Advanced High‐Voltage Aqueous Lithium‐Ion Battery Enabled by “Water‐in‐Bisalt” Electrolyte

A new super‐concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra‐high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO₂ as the anode material, and a 2.5 V aqueous Li‐ion cell based on LiMn₂O₄ and carbon‐coated TiO₂ delivered the unprecedented energy density of 100 Wh kg^?1 for rechargeable aqueous Li‐ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the “water‐in‐salt” electrolyte further pushed the energy densities of aqueous Li‐ion cells closer to those of the state‐of‐the‐art Li‐ion batteries.     

Studies on addition of arynyl Grignard reagents to (μ-dithio)bis(tricarbonyliron): —Synthesis,structures and formation mechanism of “open” and “closed” iron-sulfur cluster complexes

Arynylmagnesium bromides cleave the S? S bond of μ-S₂Fe₂(CO)₆ to give equilibrium mixtures of “open” intermediates (μ-ArC≡CS) (μ-BrMgS)Fe₂(CO)₆ and “closed” intermediates μ-[S(Ar)C=C(MgBr)S]Fe₂(CO)₆. The mixtures were treated with CpFe(CO)₂I or some of organic halides to yield corresponding “open” Fe-S complexes, whereas with CF₃CO₂H, gaseous HBr or CH₃HgCl to afford the “closed” ones. The “closed” products were also observed with those alkyl halides which eliminate HX easily. So, this kind of alkyl halides possibly functions as substrates through elimination of HX in reaction courses     

Highly Selective “Turn‐On” Fluorescent and Colorimetric Sensing of Fluoride Ion Using 2‐(2‐Hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one based on Excited‐State Proton Transfer

A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2‐(2‐hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one. This system allows selective “turn‐on” fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited‐state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD‐DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples.     

“Synthetic Metals”: A Novel Role for Organic Polymers (Nobel Lecture)

Since the initial discovery in 1977, that polyacetylene (CH)_x, now commonly known as the prototype conducting polymer, could be p‐ or n‐doped either chemically or electrochemically to the metallic state, the development of the field of conducting polymers has continued to accelerate at an unexpectedly rapid rate and a variety of other conducting polymers and their derivatives have been discovered. Other types of doping are also possible, such as “photo‐doping” and “charge‐injection doping” in which no counter dopant ion is involved. One exciting challenge is the development of low‐cost disposable plastic/paper electronic devices. Conventional inorganic conductors, such as metals, and semiconductors, such as silicon, commonly require multiple etching and lithographic steps in fabricating them for use in electronic devices. The number of processing and etching steps involved limits the minimum price. On the other hand, conducting polymers combine many advantages of plastics, for example, flexibility and processing from solution, with the additional advantage of conductivity in the metallic or semiconducting regimes; however, the lack of simple methods to obtain inexpensive conductive polymer shapes/patterns limit many applications. Herein is described a novel, simple, and cheap method to prepare patterns of conducting polymers by a process which we term, “Line Patterning”.     

[Fe(H2O)5(NO)]2+, the “Brown‐Ring” Chromophore

Although the “brown‐ring” ion, [Fe(H₂O)₅(NO)]²⁺ ( 1 ), has been a research target for more than a century, this poorly stable species had never been isolated. We now report on the synthesis of crystals of a salt of 1 which allowed us to tackle the unique bonding situation on an experimental basis. As a result of the bonding analysis, two stretched, spin‐polarised π‐interactions provide the Fe–NO binding—and challenge the concept of “oxidation state”.     

