Quantitative understanding of the ultra-sensitive and selective detection of dopamine using a graphene oxide/WS2 quantum dot hybrid

Abstract

Herein, we have reported the ultra-high sensitive and selective detection of dopamine (DA) at the pico-molar level using a low cost sensing platform based on graphene oxide (GO) sheets anchored with tungsten disulfide quantum dots (WS₂ QDs). The liquid phase exfoliated WS₂ QDs are mostly bilayered with an average particle size of ∼2.0 ± 0.3 nm, while the GO sheets are of few-layer thickness. The WS₂ QDs are highly luminescent with a photoluminescence (PL) quantum yield of ∼15%, and they exhibit an excitation wavelength dependent spectral shift in PL due to the high degree of edge/defect states. In the presence of GO, the PL intensity of WS₂ QDs is partially quenched due to van der Waals interaction and excited-state charge transfer from WS₂ to GO. However, in the presence of DA, a drastic quenching of PL occurs for the WS₂/GO hybrid and this enables the selective detection of DA as low as 10 pM, which is the lowest among the reported values. We have presented a new model to quantitatively explain the GO mediated efficient charge transfer and unusual quenching of PL as a function of the DA concentration. Finally, the WS₂/GO based sensor is utilized for the detection of DA in river water and blood serum with a satisfactory recovery, which establishes its practical utility as an efficient environmental/biochemical sensor.