Microstructural and Chemical Characterisation of Metal Particles Nanostructures

Abstract

In order to achieve a full characterisation of metal particles nanostructures at the microstructural level, we show in this overview the use of different techniques: i) High resolution transmission electron microscopy (TEM) or energy filtered TEM (EFTEM) associated to energy dispersive X-Ray analysis (EDX) and electron energy loss spectroscopy (EELS). ii) A surface analysis technique like X-Ray photoelectron spectrocopy (XPS). iii) A technique sensitive to the local structure and chemical state like X-Ray absorption spectroscopy (XAS). Two systems will be described to illustrate this study:
i) Nickel particles dispersed in an amorphous carbon matrix have been synthesized by a sonication method, and further heated at 773 K under Ar atmosphere. The as-prepared sample shows amorphous spherical particles (TEM) formed by Ni²⁺ highly dispersed in carbon (XPS, XAS). The heated sample shows spherical grains formed by nanocrystalline Ni particles embedded in an amorphous carbon matrix (HRTEM). Heterogeneities at micro- and nanoscopic scale have been determined by TEM/EELS and EFTEM. Quantification of the oxidation level for the heated sample was also determined by XAS. ii) Gold nanoparticles modified with neoglycoconjugates molecules have been prepared by a wet chemical method. Aggregates, isolated nanoparticles or two-dimensional self-organised nanostructures have been obtained by controlling the interaction forces between biological significant oligosaccharides. The EFTEM analysis has been used to demonstrate the role of divalent cations in the formation of the nanostructures.