Synergism of Edge Effect and Interlayer Engineering of VS₂ on CNFs for Rapid and Precise NO₂ Detection

Abstract

Although two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit attractive prospects for gassensing applications, the rapid and precise sensing of TMDs at low loss remains challenging. Herein, a NO 2 sensor based on an expanded VS 2 (VS 2 -E)/carbon nanofibers (CNFs) composite (abbreviated as VS 2 -E-C) with ultrafast response/recovery at a low-loss state is reported. In particular, the impact of the CNF content on the NO 2 -sensing performance of VS 2 -E-C was thoroughly explored. Expanded VS 2 nanosheets were grafted onto the surface of hollow CNFs, and the combination boosted the charge transport, exposing abundant active edges of VS 2 , which enhanced the adsorption of NO 2 efficiently. The activity of the VS 2 edge is further confirmed by stronger NO 2 adsorption with a more negative adsorption energy (−3.42 eV) and greater than the basal VS 2 surface (−1.26 eV). Moreover, the exposure of rich edges induced the emergence of the expanded interlayers, which promoted the adsorption/desorption of NO 2 and the interaction of gas molecules within VS 2 -E-C. The synergism of edge effect and interlayer engineering confers the VS 2 -E-C3 sensor with ultrafast response/recovery speed (9/10 s) at 60 °C, high sensitivity (∼2.50 to 15 ppm NO 2 ), good selectivity/stability, and a low detection limit of 23 ppb. The excellent "4S" functions indicate the promising prospect of the VS 2 -E-C3 sensor for fast and precise NO 2 detection at low-loss condition.

Room Temperature Ultrasensitive NO2 Detection by Activating VS2 Basal Planes in Rare-Earth Nd-Doped VS2/Carbon Nanofibers

“…The calculated total energy of the defect structure with a vacancy in the S1 position is lower than that in the S2 position, revealing that the S1 position is more energetically favorable for S vacancies in Nd-VS 2 -C. Figure (f) illustrates the top and side views of the fully relaxed absorption configurations of the NO 2 molecule on the surface of Nd-VS 2 with the S vacancy in the S1 position. The calculated adsorption energy E ad in Figure (f) is −3.12 eV, which is significantly higher than the E ad (−1.26 eV) of NO 2 adsorbed on the pure VS 2 surface reported in our previous work using the same calculations method and parameters . Furthermore, the top and side views of the corresponding 3D isosurface charge density differences are presented in Figure (g).…”

“…Subsequently, due to the excellent carrier mobility and large hollow space, CNFs were chosen as growth templates for VS 2 in order to expose more edges of the VS 2 nanosheets, to fully utilize the edge effects of TMDs to enhance the NO 2 -sensing response. The VS 2 -E (11.6 Å)/CNFs heterojunction (abbreviated as VS 2 -E - C) shows a fast response/recovery speed (9 s/10 s) and ∼2.50 intense response to 15 ppm of NO 2 at 60 °C . The stronger NO 2 adsorption at the edges of VS 2 nanosheets can also be verified by a more negative −3.42 eV adsorption energy than −1.26 eV of the VS 2 (001) basal planes.…”

“…The electron accumulation (yellow contours) denotes the intense interaction of 0.300 e transfer from Nd-VS 2 -C to NO 2 . However, only 0.138 e are found to transfer from pure VS 2 surface to NO 2 . Also, the calculated E ad for NO 2 molecule absorbed on the surface of Nd-VS 2 with S vacancy in the S2 position is given in Figure S3 as a supplement.…”

“…Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have garnered growing attention as promising RT gas sensing materials on account of their large specific surface area and efficient charge transfer processes. , Owing to the outstanding electrical conductivity and the sensitive variation of carrier concentration to external stimuli, VS 2 shows great possibilities in the gas sensors realm, especially for the sensitive detection of NO 2 at low temperatures. , As one of the most dangerous toxic and hazardous gases, NO 2 poses a serious threat to the atmospheric environment and human health . In our previous reports, , VS 2 with expanded interlayer spacing (11.6 Å) (abbreviated as VS 2 -E) was prepared by NH 4 + intercalation. The expanded interlayer spacing greatly promoted the adsorption/desorption and diffusion rate of NO 2 between the VS 2 interlayers, which is mainly responsible for the rapid response/recovery of VS 2 -E .…”

Toward High Selectivity of Sensor Arrays: Enhanced Adsorption Interaction and Selectivity of Gas Detection (N2, O2, NO, CO, CO2, NO2, SO2, AlH3, NH3, and PH3) on Transition Metal Dichalcogenides (MoS2, MoSe2, and MoTe2)

“…Given that the typical recovery of TMD sensors takes at least several minutes, the theoretical values make it clear that the desorption of the basal plane of the TMD monolayers does not determine its rate. This process is likely slowed down by the interaction of molecules or their accumulation at the edges [20,87,88], resulting in slower release of analyte molecules. Therefore, enhanced adsorption is unlikely to meaningfully affect the experimentally observed recoveries.…”