Search results for "Diamond"

Energy conversion efficiency in betavoltaic cells based on the diamond Schottky diode with a thin drift layer

2020

The HPHT diamond Schottky diode was assembled as a Metal/Intrinsic/p-doped structure betavoltaic cell (BC) with a very thin (1 μm) drift layer and tested under 5–30 keV electron beam irradiation using a scanning electron microscope (SEM). The effect of the β-radiation energy and the backscattering of electrons on the energy conversion was studied. From the results obtained, it is shown that, the efficiency of the investigated BC increases from 1.01 to 3.75% with the decrease of β-particle energy from 30 to 5 keV due to an increase of the electron beam absorption in a thin drift layer. Maximum efficiency is achieved when the electron beam energy is close to the average β-decay energy of 3H. …

The “green” electrochemical synthesis of periodate

2020

Abstract High‐grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost‐efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron‐doped diamond anodes, which are durable, metal‐free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was opti…

Electrochemical C−H Functionalization of (Hetero)Arenes—Optimized by DoE

2020

Abstract A novel approach towards the activation of different arenes and purines including caffeine and theophylline is presented. The simple, safe and scalable electrochemical synthesis of 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) aryl ethers was conducted using an easy electrolysis setup with boron‐doped diamond (BDD) electrodes. Good yields up to 59 % were achieved. Triethylamine was used as a base as it forms a highly conductive media with HFIP, making additional supporting electrolytes superfluous. The synthesis was optimized using Design of Experiment (DoE) techniques giving a detailed insight to the significance of the reaction parameters. The mechanism was investigated by cyclic volt…

Direct electrochemical generation of organic carbonates by dehydrogenative coupling.

2018

Organic carbonates are an important source for polycarbonate synthesis. However, their synthesis generally requires phosgene, sophisticated catalysts, harsh reaction conditions, or other highly reactive chemicals. We present the first direct electrochemical generation of mesityl methyl carbonate by C–H activation. Although this reaction pathway is still challenging concerning scope and efficiency, it outlines a new strategy for carbonate generation.

Diamondoids: functionalization and subsequent applications of perfectly defined molecular cage hydrocarbons

2014

The term “diamondoid” describes cage hydrocarbon molecules that are superimposable on the diamond lattice. Diamondoids that are formally built by face-fusing of adamantane units, namely diamantane, triamantane, tetramantane, etc., have fascinated chemists since the beginning of the last century. The functionalization of these perfectly defined (C,H)-molecules is described here. Thus, diamondoid halides and diamondoid alcohols are first rank precursors for amino and phosphine-substituted diamondoids that have proved to be highly useful in therapeutic applications and metal catalysis, respectively. The extent of functionalization and polyfunctionalization achieved for adamantane and diamantan…

Quantitative measurements of non-covalent interactions with diamond based magnetic imaging

2018

We present a technique employing dielectrophoretic (DEP) manipulation of surface immobilized complexes integrated with a magnetic imaging platform based on nitrogen-vacancy (NV) centers in diamond for the quantitative measurements of non-covalent interactions. The interdigitated microelectrodes closely spaced to the functionalized surface of the diamond plate provide a wide range of applied DEP forces for noninvasive manipulation of various molecular interactions, while the NV layer under the surface reports the unbinding dynamics. Given that biological samples do not present significant magnetic background and do not screen magnetic fields, our approach has many advantages over the fluores…

Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

2000

Optical absorption of the diluted magnetic semiconductor Zn 1-x Co x Se (x = 0.02) has been measured at room temperature under hydrostatic pressure up to 14 GPa in a membrane diamond-anvil cell. We found two absorption features: (i) an absorption structure in the energy range 1.5 to 1.8 eV, with a negligible pressure shift (i.e. (0.45 ± 0.05) meV/GPa) which we have identified as the Co 2+ (3d 7 ) internal transition 4 A 2 (F) → 4 T 1 (P) and (ii) an onset in the energy range 2 to 2.7 eV which redshifts with pressure (dE/dP = (-8.1 ± 0.6) meV/GPa). We have attributed such absorption edge to charge transfer between the ZnSe valence band and the Co 2+ (3d 7 ) levels. On the assumption that tho…

Nanodiamonds: Emergence of Functionalized Diamondoids and Their Unique Applications

2015

ChemInform Abstract: Tuning the Band Gap of PbCrO4Through High-Pressure: Evidence of Wide-to-Narrow Semiconductor Transitions.

2014

Commercial polycrystalline and cleaved platelets from natural PbCrO4 are studied in a diamond anvil cell at ≤ 21 GPa.

Utilisation des minéraux lourds comme indicateurs de paléoplacers alluvionnaires diamantifères en République centrafricaine (RCA). Use of heavy miner…

2001

International audience; Le diamant est la première ressource minérale de la République Centrafricaine (RCA). Exclusivement exploité par plusieurs sociétés minières avant 1960, il l'est maintenant de façon artisanale. Avec une production annuelle d'envi-ron 500 000 carats (1 carat = 0,2 g), la RCA est le dixième producteur de diamant (en valeur) dans le monde. Les diamants gemmes (pierres de joaillerie, taillables) représentent 70 à 75 % de la production. Deux principales zones diamantifères présentant une relation spatiale évidente existent en RCA : la Formation de Mouka-Ouadda à l'Est et celle de Carnot à l'Ouest. Ces formations, représentant les 'roches magasins' du diamant, constituent a…