Citrate-capped gold nanoparticles as a sensing probe for determination of cetyltrimethylammonium surfactant using FTIR spectroscopy and colorimetry

A novel, facile, and low-cost method was developed for determination of cetyltrimethylammonium (CTA + ) cationic surfactant in water samples using diffuse reflectance Fourier transform IR (FTIR) spectroscopy and colorimetry. Cetyltrimethylammonium bromide was chosen as a model compound to demonstrate the optimization of the method for determination of CTA + in water samples. The absorption peak at 3015.96 cm -1 (for CTA + ) was enhanced when gold nanoparticles were used as a chemical sensor in diffuse reflectance FTIR spectroscopy, and this absorption peak was used for determination of CTA + . Alternatively, the color change from wine red (525 nm) to blue (740 nm) and the redshift of the localized surface plasmon resonance band in the visible region were used as a sensing probe for determination of CTA + . A linear calibration curve for determination in water samples was obtained in the range from 10 to 100 ng mL -1 with a limit of detection of 3 ng mL -1 by diffuse reflectance FTIR spectroscopy and in the range from 20 to 400 ng mL -1 with a limit of detection of 7 ng mL -1 by colorimetry. The advantageous features of the methods are their simplicity, rapidity, and sensitivity for the determination of CTA + in water samples. Graphical abstract