A simple, low-cost nanomaterial made from two abundant transition-metal oxides can both destroy one of the world’s most persistent antibiotic pollutants in sunlight and electrically detect it at trace concentrations, according to new research published in Catalysis Letters. The study, led by Jahnavi Hunasekatte Katamallappa and Rajendra Prasad Shivalingappa of Davangere University in India, describes a manganese oxide–cobalt oxide (Mn₂O₃–Co₃O₄) nanocomposite synthesized by an accessible sol–gel route that achieves 95 percent degradation of the antibiotic trimethoprim within 50 minutes under natural sunlight, while simultaneously serving as the active layer of an electrochemical sensor with a detection limit of 0.5 micromolar. The dual functionality is significant because water utilities and environmental agencies typically require two separate technologies—one to remove contaminants and another to measure them—and a single material that performs both jobs could simplify monitoring and remediation infrastructure considerably.
Trimethoprim is a widely prescribed antibiotic, usually administered in combination with sulfamethoxazole for urinary tract and respiratory infections, and it is a textbook example of an “emerging contaminant”: a compound that is not effectively removed by conventional wastewater treatment and therefore accumulates in rivers, lakes, and even drinking water sources. Because it is designed to suppress bacterial growth, its continuous presence in aquatic ecosystems exerts selective pressure on microbial communities, accelerating the evolution and dissemination of antibiotic-resistance genes—one of the most pressing public health threats of the century. Environmental surveys documented in the literature report trimethoprim in hospital effluents, municipal wastewater treatment plant discharges, and receiving surface waters worldwide, often at concentrations high enough to exert biological effects. Conventional biological treatment only partially transforms the molecule, sometimes generating transformation products of uncertain toxicity, which has driven intense interest in advanced oxidation processes that can mineralize the antibiotic completely rather than merely relocating it.
The core technical challenge in photocatalytic water purification lies in harnessing visible light efficiently. The archetypal photocatalyst, titanium dioxide, is chemically robust and inexpensive but possesses a wide band gap of roughly 3.2 electronvolts, meaning it absorbs only ultraviolet radiation—a small fraction of the solar spectrum. The Indian team’s Mn₂O₃–Co₃O₄ composite sidesteps this limitation. Optical measurements revealed a narrowed band gap of 2.1 electronvolts, allowing the material to absorb a substantial portion of visible light, including the abundant photons available in ordinary sunlight. This narrowing arises from the electronic structure of the two oxides: both manganese(III) oxide and cobalt(II,III) oxide are semiconducting transition-metal oxides with partially filled d-orbitals that create intermediate electronic states, and when coupled in a heterostructure, their band alignments promote efficient absorption and charge transfer. The researchers attribute the material’s outstanding performance specifically to this synergistic interaction between the two oxide phases, which facilitates rapid separation of photogenerated electron–hole pairs and enhances electron mobility across the interface.
The synthesis itself is deliberately unglamorous, which is part of its appeal. The team used a facile sol–gel method—a wet-chemical technique in which metal precursors are dissolved, gelled, and calcined to form the mixed oxide. Sol–gel processing offers fine control over composition and particle size at low cost, without the high temperatures, pressures, or exotic reagents demanded by hydrothermal or vapor-phase methods. Structural characterization by X-ray diffraction confirmed the coexistence of crystalline Mn₂O₃ and Co₃O₄ phases, while scanning electron microscopy and energy-dispersive X-ray analysis revealed a porous, heterostructured morphology with the expected elemental composition. Brunauer–Emmett–Teller surface area analysis documented the enhanced surface properties of the composite—critical, because photocatalysis and electrochemical sensing are both interfacial processes whose rates scale with accessible active surface area. Porosity also aids adsorption of trimethoprim molecules onto the catalyst surface, bringing them into intimate contact with reactive sites before degradation begins.