Effect of Na‐ionomer on dynamic rheological,dynamic mechanical and creep properties of acrylonitrile styrene acrylate (ASA)/Na+1 poly (ethylene‐co‐methacrylic acid) ionomer blend

A special class of engineered copolymers, called ionomers, comprising both electrically neutral repeating units and a fraction of ionized units was melt blended to weather resistant acrylonitrile/styrene/acrylate (ASA) terpolymer for improved electrical conductivity, heat sealing ability, direct adhesion to several polymers, glass and metals without affecting the aesthetics and colorability of ASA. The similar chemical nature of one of the components of each blended materials viz. acrylate rubber in ASA and acrylic acid of Na‐ionomer in addition to the presence of ionic crosslinking within Na‐ionomer, polar acrylonitrile group in ASA affects chain dynamics as compared to neat polymers. In this context, dynamic rheological properties, DMA properties, creep behavior and DSC of the newly developed ASA/Na‐ionomer blends were analyzed. Based on Na‐ionomer content, the blend system either forms “mushroom” or “brush” type conformation and formation of ionic crosslinking in “brush regime” leads to three tiers Caylay tree conformation. The different chain topology resulted into characteristic loss modulous (G″) curve during stress relaxation process. The chain conformation as well as ionic crosslinking and ion–dipole interaction between the blend components also affected DSC endotherm peak and glass transition temperature. The tan δ peak temperature from DMA also revealed the similar observation. The creep compliance of the blends was dependent on Na‐ionomer content and with temperature. The Findley model analysis of creep compliance suggested that the creep compliance was depended on Na‐ionomer content and ionic crosslinking controlled the creep. The findings can be utilized to design weather resistant smart polymer using suitable filler system. Copyright © 2014 John Wiley & Sons, Ltd.     

The Nanoparticle Size Effect in Graphene Cutting: A “Pac‐Man” Mechanism

Metal‐nanoparticle‐catalyzed cutting is a promising way to produce graphene nanostructures with smooth and well‐aligned edges. Using a multiscale simulation approach, we unambiguously identified a “Pac‐Man” cutting mechanism, characterized by the metal nanoparticle “biting off” edge carbon atoms through a synergetic effect of multiple metal atoms. By comparing the reaction rates at different types of edge sites, we found that etching of an entire edge carbon row could be triggered by a single zigzag‐site etching event, which explains the puzzling linear dependence of the overall carbon‐atom etching rate on the nanoparticle surface area observed experimentally. With incorporation of the nanoparticle size effect, the mechanisms revealed herein open a new avenue to improve controllability in graphene cutting.     

The Controlled Formation and Cleavage of an Intramolecular d8–d8 Pt–Pt Interaction in a Dinuclear Cycloplatinated Molecular “Pivot‐Hinge”

The bis(diphenylphosphino)methane (dppm)‐bridged dinuclear cycloplatinated complex {[Pt(L)]₂(μ‐dppm)}²⁺ (Pt₂ ? dppm; HL: 2‐phenyl‐6‐(1H‐pyrazol‐3‐yl)‐pyridine) demonstrates interesting reversible “pivot‐hinge”‐like intramolecular motions in response to the protonation/deprotonation of L. In its protonated “closed” configuration, the two platinum(II) centers are held in position by intramolecular d⁸–d⁸ Pt–Pt interaction. In its deprotonated “open” configuration, such Pt–Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]₂(μ‐dchpm)}²⁺ (Pt₂ ? dchpm) with bis(dicyclohexylphosphino)methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π–π interactions between the phenyl moieties of the μ‐dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt–Pt interaction in Pt₂ ? dppm. In the case of Pt₂ ? dchpm, spectroscopic and spectrofluorometric titrations as well as X‐ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room‐temperature triplet metal–metal‐to‐ligand charge‐transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1‐pyrazolyl‐N moiety and the methylene CH and phenyl C–H of the μ‐dppm. The “open” configuration of the deprotonated Pt₂ ? dppm was estimated to be 19 kcal mol^?1 more stable than its alternative “closed” configuration. On the other hand, the open configuration of the deprotonated Pt₂ ? dchpm was 6 kcal mol^?1 less stable than its alternative closed configuration.     

