Luminol-silver nitrate chemiluminescence enhancement induced by cobalt ferrite nanoparticles

CoFe2O4 nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO3, resulting in a strong CL emission. The UVvisible spectra, X-ray photoelectron spectra and TEM images of the investigated system revealed that AgNO3 was reduced by luminol to Ag in the presence of CoFe2O4 NPs and the formed Ag covered the surface of CoFe2O4 NPs, resulting in CoFe2O4Ag coreshell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO3 and CoFe2O4 NPs was fast at the beginning and slowed down later. The CL spectra of the luminol-AgNO3-CoFe2O4 NPs system indicated that the luminophor was still an electronically excited 3-aminophthalate anion. A CL mechanism has been postulated. When the CoFe2O4 NPs were injected into the mixture of luminol and AgNO3, they catalyzed the reduction of AgNO3 by luminol to produce luminol radicals and Ag, which immediately covered the CoFe2O4 NPs to form CoFe2O4Ag coreshell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe2O4 NPs, the catalytic activity of the coreshell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles. Copyright (C) 2011 John Wiley & Sons, Ltd.