Why nanoelectrochemistry is necessary in battery research?

The active materials constitute the heart of any battery so that unambiguous determination of their intrinsic properties is of essential importance to achieve progress in battery research. A variety of in situ techniques with high lateral resolution has been developed or adapted for battery research. Surprisingly, nanoelectrochemistry is not attracting sufficient attention from the battery community despite the existing examples of relevant in situ and highly resolved spatiotemporal information. Herein, the important role of nanoelectrochemistry in battery research is highlighted to help encourage its use in this field. In the first part, two examples in which the use of nanoelectrochemistry is a must are provided, that is, determination of intrinsic kinetics of active materials and understanding of relationships between particle structure and electrochemical activity. In the second part, pros and cons of three mature nanoelectrochemistry techniques in battery research, that is, particle-on-a-stick measurements, nanoimpact measurements, and scanning electrochemical probe microscopy, are discussed providing representative examples.     

Why is the linking C-C bond in tetrahedranyltetrahedrane so short?

[structure: see text]. The block-localized wave function (BLW) method has been employed to probe the origin of the very short linking C-C bond (1.436 A) in tetrahedranyltetrahedrane. Computations show that the vicinal hyperconjugative interactions between the two tetrahedranyl groups is stronger than the conjugation in butadiene, and if there were no hyperconjugation effect, the bond distance would be 1.491 A. Thus, both the hybridization mode and hyperconjugative interactions contribute to the shortening of the central C-C bond in tetrahedranyltetrahedrane.     

Why is Stereoregular Polyacrylonitrile Obtained by Polymerization in Urea Canals Isotactic?

Because stereoregular i‐PAN is obtained from the constrained polymerization of acrylonitrile monomer in expandable urea clathrates, we studied the inclusion compounds formed between guest AN and PANs and host cyclodextrins whose rigid channel diameters are in the range of the canals in urea clathrates. ICs of AN were successfully formed with α‐ and γ‐CDs but did not yield PANs, and only ICs between γ‐CD, and a‐ and i‐PANs were formed in solution. Modeling of AN and s‐ and i‐PAN‐CD‐ICs were performed using PM3 parameters to estimate their stabilities. We conclude that the polymerization of AN in urea clathrate channels produces predominantly i‐PAN as a consequence of its improved fit compared with s‐PAN.

     

Why is hydrofluoric acid a weak acid?

The infrared vibrational spectra of amorphous solid water thin films doped with HF at 40 K reveal a strong continuous absorbance in the 1000-3275 cm(-1) range. This so-called Zundel continuum is the spectroscopic hallmark for aqueous protons. The extensive ionic dissociation of HF at such low temperature suggests that the reaction enthalpy remains negative down to 40 K. These observations support the interpretation that dilute HF aqueous solutions behave as weak acids largely due to the large positive reaction entropy resulting from the structure making character of the hydrated fluoride ion.     

Why is Firefly Oxyluciferin a Notoriously Labile Substance?

The chemistry of firefly bioluminescence is important for numerous applications in biochemistry and analytical chemistry. The emitter of this bioluminescent system, firefly oxyluciferin, is difficult to handle. The cause of its lability was clarified while its synthesis was reinvestigated. A side product was identified and characterized by NMR spectroscopy and X‐ray crystallography. The reason for the lability of oxyluciferin is now ascribed to autodimerization of the coexisting enol and keto forms in a Mannich‐type reaction.     

Why is understanding glassy polymer mechanics so difficult?

In this Perspective, I describe recent work on systems in which the traditional distinctions between (i) unentangled versus well‐entangled systems and (ii) melts versus glasses seem least useful, and argue for the broader use in glassy polymer mechanics of two more dichotomies: systems which possess (iii) unary versus binary and (iv) cooperative versus noncooperative relaxation dynamics. I discuss the applicability of (iii–iv) to understanding the functional form of strain hardening. Results from molecular dynamics simulations show that the “dramatic” hardening observed in densely entangled systems is associated with a crossover from unary, noncooperative to binary, cooperative relaxation as strain increases; chains stretch between entanglement points, altering the character of local plasticity. Promising approaches for future research along these lines are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Why is Firefly Oxyluciferin a Notoriously Labile Substance?

The chemistry of firefly bioluminescence is important for numerous applications in biochemistry and analytical chemistry. The emitter of this bioluminescent system, firefly oxyluciferin, is difficult to handle. The cause of its lability was clarified while its synthesis was reinvestigated. A side product was identified and characterized by NMR spectroscopy and X‐ray crystallography. The reason for the lability of oxyluciferin is now ascribed to autodimerization of the coexisting enol and keto forms in a Mannich‐type reaction.     

