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The type of aggregation in conjugated polymers determines their use in electronic devices. H-type aggregates are most suitable for solar cell applications, while J-type aggregates are recommended for light-emitting diodes. In this work, we used three methods to determine the type of aggregates in a benzodithiophene–isoindigo-based (PBDTI-DT) copolymer, namely, Huang–Rhys factor evolution with temperature, Franck–Condon analysis, and relative quantum yield (QY) calculation. All three methods indicate that both aggregation types are present, and the QY calculation clearly indicates that H-aggregates are more dominant. Time-dependent density functional theory was used to identify the two absorption bands of PBDTI-DT as local π − π* and intramolecular charge-transfer transitions. [ABSTRACT FROM AUTHOR]

In this article, we studied the structural, electrical, lattice vibrational, and magnetic properties of the quaternary compound Zn(1−x)FexSeyTe(1−y) using density functional theory. All the calculations have been performed based on first-principles calculations using Perdew–Zunger [local-density approximation (LDA)] and Hubbard parameter correction (LDA+U) functionals as employed in the Quantum Espresso package. The computed equilibrium lattice parameter for ZnTe is 6.01 Å, and the energy bandgap, Eg, is 1.362 eV, which is consistent with the experimental values as well as the previous reports, respectively. The influence of the co-doping of iron and selenium on electrical and magnetic properties in a ZnTe system is discussed in detail. The co-doping of iron and selenium affects metallic behavior in these systems by forming localized states between the conduction and valance bands. The presence of localized states is related to the metallic properties of the iron atom, specifically iron 3d orbitals. The spin-polarized density of state and band structure computations also confirmed that the iron and selenium co-doped ZnTe system exhibits significant half-metal ferromagnetic and dilute magnetic semiconductor features at room temperature. Furthermore, the phonon calculation of these systems indicated that the systems are dynamically stable and that localized frequency states are created at higher frequencies due to the presence of iron atoms. As a result, the iron and selenium co-doped ZnTe systems can be considered for magnetic and spintronic device applications at room temperature, pending further experimental research. [ABSTRACT FROM AUTHOR]

A simple wet chemical ultrasonic-assisted synthesis method was employed to prepare visible light-driven g-C3N4-ZnO-Co3O4 (GZC) heterojunction photocatalysts. X-ray diffraction (XRD), scanning electromicroscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), ultraviolet (UV), and electrochemical impedance spectroscopy (EIS) are used to characterize the prepared catalysts. XRD confirms the homogenous phase formation of g-C3N4, ZnO, and Co3O4, and the heterogeneous phase for the composites. The synthesized ZnO and Co3O4 by using cellulose as a template show a rod-like morphology. The specific surface area of the catalytic samples increases due to the cellulose template. The measurements of the energy band gap of a g-C3N4-ZnO-Co3O4 composite showed red-shifted optical absorption to the visible range. The photoluminescence (PL) intensity decreases due to the formation of heterojunction. The PL quenching and EIS result shows that the reduction of the recombination rate and interfacial resistance result in charge carrier kinetic improvement in the catalyst. The photocatalytic performance in the degradation of MB dye of the GZC-3 composite was about 8.2-, 3.3-, and 2.5-fold more than that of the g-C3N4, g-C3N4-ZnO, and g-C3N4-Co3O4 samples. The Mott–Schottky plots of the flat band edge position of g-C3N4, ZnO, Co3O4, and Z-scheme g-C3N4-ZnO-Co3O4 photocatalysts may be created. Based on the stability experiment, GZC-3 shows greater photocatalytic activity after four recycling cycles. As a result, the GZC composite is environmentally friendly and efficient photocatalyst and has the potential to consider in the treatment of dye-contaminated wastewater. [ABSTRACT FROM AUTHOR]

In this article, density functional theory is used to explore the electronic structure, phonon, and magnetic properties of Zn(1−x)FexSe (for x = 0%, 6.25%, 12.5%, 25%, and 50%). The electronic structure, phonon properties, and magnetic properties of the systems were examined using the generalized gradient approximation (GGA) and with Hubbard correction (GGA + U), where U is a Hubbard parameter. The calculated lattice parameter is 5.65 Å, which is quite close to the experimental lattice parameter of ZnSe, 5.66 Å. In this study, the GGA+U provides a better bandgap approximation (Eg = 1.3708 eV) than the GGA (Eg = 1.229 eV), which is consistent with experimental results and values previously reported. According to our results, the iron-doped zinc selenide exhibits antiferromagnetic coupling for a percentage of substitution greater than 12.5%. In addition, for an iron substitution of 12.5% with the distance between dopant atoms exceeding 5.6364 Å, it tends to exhibit ferromagnetic properties. Therefore, the iron-doped zinc selenide manifests the dilute magnetic semiconductor and can be considered to enhance its applications in the field of spintronics and magneto-optical devices based on further experimental results. [ABSTRACT FROM AUTHOR]

In this work, the un-doped, Cu-doped, and (Ni, Cu) co-doped SnO2 nanoparticles (NPs) were synthesized using the sol–gel method with a fixed concentration of copper dopant while varying the nickel concentrations. The structural, optical and electrical properties, as well as the surface morphology, were investigated systematically by various characterization techniques. The X-ray diffraction (XRD) study confirmed that the prepared samples had a tetragonal rutile crystal structure for all single-doped/co-doped and un-doped SnO2 NPs. The XRD results further confirmed that the crystalline sizes varied from 16 to 10 nm with the concentrations of the dopants. The UV–Vis diffusion reflectance spectroscopy (DRS) analysis showed that the optical band gap was found to be decreased from 3.38 to 3.27 eV when the dopant concentrations were increased. The energy dispersive analysis of X-ray spectra (EDX) results confirmed the presence of the expected elements in the prepared samples. Three major photoluminescence (PL) emission peaks were observed in the visible region, with a small shift toward lower wavelengths with dopant and co-dopant concentrations. Chemical bonding and the position of the O–Sn–O bond at 600–660 cm−1 were confirmed by the Fourier transform infrared spectroscopy (FTIR) study. The activation energies and conduction mechanisms of the prepared samples were investigated using the Hall Effect measurement method. The I–V studies confirmed that the prepared samples had a good ohmic contact behavior and the resistivity decreased significantly for co-doped sample. [ABSTRACT FROM AUTHOR]