Use of dialkyldithiocarbamato complexes of bismuth(III) for the preparation of nano- and microsized Bi2S3 particles and the X-ray crystal structures of [Bi{S2CN(CH3)(C6H13)}(3)] and [Bi{S2CN(CH3)(C6H13)}(3)(C12H8N2)]

A range of bismuth(III) dithiocarbamato complexes were prepared and characterized. The X-ray crystal structures of the compounds [Bi{S2CN(CH3)(C6H13)}3] (1) and [Bi{S2CN(CH3)- (C6H13)}3(C12H8N2)] (2) are reported. The preparation of Bi2S3 particulates using a wet chemical method and involving the thermalysis of Bi(III) dialkyldithiocarbamato complexes is described. The influence of several experimental parameters on the optical and morphological properties of the Bi2S3 powders was investigated. Nanosized Bi2S3 colloids were obtained having long-term stability and showing a blue shift on the optical band edge; the presence of particles exhibiting quantum size effects is discussed. Morphological welldefined Bi2S3 particles were obtained in which the fiber-type morphology is prevalent.FCT - POCTI/1999/CTM/ 3545

When gold stops glittering: corrosion mechanisms of René Lalique's Art Nouveau jewellery

ABSTRACT: Art Nouveau jewellery created by René Lalique is presently corroded. To identify the corrosion processes, Au-Ag-Cu alloys with compositions comparable to those used in the René Lalique’s jewellery were fabricated to be exposed to sulphide-containing environments. Using SEM-EDS, XRD, UV-Vis spectroscopy and ellipsometry, it was for the first time demon-strated that at the surface of tarnished Au alloys forms a corrosion film with a layer-by-layer structure. Considering the complex refractive indices of bulk Cu and Ag oxides and sulphides, a two-step corrosion mechanism was proposed. The formation of Cu-based compounds during the early corrosion stages is followed by the formation of Ag-based compounds. The thinness of the formed film, shown for one of the gold alloys to be of 80 nm, is due to a corrosion kinetics controlled by the presence of Au and by the formation of an Au-S self-assembled monolayer. The corrosion mechanism of gold alloys raises a new conservation challenge concerning the removal of nanometric layers.info:eu-repo/semantics/publishedVersio

The use of bismuth(III) dithiocarbamato complexes as precursors for the low-pressure MOCVD of Bi2S3

Communication: The potential use of Bi2S3 in thermoelectronic coolers and photodiode arrayshas attracted considerable interest recently. The successful deposition of Bi2S3 by low-pressure MOCVD is reported for the first time. The use of single-source precursors Bi(S2CNEt2)3 and Bi(S2CNMe-nHex)3 produces strongly adhered polycrystalline films on glass substrates at 400–450 °C. XPS and EDX analyses confirm that the deposited film surface is predominantly Bi2S3 and no elemental contamination is detected

Synthesis of PbSe nanocrystallites using a single-source method. The X-ray crystal structure of lead (II) diethyldiselenocarbamate

The compounds PbhSe CN(C H ) j and PbhSe CN(CH )(C H )j were synthesised and characterised. The X-ray crystal structure 2 2 5 2 2 2 3 6 13 2 of PbhSe CN(C H ) j is reported. The use of these compounds as single-molecule precursors to produce PbSe by thermolysis in 2 2 5 2 2 tri-n-octylphosphine oxide was investigated. The optical and morphological properties of the PbSe particulates were analysed; strong quantum confinement effects were observed in the optical spectra of nanodispersed PbSe in organic solvents

Adsorption and catalytic properties of SiO2/Bi2S3 nanocomposites on the methylene blue photodecolorization process

The decolorization of aqueous solutionsmethylene blue (C.I. Basic Blue 9), due to the presence of nanocrystalline Bi2S3, supported on SiO2 submicron particles,was investigated here. For this decolorization process, two distinct characteristics, though related, associated to the role of SiO2/Bi2S3 were identified: (i) high methylene blue adsorption capability and (ii) photocatalytic activity to methylene blue photodecolorization. Effects of experimental parameters on the decolorization process, such as methylene blue and nanocomposite concentrations, pH and Bi2S3 particle size were investigated. The maximum adsorption ability of the SiO2/Bi2S3 was approximately 15.6mg methylene blue per gram. The complete decolorization of a 16ppm organic dye solution can be achieved, by an adsorption process, in an extremely short time (less than 5 min), using 1.6 g/L of SiO2/Bi2S3 nanocomposite. The study of the decolorization of the dye by an adsorption–photoassisted decolorization processwas carried out by irradiation of a suspension prepared with 100mL of methylene blue solution (8 ppm) and 50mg of SiO2/Bi2S3. In these conditions the complete decolorization of the dye, adsorbed and in the solution, was achieved in 40 min.FCT - SFRH/BPD/14554/2003FEDER - POCI/QUI/59615/200

