The starting point of the work is deceptively simple. Clam shells, composed largely of calcium carbonate, are converted through controlled thermal and chemical treatment into a honeycomb-structured porous activated carbon, which the researchers abbreviate CAC. This architecture is exactly what materials scientists prize in an electrode or catalyst support: an interconnected network of pores at multiple length scales that offers enormous internal surface area for ions to access, along with a conductive carbon scaffold that can anchor catalytically active particles. By sourcing the carbon from biowaste rather than fossil-derived precursors, the team also sidesteps one of the persistent criticisms of advanced energy materials, namely that their manufacture can carry a heavy environmental footprint of its own.

Onto this biological carbon scaffold the researchers deposited sphere-like particles of a cerium-doped lanthanum cobaltite, a perovskite oxide of the general formula LaCoO3 in which a small fraction of the lanthanum sites is occupied by cerium atoms. Perovskite oxides of this ABO3 family have attracted intense interest in recent years because their compositions can be tuned almost endlessly, allowing chemists to adjust their electronic structure, optical absorption and surface chemistry. Doping is the classic lever: substituting foreign cations into the crystal lattice distorts the structure, creates defects such as oxygen vacancies, and can dramatically improve charge transport and light harvesting. In this case, the cerium substitution modifies the cobaltite’s semiconductor characteristics in ways that make it a more effective visible-light photocatalyst and a more capable charge-storage material.

The synthesis itself was deliberately kept low-tech. The composite, designated CAC/LC:Ce, was prepared by a facile hydrothermal method, in which the precursor solution and the carbon support are heated together in a sealed vessel, allowing the perovskite spheres to nucleate and grow directly on the carbon surface. Hydrothermal processing is widely favored in green chemistry because it operates at modest temperatures, uses water as the reaction medium and avoids many of the toxic solvents and elaborate vacuum steps associated with other nanomaterial fabrication routes. The result is a one-pot marriage of biowaste-derived carbon and engineered oxide that could, in principle, be scaled without exotic equipment.

Characterization was correspondingly thorough. The team probed the crystal structure of all three materials with X-ray diffraction, examined their morphology with field-emission scanning electron microscopy and high-resolution transmission electron microscopy, and confirmed chemical composition and surface states using Fourier-transform infrared spectroscopy, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis and Brunauer-Emmett-Teller surface area measurements. Two electrochemical techniques added crucial mechanistic depth. Mott-Schottky analysis revealed the semiconductor type and band structure of the cerium-doped cobaltite and the composite, mapping out the energy levels that govern how photogenerated electrons and holes separate, while transient photocurrent measurements under intermittent illumination demonstrated how efficiently the materials shuttle light-excited charges before they recombine and waste the absorbed energy.

The environmental half of the story centers on bromophenol blue, a widely used phenolic dye that serves as a stand-in for the colored organic pollutants that textile and dyeing industries discharge into waterways. Under visible-light illumination, the three materials showed a clear performance hierarchy in dye removal percentage. The clam shell carbon alone discolored 75 percent of the dye, the cerium-doped cobaltite managed 86 percent, and the combined composite reached 98 percent. That near-complete removal reflects a synergy between the two components: the porous carbon adsorbs dye molecules onto its extensive surface, concentrating them near the perovskite particles, which then generate reactive oxygen species under light that chemically dismantle the adsorbed pollutants. Scavenger experiments, in which specific radical quenchers are added to identify which reactive species dominate, allowed the team to pin down the key actors in the degradation chemistry.

Just as important as the headline efficiency is durability. Many photocatalysts lose activity after a few cycles as active sites are blocked by intermediates or the material itself degrades. The CAC/LC:Ce composite retained a 95 percent dye removal value on its fourth consecutive run, a strong indication that the anchoring of the perovskite on the robust carbon framework protects the active phase. The researchers also used liquid chromatography-mass spectrometry to trace the intermediate species formed as the dye broke down, reconstructing a plausible degradation pathway rather than simply reporting that the color disappeared. That distinction matters, because a decolorized solution can still contain toxic fragments, and a responsible remediation technology must demonstrate that the end products are genuinely benign.

To address that concern directly, the team evaluated the treated water biologically. Phytotoxicity tests using fenugreek, Trigonella foenum-graecum, assessed whether the degraded dye solution would still harm seed germination and plant growth, while ecotoxicity screening in zebrafish probed effects on aquatic organisms. These assays are a relatively rare but welcome step in photocatalysis research, where many studies stop at the discoloration percentage. By checking that the remediated water is compatible with both plant and aquatic life, the authors provide evidence for the practical reuse potential of the treated effluent, which is the ultimate test of any water-treatment technology intended for real-world deployment.

