Photothermal and colorimetric dual mode detection of nanomolar ferric ions in environmental sample based on in situ generation of prussian blue nanoparticles

Abstract

Iron ions play a key role in many physiological processes, which can provide feedback for the evaluation of biological systems and environmental processes. New strategies for portable determination of Fe³⁺ therefore are still in urgent need. Here, through an in situ generation of prussian blue nanoparticles (PB NPs) in aqueous solution, we developed a bimodal method for photothermal and colorimetric detection of Fe³⁺. The sensing mechanism is based on the effective oxidation etching of Au-Cu core-shell nanocubes induced by Fe³⁺, accompanied by the in situ generation of PB NPs. It can be attributed to the specific reaction between ferrous ions (Fe²⁺) from the reduction of Fe³⁺ and potassium ferricyanide (K₃[Fe(CN)₆]) in the reaction solution. The in situ produced PB NPs show distinct bare-eye-detectable readouts with highly sensitive colorimetric and photothermal responses and thus can be used for Fe³⁺ determination. Such colorimetric change signals of characteristic absorbance at 740 nm in the UV-vis spectra showed a sensitive response to Fe³⁺ with a LOD of 210 nM. Moreover, as a sensitive photothermal probe, PB NPs generated in our Fe³⁺-enabled reaction system also exhibited a sensitive response to Fe³⁺ with a LOD of 70 nM. In addition, the standard addition experiments demonstrate our photothermal and colorimetric probe has good applicability for Fe³⁺ detection in the river water sample. What's more, the proposed strategy opens a new horizon for affordable detection of metal ions using a common thermometer, and therefore has a great potential for analytical chemistry and some important applications such as environmental monitoring, disease diagnostics and food analysis.

Keywords: Au–Cu core-shell nanocubes; Colorimetric; Ferric ions; Photothermal; Prussian blue nanoparticles.