A higher generation dendron with a long-alkyl chain thiol (DA2–SH) induced the formation of nanoparticles with a small core with quite a narrow size distribution (1.5 ± 0.1 nm), the self-assembly of one-dimensional arrays of these gold nanoparticles (DA2–Au), and the stabilization for the formation of the radical cation of the phenothiazine of DA2–Au nanoparticles from the interfacial one-electron oxidation of the nanoparticles with NOBF4.