Protein protected gold nanoparticles as a fluorophore for the highly selective and ultrasensitive determination of bisphenol A in plastic samples

Abstract

We wish to report a highly selective and ultrasensitive chemosensor for bisphenol A in plastic samples using bovine serum albumin capped gold nanoparticles (BSA–AuNPs) as the fluorophore. The BSA–AuNPs were synthesized by a wet chemical method and were characterized by UV-visible, fluorescence, high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction techniques. The BSA–AuNPs show the absorption maximum at 523 nm and the emission maximum at 765 nm (λ_ex: 523 nm). Interestingly, after the addition of 10 μM bisphenol A, the wine red color of BSA–AuNPs was changed to purple and the surface plasmon resonance (SPR) band at 523 nm was red shifted with decreased absorbance. The observed spectral and color changes were ascribed to the aggregation of AuNPs and this was confirmed by HR-TEM. However, no spectral changes were observed for BSA–AuNPs in the presence of nanomolar range concentrations. Interestingly, the emission intensity was enhanced at 765 nm for the addition of 10 pM bisphenol A. Based on the enhancement of emission intensity, the concentration of bisphenol A was determined. The present fluorophore showed preferential selectivity towards the determination of 1 nM bisphenol A in the presence of 1000-fold higher concentration of common interferences. A good linearity was observed from 1 × 10⁻⁹ to 100 × 10⁻¹² M bisphenol A and the detection limit was found to be 2.3 fM L⁻¹ (S/N = 3). The proposed method was successfully utilized to determine bisphenol A in a PVC drinking cup, baby's dummy and food packaging, tap water and river water samples. The obtained results were validated by HPLC.