Large-Area Hexagonal Boron Nitride for Surface Enhanced Raman Spectroscopy

Application of atomically thin layers of hexagonal boron nitride (hBN) for passivating gold and silver nanoparticles is investigated and its potential use is demonstrated through surface-enhanced Raman spectroscopy (SERS). Silver nanoparticles readily oxidize in air, resulting in a significant decrease in its SERS activity. hBN is a novel 2D material, well-known for its thermal and chemical stability. In this study, wafer-scale hBN is grown using metal organic vapor phase epitaxy (MOVPE) and centimeter-sized hBN layers are transferred on to silver nanoparticles. hBN acts as an impermeable barrier and protects silver nanoparticles from oxidation, even at elevated temperatures and help retain its SERS activity. Thermal stability of hBN coated Ag nanoparticles is studied in detail. Furthermore, wafer-scale hBN layers grown using MOVPE are especially attractive, compared to mechanically exfoliated, micrometer sized flakes from bulk crystals, as it can be easily scaled-up, shown here through design and fabrication of a SERS chip, conducive for droplet-based analysis. Overall, large-area hBN layers are well suited for practical applications and can help improve the shelf-life and reusability of commercially available SERS substrates.