Vanadium oxide nanotubes were obtained as the main product in a sol−gel reaction followed by hydrothermal treatment from vanadium(V) alkoxide precursors and primary amines (C n H2 n +1NH2 with 4 ≤ n ≤ 22) or α,ω-diamines (H2N[CH2] n NH2 with 14 ≤ n ≤ 20). The structure of the nanotubes has been characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and magnetic measurements. The tubes are up to 15 μm long and have outer diameters ranging from 15 to 150 nm and inner diameters from 5 to 50 nm. The tube walls consist of 2−30 crystalline vanadium oxide layers with amine or diamine molecules intercalated in between. The distance between the layers (1.7−3.8 nm) is proportional to the length of the alkylamine, which acts as a structure-directing template. The structure within the layers has a square metric with a ≈ 0.61 nm. Cross-sectional TEM images demonstrate the predominance of serpentine-like scrolls rather than of concentric tubes. The intercalated templates can be easily substituted, e.g. by diamines, while the tubular morphology is preserved. This points to a highly flexible structure.

Cross-linked poly(dimethylsiloxane) (PDMS) was irradiated with a Xe2*-excimer lamp (172 nm) under ambient conditions. The irradiation in combination with the formed ozone results in an oxidation of PDMS to SiO2 at the polymer−air interface. The surface properties of the irradiated surfaces were studied by means of contact angle measurements, infrared spectroscopy, and X-ray photoelectron spectroscopy. The photochemical conversion of surface methylsilane groups to silanol groups is responsible for the large increase in surface free energy. Subsequent degradation of the polymer and formation of SiO x was monitored by infrared spectroscopy. As determined by X-ray photoelectron spectroscopy, the binding energy shifts reach values corresponding to SiO2. The atomic ratio concentration O:Si changes from about 1:1 (PDMS) to about 2:1 (SiO2). On the basis of the XPS and IR results, the photochemical reaction pathway from PDMS to silicon oxide via surface silanol groups is discussed. The strict linearity of the contact angle versus irradiation time and the clear dependence from irradiation intensity allows the tuning of the chemical surface functionalities.

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Lithium nickel manganese oxides, LiNi15Mn5O2÷5, (0 y 0.5) were prepared via a new solution technique. The corresponding mixed nickel manganese hydroxide precursors were synthesized in an oxidative coprecipitation method. Subsequent calcination in the presence of LiOH leads to crystalline products with a partially disordered layered-type cs-NaFeO2 structure. X-ray photoelectron spectroscopic analysis has indicated a strong enrichment of lithium at the surface. The electrochemical performance of these materials as positive electrodes in lithium-ion batteries was evaluated as a function of the calcination temperature and manganese content. A calcination temperature of 700°C leads to the best cycling stability. At this temperature, a sufficiently high degree of crystallinity was achieved, having a strong influence on the cycling stability of these "4 V" materials. The specific charge and cycling stability obtained for the solution-prepared pure lithium nickel oxide, LiNiO2, was low, but was significantly enhanced by replacing some nickel with manganese. With increasing manganese content, the specific charge increased to about 170 mAh g' for materials with a Ni:Mn ratio of about 1:1. Ex situ magnetic susceptibility measurements proved that during lithium deinsertion, the trivalent manganese is preferentially oxidized, and seems to be the more reactive redox center in these oxides. InfroductionCurrently interest is focused on the use of lithium transition metal oxides as positive electrode materials in rechargeable high energy density lithium-ion transfer battery systems.'-3 Elemental lithium has been substituted by some forms of carbon as the negative electrode material for safety reasons. Oxides containing highly mobile lithium function as the lithium source in these types of cells. Attention has focused on lithium metal oxides of the form LiMeO2 (Me = Co, Ni), which have the layered cz-NaFeO2 structure type. This structure is shown in Fig. 1 for LiNiO2. In a distorted cubic-closed-packed oxygen array, the lithium and the transition metal atoms are distributed in the octahedral interstitial sites in such a way that Me02 layers are formed. These layers consist of edge sharing [Me06] octahedra of trigonal symmetry. Between these layers, lithium resides in octahedral coordination sites [Li06], leading to alternating lithium and nickel layers along the [111] direction. In a crystal lattice of the space group R3m, oxy-

Self-assembled monolayers have evolved into one of the best established self-assembly systems with high relevance in a scientific and applied context. So far, however, virtually exclusively thiol functional groups have been used for the investigation of fundamental processes on metal surfaces. In this paper, an alternative binding group, the dithiocarbamate (DTC) group, is re-visited. Complete SAM formation with new layer properties characteristically different from thiol SAMs is demonstrated for mono-functional acyclic and bifunctional cyclic dithiocarbamates on Au111 by X-ray photoelectron spectroscopy, cyclic voltammetry, and scanning tunneling microscopy. Furthermore, the chemical adsorption and voltammetric desorption reactions are quantitatively determined. The resonant bi-dentate structure of the DTC provides a characteristically different molecule-metal coupling compared to the thiols and makes the DTC an interesting system for molecular electronics.