Surface mineralization and characterization of tobacco mosaic virus biotemplated nanoparticles
Abstract
The genetically engineered tobacco mosaic virus (TMV) has been utilized as a biotemplate in the formation of nanoparticles with the intent of furthering the understanding of the biotemplated nanoparticles formed in the absence of an external reducing agent. Specifically, the work aims to provide better knowledge of the final particle characteristics and how these properties could be altered to better fit the need of functional devices. Three achievements have been accomplished including a method for controlling final particle size, characterizing the resistivity of palladium coated TMV, and the application of TMV as an additive in nanometric calcium carbonate synthesis. Until the last 5 years, formation of metal nanoparticles on the surface of TMV has always occurred with the addition of an external reducing agent. The surface functionalities of genetically engineered TMV allow for the reduction of palladium in the absence of an external reducing agent. This process has been furthered to understand how palladium concentration affects the final coating uniformity and thickness. By confirming an ideal ratio of palladium and TMV concentrations, a uniform coat of palladium is formed around the viral nanorod. Altering the number of palladium coating cycles at these concentrations allows for a controllable average diameter of the final nanorods. The average particle diameter was determined by small angle x-ray scattering (SAXS) analysis by comparing the experimental results to the model of scattering by an infinitely long cylinder. The SAXS results were confirmed through transmission electron microscopy images of individual Pd-TMV nanorods. Secondly, methodologies to determine the electrical resistivity of the genetically engineered TMV biotemplated palladium nanoparticles were created to provide valuable previously missing information. Two fairly common nanoelectronic characterization techniques were combined to create the novel approach to obtain the desired measurements. A gold nanogap electrode was designed with focused ion beam (FIB) milling, and electron beam or FIB assisted platinum deposition provided contacts between the electrodes and the nanoparticles. Promising preliminary results obtained with the electron beam platinum deposition produced a nanowire resistance of ~75 kΩ. By varying the nanogap width and utilizing the FIB assisted platinum deposition, a resistivity of 4.27 × 10-5 ± 1.22 × 10-5 Ω•m was determined for the Pd-TMV. This resistivity value indicates a potential future for Pd-TMV particles in nanoelectronic applications. Finally, the genetically engineered TMV into the slurry of a calcium carbonate synthesis in order to test its potential use as a biotemplate in altering the structure of nanometric calcium carbonate. A second technique in the absence of TMV was developed by using dioctyl sodium sulfosuccinate (AOT) as a surfactant to limit the size of the precipitated calcium carbonate. In comparing the two synthesis techniques, the AOT was capable of limiting the particle size of the calcium carbonate at much higher reaction concentrations. However, at lower concentrations the TMV was shown to occasionally alter the shape of the precipitated CaCO3 as some of the particles were cylindrical in shape instead of the commonly formed spherical particles. These investigations further the knowledge of the capabilities of the tobacco mosaic virus as a biotemplate in nanoparticle synthesis. Combined these results show the versatility of TMV, and the knowledge of the characteristics of the synthesized particles could lead to better application of these particles in functional nanodevices.
Degree
Ph.D.
Advisors
Harris, Purdue University.
Subject Area
Chemical engineering|Nanotechnology
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