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R. Oliveira Conceição, H. Hoffmann, M.D. Mihovilovic:
"Azobenzene Cis Immobilization: A New Practical Approach To Obtain Azobenzene Light Responsive Surfaces";
Poster: 14th International conference on materials chemistry (MC14), UK; 08.07.2019 - 11.07.2019; in: "14th International conference on materials chemistry (MC14)", Royal Society of Chemistry, Birmingham, England, UK (2019), S. 240.

In recent years, light responsive surfaces have attracted interest due to their ability to reversibly change their
properties in response to light, a non-invasive and highly precise spatial and temporal stimulus. 1,2 One way to
achieve this light response is by coating the surface with a photoswitch, a chemical entity that after the absorption
of a photon suffers a reversible chemical reaction. One of the most used photoswitches for this purpose are
azobenzenes, thanks to their high quantum yields, fast photoisomerization rates and resistance to optical fatigue.
3
Although it may sound fairly simple, the coating of a surface with an azobenzene is not a trivial process since
when the molecules are too tightly packed isomerization is prevented by steric hinderance or electronic coupling
between the molecules and the surface.4 Therefore, the immobilization of the azobenzene is normally performed
using a quite diluted reaction mixture or/and a mixed approach, where the azobenzene is immobilized together
with another molecule not capable of switching, which acts as a spacer.5 In both strategies, the optimization
process can be quite tedious and time consuming, requiring the test of several azobenzene concentrations,
reaction times and
In this work, we present another strategy to circumvent this problem, the immobilization of the azobenzene while
on the most space demanding configuration, the cis isomer. For this purpose, an azobenzene was immobilized
on a silicon surface using a reaction mixture previously irradiated with 365 nm to switch the azobenzene to the cis
configuration. After immobilization, the switching was checked by water contact angles measurements.
References
1. Zhang, J., Ma, W., He, X. P. & Tian, H. Taking Orders from Light: Photo-Switchable Working/Inactive Smart Surfaces for
Protein and Cell Adhesion. ACS Appl. Mater. Interfaces 9, 8498-8507 (2017).
2. Browne, W. R. & Feringa, B. L. Light switching of molecules on surfaces. Annu. Rev. Phys. Chem. 60, 407-428 (2009).
3. Szymański, W., Wu, B., Poloni, C., Janssen, D. B. & Feringa, B. L. Azobenzene photoswitches for staudinger-bertozzi
ligation. Angew. Chemie - Int. Ed. 52, 2068-2072 (2013).
4. Russew, B. M. & Hecht, S. Photoswitches : From Molecules to Materials. Adv. Mater. 22, 3348-3360 (2010).
5. Liu, D., Xie, Y., Shao, H. & Jiang, X. Using azobenzene-embedded self-assembled monolayers to photochemically control
cell adhesion reversibly. Angew. Chemie - Int. Ed. 48, 4406-4408 (2009).

https://publik.tuwien.ac.at/files/publik_286001.pdf