Advanced Composite for sp3‐Carbon‐Based Gas Sensing Application from Gold Organometallic Single Nanolayering on Diamondoids

Abstract The assembly of hybrid materials combining a pure sp 3 ‐C platform from nano‐and microcrystals of molecularly‐defined nanometer‐sized functionalized diamondoids (nanodiamonds) coated with a gold transition metal nanolayer is conducted from the gas phase, following a two‐steps vapor phase dry construction process. By using first the controlled vapor phase self‐assembly of primary phosphine diamantane derivatives, followed by a chemical vapor decomposition of a suited gold organometallic complex the synthesis of the nanocomposite Au@H 2 P–DiamOH 2 is achieved. The gold deposit surface analysis reveals the formation of a Au–P covalent bonding, which excludes the formation of phosphine oxide, as confirmed at higher depth into the nanocomposite by Hard X‐ray Photoelectron Spectroscopy analysis (HaXPES). The thickness d of the gold layers deposited onto the surface of diamondoids is estimated to be around d = 0.8 ± 10% nm from XPS data, which allows combining the composite Au@H 2 P–DiamOH 2 with ITO interdigitated electrodes, to produce a long‐life, highly stable and reproducible, n‐type behavior sensor for ammonia detection. A relative response (RR) of 150% at 30 ppm and a limit of detection of 6 ppm are measured at room temperature (20 to 25 °C) and at 45% of relative humidity.