Detection of Amaranth and Iron in Foods by Modified Carbon Quantum Dots as a Ratiometric Fluorescence Probe

Graphical Citric acid (CA) and N-[3-(trimethoxysilyl)propyl]ethylenediamine (TPED) were dissolved in formamide to prepare carbon dots (CDs) by a microwave-assisted method. The obtained CDs were further modified with 3,5-dichloro-2-hydroxybenzaldehyde. The modified CDs (G-CDs) showed a new emission peak at 520 nm and a weaker emission peak at 450 nm; thus, a new ratiomeric fluorescence (RF) probe was obtained. The RF probe could be used for sensitively and selectively monitoring of amaranth AM and Fe 3+ . In this work, a new carbon quantum dots (CDs) was prepared though microwave assisted approach using citric acid anhydrous (CA) and N-[3-(Trimethoxysilyl)propyl] ethylenediamine (TPED) as raw materials. However, the CDs was not effective in actual sensing applications, so further modification of CDs was done by 3,5-Dichloro-2-hydroxybenzaldehyde (it was named as G-CDs). Fortunately, the modified CDs (G-CDs) has good selectivity for Fe 3+ and amaranth. Studies confirmed that Fe 3+ could quench the fluorescence of G-CDs by forming a complex, while the fluorescence quenching mechanism of G-CDs by amaranth (AM) mainly belonged to the internal filtering effect (IFE). A detection limit of 20.8 nM for Fe 3+ and 43.8 nM for AM were achieved. Moreover, the as-developed G-CDs probe was also successfully used to detect Fe 3+ and amaranth in real samples, and compared with their results by the standard method, hinting that the accuracy and reliability of the probe were highly satisfactory.