In Situ Preparation Of Ag Nanoparticles By Laser Photoreduction As Sers Substrate For Determination Of Hg2+

This paper reports a new way to fast produce surface-enhanced Raman scattering (SERS) substrate within 1 s by in situ photoreduction of AgNO3 and chemical compound containing mercapto group, such as para-aminothiophenol (PATP), dithizone, and 4-mercaptobenzoic acid on filter paper. Ag nanoparticles (Ag-NPs) would form in the area where the laser spot was focused by Raman instrument. In this work, the preparation of Ag-NPs and excitation of SERS signal could be achieved simultaneously within 1 s. However, no SERS signal and Ag-NPs were observed when rhodamine 6G and crystal violet were employed in place of the aforementioned molecules after the same operation. About 0.5 mu MPATP, 5 mu Mdithizone, and 1 mu M4-mercaptobenzoic acid could be fast detected by this method. According to this phenomenon, a fast and sensitive way to detect Hg2+ based on a competitive reaction among PATP, Ag+, and Hg2+ was developed. With the addition of Hg2+, PATP was removed from Ag+ owing to the stronger interaction between -SH and Hg2+. This behavior inhibited the formation of Ag-NPs, leading to a decrease of the intensity of the SERS signal. The decrease of SERS intensity was used to determine the concentration of Hg2+. Under optimal conditions, this methodcanbeutilized todetectHg(2+) at a detectable level of a concentration of 4 nMin aqueous solution. Additionally, the Raman mapping experiment demonstrated good point-to-point repeatability with a relative standard deviation of less than 7%. Therefore, this sensing platform is a promising candidate for fast and real-time mercuric ion detection. Copyright (c) 2016 John Wiley & Sons, Ltd.