Ratiometric Fluorescent Sensor for Al³⁺ Based on the Inner Filter and Static Quenching Effects of Carbon Dots Obtained from Neem Leaves

Abstract

The level of Al3+ is an indicator for many diseases of human, so the selective and sensitive detection of Al3+ is critically important for human health. In this study, a simple and sensitive ratiometric fluorescent sensor for the detection of Al3+ in the aqueous solution was developed based on the inner filter effect (IFE) and static quenching effect (SQE) of the carbon dots (CDs) and fluorescein. The preparation of CDs was facile and green by a one‐step hydrothermal method, using the fresh Melia azedarach L. leaves as the raw material. The fluorescence of CDs at 430 nm was quenched owing to the combination of IFE and SQE while the fluorescence of fluorescein at 515 nm was enhanced upon adding fluorescein. Meanwhile, fluorescein interacted with Al3+ resulting in the quenching of the fluorescence of fluorescein at 515 nm and the recovering of the fluorescence of CDs at 430 nm with the addition of Al3+ into the system of CDs‐fluorescein. The linear range of the ratiometric fluorescent sensor (F515/F430) for Al3+ detection was 0–500 μM and the detection limit was 0.216 μM. Importantly, it had been successfully applied in the detection of Al3+ in the drinking and environmental water.

Chemically modified graphitic carbon nitride nanosheets for the selective turn-off fluorescence detection of Al(iii) ions in crabs (Brachyura)

“…It is well known that Al( iii ) has a high tendency to form a stable complex with O and N-donor ligands as a result of the successive electron transfer between OH/g-CN and Al( iii ), and this can be the reason for the quenching phenomena of the fluorescence emission caused by the presence of Al( iii ) ion. 44–46 As shown in Fig. 3C, the concentration of Al( iii ) was increased from 0 to 4.0 ppm; subsequently, the intensity of fluorescence emission of OH/g-CN at 377 nm ( λ max 290 nm) decreased gradually until complete quenching happened at 4 ppm Al( iii ).…”

“…Subsequently, the interactions between OH/g-CN and Al(III) results in the return of these excited electrons from the CB of OH/g-CN to the LUMO of the target cations. [45][46][47] Therefore, the complete quenching of the uorescence intensity is a result of the recombination of photoinduced electron-holes. Fig.…”

From Weed to Shining ‘Mystic Stars’: Value‐Added Applications of Siam Weed Derived Carbon Dots

“…The prepared system could act as an effective and selective sensor of folic acid realized through fluorescence quenching, with a limit of detection of 4.5 μM. The specific quenching [27] in the luminescence of CO‐CDs in presence of folic acid is credited to the inner filter effect [4b,28,4b,25,28b,29] . The practical use of the sensor has been confirmed by real sample analysis, by quantifying folic acid present in commercially available Folate tablets [30] .…”

Application Progress of Green Carbon Dots in Analysis and Detection

“…The IFE is different from FRET, which is a simple absorption process and can still occur even if the distance between the g‐CDs and the quencher is more than 10 nm. [ 70 ] Liu et al. [ 71 ] made g‐CDs that can detect myricetin and studied its mechanism.…”