Chemiluminescence of off-line and on-line gold nanoparticle-catalyzed luminol system in the presence of flavonoid.

Abstract

It was found that flavonoids could remarkably inhibit the chemiluminescence (CL) intensity of an off-line gold nanoparticle (AuNP)-catalyzed luminol-H2 O2 CL system. By contrast, flavonoids enhanced the CL intensity of an on-line AuNP-catalyzed luminol-H2 O2 CL system. In the off-line system, the AuNPs were prepared beforehand, whereas in the on-line system, AuNPs were produced by on-line mixing of luminol prepared in a buffer solution of NaHCO3 -Na2 CO3 and HAuCl4 with no need for the preliminary preparation of AuNPs. The on-line system had prominent advantages over the off-line system, namely a lowering of the background noise and improvements in the stability of the CL system. The results show that differences in the signal suppression effect of flavonoids on the off-line AuNP-catalyzed CL system are influenced by the combined action of a free radical scavenging effect and occupy-sites function; the latter was proved to be predominant using controlled experiments. Enhancement of the on-line system was ascribed to the presence of flavonoids promoting the on-line formation of AuNPs, which better catalyzed the luminol-H2 O2 CL reaction, and the enhancement activity of the six flavonoids increased with the increase in reducibility. This work broadens the scope of practical applications of an AuNP-catalyzed CL system.