Single-Molecule Methane Sensing Using Palladium-Functionalized nIR Fluorescent Single-Walled Carbon Nanotubes
Xun Gong, Seon‐Yeong Kwak, Soo‐Yeon Cho, Daniel J. Lundberg, Albert Tianxiang Liu, Melissa Keiko McGee, Michael S. Strano
Abstract
There has been considerable interest in detecting atmospheric and process-associated methane (CH 4 ) at low concentrations due to its potency as a greenhouse gas. Nanosensor technology, particularly fluorescent single-walled carbon nanotube (SWCNT) arrays, is promising for such applications because of their chemical sensitivities at single-molecule detection limits. However, the methodologies for connecting the stochastic molecular fluctuations from gas impingement on such sensors require further development. In this work, we synthesize Pd-conjugated ss(GT) 15 -DNA-wrapped SWCNTas near-infrared (nIR) fluorescent, single-molecule sensors of CH 4 . The complexes are characterized using X-ray photoelectron spectroscopy (XPS) and spectrophotometry, demonstrating spectral changes between the Pd 2+ and Pd 0 oxidation states. The nIR fluctuations generated upon exposure from 8 to 26 ppb of CH 4 were separated into high- and low-frequency components. Aggregating the low-frequency components for an array of sensors showed the most consistent levels of detection with a limit of 0.7 ppb. These results advance the hardware and computational methods necessary to apply this approach to the challenge of environmental methane sensing.