Vortex fluidics manipulation of nano carbon

Author: Kasturi Vimalanathan

Vimalanathan, Kasturi, 2016 Vortex fluidics manipulation of nano carbon, Flinders University, School of Chemical and Physical Sciences

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Carbon nanomaterials of various dimensionalities have gained a unique place in nanotechnology owing to their explicit physical and chemical properties. These include excellent optical and thermal properties, electrical conductivity and high mechanical strength. Such materials have a myriad of applications including for energy storage, sensors, drug delivery, field emission devices, electronic devices, as high strength materials and biomedical engineering. Carbon based nanomaterials have been widely used for decades in device and sensing technology and other related fields, but only recently have biological applications emerged. However, there are concerns about the toxicity of these nanomaterials, and exquisitely controlling their morphology, shapes and size is pivotal to harness their full potential. Following advances in fabrication and characterization techniques, graphene has emerged as a building block for other carbon nanomaterials other than nanodiamond, which include carbon nanotubes of single to multiple shells, fullerene C60 and C70 and carbon nanoonions.

Conventional processing methods have dominated the fabrication of carbon nanomaterials. This includes traditional “top down” and “bottom up” approaches which can involve long and tedious processing, the use of toxic and harsh chemicals, and the use of surface active molecules and chemical stabilizers. Although the methods can be high yielding and offer great opportunities in the market place, there are major concerns primarily around the high cost of fabrication, the generation of waste streams, high energy usage and the requirement for extensive down stream processing.

The key focus of this thesis is creating a paradigm shift in nanoscience, employing the use of process intensification as an alternative strategy towards the fabrication and manipulation of novel forms of carbon material at the nanoscale level. The research potentially hails a new frontier to the fabrication of different new carbon nanoforms which incorporate green chemistry metrics and is likely to create opportunities towards industrial applications. While addressing the issue of scalability beyond generating research quantities of carbon nanoforms, the ability to unequivocally manipulate high tensile carbon nanomaterials in particular poses a number of challenges. This includes the use of toxic organic chemicals, long and tedious processing times and the use of surfactant, and indeed overcoming these in general is potentially a Holy Grail in material science.

With the limitations of traditional batch processing, the synthesis of nanocarbon potentially benefits from innovation in using novel energy efficient processing platform with controllable operating conditions. Recently the vortex fluidic device (VFD), as a microfluidic platform with dynamic thin films, has been developed as a versatile continuous flow processor. It has a number of novel and facile capabilities including controlling self assembly processes, and the fabrication and growth of carbon nanomaterials with distinct control over the morphology, shape and size of the nanostructures.

This thesis focuses on advancing the applications of the VFD in nanocarbon technology, specifically in fabricating carbon nanomaterials based on carbon nanotubes, fullerenes C60 and graphene. The controllable mechanoenergy within dynamic thin films in the VFD has been used to fabricate different forms of nanocarbon, with potential for a wide range of applications, from device technology to drug delivery, with a view of transferring the technology to the market place.

The thesis introduces the different forms of carbon nanomaterials and the extent of research developments in the area. The method of process intensification utilized to manipulate different carbon nanomaterials, namely vortex fluidic device (VFD) will be described. The research established that the VFD is effective for slicing carbon nanotubes in a controlled way while irradiated with a pulsed laser operating at 1064 nm wavelength, as a process incorporating green chemistry metrics, including scalability. In addition, the VFD was effective in fabricating toroidal arrays of single walled carbon nanotubes, the formation of self assembled arrays of fullerene C60 in the form of nanotubules which are superior sensing material for detecting small molecules, and the direct exfoliation of graphene into graphene scrolls. The extent of advances made in this research, in filling gaps in the scientific arena will be discussed.

Keywords: nanocarbon, continuous flow, self assembly, fabrication

Subject: Chemistry thesis

Thesis type: Doctor of Philosophy
Completed: 2016
School: School of Chemical and Physical Sciences
Supervisor: Professor Colin Raston