Synthesis and Potential Applications of Advanced Materials: TMDs and Polyazomethine Composites

Abstract

Two-dimensional layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing materials. The versatile and tunable properties of these materials make them attractive for compendium of applications. Emerging transition metal dichalcogenides offer unique and hitherto unavailable opportunities to tailor the mechanical, thermal, electronic and optical properties of polyazomethine based composites. Phase conversion of the transition metal dichalcogenides from 2H phase to 2H'/1T was carried out by organolithium treatment of MoS2 and MoSe2 polycrystalline films on the chips. The conversion was done successfully on the particular area yielding a lateral heterostructure concerning the pristine 2H phase and the 2H'/1T co-phase regions. Lateral heterostructure was verified by Raman spectroscopic, X-ray photoelectron spectroscopic studies and X-ray diffraction analysis. Scanning electron (SEM) and atomic force (AFM) microscopies revealed the changes in the surface morphology and work function of the heterostructure in comparison to the pristine films. Phase stability studies of the heterostructure were also studied by Raman spectroscopic studies. Gas sensing and electrical properties were also performed on these chips. Functionalization route was demonstrated that results in ethylene glycol bonded to the MoSe2 surface via covalent C–Se bond. It was based on lithium intercalation, quenching of the negative charges residing on the MoSe2 by electrophiles such as bromo diazonium salts and subsequently proceeding with ethylene glycol via cross coupling reaction. FTIR and (1H and 13C) NMR spectroscopic analyses techniques were used for structure elucidation. Strong evidence for the existence of heterostructure 2H'/1T of MoSe2 after the effective grafting of C– O linkage on the MoSe2 surface was confirmed by wide angle X-ray diffraction (XRD) and Xray photoelectron spectroscopic studies (XPS). Thermal stability of the synthesized product was ensured by the thermogravimetric analysis (TGA). Surface morphology was also probed by scanning electron microscopic studies (SEM). Further strategy of modifying TMDs with amine-terminated polyazomethines (PAs) was successfully offers a scalable platform suitable for tuning the properties of flexible PAs TMDs composite. TMDs (MoS2, MoSe2, WS2 and WSe2) were properly embedded in the polymer matrix. Bifunctional aldehyde monomers containing sulphone linkage were synthesized and subsequently confirmed by FT-IR and (1H and 13C) NMR spectroscopic studies and then treated with two different diamines to prepare six polyazomethines via polycondensation method in acidic media. Synthesized polyazomethines were confirmed by FT-IR and (1H and 13C) NMR spectroscopic analysis. Furthermore, in another attempt, the ethoxy pendant group was also attached to the linear polyazomethines. Synthesized poly- azomethines (PAs) were further doped with TMDs material and characterized by FTIR, Raman and XPS spectroscopic studies. Scanning electron and transmission electron microscopic studies revealed changes in the surface morphology. Energy dispersive X-ray spectroscopy (EDX) was also done using the TEM setup. UV-Visible and fluorescence spectroscopic technique were also performed to study the photophysical behavior. Electrocatalytic activity was also performed on these composite materials. In addition, synthesized polyazomethines were covalently grafted onto acid functionalized MCNTs. The synthesized nanocomposite materials were consequently characterized by spectroscopic studies (FT-IR, Raman spectroscopic studies). X-ray diffraction (XRD) and Xray photoelectron (XPS) spectroscopic studies were also performed. Scanning electron and transmission electron microscopic studies revealed modifications in the surface morphology. A current voltage measurements and electrocatalytic activity were also performed on these PAs-MCNTs composites. This perspective concerns the synthetic strategies that have been used to incorporate PAs into TMDs and grafting onto MCNT’s surface can improve their performance in technological applications.