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The aqueous suspension of fluorescent pyrene nanoparticles (PyNPs) have been prepared by a reprecipitation method in the presence of sodium dodecyl sulphate (SDS) as a stabilizer. The PyNPs shows bathochromically shifted aggregation induced enhanced emission in the spectral region 400 nm to 600 nm peaking at 466 nm where Riboflavin (RF) absorbs strongly. The systematic fluorescence resonance energy transfer (FRET) experiments performed by measuring fluorescence quenching of PyNPs with successive addition of RF analyte has exploited the use of PyNPs as nano probe for detection of RF in aqueous solution with lower limit of detection 10.163 x 10-5 mol.L-1. The fluorescence of PyNPs is quenched by RF and quenching is in accordance with the Stern-Volmer relation. The distance r between the donor (PyNPs) and acceptor (RF) molecules has been obtained according to the FRET method. The evaluation of photo kinetic and thermodynamic parameters such as quenching rate constant (kq), enthalpy change (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS) are calculated by quenching results obtained at different constant temperatures. The proposed FRET method based on fluorescence quenching of PyNPs is used further to develop an analytical relation for estimation of RF from pharmaceutical samples available commercially in the market. [ABSTRACT FROM AUTHOR]

Fluorescent pyrene nanoparticles (PyNPs) have been prepared by a reprecipitation method in the presence of sodium dodecyl sulphate (SDS) as a stabilizer. The formation of PyNPs has been confirmed by dynamic light scattering (DLS), UV-visible absorption spectroscopy, fluorescence spectroscopy and excited state lifetime measurements. DLS results of PyNPs shows a narrow size distribution with average particle size of 77.4 nm and negative zeta potential. The systematic FRET experiments performed by measuring fluorescence quenching of PyNPs with successive addition of FL-Na analyte exploited the use of PyNPs as nanoprobe for detection of FL-Na in aqueous solution. The fluorescence of PyNPs has been quenched by Fl-Na and quenching has been in accordance with the Stern-Volmer relation. The distance r between the donor (PyNPs) and acceptor (FL-Na) molecules has been obtained according to the fluorescence resonance energy transfer. The fluorescence quenching results have been used further to develop an analytical method for estimation of fluorescein sodium from ophthalmic samples available commercially in the market. [ABSTRACT FROM AUTHOR]