Angle-Dependent Dip Coating Strategy for Silver Nanostructured Surface Fabrication with Enhanced Fluorescence and Surface-Enhanced Raman Scattering Properties.

Noble metal nanostructures based on localized surface plasmon resonance (LSPR) can induce metal-enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS), significantly improving trace detection sensitivity for biomedical and chemical analysis. While self-assembly of noble metal nanoparticles offers simplicity and low equipment dependence, achieving large-area, uniform, and controllable nanostructures remains challenging. In this study, angle-dependent dip coating (ADDC) technology was employed to achieve efficient, controllable self-assembly of silver nanoparticles (AgNPs) on glass slides, establishing a fabrication process for MEF/SERS dual-functional substrates. A stable AgNPs-anhydrous ethanol suspension was prepared and extracted from an inclined substrate reservoir using a microfluidic syringe pump, enabling large-area uniform nanostructure assembly. Systematic investigation revealed that substrate inclination angle provides better morphology and fluorescence enhancement control than withdrawal flow rate. The silver nanostructured surface fabricated under a withdrawal flow rate of 16 mL/h and a substrate inclination angle of 30° exhibited a Cy3 detection limit as low as 10-1 nM, with an enhancement factor ranging from 19.14 to 28.66, as well as an R6G SERS detection limit of 10-10 M with an enhancement factor of 4.07 × 108. This study confirms that ADDC technology enables simple, efficient, large-area uniform AgNPs self-assembly for superior dual-function enhancement substrates, offering a cost-effective and efficient strategy for highly sensitive trace detection.