The effects of pH on iodide and silver TNPs interaction were studied. We found that the interaction between silver TNPs and iodide is stable at pH value range from 6 to 9 (Supporting Information, Fig. S15). However, if silver TNPs was diluted and used for detection very low concentration of iodide (less than 0.1 M), the in presence of 20 mM of B–R buffer (contains various ions) would affect the iodide detection [36]. Our study showed that very low concentration of iodide could be detected after removing B–Rbuffer.