construct BODIPY-Based White Light Emission Materials.

Two kinds of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyads BDP-OH containing 4-hydroxystyrene groups and BDP-PY bearing pyridinyl units were prepared. In addition, a naphthalene derivative NAP-PY modified by pyridinyl moieties substituent was made. The above three dyads could be used to construct white-light emission (WLE) material by a supramolecular engineering strategy due to their three primary colors of blue, green and red. The supramolecular correlations between the hydroxyl group of BDP-OH and the pyridinyl groups of NAP-PY and BDP-PY were confirmed by 1 H NMR titration, 2D NOESY and FTIR. A fluorescence monitor application was carried out based on the realization of WLE. This work might be useful for designing other WLE supramolecular systems and image display.

Chelation-assisted, copper(II)-acetate-accelerated azide-alkyne cycloaddition.

We described in a previous communication a variant of the popular Cu(I)-catalyzed azide-alkyne cycloaddition (AAC) process where 5 mol % of Cu(OAc)(2) in the absence of any added reducing agent is sufficient to enable the reaction. 2-Picolylazide (1) and 2-azidomethylquinoline (2) were found to be by far the most reactive carbon azide substrates that convert to 1,2,3-triazoles in as short as a few minutes under the discovered conditions. We hypothesized that the abilities of 1 and 2 to chelate Cu(II) contribute significantly to the observed high reaction rates. The current work examines the effect of auxiliary ligands near the azido group other than pyridyl for Cu(II) on the efficiency of the Cu(OAc)(2)-accelerated AAC reaction. The carbon azides capable of binding to the catalytic copper center at the alkylated azido nitrogen in a chelatable fashion were indeed shown to be superior substrates under the reported conditions. The chelation between carbon azide 11 and Cu(II) was demonstrated in an X-ray single-crystal structure. In a limited set of examples, the ligand tris(benzyltriazolylmethyl)amine (TBTA), developed by Fokin et al. for assisting the original Cu(I)-catalyzed AAC reactions, also dramatically enhances the Cu(OAc)(2)-accelerated AAC reactions involving nonchelating azides. This observation leads to the hypothesis of an additional effect of chelating azides on the efficiencies of Cu(OAc)(2)-accelerated AAC reactions, which is to facilitate the rapid reduction of Cu(II) to highly catalytic Cu(I) species. Mechanistic studies on the AAC reactions with particular emphasis on the role of carbon azide/copper interactions will be conducted based on the observations reported in this work. Finally, the immediate utility of the product 1,2,3-triazole molecules derived from chelating azides as multidentate metal coordination ligands is demonstrated. The resulting triazolyl-containing ligands are expected to bind with transition metal ions via the N(2) nitrogen of the 1,2,3-triazolyl group to form nonplanar coordination rings. The Cu(II) complexes of bidentate T1 and tetradentate T6 and the Zn(II) complex of T6 were characterized by X-ray crystallography. The structure of [Cu(T1)(2)(H(2)O)(2)](ClO(4))(2) reveals the interesting synergistic effect of hydrogen bonding, π-π stacking interactions, and metal coordination in forming a one-dimensional supramolecular construct in the solid state. The tetradentate coordination mode of T6 may be incorporated into designs of new molecule sensors and organometallic catalysts.

Chemical anchoring of SeS2 on a fluoro-substituted covalent organic framework as a high-performance cathode material.

In this work, a high-performance cathode material was achieved by using SeS2 post-functionalization of a fluorinated covalent organic framework (COF) through SNAr chemistry. The chemical and physical confinement of polysulfides and polyselenides combined with enhanced conductivity boosted its electrochemical performance as a cathode material for lithium-sulfur batteries (LSBs). COF-F-SeS2 delivered a discharge capacity of 1633 mA h g-1 at 0.1C, an excellent C-rate performance of 1163 mA h g-1 at 1C and favorable long cycle performance. This work provides a feasible strategy to overcome the bottlenecks of LSBs for high capacity, excellent C-rate performance and enhanced cycle performance.

BODIPY-based Carbonaceous Materials for High Performance Electrical Capacitive Energy Storage.

