title: Chemically linked AuNP-alkane network for enhanced photoemission and field emission.
abstract: Size and ligand effects are the basis for the novel properties and applications of metallic nanoparticles (NPs) in nanoelectronics, optoelectronics, and biotechnology. This work reports the first observation of enhanced photoelectron emission from metallic Au NPs ligated by alkanethiols. The enhancement is based on a conceptually new mechanism: the AuNP provides electrons while the alkane ligand emits electrons due to its low or negative electron affinity. Moreover, the AuNP-ligand chemical bonding is found to significantly facilitate the transmission of photoexcited electrons from the AuNP to the ligand emitter. Consequently the smooth NP film, which is a typical low-aspect-ratio two-dimensional structure, exhibits strong and stable field emission behavior under photoillumination conditions. The photoenhanced field emission is related to the interband and surface plasmon transitions in AuNPs, and a photoenhancement factor of up to approximately 300 is observed for the AuNP-based field emission. This is highly remarkable because field emission is often based on one-dimensional, high-aspect-ratio nanostructures (e.g., nanotubes and nanowires) with geometrical field enhancement effect. The chemical linkage of electron-supplying AuNP and electron-emitting alkane ligand represents a fundamentally new mechanism for efficient photoexcitation and emission. Being low-temperature/solution processable, and inkjet printable, AuNPs may be a flexible material system for optoelectronic applications such as photodetection and photoenhanced field emission.
authors.affiliation: NUS Nanoscience and Nanotechnology Initiative (NUSNNI), National University of Singapore. nnixxn@nus.edu.sg
authors.forename: Xian Ning
authors.initials: XN
authors.lastname: Xie
authors.forename: Xingyu
authors.initials: X
authors.lastname: Gao
authors.forename: Dongchen
authors.initials: D
authors.lastname: Qi
authors.forename: Yilin
authors.initials: Y
authors.lastname: Xie
authors.forename: Lei
authors.initials: L
authors.lastname: Shen
authors.forename: Shuo-Wang
authors.initials: SW
authors.lastname: Yang
authors.forename: Chorng Haur
authors.initials: CH
authors.lastname: Sow
authors.forename: Andrew Thye Shen
authors.initials: AT
authors.lastname: Wee
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D011789:Quantum Theory; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry
chemical_list: D000473:Alkanes; D008024:Ligands; D013455:Sulfur; D006046:Gold