Necklace-like molecularly imprinted nanohybrids based on polymeric nanoparticles decorated multi-walled carbon nanotubes for highly sensitive and selective melamine detection.

In this study, molecularly imprinted nanohybrids with "necklace-like" nanostructures were developed based on self-assembled polymeric nanoparticles decorating multi-walled carbon nanotubes (MWCNTs) by employing melamine as template molecules. An amphiphilic copolymer poly(acrylic acid-co-(7-(4-vinylbenzyloxy)-4-methyl coumarin)-co-ethylhexyl acrylate) (poly(AA-co-VMc-co-EHA), PAVE) containing photosensitive coumarin units was synthesized firstly. Then, the PAVE copolymers were co-assembled with MWCNTs in the presence of template molecules, generating photosensitive molecularly imprinted nanohybrids (MIP-MWCNTs) with "necklace-like" structures. Subsequently, the MIP-MWCNTs nanohybrids were used to modify electrode surface followed by photo-polymerization of the coumarin units in the nanohybrids, leading to a network architectured complex film. After extracting melamine molecules by electrolysis, a melamine MIP sensor was successfully developed. The as prepared sensor exhibited a significantly wide linear range (1.0×10-12 mol L-1 ~ 1.0×10-6 mol L-1) and a low detection limit (5.6×10-13 mol L-1) for melamine detection. High selectivity of the sensor toward melamine was well demonstrated with respect to other melamine analogues and interferents. Furthermore, the MIP sensor showed high stability and reproducibility. The excellent performance of the MIP sensor can be attributed to the unique nanostructure of the complex film provided by these "necklace-like" nanohybrids. On one hand, the nanosized polymeric MIP nanoparticles (NPs) along the MWCNTs increase the effective electrode surface area and thus offer high melamine binding capacity. On the other hand, the MWCNTs in MIP-MWCNTs nanohybrids serve as "electronic bridges" to accelerate the electron transfer among the complex MIP film. More importantly, the MIP sensor was practically used to monitor melamine in milk samples, demonstrating a promising feature for applications in food analysis like milk and other food products including milk powder, infant formula and animal feed. Considering the ease of polymeric nanoparticles functionalization, the "necklace-like" nanohybrids would be extended to wider applications in many other sensors and devices.