Development of a gold nanomaterial enabled colorimetric sensor method for the analysis of sodium chloride in seawater

Abstract

In this study, a simple and practical gold nanoparticle enabled colorimetric sensor technique was developed for the detection of sodium chloride. The synthesis of gold nanoparticles was based on the chemical reduction of gold (III) chloride trihydrate using tri-sodium citrate that also served as a capping agent thus, protecting the particles against aggregation. UV–vis spectra and transmission electron microscopy were used to characterise the synthesized citrate capped gold nanoparticles. The colorimetric response of sodium chloride was performed by the gold nanoparticle sensor, based on the property of localized surface plasmon resonance. The interaction between sodium ions, chloride and tri-sodium citrate causes rapid aggregation of the gold nanoparticles conjugates, resulting in color conversion from wine red to blue which is clearly visible by the naked eye. Thereby, we propose the use of gold nanoparticles as colorimetric sensors, as they cause a color change when interacting with sodium chloride which is recognized easily by naked eye with high selectivity. The detection limit of the sensor calculated by the linear relationship of localised surface plasmon resonance for sodium chloride was found to be 1.18 parts per thousand and the lowest quantified amount was 3.57 parts per thousand, making the developed sensor to be highly sensitive. The practical applicability of the gold nanoparticles was also verified by the detection of sodium chloride in estuary and seawater samples.