Applications of Functional One-Dimensional Nanostructures Studied by Light Scattering

Abstract

One-dimensional (1D) nanocrystals represent a versatile and functional class of materials characterized through a high transport efficiency along the long axis, and a confined cylindrical surface. Silver nanowires (Ag-NWs) are excellent building blocks for 2D conductive networks, which are used as functional fillers in 3D printing polymer composites. The morphology of randomly oriented Ag-NWs is studied as a function of concentration, as well as during external modifications and within a polymer matrix by, inter alia, grazing incidence X-ray scattering. Flexible and conductive Ag-NW composites are fabricated and investigated under mechanical stress. Key network properties are revealed by a Monte Carlo based model. The electrical nanowire network, dominated by the tunneling resistances between the nanowires, strongly interacts with the supporting polymer matrix. A 3D-printed flexible capacitor is demonstrated as a prototype for 3D-printed flexible electronic devices. Furthermore, in order to investigate the low-energy excitation spectrum as well as the interaction between the electronic system with lattice degrees of freedom within 1D nanostructures, Raman spectroscopy is utilized. We developed a Raman microscope with ultra-small spot sizes down to 200nm - 300nm to study local phenomena on the nanoscale. Surface enhanced Raman spectroscopy (SERS) is used to study a chemical selective system based on the electronic transitions between semiconducting zinc oxide nanowires and 4-mercaptopyridine. Plasmonic enhancements of the Raman response are observed in nanowires of the topological insulator Bi2Se3 as a function of wire diameter. The modification of the quasi-relativistic surface states by geometrical confinement from 2D to 1D results in a gap opening of the spin-polarized Dirac-states as a consequence of the formation of a Spin-Berry phase.