Wide color-varying visualization of sulfide with a dual emissive ratiometric fluorescence assay using carbon dots and gold nanoclusters

Abstract

Development of visual detection methods regarding water pollutants can effectively facilitate water resource monitoring programs. A wide color-varying ratiometric approach has been developed for sensitive determination of sulfide by mixing orange emissive glutathione stabilized gold nanoclusters (AuNCs) and blue emissive urea stabilized carbon dots (CDs) in an appropriate ratio. Under a single excitation wavelength of 365 nm, the ratiometric fluorescence (RF) probe exhibited two distinct emission bands at 452 and 607 nm corresponding to CDs and AuNCs, respectively. Owing to the high affinity of sulfide ions to AuNCs in alkaline medium, the fluorescence (FL) of AuNCs was turned-off while the emission of CDs remained unchanged, resulting in a distinguishable FL color change from pink to blue under an ultra-violet (UV) lamp. The I452/I607 ratio was linearly dependent to sulfide concentration in the range of 1.0 to 50.0 µM with a limit of detection (LOD) of 0.35 µM and a visual LOD as low as 4.0 µM that is less than the maximum allowable sulfide amount (10.0 µM) in drinking water. The RF probe was successfully applied for further determination of sulfide in river water and acceptable recoveries were obtained. We believe that the simplicity together with the great visual capability of this visual RF probe can improve and facilitate on-site sulfide determination.