Polymorph-Specific Electronic Transduction in WO₃ during Molecular Sensing.

Area of Science:

• Materials Science
• Surface Chemistry
• Solid-State Physics

Background:

• Polymorphs of tungsten oxide (WO3) are investigated for molecular sensing applications.
• The underlying mechanisms of their differing chemoresistive properties remain poorly understood.

Purpose of the Study:

• To elucidate the mechanistic aspects of chemoresistive response generation in WO3 polymorphs.
• To introduce energetic allocation of transferred charge as a key metric beyond net-transfer for gas-solid interactions.

Main Methods:

• Combined operando work function measurements, chemisorption analysis, and in situ spectroscopy.
• Utilized density functional theory calculations for theoretical validation.
• Focused on acetone as the target analyte for both gamma- and epsilon-WO3 polymorphs.

Main Results:

• Both gamma- and epsilon-WO3 exhibit similar surface-level acetone activation via electron-deficient tungsten sites.
• Epsilon-WO3 uniquely stabilizes analyte-induced electronic states near the conduction band, crucial for conductivity modulation.
• These subsurface electronic rearrangements in epsilon-WO3 correlate with superior transduction efficiency despite comparable surface chemistry.

Conclusions:

• Energetic allocation of transferred charge provides a novel perspective on chemoresistive sensing mechanisms.
• Intrinsic electronic structure, particularly subsurface states, is critical for designing efficient chemical transducers.
• This framework enables rational development of advanced WO3-based sensors.