Mechanistic study of the hydrothermal reduction of palladium on the Tobacco mosaic virus

Abstract

West Lafayette, Indiana ii I dedicate this thesis to my goddaughter, Erinayo Obadina.iii ACKNOWLEDGEMENTS

Molecular Docking and Aberration-Corrected STEM of Palladium Nanoparticles on Viral Templates

“…Similar to the observations here, His, Asn, and Arg residues of synthetic peptides effectively served as nucleation and stabilizing agents to obtain Pd nanoparticles [36]. Several reports have shown the need for site-directed mutations to insert Cys residues in TMV, providing active sites for the adsorption and reduction of Pd(II) ions and other metal precursors [9,15]. However, wild-type TMV has also proved to be able to stabilize these precursor ions, suggesting that other amino acid residues are involved [9].…”

“…VP6 self-assembles into tubes with a diameter of 75 nm in the pH range of 5.5-7.0, and may support divalent cations up to 200 mM, keeping its macrostructural arrangement [37]. Several reports have shown the need for site-directed mutations to insert Cys residues in TMV, providing active sites for the adsorption and reduction of Pd(II) ions and other metal precursors [9,15]. However, wild-type TMV has also proved to be able to stabilize these precursor ions, suggesting that other amino acid residues are involved [9].…”

“…Viral templates (complete viruses or virus-like particles) stand out as bioscaffolds due to their advantageous inner nanometer-range properties: self-assembly capacity, monodispersity, discrete size and shape, stability, symmetry, and biocompatibility [8]. Palladium nanoparticles were synthesized with Tobacco mosaic virus (TMV) as the scaffold in the aqueous phase [9], as part of hydrogel formulations or through hydrothermal reduction [10][11][12][13][14][15], producing complete coverage of the viral particles with a Pd layer or the formation of discrete particles of 1-2 nm, depending on reaction conditions. Additionally, genetically engineered M13 bacteriophages were used as biotemplates for Pd particles obtaining hybrid nanorods and nanowires with potential applications in nanobatteries [16,17].…”

Decoupling and elucidation of surface-driven processes during inorganic mineralization on virus templates

“…In a system with much higher Pd concentration, salt build up will increase the ionic strength of the solution and could initiate this Cldriven inhibition even before all of the Pd has reduced. This observation was made in the entryway XAS study performed by Adigun et al 44 in which a much fast reduction was followed by a slower reduction after an initial layer of Pd had grown on the biotemplate surface. This observation about the effect of salt concentration during the mineralization process is also particularly important in view of accessing the future possibility of halide controlled nanocrystal growth in these systems.…”

“…Time-resolved XANES spectra were used to obtain the ratio of oxidation states of palladium i.e. Pd (2+) : Pd (0) at different times during synthesis as was previously described by Adigun et al 44 Results from these are shown in Figure 2 Results show that the kinetic constant decreased to zero when a new coating cycle was performed without the removal of ionic products (Figure 3(a)). The opposite observation was made for the mineralization of washed particles i.e.…”