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 viavesicle–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 µg L⁻¹ by extracting only 5 mL of sample volume with satisfactory reproducibility (RSD = 5.21%, C = 10 µg L⁻¹, n = 6), which are directly comparable to those attained with more sophisticated techniques.