We developed a simple and cost-effective fabrication technique to construct a hydrogen nanosensor by decorating single-walled carbon nanotubes with Pd nanoparticles. By varying the sensor's synthesis conditions (e.g., Pd electrodeposition charge, deposition potential, and initial baseline resistance of the SWNT network), the sensing performance was optimized. The optimized sensor showed excellent sensing properties toward hydrogen (ΔR/R of 0.42%/ppm) with a lower detection limit of 100 ppm and a linear response up to 1000 ppm. The response time decreased from tens of minutes to a few minutes with increasing hydrogen concentration at room temperature. The sensor's recovery time improved under humid air conditions compared to dry air conditions.

We demonstrate a facile fabrication method to make chemical gas sensors using single-walled carbon nanotubes (SWNT) electrochemically functionalized with polyaniline (PANI). The potential advantage of this method is to enable targeted functionalization with different materials to allow for creation of high-density individually addressable nanosensor arrays. PANI-SWNT network based sensors were tested for on-line monitoring of ammonia gas. The results show a superior sensitivity of 2.44% DR/R per ppm v NH 3 (which is more than 60 times higher than intrinsic SWNT based sensors), a detection limit as low as 50 ppb v , and good reproducibility upon repeated exposure to 10 ppm v NH 3 . The typical response time of the sensors at room temperature is on the order of minutes and the recovery time is a few hours. Higher sensitivities were observed at lower temperatures. These results indicate that electrochemical functionalization of SWNTs provides a promising new method of creating highly advanced nanosensors with improved sensitivity, detection limit, and reproducibility.

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