Quantification of arsenic(iii) in aqueous media using a novel hybrid platform comprised of radially porous silica particles and a gold thin film

Abstract

The use of novel radially porous silica particles and gold thin film hybrid-based spectroscopy for the sensitive and anion-selective detection of As(III) is described. The method is based on the selective formation of electrostatic complexes between As(III) and an amine functionality on the porous silica particles and the effect of this on changes in the surface plasmon resonance (SPR) profiles of the gold thin film. Since silica particles have radially oriented mesopores, the sizes of which gradually increase from the center to the outer surface of the particle, they provide very large surface area, and permit target analytes to easily access active receptors within the pores. Thus, the amine-functionalized silica particles contain much higher concentration As(III) receptors than conventional porous nanoparticles or a flat surface, which results in a lower detection limit. In addition, due to the surface properties of silica as a dielectric spacing layer, it allows the sensing platform to be more sensitive and stable. The SPR properties of the resulting selectively formed complexes are altered, leading to significant changes in SPR reflectance (ΔR) near the SPR angle. The limit of detection of the method was determined to be 1.0 nM, which is ca. 80 times more sensitive than the U.S. EPA regulation level (10 μg L⁻¹ ≈ 130 nM). The response is essentially linear in the concentration range of 10–600 nM on a semi-log scale. The method also shows good selectivity for As(III) in the presence of H₂PO₄⁻, SO₄²⁻, NO₃⁻, and Cl⁻ and is feasible for use in the analysis of tap (drinking) water; therefore, it would be applicable for use in environmental and biological monitoring.