Hierarchically Structured Nanomaterials for Electrochemical Energy Conversion

Hierarchical nanomaterials are highly suitable as electrocatalysts and electrocatalyst supports in electrochemical energy conversion devices. The intrinsic kinetics of an electrocatalyst are associated with the nanostructure of the active phase and the support, while the overall properties are also affected by the mesostructure. Therefore, both structures need to be controlled. A comparative state‐of‐the‐art review of catalysts and supports is provided along with detailed synthesis methods. To further improve the design of these hierarchical nanomaterials, in‐depth research on the effect of materials architecture on reaction and transport kinetics is necessary. Inspiration can be derived from nature, which is full of very effective hierarchical structures. Developing fundamental understanding of how desired properties of biological systems are related to their hierarchical architecture can guide the development of novel catalytic nanomaterials and nature‐inspired electrochemical devices.     

The decay of153Gd

The sum peak method has been applied to calculate electron capture probability changes to 97 keV and 103 keV levels in the decay of¹⁵³Gd in different environments, e.g., HClO₄ and HNO₃. The relative and absolute intensities of KX-rays and -rays have been measured using a HPGe detector. In addition to these, electron capture intensities and electron capture decay energies (Q _Ec) have also been calculated.     

The Huisgen 1,4-dipolar cycloaddition involving isoquinoline, dimethyl butynedioate and activated styrenes: a facile synthesis of tetrahydrobenzoquinolizine derivatives

A three-component reaction involving isoquinoline, dimethyl butynedioate and electrophilic styrenes is described. The reaction proceeds through a Huisgen 1,4-dipolar cycloaddition pathway.     

Voltammetric determination of molybdenum in brines

Summary The presence of molybdenum in natural water, at the ng/ml level, is essential for the growth of phytoplankton and other organisms, but its presence in brines is reported to affect the current efficiency in electrochemical chlor-alkali production. A voltammetric method, incorporating a preconcentration step, has been developed for the determination of molybdenum at this level in brine and sea-water. Molybdenum is co-precipitated with cadmium sulphide at a pH of about 2. The precipitate is dissolved in aqua regia and fumed with perchloric acid. The residue is dissolved in a supporting electrolyte comprising 1M sodium perchlorate, 0.1M sodium acetate and 0.01M EDTA (pH 6.0±0.2). At this pH, a well-defined wave for the reduction of molybdenum(VI) is obtained at –0.88 Vvs. SCE. None of the common ions interferes. Preconcentration of the molybdenum from 1 litre of brine facilitates its determination down to 1 ng/ml. The estimated precision at the 5 ng/ml level is 13%.

---

Voltammetrische Molybdänbestimmung in Salzwasser

Zusammenfassung Die Anwesenheit von Molybdän in natürlichem Wasser in der Größenordnung von ng/ml ist für das Wachstum von Phytoplankton und anderen Organismen wesentlich, aber, wie berichtet wird, stört seine Anwesenheit in Salzwässern die elektrochemische Produktion von Chlor bzw. Alkali. Eine voltammetrische Methode mit vorangehender Anreicherung wurde für die Molybdänbestimmung in dieser Größenordnung in Salz- und Meerwasser ausgearbeitet. Molybdän wird bei pH etwa 2 mit Cadmiumsulfid mitgefällt. Dieser Niederschlag wird in Königswasser gelöst und mit Perchlorsäure abgeraucht. Der Rückstand wird in einem Trägerelektrolyt mit 1M Natriumperchlorat, 0,1M Natriumacetat und 0,01M ÄDTA (pH 6,0±0,2) gelöst. Bei diesem pH erhält man bei –0,88 V gegen eine ges. Kalomelelektrode für die Reduktion von Mo(VI) eine wohldefinierte Welle. Keines der üblichen Ionen stört. Die Anreicherung des Molybdäns aus 1 Liter Salzwasser erleichtert seine Bestimmung bis zu 1 ng/ml. Die geschätzte Genauigkeit für die Größenordnung 5 ng/ml beträgt 13%.

---

---

Presented at the 8th International Microchemical Symposium, Graz, August 28, 1980.     

