The formation of the spherical self-assembly of gold nanoparticles (AuNPs) of 200 ± 20 nm size at the water–chloroform interface is achieved by employing the cyclotetrasiloxane [RSCH₂CH₂SiMeO]₄ (R = CH₂CH₂OH) as the stabilizing ligand. The interfacially stabilized AuNPs act as a versatile catalyst for selective hydrolytic oxidation of only one of the Si–H bonds in secondary organosilanes, RR¹SiH₂ (R, R¹ = alkyl, aryl, and sila-alkyl), to afford the high yield synthesis of 1,1,3,3-tetraorganodisiloxanes, (HRR¹Si)₂O. The study unravels for the first time the role of the photothermal effect arising from the excitation of the surface plasmon resonance of the AuNPs under visible light irradiation in enhancing the catalytic activity at ambient temperature.