Pure and Ce-doped spinel CuFe2O4 photocatalysts for efficient rhodamine B degradation

Tailoring structural and optical properties of Cu(II)-induced MgAl2O4 nanoparticles and their response to toxic dyes under solar illumination

Worldwide environmental challenges pose critical problems with the growth of the global economy. Addressing these issues requires the development of an eco-friendly and sustainable catalyst for degrading organic dye pollutants. In this study, copper-doped magnesium aluminates (CuxMg1-xAl2O4) with x = 0.0-0.8 were synthesized using a citrate-based combustion route. The inclusion of Cu(II) significantly impacted the structural, microstructural, optical, and photocatalytic activity of the catalyst. Rietveld analysis of X-ray diffraction powder profiles revealed single-phase spinels crystallized in the face-centered cubic unit cell with Fd 3 ¯ m space group. Chemical states of the ions, surface morphology, and elemental investigation were analyzed by X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy, respectively. UV-visible and diffuse reflectance spectroscopies confirmed the reduction of the band gap due to Cu(II) doping, validated by first-principle investigations using the WIEN2k code. The catalyst with x = 0.8 showed higher photocatalytic efficacy (90% and 93%) for removing two azo organic dye pollutants, rhodamine B and methyl orange, respectively, within 120 min. Degradation kinetics followed a pseudo-first-order mechanism. The doped (0.8) sample was structurally and morphologically stable and reusable under visible irradiation, retaining performance after three runs. Scavenger studies confirmed hydroxyl and superoxide radicals' involvement in the degradation. This work presents an effective approach to enhancing CuxMg1-xAl2O4 catalysts' photodegradation performance, with potential applications in pharmaceuticals and wastewater remediation.

Tuning optical, magnetic, and electrical parameters of CuFe2O4 nanoparticles incorporated with GO and ZnO using a facile synthesis

Nano-ferrites, metal oxides, and carbon-based nanomaterials have been used frequently to enhance optical and magnetic prospects for latent applications. Copper ferrite/Graphene Oxide and Zinc Oxide (CuFe2O4/GO/ZnO) ternary nanocomposite synthesized by hydrothermal route showed dramatically good outcomes as the band gap energy value of synthesized nanocomposite approaches to 2.4 eV. Furthermore, the light absorbance of CuFe2O4 increases by adding ZnO and GO. The experimental data revealed the face-centered cubic structure (FCC) of pure spinal ferrite (CuFe2O4) nanoparticles even after adding ZnO and GO. The 2θ peak observed at 31.70° with (220) hkl planes indicates the successful addition of ZnO nanoparticles in CuFe2O4/GO nanocomposite. XRD graph, the absence of characteristic peaks of GO revealed the intercalation of CuFe2O4 nanoparticles with GO layers. In SEM images, agglomeration among CuFe2O4 nanoparticles is observed due to the magnetic interaction of nano-crystallite with a high surface-to-volume (S/V) ratio. VSM can be used to determine the magnetic properties of as-synthesized samples at moderate temperatures under 0-0.5 and ± 5 tesla. In CuFe2O4/GO/ZnO ternary nanocomposite, the saturation magnetization value reduces from 2.071 to 1.365 emu/g due to the addition of ZnO nanoparticles. The loops were narrowed showing a decrease in the coercive field with the addition of ZnO nanoparticles in CuFe2O4/GO ternary nanocomposite material. Moreover, the study of electrical properties of pure CuFe2O4 and CuFe2O4/GO/ZnO ternary nanocomposite revealed that the values of dielectric constant and tangent loss decrease at high frequencies owing to surface charge polarization and intrinsic dipole interactions. The study of the electrical properties of both pure CuFe2O4 and the CuFe2O4/GO/ZnO ternary nanocomposite reveals that the dielectric constant (ε') and tangent loss (tanδ) exhibit a decreasing trend as the frequency increases. This behavior is attributed to surface charge polarization and intrinsic dipole interactions. At lower frequencies, both samples display elevated values for these properties, which stabilize as the frequency increases beyond 2 MHz. Notably, high AC conductivity is observed in both samples, attributed to increased capacitance and resistance.

Investigation of the efficacy of Zn/Ce-CuO nanoparticles for enhanced photocatalytic, antibacterial, and antioxidant activities

The world is dealing with unprecedented environmental challenges, leading to a growing urgency to limit environmental damage. So, this study focuses on the synthesis of pure CuO, Zn, Ce, and Zn/Ce dual-doped CuO nanoparticles (NPs) using extract of Citrus limon leaves as reductant via simple co-precipitation method. The X-ray diffraction (XRD) characterization was employed to analyze structural characteristics of synthesized samples which confirm influence of Zn or Ce doping on crystallite size, dislocation density, and strain. The role of functional groups, changes in force constant, and bond length on addition of dopants was indicated by FTIR results. The SEM and TEM results showed variation in morphology from irregular to spherical. The zeta-potential and BET analysis confirmed surface potential as well as surface area characteristics. The change in energy gap values from 1.81 to 1.45 eV of Zn/Ce-doped CuO NPs computed from UV-vis analysis elevated its photocatalytic performance and reduced the chances of recombination of electron-hole pair due to presence of trapping levels between valence and conduction bands. The enhanced photo-degradation of Congo red (CR) and rhodamine B (RhB) with 91 and 94%, respectively, for Zn/Ce-doped CuO NPs was observed. The so-obtained samples have also exhibited good antibacterial and antioxidant activities.