Synthesis,characterization, and catalytic oxidation of styrene,cyclohexene, allylbenzene,and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)

Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylenediamine (HyP-Eda) with oxidized chloromethylated polystyrene. Oxidized chloromethylated polystyrene (PS-CHO) was prepared by oxidation of chloromethylated polystyrene (PS) with sodium bicarbonate in DMSO. By reacting DMSO solution of [VO(acac)₂] with polymer-anchored Schiff base ligands I, II, and III, vanadium(IV) complexes PS-[V^IVO(Ae-Eol)] (1), PS-[V^IVO(Hy-Eda)] (2), and PS-[V^IVO(HyP-Eda)] (3) were prepared. Structure and bonding of I, II, and III as well as corresponding vanadium complexes 1, 2, and 3 were confirmed by FT-IR, UV–vis spectroscopy, SEM, EDX, AAS, TGA, EPR, etc. Polymer-anchored vanadium(IV) complexes 1, 2, and 3 show, efficient catalysis toward oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene in the presence of hydrogen peroxide. Optimized reaction conditions for the oxidation of these alkenes was achieved by changing various reaction parameters (like amount of catalyst, amount of oxidizing agent, volume of solvent, etc.). Polymer-grafted 1, 2, and 3 can be reused multiple times without depletion of their activity.     

Bismesitoylphosphinic Acid (BAPO‐OH): A Ligand for Copper Complexes and Four‐Electron Photoreductant for the Preparation of Copper Nanomaterials

Bismesitoylphosphinic acid, (HO)PO(COMes)₂ (BAPO‐OH), is an efficient photoinitiator for free‐radical polymerizations of olefins in aqueous phase. Described here are the structures of various copper(II) and copper(I) complexes with BAPO‐OH as the ligand. The complex Cu^II(BAPO‐O)₂(H₂O)₂ is photoactive, and under irradiation with UV light in aqueous phase, it serves as a source of metallic copper in high purity and yield (>80 %). Simultaneously, the radical polymerization of acrylates can be initiated and allows the preparation of nanoparticle/polymer nanocomposites in which the metallic Cu nanoparticles are protected against oxidation. The determination of the stoichiometry of the photoreductions suggests an almost quantitative conversion from Cu^II into Cu⁰ with half an equivalent of BAPO‐OH, which serves as a four‐electron photoreductant.     

Reductive Amination of Aromatic Aldehydes Using NADH Models

Reductive amination of aromatic aldehydes takes place when treated with equimolar amounts of aromatic amines and NADH model compounds in glacial acetic acid. Imines, the intermediates in the reaction were also reduced by NADH models in acetic acid.     

Design of Peptides with α,β-Dehydro-Residues: Syntheses and Crystal Structures of (i) N-Tertiarybutyloxycarbonyl-L-Ala-ΔPhe-L-Ala-OCH3 and (ii) N-Tertiarybutyloxycarbonyl-L-Leu-ΔPhe-L-Leu-OCH3

In order to contribute to design rules with α,β-dehydro amino acid residues, two peptides (i) Boc-Ala-ΔPhe-Ala-OCH₃ and (ii) Boc-Leu-ΔPhe-Leu-OCH₃ were synthesized and their crystal structures were determined. Peptide (i) with Ala residues on both sides of ΔPhe adopted a type II β-turn conformation with dihedral angles of two corner residues, φ₁ = ?62.6(4)^°, ψ₁ = 138.9(5)^°, φ₂ = 76.3(4)^° and ψ₂ = 13.1(3)^°, while the peptide (ii) with Leu residues formed an unfolded conformation with dihedral angles, φ₁ = ?81.9(5)^°, ψ₁ = ?28.3(4)^°, φ₂ = 56.7(5)^° and ψ₂ = 42.6(4)^°. The structure of peptide (i) was stabilized by an intramolecular 4→1 hydrogen bond between Ala³ NH and BOC carbonyl oxygen atom, whereas that of peptide (ii) was stabilized by van der Waals forces involving the side chains of two Leu residues.     

Rate of excitation energy transfer between fluorescent dyes and nanoparticles

Because of the sensitivity of the rate of Coulomb interaction induced long range resonance energy transfer (RET) on the distance between the donor (D) and the acceptor (A) molecules, the technique of FRET (fluorescence resonance energy transfer) is popularly termed as “spectroscopic ruler” and is increasingly being used in many areas of biological and material science. For example, the phenomenon is used to monitor the in vivo separation between different (bio)polymers/units of (bio)polymers and hence the dynamics of various biomolecular processes. In this work, we examine the distance and the orientation dependence of RET in three different systems: (i) between a conjugated polymer and a fluorescent dye, (ii) between a nanometal particle (NMP) and a fluorescent dye and (iii) between two NMP. We show that in all the three cases, the rate of RET follows a distance dependence of d^−σ where exponent σ approaches 6 at large distance d (Förster type dependence) but has a value varying from 3–4 at short to intermediate distances.