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A hybrid thin film is fabricated by a simple drop-casting method. Functionalized single-walled carbon nanotubes (SWCNTs) and gold nanoparticles (AuNPs) with a diameter of ≈15 nm are drop-casted onto a printed circuit board (PCB) substrate equipped with interdigitated electrodes. The addition of AuNPs to the carbon nanotube networked films enhance sensitivity and lower the detection limit to low parts-per-billion (ppb) concentrations. The gold particle to carbon nanotube ratio is optimized to find the optimum gold nanoparticle loading. The composite films were tested in both air and nitrogen environments across a wide relative humidity range (0-97%), which is suitable for dissolved Nitric Oxide (NO) detection in sea water for oceanographic study and for human breath analysis in medical diagnosis. The sensors exhibited high selectivity, particularly to NO, outperforming other tested gases. Notably, the sensor reliably detected NO at 10 ppb levels with response times within 10 seconds and recovery time around 1 minute, showcasing excellent reproducibility across sensors and operational efficiency within diverse humidity conditions.