Carbon dots@metal–organic frameworks as dual-functional fluorescent sensors for Fe3+ ions and nitro explosives

Abstract

Carbon dots (CDs) with excellent optical properties were encapsulated into two fluorescent metal–organic frameworks (MOFs), namely, [Cd(HL)]·0.8H₂O (1) and [Cd₃(L)₂]·3H₂O (2) (H₃L = 4-(5-carboxypyridin-2-yl)isophthalic acid). The as-prepared CDs@1 and CDs+2 not only retained the strong fluorescence activity of CDs, but also embedded Eu³⁺ ions in the hybrids to form dual-emitting Eu³⁺/CDs@1 and Eu³⁺/CDs+2. These novel composites emitted strong red light at room temperature and exhibited good fluorescence sensing capabilities for Fe³⁺ ions, p-nitrotoluene (p-NT) and 2,4-dinitrophenol (2,4-DNP) in water solutions with detection limits of 0.034 μM, 0.0096 μM, 0.062 μM and 0.0111 μM. These results indicate that 1A and 2A (activated products of Eu³⁺/CDs@1 and Eu³⁺/CDs+2) could be regarded as potential dual-functional fluorescent sensors with superior sensitivity and excellent selectivity.