Highly uniform and ultra-sensitive graphene hybrid SERS substrates fabricated by colloidal lithography

Surface-enhanced Raman spectroscopy (SERS), empowered by the rapid development of advanced micro/nanostructured substrates, has shown increasing promise in diverse applications. Graphene-Au nanopyramid (GAuNP) substrate is a promising SERS platform with high sensitivity, and can be fabricated through low-cost colloidal lithography. However, the fabrication processes remain underexplored and limit investigations into nanopyramid arrays with diverse dimensions. Here, three types of highly uniform and ultra-sensitive GAuNP SERS substrates with diverse dimensions were fabricated through advanced colloidal lithography technology. A novel Langmuir-Blodgett method and a poly (methyl methacrylate)/paraffin bilayer-enabled method were introduced to fabricate two-dimensional polystyrene colloidal crystals and achieve large-area, clean graphene transfer. Optimal micro/nanofabrication methods and parameters were comprehensively identified. Relative standard deviations of 3.3 % for nanopyramid size and 9.1 % for spectral intensity demonstrate excellent structural and spectral uniformity. Theoretical simulations and experimental results demonstrated the ultra-sensitivity, achieving a maximum analytical enhancement factor of 1.6 × 10¹⁰. Graphene contributes a 19-fold chemical enhancement effect and improves quantitative analysis capabilities. Machine learning enabled the classification of various substances with exceptional performance, achieving 100 % sensitivity, over 96.3 % specificity, and over 97.4 % accuracy. This method demonstrates significant potential for diverse applications, such as cytological diagnosis and chemical detection.