In this study, the preparation and electrochemical application of a chromium(III) oxide modified carbon paste electrode (Cr-CPE) and a screen printed electrode (SPE), made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 µg·L⁻¹ for Zn(II), 3 and 10 µg·L⁻¹ for Cd(II), 3 and 10 µg·L⁻¹ for Pb(II), 3 and 10 µg·L⁻¹ for Cu(II), and 3 and 10 µg·L⁻¹ for Ag(I), respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 µg·L⁻¹ for Zn(II), 25 µg·L⁻¹ for Cd(II), 3 µg·L⁻¹ for Pb(II) and 3 µg·L⁻¹ for Cu(II). Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters.

Amorphous nanoscopic iron(III) oxide with interesting magnetic properties was prepared by sonolysis of Fe(acac)(3) under Ar in tetraglyme with a small amount of added water. The organics content and the surface area of the Fe(2)O(3) nanoparticles can be controlled with an amount of water in the reaction mixture and it increases from 48 m(2)g(-1) for dry solvent up to 260 m(2)g(-1) when wet Ar is employed. For further monitoring of the particle size and morphology and for the study of the surface, magnetic and thermal properties, the sample with 2 vol.% of H(2)O was chosen. SEM showed nanoscopic composite particles of a uniform size distribution and nearly spherical shapes with an estimated diameter of 20 nm. Such composites are built from amorphous iron(III) oxide nanoparticles (3 nm) embedded in an acetate matrix as proved by TEM and IR spectroscopy. Temperature-dependent Mössbauer spectra demonstrate a very narrow magnetic transition with an unusually low transition temperature around 25K reflecting the system of magnetically non-interacting ultrasmall particles with a narrow size distribution. The in-field (5T) Mössbauer spectrum recorded at 5K shows a minimum change compared to the zero-field spectrum indicating an absence of the long-range magnetic ordering. The composite particles are thermally stable up to 150 degrees C, which is confirmed by DSC, TG, and by the constant surface area. At higher temperatures, acetate groups are removed from the particle surface, which is documented by the increased surface area and disappearance of their IR bands.

A novel non-hydrolytic sol–gel (NHSG) synthesis of mesoporous tin silicate xerogels is presented. The polycondensation between silicon tetraacetate, Si(OAc)₄, and tetrakis(diethylamido)tin, Sn(NEt₂)₄, resulting in acetamide elimination leads to tin silicate xerogels containing Si–O–Sn linkages. The addition of Pluronic P123 or F127 templates provides homogeneous stiff gels that are, after template removal by calcination at 500 °C in air, converted to stable mesoporous silica xerogels with large surface areas (476 m² g⁻¹) and dispersed SnO₂ nanoparticles (6–7 nm). Heat treatment of the as-prepared tin silicate gels in an inert N₂ atmosphere leads to reduction and transformation to Sn nanoparticles (70–150 nm) embedded in a silica–carbon matrix. The composition and morphology of the xerogels, volatile reaction byproducts, and thermal transformations were followed by elemental analyses, IR spectroscopy, thermal analysis TG-DSC, nitrogen adsorption measurements, solid-state NMR spectroscopy, DRUV-vis spectroscopy, electron microscopy, and HT powder XRD. The SnO₂–SiO₂ xerogels were tested as potential catalysts for aminolysis of styrene oxide with aniline and for the Meerwein–Ponndorf–Verley reduction of 4-tert-butylcyclohexanone. The resulting reaction systems displayed good activity and selectivity.

A novel non-hydrolytic sol–gel (NHSG) synthesis of mesoporous aluminosilicate xerogels is presented. The polycondensation between silicon acetate, Si(OAc)₄, and tris(dimethylamido)alane, Al(NMe₂)₃, leads to homogeneous aluminosilicate xerogels containing Si–O–Al linkages through dimethylacetamide elimination. The addition of Pluronic P123 and F127 templates provides stiff gels that are, after calcination at 500 °C, converted to stable mesoporous xerogels with a high surface area (>600 m² g⁻¹) and wormhole-type pores (d = 5.9 nm). The xerogels exhibit high catalytic activity in aminolysis of styrene oxide (82% conversion) with the turnover frequency up to 100.