Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump–probe Brewster angle reflectometry

Siebenhofer, Bernhard, Gorelik, Sergey, Lear, Martin J. , Song, Hong Yan, Nowak, Christoph and Hobley, Jonathan (2013) Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump–probe Brewster angle reflectometry. Photochemical & Photobiological Sciences, 12 (5). pp. 848-853. ISSN 1474-905X

Full content URL: http://dx.doi.org/10.1039/c3pp25397j

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Abstract

Self-assembled monolayers of 11-(3’,3’-dimethyl-6,8-dinitrospiro[chromene-2,2’-indoline]-1’-yl) undecanoic acid (amphiphilic spiropyran) at the air–water interface are studied using Brewster angle reflectometry. Transient kinetics of the spiropyran to merocyanine conversion are recorded in a UV-pump, VIS-probe configuration. By varying the probe wavelength using an optical parametric oscillator, we are able to reconstruct absorption spectra of intermediate states with a time-resolution of 10 nanoseconds, limited by the temporal convolution of the two laser pulses. After UV irradiation, spiropyran converts to merocyanine in two stages. The first occurs within a timescale of several tens of nanoseconds and is heavily convoluted with the system response time, whereas the second stage occurs over a few hundred nanoseconds. During the rise time there is a small red shift in the transient absorption spectrum of ∼20 nm. We assign the red shift and the slower kinetics to the isomerization of a merocyanine isomer cis about the central methine bond to those that are trans about the same bond.

Keywords:Brewster angle reflectometry, Spiropyran, Merocyanine, Self-assembled monolayers
Subjects:F Physical Sciences > F200 Materials Science
F Physical Sciences > F170 Physical Chemistry
F Physical Sciences > F160 Organic Chemistry
Divisions:College of Science > School of Chemistry
ID Code:17132
Deposited On:23 Apr 2015 11:21

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