Preparação de nanocompósitos através do encapsulamento de polímeros condutores em 2H-MoS2 e 1T-TiS2

Nanocomposites obtained by the encapsulation of conducting polymers such as polyaniline and polydiphenylamine in 2H-MoS2 and 1T-TiS2 are synthesized and characterized by X-ray diffraction and infrared spectrophotometry. The synthesis consists in intercalating the layered compound with n-butyllithium and subsequent exfoliation in water and organic solvents. The nanocomposites are obtained by the adsorption of the polymers into the single-layers sulfides and posterior restacking. The X-ray diffraction measurements showed that the organic conducting polymers are encapsulated in mono and bilayers arrangement in a well-ordered fashion to produce single phase compounds.

Estudo da dissolução oxidativa microbiológica de uma complexa amostra mineral contendo pirita (FeS2), Pirrotita (Fe1-xS) e Molibdenita (MoS2)

This work aims to study the oxidation of a complex molybdenite mineral which contains pyrite and pyrrotite, by Acidithiobacillus ferrooxidans. This study was performed by respirometric essays and bioleaching in shake flasks. Respirometric essays yielded the kinetics of mineral oxidation. The findings showed that sulfide oxidation followed classical Michaelis-Menten kinetics. Bioleaching in shake flasks allowed evaluation of chemical and mineralogical changes resulting from sulfide oxidation. The results demonstrated that pyrrotite and pyrite were completely oxidized in A. ferrooxidans cultures whereas molybdenite was not consumed. These data indicated that molybdenite was the most recalcitrant sulfide in the sample.

Estudo da oxidação dos sulfetos sintéticos molibdenita (MoS2) e covelita (CuS) por Acidithiobacillus ferrooxidans via respirometria celular

This paper analyses the oxidation of covellite and molybdenite by Acidithiobacillus ferrooxidans strain LR using respirometric experiments. The results showed that both sulfides were oxidized by A. ferrooxidans, however, the covellite oxidation was much higher than molybdenite. Regarding the kinetic oxidation, the findings revealed that just molybdenite oxidation followed the classical Michaelis-Menten kinetic. It is probably associated with the pathway which these sulfides react to chemistry-bacterial attack, what is influenced by its electronic structures. Besides, experiments conducted in the presence of Fe3+ did not indicate alterations in molybdenite oxidation. Thus, ferric ions seem not to be essential to the sulfide oxidations.

Síntese e caracterização dos nanocompósitos K0,1(PEO)xMoS2 (X= 0,5; 1,2)

The reaction of an aqueous solution of poly(ethylene oxide) (peo - mw 100.000) with a neutral aqueous suspension of single layers of MoS2 was studied. The single layers aqueous suspension was prepared by first intercalating lithium (using n-Butyllithium in n-hexane) and reaction of these ternary compound with water under ultrasound stirring. The suspension was washed several times with water until neutral pH. The suspension was mixed with the PEO aqueous solution in the presence of KCl. Two single phase compounds were obtained with the expansion of 4,8 and 9,0Å, attributed to the solvation of the intercalated potassium cations with mono and double layers, respectively.

Dissulfeto de molibdênio, um material multifuncional e surpreendente

The aim of this work is to review the chemical and physical properties of layered molybdenum disulfide. The three polymorphic/polytypic modifications of the compound were found, the polytypes 2H (molybdenite) and 3R are semiconductors while the polymorph 1T is an electronic conductor. 2H-MoS2 has several important industrial applications as hydrotreatment catalysts, energy storage devices, solar cells, solid lubricants, among others. When intercalated, the 2H phase changes to a distorted 1T phase, producing unstable intercalation compounds that can be exfoliated in solution, producing single layers and consequently nanocomposites. The direct synthesis of the 1T phase produces stable intercalation compounds. Recently molybdenum disulfide was prepared as nanotubes and fulerene-like structures that bring new insights in the investigation of this important material.

Dissulfeto de molibdênio, um material multifuncional e surpreendente: doze anos depois

In 2002, a review article was published in which molybdenum disulfide properties were discussed. The last sentence of the article read as follows: "Based on that described above, we can conclude that in spite of the vast applications of molybdenum disulfide in several industrial branches, many of the potential applications need to be investigated in the future". Since 2002, novel properties of molybdenum disulfide have been described which promise to revolutionize science. The objective of the present review paper was to provide an overview of the processes of 2H-MoS2 exfoliation and properties of the single layers, reported mainly in the last decade.