CTAB Capped β‐Naphthol Nanoparticles as Ratiometric Fluorescent Sensors for Cr (VI): Application to Environmental Sample

The aqueous suspension of fluorescent β‐naphthol organic nanoparticles using CTAB as capping agent (CTAB‐BNNPs) was prepared by reprecipitation approach. The formation of CTAB‐BNNPs confirmed by FESEM technique reveal nanoparticles with spherical morphology, and DLS‐size analyzer supports a narrow particle size distribution with an average particle size of 89 nm. The absorption investigations of CTAB‐BNNPs indicates blue shifted maximum at 275 nm as compared with monomer ( λ ab = 335 nm) whereas the fluorescence spectra of CTAB‐BNNPs also supports to blue shifted emission maximum at 353 nm as compared with monomer BN ( λ em = 431 nm). This observation of blue shifted emission is due to the aggregation induced enhanced emission (AIEE). Furthermore, prepared nanoparticles show selective ratiometric sensing behavior toward Cr 2 O 7 2− ion only. This is because the electrostatic binding attraction between Cr 2 O 7 2− ions and oppositely charged nanochemosensor (CTAB‐BNNPs) resulted in ground state complexation. The ratiometric fluorescence enhancement data was well‐fitted into the calibration curve ( R 2 = 0.99) and the estimated limit of detection (LOD) was found to be 0.2435 µg/mL, which is less than WHO acceptable limit for chromium in drinking water. This proposed analytical assay was successfully applied for the quantitative determination of Cr 2 O 7 2− ion in the river sample.