Soupitak Pal

A chemiresistive gas sensor based on Pt-loaded spinel γ-Fe₂O₃ nanoparticles is reported for the first time to the best of our knowledge for trace-level detection of triethylamine (TEA), a critical indicator of fish spoilage. The sensing material was synthesized via a facile sonochemical route and comprehensively characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Field Emission Scanning Electron Microscopy, UV–Vis spectroscopy, Brunauer-Emmett-Teller (BET) specific surface area analysis, and current-voltage (I-V) measurements. Owing to the intrinsically ordered cation-vacancy architecture of γ-Fe₂O₃ and its modulation upon Pt incorporation, 3 wt% Pt–γ-Fe₂O₃ sensor exhibits outstanding performance, including a low detection limit (200 ppb), ultrafast response (~1.9 s), rapid recovery (~23 s), excellent selectivity against interfering gases, and stability over six months at 300 °C. To elucidate the origin of this superior performance, first principal calculations—performed on γ-Fe₂O₃ for the first time to the best of our knowledge in view of its electronically and magnetically complex spinel structure—were carried out in conjunction with systematic structural and spectroscopic analyses. These findings establish Pt-functionalized γ-Fe₂O₃ as a high-performance and fundamentally distinctive sensing platform and highlight defect-architecture engineering in spinel oxides as a promising strategy for next-generation chemiresistive sensors for real-time food quality monitoring.

Surface termination groups in MXenes stabilize their structure and govern their wide range of applications by modulating the local charge density and work function. However, the precise quantification of MXene surface chemistry remained elusive, with independent measurements on the same MXene often yielding inconsistent results across different characterization techniques. Here, near-accurate composition of surface terminations in MXene is quantified for the first time using a multi-modal characterization approach, primarily based on powder X-ray diffraction, X-ray photoelectron spectroscopy, pair distribution function (PDF) analysis, corroborated by first-principle calculations. For Ti3C2Tx synthesized via hydrofluoric acid etching, the surface chemistry is found to be dominated by mixed oxygen and fluorine terminations, randomly distributed across the available adsorption sites with site occupancies of approximately 84.0% and 16.0%, respectively. Surface electron-density maps reveal pronounced electron localization around oxygen atoms and a longer bond length for Ti–F compared to Ti–O, while Ti atoms display Manuscript Click here to view linked References strong anisotropy. The proposed structural model rationalizes the emergence of the (h0l) reflections in MXene diffraction patterns, which is not predicted by Warren’s theory for randomly oriented 2D lattices. Such observations elucidate the inevitable formation of titanium dioxide nanoclusters during processing and local electronic structure.