A comparative study of non-vdW Hematene synthesized via different methods for its potential application in NO2 gas sensing

Non-van der Waals (non-vdW) two-dimensional (2D) materials like Hematene, derived from non-layered structures such as α-Fe₂O₃, offer unique advantages over traditional van der Waals (vdW) materials like graphene, transition metal dichalcogenides (TMDs), and phosphorene. Unlike vdW materials that exfoliate along weak interlayer forces, Hematene originates from a strong, non-layered crystal structure, enabling distinct physicochemical properties including greater structural stability, tunable electronic behavior, and enhanced catalytic activity. Recognizing that synthesis methods play a crucial role in shaping these properties, this study systematically compares Hematene synthesized via chemical, microwave, and ultrasonic exfoliation techniques. The results show that chemical exfoliation yields thinner nanosheets with increased surface reactivity, which significantly enhance nitrogen dioxide (NO₂) sensing performance. Notably, the chemically exfoliated Hematene demonstrated a high response of 81% and a rapid response time of 10 s at 20 ppm NO₂ at an optimized operating temperature of 150 °C, outperforming both other exfoliation methods and many conventional vdW-based 2D sensors. These findings highlight the importance of optimizing synthesis strategies to tailor the properties of non-vdW 2D materials. Overall, this work positions Hematene as a promising candidate for high-performance gas sensors and a compelling alternative to traditional vdW materials in next-generation sensing applications. Copyright © 2026. Published by Elsevier B.V.