Why is benzyl‐gem‐diacetate remarkably stable in aqueous solution?

Benzyl‐gem‐diacetate is synthesized and performed its solvolysis in water at 25°C. It did not solvolize even for a year, whereas its counterparts benzyl‐gem‐diazide and dihalides underwent spontaneous cleavage through a S_N1 mechanism in aqueous solution to give benzaldehydes as the final product through α‐azido benzyl and α‐halo benzyl carbocation intermediates, respectively. The possible explanations are offered for the extraordinary stability of the benzyl‐gem‐diacetate in water. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 554–557, 2009     

Application of the ProteomeLab? PF2D protein fractionation system in proteomic analysis for human genetic diseases

Proteomic analysis has been widely used in elucidating the mechanism of diseases. As a classical proteomic approach, two-dimensional gel electrophoresis (2DGE) has been commonly applied in finding differentially expressed proteins through a first dimension of separation by the isoelectric point (pI) of proteins and a second dimension of separation according to the molecular weight (MW) of proteins. Compared to 2DGE, a recently developed commercial system from Beckman Coulter, the two-dimensional protein fractionation (PF2D), separates proteins according to the pI of proteins in the first dimension followed by a second dimension of separation according to the degree of protein hydrophobicity. As a liquid-based fractionation system, PF2D could facilitate the extraction and separation of broader protein categories and improve reproducibility and quantification as well as be less labor-intensive, which are usually identified as limitations of a gel-based 2DGE platform. This review evaluates the applications of the PF2D system and discusses the perspectives and advantages of PF2D in the investigation of cancer and genetic disorders and in protein mapping in human biological fluids and cell cultures.      

Why is formate synthesis insensitive to copper surface structures?

Experiments have revealed that formate synthesis from carbon dioxide and hydrogen is structure insensitive to copper catalyst surfaces, while the reverse formate decomposition reaction is structure sensitive. The present ab initio density functional theory (DFT) calculations show that the reaction of CO2 with surface atomic hydrogen initially leads to the formation of unstable monodentate formate, which has similar adsorption energies on Cu(111), Cu(100), and Cu(110). The structure of the transition state is similar to that of monodentate formate. It is also shown that gaseous CO2 is directly reacted with surface hydrogen, as suggested by previous experiments. The position of the similar transition state and the direct reaction mechanism well explain the similar energetic pathways, that is, the structure insensitivity.     

Why is copper locally etched by scanning electrochemical microscopy?

The etching of thin copper films by scanning electrochemical microscopy (SECM) was investigated. It is not trivial that locally injected charge by an oxidized mediator will lead to dissolution of copper as the charge can easily be dissipated by lateral charge propagation. We studied the effect of different parameters, such as thickness of the Cu film and concentration of the mediator, on the efficiency of etching. The feedback current is the sum of three charge transfer contributions: diffusion of mediator species, chemical reaction on the surface and lateral charge propagation across the copper film. We have introduced an approach for isolating the lateral contribution and studied the parameters affecting the fate of the locally injected charge. We found that etching becomes effective once the lateral contribution cannot dissipate the locally injected charge. This occurs as the concentration of the etchant increases or the film thickness decreases. Measuring the steady-state current above Cu films with different thickness, allowed estimating the potential difference across the Cu area underneath the tip. We conclude that driving local processes, such as etching, depends on creating a mechanism which maintains the injected charge focused.     

How important is the back reaction of electrons via the substrate in dye-sensitized nanocrystalline solar cells?

The role of the conducting glass substrate (fluorine-doped tin oxide, FTO) in the back reaction of electrons with tri-iodide ions in dye-sensitized nanocrystalline solar cells (DSCs) has been investigated using thin-layer electrochemical cells that are analogues of the DSCs. The rate of back reaction is dependent on the type of FTO and the thermal treatment. The results show that this back-reaction route cannot be neglected in DSCs, particularly at lower light intensities, where it is the dominant route for the back transfer of electrons to tri-iodide. This conclusion is confirmed by measurements of the intensity dependence of the photovoltages of DSCs with and without blocking layers. It follows that blocking layers should be used to prevent the back reaction in mechanistic studies in which the light intensity is varied over a wide range. Conclusions based on studies of the intensity dependence of the parameters of DSCs such as photovoltage and electron lifetime in cells without blocking layers, must be critically re-examined.     