Fabrication of CuFe2O4/Bi12O17Cl2 photocatalyst with intrinsic p-n junction for highly efficient bisphenol A degradation

The construction and application of novel highly efficient photocatalysts have been the focus in the field of environmental pollutant removal. In this work, a novel CuFe2O4/Bi12O17Cl2 photocatalysts were synthesized by simple hydrothermal and chemical precipitation method. The fabricated CuFe2O4/Bi12O17Cl2 composite exhibited much higher photocatalytic activity than pristine CuFe2O4 and Bi12O17Cl2 in the removal of bisphenol A (BPA) under visible-light illumination, which ascribed to the intrinsic p-n junction of CuFe2O4 and Bi12O17Cl2. The photocatalytic degradation rate of BPA on CuFe2O4/Bi12O17Cl2 with an optimized CuFe2O4 content (1.0 wt.%) reached 93.0% within 30 min. The capture experiments of active species confirmed that the hydroxyl radicals (•OH) and superoxide radicals (•O2-) played crucial roles in photocatalytic BPA degradation process. Furthermore, the possible degradation mechanism and pathways of BPA was proposed according to the detected intermediates in photocatalytic reaction process.

Binary Metal-Oxide Active Sites Derived from Cu-Doped MIL-88 with Enhanced Electroactivity for Nitrate Reduction

Nitrate-to-ammonia electrochemical conversion is important for decreasing water pollution and increasing the production of valuable ammonia. However, achieving high ammonium production without undesirable byproducts is difficult. Cu-doped MIL-88-derived bimetallic oxide catalysts with electrocatalytically active Fe-O-Cu bridges, which have high NO3- adsorption energy and facilitate N-intermediate hydrogenation, are developed for NH4+ production. Cu doping promotes hybridization between the O 2p of NO3- and Fe-Cu 3d, facilitating the adsorption and reduction of NO3- with a low Tafel slope (62.1 mV dec-1) and high ammonia yield (1698.8 μg·h-1·cm-2). The cathode efficiency is stable for seven cycles. Cu adjacent to Fe sites inhibits hydrogen evolution, promotes NO3- adsorption, and decreases the intermediate adsorption energy barrier. This study provides new opportunities for fabricating diverse binary metal oxides with new interfaces as efficient cathode materials for selective electroreduction.

Tunable sulphur doping on CuFe2O4 nanostructures for the selective elimination of organic dyes from water

In this work, sulphur doped copper ferrites (S-CuFe2O4) photocatalysts were successfully synthesized for the first time using the facile hydrothermal method. The as-synthesized photocatalysts were characterized through XRD, Raman, TGA, FT-IR, UV-Vis-DRS, SEM, EDX and PL techniques. The results revealed that doping with sulphur has been found to be a suitable alternative that causes strain in the lattices as anions replace the oxygen from the CuFe2O4 nanostructures. Due to sulphur dopants, photocatalysts are able to efficiently trap and transfer the photoinduced charges, which readily suppress charge recombination. A UV-Vis spectrophotometer was used to monitor the degradation of selective toxic organic dyes (RhB, CR, MO, and CV) in aqueous media. The dye degradation results provide evidence for the surprisingly superior performance of S-CuFe2O4 over pristine CuFe2O4. On the basis of its efficiencies, this work can be assigned as an excellent candidate for photocatalysis science.

CuCe-Ferrite/TiO2 Nanocomposite as an Efficient Magnetically Separable Photocatalyst for Dye Pollutants Decolorization

In this work, a magnetically separated photocatalyst with great efficiency CuCe-Ferrite/TiO2 composite was prepared and characterized by X-ray diffraction (XRD), UV–Vis spectrophotometry, Fourier transformer infra-red spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). Single-phase cubic spinel was formed by calcining the prepared sample at a temperature of 550 °C, according to the results. Different concentrations of reactive red 250 (RR250) dye photodegradation was evaluated using different doses of CuCe-ferrite/ TiO2 and TiO2 NPs. Higher efficiency of RR250 photodegradation up to 100% was obtained using CuCe-ferrite/ TiO2. The photodegradation efficiency was confirmed using chemical oxygen demand (COD) test of both treated and untreated samples. The oxidation process was mostly mediated by photogenerated .O2− according to scavenger test results. The catalyst possess higher photodegradation efficiency even after regeneration for ten times.

Graphical Abstract

Highly sensitive photoelectrochemical neuron specific enolase analysis based on cerium and silver Co-Doped Sb2WO6

A signal-enhanced photoelectrochemical immunoassay technique for detecting neuron specific enolase (NSE) was proposed. As a photoactive matrix, (Ce,Ag):Sb₂WO₆ was firstly investigated via doping Ce and Ag into Sb₂WO₆. It could be found that the presence of Ce and Ag not only had enormous variation on the morphology of Sb₂WO₆, but also showed excellent PEC behavior. In order to further improve the visible light utilization rate of (Ce,Ag):Sb₂WO₆, In₂S₃ was modified onto the surface of (Ce,Ag):Sb₂WO₆ to enhance visible light absorption. In addition, the CdS/PDA was served as a secondary antibody marker to further amplify signal. Especially, PDA as an electron donor could effectively remove photogenerated holes. Meanwhile, the good matching cascade band-edge levels between CdS and Sb₂WO₆ could promote photoelectron migration, improve the PEC response, and achieve sensitive detection of NSE. Under the selected excellent conditions, the photocurrent can linearly increase with the increase of NSE concentration in the operating range from 0.1 pg/mL to 50 ng/mL, and the limit of detection is 1.57 fg/mL. The constructed immunosensor also exhibits satisfactory stability, selectivity, and reproducibility, and it creates conditions for the detection of other biomolecules.