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

Carbon dots (CDs) with excellent optical properties were encapsulated into two fluorescent metal-organic frameworks (MOFs), namely, [Cd(HL)]center dot 0.8H(2)O (1) and [Cd-3(L)(2)]center dot 3H(2)O (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 mu M, 0.0096 mu M, 0.062 mu M and 0.0111 mu M. 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.