Fluorescent and smartphone-assisted colorimetric dual-mode sensor for Ag⁺ detection based on orange-red emitting carbon dots

A novel fluorescent and smartphone-assisted colorimetric dual-mode sensor is constructed for Ag+ monitoring based on orange-red emitting carbon dots (or-CDs). The as-synthesized or-CDs possess strict excitation independence and show specific response to Ag+. Ag+ can induce fluorescence quenching of the or-CDs through dynamic quenching characteristic. The quenching efficiency and Ag+ concentration show good linear relationships in the ranges of 0.8-10 mu M and 10-100 mu M with the limit of detection (LOD) down to 56 nM. More interestingly, these phenomena are accompanied by visible color conversion (red-brown) under the sunlight. So, we develop a portable smartphone-assisted colorimetry for Ag+ monitoring via the red-green-blue (RGB) analysis with the linear range of 10-80 mu M and LOD of 0.78 mu M. Furthermore, the or-CDs have realized the monitor of Ag+ in human serum and the Fenhe River with good recoveries (96.37-103.20%) and relative standard deviations (RSDs, <3%) by fluorescence and smartphone-based RGB analysis.