Silver-Coated Cu₂O Nanoparticle Substrates for Surface Azide–Alkyne Cycloaddition

Heterogeneous copper nanoparticles (CuNPs) have emerged as a promising alternative to complete the Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) owing to better stability and biocompatibility and provide opportunities for surface functionalization of biomolecules. Herein, we fabricated Ag-coated cuprous oxide (Cu2O) NP slides to promote dual functions: the metal-enhanced fluorescence effect and external copper ion-free CuAAC reaction. The Cu2O NPs were in situ generated on a Ag-coated glass slide, thus accelerating the catalytic process of the surface cycloaddition reaction. Considering the catalytic activity of the Ag-coated Cu2O NP surface, the azide–alkyne cycloaddition was studied employing an azido-linked ganglioside GD3 glycan and a caged biotin; the latter surface enabled the detection of fluoride with a sensitivity of 0.82 μM that cannot be used on bare glass slides due to erosion by fluorine. Moreover, the immobilization of antibodies (Ab’s) using the BA-tosyl-oriented pathway was further introduced to this newly developed slide surfaces and showed better sensitivity compared to the random Ab immobilization method. The Ag-coated Cu2O NP surfaces developed herein represent a practical and alternative sensing platform for biological or diagnostic applications.