Synthesis and characterization of α-Fe₂O₃ nanoparticles showing potential applications for sensing quaternary ammonium vapor at room temperature

Abstract

P-type and n-type metal oxide semiconductors are widely used in the manufacture of gas sensing materials, due to their excellent electronic, electrical and electrocatalytic properties. Hematite (α-Fe2O3) compound has been reported as a promising material for sensing broad types of gases, due to its affordability, good stability and semiconducting properties. In the present work, the efficient and easy-to-implement sol-gel method has been used to synthesize α-Fe2O3 nanoparticles (NPs). The TGA-DSC characterizations of the precursor gel provided information about the phase transformation temperature and the mass percentage of the hematite NPs. XRD, TEM and XPS data analyses indicated the formation of two iron oxide phases (hematite and magnetite) when the NPs are subjected to thermal treatment at 400 °C. Meanwhile, only the hematite phase was determined for thermal annealing above 500 °C up to 800 °C. Besides, the crystallite size shows an increasing trend with the thermal annealing and no defined morphology. A clear reduction of surface defects, associated with oxygen vacancies was also evidenced when the annealing temperature was increased, resulting in changes on the electrical properties of hematite NPs. Resistive gas-sensing tests were carried out using hematite NPs + glycerin paste, to detect quaternary ammonium compounds. Room-temperature high sensitivity values (Sr ~ 4) have been obtained during the detection of ~1mM quaternary ammonium compounds vapor. The dependence of the sensitivity on the particle size, the mass ratio of NPs with respect to the organic ligand, changes in the dielectric properties, and the electrical conduction mechanism of gas sensing was discussed.

Core‐Shell Architectured Sulfur Coated α‐Fe2O3 Nano‐Sheet Anode for Li‐Ion Battery with Insitu Active Solid Electrolyte Interfacial Layer and Li‐Sulfur Energy Storage Systems

“…The Fe 2p spectra depicts two strong peaks in the binding energy range of 710.7 and 724.1 eV with an energy seperation of 13.4 eV for all the samples, which is corresponding to the Fe 2p 3/2 and Fe 2p 1/2 signals from α-Fe 2 O 3 . [48] The signals of Fe are deconvoluted into a triplet of each signals Fe 2p 3/2 and Fe 2p 1/2 which represent a mixed valance state of Fe 3 + and Fe 2 + of Iron. These two oxidation states of Fe 3 + and Fe 2 + of Fe 2p 3/2 appears at 710.3 eV and 709.3, 712.3 eV for all the samples (α-Fe 2 O 3 , α-Fe 2 O 3 @S-1 and α-Fe 2 O 3 @S-2).…”

“…Figure 3(a–c) shows the core level Fe 2p XPS spectra of bare, sulfur coated α‐Fe 2 O 3 @S‐1 and α‐Fe 2 O 3 @S‐2 samples in the BE range of 705 to 740 eV. The Fe 2p spectra depicts two strong peaks in the binding energy range of 710.7 and 724.1 eV with an energy seperation of 13.4 eV for all the samples, which is corresponding to the Fe 2p 3/2 and Fe 2p 1/2 signals from α‐Fe 2 O 3 [48] . The signals of Fe are deconvoluted into a triplet of each signals Fe 2p 3/2 and Fe 2p 1/2 which represent a mixed valance state of Fe 3+ and Fe 2+ of Iron.…”

Microwave-assisted Synthesis and Characterization of Metal Oxide Nanoparticles for Biological and Electrochemical Applications

“…The most common iron oxides are trivalent oxides, which have four crystalline phases, namely α, ß, γ and . Among these crystalline phases, hematite (α -Fe 2 O 3 ) is the most stable form of iron oxide, with unusual magnetic properties, non-toxicity, and corrosion resistance [15]. The crystal structure is rhombohedral.…”