Ibrahim Issac

Adamantyl‐ and Furanyl‐Protected Nanoscale Silver Sulfide Clusters

The silver salts of 1-adamantanethiol (AdSH) and furan-2-ylmethanethiol (FurCH2 SH) were successfully applied as building blocks for ligand-protected Ag2 S nanoclusters. The reaction of the silver thiolates [AgSAd]x and [AgSCH2 Fur]x with S(SiMe3 )2 and 1,5-bis(diphenylphosphino)pentane (dpppt) afforded three different clusters with 58, 94 and, 190 silver atoms. The intensely colored compounds [Ag58 S13 (SAd)32 ] (1), [Ag94 S34 (SAd)26 (dpppt)6 ] (2), and [Ag190 S58 (SCH2 Fur)74 (dpppt)8 ] (3) were structurally characterized by single-crystal X-ray diffraction and exhibit different cluster core geometries and ligand shells. The diameters of the well-defined sphere-shaped nanoclusters range from 2.2 nm to 3.5 nm.

Synthesis of nanocrystalline solid solutions AlySn1−yO2−y/2 (y = 0.57, 0.4) investigated by XRD, 27Al/119Sn MAS NMR, and Mössbauer spectroscopy

Nanocrystalline AlySn1−yO2−y/2 (y = 0.57, 0.4) was prepared by a co-precipitation method and subsequent calcination at temperatures of up to 650 °C. Transmission electron microscopy and X-ray diffraction reveal crystallite sizes of about 2 nm and a crystal structure equivalent to that of pure SnO2 cassiterite. The local structure was investigated by 27Al and 119Sn NMR as well as by Sn Mossbauer spectroscopy. The results show the formation of a solid solution with a random distribution of Al and Sn on the cation sites and a random distribution of oxygen vacancies on the anion sites.

Synthesis and electrochemical performance of nanocrystalline Al0.4Mg0.2Sn0.4O1.6 and Al0.25Mg0.38Sn0.38O1.5 investigated by in situ XRD, 27Al/119Sn MAS NMR, 119Sn Mössbauer spectroscopy, and galvanostatic cycling

Nanocrystalline Al0.4Mg0.2Sn0.4O1.6 and Al0.25Mg0.38Sn0.38O1.5 were prepared by a co-precipitation method from Al(NO3)3·9H2O, MgSO4, and SnCl4·5H2O, followed by calcination at different temperatures. We performed in situ X-ray diffraction measurements at temperatures between 307 K and 1173 K and transmission electron microscopy. The results reveal a crystal structure equivalent to that of SnO2 cassiterite, very small crystallite sizes of about 3–4 nm, and high thermal stability. The local structure around Al and Sn was investigated by 27Al/119Sn NMR and 119Sn Mossbauer spectroscopy. These measurements show that the calcination results in the formation of [AlO4] and [AlO5] units, in addition to the initial [AlO6] environment, and in local disorder around the Sn atoms. The electrochemical performance was studied by galvanostatic cycling against Li metal. These experiments were performed on bare and carbon coated materials. Sn is the active component in these materials and undergoes an alloying reaction. Both Al0.4Mg0.2Sn0.4O1.6 and Al0.25Mg0.38Sn0.38O1.5 exhibit good electrochemical performance with a very stable cycling and a discharge capacity of 522 mA h g−1 and 385 mA h g−1, respectively, after 100 cycles. Their performance is strongly improved in comparison with pure SnO2 prepared by the same synthesis route.