Quenched fluorescence and enhanced resonant light scattering in molecular plasmonic assemblies

Isolated gold nanoparticles in liquid suspension can effectively quench the fluorescence of molecules that are nearby (< 10 nm), e.g. fluorophores attached to the particles via molecular linkers. Using fluorescence correlation spectroscopy, which analyses the fluorescence from individual objects in a small probe volume, we have been able to demonstrate unambiguously the quenching of ligated chromophores, and to identify spontaneously desorbed ligands that display fluorescence [1,2]. Enhancement of molecular spectroscopic responses may occur at 'hot spots' in aggregates of plasmonic nanoparticles. Moreover, such aggregates display an intense, and specific, resonant light scattering, which in itself provides a useful signal for optical detection at low concentrations in small volumes [3]. We are currently investigating the reversible aggregation of various functionalised gold nanoparticles, using microfluidic systems [4] as a platform for precise control of the aggregation as well as for the development of new (molecular plasmonic) biosensing schemes. Funding by ERANet-NanoSci (MOLIMEN) and ANR (JCJC 2010, COMONSENS) is gratefully acknowledged. [1] M. Loumaigne, R. Praho, D. Nutarelli, M. H. V Werts and A. Debarre, Phys. Chem. Chem. Phys. 12 (2010) 11004-11014 [2] J. R. G. Navarro, M. Plugge, M. Loumaigne, A. Sanchez-Gonzalez, B. Mennucci, A. Debarre, A. M. Brouwer, M. H. V Werts, Photochem. Photobiol. Sci. 9 (2010) 1042-1054 [3] J. R. G. Navarro and M. H. V Werts. Analyst 138 (2013) 583-592 [4] M. H. V. Werts, V. Raimbault, R. Texier-Picard, R. Poizat, O. Francais, L. Griscom and J. R. G. Navarro, Lab on a Chip 12 (2012) 808-820