Hollow molecularly imprinted microspheres made by w/o/w double Pickering emulsion polymerization stabilized by graphene oxide quantum dots targeted for determination of l-cysteine concentration

A double Pickering emulsion was designed to fabricate hollow imprinted microspheres (H-IMMs) for the detection of l-Cysteine (l-Cys). In a w1/o/w2 double emulsion, the main o/w2 emulsion droplets stabilized by hydrophilic partially reduced graphene oxides (r-GOs) encapsulating smaller w1/o emulsion droplets stabilized by hydrophobic reduced graphene oxide quantum dots (r-GOQDs). The results revealed that size distribution and calculated volume-surface mean diameter (d3,2) of main droplets were narrowed and decreased from 48.2 to 16.7 μm with pH variation from 4 to 12 ; the reason lies in the pH-sensitivity of r-GOs. Polymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of l-Cys, as a target molecule, at the oil phase led to the synthesize of H-IMMs. Investigations by cyclic voltammetry and differential pulse voltammetry methods demonstrated that the prepared H-IMMs is responsive to l-Cys. The response of H-IMMs leach/CPE displayed a linearity range of 0.01 μM to 1 μM Cys with a limit of detection of 15.5 nM.