Rationally designed SERS AgNPs/GO/g-CN nanohybrids to detect methylene blue and Hg2+ ions in aqueous solution

[Display omitted] •An excellent plasmonic AgNPs/GO/g-CN SERS substrate was developed and demonstrated for SERS application.•High enhancement in Raman signal by highly delocalized electronic cloud of AgNPs/2D matrixes was observed.•Selective detection of Mercury and its plausible mechanism was investigated.•The SERS substrate exhibited admirable enhanced sensing and signal reproducibility, and has noteworthy for SERS applications. The newly developed AgNPs/GO/g-CN nanohybrids by combining silver nanoparticles, graphene oxide and carbon nitride (g-CN) in the present study has emerged as a much sensitive one to detect methylene blue (MB) and Hg2+ ions. Its multiple charge transfer from 2D sheets to AgNPs and then to MB is verified beyond the doubts with analytical techniques and it is the cause for an enhanced SERS intensity. A very low concentration of 10−12 M with enhancement factor of 4.25 × 108, 6.15 × 108, 6.11 × 108 and 6.59 × 108 for the peaks at 450, 502, 1400 and 1624 cm−1, respectively for MB could be detected by this SERS substrate. The ideas implemented in this study could also be applicable to other 2D sheets and metal nanoparticles. The essential criterion is the 2D sheets should have delocalized electronic cloud and capable of bonding to each other and facilitate immobilizing metal nanoparticles on their surface. The analyte MB bonding to the metal nanoparticles of the SERS substrate could be used as a and Raman tag to study selective SERS sensing of Hg2+ ions at very low concentration of 0.01986 ppm. Thus the present SERS substrate is expected to be a promising candidate for the determination of waste water contaminants.