A giant enhancement of nearly 100 times is seen in triethylamine response through Ti-Zr-Cr-V-Ni high-entropy alloy nanoparticle (HEA NP)-induced fermi energy control of two-dimensional molybdenum disulfide (MoS2) nanosheets. These Laves-phase HEA NP-decorated MoS2 samples are synthesized using cryomilling followed by 30 h of sonication. The prolonged sonication results in well-exfoliated MoS2 with fairly small (∼10-20 nm) HEA NPs anchored due to cryomilling confirmed by extensive microscopic and spectroscopic examinations. The presence of HEA NPs leads to reduction in edge oxidation of MoS2 as seen from X-ray photoelectron spectroscopy. Moreover, this edge state reduction causes strong Fermi level pinning, which is commonly observed in layered MoS2 with bulk metal electrodes. This leads to target gas-specific carrier-type response and selective oxidation of TEA vapors due to highly catalytically active metals. The resulting composite (MoS2 + NPs) exhibits high response (380% for 2000 ppm TEA vapors) along with selectivity toward TEA at 50 °C. The cross-sensitivity of the composite to other volatile organic compounds and NH3, CO, and H2 has been very minimal. Thus, the highly selective catalytic activity of metal alloy NPs and their Fermi energy control has been proposed as the prime factors for observed large sensitivity and selective response of MoS2 + NP nanocomposites.
Keywords: Fermi energy control; gas sensor; high-entropy alloys; molybdenum disulfide (MoS2); triethylamine.