Photocatalytic performance was evaluated under natural sunlight irradiation, and the results were striking. Under optimized conditions—a solution pH of 5, a temperature of 35 degrees Celsius, and an initial trimethoprim concentration of 20 parts per million—the nanocomposite destroyed 95 percent of the antibiotic within 50 minutes. Kinetic analysis of the concentration-versus-time data indicated that the degradation follows pseudo-first-order reaction kinetics, a hallmark of heterogeneous photocatalysis in which the reaction rate is proportional to pollutant concentration while the catalyst surface is saturated with light-generated reactive species. To probe the mechanism, the researchers conducted radical scavenging experiments using isopropyl alcohol, benzoquinone, and ammonium oxalate—selective quenchers of hydroxyl radicals (•OH), superoxide radicals (•O₂⁻), and photogenerated holes, respectively. The mechanistic picture that emerges is familiar to photocatalysis researchers: sunlight excites electrons from the valence band to the conduction band of the composite, leaving holes behind. Dissolved oxygen captures conduction-band electrons to form superoxide radicals, while water or hydroxide ions react with holes to generate hydroxyl radicals. These reactive oxygen species then attack the trimethoprim molecule, progressively cleaving its aromatic rings and heteroatom-containing moieties until mineralization products are formed.
The second, equally consequential application is electrochemical detection. The same nanocomposite was immobilized on an electrode and tested for its ability to oxidize trimethoprim in phosphate buffer solution. Cyclic voltammetry established that the modified electrode exhibits excellent electrocatalytic activity toward the antibiotic, with a well-defined oxidation signal whose current increases systematically with trimethoprim concentration. Quantitative calibration using differential pulse voltammetry—a pulsed technique that suppresses background charging current and therefore improves sensitivity—demonstrated a wide linear detection range spanning 0.05 to 25 micromolar, a limit of detection of 0.5 micromolar, and a high sensitivity of 10 microamperes per micromolar per square centimeter. These figures of merit compare favorably with previously reported trimethoprim sensors, including those based on noble-metal nanoparticles, carbon fiber paper, and graphene oxide–zinc oxide quantum dot composites, yet the underlying material is composed of two earth-abundant, inexpensive oxides prepared in a single synthesis. The improved electrochemical response again reflects the synergy between the two oxide phases: efficient charge separation within the composite translates into faster heterogeneous electron transfer between the trimethoprim molecule and the electrode, amplifying the analytical signal.
What makes this work resonate beyond the laboratory is the elegance of its dual-purpose design. Environmental monitoring of pharmaceuticals currently depends on labor-intensive analytical techniques such as liquid chromatography coupled to mass spectrometry, which require expensive instrumentation, trained operators, and centralized facilities. Electrochemical sensors, by contrast, are compact, fast, inexpensive, and amenable to field deployment—and a sensor built from the same material that degrades the pollutant offers a compelling vision of integrated remediation systems in which treatment and verification happen side by side. A treatment plant or a decentralized rural water-treatment unit could, in principle, load sunlight-active composite onto a photo-reactor while equipping an electrode downstream with the same composite to continuously verify that antibiotic levels have fallen below safe thresholds. The low fabrication cost and reliance on freely available sunlight make the approach particularly attractive for low-resource settings where antibiotic contamination and monitoring gaps are most severe.
The findings also add to a growing body of evidence that carefully engineered heterojunctions between cheap metal oxides can rival more exotic and costly photocatalysts. Prior studies have explored Z-scheme and p–n heterojunction systems—such as Co₃O₄/BiOI for ibuprofen and trimethoprim degradation, g-C₃N₄/AgMoO₄ composites for antibiotic destruction, and Mn/Fe oxide-functionalized ceramic membranes for catalytic ozonation—but relatively few materials have been validated for both photocatalytic degradation and electrochemical sensing of the same target molecule. The Mn₂O₃–Co₃O₄ system demonstrates that the same interfacial charge-transfer physics that drives photocatalysis can be exploited for amperometric detection, unifying two branches of applied materials chemistry under one synthesis. The mechanistic understanding that superoxide and hydroxyl radicals are the dominant degrading species, confirmed through selective scavenger tests, provides a blueprint that other groups can use to rationalize and optimize related composite systems.
