Fabrication of flower-like silver nanostructures for rapid detection of caffeine using surface enhanced Raman spectroscopy

Flower-like silver nanoparticles, with diameters of 450-500 nm and protrusions on the surface up to 10-15 nm, have been successfully synthesized via liquid phase reduction method, by using ascorbic acid as a reductant and polyvinyl pyrrolidone (PVP) as a surfactant. It is found that the proper coating degree of PVP on silver nuclei leads to anisotropic growth of the silver nuclei resulting in the formation of flower-like structure with more protrusions. Furthermore, when the obtained flower-like silver nanostructure is used as Surface Enhanced Raman Scattering(SERS) substrates, SERS signal is still clearly even if the concentration of R6G solution is reduced down to 10−8 M. The SERS enhancement mechanism of flower-like silver nanostructures in SERS spectroscopy has been further discussed. SERS technology based on the obtained flower-like silver nanostructure substrates can be also used as an effective way to detect caffeine. In this work, it is found that the average intensity of SERS signals at 807 cm−1(NCH), 958 cm−1(Pyrimidine ring) and 1327 cm−1(Imidazole trigonal ring) linear decreased with the −log10C (C is the concentration of caffeine), and the coefficient of determination (R2) is as high as 0.975. This work provides a new way for the quantitative detection of caffeine based on SERS spectroscopy.