Udo Bach Research Group

Nanofabrication

Size-selective separation of gold-nanoparticles

We have introduced a new simple and scalable method to quantitatively separate nanoparticles according to size. This was achieved by fine-tuning the microforces that dictate the colloidal stability of nanoparticle solutions. The ionic strength of the medium used to disperse charge-stabilized nanoparticles is critically important for their colloidal stability. The functionalized AuNPs show steep onsets of colloidal instability as a function of salt concentration in aqueous dispersions. The surface modification further renders the nanoparticles highly biocompatible while offering a convenient way to couple biomolecules such as proteins or amino-functionalized DNA strands to the nanoparticle, e.g. for biolabeling purposes. These results have been published in Chemical Communications.

Templated placement of individual nanoparticles onto surface nanopatterns through DNA-directed self-assembly

Monodisperse nanoparticles with complex heterostructures and shapes can be synthesized in bulk quantities, leading to complex nanoscale architectures that cannot be produced by nanolithographic methods. This project aims to bridge the gap between top-down lithography and bottom-up synthetic strategies by offering a method to place individual nanoparticles into prefabricated lithographic patterns. To do so, we have studied the templated assembly of DNA capped gold nanoparticles onto surface nanopatterns fabricated by electron beam lithography with the aim to control the assembly of individual nanoparticles into discrete arrays. These results have been published in ACS Nano. Collaboration: Lawrence Berkeley National Labs (USA).

Stamping of nanoparticle assemblies

We recently have been successful in transferring nanoparticle nanostructures from a master (stamp) to a non-patterned host substrate with excellent transfer efficiency. These results have been published in Angewandte Chemie International Edition. Collaboration: Lawrence Berkeley National Labs (USA).

DNA-Directed Nanofabrication

This research project aims to combine top-down nanopatterning and bottom-up self-assembly strategies to develop an entirely novel fabrication approach. This method will allow the accurate placement of nanoparticles (quantu dots) into pre-defined structures (quantum dot particles). The self-assembly process will be templated by a nanostructured surface and allows to produce large numbers of these predefined nanostructures in repetitive production cycles. Collaboration: Lawrence Berkeley National Labs (USA).