It was found that silver nanoparticles could strongly enhance the chemiluminescence (CL) of the luminol-KIO 4 system in the presence of Co 2+ . The most intensive CL signals were obtained with silver nanoparticles in diameter of 22 nm. The studies of UV-visible spectra and CL spectra were carried out to explore the possible CL enhancement mechanism. Moreover, the influences of 17 amino acids and 25 organic compounds on the luminol-KIO 4 -Co 2+ -Ag NPs CL system were studied by a flow injection procedure, which led to an effective method to detect these compounds. KeywordsFlow Injection, Luminol, Chemiluminescence, Silver Nanoparticle * Corresponding author. nanoparticles, especially metal nanoparticles, as catalysts for the chemiluminescence system has attracted considerable interest.Recently, the combination of nanoparticles with chemiluminescence has attracted substantial interest because the noble metal nanoparticles have been found to participate in CL reactions as a catalyst, reductant, luminophor, and energy acceptor [20] [21]. For example, Lin et al. [22] [23] have reported that metal nanoparticles can enhance the CL of the luminol-H 2 O 2 and NaHCO 3 -H 2 O 2 system. Cui's group applied noble metal nanoparticles to the CL reactions of lucigenin and potassium permanganate system [24] [25].In this study, we examined the response of Ag NPs for CL intensity of the luminol-KIO 4 -Co 2+ system. The prepared Ag NPs displayed much stronger catalytic activity in presence of Co 2+ on the luminol CL than single Ag NPs or Co 2+ . The effects of reaction conditions on the CL intensity were examined. Moreover, the possible enhancement mechanism of Ag NPs on luminol-KIO 4 -Co 2+ CL reaction was investigated in terms of the UVvisible and CL spectra in detail. In addition, the influences of amino acids and organic compounds on the luminol-KIO 4 -Co 2+ -Ag NPs CL system were reported in extension. Experimental Section Reagents and MaterialsAll chemicals and reagents were analytically pure and used without further purification, and the deionized and triple-distilled water was used throughout.A 2.5 × 10 −2 mol•L −1 stock solution of luminol (3-aminophthalhydrazide) was prepared by dissolving luminol (Fluka) in 0.1 mol•L −1 sodium hydroxide solution. Working solutions of luminol were prepared by diluting the stock solution with water. The 1.0 × 10 −2 mol•L −1 stock solution of periodate was prepared by dissolving 0.23 g KIO 4 (Shanghai, China) in 0.01 mol•L −1 sodium hydroxide solution, and stored in a brown bottle to avoid photochemical decomposition. Silver nitrate, trisodium citrate, hydroborate, amino acids and organics were obtained from Sinopharm Group Chemical Reagent Co. Ltd. (Shanghai, China).