Small Au nanoparticles to be modified with decavanadate for sensitive and stable SERS detection

Surface enhanced Raman spectroscopy (SERS) has been a powerful vibrational optical spectroscopic technique for trace determination. And the application and promotion of SERS technology are closely related to plasmonic substrates. To combine the distinct electronic properties of polyoxovanadates with the plasmonic properties of Au NPs, the small cit-Au NPs (reduced by sodium citrate) was modified with decavanadate (V 10 ) via ligand displacement. The structure of V 10 was controlled by pH adjustment. X-ray photoelectron spectroscopy (XPS) and SERS were introduced for studying interactions of V 10 with the surface of Au NPs. Compared with cit-Au NPs, V 10 -Au NPs owned higher absolute value of zeta potential and presented greater stability in CH 3 OH/H 2 O (V/V = 1:10) solvent environment. Even after 60 min of soaking, the V 10 -Au NPs still exhibited a typical coffee ring effect during the evaporation process with SERS enhancement. The stability of V 10 -Au NPs (in a solution with pH 4.8) was tested over a period of 5 days to indicate their ability to maintain SERS activity. Moreover, the V 10 -Au NPs also showed great sensitivity for cationic dye molecules and antibiotics, and the detection levels could be as low as μg⋅L −1 . This study lays the foundation for the screening low-concentration cations in mixed solutions and monitoring the morphological changes of polyoxometalates during their application via SERS technology.