Signals of neutropenia in human breath?

Children undergoing systemic chemotherapy often suffer from severe immunosuppression usually associated to severe neutropenia (neutrophils <?0.5 x 10⁹/l). Clinical courses during those periods range from asymptomatic to septic general conditions. Development of septic symptoms can be very fast and life-threatening. Swift detection of risk factors in those patients is therefore needed. So far no early, rapid and reliable marker or tool exists. Ion-Mobility-Spectrometry coupled with a Multi-Capillary-Column (IMS-MCC) can analyze more than 600 volatile components from exhaled air within a few minutes and hence is a potential, rapid detection-tool. As a proof of concept we measured the exhaled breath of 11 patients with neutropenia and 10 healthy controls ranging from 3 to 18 years of age at the time of measurement. Ten milliliters breath samples were taken at the outpatient clinic and analyzed with an onsite IMS-MCC (BreathDiscovery, B&S Analytik, Dortmund, Germany). Dead-space-volume was adapted to two groups (small 250 ml, large 500 ml). Interestingly 59 differing peaks were measured. Eleven were significantly different (p?≤?0.05), three of which highly significant (p?≤?0.01) in Mann-Whitney-Rank-Sum-testing. The corresponding analytes used in the decision tree are 2-Propanol, D-Limonene and Acetone. The analytes with the lowest rank sum identified are 2-Hexanone, Iso-Propylamine and 1-Butanol. Eventually we were able to show a three-step-decision-tree, which discerns the 21 samples except one from each group. Sensitivity was 90 % and specificity was 91 %. Naturally these findings need further confirmation within a bigger population. Our pilot-study proves that Ion-Mobility-Spectrometry coupled with a Multi-Capillary-Column is a feasible rapid diagnostic tool in the setting of a pediatric oncology out-patient clinic for patients 3 years and older. Our first results furthermore encourage additional analysis as to whether patients at risk for septic events during immunosuppression can be diagnosed in advance by rapidly assessing risk factors such as Neutropenia in exhaled breath.     

How is the CH/pi interaction important for molecular recognition?

Ab initio calculations illustrate that CH/pi attractions significantly contribute to host-guest complexation, but are not always a direct factor in molecular recognition.     

Why is metallic Pt the best catalyst for methoxy decomposition?

The decomposition of methoxy on Cu(111), Ag(111), Au(111), Ni(111), Pt(111), Pd(111), and Rh(111) has been studied in detail by the density functional theory calculations. The calculated activation barriers were successfully correlated with the coupling matrix element V 2 ad and the d-band center (ε d ) for the group IB metals and group VIII metals, respectively. By comparison of the activation energy barriers of the methoxy decomposition on different metals, it was found that Pt is the best catalyst for methoxy decomposition. The possible reason why the metallic Pt is the best catalyst has been analyzed from both the energetic data and the electronic structure information, that is, methoxy decomposition on Pt(111) has the largest exothermic behavior due to the closest p-band center of the CH 3 O among all metals after the adsorption.     

Why is the amyloid beta peptide of Alzheimer's disease neurotoxic?

In this article, we support the case that the neurotoxic agent in Alzheimer's disease is a soluble aggregated form of the amyloid beta peptide (Abeta), probably complexed with divalent copper. The structure and chemical properties of the monomeric peptide and its Cu(ii) complex are discussed, as well as what little is known about the oligomeric species. Abeta oligomers are neurotoxic by a variety of mechanisms. They adhere to plasma and intracellular membranes and cause lesions by a combination of radical-initiated lipid peroxidation and formation of ion-permeable pores. In endothelial cells this damage leads to loss of integrity of the blood-brain barrier and loss of blood flow to the brain. At synapses, the oligomers close neuronal insulin receptors, mirroring the effects of Type II diabetes. In intracellular membranes, the most damaging effect is loss of calcium homeostasis. The oligomers also bind to a variety of substances, mostly with deleterious effects. Binding to cholesterol is accompanied by its oxidation to products that are themselves neurotoxic. Possibly most damaging is the binding to tau, and to several kinases, that results in the hyperphosphorylation of the tau and abrogation of its microtubule-supporting role in maintaining axon structure, leading to diseased synapses and ultimately the death of neurons. Several strategies are presented and discussed for the development of compounds that prevent the oligomerization of Abeta into the neurotoxic species.