Incorporation of heteroatoms into carbon materials is crucial to tailor carbon materials' donor-acceptor properties and consequently tune their chemical and electrical performance. However, doping carbon materials with multi-heteroatoms (three or more, especially the light elements) has been rarely payed attention until now. In this work, we develop a porous organic polymer containing boron, nitrogen, fluorine elements and realize its corresponding carbonaceous materials by subsequent carbonation or KOH activation process. Electrochemical measurements results reveal that KOH activation sample (BPOP-700A) is endowed with excellent specific capacitance of 408 F g-1 in three-electrode system and an energy density over 19.2 Wh kg-1 in two-electrode system at aqueous electrolyte, which can be attributed to multi light elements (boron, nitrogen and trace fluorine) doping, favorable morphology and rational pore size distribution architecture. In addition, BPOP-700A displays well rate ability and outstanding cycle performance (10 A g-1 , 10 000 cycles, 95 % retention). Our work might give some hints in designing multi light element doping carbon materials in supercapacitor applications.

Synthesis and Morphology Evolution of Ultrahigh Content Nitrogen-Doped, Micropore-Dominated Carbon Materials as High-Performance Supercapacitors.

Nitrogen-doped carbon-based materials including nanocarbons, graphene, and conductive polymers are impressive as supercapacitor electrodes. However, ultrahigh nitrogen contents, micropore dominated, and morphology evolving carbonaceous electrodes have not achieved until now which are crucial for supercapacitor. Herein, we prepare a novel fumaronitrile (FUM) derived covalent triazine framework (FUM-CTF) and activated it by using KOH at different temperatures to obtain the corresponding carbon materials, which were used as supercapacitor electrode materials. Specially, the FUM-700 (sample activated at 700 °C) possesses an excellent specific capacitance of 400 F g-1 at a current density of 1 A g-1 and considerable energy density over 18 Wh kg-1 in KOH (6 m) aqueous electrolyte. In addition, this electrode shows 260 F g-1 at a current density of 20 A g-1 for charge/discharge operation. Furthermore, the FUM-700 electrode demonstrates extraordinary electrochemical stability with 97 % retention after 10 000 cycles at 10 A g-1 . Ultrahigh nitrogen contents, the microporous structure, and the inner nanoparticle morphology work in concert to contribute to the superior electrochemical performance of FUM-700. Our work might give some hints to help design other high-performance nitrogen-containing supercapacitor electrode materials.

Highly Fluoro-Substituted Covalent Organic Framework and Its Application in Lithium-Sulfur Batteries.

We report the preparation of a highly fluoro-substituted crystalline covalent organic framework (COF) and its application as a cathode material in lithium-sulfur batteries (LSBs) upon sulfur confinement. A sulfur-functionalized COF with high sulfur content (60 wt %) was obtained through physisorption of elemental sulfur and subsequent SNAr reaction of sulfur with aromatic fluorides on the COF backbone. After such physical and chemical confinement of sulfur through a postfunctionalization approach, the COF material still shows some structural order, allowing us to investigate the structure-property relationship of such COF materials in LSB application. We compared the electrochemical performances of the two cathode materials prepared from a crystalline COF and its amorphous counterpart and studied the important factors that affect battery capacity, reaction kinetics, and cycling stability.

BODIPY-Based Conjugated Porous Polymer and Its Derived Porous Carbon for Lithium-Ion Storage.

Conjugated porous polymers (CPPs) possess great potential in the energy storage aspect. In this work, a boron-dipyrromethene (BODIPY)-conjugated porous polymer (CPP-1) is achieved by a traditional organic synthesis route. Following this, a carbonization process is employed to obtain the carbonized porous material (CPP-1-C). The two as-prepared samples, which are characterized by doping with heteroatoms and their porous structure, are able to shorten the lithium-ion pathways and improve the lithium-ion storage property. Then, CPP-1 and CPP-1-C are applied as anode materials in lithium-ion batteries. As expected, long-term cyclic performances at 0.1 and 1 A g-1 are achieved with maintaining the specific capacity at 273.2 mA h g-1 after 100 cycles at 0.1 A g-1 and 250.8 mA h g-1 after 300 cycles at 1 A g-1. The carbonized sample exhibits a better electrochemical performance with a reversible specific capacity of 675 mA h g-1 at 0.2 A g-1. Moreover, the capacity is still stabilized at 437 mA h g-1 after 500 cycles at 0.5 A g-1. These results demonstrate that BODIPY-based CPPs are capable of being exploited as promising candidates for electrode materials in the fields of energy storage and conversion.