Cetyltrimethyl ammonium mediated enhancement of the red emission of carbon dots and an advanced method for fluorometric determination of iron(III).

Red-emissive carbon dots (CDs) were synthesized by one-step hydrothermal technique using citric acid (CA), and urea in N,N-dimethylformamide (DMF) solution. The CDs has an average diameter of 2.3 nm, excitation/emission maxima at 553/606 nm, and a low photoluminescence quantum yield (4%). Fluorescence is weakly quenched by the ions Fe3+, Hg2+, Cu2+, Co2+, Zn2+, Ca2+, Ni2+, and Pb2+. After addition of cetyltrimethyl ammonium ion (CTAB), electrostatic interaction between negatively charged CDs and CTAB causes the CDs to self-aggregate. The formation of CD/CTAB increases the average particle diameter to around 13 nm and enhances the quantum yield to 24%. The hydrophobic segments of CTAB twined into a network structure can selectively trap Fe3+ and then interact with surface groups of the CDs to cause quenching. The CD/CTAB nanoprobe enables fluorometric determination of Fe3+ with a linear response in the 0.10-10 μM concentration range and a 0.03 μM limit of detection. The probe was utilized for determination of Fe3+ in human serum samples, and satisfactory results were obtained. Graphical abstractSchematic representation of fluorometric analysis of Fe(III) ion by cetyltrimethyl ammonium ion (CTAB) mediated red emission carbon dots (CDs). The hydrophobic segments of CTAB twined into a network structure can selectively trap Fe(III) and then interact with surface groups of the CDs to cause quenching.