Enhanced electrochemiluminescence based on Ru(bpy)32+-doped silica nanoparticles and graphene composite for analysis of melamine in milk

A sensitive electrochemiluminescence (ECL) sensor for melamine analysis was fabricated based on Ru(bpy) 3 2+ -doped silica (Ru(bpy) 3 2+ @SiO 2 ) nanoparticles and graphene composite. Spherical Ru(bpy) 3 2+ @SiO 2 nanoparticles with uniform size about 55   nm were prepared by the reverse microemulsion method. Since per Ru(bpy) 3 2+ @SiO 2 nanoparticle encapsulated a great deal of Ru(bpy) 3 2+ , the ECL intensity has been greatly enhanced, which resulted in high sensitivity. Due to its extraordinary electric conductivity, graphene improved the conductivity and accelerated the electron transfer rate. In addition, graphene could work as electronic channel improving the efficient luminophor amount participating in the ECL reaction, which further enhanced the ECL signal. This proposed sensor was used to melamine analysis and the ECL intensity was proportional to logarithmic melamine concentration range from 1   ×   10 −13   M to 1   ×   10 −8   M with the detect limit as low as 1   ×   10 −13   M. In application to detect melamine in milk, satisfactory recoveries could be obtained, which indicated this sensor having potential application in melamine analysis in real samples.