Palladium nanoparticles (PdNPs) have been synthesized using n-alkylamines (C n -NH 2 ) as stabilizing ligands. The NP size and distribution were controlled by varying the initial mole ratio of PdCl 2 /C n -NH 2 and carbon chain lengths of C n -NH 2 including hexylamine (C 6 -NH 2 ), dodecylamine (C 12 -NH 2 ), and octadecylamine (C 18 -NH 2 ). The average PdNP sizes were 20 ( 2.0, 6.0 ( 0.8, 5.6 ( 0.8, 6.5 ( 0.9, and 5.2 ( 0.8 nm prepared with 1:7 PdCl 2 /C 6 -NH 2 , 1:7 PdCl 2 /C 12 -NH 2 , 1:7 PdCl 2 /C 18 -NH 2 , 1:5 PdCl 2 /C 18 -NH 2 , and 1:9 PdCl 2 /C 18 -NH 2 , respectively. The particle size decreased with the increase in the carbon chain length of C n -NH 2 . The as-synthesized n-alkylamine stabilized PdNPs (C n -NH 2 -PdNPs) were fully characterized by transmission electron microscopy, X-ray powder diffraction, UV-visible absorption spectroscopy, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), proton nuclear magnetic resonance ( 1 H NMR) spectroscopy, thermogravimetric analysis, graphite furnace atomic absorption spectrometry, and mass spectrometry. The interaction of C 18 -NH 2 with PdNPs was verified by IR, XPS, and 1 H NMR spectra, demonstrating that the amine functionalities were successfully linked to the Pd core surfaces. The PdNPs are soluble and stable in apolar solvents such as benzene, chloroform, n-hexane, and toluene. The electrochemical reactions between CH 4 and C n -NH 2 -PdNPs on Pd electrodes were studied by cyclic voltammetry and chronoamperometry. These PdNPs reacted readily and produced good response to CH 4 at ambient conditions. The sensitivity to CH 4 depends on the PdNPs prepared from various n-alkyl chain lengths of C n -NH 2 and also the mole ratio of PdCl 2 /C n -NH 2 . It was determined that PdNPs synthesized from 1:7 PdCl 2 /C 18 -NH 2 displayed the best electrocatalytic oxidization of CH 4 . The C 18 -NH 2 -PdNP (5.6 nm) modified Pd electrode could be used repeatedly and had a stable and reproducible response to CH 4 .
