Smart choice of carbon dots as a dual-mode onsite nanoplatform for the trace level detection of Cr2O72-.

Abstract Efficient ways for the trace level monitoring of Cr 2 O 7 2− have generated considerable attention in the fields of medical diagnosis and environmental protection. In current research, the water-soluble carbon dots (CDs) have been developed via the precursors of 1,3-phenylenediamineand citric acid. The quantum dots with particle size of 3–4 nm have been prepared based on a simple one-pot ultrasonic irradiation method and demonstrate bright blue emission at 440 nm. Its excitation-dependent feature has been explored and the achieved emission evolves from blue (440 nm) to green luminescence (528 nm). Photophysical studies support that CDs can be remarkably quenched by the presence of chromate due to inner filter effect. In addition, the absorption curves demonstrate that carbon dots possess highly selective and sensitive responses to Cr 2 O 7 2− through color changes. The dual sensing modes (fluorescence and colorimetric detection) can be well-established for the recognition of chromate and the detection limits are calculated to be as low as 140 nM and 410 nM respectively. To further evaluate the analytical potentials of such nano-platform, the concentration of Cr 2 O 7 2− have been determined in real water and river samples. Highlights • Ultrasonic irradiation was used to assemble carbon dots. • Blue-emissive carbon dots were prepared. • Excitation-dependent feature was explored. • Dual sensing modes were developed. [ABSTRACT FROM AUTHOR]