Dual-Mode Optical Nanosensor Based on Gold Nanoparticles and Carbon Dots for Visible Detection of As(III) in Water

To eliminate the occurrence of false positives and improve the accuracy of measurement results in the process of environmental detection, a single-switch dual-mode nanosensing method should be developed for real-time and in situ detection. Herein, we constructed a colorimetric and fluorescent dual-mode optical nanosensor for accurate detection of As(III) in water. The nanosensor consisted of trithiocyanuric acid modified gold nanoparticles (TMT-Au NPs) and amino-functionalized carbon dots (NCDs). When TMT-Au NPs were injected into the NCDs solutions, the fluorescence of NCDs was weakened due to the overlap of the UV–vis absorption peak of TMT-Au NPs and emission peak of NCDs based on an internal filtering effect. With the addition of As(III), the coordination of As(III) with sulfhydryl groups of TMT-Au NPs occurred, causing the aggregation of TMT-Au NPs for colorimetric detection based on local surface plasmon resonance with a limit of detection (LOD) of 0.87 ppb. Meanwhile, the fluorescence of the NCDs was recovered during the aggregation process of TMT-Au NPs for fluorescence detection with an LOD as low as 0.66 ppb. The reported dual-mode optical nanosensor will be widely used in the field of environmental water detection.