Carbon dots and AuNCs co-doped electrospun membranes for ratiometric fluorescent determination of cyanide

Due to the extremely toxic nature of cyanide, the World Health Organization (WHO) has set 1.9 mu M as the maximum acceptable level in drinking water. Therefore, methods for facile screening and on-site detection of cyanide is urgently needed. In this work, a ratiometric fluorescent method for cyanide detection was developed based on blue-emitting carbon dots (CDs) and red-emitting AuNCs. To suit an on-site detection, the two fluorophores were incorporated into a nanofibrous membrane through electrospinning, yielding the core-shell structure of CDs/AuNCs-PVA@CA. Upon reaction with cyanide, the red fluorescence of AuNCs was quenched but the blue fluorescence of CDs was retained, resulting in ratiometric fluorescence change. Besides, both CDs and AuNCs can be excited with a handheld UV lamp (365 nm), and the resultant visible fluorescence color change could be visualized with naked eye. The proposed ratiometric method provided a limit of detection (LOD) 0.15 mu M for cyanide, which was far lower than 1.9 mu M. The membrane was further employed for screening analysis of cyanide in tap water samples. After collection of 500 analytical results, only 5.6% of the results located outside the X +/- 2s criteria, while for the X +/- 3s criteria, there is no outlier. The statistical results indicated that the proposed method may be potentially useful for screening analysis of cyanide in water samples.