Developing A “Polysulfide‐Phobic” Strategy to Restrain Shuttle Effect in Lithium–Sulfur Batteries

Inspired by hydrophobic interface, a novel design of “polysulfide‐phobic” interface was proposed and developed to restrain shuttle effect in lithium–sulfur batteries. Two‐dimensional VOPO₄ sheets with adequate active sites were employed to immobilize the polysulfides through the formation of a V?S bond. Moreover, owing to the intrinsic Coulomb repulsion between polysulfide anions, the surface anchored with polysulfides can be further evolved into a “polysulfide‐phobic” interface, which was demonstrated by the advanced time/space‐resolved operando Raman evidences. In particular, by introducing the “polysulfide‐phobic” surface design into separator fabrication, the lithium–sulfur battery performed a superior long‐term cycling stability. This work expands a novel strategy to build a “polysulfide‐phobic” surface by “self‐defense” mechanism for suppressing polysulfides shuttle, which provides new insights and opportunities to develop advanced lithium–sulfur batteries.     

Electrochemiluminescence of Supramolecular Nanorods and Their Application in the “On–Off–On” Detection of Copper Ions

In this work, an “on–off–on” switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu²⁺) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10‐perylenetetracarboxylic acid (PTCA) and aniline. The initial “signal‐on” state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co‐reaction accelerator. In addition, ECL quencher probes (Fc‐NH₂/Cu‐Sub/nano‐Au) were fabricated by immobilizing aminoferrocene (Fc‐NH₂) on Cu‐substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu‐enzyme strand to form Cu²⁺‐specific DNAzyme. Similarly, the “signal‐off” state was obtained by the high quenching effect of Fc‐NH₂ on the ECL of the excited‐state PTCA (¹PTCA*). As expected, the second “switch‐on” state could achieved by incubating with the target Cu²⁺, owing to the Cu²⁺‐specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (ΔI_ECL) before and after incubating with the target Cu²⁺, the prepared Cu²⁺‐specific DNAzyme‐based biosensor was used for the determination of Cu²⁺ concentrations with high sensitivity, excellent selectivity, and good regeneration.     

A concept for bifocal contact‐ or intraocular lenses: liquid single crystal hydrogels (“LSCH”)

The synthesis of liquid single crystal hydrogels (“LSCH”) in suitable molds offers an innovative concept to realize bifocal contact‐ or intraocular‐lenses. LSCH combine the properties required for applications as bifocal ophthalmic lenses: the soft and water‐containing hydrogel enables oxygen permeation and exhibits high birefringence due to the liquid crystalline phase structure built up by rigid rod‐like amphiphiles. Via a photo‐initiated crosslinking reaction of aqueous solutions of monomeric lyotropic liquid crystalline amphiphiles in the macroscopically ordered liquid crystalline state, we obtain optically uniaxially ordered and transparent LSCH. The orientation process and the phase structure of the anisotropic hydrogel is analyzed by deuterium NMR‐spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.     

Thin‐Film Voltammetry of a Lutetium Bisphthalocyanine at Ionic Liquid|Water Interface

At room temperature, tetraoctylphosphonium bromide is a viscous ionic liquid, this gel‐like organic phase can be cast over a basal‐plane graphite electrode (BPGE). Cyclic voltammetry at such a modified electrode, in contact with an aqueous solution have revealed one reversible oxidation and five reversible reduction steps for a Lu^III bisphthalocyanine dissolved in the ionic liquid film, a proof that the highly reactive reduced species were protected from interaction with water in this highly lipophilic phase. It has also been shown that the redox properties are influenced by the ions in the aqueous phase, a property which has been attributed to ion‐pairing effects; obviously, the ion transfers at the organic|aqueous interface has been ignored. Electrochemistry of Lu(III)[(_tBu)₄Pc]₂ (cyclic voltammetry and square wave voltammetry) under similar conditions shows that the nature and concentration of the anion in the aqueous solution in contact with the ionic liquid film influences the potential of the electrode reaction. This can be attributed to variations of the interfacial potential and also because the organic phase is an anion exchanger. Moreover, SWV experiments suggest that the rate of the overall reaction varies with the nature and concentration of the anion of the aqueous electrolyte, which implies that the ion transfer through the organic|aqueous interface is slower than the electron exchange rate of the molecule at the surface of graphite.     

