Surface Plasmon-Enhanced Kinetics of Molecular Switches

Gold nanohole arrays are proposed as transparent and conductive plasmonic material that accelerates visible-light-triggered chemical reactions including molecular switching.

Diarylethene molecules are discussed as possible optical switches, which can reversibly transition between completely conjugated (closed) and nonconjugated (open) forms with different electrical conductance and optical absorbance, by exposure to UV and visible light. However, in general the opening reaction exhibits much lower quantum yield than the closing process, hindering their usage in optoelectronic devices.

(a) Sketch showing the surface plasmon-enhanced switching kinetics of diarylethene molecules. (b) FDTD simulated 2D electrical field distribution in x−z cross section of the molecular film on gold nanohole arrays. (c) Kinetic characteristics of a molecular film on quartz for opening (orange) and closing (blue) process. (d) Extracted kinetic coefficients of opening process at maximum of extinction for quartz, Au, and hAu substrates plotted versus the transmission of the bare substrate.

Bohdan Lenyk in the collaboration with coworkers from the University of Konstanz introduced the plasmonic field enhancement of gold films perforated with nanoholes to enhance the opening process, which is supported by visible light, Figure (a). Nanohole arrays were chosen as plasmonic electrodes to facilitate not only plasmon excitation but also a high conductance and transparency which are crucial for optoelectronic applications. The electrodes with hexagonal lattices of nanoholes revealed strong optical transmission in the visible range (∼60%) and pronounced enhancement of field intensities, Figure (b).

Different lattice constants were utilized to investigate the contribution of SPP on the switching kinetics, Figure (c), and to optimize them for the molecules under study. The researchers confirmed that the enhancement effect is strongest when the SPP resonance and the molecular absorption are located in the same wavelength range. The experimental UV−vis measurements were verified with finite-difference time-domain simulation confirming an SPP-induced enhancement (up to 50% compared to quartz substrate) of the switching kinetics of the opening reaction, Figure (d).

Publication: B. Lenyk, V. Schöps, J. Boneberg, M. Kabdulov, T. Huhn, E. Scheer, A. Offenhäusser, D. Mayer. Surface Plasmon-Enhanced Switching Kinetics of Molecular Photochromic Films on Gold Nanohole Arrays. Nano Lett. 2020


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Last Modified: 21.12.2021