Live diatoms facing Ag nanoparticles: surface enhanced Raman scattering of bulk cylindrotheca closterium pennate diatoms and of the single cells

Abstract

A comprehensive exploratory SERS experiment in conjunction with conventional Raman spectroscopy was conducted to investigate the interface between the silver nanoparticles (AgNPs) and the lightly silicified Cylindrotheca closterium diatoms in vivo both in the bulk cells culture and at the single cell level. The SERS chemisorption mechanism was found dependent on the NPs type and size as the SERS signal showed different signature for different NPs, the common SERS feature being the absence of the conventional Raman signal of carotenoids when microalgae are excited with the 532 nm line. SERS results suggest that the (pre)resonance Raman effect observed in bulk diatoms is no longer dominant in the case of SERS in bulk solution. Detection of polyunsaturated fatty acids was achieved together with specific SERS evidence of carotenoids and chlorophylls. The results are a prerequisite for the further exploration the diatoms fluctuant contribution to the SERS outcome of natural seawater.