Selective sensing of heavy metal ions via fluorescence quenching of femtosecond-laser-synthesized 2D nanoparticles

Abstract

A femtosecond laser is used to break and exfoliate two dimensional (2D) flakes of nitrogen-doped graphene oxide (NGO) or molybdenum disulfide (MoS2) dispersed in acetonitrile or a 1:1 ethanol-water mixture and convert them into nanoparticles (NPs) in 70–100 min. The chemically active NPs bond with atoms from the laser-dissociated acetonitrile or ethanol and water molecules to form 2D NPs functionalized with varying quantities of nitrogen, oxygen, hydrogen, and carbon groups. Sensitive and selective detection of heavy metal ions (HMI) Hg2+, As3+, Pb2+, and Cd2+ is demonstrated with the solvent-functionalized NGO and MoS2 NPs. Binding between the HMI and functional groups leads to quenching of the NPs’ photoluminescence. Limits of detection of 3 nm (Hg2+), 3.8 nm (As3+), 1.8 nm (Pb2+), and 13 nm (Cd2+) are demonstrated with the solvent-functionalized NGO in acetonitrile, NGO in acetonitrile, MoS2 in acetonitrile, and NGO in ethanol-water, respectively. The selectivity is attributed to varying bond polarities associated with the different combinations of NPs and functional groups, which electrostatically attract HMI with different affinities. The functional groups responsible for the selective sensing in the different NP solutions are identified using Fourier transform infrared spectroscopy. This rapid, one-pot, room-temperature process can be used to tailor 2D materials for targeted chemical sensing.