Research Group Prof. Dr. G. Friedrichs

Properties of Photoswitchable Functionalized Surfaces

Functionalization of surfaces with photochromic molecular switches enables external control of interfacial properties. Consequently, photoswitchable molecular systems have found many applications in nanotechnology, biotechnology, and material sciences.

VSFG-Study of Azobenzene Based SAMs

abswitch1_webAs part of a subproject of the Collaborative Research Center “Function by Switching” (SFB 677), the inherently surface-sensitive Vibrational Sum-Frequency Generation (VSFG) spectroscopy has been applied as a powerful technique to investigate the molecular structure and photoswitching efficiency of functionalized surfaces. Systematic studies on pure and mixed (i.e., “diluted” with simple alkylthiols) self-assembled monolayers (SAMs) help to unravel the effects of steric hindrance and energy dissipation, which are known to degrade the switching efficiency.

VSFG is employed to monitor the morphology and switching properties of azobenzene based SAMs on gold. As a prerequisite for a detailed assessment of the switching efficiency, knowledge of morphological aspects such as possible phase separation, available free volume, and the orientation of the molecular switch is necessary. For example, Methylazobenzene-O-undecanethiol (MeAB) has been used as the molecular switch with the methyl substituent serving as a sensitive VSFG marker to measure the trans-cis switching state of the AB moiety. Upon “dilution” of the surface with different co-ligands, due to the loss of lateral and axial structural order, the SFG spectrum changes significantly.


Contributing Researchers: Saira Riaz and Gernot Friedrichs