Colloidal synthesis and characterizations of metal, metal- oxide, and semiconductor nanoparticles by inductive heating method

Abstract

The goal of this thesis is to develop a faster, safer, and industrial-level scale-up methodology for the synthesis of diverse nanomaterials applying the inductive heating methodology. This thesis discusses the size control magnetic inductive heating synthesis of iron, iron- oxide, manganese, manganese/iron alloys, and germanium nanoparticles (NPs) in different chapters. Background in the magnetic heating methodology and how it can be used for nanomaterial synthesis is discussed in Chapter 2. Chapter 3 describes the synthesis and characterization of colloidal insulating iron-oxide NPs. Fe₂O₃ and Fe₃O₄ NPs were prepared by inductive heating. Their morphological and magnetic properties were studied in detail. The effect of different solvents and heating times on the size of NPs was explored. Furthermore, this chapter discusses how the inductive heating methodology can be utilized for the use of solid precursors to prepare monodispersed, phase pure γ- Fe₂O₃ NPs. Chapter 4 is aimed to describe the synthesis of air-stable metallic iron NPs with their size tuning. TEM, HRTEM, PXRD, and elemental analysis were carried out to confirm the formation of iron NPs and their particle size distributions. SQUID was used to investigate the magnetic properties of thus synthesized NPs. Chapter 5 focuses on achieving greater control over the size distribution in the solution synthesis of semiconducting germanium NPs. The effect of concentration of precursor and heating time was explored. This chapter will also discuss the possible defects present in as-synthesized NPs. Various spectroscopic characterizations such as transient absorption and UV-Vis-NIR were performed to identify the quality of crystals. Finally, Chapter 6 describes the use of the inductive heating methodology for the synthesis of manganese oxide and iron-manganese oxide alloy nanoparticles, a potential material for fossil-free ammonia synthesis by step catalysis. The one-pot inductive heating-assisted method promises a scalable and low-cost production of highly crystalline NPs by overcoming the traditional disadvantages of long reaction times, high temperature and pressure, complicated precursor preparation, and exhaustive post-synthetic purification steps.