Selective Detection of Ethylene by MoS<sub>2</sub>–Carbon Nanotube Networks Coated with Cu(I)–Pincer Complexes
Winston Yenyu Chen, Aiganym Yermembetova, Benjamin M. Washer, Xiaofan Jiang, Shoumya Nandy Shuvo, Dimitrios Peroulis, Alexander Wei, Lia Stanciu
Abstract
The plant hormone ethylene (C2) can induce premature fruit ripening and flower senescence at levels below 1 ppm, which has motivated efforts to develop cost-effective methods for C2 monitoring during the transport and storage of climacteric fruits. Here, we describe a nanocomposite film composed of exfoliated MoS2, single-walled carbon nanotubes (SCNTs), and Cu(I)–tris(mercaptoimidazolyl)borate complexes (Cu–Tm) for real-time detection of C2 at levels down to 100 ppb. A copercolation network of MoS2 and SCNTs was deposited onto interdigitated Ag electrodes printed on plastic substrates and then coated with Cu–Tm with a final conductance in the 0.5 mS range. Reversible changes in relative conductance (−ΔG/G0) were measured upon C2 exposure with a linear response at sub-ppm levels. The thin-film sensors were highly selective toward C2, and they responded weakly to other volatile organic compounds or water at similar partial pressures. A mechanism is proposed in which Cu–Tm behaves as a chemically sensitive n-type dopant for MoS2, based on spectroscopic characterization and density functional theory modeling. Cu–Tm-coated MoS2/SCNT sensors were also connected to a battery-powered wireless transmitter and used to monitor C2 production from various fruit samples, validating their utility as practical, field-deployable sensors.