Fluorescence sensors for titanium (IV) and mercury (II) based on doped carbon dots synthesized from acetamide and thioacetamide, a comparative study

Abstract

Carbon dots doped with nitrogen and sulfur (N, S-CDs and N-CDs) were synthesized by microwave from two initial precursors such as thioacetamide and acetamide with similar structure and one atom difference. Difference in doping agent in similar conditions affects surface functional groups, morphology, and optical properties of the CDs. Morphology and structure of the CDs were characterized by FT-IR, UV–Vis, and TEM. A novel turn off fluorescent probe for titanium was reported for the first time based on these N, S co-doped CDs that synthesized from thioacetamide. At optimum conditions (pH = 7, λ_ex = 340 nm, and λ_em = 422 nm), linear dynamic range and detection limit were 0.1–50 μM and 29 nM, respectively. Quenching was very fast after addition of Ti⁴⁺ that is an important property of this sensor. Nitrogen-doped carbon dots were also successfully synthesized from acetamide and used as turn off fluorescent probe for Hg²⁺. Under optimum condition (pH = 8; λ_ex = 350 nm; λ_em = 424 nm), dynamic range and detection limit Hg²⁺ for were 0.1–50 μM and 49 nM, respectively. Good sensitivity and selectivity, simple and green synthesis method, low-cost materials, solubility in water, very fast response time and applicability in real sample such as tap and mineral water samples are advantages of these fluorescence probes.