Enhanced photocatalytic and antibacterial performance of LaMnCeO3/TiO2 composites modified with Ti3C2Tx MXene for efficient methyl red degradation

Nastaran Parsafard; Ali Riahi-Madvar

doi:10.1038/s41598-026-41059-4

. 2026 Mar 5;16:12322. doi: 10.1038/s41598-026-41059-4

Enhanced photocatalytic and antibacterial performance of LaMnCeO₃/TiO₂ composites modified with Ti₃C₂T_x MXene for efficient methyl red degradation

Nastaran Parsafard ^1,^✉, Ali Riahi-Madvar ²

PMCID: PMC13079796 PMID: 41786844

Abstract

In this study, LaMnCeO₃/TiO₂ nanocomposites modified with MXene were synthesized with varying La: Mn: Ce ratios to investigate their photocatalytic performance, charge-transfer behavior, and surface-related characteristics. TEM analysis revealed that MXene forms thin lamellar sheets, serving as a dispersive support for predominantly spherical or semi-spherical LaMnCeO₃/TiO₂ nanoparticles (sizes ranging from a few nanometers to ~ 100 nm). EDS mapping confirmed uniform distribution of La, Mn, Ce, Ti, O, and C throughout the composites. Structural and spectroscopic analyses demonstrated successful MXene incorporation, formation of mesoporous architectures with tunable surface areas, and compositional control over electronic transitions and chemical bonding. Photocatalytic studies indicated that LMC-112 achieved the highest dye degradation efficiency, while LMC-111 exhibited outstanding stability over five consecutive cycles. The photocatalytic performance was strongly dependent on pH, temperature, dye concentration, and reaction time. EIS, PL, and XPS analyses revealed efficient interfacial charge transfer, suppressed electron–hole recombination, and active surface defect states, which collectively enhanced reactive oxygen species (ROS) generation. Importantly, antibacterial assays revealed negligible microbial inhibition under the tested conditions, indicating that the material does not exhibit strong antibacterial activity. Overall, the LaMnCeO₃/TiO₂/MXene nanocomposites provide a stable and highly efficient platform for visible-light-driven wastewater treatment and environmental remediation, with performance tunable through compositional and structural optimization.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-41059-4.

Keywords: Photocatalysis, LaMnCeO₃/TiO₂/MXene, Methyl red, Visible light, Perovskite, RSM optimization

Subject terms: Chemistry, Environmental sciences, Materials science, Nanoscience and technology

Introduction

Industrial wastewater pollution caused by persistent organic dyes and microbial contaminants has become a critical environmental challenge, as conventional treatment methods such as coagulation, adsorption, and membrane filtration often fail to achieve complete degradation of complex pollutants¹. In this context, photocatalysis has emerged as an efficient and sustainable approach for wastewater remediation, offering effective degradation of organic pollutants and potential disinfection under light irradiation².

Recent advances have focused on the development of multifunctional photocatalytic nanocomposites that combine high degradation efficiency with antibacterial activity. Various systems, including activated carbon-supported TiO₂/ZnO³, MoS₂/SnS₂@AC⁴, TiO₂/ZnO/rGO⁵, ZnFe₂O₄/g-C₃N₄/rGO⁶, BiOCl/g-C₃N₄⁷, and g-C₃N₄/MnO₂ composites⁸, have demonstrated enhanced photocatalytic performance under visible light. However, excessive antibacterial activity is not always desirable in wastewater treatment, as it may disrupt beneficial microbial populations essential for biological processes. Therefore, the development of photocatalysts that efficiently generate reactive oxygen species (ROS) for pollutant degradation while maintaining biological neutrality has attracted increasing attention⁹.

Titanium dioxide (TiO₂) remains one of the most widely studied photocatalysts due to its stability and strong oxidative capability; nevertheless, its practical application is hindered by rapid charge carrier recombination and limited visible-light absorption. To overcome these drawbacks, strategies such as doping, defect engineering, and composite formation have been widely employed to tailor electronic structures, enhance charge separation, and extend light absorption into the visible region^10–12. Chemical activation approaches using agents such as NaBH₄¹³ or peroxymonosulfate¹⁴ have also been reported to enhance photocatalytic degradation through improved radical generation. Lanthanum-based perovskite oxides, such as LaMnCeO₃, offer tunable electronic structures, high thermal stability, and improved charge transport properties, making them promising candidates for visible-light-driven photocatalysis. Meanwhile, MXene (Ti₃C₂T_x) provides a highly conductive two-dimensional support with abundant surface active sites, facilitating efficient electron transfer and suppressing electron–hole recombination. Integrating TiO₂, LaMnCeO₃, and MXene into a ternary composite system enables the synergistic combination of semiconductor activity, perovskite charge modulation, and interfacial electron transport, thereby overcoming the intrinsic limitations of individual components^15–19.

