A high-performance 2D-3D SERS substrate with facile through-hole nanoporous anodic alumina membrane for malachite green and salicylic acid detection

• Traditionally detecting antibiotics by SERS with metal nanoparticles (MNPs), core-shell or multilayer structure. • A unique through-hole 2D-3D nanostructured AAO membrane as MNP-free SERS substrate is proposed with three kinds of electric enhancement mechanism. • Such 2D-3D nanoporous membrane is prepared by a rapid high-efficient voltage detachment method. • A low LOD of 1×10 −10 M for MG was achieved, with an R² of 0.93–0.98 and RSD of 8.14–8.33%. • Detecting salicylic acid concentrations as low as 0.01 ppm, far below 10 −3 M proposed by other group. Surface-enhanced Raman scattering (SERS) is an effective optical detection method for tracing amounts of toxic substances, with applications in drug detection, environmental and food safety. In the SERS measurements of malachite green (MG) and salicylic acid (SA), metal nanoparticles (MNPs) or core-shell nanostructures are commonly used. However, the preparation of these nanostructures typically requires at least 12 h. Compared to these complex and time-consuming fabrication methods, porous AAO templates offer a facile and stable SERS measurement substrate. We develop a rapid and efficient through-hole AAO fabrication method for SERS detection of MG and SA. The 2D-3D structures at the bottom of these membranes provide more hotspots from sharp tips and concaves, effectively enhancing the SERS signal intensity and improving limits of detection (LOD). For MG detection, the LOD of 10 −10 M and analytical enhancement factor (AEF) of 2.67☓10 5 was achieved, with bottom surface of the membrane providing 2-5 times higher signal intensity compared to top surface. Among different AAO nanostructures, AAO prepared at 40 V showed a 1.2-2 times signal enhancement compared to 100/-4 V, attributed to the smaller interpore distance, which effectively enhances the local electrical field on the AAO substrate. The COMSOL simulation of the electric field enhancement by 2D-3D nanostructures is also performed. The calculated relative standard deviations (RSD) within 5 points are 8.23% and 8.14%, indicating that the 2D-3D through-hole membrane structure exhibits excellent uniformity. By applying AAO membranes to SA and real sample detection, the LOD of 1 ppm is achieved. This detection method can help in detecting MG and SA in fields like aquaculture, food safety, and daily items. In the SERS measurements of malachite green (MG) and salicylic acid (SA), metal nanoparticles (MNPs) or core-shell nanostructures are commonly used. Compared to these complex and time-consuming fabrication methods, porous AAO templates offer a facile and stable SERS measurement substrate. We develop a rapid and efficient through-hole AAO fabrication method for SERS detection of MG and SA. The 2D-3D structures at the bottom of these membranes provide more hotspots from sharp tips and concaves, effectively enhancing the SERS signal intensity and improving limits of detection (LOD). For MG detection, the LOD of 10 −10 M and analytical enhancement factor (AEF) of 2.67☓10 5 was achieved, with bottom surface of the membrane providing 2-5 times higher signal intensity compared to top surface. Among different AAO nanostructures, AAO prepared at 40 V showed a 1.2-2 times signal enhancement compared to 100/-4 V, attributed to the smaller interpore distance, which effectively enhances the local electrical field on the AAO substrate. By applying AAO membranes to SA detection, the LOD of 10 ppb is achieved. This detection method can help in detecting MG and SA in fields like aquaculture, food safety, and daily items.