CdS QDs/N-methylpolypyrrole hybrids as fluorescent probe for ultrasensitive and selective detection of picric acid.

Abstract

Inorganic-organic hybrids are an advanced class of luminescent materials showing great promise for fabrication of highly sensitive and selective optical sensors. In the present study, a novel CdS quantum dots/N-methylpolypyrrole (CdS QDs/NMPPY) hybrid was synthesized via the direct polymerization of NMPPY on L-cysteine capped CdS QD aggregates. A number of characterization techniques including FTIR, DLS, FESEM, UV-vis, and fluorescence spectroscopies were used to study the chemical composition, morphology and optical properties of the resultant QDs/polymer hybrid. The as-synthesized CdS QDs/NMPPY hybrid shows a bright emission at 459 nm under excitation at 367 nm in water. Also the results show the role of sodium dodecyl benzenesulfonate (SDBS) to control the mechanism of synthesis and spectroscopic of the prepared CdS/NMPPY hybrid. Moreover, in this work was reported the direct hybridization procedure without other modification such as ligand exchange and coating. We demonstrated that the hybridization of CdS QDs with NMPPY polymer leads to a significant change in fluorescence sensing properties toward nitroaromatic compounds. Further studies unveiled that the emission of CdS QDs/NMPPY hybrid is strongly and selectively quenched by picric acid molecule with a large Stern-Volmer constant of 843,900 M-1 and an excellent detection limit of 4.6 × 10-7 M. The changes in the UV-vis spectra of picric acid solutions in the presence and absence of CdS QDs/NMPPY hybrid displayed that the fluorescence quenching occurs through a static quenching mechanism. Finally, the proposed CdS QDs/NMPPY sensor was successfully utilized to determine the amount of picric acid in real water samples.