AUTHOR=Lee Jong Hyun , Kang Se Hwang , Park Gi Hyun , Kim Min Young , Ji Sanghyun , Choa Ha Eun , Han Gi Hyeon , Hwang Jeong Yun , Lee Seung Yong , Lee Kyu Hyoung 

TITLE=Emerging NO2 gas sensing on substitutionally doped Fe on NiWO4 SCES insulators

JOURNAL=Frontiers in Chemistry

VOLUME=12

YEAR=2024

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2024.1480356

DOI=10.3389/fchem.2024.1480356

ISSN=2296-2646

ABSTRACT=<p>In this study, we demonstrate the emergence of NO<sub>2</sub> gas sensing capabilities in the typically non-active NiWO<sub>4</sub>, a strongly correlated electron system (SCES), by introducing substitutional Fe at the Ni site. NiWO<sub>4</sub> typically exhibits strong Coulombic repulsion between Ni atoms, resulting in a large band gap of over 3.0 eV and insulating behavior. This correlated behavior is clearly reflected in the significant increase of band gap when considering the Hubbard <italic>U</italic> correction for the cations, bringing the theoretical value closer to the observed value. The single-phase Fe<sub>0.5</sub>Ni<sub>0.5</sub>WO<sub>4</sub> displays a notable shift in the [NiO<sub>6</sub>] symmetric vibration mode and an increase in magnetization. Additionally, theoretical calculations confirm the preservation of the wide band gap, with the Fe and O levels generated within the band gap. These findings indicate that Fe located in the Ni sites modulate Coulombic repulsion in NiWO<sub>4</sub> SCES insulators. Unlike the poor gas-sensing performance of intrinsic NiWO<sub>4</sub>, Fe<sub>0.5</sub>Ni<sub>0.5</sub>WO<sub>4</sub> exhibits a significant NO<sub>2</sub> response (R<sub>g</sub>/R<sub>a</sub>) of 11 at 200°C than other gases and a limit of detection (LOD) of 46.4 ppb. This study provides a pathway for realizing gas-sensing performance in strongly correlated electron insulators with large band gaps through the introduction of dopant levels at the cation sites.</p>