We report the preparation, characterization, and electrogenerated chemiluminescence (ECL) of rubrene
nanoparticles (NPs) and 9,10-diphenylanthracene (DPA) nanorods. The organic NPs were prepared in an
aqueous phase using a simple reprecipitation method, i.e., injecting a solution of the hydrocarbon in an organic
solvent into water. The resulting NPs can be collected and redispersed to form stable colloidal solutions in
water. Rubrene forms spherical nanoparticles (NPs) (diameter ∼50 nm), while DPA initially forms nanorods
with an average size of ∼500 nm in length and ∼50 nm in diameter. DPA nanorods grew gradually with
time into wires with diameters of ∼1 μm and lengths of ∼10 μm. ECL emission from these NPs was observed
upon electrochemical oxidation in aqueous solutions containing different co-reactants, such as tri-n-propylamine
for rubrene and an oxalate ion for DPA NPs. The ECL intensity from rubrene NPs was significantly higher
than that from DPA NPs because of the smaller size, and thus there is a higher diffusion coefficient for
rubrene as compared to that of DPA NPs.