High-Volume Production of Repeatable High Enhancement SERS Substrates Using Solid-State Superionic Stamping

Abstract

Surface-enhanced Raman spectroscopy (SERS) is emerging as a powerful tool for detecting and identifying chemical and biological substances because of its high sensitivity, specificity, speed, and label-free detection. For SERS substrates to be effective in sensing applications, they must exhibit reproducible and robust high signal enhancement and cost-effective scalability. This article introduces a highly sensitive, large-area silver SERS substrate patterned with a uniform array of 3D retroreflecting inverted pyramids and develops a manufacturing pathway for it, using a novel and facile electrochemical imprinting process called solid-state superionic stamping (S4). Substrates, approximately 4 mm2 in area, are produced and tested with 1,2-bis(4-pyridyl) ethylene (BPE). Uniformly high and reproducible spatially averaged enhancement factor (EF), typically around a value of 2 × 107 with a relative standard deviation of 6.7% and a high batch-to-batch repeatability with a relative standard deviation of 10.5% between batches were observed. Passivating a substrate's surface with atomically thin layers of alumina, deposited using atomic layer deposition (ALD) was effective in maintaining the EF constant over a 60-day period, albeit with a trade-off between its EF and its lifespan. S4 has the potential to make substrates with EF consistently greater than 107 available at a cost of $1 to $2 per substrate, allowing SERS to be adopted across a wide spectrum of high-volume applications, including security, food safety, medical diagnostics, and chem-bio analysis.