Ordered silver nanoparticle arrays as surface-enhanced Raman spectroscopy substrates for label-free detection of vitamin C in serum

A porous anodic aluminum oxide (AAO) template is fabricated using two-step anodization technology. The Ag nanostructure arrays are realized by electron beam evaporating a thin layer of silver onto the porous side of the AAO template. The device as a robust and cost-efficient surface-enhanced Raman scattering (SERS) substrate is used for label-free detection of vitamin C in serum. This substrate produces a high Raman signal due to its periodic hexagonal arrangements. The nanostructures have sharp edges to bring about a further enhancement to the local electromagnetic field. The partial least squares (PLS) regression method is applied on measuring vitamin in serum within physiological levels. In comparison with other methods of measuring vitamin C, our method provides the advantages of high precision and simple way in physiological levels. The error of vitamin C concentration is less than 0.04 μmol/L between measurement by Raman spectrum and by high performance liquid chromatography (HPLC).