“On‐Droplet” Chemistry: The Cycloaddition of Diethyl Azodicarboxylate and Quadricyclane

Sharpless and co‐workers previously studied the [2σ+2σ+2π] cycloaddition of diethyl azodicarboxylate (DEAD) and quadricyclane and reported that the addition of water to the neat reagents caused an acceleration in the reaction rate, giving birth to what has been called “on‐water” chemistry. We have examined the same reaction in aqueous microdroplets (ca. 5 μm diameter) and find that the cycloaddition reaction is accelerated even further (by a factor of 10²) compared to that of the “on‐water” reaction reported previously. The trends of acceleration in solvents other than water demonstrated by Sharpless and colleagues were replicated in the corresponding microdroplet experiments. We also find that DEAD reacts with itself to form a variety of hydrazine carboxylates and intercept intermediates of this reaction in microdroplets to validate a mechanism proposed herein. We suggest that “on‐droplet” chemistry, similar to “on‐water” chemistry, may be a general process of synthetic interest.     

Terpy(Pt–salphen)2 Switchable Luminescent Molecular Tweezers

The design and synthesis of switchable molecular tweezers based on a luminescent terpy(Pt‐salphen)₂ ( 1 ; terpy=terpyridine) complex is reported. Upon metal coordination, the tweezers can switch from an open “W”‐shaped conformation to a closed “U”‐shaped form that is adapted for selective recognition of cations. Closing of the tweezers by metal coordination (M=Zn²⁺, Cu²⁺, Pb²⁺, Fe²⁺, Hg²⁺) was monitored by ¹H NMR and/or UV/Vis titrations. During the titration, exclusive formation of the 1:1 complex [M( 1 )] was observed, without appearance of an intermediate 1:2 complex [M( 1 )₂]. The crystallographic structure of the 1:1 complex was obtained with Pb²⁺ and showed a distorted helical structure. Selective intercalation of Hg²⁺ cations by the closed “U” form was observed. The tweezers were reopened by selective metal decoordination of the terpyridine ligand by using tris(2‐aminoethyl)amine (tren) as a competitive ligand without modification of the Pt–salphen complex. Detailed photophysical studies were performed on the open and closed tweezers. Structured emission was observed in the open form from the Pt–salphen moieties, with a high quantum yield and a long lifetime. The emission is slightly modified upon closing with 1 equivalent of Zn²⁺ or Hg²⁺, whereas a dramatic quenching was obtained upon intercalation of additional Hg²⁺.     

NMR Analysis of Apo Glutamine‐Binding Protein Exposes Challenges in the Study of Interdomain Dynamics

Glutamine‐binding protein (GlnBP) displays an apo, “open” and a holo, “closed” crystal form, mutually related by a rigid‐body reorientation of its domains. A fundamental question about such large‐scale conformational transitions, whether the closed state exists in the absence of ligand, is controversial in the case of GlnBP. NMR observations have indicated no evidence of the closed form, whereas experimentally validated computations have suggested a remarkable ca. 40 % population. Herein, a paramagnetic NMR strategy designed to detect the putative apo‐closed species shows that a major population of the latter is highly improbable. Further, NMR residual dipolar couplings collected under three anisotropic conditions do not reveal differential domain alignment and establish that the average solution conformation is satisfied by the apo‐open crystal structure. Our results indicate that the computational prediction of large‐scale interdomain motions is not trivial and may lead to erroneous conclusions without proper experimental validation.     

