ZnS nanocrystallites as fluorescent probe for selective detection of bilirubin

Abstract

Selective determination of bilirubin is much essential to identify neonatal hyperbilirubinemia. Herein, we present a simple and precise method for quantitative measuring of bilirubin levels using polyvinylpyrrolidone (PVP) capped ZnS nanocrystallites (ZSP). The crystalline structure and purity are studied from x-ray diffraction (XRD) patterns and the transmission electron microscope (TEM) images. The optical characteristics are analyzed using UV-visible absorption and photoluminescence spectra. For ZSP, the estimated value for the optical band gap is 4.06 eV, surpassing the band gap value of uncapped ZnS (3.89 eV). Upon 265 nm excitation, ZSP nanocrystallites exhibits blue emission peaked at 371 nm wavelength. The fluorescence intensity shows a consistent reduction as the bilirubin concentration rises from 3.0 μM to 80 μM. The spectral overlap between the emission spectrum of ZSP and the absorption spectrum of bilirubin, results in fluorescence attenuation due to the inner filter effect (IFE). The ZnS nanocrystallites exhibit remarkable fluorescence properties and demonstrate high sensitivity in detecting bilirubin, achieving a limit of detection (L.O.D) as low as 56 nM. The selectivity of bilirubin over certain co-existing biomolecules is also analyzed. The utility of the fluorescence probe for practical use is confirmed in spiked human serum and urine samples.