A sensitive turn off-on spectrofluorimetric probe for picric acid based on the resonance fluorescence energy transfer between rhodamine B and gold nanoparticles

A fluorescence resonance energy transfer (FRET) probe was described for the simple, and sensitive determination of trace quantities of picric acid (PA) based on its restoring effect on quenched fluorescence of rhodamine B (RB) by amine capped-gold nanoparticles (AuNPs). AuNPs act as the energy acceptors and diminish the fluorescence emission of RB via FRET mechanism, due to the electrostatic attaching of RB on their surface [1]. Furthermore, it is observed that PA has a restoring effect on this quenched fluorescence, maybe because of its interaction with amine groups on the surface of AuNPs [2] and so, detaching of RB molecules. The increase in fluorescence emission was linear increased with PA concentration that formed the basis of a turn off-on sensor for the determination of PA. The effect of some important factors (for example pH, buffer, RB concentration etc.) were optimized to obtain maximum sensitivity. The calibration graph was plotted which is linear in the concentration range of 0.9-80 nmol L-1, with a detection limit (3s) of 0.23 nmol L-1. The developed method has good precision and was satisfactorily applied to the determination of PA in environmental samples.