NPs (average radius ∼50 nm) of two ECL emitters, rubrene
and DPA, were synthesized and characterized. ECL of these
dispersed NPs was observed in aqueous 0.1 M NaClO4 solutions
containing suitable co-reactants. Rubrene formed spherical NPs,
which were stable for at least one week in the dark with no
significant aggregation, while DPA NPs first formed nanorods,
which grew into nanowires within a week due to the instability
of the initially formed NPs. The ECL intensity from the rubrene
NPs was sufficient to suggest their use as labels for ECL
analytical methods. However, we are attempting the preparation
of smaller particles. The addition of surfactant generates smaller
NPs; however, surfactant decreases the ECL intensity, probably
because it interferes with electron transfer reactions at the NP
surface. Alternative approaches are being investigated.