Synthesis and characterization of star graft copolymers with asymmetric mixed “V‐shaped” side chains via “click” chemistry on a hyperbranched polyglycerol core

The star graft copolymers composed of hyperbranched polyglycerol (HPG) as core and well defined asymmetric mixed “V‐shaped” identical polystyrene (PS) and poly(tert‐butyl acrylate) as side chains were synthesized via the “click” chemistry. The V‐shaped side chain bearing a “clickable” alkyne group at the conjunction point of two blocks was first prepared through the combination of anionic polymerization of styrene (St) and atom transfer radical polymerization of tert‐butyl acrylate (tBA) monomer, and then “click” chemistry was conducted between the alkyne groups on the side chains and azide groups on HPG core. The obtained star graft copolymers and intermediates were characterized by gel permeation chromatography (GPC), GPC equipped with a multiangle laser‐light scattering detector (GPC‐MALLS), nuclear magnetic resonance spectroscopy and fourier transform infrared. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1308–1316, 2009     

Far-infrared studies on Nafion and perfluoroimide acid (PFIA) and their alkali salts

The terahertz/far-infrared spectra (<300 cm⁻¹) of perfluorinated sulfonic acid (Nafion NR211 polymer) and perfluoroimide acid (PFIA polymer) and their alkali (M⁺) salts have been analyzed and the results are presented. Pronounced features in the spectra of these ionomers that correlate systematically with the corresponding cation mass are reported and from their spectral position the force constants are derived. The average vibrational force constants for Nafion/M⁺ and PFIA/M⁺ are found to be 54 ± 7 and 39 ± 4 N/m, respectively. Such terahertz/far-infrared signatures probe the detailed structure of the Nafion/M⁺ and PFIA/M⁺ ionic clusters and, in turn, provide benchmarks for elucidating the ionomer “water channels” or water molecules located in the ionomer–water interface upon hydration. Qualitative trends in the vibrational energies of Nafion and PFIA can be explained by consideration of electronic and/or structural (ionic domain-size) effects.     

Dioxa‐[40]decaphyrin(1.0.1.0.0.1.0.1.0.0): An analogue of turcasarin with a “figure‐eight” structure

The synthesis and characterization of two different furan containing analogues of turcasarin, namely 46,51 ‐dioxa‐2,11,15,20,24,33,37,42‐octapropyl‐turcasarin ( 7a ) and 46,51 ‐dioxa‐2,11,24,33‐tetrapropyl‐15,20,37,42‐tetraethyl‐16,19,38,41‐tetramethyl‐turcasarin ( 7b ) are described. While 7a was found to exhibit a “figure eight” structure in solution and in the solid state, 7b is believed to adopt a different, more symmetric conformation is solution.     

A Reference Electrode System for Electrochemical Measurements in Pure Water

A reference hydrogen electrode systems is constructed by employing a strip of proton‐type Nafion membrane as an ion‐conducting “bridge” to connect a reversible hydrogen electrode (RHE) in an acidic solution to an electrochemical system using pure water as electrolyte, in which the working electrode (WE) is placed. Using such a reference electrode system, the potential at the “WE/pure water” interface is equal to the equilibrium hydrogen electrode potential in pure water when the potential difference between RHE and WE is zero, irrespective of the pH value of the acidic solution in the RHE compartment. The accuracy and reproducibility of the WE potential measurements are within 1–2 mV.     

Statistical interpretation of the Amerithrax “morph” assay results

In the Amerithrax investigation PCR‐based “morph assays” were used to link the anthrax letters with the RMR‐1029 flask at USAMRIID. Quantitative data reported for several of these assays are not consistent with Poisson sampling statistics, but instead exhibit “Taylor's Law” behavior where the variance greatly exceeds the mean. A plausible statistical model for this behavior can explain the large number of observed negative and “inconclusive” findings, and implies a high likelihood that a repository sample could contain a “morph” mutant at concentrations well above the nominal detection limit but nonetheless give a negative or inconclusive test result. A Bayesian framework relates the assay results to the probability that a sample actually contains all four morph mutants, even though it tested negative for at least one. The analysis implies that the observed false negative rate actually does not significantly weaken the conclusion that the morph assays correctly excluded all but the stocks derived from RMR‐1029 as possible sources of the letter powders, at least when the test results were unambiguous. These findings expand upon and resolve some of the issues cited in recent reviews, and indicate the importance of developing a rigorous statistical framework for interpreting “morph” assay data.