Surface-enhanced Raman scattering (SERS) allows for label-free detection of analyte molecules with high sensitivity, but it is still vastly challenged for the detection of ultra-highly diluted analyte solutions in practice, e.g., femtomolar concentrates, 10 −15 M. Here, we report a facile approach for the fabrication of hierarchical superhydrophobic melamine-formaldehyde/Ag (MF/Ag) nanocomposite array substrates, applicable for ultra-highly sensitive SERS detection of biological analytes at very low concentrations up to femtomolar levels. Hierarchical superhydrophobic MF/Ag nanocomposite arrays are synthesized by integrating colloidal lithography at the air-liquid interface and in-situ interfacial reactions. These substrates can confine analyte molecules within the localized sensing regions, so as to effectively prevent the random spread of analyte molecules. In this way, these substrates are able to detect dopamine with a detection limit of 10 -15 M, and with a SERS enhancement factor (EF) as high as 3.21 × 10 10 . The substrates are durable and the SERS results are reproducible. For practical demonstration, these superhydrophobic SERS-active substrates are also applied for detecting proteins, lysozyme and hemoglobin at low concentrates. This work presents a straightforward way to synthesize the hierarchical superhydrophobic SERS-active substrates with superior sensitivity and long-term reproducibility, with rational modification, which might merit the practical SERS applications in detection of drug and pollutants in extremely dilute environments.
- Ag nanoparticles
- Hierarchical surface
- Surface-enhanced Raman scattering