Towards an understanding of abiotic-biotic interactions for the development of novel biocomposite materials

• Main Author: Oliver, Daniel J
• Format: Dissertation
• Language: English
• Published: Nottingham Trent University 2020

Developing a fundamental understanding of the interplay between primary peptide sequence and interaction with the target substrate with respect to the synthesised product is an active research area. In this study, a one-pot synthetic route to ZnO-Au heterostructures was devised using peptide mediation as the reaction control. To achieve this, binding interactions of known gold binders including A3 (AYSSGAPPMPPF), AuBP1 (WAGAKRLVLRRE) and AuBP2 (WALRRSIRRQSY) to gold substrates were investigated to explore the interplay between the primary sequence and overall binding efficacy of a given peptide. Kinetic and thermodynamic data was collected with the kinetics being explored using a Langmuir-Kisliuk kinetic model developed during the programme of research which is capable of fitting kinetic data from 0.1-800μM with a high quality of fit (adj-R2 > 0.9). This study found that positively charged amino acid diads in the peptide sequence had a higher affinity for the gold substrate than the sulphur containing residues (Cys, Met). Further, multiple histidine residues or histidine diads in a sequence had a high affinity for the Au(111) surface and a far lower affinity for the Au(110) and Au(100) surfaces. A hybrid binding sequence to facilitate a one-pot synthesis of ZnO-Au heterostructures was engineered from a known gold binding peptide A3 (AYSSGAPPMPPF) and a known ZnO binding peptide G-12 (GLHVMHKVAPPR) which has been extensively studied within the Perry group. The engineered ZA2 peptide (GLHVMHKAYSSGAPPMPPF) was used to synthesise ZnO in both the presence and absence of gold resulting in pseudospherical ZnO-Au microstructures and micron sized ZnO nanoflowers respectively. To expand understanding of the impact of peptide mediation and gold inclusions on ZnO behaviour both Mie theory modelling and a novel spectroscopic method termed 2D Fluorescence Mapping (2DFM) were used to study these systems. By careful deconvolution of the spectroscopic features to extract defect state contributions 2DFM was able to identify the complex emissive state topology of semiconductors including anthracene, CdS, CdSe, TiO2, ZnS, ZnSe & ZnO. Applying 2DFM to ZnO crystals prepared using different synthetic routes it was possible to show that the synthesis conditions strongly impact defect concentrations with all samples prepared in the presence of peptides having similar defect populations. The findings from these studies can be used to engineer novel binding sequences for peptide-mediated synthesis and begin to study the interplay between the primary sequence and the defect states formed in the synthesised matter.