Intercalation and electrical behavior of Ta xMo1-xS2 (x > 0.5) layered mixed disulfides

Abstract

Este trabalho relata um estudo sistemático do comportamento estrutural e elétrico de três fases ternárias do sistema Ta x Mo 1-x S 2 (x = 0,55, 0,75 e 0,90) e de seus compostos de intercalação resultantes das inserções química e eletroquímica de lítio, assim como das intercalações de piridina e poli(óxido de etileno). As três fases foram preparadas pela reação direta de seus elementos constituintes, sem qualquer outro aditivo, a 900 o C em atmosfera inerte. Os compostos resultantes foram caracterizados por meio de difratometria de raios X de pó (XRD), análises termogravimétrica e térmica diferencial (TGA/DTA), fluorescência de raios X por dispersão de energia (EDX) e microscopia eletrônica de varredura com emissão de campo (FE-SEM). A condutividade elétrica dos diferentes compostos preparados foi medida no intervalo de temperatura 1,5-300 K utilizando o método convencional de sonda de quatro pontas van der Pauw na presença de um campo magnético de 9 T para verificar a ocorrência do fenômeno de magnetoresistividade.This work reports a systematic study of the structural and electrical behavior of three ternary phases of the Ta x Mo 1-x S 2 system (x = 0.55, 0.75 and 0.90) and their intercalation compounds resulting from both chemical and electrochemical lithium insertions, as well as from pyridine and poly(ethylene oxide) intercalations. The three ternary phases were prepared by direct reaction of their constituting elements, without any other additive, at 900 ºC in inert atmosphere. The resulting compounds were characterized by means of X-ray powder diffractometry (XRD), thermogravimetric and differential thermal (TGA/DTA) analyses, energy dispersive X-ray fluorescence (EDX) and field emission-scanning electron microscopy (FE-SEM). The electrical conductivity of the different products was measured in the 1.5-300 K temperature range using the conventional four probe van der Pauw method in the presence of a 9 T magnetic field in order to verify the occurrence of magnetoresistivity phenomena. Keywords: chalcogenides, intercalation, pyridine, PEO, conductivity IntroductionThe renewed interest to study layered solids is originated from the observation of unusual physical properties associated with anisotropy phenomena in such type of low-dimensional materials. Another important reason why 2D solids are investigated is their ability to intercalate a large variety of compounds. [1][2][3][4][5][6][7][8][9] In this context, physical properties such as electrical conductivity and electrochemical behavior of layered solids can be deliberately modified by intercalation of organic species. [2][3][4]10,11 Among different 2D solids, the study of layered transition-metal dichalcogenides (LTMDs) has become the subject of an active field of research in solid state physics and chemistry during the last decades. 1,12,13 One of the most salient physical properties of these materials is their electrical conductivity (and superconductivity) behavior, which is related to phase transitions usually driven by charge density wave mechanisms...

An ion-selective crown ether covalently grafted onto chemically exfoliated MoS2 as a biological fluid sensor

“…33 In the field of transition metal dichalcogenides, to the best of our knowledge, crown ethers have been only utilized as Li ions-containing intercalants within MoS2 exfoliated nanosheets serving as potential electrochemical switches. 34,35 The selective recognition of cations by tuning the size of the oxygencontaining macrocycles offers the advantage of developing responsive electrochemical platforms based on the host-guest interactions, arising from the stabilization of the cations within the macrocyclic polyether tether. Furthermore, it is known that B15C5 efficiently hosts sodium cations with high binding affinity.…”