Bimetallic-based colorimetric sensor for highly selective, stable and sensitive detection of iodide ions

Too much or too little iodine in the body can affect person's health. Therefore, iodide detection is particularly important. In this work, a novel bimetallic nanoparticle sensor based on colorimetric signal responses was developed for the visual detection of I − . Gold nanoparticles (AuNPs) were prepared by in situ reduction of chloroauric acid using gelatine (Gel) as reducing agent, and further constructed as gold-platinum (Au-Pt) alloy nanoparticle. Au-Pt alloy have unique structure and excellent synergistic effects, which provide higher I − detection sensitivity and stability compared to single-metal nanoparticles. The probe undergoes a redox reaction with I − , which causes the colour to change from buff to rufous, enabling colorimetric detection of I − . The probe is more eye-catching than commonly reported I − detectable colour change based on the aggregation of single metal nanoparticles, and this colour change based on steady-state chemical reactions can remain stable for a long time, which makes it easy to record and detect. The probe showed good linearity over the I − concentration range of 0–1.1 mM with a linear fit coefficient of 0.9943 and a lowest limit of detection (LOD) of 0.29 μM. Moreover, the probe showed very high selectivity for I − and was successfully applied to detection of I − in seawater and tap water. More importantly, the probe remains stable at a temperature of 50 ℃ and a salinity of 12 g/L, broadening its practical application range in a variety of harsh conditions. In summary, the probes have great potential for I − detection and analytical applications.