Sensitive colorimetric detection of K(I) using catalytically active gold nanoparticles triggered signal amplification

Abstract In this work, we report a simple, ultrasensitive, and feasible colorimetric assay for metal ion (K + , used as a model) via inherent peroxidase-like enzymatic amplification strategy of gold nanoparticles (AuNPs). It is shown that peroxidase-like activity of AuNPs can be improved dramatically by its surface activation with target-specific aptamer molecules. Whereas when the target exists, the aptamers leave the surface of AuNPs in a target concentration-dependent manner, resulting in a decrease of the nanoenzymatic catalytic ability of AuNPs. Thus, K + can be quantified in the presence of AuNPs by using a colorimetric sensing probe (3,3′,5,5′-tetramethylbenzidine). The color change of the solution is relevant to the dose of the target, and this can be achieved with the naked eyes and monitored by UV–vis spectrometry. A linear dependence between the absorbance and target K + concentration is obtained under optimal conditions in the range from 0. 1 nM to 1 μM with a detection limit (LOD) of 0.06 nM estimated at the 3S blank level . The sensitivity displays to be 2–9 orders of magnitude better than those of other K + detection methods. This sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.