Spectroscopic study of the pH dependence of the optical properties of a water-soluble molecular photo-switch.

Spectrochim Acta A Mol Biomol Spectrosc

University of Dayton, Department of Chemistry, 300 College Park, Dayton, OH, 45469, USA. Electronic address:

Published: February 2020

In this report we present a UV-Vis spectroscopic study of the pH dependent optical properties of 4,4'-azobenzene dicarboxylic acid in aqueous solution. A combination of chemical (acid-base) and light stimuli is combined to demonstrate that the system undergoes two types of optical switching cycles. At neutral pH the azobenzene undergoes photo-induced cis-trans isomerisation. Upon pH reduction the UV-Vis spectra show changes consistent with aggregation of the azobenzene photo-switch. The photo-responsive behaviour is dependent on the pH and conformation of the azobenzene. The optical properties of the system are dependent on the mode of pH reduction and the isomeric cis/trans composition of the photo-switch, showing hierarchical control of self-assembly.

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http://dx.doi.org/10.1016/j.saa.2019.117576DOI Listing

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