The sensitive, anion-selective detection of arsenate with poly(allylamine hydrochloride) by single particle plasmon-based spectroscopy

The use of single gold nanoparticle plasmon-based spectroscopy for the sensitive, anion-selective detection of arsenate is described. The method is based on the selective formation of electrostatic complexes between arsenate and poly(allylamine hydrochloride) (PAH) and changes in the single particle plasmon in Rayleigh scattering profiles. PAH, when modified with gold nanoparticles, binds arsenate via its amine-functionalities. The scattering properties of the resulting selectively formed complexes are altered, leading to significant changes in the surface plasmon resonance wavelength. The limit of detection of the method was determined to be 10 nM, which is ca. 13 times more sensitive than U.S. EPA regulation levels. The response is essentially linear in the concentration range of 50–300 nM. The method also shows good selectivity for arsenate in the presence of other environmentally relevant anions, including H2PO4−, SO42−, NO3−, and Cl−.