Au nanoparticle assembly on CNTS using flash induced solid-state dewetting
Carbon Nanotubes (CNTs) are used extensively in various applications where substrate are required to be possessing higher surface area, porosity and electrical and thermal conductivity. Such properties can be enhanced to target a particular gas and biochemical for efficient detection when CNT matrix is functionalized with Nanoparticles (NPs). Conventional functionalization involves harsh oxidation repeated washing, filtration and sonication, which induce defects. The defects lead to hindered mobility of carriers, unwanted doping and also fragmentation of the CNTs in some cases. In this document we demonstrate functionalization of CNT with Au nanoparticles on a macro scale under dry and ambient condition using Xenon flash induced solid-state dewetting. A sputtered thin film was transformed into nanoparticles which were confirmed to be in a state of thermodynamic equilibrium. We worked on 3nm, 6nm, 9nm, 15nm, 30nm initial thickness of thin films. Xenon flash parameters of energy, number of pulse, Duration of pulse, duration of gap between consecutive pulses were optimized to achieve complete dewetting of Au thin films. 3nm deposition was in the form of irregular nano-islands which were transformed into stable nanoparticles with a single shot of 10J/cm2 of 2ms duration. 6nm and 9nm deposition was in form of continues film which was also dewetted into stable nanoparticles with a single pulse but with an increased energy density of 20J/cm2 and 35 J/cm2 respectively. In case of 15nm and 30nm deposition the thin film couldn't be dewetted with a maximum energy density of 50 J/cm2, it was observed that 3 and 4 pulses of 2ms pulse duration and 2ms gap duration with an energy density of 50J/cm 2 were required to completely dewet the thicker films. However irregularity was induced in the sizes of the NPs due to Ostwald ripening phenomenon which causes smaller particle within a critical diffusion length to combine and form a larger particle during or after dewetting process. For comparison purpose the Au thin films were also dewetted by a conventional process involving annealing of samples until the thin film was fully transformed into NPs and the size of NPs seized to grow. Scanning electron microscope (SEM) was used to characterize the samples. Thermodynamic stability of the particles was confirmed with statistical analyses of size distribution after every additional pulse.
Ryu, Purdue University.
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