Reusable sensor based on functionalized carbon dots for the detection of silver nanoparticles in cosmetics via inner filter effect

•Functionalization via amidation reaction of the carbon dots.•Carbon dot surface is chemically modified with ethylenediamine moieties.•High affinity of amine ending groups of CD surface to silver core of citrated AgNPs.•Reusable and fluorescent nanosensor versus citrated AgNPs.•A selective method to determine AgNPs versus other TiO2 NPs in a cream is presented.

We report a low cost selective analytical method based on inner filter effect (IFE) for citrate-silver nanoparticle (cit-AgNP) detection, in which fluorescent amine-derivatized carbon dots (a-CDs) act as the donor and aggregated cit-AgNPs as the energy receptor. Carbon dots (CDs) were chemically modified with ethylenediamine (EDA) moieties via amidic linkage displaying an emission band at 440 nm. The presence of cit-AgNPs produces a remarkably quenching of a-CD fluorescence via IFE, since the free amine groups at CD surface induce the aggregation of cit-AgNPs accompany by a red-shifting of their characteristic plasmon absorption wavelength, which resulted in “turn-on” of the IFE-decreased in CD fluorescence. The proposed method, which involves the use of chelating agents for removal of metal ions interferences, exhibits a good linear correlation for detection of cit-AgNPs from 1.23 × 10−5 to 6.19 × 10−5 mol L−1, with limits of detection (LOD) and quantification (LOQ) of 5.17 × 10−6 and 1.72 × 10−5 mol L−1, respectively. This method demonstrates to be efficient and selective for the determination of cit-AgNPs in complex matrices such as cosmetic creams and reveals many advantages such as low cost, reusability, high sensitivity and non time-consuming compared with other traditional methods.

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