Investigation of the compositional and structural properties of liquid metal entities for catalysis

Liquid metals are evolving in diverse research fields due to their peculiar chemical and physical properties. The emerging concept of combining two or more metallic elements can potentially reduce the system's melting point and enable them to be engineered and tuned to improve the performance of specific applications in catalysis, sensing, electronics, microfluidics, and biomedicine, which to date remain unknown. Despite the promising developments regarding liquid metals, the awareness and knowledge regarding solidification, scalable synthesis of catalytic materials, crystal formation, and phase separation have not been deeply explored. This thesis focuses on the synthesis techniques, applications, and fundamentals of liquid metals and investigating their surface and core alloys. In Chapter 3 of the thesis, particles of Field's metal (an alloy of bismuth 32.5 wt%, tin 16.5 wt% and indium 51 wt%) are produced using an ultrasonication approach at a low processing temperature. It is demonstrated that the sonication process produces heterostructure core-shell particles with specific defects that emerge after solidification. Interestingly, modifications towards the Field’s metal system through silver (Ag) incorporation selectively improve the catalytic activity towards specific dyes, which can be readily extended for designing catalysts. In Chapter 4, gas-sensitive semiconducting compounds are developed by using the same concept in synthesizing micro/nano particles of liquid metals via ultrasonication procedures. Metallic elements of indium (In), tin (Sn), and zinc (Zn) are incorporated into liquid gallium (Ga), which are later sonicated in two different solvents: dimethyl sulfoxide (DMSO) and water for producing particles with different sizes, morphologies, and crystal structures. Responses of synthesized samples towards hydrogen (H2) and nitrogen dioxide (NO2) gas species are favourable towards particulate products prepared in DMSO in contrast to preparation in water. This is highly beneficial for functional engineering materials for sensing applications. For Chapter 5, the author further explores the unique behaviour of Ga-based alloys. Solute metals including Zn, Sn, Ag, bismuth (Bi), nickel (Ni), manganese (Mn), copper16 (Cu), platinum (Pt), and a combination of Mn and aluminium (Mn/Al) are dissolved into liquid Ga at an elevated temperature. Growth of crystals is observed in the liquid metal solvents, which are later extracted through a combination of electrocapillary modulation and vacuum filtration techniques. It is demonstrated that the structural change of the crystals formed is significantly influenced by the growth conditions (growth time, temperature, and pressure). This work further complemented the mechanistic understanding of the dynamic nature of the metallic crystal growth phenomenon, specifically in liquid metal solvents. The findings presented in this thesis are expected to give insightful impact into the fields related to the development of sensing elements, microfluidic systems, flexible electronics, bio-applications, and possibly catalytic materials