In this study, graphene oxide (GO) and a carbon 2D materials (g-C₃N₄ nanosheets) were combined to construct g-C₃N₄/GO nanosheets through π-π stacking interaction. Moreover, Ag⁺ ions were reduced to Ag nanoparticles and further grafted onto the g-C₃N₄/GO nanosheets (Ag@g-C₃N₄/GO) to impart the dual functionality of photocatalytic degradation and surface enhanced Raman scattering (SERS) detection. The Ag@g-C₃N₄/GO SERS substrate can be used to detect biomolecules (adenine) and organic pollutants (methylene blue). The X-ray diffraction, scanning electron microscopy, and Raman spectroscopy observations confirmed that g-C₃N₄ was successfully stacked onto the GO nanosheets. In addition, the Ag@g-C₃N₄/GO SERS substrate displayed photocatalytic ability. Pollutants in water were photodegraded by irradiation with visible light (405 nm), making the substrate self-cleaning and reusable. Thus, the Ag@g-C₃N₄/GO SERS nanosheets has potential for application in the photocatalytic degradation of water pollutants and detection of biomolecules.