Nowadays,it is widely accepted metal nanoparticles (NP) affect thephotophysical and photochemical performance of molecules locatedclose or in contact with the metal surface in different ways. Eitherquenching or enhancement of their properties can be produced, andfactors affecting these phenomena are NP size, composition, shape aswell as distance of the molecule from the surface [1-2].Although, the mentioned properties variations are continuallyexplored to improve molecule sensing, reports on the effect ofnanoparticle concentration on the photophysical properties such asfluorescence are still scarce.

Onthe other hand, due to the environmental implications NP can have, inthe last years it has been an increased interest on developinganalytical methods oriented to the detection of NP. In this frame,our aim is toexplore the NP concentration dependance of the photophysicalproperties of molecular probes and supramolecular complexes as anstrategy to detect metal nanoparticles in mixtures.

Inthis work we selected Rhodamine B and 6G (RhB and Rh6G, respectively)as molecular probes and carbazol@cyclodextrins (CZL@CDs) as thesupramolecular systems; and colloidal AgNP (citrate, gallic acid orstabilized by a gemini surfactant) and AuNP (citrate stabilized) asthe tested NP. We evaluated the effect on the fluorescence of RhB,Rh6G and CZL@CDs of the presence of different NP at differentconcentrations with or without pH control. A comparison between allthe systems will be discussed.