Multi-mode detection of iodine based on Au@Ag nanoparticle array with highly sensibility and stability using plasmonic surface lattice resonances

Designing a sensor to rapidly and simply detect iodine (I2) in liquid and gaseous phase with excellent sensitivity, high stability, and low cost at room temperature is highly desirable. Herein, a two-dimensional Au@Ag nanoparticle ordered array was prepared by template method combined with chemical reduction for detecting I2 at room temperature. Due to the ordered structure, a plasmonic surface lattice resonances (PSLR) peak appeared in extinction spectrum of the Au@Ag nanoparticle ordered array. When the ordered array exposed to I2, the Ag shell would react with I2 to form AgI, thus leading to a change in the dielectric medium surrounding the Au nanoparticles. This change would cause a variation of color and a shift of PSLR peak, realizing multi-mode detection of liquid and gaseous I2 at room temperature without any sophisticated instrument. With the increase of I2 concentration, the color of the Au@Ag nanoparticle array changed from red to yellow-green. Meantime, the PSLR peak displayed highly sensitive redshift with a larger offset (about 156 nm) and intense signal strength. Moreover, due to the ordered array structure, the PSLR peak possessed good uniformity and stability. Therefore, the PSLR peak was more suitable for detecting I2 in a large concentration region. Furthermore, the practical application of the present prepared Au@Ag nanoparticle array was explored by detecting gaseous I2 at room temperature. It was found that the Au@Ag nanoparticle array possessed high sensitivity to gaseous I2 with a detection limit reaching to trace level (1 ppb), suggesting tremendous potential for real-world application.