A novel “mix-response” biosensor for colorimetric and photothermal dual-mode detection of sulfide ions in food based on silver-doping Prussian blue nanoparticle

Effective identification of sulfur ions (S2-) in foodstuff is crucial for food safety and human health, but it remains challenging. Traditional single-mode colorimetric sensing methods are simple and sensitive, but are prone to interference from colored substances which can lead to false positives or negatives results. Herein, we develop a novel "mix-response" biosensor for colorimetric and photothermal dual-mode detection of S2- with good simplicity, sensitivity and portability. In this biosensor, silver-doping Prussian blue nanoparticle (SPB NPs) was used as signal output component, which not only exhibits blue color characteristics, but also has photothermal conversion properties activated by near-infrared (NIR) laser. Upon increasing the S2- concentration, the prepared SPB NPs undergo etching, leading to the formation of new silver sulfide precipitation (Ag2S), along with different colorimetric and photothermal response signals. For the portable visualization of S2-, the color information was recorded by a smartphone in combination with RGB (red channel) analysis and the evolution of the photothermal signal was documented by a thermal imager. The introduction of smartphone and handheld thermal imager in this "mix-response" biosensor makes it suitable for on-site quantitative detection of S2- without sophisticated instrument. Moreover, the development of this "mix-response" biosensor does not need the use of recognition probes (e.g. aptamers and reaction intermediates), thereby simplifying the construct procedures of sensing strategies and improving the economic efficiency of detection. More importantly, the photothermal response signals can overcome the interference of colored substances in foods, thereby reducing the false positives or negatives of the detection results.