Colorimetric Detection of Hydrogen Peroxide and Glucose Based on Gold-Silver Core-Shell Nanoparticles

Carbon dots (CDs) were synthesized through a one-step microwave-assisted treatment by using donkey-hide gelatin as carbon source. Gold nanoparticles (AuNPs) were subsequently prepared via the reduction of HAuCl4 by the as-prepared CDs, which served as a green reducing agent. Based on the reducing property of dopamine (DA), gold-silver core-shell nanoparticles (AuNPs@AgNPs) were synthesized by in situ growth of silver shell on the surface of AuNPs under alkaline conditions by a seed-growth method. The resulting AuNPs@AgNPs were successfully employed to construct a colorimetric sensing platform for detection of H2O2 and glucose. H2O2 could directly oxidize and etch gradually the silver shell of AuNPs@AgNPs, leading to a decrease in the surface plasmon resonance absorbance at 410 nm monitored by ultraviolet visible (UV-vis) detection, which was accompanied by a color change. The important experimental parameters influencing detection of H2O2 were investigated in detail, including the concentrations of AgNO3, NaOH, DA and so on. The sensor exhibited two linear response ranges for H2O2 from 0.5 to 80 μmol/L and from 80 to 180 μmol/L, with a limit of detection (LOD) of 0.26 μmol/L. H2O2 could be produced from glucose under the catalysis of glucose oxidase, therefore the sensor was also available to detect glucose, with a linear range of 2–120 and 160–1000 μmol/L and a LOD of 0.60 μmol/L. The sensor was successfully employed for glucose determination in human urine samples, yielding recoveries in the range of 94.0%–106.8%. Furthermore, the colorimetric sensing system was immobilized in agarose gels to fabricate test strips, enabling qualitative glucose analysis by the naked eye.