Study On Piezoelectric And Optical Properties Of Peptide Nanomaterials

Peptide-based materials are important biomaterials with natural bioaffinity and have a wide range of applications in the field of biofunctional nanomaterials.Since peptides have complex amino acid sequences,the structural and functional diversity of peptide-based materials formed by self-assembly can be adjusted by chemical modification and regulation of temperature,solution pH and other parameters during self-assembly.For example,peptides containing aromatic amino acids can be assembled into peptide-based materials with excellent electrical and optical properties,such as piezoelectric and fluorescence properties,through aromatic interaction and the construction of hydrogen bond networks.Among them,amyloidβ(Aβ)peptides are easy to form stable and ordered self-assembly,and the structure and properties of their self-assembly are the focus of current research.The researches show that the core sequence of Aβ is KLVFF,which plays a key role in the self-assembly process.Therefore,this thesis mainly explores the self-assembly of KLVFF and its derived sequences,and studies the piezoelectric and optical properties of peptide assembly materials with different structures.The content of the thesis is divided into the following parts:In Chapter 1,introduction.The self-assembly mechanism,research status and functional application of peptide materials are briefly introduced,and the research progress of piezoelectric properties of peptide assembly materials is introduced by combining piezoelectric force microscope based on atomic force microscopy technology.In addition,we introduce the optical properties of peptide materials.Finally,we summarize the topic and significance of this thesis.In Chapter 2,we acetylate KLVFF to obtain rod-like peptide crystals.Optical microscopy and transmission electron microscopy are used to characterize the overall morphology of peptide crystals.The Young’s modulus and adhesion of peptide crystals are tested by atomic force microscopy,and the informations of mechanics and height at the microscopic scale are obtained,and the results show that the peptide crystals have a regular and ordered crystal structure.The piezoelectric tests of the crystal by piezoelectric force microscope show that it have intrinsic piezoelectricity,spontaneous polarization,and the out-of-plane response has a significant dependence on voltage.In addition,nonlinear optical measuring instrument and fluorescence microscopy tests show that peptide crystals have good optical properties.The researches in this chapter provide theoretical support for the design of novel biological piezoelectric devices.In Chapter 3,based on the above amino acid sequence,two amino acids are added to obtain an assembly of KLVFFAL nanotubes.Fourier transform infrared spectroscopy is used to study the relationship between the assembly process and the secondary structure of peptides,indicating that the self-assembly behavior of peptides is driven by aromatic group interaction.Transmission electron microscopy characterization determines the structural characteristics of peptide self-assembled nanotubes.Out-of-plane images of piezoelectric force microscopy show the different polarization responses of nanotubes at the same height and in the same arrangement direction.Nonlinear measuring instrumentation reveals the properties of third-order nonlinear optics of nanotubes.This chapter has guiding significance for the study of piezoelectric properties of nanotube materials.In Chapter 4,based on the KLVFF sequence,two phenylalanines with aromatic groups are added,and the FFKLVFF peptide fiber is self-assembled.The secondary structure information of peptide fibers is obtained by fourier transform infrared spectroscopy and circular dichroism.The height and phase diagrams of the atomic force microscopy show the uniformity of the film layer composed of fibers.Piezoelectric force microscopy tests the polarization flipping of the film layer,which proves that the film layer has an off-plane piezoelectric response,and its piezoelectric response image proves the uniformity of the film layer.In addition,we explore the properties of fluorescence and nonlinear optics.The research in this chapter provides guidance for studying the piezoelectric properties of peptide fiber coatings,and enriches our understanding of peptide self-assembly materials.