A novel sensor for determination of naproxen based on change in localized surface plasmon peak of functionalized gold...

A highly selective and sensitive colorimetric sensor for the determination of naproxen (NAP) based on the aggregation of the thiolated β-cyclodextrin (Tβ-CD) functionalized gold nanoparticles (Tβ-CD-Au NPs) in the presence of NAP and Zn²⁺is described. The hydrophobic end of NAP interacts with the immobilized Tβ-CD on the Au NPs and forms the complex of Tβ-CD:NAP while the Zn²⁺ ions form a 1:2 complex of (NAP)₂Zn with the carboxyl groups of NAP resulting in the aggregation of functionalized gold nanoparticles. As a result of aggregation, the localized surface plasmon resonance (LSPR) band of functionalized gold nanoparticles around 520nm decreases and a new red shifted band at 650nm appears which increases gradually as the function of NAP concentration. The calibration graph derived from the intensity ratios of absorbance at 650nm to 520nm was linear in the concentration range of 4-180μgL^-1of NAP. At the optimum conditions, the limit of detection (LOD) and quantification (LOQ) were found to be 0.6 and 2.1μgL^-1, respectively and the relative standard deviation at 20μgL^-1of NAP (n=5) was 2.5%. The selectivity and applicability of the method was verified through analyzes of the synthetic samples containing the major interference compounds reported in literature as well as tablets, wastewater and urine samples. The accuracy of the method was evaluated by recovery experiments and analysis of pharmaceutical tablets.