Local atomic and electronic structure of quantum dots based on Mn- and Co-doped ZnS

Solid solutions of zinc sulfide with manganese and cobalt are synthesized. Based on the analysis of X-ray diffraction profiles the conclusion is drawn about the formation of a hexagonal wurtzite type structure in the synthesized quantum dot (QD) solutions. The average crystallite sizes are 8 nm and 22 nm for the samples with manganese and cobalt respectively. Results of IR and optical spectroscopy are consistent with the powder X-ray diffraction and X-ray fluorescence data. The question about particle aggregation in isopropanol and DMF solutions is considered. The QD structures based on ZnS particles doped with Mn and Co transition metal atoms are modeled. The possibility to apply X-ray absorption near edge structure (XANES) spectroscopy to verify the atomic structure parameters around the positions of doping transition metal atoms in QDs of the ZnS family is shown. Partial densities of ZnS:Mn and ZnS:Co electronic states are calculated.     

Phase IIb randomized trial of adjunct immunotherapy in patients with first-diagnosed tuberculosis,relapsed and multi-drug-resistant (MDR) TB

Placebo-controlled, randomized, phase 2b trial was conducted in 34 adults comprising 18 first-diagnosed (52.9%), 6 relapsed (17.6%), and 10 MDR-TB (29.4%) cases to investigate the safety and efficacy of an oral immune adjunct (V5). The immunotherapy (N = 24) and placebo (N = 10) arms received once-daily tablet of V5 or placebo for one month in addition to conventional anti-TB therapy (ATT) administered under directly observed therapy (DOT).     

Synthesis and structure modeling of ZnS based quantum dots

Quantum dots (QDs) based on zinc sulfide are synthesized by a microwave method in an aqueous medium using dioctyl sodium sulfosuccinate (DS) or 4,4′-bipyridine (BP). Based on the analysis of X-ray diffraction profiles the conclusion is drawn that QDs obtained have a structure of cubic zinc blende with an average particle size of 5.6 nm for the ZnS_DS sample and 4.8 nm for ZnS_BP. Transmission electron microscopy images show the presence of spherical aggregates of particles only for ZnS_DS. FTIR data indicate the presence of sulfate ions in both samples; DS remains in the sample, facilitating the QD agglomeration, while BP is effectively washed out. From the optical diffuse reflectance spectra the band gap is estimated, which turns out to be larger than the expected one due to the presence of elemental sulfur in the samples and partial oxidation of the QD surface. The QD structure based on ZnS particles is also modeled in the work. The possibility to employ X-ray absorption near-edge spectroscopy for the verification of atomic structural parameters around zinc sites in QDs based on zinc sulfide is demonstrated.     

Simple preparation of diamondoid 1,3-dienes via oxetane ring opening

The transformations of apical mono- and bisacetyl diamondoids to the respective oxetanes and subsequent acid-catalyzed ring opening/dehydration lead to diamondoidyl mono- and bis-1,3-dienes in high preparative yields.     

Preparation and reactivity of metal-containing monomers

The stability constants of some bi- and trivalent metal complexes with methyl-, trifluoromethyl-, and phenyl-substituted 6-heptene-1,3-diones have been determined by pH-metric titration at 20 °C and an ionic strength = 0.1. It is proposed that vinyl groups of ligands are involved in complexation.For Part 44 seeIzv. Akad. Nauk, Ser. Khim., 1995, 1827 [Russ. Chem. Bull., 1995,44, 1758 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2404–2408, December, 1995.This work was partially financially supported by the International Science Foundation (Grant No. NJB000).     

New P2 compound with brucite-like layers: potassium lithiostannate

A new compound with brucite-like layers, K(0.72)Li(0.24)Sn(0.76)O(2), has been obtained two ways, via solid-state reactions: with a big excess of KOH and in a controllable atmosphere without water and carbon dioxide. It has P2 structure (in Hagenmuller's definition) as previously described for K(0.70)Zn(0.35)Sn(0.65)O(2). The latter compound has been repeatedly prepared using the new technique presented here. The structure was refined using powder X-ray profile analysis. Lithium cations are disordered with tin (+4) in the rigid part and introduce "acid" properties. Both types of potassium positions are split. The metastable P3 phase also appears in the K(2)O-Li(2)O-SnO(2) system. The sodium analogue Na(0.72)Li(0.24)Sn(0.76)O(2) with P2 structure has been prepared using an ion-exchange technique.     

Preparative Synthesis of Vinyl Diamondoids

We describe a convenient four-step preparation of 1- vinyl adamantane, 1- vinyl diamantane, and 4,9-divinyl diamantane from the respective diamondoid acetic acids in 50–80% isolated yields involving esterification, reduction, and hydrobromination/dehydrobromination.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Di(adamant-1-yl)- and di(adamant-2-yl)thiophosphoric acids and their triethylammonium salts in alkylation reactions

By reaction of di(adamant-1-yl) and di(adamant-2-yl) phosphites with sulfur in the presence of triethylamine diadamantylthiophosphoric acid triethylammonium salts were obtained. The latter by the action of hydrochloric acid were converted into free thiophosphoric acids and by the reaction of alkylation into the respective triesters which have thionic structure. Applicability in such reactions also of triethylammonium salts of diadamantyldithiophosphoric acids was demonstrated.     

The First Efficient Iodination of Unactivated Aliphatic Hydrocarbons

No heavy metals, no enzymes, and a simple protocol : the direct iodination of aliphatic hydrocarbons, which has not been possible to date, can now be carried out in multiphase systems [see for example Eq. (1)]. In situ generated tetraiodomethane serves as a key intermediate in this selective radical chain reaction initiated by a single electron transfer. This room-temperature, efficient transformation is highly regioselective, easy to work-up, and hence widely applicable.