Realizing High Performance Tunable Sensing Mode and Selectivity of Metal Ions Based on Carbon Dot

Abstract We have adopted a straightforward, eco‐friendly and economically profitable pyrolysis route of tailoring quantum dot size carbon particles (CD) from the leaves of Arundo donax. The synthesized uniformly dispersed CD1 and CD2 have an average diameter of 4.5 nm and 3.5 nm respectively as determined via HRTEM. FT‐IR analysis corroborated nitric acid treatment leads to rich surface functionalization of CD2. Experimentally estimated average fluorescence (FL) lifetime of the as‐prepared CD1 and CD2 are 2.31 ns and 3.87 ns respectively. Juxtapose to other metal ions, Cd⁺² ions can efficiently quench FL of CD1, while Cr⁺⁶ ions, on contrary, prominently enhanced FL of CD2. Benefitting from their FL response, a turn off sensor was built using CD1 to detect Cd⁺² ions and a turn on‐off sensor by CD2 to sense Cr⁺⁶ with impressive limit of detections of 2.58 nM and 1.73 nM respectively. They exhibit superior performance compare to other documented nanoscopic materials. The FL “turn off” interaction mechanism of CD1 was attributed mainly to static quenching. While that of “turn on‐off” mechanism for CD2 was ascribed to chelation enhanced fluorescence phenomenon and a rare partial combination of inner filter effect plus dominate dynamic type of quenching.