Beyond Plasmonic expectations: Micellar confinement governs the Norrish type I reaction in hybrid micelle‐gold nanoparticle systems

Spin-dependent photochemical mechanisms are central to understanding how external stimuli, such as light, temperature, and magnetic fields, modulate chemical reactivity. In this study, the photolysis of the asymmetrical ketone 4-methyldibenzyl ketone (MDBK) was investigated in cetyltrimethylammonium chloride (CTAC) micelles and in hybrid gold nanoparticle (AuNP) systems under UVB and combined UVB-red light irradiation. The objective was to assess whether plasmonic AuNPs could alter product distribution or influence radical pathways relative to micellar media alone. Photoproduct analysis revealed that the incorporation of AuNPs did not induce measurable variations in the product ratios, and the calculated cage effect remained comparable to that observed in pure CTAC micelles. This outcome demonstrates that micellar confinement remains the dominant factor controlling radical recombination in MBDK photolysis, even in hybrid plasmonic environments. By defining the regime in which nanoparticle-induced perturbations are negligible, this work provides a mechanistic baseline and guides future efforts to identify conditions conducive to plasmon-radical coupling.