Surface Enhanced Raman Spectroscopy (SERS) Detection of β-Estradiol in Milk by Molecularly Imprinted Polymers on Biogenic Silica and Silver Nanoparticles
The highly sensitive surfaced-enhanced Raman spectroscopy (SERS) and the directive selection of molecularly imprinted polymers (MIP) provided a simple and rapid method to detect the content of β-estradiol in milk sample which exists in low concentration at natural level. The MIPs were synthesized by surfacepolymerization of β-estradiol (template), methacrylic acid (the monomer), and ethylene glycol dimethacrylate (cross-linking agent), with 4,4’ azobis (4-cyanopentanoyl) chloride initiator convalently grafted on the biogenic silica surface. The NIPs were also synthesized in a similar version to MIPs, but polymerization done without β-estradiol template. The surface morphology of MIPs and NIPs by scanning electron microscopy (SEM) showed a clear difference on their structures. Silver and silica nanoparticles were served as SERS active substrates for signal enhancement. The limit of detection (LOD) for MIPs-silver nanoparticles was 1.0 ppm, whereas for MIPs-silica, the LOD was 0.73 ppm. As the result, biogenic silver nanoparticles gave a more enhanced Raman signal compared to the conventional silica nanoparticles.
* Indicates faculty mentor.