Gap-dependent SERS Effect of Ordered Composite Plasmonic Nanoparticle Arrays and Its Application for Detection of Sodium Saccharin

Sodium saccharin (SS) is usually used in the field of synthetic sweeter food processing. Excessive consumption of SS may cause many health problems. Therefore, it is very necessary to achieve rapid and highly sensitive detection of SS. Here, method based on surface enhanced Raman scattering (SERS) effect using high density ordered gold wrapped polystyrene spheres (Au@PSs) composite plasmonic nanoparticle arrays as substrate, can achieve quantitative detection of SS in aqueous solution within a certain concentration range. The gap distance between two adjacent Au@PSs can be well controlled. Such arrays are fabricated by a magnetron sputtering deposition method on ordered separated PSs arrays manufactured through reactive ion etching (RIE) method. Due to the high density of sub-10 nm gaps contained in such arrays, the structure exhibits strong SERS activity. Finite difference time domain (FDTD) method calculation also confirms that the fabricated substrate possess enhanced electromagnetic field at the gap site. SERS measurement shows that the limit of detection (LoD) for SS is 10(-7) M, which is far below the national standard (<= 5 mg/kg approximate to 2.07 x 10(-5) M). Further study shows a good linear relationship between SERS peak intensity and SS concentration in the range of 10(-7) M similar to 10(-3) M. This study provides a new and highly sensitive SERS substrate for the simple, rapid, low cost and highly efficient detection of the SS.