Sensitive Colorimetric Determination of Cyromazine Using a Gold Nanoparticle (Au NP) Based Sensor with Smartphone Detection

A highly sensitive colorimetric sensor based on the aggregation of gold nanoparticles (Au NPs) and a smartphone camera as detector is reported for the determination of cyromazine. In the presence of cyromazine, a decrease in the characteristic SPR absorbance peak of Au NPs is observed at 520 nm. A color change in the solution of Au NPs was observed from burgundy to purple and then to blue gray with a red shift of the absorbance peak from 520 to 666 nm with increasing cyromazine concentration. The reaction parameters were investigated to optimize the sensitivity. The best conditions for cyromazine were 0.125 mM of Au NPs, pH 4.0, 25 degrees C, reaction time of 7 min, and 0.5 mM of sodium bisulfate. The absorbance ratio at 666 nm and 520 nm (A(666)/A(520)) as a function of the concentration of cyromazine provided a linear relationship from 0.3 to 0.7 mu M. The visible color changes were captured with a smartphone camera. The digital images were analyzed by the WeChat applet for color recognition extraction for red-green-blue conversion. The limits of detection were 0.3 mu M with the naked eye and 8.13 nM with a spectrophotometer. These values are lower than those in the literature. The method provides a simple, time-saving, and portable strategy for the determination of cyromazine.

Automated summary

A highly sensitive colorimetric sensor based on the aggregation of gold nanoparticles (Au NPs) and a smartphone camera as detector is developed for the determination of cyromazine. By optimizing the reaction parameters, a linear relationship between the absorbance ratio at 666 nm and 520 nm and the cyromazine concentration is established. The method provides a simple and portable strategy for the determination of cyromazine with lower detection limits compared to previous studies.