Development of a chromium speciation probe based on morphology-dependent aggregation of polymerized vesicle-functionalized gold nanoparticles

Abstract

In this work, a new approach for visual sensing of Cr3+ in aqueous solutions is presented, based on the morphological changes induced by Cr3+ on (4-carboxybenzyl)bis[2-(undec-10-enyloxycarbonyl)ethyl]methylammonium bromide (4-CBUAB)-polymerized vesicles. CTAB-stabilized gold nanoparticles (GNPs) react with 4-CBUAB-polymerized vesicles to form aggregates via vesicle-micelle interactions, which does not proceed further because of vesicle-vesicle repulsive forces, creating a large polymerized vesicle-gold nanoparticle (PV-GNP) conjugate. The incorporation of Cr3+ through the 4-CBUAB polymeric membrane induces structural perturbations on the polymerized vesicle morphology by swelling of the lamellar phase which is reflected in the morphology of the polymerized vesicle-gold nanoparticle conjugate assembly. These steric perturbations induce a linear increase in the absorbance of the solutions as a function of Cr3+ concentration, a feature which was exploited for the analytical determination of Cr3+ in real samples. Owing to the high selectivity of the polymerized vesicular aggregate no interferences from co-existing species were observed, enabling the determination and speciation of Cr3+ in real samples with minimal sample pre-treatment and without preconcentration. The analytical merits afford detection limits as low as 0.72 microg L(-1) by extracting only 5 mL of sample volume with satisfactory reproducibility (RSD = 5.21%, C = 10 microg L(-1), n = 6), which are directly comparable to those attained with more sophisticated techniques.