Metal-organic nanowires

Metal-organic nanowires exhibit not only the properties of one-dimensional structures including ultra-small scale, large surface-to-volume ratio etc., but also obvious advantages in their tunable properties and label-free sensing ability by optical or electrical readout. Thus, the evaluation of metal-organic materials by the use of transition metal ions and organic ligands including tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) were focused in this thesis. Concerning the synthesis of metal-organic nanowires, microfluidics offers various benefits, e.g. laminar flow, reduced sample/reagent consumption and control of self-assembly of nanostructures. Therefore, microfluidic techniques have been mainly applied to the synthesis and application of nano-/microstructures. In the first part of this thesis, label-free biosensors based on in situ formed and functionalized gold-tetrathiafulvalene (Au-TTF) wires were developed using an integrated microfluidic system. Au-TTF microwires were formed and immobilized inside the microchip. Then, different surface modification protocols were applied to modify Au-TTF wires which were used for sensitive label-free detection of catecholamines and human IgG by Raman spectroscopy. Following, a study of molecular self-organization in individual Au-TTF nano-/microwire by polarized confocal Raman spectroscopy was performed to understand the growth mechanism of Au-TTF. Single nanowires were analysed using non-destructive polarized Raman spectroscopy. Angular polarization Raman measurement of a single TTF crystal and single nanowire showed the periodic variations in typical Raman bands, indicating preferential ordering of molecules in both crystal and Au-TTF wire. Based on the density functional theory (DFT) calculation and simulation of depolarization ratio, the molecular assembly in a single TTF crystal was confirmed. The tilted stacking of TTF units in single Au-TTF nanowire along the long axis was also proved. Afterwards, the formation of fibres and particles made of metal salts and TTF derivatives on a microfluidic device and in a conventional reaction flask was investigated. Their morphologies, optical properties and electrical conductivities were characterized. This study provides a comprehensive overview of the morphologies of the products obtained from reactions between metals and different commercially available TTF derivatives. Finally, a microfluidic-assisted synthesis of copper-tetracyanoquinodimethane (Cu-TCNQ) nanostructures based on TCNQ was performed. A two-layer microfluidic device comprising parallel actuated microchambers was used for the synthesis, and enabled the excellent fluid handling for the continuous and multiple chemical reactions in confined ultra-small chambers. The as-prepared Cu-TCNQ wire bundles showed good conductivity and hysteresis reversing memory effect, which proved the possibility in using them to build advanced nanoelectronics.

Author dc:creator

• Xing, Yanlong

Advisor dc:contributor.advisor

• Esser, Norbert

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-5576

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/5989