The energy-storage half of the study is equally striking. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy were used to evaluate electrodes fabricated from each material. The specific capacitances came out at 240 farads per gram for the clam shell carbon, 381 farads per gram for the cerium-doped cobaltite, and 652 farads per gram for the composite, a value that places the hybrid among the more capable perovskite-carbon electrodes reported in the supercapacitor literature. The composite electrode also held on to 91 percent of its initial capacitance after 3000 charge-discharge cycles, showing that the faradaic reactions at the perovskite surface do not rapidly degrade the electrode. To test performance at the device level, the team assembled a two-electrode asymmetric supercapacitor cell using the plain clam shell carbon as the negative electrode and the composite as the positive electrode, a configuration that widens the operating voltage window and is the standard route toward practical energy and power densities.

Taken together, the study offers a template for what sustainable materials chemistry can look like when the circular economy is designed in from the first step rather than bolted on at the end. A waste stream from the seafood industry becomes a porous carbon; that carbon hosts a doped perovskite engineered for visible-light activity; the resulting composite simultaneously tackles dye pollution and grid-relevant energy storage; and the safety of the cleaned water is verified with living organisms rather than assumed. Challenges certainly remain before such materials leave the laboratory, including scaling hydrothermal synthesis, validating performance with real textile effluents rather than model dyes, and demonstrating device-level cycling over far more than 3000 cycles. But the underlying message is compelling: with thoughtful design, the same humble material can help solve two of the defining problems of the coming decades, dirty water and the need for affordable energy storage, using nothing more exotic than clam shells, cerium and sunlight.

Subject of Research: A clam shell-derived activated carbon supporting cerium-doped lanthanum cobaltite perovskite for photocatalytic dye degradation and supercapacitor energy storage

Article Title: Sustainable synthesis of La–Ce mixed cobaltite anchored on clam shell-derived porous activated carbon for electrochemical energy storage and environmental remediation

Article References: Sustainable synthesis of La–Ce mixed cobaltite anchored on clam shell-derived porous activated carbon for electrochemical energy storage and environmental remediation. (n.d.). https://doi.org/10.1007/s11581-026-07489-w

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07489-w

Keywords: clam shell activated carbon, perovskite, LaCoO3, cerium doping, photocatalysis, dye degradation, supercapacitor, asymmetric cell, biomass-derived carbon, water remediation, hydrothermal synthesis, specific capacitance

Spinel ferrites are magnetic oxides whose crystal structure, described by the general formula AB₂O₄, allows metal cations to occupy two distinct interstitial sites within a framework of oxygen atoms: tetrahedral A sites and octahedral B sites. This architectural flexibility is what makes the family so versatile. Nickel ferrite is an inverse spinel with moderate saturation magnetisation and strong super-exchange interactions between the two sublattices, while magnesium ferrite is a partially inverse spinel prized for its high electrical resistivity, low magnetic losses and thermal stability. Blending the two produces a material already attractive for high-frequency applications, and the non-magnetic character of magnesium ions improves biocompatibility, opening the door to biomedical uses.

The researchers synthesised their nanoparticles using the sol-gel auto-combustion technique, a low-cost route in which metal nitrates dissolved in deionised water are chelated by citric acid in a one-to-one molar ratio. Liquid ammonia adjusts the pH to around seven, and gentle heating at 80 to 90 degrees Celsius transforms the solution into a thick gel. Further heating triggers a self-propagating ignition reaction, releasing gases and leaving behind a porous, fluffy ash-like powder. After grinding and calcination at 900 degrees Celsius for five hours in air, the team obtained phase-pure ferrite samples across all five cerium concentrations.

X-ray diffraction confirmed that every composition crystallised in the cubic spinel structure belonging to the Fd-3m space group, with characteristic reflections from the (220), (311), (400), (422), (511) and (440) planes. The cerium-doped samples also showed weak secondary peaks from iron oxide and cerium dioxide, a signature of the limited solubility of large Ce³⁺ ions in the spinel lattice. The most telling evidence came from the (311) peak, which shifted steadily toward lower angles as cerium content increased. Because Ce³⁺ carries an ionic radius of 1.02 angstroms, substantially larger than the 0.67 angstroms of the Fe³⁺ ions it replaces at octahedral sites, each substitution stretches the lattice. The lattice constant grew from 8.331 to 8.533 angstroms, the unit cell volume expanded from 578.16 to 621.69 cubic angstroms, and lattice strain rose from 2.31 to 4.00 times ten to the minus three.

That same strain suppresses crystal growth. Crystallite sizes calculated with the Debye-Scherrer equation fell monotonically from 40.77 nanometres for the undoped sample to 24.29 nanometres at the highest cerium loading, while Williamson-Hall analysis, which separates size broadening from strain broadening, yielded consistently larger values and confirmed the accumulating microstrain. Field-emission scanning electron microscopy revealed quasi-cubic grains whose average size actually increased with doping, from 57 to 88 nanometres, indicating that each visible grain is an aggregate of many finer crystallites. Porosity dropped from roughly 4.9 percent to 2.5 percent at the highest substitution levels, and energy-dispersive X-ray spectroscopy verified the presence of nickel, magnesium, iron, cerium and oxygen without contaminants.

