Mo6+ − doped In2O3 nanowire sensors for enhanced trimethylamine sensing and fish freshness monitoring

The 3 mol% Mo 6+  − doped In 2 O 3 nanowires exhibit a high response of 233.5 and a LOD as low as 25.4 ppb for TMA detection. • Substitutional Mo 6+ and surface MoO 3 jointly regulate surface oxygen chemistry and charge transfer. • Mo 6+ doping induces concurrent regulation of lattice, electronic, and surface properties in In 2 O 3 nanowires. • The Mo 6+  − doped In 2 O 3 sensor demonstrates practical application in fish-freshness monitoring through TMA detection. Marine fish are highly susceptible to deterioration during capture, transportation, and storage, accompanied by the generation of malodorous trimethylamine (TMA), making rapid TMA detection highly desirable for freshness assessment. In this work, Mo − containing In 2 O 3 nanowires with different nominal Mo/In ratios were synthesized, and their TMA sensing properties were systematically investigated. The 3 mol% Mo sample (3IMO) exhibited the optimal sensing performance, with the optimal operating temperature decreasing from 220 °C for undoped 0IMO to 200 °C, while the response toward 100 ppm TMA increased markedly from 32.2 to 233.5. The 3IMO sensor also exhibited a rapid response time of 2 s, a recovery time of 262 s, and a low limit of detection (LOD, 0.0254 ppm). Structural analyses reveal that the introduced Mo exists predominantly as substitutional Mo 6+ incorporated into the In 2 O 3 lattice, accompanied by a minor amount of highly dispersed surface MoO 3 nanocrystallites. The enhanced sensing behavior is therefore attributed to the synergistic contributions of these two Mo configurations: lattice-incorporated Mo 6+ provides the dominant regulation of carrier/surface-charge characteristics and surface oxygen chemistry, whereas trace surface MoO 3 provides auxiliary interfacial charge modulation and possible Lewis-acidic adsorption sites. Combined with the pronounced enrichment of chemisorbed oxygen species, these effects facilitate TMA surface redox reactions and amplify resistance modulation. Furthermore, practical fish-storage experiments demonstrate that the 3IMO sensor can effectively track the freshness deterioration, showing consistency with pH and Quality Index Method (QIM) sensory evaluations. These results demonstrate the potential of Mo − modified In 2 O 3 nanowires for sensitive TMA detection and fish freshness monitoring. Download: Download high-res image (236KB) Download: Download full-size image