Ordered 2D Gold Nanoparticle Films for Sensing of Toluene and Ethanol Gases

The use of metallic nanoparticles as building blocks toward the synthesis of self-assembled films creates intriguing opportunities for generating advanced materials with multifunctional properties. To achieve that, uniformed gold nanoparticles protected by alkanethiols have been used to form highly ordered two-dimensional (2D) monolayer films at the air/water interface with the aid of the Langmuir–Blodgett technique. These films display a highly ordered hexagonal close-packed structure with controlled interparticle distance at 1.3 ± 0.45, 1.9 ± 0.65, and 2.2 ± 0.64 nm, respectively, by changing the chain length of alkylthiol ligands. Further investigation suggests that the driving force of the formation of ordered 2D nanoparticle films is the van der Waals force, which is exponentially decreased with the increase of the chain length of alkylthiol ligands. Significantly, their optical, adhesive, hydrophobic, and electric properties can also be varied by changing the chain length of alkylthiol ligands. Based on their excellent performances, they have been used for designing vapor sensors to detect toluene and ethanol gases, which have been found to possess excellent stability, appreciable recovery time, and much lower LOD than other sensing systems. Besides, important parameters of these nanoparticle films have been obtained, including active energy, electrical conductivity, and contact angle. In summary, our research provides an effective way for preparing uniformed hydrophobic gold nanoparticles and forming highly ordered 2D hexagonal close-packing films via regulation of nanoparticle interactions during self-assembly, and these films not only have excellent multiple performances but also have many promising applications, such as sensors.