Asian Research Thesis Index

Abstract

The aim of the project is to design and develop a cost-effective and mass productive microplasma facility for the synthesis of Nanodiamonds (NDs) and their composites for the water purification. In order to produce microplasma, electrode assembly consisting of an array of hollow capillary cathode and a stainless steel mesh anode were fitted in a chamber which was attached with a gas flow system. NDs were formed by dissociation of gas mixture using this microplasma facility. Ethanol is chosen as a carbon precursor and argon as a carrier gas. A mixture of ethanol and argon has been dissociated in microplasma to form NDs. However, the addition of hydrogen is to enhance the quenching, etching, and stabilization of NDs. Initially, the focus was to find an effective root for the introduction of hydrogen in microplasma. hydrogen is introduced either directly or indirectly into the microplasma. Availability of high amount of atomic hydrogen and presence of argon makes the indirect dilution more efficient as compared to direct dilution. The next step was to explore the suitable flow rate of indirectly inserted hydrogen as flow rate is an important parameter to control the structure and properties of NDs. Therefore, the experiments were carried out at hydrogen flow rates of 3 and 5 L/min out of which 3 L/min was found to be better as flow rate for as the quality of the NDs are concerned. It was also attempted to produce NDs without the introduction of hydrogen. For this purpose, the experiments were carried out without hydrogen for different argon flow rates ranging from 3 to 9 L/min. Amongst all, 6 L/min appears to be the best flow rate for the growth of smallest size and near stress free NDs. It was established that NDs can be fabricated even without the hydrogen. The synthesized NDs (with and without hydrogen) were characterized by various diagnostic techniques. Raman spectroscopy and X-rays Diffractometer were utilized for structural analysis. Atomic force microscopy was used for surface morphology of NDs. The Optical characterization of NDs has been determined through UV-Visible absorption and Photoluminescence spectroscopy. The details of the functional groups present at the surface of the NDs has been investigated using Fourier Transform Infrared Spectrophotometer. The NDs produced at the optimized carrier gas (argon) flow rate of 6 L/min. are of best quality which were then utilized as a nanofillers to fabricate polymeric and metallic nanocomposites. Polyvinyl Alcohol (PVA) and silver (Ag) are used as polymer and metal matrix, respectively. The purpose of fabrication PVA-NDs and Ag-NDs composites was to utilize them for antibacterial applications PVA-NDs are prepared by solution casting method. XRD confirms that the intensity of PVA diffraction peak decreases with increasing content of NDs. The absence of NDs peak confirmed the homogeneous mixture PVA and NDs. Antibacterial activity has been evaluated against E-coli and S-aureus. PVA-NDs exhibits higher antibacterial activity than PVA. PVA-NDs composite could be a promising candidate for safe antibacterial packaging Silver nanoparticles (Ag-NPs) and Ag- NDs composites have been synthesized by microplasma techniques. Raman spectra confirm the formation of Ag-NPs and it also indicate the presence of both Ag and NDs in Ag-NDs composite. NDs act as seed and increases the Ag+ ion reduction. Thus, a core (NDs) shell (Ag) composite is obtained. Antibacterial activity of Ag-NDs composites have been tested against E-coli and S-aureus. An improvement in antimicrobial properties of Ag- NDs composite as compared to that of Ag has been observed. The enhanced antibacterial activity of the Ag-NDs composite makes it a potential candidate for water purification. Therefore, the water filtrates (fiberglass, cation resin, zeolite, anion resin and sand) were coated with Ag and Ag- NDs composites. XRD and EDX analyses confirm the coating of Ag and Ag-NDs on the filtrates. Tap water has been taken from Sabzazar, Lahore, Pakistan. Physicochemical properties of Tap water before and after incorporation of Ag and Ag-NDs coated filtrate were evaluated by standard methods. NDs reduced the pore size of filtrates. NDs improved the binding of silver to the various filtrates. The decreasing trend of total dissolved, total suspended solids, hardness and turbidity was more pronounced for Ag-NDs composite filtrates as compared to Ag coated filtrates. Antibacterial activity has been performed with black water taken from main sewerage line. Antimicrobial properties of Ag and Ag-NDs coated filtrated black water were investigated using total fecal coliform bacteria. Ag-NDs coating has positive effect antibacterial properties of water.

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