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Abstract
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In this study, we developed sensitive and reproducible optical sensors for melamine detection based on localized
surface plasmon resonance (LSPR). Metal nanoparticle arrays were fabricated using colloidal lithography,
employing polymethyl methacrylate (PMMA) microspheres with diameters ranging from 114 to 1135 nm as
lithography masks. These 2D colloidal crystals were prepared via a Langmuir–Blodgett (LB) trough, coated with a
50 nm gold layer using magnetron sputtering, and processed to leave distinct gold nanoparticle (AuNP) arrangements. Functionalization of the LSPR chips involved immobilizing p-NA as a melamine receptor and
applying bovine serum albumin (BSA) as a blocking agent. Melamine detection was performed by monitoring the
LSPR peak wavelength shift using a UV–Vis spectrophotometer. Results showed that reducing microsphere
diameter improved detection limits from 5.88 to 0.63 ppm. Selectivity was validated with melamine detection in
infant formula samples, and Finite-Difference Time-Domain (FDTD) simulations corroborated the experimental
findings.
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