Colorimetric detection of pesticides based on calixarene modified silver nanoparticles in water.

Highly stable silver nanoparticles modified with p-sulfonatocalix[n]arene (n = 4, 8) were synthesized via a one-pot protocol in aqueous media and characterized by transmission electron microscopy, FT-IR and UV-vis spectroscopy. In comparison with p-sulfonatocalix[8]arene modified silver nanoparticles, p-sulfonatocalix[4]arene modified silver nanoparticles can be utilized as a novel colorimetric probe for optunal, allowing a rapid quantitative assay of optunal down to a concentration of 10(-7) M, showing a great potential for application to real-time in situ detection of optunal. The possible mechanism is discussed.