Ultrasensitive SERS Substrate Integrated with Uniform Subnanometer Scale “Hot Spots” Created by a Graphene Spacer for the Detection of Mercury Ions

Mercuric ion (Hg2+) is one of the most toxic and serious environment polluting heavy metal ions, which can be accumulated in human body through food chains and drinking water, and causes serious damage to human organs. Therefore, development of the efficient and sensitive method for detection of Hg2+ is very necessary. In this study, the high surface sensitivity and fingerprint information about the chemical structures based on surface‐enhanced Raman scattering (SERS) for sensing applications are taken advantage of. Au triangular nanoarrays/n‐layer graphene/Au nanoparticles sandwich structure with large‐area uniform subnanometer gaps are fabricated and used to detect Hg2+ in water via thymine–Hg2+–thymine coordination; the detection limit of Hg2+ is as low as 8.3 × 10−9m. Moreover, this SERS substrate is used to detect the Hg2+‐contaminated sandy soil and shows excellent performance. This study indicates the sandwich structure has a great potential in detection of toxic metal ions and environmental pollutants. Ultrasensitive surface‐enhanced Raman scattering (SERS) substrate with large‐area uniform subnanometer “hot spots” is used to detect mercuric ion in water and sandy soil; the detection limit is as low as 8.3 × 10−9m. The uniformity of the SERS substrate is proved by Raman mapping, and the physical mechanism of SERS enhancements is supported by the finite difference time domain method.