Rapid selective colorimetric sensing of polyphosphates by ionic resorcinarene cavitand interdigitated gold nanoparticles

Abstract

In this article, we show that resorcinarene tetratrimethylammonium tetrabromide cavitand interdigitated gold nanoparticles can be prepared by appropriate choice of solvent and that they can act as efficient colorimetric sensors for the selective detection of polyphosphates such as pyrophosphate, ADP and ATP in aqueous medium. Remarkably, this electrostatically mediated sensing occurs in a minute in biologically relevant HEPES medium and anions such as closely related monobasic- and tribasic-phosphate, various halides including fluoride, acetate, carbonates, nitrate, and sulfate don’t show any colorimetric response. NMR titration showed that the resorcinarene cavitand surfactant binds to pyrophosphate with a binding constant of 4190M−1. Further, we show that PPi can be colorimetrically detected even in the presence of tribasic phosphate, which also binds to the resorcinarene cavitand surfactant with a binding constant of 850M−1. Given the dimensions of the resorcinarene cavitand and the calculated initial interparticle distances of 7.3nm, we believe that the aggregation based sensing of PPi, ADP and ATP occurs by the crosslinking of two resorcinarene cavitand interdigitated nanoparticles by these anions. We show the ratio of absorbance at 700nm and 529nm (A700/A529) and the LSPR of the resorcinarene cavitand interdigitated nanoparticles varied significantly over a wide range of pyrophosphate concentrations with a limit of detection of 140nM.