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

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 Fe 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 Fe. The sensing mechanism is based on the effective oxidation etching of Au-Cu core-shell nanocubes induced by Fe, accompanied by the in situ generation of PB NPs. It can be attributed to the specific reaction between ferrous ions (Fe) from the reduction of Fe and potassium ferricyanide (K[Fe(CN)]) 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 Fe determination. Such colorimetric change signals of characteristic absorbance at 740 nm in the UV-vis spectra showed a sensitive response to Fe with a LOD of 210 nM. Moreover, as a sensitive photothermal probe, PB NPs generated in our Fe-enabled reaction system also exhibited a sensitive response to Fe with a LOD of 70 nM. In addition, the standard addition experiments demonstrate our photothermal and colorimetric probe has good applicability for Fe 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.