52 / 2021-05-31 10:38:13

Green synthesis of nanocellulose based-Cu2O/Ag heterostructure with surface-enhanced Raman scattering performance

Surface-enhanced Raman scattering, cuprous oxide/silver heterostructure, cellulose nanofibrils, methylene blue

Semiconductor metal-oxide/metal heterostructures with plasmonic resonance property are believed to be a reliable substitute for noble-metal surface enhanced Raman scattering (SERS) detection substrate because of their higher sensitivity and lower cost. Here, we demonstrated an ecofriendly and easily-controlled route to synthesize cuprous-oxide/silver (Cu₂O/Ag) heterostructure for sensitive SERS detection of organic dyes by using TEMPO-oxidized cellulose nanofibrils (CNFs) as sole reducing and stabilizing agents. The results showed that Cu₂O cubes were synthesized under mild aqueous conditions, and covered by spherical-like Ag nanoparticles (AgNPs) through substitution reaction. With methylene blue (MB) as a probe, the Cu₂O/Ag heterostructure within the CNF network showed better Raman scattering sensitivity than pure CNF-Cu₂O hybrids at 633 nm laser excitation. When the surface of the Cu₂O cubes was fully covered by AgNPs, the substrate showed the highest SERS activity and reproducibility. The enhancement index was up to 4.0×10⁴ and the substrate was capable of detecting MB dyes down to sub part-per million level. The green synthesized CNF-based Cu₂O/Ag heterostructure substrate with improved SERS activity and low fluorescence has great potential in food safety testing, water monitoring and other portable Raman detection devices.