Super-hydrophilic SERS sensor with both ultrahigh activity and exceptional 3D spatial uniformity for sensitive detection of toxic pollutants

• Construction of super-hydrophilic SERS sensor with multiplex distinctive merits. • Dense Au NPs decorated on 2D h-BN then the hybrids are grafted into 3D porous BNCs. • Ultrahigh SERS activity with detection limit of analyte at 0.1 femtomole level. • Exceptional 3D spatial SERS uniformity in horizontal and vertical directions. • Superior wettability leads to ultrarapid and uniform diffusion of liquid analytes. The powerful surface-enhanced Raman scattering spectroscopy (SERS) practical technique is not only related to signal enhancement but also heavily dependent on spatial uniformity. Different from the routine hydrophobic substrates, an extraordinary super-hydrophilic SERS sensor is established by loading plasmonic Au nanoparticles (NPs) on two-dimensional (2D) hexagonal boron nitride (h-BN) then the hybrids uniformly are grafted into 3D bacterial nanocelluloses (BNCs). The Au NPs@h-BN/BNCs exhibit a remarkably high SERS activity with a limit of detection (LOD) of dyes at 0.1 femtomole (fM) level (∼10 -16 M). It is attributed to the strong synergistic coupling effect between highly dense Au NPs and modified h-BN as well as multiple light-scattering effects in 3D porous supports. More importantly, the distinctive advantage is further highlighted by the exceptional 3D spatial SERS uniformity with relative standard deviation (RSD) less than 3.4% along both horizontal and vertical directions. The unique feature is due to the 3D homogeneous distribution of the injected colloidal analytes via ultra-rapid liquid diffusion throughout the entire body with superior wettability. Besides, the flexible SERS substrates with excellent easy-tailorable mechanical properties can be robust enough to withstand the portable operations in real-world scenarios. These competitive merits are particularly beneficial for reliable SERS quantitative surveillance.