Important work remains before the technology can leave the bench. Real wastewater contains competing organic matter, suspended solids, and mixed pharmaceutical cocktails that can foul catalysts and interfere with electrochemical signals, and the study’s optimized conditions—moderately acidic pH and relatively warm temperatures—will need to be tested against the variable chemistry of actual effluents. Long-term catalyst stability, recyclability across repeated sunlight cycles, and the identity and toxicity of degradation intermediates are all questions that scale-up studies must answer. The authors, who also include Dhanyashree Savithree Vishwakumar of Davangere University, Jagadish Krishnegowda of Sarada Vilas College, University of Mysore, and Sucheta Mallikarjunaiah of Bangalore University, report no external funding for the work and state that all supporting data are contained within the article. Nonetheless, the combination of a 2.1-electronvolt band gap, 95 percent degradation in under an hour of sunlight, pseudo-first-order kinetics, and a sub-micromolar electrochemical detection limit establishes the Mn₂O₃–Co₃O₄ nanocomposite as one of the more versatile entries yet in the quest to tame antibiotic pollution—and a reminder that sometimes the most impactful materials science begins with the humblest of ingredients.
Subject of Research: A sol–gel synthesized Mn₂O₃–Co₃O₄ nanocomposite used for visible-light photocatalytic degradation and electrochemical detection of the antibiotic trimethoprim in water
Subject of Research: Chemistry
Article Title: Dual-Functional Mn₂O₃-Co₃O₄ Nanocomposite for Visible-Light Photocatalytic Degradation and Electrochemical Detection of Trimethoprim
Article References: Katamallappa, J. H., Krishnegowda, J., Vishwakumar, D. S., Mallikarjunaiah, S., & Shivalingappa, R. P. (2026). Dual-Functional Mn2O3-Co3O4 Nanocomposite for Visible-Light Photocatalytic Degradation and Electrochemical Detection of Trimethoprim. Catalysis Letters, 156(8), Article 238. https://doi.org/10.1007/s10562-026-05478-2
Image Credits: AI Generated
DOI: 10.1007/s10562-026-05478-2
Keywords: Mn₂O₃–Co₃O₄ nanocomposite, visible-light photocatalysis, trimethoprim detection, electrochemical sensor, photocatalytic degradation, antibiotic pollution, sol–gel synthesis, water remediation, reactive oxygen species, pseudo-first-order kinetics, limit of detection, environmental monitoring
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Bethany Barker. (September 6, 2026). Mn2O3-Co3O4 Nanocomposite Enables Visible-Light Degradation and Electrochemical Detection of Trimethoprim. Scienmag. https://scienmag.com/mn2o3-co3o4-nanocomposite-enables-visible-light-degradation-and-electrochemical-detection-of-trimethoprim/
Bethany Barker. “Mn2O3-Co3O4 Nanocomposite Enables Visible-Light Degradation and Electrochemical Detection of Trimethoprim.” Scienmag, 6 September 2026, https://scienmag.com/mn2o3-co3o4-nanocomposite-enables-visible-light-degradation-and-electrochemical-detection-of-trimethoprim/. Accessed 6 September 2026.
Bethany Barker. “Mn2O3-Co3O4 Nanocomposite Enables Visible-Light Degradation and Electrochemical Detection of Trimethoprim.” Scienmag. September 6, 2026. https://scienmag.com/mn2o3-co3o4-nanocomposite-enables-visible-light-degradation-and-electrochemical-detection-of-trimethoprim/
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Tags: dual-function water purificationelectrochemical detection of antibioticselectrochemical sensor for antibiotic detectionenvironmental monitoring of emerging contaminantsenvironmental pollutant degradationenvironmental remediation nanotechnologylow-cost nanomaterial synthesisMn2O3-Co3O4 nanomaterialsnanocomposite synthesisnanocomposite water treatmentNanomaterialpersistent pharmaceutical pollutantssol-gel synthesis methodsol-gel synthesis of transition metal oxidessustainable nanomaterialstrace antibiotic sensingtrace-level antibiotic monitoringtransition metal oxidestrimethoprim removalvisible light photocatalysiswastewater contaminant removalwastewater treatment
