Novel nanostructures in transition metal chalcogenide systems

QC Physics;QD Chemistry;Q Science (General)

Denholme, Saleem J. ; Gregory, D.H.

University:University of Glasgow

Department:School of Chemistry

关键词: Nanostructure, Chalcogenide, transition metals;   

Others  :  http://theses.gla.ac.uk/3077/1/2011Denholmephd.pdf

来源: University of Glasgow

【 摘 要 】

This thesis discusses the synthesis of transition metal chalcogenide nanostructures(where the chalcogen is either sulfur, selenium or tellurium) through the use ofstandard chemical vapour transport (CVT) and chemical vapour deposition (CVD)techniques. The resultant structures are characterised with a variety of methods andcomparisons of their properties are made with their bulk counterparts. A discussion intohow some of these structures form during the reaction is also given.Highly symmetrical, isotropic, nickel disulfide (NiS2) nanocubes have been synthesisedvia a Physical Vapour Transport (PVT) method in which sulfur vapour generated in situ isreacted with nickel-coated silica substrates. Systematic studies demonstrate the effectof the reactant ratio, substrate, metal layer thickness and reaction temperature on thesynthesis and growth process. The evolution of structure and composition has beenfollowed by diffraction and scanning electron microscopy (SEM). The size of the NiS2cubes can be varied from below 200 nm to 1 -2 1m across. Magnetic properties of thedisulfide nanomaterials have been determined using superconducting quantuminterference device (SQUID) magnetometry. Initial experiments also demonstrate thatrelated CVT techniques can be exploited to produce alternative compositions in the Ni-Ssystem with varying morphologies that can be controlled via chemical and physicalreaction parameters.Surface Assisted Chemical Vapour Transport (SACVT) methods have been employed togrow flower-like nanostructures of titanium disulfide (TiS2) and titanium trisulfide (TiS3)on titanium coated silica substrates. Systematic studies demonstrate the role of thereactant ratio and reaction temperature on the synthesis and growth process. Theevolution of structure and composition has been followed by powder X-ray diffraction(PXD) and electron microscopy techniques such as and transmission electron microscopy(TEM). Magnetic properties of the disulfide nanomaterials have been determined usingSQUID and Raman spectroscopy has been used to confirm the identity of the sulfides.Investigations into nanostructured materials of the group IV transition metals zirconiumand hafnium resulted in the successful synthesis of nanostructures of zirconiumtrisulfide/selenide (ZrS3/Se3) and hafnium trisulfide/selenide (HfS3/Se3). The unusualeffects on structure that can occur when reactant time and synthesis temperature arevaried and when a balance between these two factors is successfully found,nanostructures other than tubes and wires can be formed. Each of these systems werecharacterised with a variety of techniques including, TEM, PXD and SQUID.