Magneto‐Photoactivated Gold Plasmonic Nano‐Islands and Quantum Dot Assemblies for ppt‐Level NO ₂ Detection

ABSTRACT

The intrinsic instability and limited chemical reactivity of metal nanoparticles have long restricted their direct integration in chemiresistive gas sensing. Here, we present a highly selective, tunable, ultra‐stable, and ultra‐sensitive NO ₂ sensor derived from gold nano‐islands (GNIs) and quantum dot (QD) assemblies anchored on a reactive sodium aluminophosphosilicate glass matrix (H1‐glass). Thermal dewetting of sputtered Au films at 550°C under ambient conditions initiates a reactive glass‐metal interaction (RGMI), leading to the formation of Au‐rich core/semiconducting shell GNIs along with spatially dispersed QDs on the glass surface. Magnetometry and magnetic force microscopy reveal the emergence of room‐temperature ferromagnetism across the GNI array. The resulting H1‐Au sensor, featuring robustly embedded GNIs and QDs, demonstrates an exceptional chemiresistive response of 73.5% toward 40 ppm NO ₂ , with a remarkable detection limit of 50 ppb, and maintains full functionality at temperatures down to 0°C. Notably, the synergistic application of external magnetic fields and light irradiation further amplifies the sensor response to 11.67% at an ultralow concentration of 50 ppt NO ₂ , outperforming all previously reported chemiresistive gas sensing platforms. These findings establish RGMI‐stabilized GNIs as a highly reliable and versatile platform for ultra‐trace, low‐temperature gas detection, with broad implications for chemical, environmental, and biomedical monitoring applications.