A comparative study on emergent pollutants photo-assisted degradation using ruthenium modified titanate nanotubes and nanowires as catalysts

Several methods have been used to tailor nanomaterials structure and properties. Sometimes, slight changes in the structure outcomes expressive improvements in the optical and photocatalytic properties of semiconductor nanoparticles. In this context, the influence of the metal doping and the morphology on a catalyst performance was studied in this work. Here, ruthenium doped titanate nanotubes (RuTNT) were synthesised for the first time using an amorphous Ru-containing precursor. Afterwards, the photocatalytic performance of this sample was compared to the one obtained for ruthenium titanate nanowires (RuTNW), recently reported. Two samples, RuTNW and RuTNT, were produced using the same Ru-containing precursor but distinct hydrothermal methodologies. The powders were structural, morphological and optical characterized by X-ray diffraction and fluorescence, transmission electron microscopy, Raman, X-ray photoelectron and photoluminescence spectroscopies. Distinct variations on the structural and optical properties of the RuTNT and RuTNW nanoparticles, due to ruthenium incorporation were observed. Their potential use as photocatalysts was evaluated on the hydroxyl radical photo-assisted production. Both samples were catalytic for this reaction, presenting better performances than the pristine counterparts, being RuTNT the best photocatalyst. Subsequently, the degradation of two emergent pollutants, caffeine and sulfamethazine, was studied. RuTNT demonstrated to be better photocatalyst than RuTNW for caffeine but identical performances were obtained for sulfamethazine. For both catalysts, the degradation mechanism of the pollutants was explored through the identification and quantification of the intermediate compounds produced and several differences were found. This indicates the importance of the structural and morphological aspects of a material on its catalytic performance.publishe

Ruthenium-Modified Titanate Nanowires for the Photocatalytic Oxidative Removal of Organic Pollutants from Water

Titanate elongated nanomaterials have been studied as promising catalysts for photoassisted oxidation processes, and various methods have been used to tailor their properties. In this context, the synthesis and photocatalytic evaluation of novel ruthenium-modified titanate nanowires is described. In this work, pristine (TNW) and modified nanowires (RuTNW) were obtained through the hydrothermal treatment of an amorphous precursor, and they were characterized by XRD, Raman, XRF, XPS, TEM, DRS, and PL. The results indicate some alterations on the structure and on the optical properties of these semiconductor nanoparticles, owing to ruthenium incorporation. Regarding the structure, several possible Ru positions can be anticipated: in the TiO6 octahedra, substituting Ti4+, or localized in interstitial sites, or in the interlayers, replacing some Na+. Anticipating their potential use for oxidation photocatalysis, namely, for pollutants removal, the samples were evaluated for hydroxyl radical production, using the probe molecule terephthalic acid. Both samples were catalytic for this photoactivated process, with RuTNW being the best photocatalyst. Afterward, the degradation of caffeine, used as a model pollutant, was evaluated under UV−vis and visible radiation. Regardless of the radiation type in use, a clear improvement on TNW photocatalytic performance was observed after Ru incorporation. In fact, RuTNW was the best catalyst for caffeine photodegradation (20 ppm; 0.13 g/L), with a complete pollutant removal after 60 min, using UV−vis radiation. Through the identification and quantification of the intermediates produced during irradiation, a longer time (more than 120 min) is however required to complete the degradation process. A proposal for the photogenerated charge-transfer mechanism in these photoactivated processes is also given and discussed.publishe

Biotechnologically obtained nanocomposites: A practical application for photodegradation of Safranin-T under UV-Vis and solar light

This research was undertaken to determine the potential of biologically obtained ZnS-TiO2 nanocomposites to be used as catalysts in the photodegradation of organic pollutants, namely, Safranin-T. The photocatalysts were prepared by modifying the surface of commercial TiO2 particles with naturally produced ZnS, using sulfide species produced by sulfate-reducing bacteria and metal contaminated wastewaters. Comparative studies using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), prior and after photodegradation, were carried out in order to monitor possible structural and morphological changes on the particles. Adsorption properties and specific areas were determined by the Brunauer-Emmet-Teller (BET) method. The final solutions were characterized by UV-Vis and chemical oxygen demand (COD) content in order to determine Safranin-T concentration and toxicity. The influence of the catalyst amount, initial pH and dye concentration was also evaluated. Finally, the efficiency of the precipitates as catalysts in sunlight-mediated photodegradation was investigated, performing two scale experiments by using different volumes of dye-contaminated water (150mL and 10 L). All tested composites showed potential to be used as photocatalysts for the degradation of Safranin-T, although the ZnS-TiO2_0.06 composite (0.06g of TiO2 per 50mL of the zinc solution) was the most effective. This substantiates the applicability of these biologically obtained materials as efficient photocatalysts for the degradation of organic pollutants, in laboratorial conditions and under direct sunlight