Maria T.C. Sansiviero

Thermal decomposition of sulfur-containing organotin molecular precursors to produce phase-pure SnS

The present work reports a simple route to prepare tin(II) sulfide semiconductor nanometric particles by thermal decomposition in air of the easily prepared organotin sulfur-containing precursors R4Sn4S6 [R = Me, Bun and Ph]. Thermogravimetric (TG) analyses showed that Me and Bun derivatives decompose in a single sharp step at relatively low temperatures to produce the pure SnS phase, which was confirmed by powder X-ray diffraction (XRD). Temperature programmed decomposition-mass spectrometry (TPD/MS) experiments suggested that the decomposition occurs ia reductive elimination steps involving the –R and –S groups. The ring structured R6Sn3S3 [R = Me, Bun, But and Ph] compounds were also studied. However, during thermal decomposition in nitrogen or air tin is partially lost to the gas phase due to sublimation, leaving Sn or SnO, with only traces of SnS.

ZnO/TiO2 semiconductor nanocomposites: photocatalytic tests

Titanium dioxide is an efficient photocatalist, being possible to improve its efficiency with better charge separation which occurs when it is coupled with other semiconductors. Nanometric particles of ZnO were used to impregnate TiO2 P25 in order to optimize its photocatalytic properties. ZnO/TiO2 composites were obtained at different proportions and were characterized by X-ray diffraction (XRD), micro-Raman and diffuse reflectance spectroscopies, measurement of surface area (BET) and scanning electron microscopy (SEM). Raman spectroscopy data revealed a change on the TiO2 surface due the presence of ZnO which was observed by an enlargement of TiO2 peaks and a change on the relation rate between anatase and rutile phases of the composites. The photodegradation of azo-dye Drimaren red revealed better efficiency for ZnO/TiO2 3% nanocomposite and for ZnO pure.

A New Molecular Magnetic Semiconductor Based on Tetrathiafulvalene (ttf) and Oxamato Ligand (opba): (ttf) 2 (Cu(opba))·H 2 O

An oxamato-based compound of formula (ttf) 2 (Cu(opba))·H 2 O, with ttf = tetrathiafulvalene and opba = ortho-phenylenebis(oxamato), has been prepared and characterized. The complex was obtained by metathesis from (ttf) 3 (BF 4 ) 2 and (Bu 4 N) 2 (Cu(opba)) in acetonitrile at room temperature. The UV-Vis-NIR spectrum reveals the presence of the radical cation in two forms, (ttf •+ ) and (ttf •+ ) 2 dimer. The electronic transport properties of (ttf) 2 (Cu(opba))·H 2 O were studied by impedance spectroscopy (IS) and linear voltammetry (LV), and show a typical semiconductor behavior. The EPR spectra exhibit two superposed lines corresponding to electron spins of Cu II

Propriedades elétricas e magnéticas de novos compostos com o ânion condutor [Ni(dmit)2]- e radicais magnéticos nitronil nitróxido

Three compounds have been synthesized with formulae [3-MeRad][Ni(dmit)2] (1), [4-MeRad][Ni(dmit)2] (2) and [4-PrRad][Ni(dmit)2] (3) where [Ni(dmit)2]- is an anionic p-radical (dmit = 1,3-dithiol-2-thione-4,5-dithiolate) and [3-MeRad]+ is 3-N-methylpyridinium a-nitronyl nitroxide, [4-MeRad]+ is 4-N-methylpyridinium a-nitronyl nitroxide and [4-PrRad]+ is 4-N-propylpyridinium a-nitronyl nitroxide. The temperature-dependent magnetic susceptibility of 1 revealed that an antiferromagnetic interaction operates between the 3-MeRad+ radical cations with exchange coupling constants of J1 = - 1.72 cm-1 and antiferromagnetism assigned to the spin ladder chains of the Ni(dmit)2 radical anions. Compound 1 exhibits semiconducting behavior and 3 presents capacitor behavior in the temperature range studied (4 - 300 K).

Thermal decomposition in air of [Bu4N]2[Zn(imnt)2] (bis (1,1 dicyanoethylene-2,2 ditiolate) zincate II of bis tetrabutilamonium) and morphological investigation

Abstract Thermal decomposition in air of [Bu 4 N] 2 [Zn(imnt) 2 ] initially led to the formation of zinc sulfate, and later, to the formation of zinc oxide. Zinc oxide particles were morphologically analyzed showing highly crystalline micron-sized clusters. For the characterization, the following techniques were used: X-ray diffraction, Raman and infrared vibrational spectroscopy and scanning electron microscopy (SEM).