Contactless dye-sensitised nano-photoelectrodes assembled at polarisable liquid|liquid interfaces exhibit photocurrent responses originating from the heterogeneous photooxidation of ferrocene by the colloids. The photocurrent spectra of the nanoparticle assembly sensitised by alizarin indicate that the photoreaction is initiated by an ultrafast electron injection from the dye into the conduction band of the TiO2 particles, followed by heterogeneous electron transfer from ferrocene to the oxidised dye, as shown.