Enhanced Electrical, Optical, and Magnetic Properties in Multifunctional ZnO/α-Fe₂O₃ Semiconductor Nanoheterostructures by Heterojunction Engineering

Abstract

Here we report the facile synthesis of 1D ZnO/α-Fe2O3 semiconductor nanoheterostructures (SNHs), and we investigate the strong interfacial interactions at the heterojunction, resulting in novel multifunctional properties. ZnO-coated α-Fe2O3 nanowires (NWs) have been prepared by combining electrodeposition and wet chemical methods. Significant improvement in electrical conductivity, photoluminescence, and room temperature magnetic properties have been observed for the ZnO/α-Fe2O3 SNHs over the pristine α-Fe2O3 NWs because of the contribution of the ZnO nanolayer. The increase in electrical conductivity in ZnO/α-Fe2O3 SNHs is because of the increase in free electrons in the conduction band of the SNHs due to the formation of type-II n-n band configuration at the heterojunction. The SNHs are found to exhibit enhanced visible green photoluminescence along with the UV emission at room temperature. The band-gap emission of the α-Fe2O3 NWs coupled to the defect emissions of the ZnO in SNHs can be attributed to the profound enhancement of the visible green luminescence. Magnetization of the SNHs is found to be increased nearly five times in magnitude over the primeval α-Fe2O3 NWs, which can be ascribed to the exchange coupling of the interfacial spin at ZnO/α-Fe2O3 interface, the surface spin of ZnO nanolayer, along with the structural defects like the cation vacancies (V Zn) and the singly ionized oxygen vacancies (V o •) present in SNHs.

Phase-controlled synthesis of polymorphic MnO2 structures for electrochemical energy storage

“…S3d. The rst involves the intercalation/extraction of protons (H 3 O + ) or alkali cations such as Li + , Na + or K + into the bulk of the oxide particles with the concomitant reduction/oxidation of Mn ions: 28,29 MnO 2 + H 2 O + xK + + (x + 1)e À 4 K x MnOOH + OH À (1) shows a schematic diagram of the growth of the products.…”

Enhanced Light Absorption and Charge Carrier Management in Core‐Shell Fe2O3@Nickel Nanocone Photoanodes for Photoelectrochemical Water Splitting

“…Now, to substantiate the chemical nature of Fe in deposited iron oxide, Fe2 p core level XPS spectra are recorded for all three 3D samples and analyzed as shown in Figure a and Figure S5 (Supplementary Information). The Fe2 p 3/2 and Fe2 p 1/2 peaks for all the samples are centered around binding energies 711 eV and 725 eV, respectively, which are typical values for Fe 3+ in Fe 2 O 3 and Fe 3 O 4 , and are not compatible with that for FeO . A satellite peak of the Fe2 p 3/2 main line can also be identified at ∼719 eV, which further substantiates the presence of Fe 3+ species .…”

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe2O3//ZnO/C Asymmetric Supercapacitor

“…In the light of the fact that ZnO has high electronic conductivity due to its intrinsic oxygen vacancies and lower work function as well as lower electron affinity compared to α-Fe 2 O 3 , which cause a band bending toward ZnO during formation of ZnO/α-Fe 2 O 3 n/n heterojunction, further facilitates electron transfer from α-Fe 2 O 3 shell to ZnO core during redox reactions. 20,32 Furthermore, annealing of FeOOH in N 2 atmosphere during conversion to α-Fe 2 O 3 significantly enhances the shell electron density through incorporation of excessive amounts of oxygen vacancies in α-Fe 2 O 3 lattice, thus improving its electronic conductivity as well. Furthermore, thin porous layer of α-Fe 2 O 3 shortens ion-diffusion length for fast-ion motion and charge transfer.…”