Optical measurements showed that cerium does more than distort the lattice; it rewires the electronic structure. Ultraviolet-visible spectroscopy revealed strong absorption across the 200 to 800 nanometre range, with the absorption edge shifting toward longer wavelengths as doping increased. Tauc analysis showed the direct band gap narrowing from about 2.2 electronvolts for the undoped ferrite to roughly 2.0 electronvolts at x equals 0.09. The team attributes this red shift to localised cerium 4f states near the conduction band, oxygen vacancies created by charge imbalance, and enhanced iron two-plus to iron three-plus charge-transfer transitions, all of which introduce intermediate energy levels that allow optical transitions at lower photon energies. Urbach tail states arising from lattice disorder extend this visible-light absorption further.

Photoluminescence spectra displayed intense blue emission centred at 408 and 430 nanometres, arising from defect-assisted recombination, oxygen-vacancy charge transfer and cerium 5d to 4f transitions. Emission intensity peaked at the x equals 0.05 composition, which the researchers identify as the optimum concentration of radiative defect centres, before declining at higher loadings through non-radiative concentration quenching. Chromaticity analysis placed all samples firmly in the blue region, with colour purity reaching 91.3 percent for the x equals 0.05 composition and dominant wavelengths near 463 nanometres, characteristics consistent with blue-emitting oxide phosphors for solid-state lighting and optoelectronic devices.

Electrical characterisation painted an equally coherent picture. The dielectric constant was high at low frequencies due to Maxwell-Wagner interfacial polarisation at resistive grain boundaries, then fell to a frequency-independent plateau governed by the grain interior, in line with Koops’ two-layer model. Dielectric loss tangent and alternating-current conductivity followed the classic patterns of hopping conduction between iron ions at octahedral sites, obeying Jonscher’s universal power law at high frequencies. Impedance spectroscopy showed depressed semicircular Nyquist plots characteristic of non-Debye relaxation, with semicircles growing larger as cerium content rose, meaning the dopant increases grain-boundary resistance and makes the material more resistive overall, a useful trait for high-frequency and shielding applications where eddy-current losses must be minimised.

Magnetically, all compositions displayed narrow hysteresis loops typical of soft ferrimagnets, but cerium substitution steadily enhanced the saturation magnetisation, magnetic moment, coercivity, magnetocrystalline anisotropy constant and anisotropy field, while reducing remanence and the squareness ratio below the 0.5 threshold that marks multidomain, soft magnetic behaviour. The team interprets the rising saturation magnetisation through the Yafet-Kittel model: cerium at octahedral sites strengthens A-B super-exchange interactions and reduces the canting angle of B-site spins, aligning the magnetic moments more collinearly and increasing the net moment per formula unit. Meanwhile, lattice strain, grain boundaries and cerium-induced distortions act as domain-wall pinning sites, raising coercivity and anisotropy.

Perhaps the most consequential result came from the antibacterial tests. Using the agar well diffusion method against Staphylococcus aureus and Escherichia coli, the composition Ni₀.₈Mg₀.₂Ce₀.₀₇Fe₁.₉₃O₄ emerged as the standout, producing inhibition zones of 10.2 plus or minus 0.5 millimetres against the Gram-positive S. aureus and 6.1 plus or minus 0.6 millimetres against the Gram-negative E. coli, the only sample active against both organisms. The undoped ferrite and the x equals 0.05 composition showed no activity at all. The researchers caution that diffusion effects in the assay mean the comparison with the streptomycin control, which produced zones of 7.9 and 12.0 millimetres respectively, should be interpreted carefully. The mechanism, they argue, lies in the defect chemistry: cerium substitution increases oxygen vacancies and surface defect sites that catalyse the generation of reactive oxygen species such as hydroxyl and superoxide radicals, which attack bacterial membranes, proteins and genetic material, while the coexisting iron and cerium redox couples facilitate the electron-transfer processes that sustain this oxidative assault. Taken together, the results position cerium-doped nickel-magnesium ferrites as a rare single-material platform spanning microwave components, electromagnetic interference shielding, blue-light optoelectronics and antimicrobial technology, all tuned by one substitution.

Subject of Research: Cerium-doped nickel-magnesium spinel ferrite nanoparticles synthesized by sol-gel auto-combustion for enhanced magnetic, optical, dielectric and antibacterial performance

Article Title: Enhanced magnetic, electrical, optical and antibacterial performance of Cerium doped Nickel-Magnesium ferrites prepared by sol gel method

Article References: Shruthi, M., Gadwala, N., Pradyutha, A., Sridhar, A., Balaganesh, D., & Prasad, M. (2026). Enhanced magnetic, electrical, optical and antibacterial performance of Cerium doped Nickel-Magnesium ferrites prepared by sol gel method. Results in Chemistry, 30, Article 103853. https://doi.org/10.1016/j.rechem.2026.103853

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103853

Keywords: spinel ferrites, cerium doping, nickel-magnesium ferrite, sol-gel auto-combustion, antibacterial nanoparticles, reactive oxygen species, photoluminescence, dielectric properties, soft ferrimagnetism, optical band gap, oxygen vacancies, nanomaterials