Fabrication Of G-C₃N₄/Ag Nanostructures And Study Of Their SERS Performance

Surface-enhanced Raman Spectroscopy（SERS）technology attracts much attention since it provides a powerful tool for ultrasensitive vibrational spectroscopy,which was shining brightly in many frontier fields,including analytical chemistry,food security,life science and bio-sensing.The efficient coupling of Plasmon-induced near field with vibrational modes of specific molecules on the SERS-active substrates can enhance the Raman cross-section of the analytes by 10⁴-10¹⁴.When the target molecules are adsorbed on the proper position of metal nanostructures,especially Au and Ag,even single molecule detection can be realized.It has commonly assumed that plasma nanostructure SERS substrate can cause much greater SERS enhancement than most pure semiconductor SERS substrates,particularly original from the“hot spots”existed in the gaps among noble metal nanostructures.However,there are still some problems for metal substrates,such as that oxidation of metal nanoparticles leads to rapid decreasing of SERS-activity,the fabrication procedures of coating and lithography are expensive and complicated.Moreover,noble metal substrates suffer from an obvious shortcoming that analytes reside on the surface of which is difficult to reuse.Therefore,more research efforts have been focused on preparing recyclable SERS substrates,such as TiO₂/Au,ZnO/Ag and graphene/g-C₃N₄/Au,wittily utilizing their photocatalytic properties to relieve analytes.Apparently,most of the composite SERS substrate mentioned exhibit degradation activity in UV-light region,it must be a meaningful and interesting topic to explore solar-light available SERS substrate.Polymeric graphitic Carbon nitride（g-C₃N₄）is a novel two-dimensional semiconductor material consisting of tri-s-triazine units,with strong covalent C-N bonds in each layer and weak van der Waals force between layers.This material has received considerable attention owing to its splendid photoelectronic properties,extending applications in hydrogen production,pollutant-degradation,and reduction of CO₂.It is a widely held view that prolonged carrier lifetime and improved electron transport kinetics as a result of short diffusion path coupled to the quantum confinement effect make g-C₃N₄ brightening photocatatytic material.In addition,we believe the ability to adsorb and enrich target molecules throughπ-πinteraction further makes it a fascinating candidate for SERS application.Herein,we first reported g-C₃N₄/Ag nanocomposites with multifunctionality,of which modified g-C₃N₄ was synthesized by thermal treating pristine g-C₃N₄ at 550℃for 1-3 hours,and then decorated with AgNPs.As-synthesized hybrid nanostructures not only shown excellent SERS activity,but also exhibited degradation ability to RhB.After six detection/degradation cycles,g-C₃N₄/Ag still maintain strong SERS activity.