Enhanced trans‐to‐cis photoisomerization quantum yield of azobenzene spatially confined in silver nanoparticle aggregates

Abstract

Photoisomerization of azobenzene spatially confined in silver nanoparticle (AgNP) aggregates and in ethanol solution was monitored by Raman spectroscopy inside optically clear colorimetric dishes. After ultraviolet irradiation, overall Raman intensity assigned to trans-azobenzene of these two samples decreased, and notably, a cis peak appeared at 599 cm −1 , assigned to C─N═N─C torsional mode. The Raman intensity at 1,007 cm −1 , assigned to trans-azobenzene, was recorded versus irradiation time for analyzing the trans-to-cis photoisomerization quantum yield (PQY). By combining our theoretical derivation and standard curve of Raman spectra, the trans-to-cis PQY of azobenzene in AgNP aggregates was roughly calculated to be 79.0% higher than that in ethanol solution. The enhancement mechanism was discussed in terms of the competition between enhanced local optical field from surface plasmon resonance and the accelerated nonradiative decay of excited azobenzene molecules together. K E Y W O R D Sabsorption spectrum, azobenzene, photoisomerization quantum yield, Raman spectroscopy, silver nanoparticles

A Study in Red: The Overlooked Role of Azo‐Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

“…A comparative analysis of UV Raman and FTIR spectra shows multiple strongly Raman active modes that are not visible in the IR spectrum 1578, 1389, 1285 and 589 cm À 1 . These can be attributed to N=N stretching, [47] N=N in trans-aromatic azo compounds, azoxy groups [34a] and CÀ N=N stretching combined with a CÀ N deformation vibrations, [48] respectively. The observed bands at 1389 and 589 cm À 1 are especially indicative of a trans-azo moiety inside the R-CN x -KS (i. e., in the solid obtained by slow evaporation of the R-CN x -K solution that was obtained after filtering off the tri-potassium cyamelurate crystals from the concentrated product solution of the R-CN x dissolution in KOH).…”

Azobenzene isomerization in condensed matter: lessons for the design of efficient light-responsive soft-matter systems

“…157 Azobenzene derivatives have also been considered in many other mixed systems with substrates including graphene 158,159 and graphene oxide, 160,161 polyelectrolytes, 162,163 and metal surfaces. [164][165][166][167] Conveniently, some metal nanocrystal systems are well positioned for in situ monitoring using surface enhanced Raman spectroscopy (SERS). 166,167 Photoisomerization can be observed these systems, which in contrast to the deactivation observed for surface interactions with some SAMS, can be speculated to be largely because of the presence of photosurfactants both on the surface and in bulk solution.…”

“…[164][165][166][167] Conveniently, some metal nanocrystal systems are well positioned for in situ monitoring using surface enhanced Raman spectroscopy (SERS). 166,167 Photoisomerization can be observed these systems, which in contrast to the deactivation observed for surface interactions with some SAMS, can be speculated to be largely because of the presence of photosurfactants both on the surface and in bulk solution. Therefore, similar to the conclusion made by Santer et al, the design of the azobenzene chromophores can be largely independent of the target substrate.…”

“…157 However, interactions cannot be completely discounted as the example systems used for SERS experiments indicate that surface interactions can have implications for the isomerization kinetics and photo-stationary states. 166,167 Surface interactions, to some extent, inhibiting or influencing the rate of trans to cis isomerization, set up a system with interplay between two isomerization rates (K surf and K sol ) and rates of adsorption and desorption from the surface (K ad and K de respectively in Fig. 8).…”

A Study in Red: The Overlooked Role of Azo-Moieties in Polymeric Carbon Nitride Photocatalysts with Strongly Extended Optical Absorption

“…A comparative analysis of UV Raman and FTIR spectra shows multiple strongly Raman active modes that are not visible in the IR spectrum 1578, 1389, 1285 and 589 cm -1 . These can be attributed to N=N stretching, [47] N=N in trans-aromatic azo compounds, azoxy groups [34a] and C-N=N stretching combined with a C-N deformation vibrations, [48] respectively. The observed bands at 1389 and 589 cm -1 are especially indicative of a trans-azo moiety inside the R-CNx-KS (i.e., in the solid obtained by slow evaporation of the R-CNx-K solution that was obtained after filtering off the tri-potassium cyamelurate crystals from the concentrated product solution of the R-CNx dissolution in KOH).…”