title: Controlled growth of conical nickel oxide nanocrystals and their high performance gas sensing devices for ammonia molecule detection.
abstract: NiO nanocones with good symmetry and highly ordered structure on NiO foil substrate have been successfully fabricated via a facile wet chemical approach combined with subsequent high temperature oxidation. These organized conical superstructures grow only along a certain direction and be controlled via the self-assembly and oriented attachment of a nucleus, which mainly rely on the similar surface energies and the extent of lattice matching of the oriented attached surfaces. During high temperature oxidation, the electric field created via the Ni(2+) and O(2-) facilitates Ni(2+) diffusion outward along the grain boundaries and O(2-) diffusion inward toward to meet the Ni(2+) ions, forming NiO. The as-grown NiO nanocones are 50-350 nm in diameter and 50-400 nm in height. The tip diameter of the nanocone is about 30 nm and the apex angle of the nanocone is about 40°. Meanwhile, we systematically investigated the gas sensing properties of the sensors based on the as-fabricated NiO foil covered with nanocone arrays for ammonia detection at room temperature. The results show that the gas sensing devices have outstanding sensitivity, reproducibility and selectivity, which are mainly because of the excellent connection between the NiO sensing materials and the Au electrodes, the strong electron donating ability of ammonia and the large active surface of selective physisorption for ammonia.
authors.affiliation: School of Materials Science and Engineering, Xihua University, Chengdu, Sichuan 610039, P. R. China. wangjianxhu@163.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Wei
authors.forename: Yafei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Liangming
authors.initials: L
authors.lastname: Wei
authors.forename: Jianjun
authors.initials: J
authors.lastname: Zhang
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Tang
authors.forename: Biao
authors.initials: B
authors.lastname: Guo
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
mesh_terms: D000641:Ammonia / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles; D009532:Nickel / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000641:Ammonia; D009532:Nickel; C028007:nickel monoxide