Nanocomposites Based on Dendrimers and Layered Molybdenum Disulfide

Abstract

Nanocomposites consisting of molybdenum disulfide (MoS2) and an organometallic dendrimer were synthesized by taking advantage of the exfoliating/restacking properties of lithiated molybdenum disulfide (LiMoS2). Based on the molecular weight of the dendrimer, nine different mole ratios of MoS2 to dendrimer were utilized in order to investigate the upper and lower limit of the dendrimer loading into the restacked MoS2. The developed nanocomposites were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and variable-temperature electrical conductivity measurements. Our studies revealed that the ideal condition for preparing reproducible monophasic systems is at low dendrimer concentration, no greater than 1:0.125 mole ratio of MoS2 to dendrimer, and no lower than 1:0.002 mole ratio of MoS2 to dendrimer. Biphasic systems can be produced at mole ratio of MoS2 to dendrimer higher than 1:0.125. Additionally, the average crystallite size decreased as the mole ratio of the MoS2 to dendrimer was increased. Specifically, a change from 1:0.002 to 1:0.5 resulted in a noticeable decrease from 365 to 155 A. The electrical conductivity of the nanocomposites drops as the amount of dendrimer increases. Variable-temperature conductivity data are consistent with a variable-range hopping model.