Highly sensitive and selective detection of free bilirubin using blue emitting graphene quantum dots (GQDs)

Graphene quantum dots (GQDs), a zero-dimensional material, are emerging as a potential fluorescent probe with a wide range of applications, particularly bio-imaging and optical sensing. In this work, we have fabricated the blue-emitting Graphene Quantum Dots (GQDs) and utilized as for free bilirubin (BR) detection. Under optimal conditions, the fluorescence of GQDs was quenched linearly with the successive addition of BR concentrations. The probe exhibited a wide linear range (40.53-237.55 μM), low detection limit (9 μM), high selectivity, and rapid response towards free BR. The drastic quenching in the fluorescence intensity of GQDs with the addition of BR is due to Förster Resonance Energy Transfer (FRET) between GQDs and bilirubin. The efficiency of energy transfer between GQD and BR was determined as 43%. Therefore, this free BR sensing platform using GQDs may prove useful in the diagnosis of jaundice. Our study opens up the possibility of designing a low-cost biosensor that will be suitable for a real sample study.

Graphical abstract

Our study presents the fabrication of blue-emitting Graphene Quantum Dots (GQDs) and employs them as an assay to detect free bilirubin (BR). Fluorescence of GQDs was quenched linearly as BR concentrations increased from 40.53 to 237.55 μM and exhibited a low detection limit (9 μM) with high selectivity and rapid response towards free BR. The efficiency of energy transfer between GQD and BR was determined as 43%. Fluorescence spectra show a broad emission spectrum with a maximum fluorescence intensity at around 420 nm (λ_max) when excited at a wavelength of 320 nm. This 100 nm wavelength stokes shift is advantaged for employing GQDs for sensing applications.