Ocimum sanctum Leaf Extract-Assisted Green Synthesis of Pd-Doped CuO Nanoparticles for Highly Sensitive and Selective NO2 Gas Sensors

In view of facile, cost-effective, and environmentallyfriendlysynthetic methods, palladium-doped copper oxide (Pd-CuO) nanoparticleshave been synthesized from Ocimum sanctum (commonly known as "Tulsi") phytoextract for gas-sensingapplications. The structural, morphological, and compositional propertiesof Pd-doped CuO nanoparticles were studied using various techniquessuch as XRD, FESEM, XPS, and EDX. The characterization results confirmedthe doping of Pd on CuO nanoparticles, and Pd-CuO nanostructures appearas nanoflakes in FESEM analysis. The gas-sensing response of Pd (1.12wt %)-CuO nanoflake-based sensor was measured at 5-100 ppmconcentration of different gases, NO2, H2S,NH3, and H-2, at 125 & DEG;C. Gas-sensing testsreveal that the sensitivity of the sensor were 81.7 and 38.9% for100 and 5 ppm concentrations of NO2, respectively, whichwas significantly greater than that of pure CuO. The response andrecovery times of the sensor were 72 and 98 s for 100 ppm of NO2 gas, while they were 90 and 50 s for 5 ppm NO2. The calculated limit of detection (LOD) value of the sensor is0.8235. This appealing LOD is suitable for real-time gas detection.The gas sensor was found to exhibit excellent selectivity toward NO2 gas and repeatability and stability in humid (80%) conditions.The Pd doping in CuO nanostructures plays a significant role in escalatingthe sensitivity and selectivity of CuO-based NO2 gas sensorsuitable to work at low operating temperatures.