One of the main concerns about the rapid development of modern industrialization worldwide is the increased environmental contaminants, including several harmful molecular and ionic species (e.g., gases, pesticides, heavy metals, and pharmaceutics). It is crucial the development of new and low-cost materials for the efficient and rapid optical detection of the lower amounts of these environmental contaminants in real water samples.

Two-dimensional (2D) materials, such as graphene and derived materials (e.g. graphene oxide: GO), have attracted significant attention due to their unique optical properties, well-defined architecture and tunable surface chemistry, making them excellent platforms for optical sensing applications. Combining such 2D materials with metallic nanoparticles (MNPs) allows the fabrication of highly sensitive surface-enhanced Raman scattering (SERS) substrates for analytical purposes.

Here, we report our research on chemical strategies to decorate GO membranes with Au nanostars (AuNSs) to produce easy-handled and highly sensitive analytical platforms, envisaging the spectroscopic detection of vestigial organic pollutants dissolved in contaminated water. The organic dye methylene blue (MB) was used here as a water pollutant model because it is a cationic dye widely used for dying textiles and wood. MB produces potentially carcinogenic aromatic amines such as benzidine and methylene and is well-known for its high SERS activity. Several preparative approaches were employed to fabricate these hybrid materials, and their impact on MB SERS detection was evaluated. These include using polyelectrolytes, distinct graphene-based materials, and the deposition method of the AuNSs.