In phosphorothioate containing dsDNA-oligomers (S-oligomers), one of the two non-bridging oxygen atoms in the phosphate moiety of sugar-phosphate backbone is replaced by sulphur. In this work, electron spin resonance (ESR) studies of one-electron oxidation of several S-oligos by Cl2•− at low temperatures are investigated. Electrophilic addition of Cl2•− to phosphorothioate with elimination of Cl− leads to the formation of a 2-center three-electron σ2σ*1 bonded adduct radical (-P-S∸Cl). In AT S-oligomers with mutiple phosphorothioates, i.e., d[ATATAsTsAsT]2, -P-S∸Cl reacts with a neighboring phosphorothioate to form the σ2σ*1 bonded disulphide anion radical ([-P-S∸S-P-]−). With AT S-oligomers with a single phosphorothioate, i.e., d[ATTTAsAAT]2, reduced levels of conversion of -P-S∸Cl dsDNA [-P-S∸S-P-]− are found. For guanine containing S-oligomers containing one phosphorothioate, -P-S∸Cl results in one-electron oxidation of guanine base but not of A, C, or T thereby leading to selective hole transfer to G. The redox potential of -P-S∸Cl is thus higher than that of G but is lower than those of A, C, and T. Spectral assignments to -P-S∸Cl and [-P-S∸S-P-]− are based on reaction of Cl2•− with the model compound diisopropyl phosphorothioate. The results found for d[TGCGsCsGCGCA]2 suggest that [-P-S∸S-P-]− undergoes electron transfer to the one-electron oxidized G healing the base but producing a cyclic disulfide bonded backbone with a substantial bond strength (50 kcal/mol). Formation of -P-S∸Cl and its conversion to [-P-S∸S-P-]− is found to be unaffected by O2 and this is supported by the theoretically calculated electron affinities and reduction potentials of [-P-S-S-P-] and O2.

SUMMARYGraphite has been used as the negative electrode in lithium-ion batteries for more than a decade. To attain higher energy density batteries, silicon and tin, which can alloy reversibly with lithium, have been considered as a replacement for graphite. However, the volume expansion of these metal elements upon lithiation can result in poor capacity retention. Alloying the active metal element with an inactive material can limit the overall volume expansion and improve cycle life. This paper presents a summary of tin-based materials as negative electrodes. After reviewing attempts to improve and understand the electrochemical behaviour of metallic tin and its oxides, the focus turns to alloys of tin with a transition metal (TM) and, optionally, carbon. To do so, a combinatorial sputtering technique was used to simultaneously prepare many different compositions of Sn-TM-based materials. The structural and electrochemical results of these samples are presented and they show that cobalt is the preferred TM to give optimal performance. Finally, a comparison of a Sn-Co-C negative electrode material prepared by a rapid quenching method (sputtering) with a material prepared by an economical milling method (mechanical attrition) is presented and discussed.

The thermodynamic temperature of the point of inflection of the melting transition of Re-C, Pt-C and Co-C eutectics has been determined to be 2747.84 ± 0.35 K, 2011.43 ± 0.18 K and 1597.39 ± 0.13 K, respectively, and the thermodynamic temperature of the freezing transition of Cu has been determined to be 1357.80 ± 0.08 K, where the ± symbol represents 95% coverage. These results are the best consensus estimates obtained from measurements made using various spectroradiometric primary thermometry techniques by nine different national metrology institutes. The good agreement between the institutes suggests that spectroradiometric thermometry techniques are sufficiently mature (at least in those institutes) to allow the direct realization of thermodynamic temperature above 1234 K (rather than the use of a temperature scale) and that metal-carbon eutectics can be used as high-temperature fixed points for thermodynamic temperature dissemination. The results directly support the developing mise en pratique for the definition of the kelvin to include direct measurement of thermodynamic temperature.

Magnetron cosputter deposited ternary libraries of Sn 1−x−y M x C y ͑M = Ti, V and Co͒ ͑0 Ͻ x Ͻ 0.5 and 0 Ͻ y Ͻ 0.5͒ have been studied structurally and electrochemically using combinatorial and high-throughput methods. Each of the sputtered Sn 1−x M x binary systems shows an amorphous composition range where the specific capacity for lithium decreases with M content. Adding carbon to the amorphous binaries, to make ternaries, causes the precipitation of crystalline Sn in the cases when M = Ti or V, but not when M = Co. We believe this is because stable carbides of Ti and V exist but stable Co carbides do not. The sputtered Sn-Co-C system was found to have a large amorphous range and the initial amorphous atomic arrangement in certain compositions are stable over at least 27 charge-discharge cycles of 600 mAh/g. Crystalline Sn was found to precipitate in composition ranges having competitive specific capacity in the Sn-Ti-C and Sn-V-C libraries causing rearrangement of the atoms during cycling leading to poor capacity retention.

A survey of the structural and electrochemical properties of combinatorially sputter deposited Sn-transition metal alloys ͓Sn 1−x M x ͑0 Ͻ x Ͻ 0.7; M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu͔͒ is reported. Over 512 compositions have been studied. Sputtered libraries of Sn 1−x M x with M = Mn, Fe, Ni, and Cu show no evidence of nanocrystalline or amorphous phases at any composition. By contrast, libraries of Sn 1−x M x with M = Ti, V, Cr, and Co show composition ranges where the films are highly nanostructured or amorphous, suggesting that these elemental combinations are better glass formers. The transition metal contents of the amorphous or nanostructured phase regions are 0.37 Ͻ x Ͻ 0.40 and x Ͼ 0.48 to at least x = 0.65 for M = Ti, x Ͼ 0.39 to at least x = 0.60 for M = V, 0.47 Ͻ x Ͻ 0.73 for M = Cr, and 0.28 Ͻ x Ͻ 0.43 for M = Co. Electrochemical tests using a 64 channel Li/Sn 1−x M x combinatorial electrochemical cell show that the specific capacity of the alloys drops with transition metal content, as expected. The Sn 1−x Co x system shows an amorphous phase with the largest specific capacity, primarily because the amorphous phase is reached at the lowest transition metal content for Sn 1−x Co x . Capacity retention vs cycle number is generally best for those compositions that are amorphous or highly nanostructured. Arguments are presented to suggest that amorphous Sn 1−x V x alloys are the best choice among Sn 1−x M x alloys. Comparison with literature results for samples prepared by mechanical alloying, electrodeposition, vacuum deposition, etc. is made.