Construction of a Photonic Crystal Sensor Based on an Amphiphilic Random Copolymer Self-assembled Magnetic Molecularly Imprinted Nanoparticles and Its Application in Tetracycline Detection

KeyWord:magnetic colloidal nanoparticles  magneto-responsive photonic crystal  molecular imprinting technology  tetracycline  amphiphilic random copolymer

Abstract:

      In this paper£¬a naked-eye magnetic molecularly imprinted photonic crystal sensor£¨MMIPCs£© based on magnetic molecularly imprinted nanoparticles£¨MMINPs£© for tetracycline£¨TC£© detection was constructed£¬under the external magnetic field through magnetic assembly of the MMINPs£®The MMINPs were prepared by one-step method through miniemulsion self-assembly£¬with oleic acid modified magnetite nanoparticles as the magnetic cores£¬the amphiphilic random copolymer P£¨St£­co£­VP£© as both the emulsifier and coating£¬and TC as the template molecule£®PVP molecular chain stretched outward to obtain a steric hindrance between magnetic colloidal nanoparticles£¨MCNPs£© owing to the hydrogen bonding between the PVP and water molecules£®A magnetic responsive photonic crystal based on steric hindrance rather than electrostatic interaction as the counterbalance to magnetic attraction was developed£®During the self-assembly of the P£¨St£­co£­VP£© aggregating on the surface of MCNPs£¬the target molecules were added£¬which were imprinted in the coatings of MCNPs£¬relying on the hydrogen bond between PVP and the templates without further polymerization reaction£®The MMINPs was characterized by transmission electron microscopy£¨TEM£©£¬Fourier transform infrared spectoscopy£¨FT£­IR£© and thermal gravimetric analyzer£¨TGA£©£®In FT£­IR spectrum for MMINPs£¬the stretching vibration peaks of C¡ªO indicated the successful imprinting of TC£®TEM showed that the particles were regularly spherical and uniform in size distribution£®The average particle diameter of the MMINPs was around 153.6 nm£®TGA showed that the content of magnetic substance was high to 67.44%£¬which was ascribed to ferromagnetic substance £¨Fe3O4 or Fe2O3£© with high thermal stability£®The preparation conditions of TC£­MMINPs were optimized and the sensitivity£¬response time and the selectivity of TC£­MMIPCs sensors were also investigated£®With the increase of concentration from 1.0 ¡Á 10-4 g/L to 1.0 g/L£¬the reflection wavelength of TC£­MMIPCs redshifts from 500 nm to 578 nm£®The logarithm of the concentration of TC exhibits a linear relationship with the reflection wavelength in this range£®The detection limit£¨S/N = 3£© was 1.0 ¡Á 10-4 g/L and the response equilibrium time of the TC£­MMIPCs sensor did not exceed 30 s£®Such a rapid response was attributed to the surface imprinting£®The imprinting factor of the TC£­MMIPCs was 3.41 and the response was specific with the selection factor of 5.92 for chloramphenicol£¬which is structurally similar to the tetracycline£®TC£­MMIPCs were successfully applied to determine TC in the actual samples£®A brand of soothing moisturizing spray was analyzed£¬the TC content in the moisturizing spray was obtained based on the linear curve of the TC concentration and the reflection wavelength obtained previously£¬and no TC was detected in the moisturizing spray.