Smartphone-Assisted Colorimetric Detection of Cr~(3+) using Vitamin B6 Cofactor Functionalized Gold Nanoparticles and Its Applications in Real Sample Analyses

摘要

This communication demonstrates a rapid, reproducible and highly selective colorimetric nanosensor for the detection of Cr~(3+) ions in aqueous medium using the functionalized gold nanoparticles. The functionalized AuNPs were obtained in three steps: (i) the citrate capped Cit-AuNPs were prepared by standard procedure, (ii) the thiolated Schiff base CAPLP was generated in-situ by reacting vitamin B6 cofactor pyridoxal 5'-phosphate and cysteamine, and then (iii) the CAPLP was decorated over the surface of Cit-AuNPs via ligand exchange method yielding spherical and well dispersed nanoparticles of size ~16±2 nm. The wine red color of CAPLP-AuNPs solution turned to purplish blue upon addition of Cr~(3+) ions along with the SPR band was red-shifted from 525 nm to 650 nm due to the complexation-induced aggregation of nanoparticles. With a high selectivity and specificity, this nano-assembly shows the detection limit down to 2.34 μM and finds applicability over a wide range of pH. The developed nanosensor was applied in environmental water samples for Cr~(3+) ions detection and achieved ideal results. More significantly, the visually detectable color change of CAPLP-AuNPs has been successfully integrated with a smartphone RGBColorValue app to make it useful for on-site fast measurement and real-time online analysis of Cr~(3+) with the detection limit down to 11 μM.