This paper shows that the photodimerization of 4-aminothiophenol (PATP) into dimercaptobenzene (DMB), a “gold standard” reaction in plasmon chemistry, can be achieved by sandwiching a PATP solution between a gold mirror and a micron-sized silica sphere. This is a version of the classical sphere-on-mirror configuration, which has been extensively utilized in recent years for Raman detection and photocatalysis [see, e.g., Nano Letters 12, 4242-4246 (2012) and RSC Advances 4, 38152-38158 (2014)]. In this configuration, the sphere acts as a lens focusing light toward the interface with the mirror, enabling locally enhanced Raman signals and faster chemical reactions.
 
Here the main point of novelty is given by the introduction of metal organic framework nanoparticles (specifically the so-called ZIF-8 system) between the mirror and spherical microlens. ZIF-8 particles allow for increasing the local concentration of PATP, which is the key for taking full advantage of the lens effect. This configuration enables simultaneous activation and Raman monitoring of the reaction. Although the general mechanism at the basis of the improved reaction kinetics is still to be elucidated, the dependence on both ZIF-8 and lens size suggests that geometrical parameters are actually the main players in managing optically-assisted reactions. These results further corroborate those of a recent paper where the same reaction has been run under optical assistance in the absence of plasmons. [see Angewandte Chemie International Edition 61, e202205013 (2022)]

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