Nanohybrids of a MXene and transition metal dichalcogenide for selective detection of volatile organic compounds

Abstract

Two-dimensional transition metal carbides/nitrides, known as MXenes, have been recently receiving attention for gas sensing. However, studies on hybridization of MXenes and 2D transition metal dichalcogenides as gas-sensing materials are relatively rare at this time. Herein, Ti₃C₂T_x and WSe₂ are selected as model materials for hybridization and implemented toward detection of various volatile organic compounds. The Ti₃C₂T_x/WSe₂ hybrid sensor exhibits low noise level, ultrafast response/recovery times, and good flexibility for various volatile organic compounds. The sensitivity of the hybrid sensor to ethanol is improved by over 12-fold in comparison with pristine Ti₃C₂T_x. Moreover, the hybridization process provides an effective strategy against MXene oxidation by restricting the interaction of water molecules from the edges of Ti₃C₂T_x. An enhancement mechanism for Ti₃C₂T_x/WSe₂ heterostructured materials is proposed for highly sensitive and selective detection of oxygen-containing volatile organic compounds. The scientific findings of this work could guide future exploration of next-generation field-deployable sensors.

Fig. 1. Ti₃C₂T_x/WSe₂ hybridization and sensor fabrication.

a Schematic illustration of preparation processes for Ti₃C₂T_x/WSe₂ nanohybrids. b Schematic illustration of inkjet-printed gas sensors in detection of volatile organic compounds with a wireless monitoring system. c Zeta potential distributions of Ti₃C₂T_x, WSe₂, and CTA⁺-WSe₂ dispersions.

Fig. 2. Microstructure analysis of Ti₃C₂T_x/WSe₂ nanohybrids.

a SEM image of 2D Ti₃C₂T_x/WSe₂ nanohybrid film (scale bar, 2 μm). b Low magnification TEM image (scale bar, 200 nm), with c showing image of a single Ti₃C₂T_x/WSe₂ nanohybrid (scale bar, 100 nm). d High-resolution TEM image of Ti₃C₂T_x/WSe₂ nanohybrid (scale bar, 100 nm). e Selected area electron diffraction pattern of Ti₃C₂T_x/WSe₂ nanohybrids (scale bar, 2 nm^–1). f HAADF-STEM image and corresponding elemental mapping of Ti, W, and Se for the Ti₃C₂T_x/WSe₂ nanohybrid showing a uniform decoration of WSe₂ nanoflakes on Ti₃C₂T_x matrix.

Fig. 3. Chemical composition of Ti₃C₂T_x/WSe₂ nanohybrids.

High-resolution XPS spectra of a Ti 2p, b O 1s, c C 1s, and d W 4f from Ti₃C₂T_x/WSe₂ nanohybrids, showing chemical components and structures of Ti₃C₂T_x/WSe₂ nanohybrids.

Fig. 4. Sensing characteristics of MXene-based VOC sensors.

a Real-time sensing response of Ti₃C₂T_x and Ti₃C₂T_x/WSe₂ gas sensors upon ethanol exposure with concentrations ranging from 1 to 40 ppm. b Comparison of gas response as a function of ethanol gas concentrations for Ti₃C₂T_x and Ti₃C₂T_x/WSe₂ sensors. c Cycling performance of Ti₃C₂T_x/WSe₂ gas sensors in response to ethanol at 40 ppm level. d Long-term stability of response over a month under 40 ppm of ethanol for Ti₃C₂T_x/WSe₂ sensor. e Response and recovery times calculated for 40 ppm of ethanol. f Selectivity test of the Ti₃C₂T_x and Ti₃C₂T_x/WSe₂ sensors upon exposure to various VOCs at 40 ppm.

Fig. 5. Environmental stability of Ti₃C₂T_x and hybrid Ti₃C₂T_x/WSe₂ films.

Changes in electrical conductance of pristine Ti₃C₂T_x and hybrid Ti₃C₂T_x/WSe₂ sensors under a 5% RH and b alternative RHs of 5 and 80% over 10 days. c Evolution of responses of Ti₃C₂T_x/WSe₂ sensors to 40 ppm of ethanol under various RHs and d the sensing responses as a function of RHs from 5 to 80%.

Fig. 6. Mechanical stability of hybrid Ti₃C₂T_x/WSe₂ films.

a Photograph of a flexible Ti₃C₂T_x/WSe₂ nanohybrid sensor. b Changes in ethanol sensing response and electrical conductance as a function of bending cycles.

Fig. 7. Enhanced sensing mechanism of Ti₃C₂T_x/WSe₂ heterostructure.

Energy-band diagram of the Ti₃C₂T_x/WSe₂ in a air and b ethanol, showing the variation of the depletion layer with interaction between adsorbed oxygen species and ethanol molecules.