Visual colorimetric detection of berberine hydrochloride with silver nanoparticles

A visual colorimetric method for the detection of berberine hydrochloride was proposed in this contribution based on the color change caused by the aggregation of silver nanoparticles (AgNps). It was found that citrate-capped AgNps dispersed in water owing to the electrostatic repulsion from each other by the negative charged surface, presenting a bright yellow color. However, the presence of positively charged berberine could induce the aggregation of citrate-capped AgNps, resulting in color change from yellow to green and even to blue depending on the concentration of berberine. Under the optimum condition investigated with UV-vis absorption and light scattering technique, berberine hydrochloride from 0.05 micromol l(-1) to 0.4 micromol l(-1) could be visually detected based on the color alteration of the AgNps suspension.