Composition-Tuned Pt-Based Nanobranch Films for Selective, Room-Temperature Gas Detection (1 ppb-100 ppm).

Chemiresistive gas sensors are broadly cross-sensitive, limiting quantitative use in complex mixtures. We address this challenge through materials-and-array co-design: a 480-node library of composition-tuned, dendritic Pt-based nanoparticles (Pt, Pt-Ni, Pt-Ag, Pt-Pd, Pt-Cu, and Pt-Au) was challenged with twelve medically and environmentally relevant gases at 25 °C-namely isoprene, methanol, ethanol, acetone, ammonia, formaldehyde, NO, CO, CO2, H2, CH4, and C3H8-across 1 ppb to 100 ppm. Distinct composition-dependent response fingerprints emerged: Pt-Ni produced the largest formaldehyde response observed here (approximately 2.1% at 100 ppm), whereas Pt-Pd showed the strongest preference for NO (approximately 2.9% at 50 ppm). The films formed homogeneous, percolated networks that delivered reproducible signals, with device-to-device RSD < 4.2% across 480 sensors and >90% response retention over one month at room temperature. These results establish a practical route to heater-free gas sensing through bimetallic composition and array-level response profiling, while identifying humidity validation and multivariate classification as important next steps toward practical breath and environmental applications.