Carbon Dot-functionalized Interferometric Optical Fiber Sensor for Detection of Ferric Ions in Biological Samples.

This work reports an interferometric optical microfiber sensor functionalized with nitrogen- and sulfur-codoped carbon dots (CDs) for the detection of ferric ions (Fe). Compared to other CD-based ferric ion sensors, the sensing mechanism of this presented sensor is dependent on the refractive index modulations due to selective Fe adsorption onto the CD binding sites at the tapered region. This is the first study in which CD-based sensing was performed at the solid phase as a chelator, which does not rely on its fluorescence properties. The detection performance of the proposed sensor is not only comparable to a conventional fluorescence-based CD nanoprobe sensor but also capable of delivering quantitative analysis results and ease of translation to a sensor device for on-site detection. The presented sensor exhibits Fe detection sensitivity of 0.0061 nm/(μg/L) in the linear detection range between 0 and 300 μg/L and a detection limit of 0.77 μg/L based on the Langmuir isotherm model. Finally, the potential use of the CD-functionalized optical microfiber sensor in the real environmental and biological Fe monitoring applications has also been validated in this work.