Synthesis, Characterization and Irradiation of Fullerene Based Metal Nanocomposites

Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeirosThe present research work entitled “Synthesis, Characterization and Irradiation of Fullerene Based Metal Nanocomposites” envisages the study on the feasibility of using fullerenes, one of the most emerging functional materials as a matrix for the reinforcement of metal nanoparticles. Fullerene matrix nanoparticles embedded composites are found to exhibit surface plasmon resonance (SPR) by virtue of which a significant enhancement of absorbance of the material become possible; the bifunctional property of matrix and metal nanoparticles in a single material makes it highly beneficial and applicable for different optical devices, thereby making it poised for emergence as a lucrative energy material. Understanding that the performance of optical absorbance of nanocomposites is highly influenced by the host microstructure, it has appeared important to monitor the structural conditions of fullerene as matrix material when subjected to such treatments as considered useful for enhancement of SPR due to noble metal particles in nanocomposites. It is further known that ion beam irradiation is most effective in alteration of SPR behavior of nanoparticles of noble metals like Au and Ag. So the present study in chapter 4.1 has contemplated to explore the effect of heavy ion beam irradiation (90 MeV Ni ion) on fullerene C60 thin film. As expected the damage of fullerenes has been fluence dependent and that ion tracks of determinable diameter could be formed by such irradiation. In view of the fact that elaborate studies on fullerene C70 is till due to be reported in literature, the present research work in chapter 4.2 has investigated and reported the effect of irradiation by different ions viz. 90 MeV Si, 55 MeV Si, 90 MeV Ni and 125 MeV Au on fullerene C70 thin films. Based on the results of the above ion beams of different electronic energy loss (Se), the damage cross section has been calculated for each ion beam, compiled and a relationship between damage cross section and electronic energy loss is developed which is supposed to be beneficial in estimating the value of damage cross section for any unknown situation of electronic energy loss within the range of present study. Although the potential of nanoparticles of gold and silver as reinforcement in fullerene C60 and C70 has been amply researched, the potential of copper is yet to receive due research attention in spite of its advantage of interesting mechanical properties, high electrical conductivity, favorable catalytic properties, appropriate melting point, high stability and high natural abundance in nature. Hence, the present thesis work has reported (chapter 5.1) the results of investigation on the incorporation of copper nanoparticles in fullerene C60 matrix subjected to irradiation by low energy ion beams (100 keV Ag ion, 350 keV Ar ion). As a corollary of low energy 100 keVAg ion irradiation study the widening of absorption range could be observed due to hybridization of copper nanoparticles induced SPR and that due to Ag ions getting implanted within in the silicon substrate. The low cost of Cu over Ag and Au makes it more attractive for applications in various fields of optics, electronics, solar energy conservation, sensors, lubricants and sliding electrical contacts. Effect of high energy (120 MeV Ag) ion irradiation on Cu (18 at. %)-C60 has implicitly demonstrated (chapter 5.2 ) the enhancement of SPR band intensity due to copper nanoparticles; the concurrent growth of copper nanoparticles at increasing fluences has caused a shift in the position of SPR band. The chapter 6 of present study has addressed the research questions related to Cu-C70 nanocomposite thin films under ion irradiation of various energies. The low energy ion beam irradiation (350 keV Ar ion) of Cu (10 at.%)-C70 nanocomposite thin films have been able to exhibit SPR band due to copper only after irradiation at fluence of 1×1015 ions/cm2. The SPR band increases its intensity with increasing fluence and got shifted towards lower wavelength side. This is in contrast with the pristine which has not exhibited any SPR due to copper presumably due to its low concentration. The similar behavior was also exhibited by this composite subjected to high energy ion beam irradiation (120 MeV Ag ion) with the exception that SPR could be obtained only at a higher fluence like 3×1013 ions/cm2. Since any fluence higher than 3×1013 ions/cm2 has not been employed in the present study it is not possible to be conclusive if it would also exhibit a blue shift with still increasing fluence, which, it seems would occur most likely. However, the studies in chapter 6 clearly authenticates that both the concentration of embedded nanoparticles and the change in optical properties of irradiated fullerenes are responsible for determining the intensity and the position of SPR due to copper in fullerene C70 matrix