Chemical State Properties Research Articles

Study of a palladium nanoparticle/ In-Zn-O thin film-based hydrogen gas sensor

A comprehensive study on the hydrogen (H2) gas sensing performance of a novel chemoresistive gas sensor is presented in this work. This sensor is synthesized by an In-Zn-O (IZO) thin film and palladium nanoparticles (Pd NPs) on a sapphire (Al2O3) substrate. The relevant elemental, compositional, and chemical state properties are systematically investigated for the fabricated Pd NP/IZO sensor. The use of Pd NPs effectively enhances the surface area to volume (SA/V) ratio and related catalytic capability. This significantly improves the hydrogen sensing characteristics. In the experiment, the produced sensor achieves a higher sensing response SR of 1.59×104 under 1 % H2/air gas and a lower detectable content of 100 ppb H2/air at 250 °C. Importantly, the fabricated sensor reveals promised selectivity, reproducibility, and long-term (90 days) durability towards H2 gas. Therefore, the studied sensor offers a prominent choice for H2 gas detection.

DEPOSITION OF PLCT THICK FILMS BY A MODIFIED SOL-GEL PROCESSING

ABSTRACT The PLCT thick films were spin-deposited on various substrates by using a modified sol-gel process. The crystallization, surface morphology and the chemical state's properties of the PLCT thick films have been investigated. It is revealed that the success of this route is due to the elimination of the agglomeration among the nanometer particles. SEM observation shows that the PLCT thick films are rather smooth and have a good distribution of small grains. The chemical state of PLCT thick films were also analyzed by used XPS.

Gersdorffite (NiAsS) chemical state properties and reactivity toward air and aerated, distilled water

This first X-ray Photoemission Spectroscopic (XPS) study of gersdorffite (NiAsS) reveals a strong, asymmetric, singlet peak in the Ni 2 p spectrum. It represents Ni of the bulk phase (fully coordinated), bonded to As-S dimers. The high binding-energy tail on the Ni 2 p spectrum includes a core-level-shifted Ni surface species and a Doniach-Sunjic high-energy tail characteristic of conductors. A third contribution, likely a hydroxylated Ni species (Ni-OH), is also observed. The XPS characteristics of gersdorffite suggest it is a compound conductor. Identical secondary surface products form on gersdorffite during reaction with both air and aerated, distilled water. Reaction rates in aerated water are more than tenfold greater than in air with arsenic being the most reactive element toward these oxidizing fluids and sulfur being the least reactive. Arsenate and arsenite are produced either in acidic form or as Ni-salts. The S 2 p spectrum does not change appreciably with exposure to the oxidized fluids, although minor quantities of surface species of intermediate oxidation state were detected. The Ni 2 p signal of gersdorffite becomes weaker relative to the As 3 d signal, and the O 1 s signal strength increases, as reaction with air proceeds. Changes to the strengths of these signals probably results from accumulation of H 2 O and oxidized As species in the secondary overlayer developed on bulk gersdorffite. The S 2 p signal strength decreases with respect to the As 3 d signal during reaction with air, probably because S is “buried” beneath the hydrated, As-enriched secondary overlayer (overlayer deficient in Ni and S). In contrast to air-reacted surfaces, the Ni 2 p signal of water-reacted surfaces remains strong relative to the intensity of the As 3 d signal. This may be explained by the high solubility of arsenites and arsenates, relative to Ni(OH) 2 , present at the oxidized gersdorffite surface.