Simple Detection of Di-Butyl Phthalate in Aqueous Samples Using UV–Visible Spectroscopy Based on Functionalized Gold Nanoparticles

Phthalates are extensively used in water bottles and children’s toys. Therefore, detecting phthalates and their common derivatives in different samples is crucial. Gold nanoparticles had unique photophysical and photochemical properties due to their surface plasmon resonance. Here, we present a facile plasmonic sensor based on surface-modified gold nanoparticles of different shapes, spherical and rods, and these gold nanoparticles are surface functionalized using PEG-COOH and PEG-NH₂ ligands. Gold nanoparticles that detect di-butyl phthalate (DPB) concentrations start from 3 × 10⁻¹² to 3 × 10⁻⁵ mol/L in aqueous samples. Adding DPB to functionalized gold nanorods causes an instant shift in the longitudinal surface resonance from 655 to 690 nm. They also show a detection concentration limit of up to 3 × 10⁻¹² mol/L. A higher sensitivity of gold nanorods was noticed compared to the spherical nanoparticles, and the results show absorbance (Δ Abs = 0.57 ± 0 and 0.54 ± 0.007) and good linearity with correlation coefficient values (0.994 and 0.991) using gold nanorods functionalized by PEG-NH₂ and PEG-COOH, respectively, upon adding different concentrations of DBP in aqueous samples. The presented plasmonic sensor offers a rapid, sensitive, low-cost, and simple detection method of DBP in laboratory aqueous samples.