Synthesis and development of multifunctional carbonaceous nanostructures for magnetic, optical and catalytic applications

Abstract

Owing to the ease of functionalization, low synthesis-cost and polymorphism, carbonaceous nanostructures such as carbon globules, nanotubes (CNTs) and graphene sheets emerged technologically as one of the most important class of multifunctional materials. In this thesis a wide variety of carbon based nanostructures were synthesized by the simple pyrolysis method, characterized and their applicabilities are demonstrated. Among the synthesized materials, metallic particles embedded amorphous carbon globules, CNTs of different morphologies such as spiralling tendrils, cup and box type bamboos, hollow and filled onions etc. are the exotic ones. We also demonstrated a way to synthesize nanoscale particles of various metallic alloys, which can be useful for any structural design in powder metallurgy. These carbon coated metallic particles, which protect themselves against any environmental corrosion, are otherwise, difficult to synthesize by any other conventional method. The structure, morphology, size distribution of the dispersed metallic particles in carbon nanostructures were investigated and correlated with their optical, magnetic, electronic and chemical properties. We have demonstrated multifunctionality of our synthesized carbonaceous materials. Our investigation highlights the non-linear absorption of laser beams in metallic nanoparticles embedded carbon materials, making them potential candidates for optical limiters. Furthermore, the dispersion of nano-sized metallic particles inside amorphous carbon matrix proves to be microwave absorption enhancers, enabling their use as electromagnetic interference (EMI) shields. In addition, the catalytic activity of most of our samples is excellent, but can be further improved by controlling the amount of defects via nitrogen doping. The catalytic performance for reduction of 4-nitrophenol by some selective samples exceeds many of the catalysts reported earlier. The performance of some of our samples in electronic devices such as in infrared photodetectors is exceptional. The use of the samples for magnetorheological applications for energy storage and many other applications cannot be undermined. Hence, our work demonstrates that our synthesized samples are versatile and truly multifunctional