Ultrasensitive determination of silver ion based on synchronous fluorescence spectroscopy with nanoparticles.

Based on the characteristics of synchronous fluorescence spectroscopy (SFS), a new method with high sensitivity and selectivity was developed for rapid determination of silver ion with functional cadmium sulphide (CdS) nanoparticles as a fluorescence probe. When Delta lambda (lambda(em) - lambda(ex)) = 215 nm, maximum synchronous fluorescence is produced at 304 nm. Under optimal conditions, functional cadmium sulphide displayed a calibration response for silver ion over a wide concentration range from 0.8x10(-10) to 1.5x10(-8) mol L(-1). The limit of detection was 0.4x10(-10) mol L(-1) and the relative standard deviation of seven replicate measurements for the lowest concentration (0.8x10(-10) mol L(-1)) was 2.8%. Compared with several fluorescence methods, the proposed method had a wider linear range and improved the sensitivity. Furthermore, the concentration dependence of the synchronous fluorescence intensity is effectively described by a Langmuir-type binding isotherm.