Stable Ag@oxides nanoplates for surface-enhanced Raman spectroscopy of amino acids.

Surface enhancement Raman scattering (SERS) is a powerful technique for detecting low-concentration analytes (chemicals and biochemicals). Herein, a high-performance SERS biosensing system has been created by using highly stable Ag@oxides nanoplates as enhancers. The Ag nanoplates were stabilized by coating a uniform ultrathin layer of oxides (SiO2 or TiO2) on the Ag surface through a simple sol-gel route. The thin oxide layer allows the plasmonic property of the original Ag nanoplates to be retained while preventing their contact with external etchants. The oxides provide an excellent platform for binding all kinds of molecules that contain a COOH group in addition to a SH group. We demonstrate that Ag@oxides have high performance with respect to the typical SERS molecule 4-ATP, which contains a typical SH group. Ag@oxides also can be directly employed for the SERS detection of amino acids. The highly stable Ag@oxides nanoplates are believed to hold great promise for fabricating a wide range of biosensors for the detection of many other biomolecules and may also find many interesting opportunities in the fields of biological labeling and imaging.