Highly Surface Active Phosphorus-Doped Onion-Like Carbon Nanostructures: Ultrasensitive, Fully Reversible, and Portable NH3 Gas Sensors

Unique phosphorous doped onion-like carbon nanostructures (P-OLCs) with superior surface properties have been synthesized through a temperature and pressure controlled thermal decomposition method. The substitutional doping of phosphorous in OLCs nanostructures could facilitate the charge transfer during ammonia gas sensing. Presence of polar metaphosphates/phosphonate species in the active sites of highly crystalline P-OLCs due to interstitial doping of oxygen incorporated with substitutionally doped phosphorous atoms significantly enhanced the sensitivity with fast response and recovery characteristics (2.8 s and 4.5 s) towards NH3 at room temperature. Further, ammonia gas adsorption kinetics in OLCs and P-OLCs have been meticulously investigated which revealed the faster adsorption rate in P-OLCs (2.17 x 10-7 Ω-1s-1) compared to pristine OLCs (8.599 x 10-8 Ω-1s-1). This method can widely open up the feasibility to induce enhanced surface activity (phosphorus-containing groups allows the access of oxyge...