High Electromagnetic Field Enhancement of TiO2 Nanotube Electrodes

We present the fabrication of TiO₂ nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface‐enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochrome b₅ were observed upon covalent immobilization of the protein matrix on the TiO₂ surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 °C. For the first time, such high values are reported for non‐directly surface‐interacting probes, for which the involvement of charge‐transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode.     

Source apportionment of trace elements in the Eastern Mediterranean atmosphere

Concentrations of elements and ions, measured in aerosol samples collected during 1993 were investigated to identify sources and source composition of aerosols in the Eastern Mediterranean atmosphere. The factor analysis have shown that Eastern Mediterranean aerosol is a four-component system, including a crustal component, long-range transported pollution component, a marine component and a local pollution component. Main anthropogenic component, which reaches to the region by long-range transport accounts for 70%-90% of the concentrations of Zn, Se, NO_3-, nss-SO₄ ^2-, NH₄ ⁺ and smaller fractions of V, Sb, Cr and Mn concentrations. According to the quantitative analysis of local and Saharan dust components, the most promising marker elements to distinguish Saharan dust from local soil were found to be Cr, Nd, Mg and Cs as they have significantly different compositions in the local soil and Saharan dust.     

Hollow polymer shells from biological templates: fabrication and potential applications

Three-dimensional ultrathin polymer shells have been produced by a combination of step-by-step adsorption of polyelectrolytes on glutaraldehyde-treated human erythrocytes and subsequent solubilization of the cytoplasmatic constituents by means of a deproteinizing agent. The obtained hollow films preserve both the size and shape of the templating cells. This opens a pathway for the fabrication of polymeric capsules within a wide range of size and shape by using various biological templates. They may have exciting potential applications, such as templates for nanocomposites, as containers for a large class of materials, or as cages for chemical reactions. The thickness of the films can be adjusted over a large range: from a few nm up to several tens of nm. The polymer shells are permeable to small molecules and ions but not to macromolecules. An increase in the ionic strength of the solution up to 100 mmol make the capsules permeable for proteins. Permeability and conductivity studies have provided evidence that the adsorption of lipids on polyelectrolyte layers is a means of producing capsules with controlled permeability properties. 6-Carboxyfluorescein and Rhodamin 6G were precipitated within the capsules.     

Electron donor-acceptor dyads based on ruthenium(II) bipyridine and terpyridine complexes bound to naphthalenediimide

Two series of photosensitizer-electron acceptor complexes have been synthesized and fully characterized: ruthenium(II) tris(bipyridine) ([Ru(II)(bpy)(2)(bpy-X-NDI)], where X = -CH(2)-, tolylene, or phenylene, bpy is 2,2'-bipyridine, and NDI is naphthalenediimide) and ruthenium(II) bis(terpyridine) ([Ru(II)(Y-tpy)(tpy-X-NDI)], where Y = H or tolyl and X = tolylene or phenylene, and tpy = 2,2':6',2' '-terpyridine). The complexes have been studied by cyclic and differential pulse voltammetry and by steady state and time-resolved absorption and emission techniques. Rates for forward and backward electron transfer have been investigated, following photoexcitation of the ruthenium(II) polypyridine moiety. The terpyridine complexes were only marginally affected by the linked diimide unit, and no electron transfer was observed. In the bipyridine complexes we achieved efficient charge separation. For the complexes containing a phenyl link between the ruthenium(II) and diimide moieties, our results suggest a biphasic forward electron-transfer reaction, in which 20% of the charge-separated state was formed via population of the naphthalenediimide triplet state.     

Synthesis of a (B12H11S) containing glucuronoside as potential prodrug for BNCT

A B₁₂H₁₁SH²⁻ containing glycoside of glucuronic acid has been prepared, for possible use as prodrug in BNCT. The synthesis was carried out by the Koenigs-Knorr reaction of the acetylated glucopyranosyluronate bromide with the nucleophile cyanoethylthioundecahydro-closo-dodecaborate(2−). After removal of the cyanoethyl-group, deacetylation and saponification of the reaction product tris(tetramethylammonium)-[S-(β-d-glucuronate)-thio] undecahydro-closo-dodecaborate(3−) could be prepared.     

LIGHT-INDUCED LINEAR ACTION DICHROISM IN PHOTOREVERSIBLY PHOTOCHROMIC SENSOR PIGMENTS—I. THEORY

Abstract— With a photoreversibly photochromic regulator pigment such as phytochrome, linear action dichroism could theoretically be obtained after photoselection even if the molecules are initially randomly oriented: If randomly oriented P_fr (fed-absorbing phytochrome) molecules are partially converted to P_fr (far-red absorbing phytochrome) molecules by plane-polarized red light, those molecules will preferentially be converted which have their 'red' transition moments nearly parallel to the electric vector of the red light. The effect of subsequent plane-polarized far-red light will depend on the plane of polarization. A general theory is developed for how this can be used to determine whether or not the transition moment changes direction during conversion. The pigment need not be isolated, since only physiological reactions (such as germination or chromatic adaptation) are measured.     

Triplet—triplet absorption spectra of alternant hydrocarbons within the grand canonical time-dependent hartree—fock approximation

Triplet—triplet excitation energies and transition moments have been calculated for some alternant hydrocarbons by the grand canonical time-dependent Hartree—Fock approximation within the Pariser—Parr—Pople model. The main features of the experimental spectra are found to be reproduced more consistently in this scheme than in previously applied models.     

Infrared Spectroscopic Study on the Hofmann-dadn-type and the Td-dahxn-type clathrates

Infrared spectra of M(1,10-diaminodecane)Ni(CN)₄ · 1,5 G (M=Co, Ni or Cd; G=o-xylene, m-xylene, p-xylene) and Cd(l,6-diaminohexane)M(CN)₄ · C₆H₆ (M=Cd or Hg) clathrates are reported. The 1,10-diaminodecane and 1,6-diaminohexane molecules in the host permit the inclusion of bulky guest molecules. The spectral data of clathrates were compared with those of the corresponding host. The spectral features suggest that these compounds are similar in structure to other Hofmann-type and Hofmann-T_d type clathrates, respectively.     

Interaction of Hydrogen with MOF-5

Hydrogen storage is among the most demanding challenges in the hydrogen-based energy cycle. One proposed strategy for hydrogen storage is based on physisorption on high surface area solids such as metal-organic frameworks (MOFs). Within this class of materials, MOF-5 has been the first structure studied for hydrogen storage. The IR spectroscopy of adsorbed H2 performed at 15 K and ab initio calculations show that the adsorptive properties of this material are mainly due to dispersive interactions with the internal wall structure and to weak electrostatic forces associated with O13Zn4 clusters. Calculated and measured binding enthalpies are between 2.26 and 3.5 kJ/mol, in agreement with the H2 rotational barriers reported in the literature. A minority of binding sites with higher adsorption enthalpy (7.4 kJ/mol) is also observed. These species are probably associated with OH groups on the external surfaces present as termini of the microcrystals.