Paper-based sensing of cinnamic ortho-diphenols in food samples using photoluminescent laser-induced aluminum nanostructures

A versatile CO₂ laser plotter-based strategy is proposed to obtain optically active aluminum/paper nanostructures for the selective colorimetric sensing of cinnamic ortho-diphenolic compounds (o-PCs). The Laser synthesis generated Al nanostructures (L-Al) that were characterized, demonstrating photoluminescent properties. A L-Al Photoluminescent Paper-based Platform (L-Al_3xP) with an ELISA plate like format, manufactured via accessible benchtop technologies, was conceived to work with a smartphone-readout. The L-Al_3xP sensing relies on chelation-enhanced fluorescence turn-on, driven by the interaction between L-Al sensing spots and o-PCs, which results in a green brightness increase. The L-Al_3xP sensing mechanism and class-selectivity were investigated towards 23 phenolic compounds of different chemical classes; the analytical figures of merits were extrapolated for caffeic, rosmarinic, and chlorogenic acids, highlighting linear dose-response (R² ≥ 0.990) and LODs≤3.0 μM. The L-Al_3xP was challenged for o-PCs determination in 15 different food samples, returning reproducible outputs (RSD ≤ 11.1 %, n = 3) well correlated with HPLC-MS/MS (r = 0.993).