Surfactant-Free Synthesis of Hexapod Cu₂O@Au Nanocrystals and Their Enhanced Performances in Biosensor and Photo-Catalysis

A low-cost biosensor with multifunctionality, wide detection range, and enhanced sensitivity was highly desirable. In this work, we demonstrated the desirable application of Cu2O@Au in nitrite, glucose, and formaldehyde detection. The surfactant-free synthesis of Cu2O@Au nanocrystals with a hexapod morphology and controllable Au loading rates has been achieved. The surfactant-free surface maximized the active sites and the decoration by Au accelerated electron transfer, resulting in an enhanced biosensor performance. The correlation between the atomic rate and biosensor performance for obtained Cu2O@Au nanocrystals has been investigated systematically. It is indicated that an optimal Au loading rate would not only enhance the sensitivity but also rationalize the sensor cost. In the detection of nitrite, the sensitivity of the sensor constructed by Cu2O@Au-20% was <inline-formula> <tex-math notation="LaTeX">$368.77 ~\mu \text{A}$ </tex-math></inline-formula>/mM <inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm2, which exhibited 6.8 folds higher than that by pure Cu2O. The superior biosensor sensitivity of Cu2O@Au could also be extended to the glucose and formaldehyde detection, the enhanced factors could reach 1.26 and 1.88, respectively. Meanwhile, the surface decoration by Au elevated enabled Cu2O an effective photocatalyst. This work optimized the performances of Cu2O by a green approach, which opened up new avenues for designing a nontoxic biosensor with multifunctionality and enhanced performance.