Nanomaterials for Magnetism and Catalysis

Abstract

Nanomaterials possess unique physical and chemical properties allowing for advancement and innovation in diverse scientific and technological fields. The remarkable magnetic and catalytic properties of these nanomaterials have prompted research into the design and development of tailored nanostructures. Considerable research efforts have been dedicated to the improve the fundamental understanding of the nanomaterial properties. The synthesis of nanoparticles of metals like Mn, Fe, Co, Zn, etc. in zero oxidation state is quite challenging due to their oxidative instability. Solvated metal atom dispersion method stands out to be an excellent synthetic methodology to realize nanoparticles of reactive metals.1 Additionally, efficient catalysts with enhanced reactivity and selectivity are realized in bimetallic nanostructures combining a noble metal with transition metals like Zn.2 Co-digestive ripening approach offers a solution-based route, allowing for the controlled synthesis of desired bimetallic nanostructures through precise control of synthesis parameters.3 This work emphasizes the crucial role of size, composition, and surface interactions in customizing the magnetic and catalytic properties of nanomaterials.

Mn(0) colloids have been prepared by the SMAD method using hexadecylamine (HDA), toluene and THF as capping agents. Monodispersed nanoparticles of Mn-HDA were obtained through digestive ripening. The magnetic properties of the resulting Mn nanoparticles are investigated, revealing intriguing exchange bias behavior arising from surface oxidation and uncompensated antiferromagnetic spin interactions.4

Furthermore, we employed the co-digestive ripening strategy in conjunction with the SMAD method to synthesize Pd@ZnO core-shell nanocomposites and Pd-Zn alloy nanoparticles. The catalytic performance of the Pd@ZnO nanocatalyst is evaluated for the selective hydrogenation of terminal alkynes, showcasing a sequential hydrogenation process yielding internal alkenes and further hydrogenation to the corresponding alkanes.5 HDA-capped Pd-Zn alloy nanoparticles having a random alloy structure exhibit excellent catalytic activity in the semi-hydrogenation of phenylacetylene, showcasing high selectivity towards styrene. Additionally, acetylene semi-hydrogenation using Pd-Zn alloy has been investigated, demonstrating high selectivity towards ethylene at room temperature.6 The detailed investigation for high selectivity towards ethylene has been performed and the results is presented in the thesis.