In this study, LaMnCeO₃/TiO₂ composites supported on MXene were synthesized and systematically investigated. The effects of elemental composition on structural, optical, and electronic properties were examined, along with photocatalytic degradation of methyl red and antibacterial behavior. Special attention was given to charge transfer, ROS generation, and interfacial interactions to elucidate the structure–performance relationship of the proposed ternary photocatalyst^20–23.

Materials and methods

Catalyst preparation

A series of ternary composite catalysts comprising LaMnCeO₃, TiO₂, and Ti₃C₂T_x (MXene) were synthesized through a multi-step process. The precursors utilized in this study were sourced from commercial suppliers: hydrofluoric acid (HF, 38–40% purity, Merck), titanium (IV) oxide (TiO₂, ≥ 99% purity, 1 g, Merck), titanium aluminum carbide (Ti₃AlC₂, > 90% purity, particle size 40 μm, 1 g, Sigma-Aldrich), lanthanum nitrate hexahydrate (La(NO₃)₃.6H₂O, 99.9% purity, 1 g, Merck), manganese (II) nitrate tetrahydrate (Mn(NO₃)₂.4H₂O, 98% purity, 1 g, Merck), and cerium (III) nitrate hexahydrate (Ce(NO₃)₃.6H₂O, 99.9% purity, 1 g, Merck).

MXene (Ti₃C₂T_x) was prepared through selective etching of Ti₃AlC₂ precursor. In a Teflon-lined reactor, 20 mL of 6 M HF solution was added, followed by the slow addition of 1 g Ti₃AlC₂ powder. The reaction mixture was maintained at room temperature (20–25 °C) for 24 h (ideally under argon atmosphere). Subsequently, the resulting suspension was centrifuged and washed repeatedly with deionized water until achieving pH > 6. The final precipitate (MXene) was dried at ambient conditions.

The perovskite component (LaMnCeO₃) was synthesized via solid-state reaction method. Stoichiometric amounts (1 g each) of lanthanum nitrate hexahydrate, manganese nitrate tetrahydrate, and cerium nitrate hexahydrate were mixed thoroughly and calcined at 900 °C for 10 h under airflow conditions. The resulting powder was collected and utilized in subsequent composite formation.

Three distinct catalyst compositions were prepared by combining 1 g LaMnCeO₃, 1 g TiO₂, and 1 g MXene (Ti₃C₂T_x) powders in deionized water, followed by 30 min sonication treatment. The catalysts were synthesized with varying lanthanum-to-manganese-to-cerium molar ratios: La: Mn: Ce = 1:1:1, La: Mn: Ce = 1:2:1, and La: Mn: Ce = 1:1:2. These catalysts are designated as LMC-111, LMC-121, and LMC-112, respectively.

Characterization

The structural, morphological, optical, surface, and electrochemical properties of the synthesized catalysts were characterized using standard techniques, as briefly summarized as follows. X-ray diffraction (XRD) patterns were recorded using a Rigaku Ultima IV diffractometer with Cu K_α radiation (λ = 1.54056 Å) over a 2θ range of 10°–80° at a step size of 0.06°. Fourier transform infrared (FT-IR) spectra were collected using a Nicolet™ iS™ 10 spectrometer in the range of 400–4000 cm^− 1. UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) measurements were performed using an Evolution 300 spectrometer with BaSO₄ as the reference material in the wavelength range of 200–800 nm. Microstructural features were examined using a ZEISS EM10 transmission electron microscope (TEM) operated at 80–100 kV. Elemental composition and spatial distribution were analyzed using an EDAX-EDS (energy-dispersive X-ray spectroscopy) system coupled to SEM/TEM. Textural properties were determined using N₂ adsorption–desorption isotherms measured on a BELSORP Mini II analyzer. Samples were degassed at 623 K for 10 h prior to analysis. The BET and BJH models were used to calculate surface area and pore size distribution, respectively. Surface morphology was examined using a TESCAN MIRA2 FE-SEM (field emission scanning electron microscopy). Bulk elemental composition was analyzed using an XRF-8410 (X-ray fluorescence) spectrometer. Photoluminescence (PL) spectra were recorded at room temperature using a HORIBA Jobin–Yvon Fluorolog spectrofluorometer. Surface chemical states were analyzed using an X-ray photoelectron spectroscopy (XPS) (Bes Tek, Germany) with Al K_α radiation. Binding energies were calibrated to the C 1 s peak at 284.8 eV. The measurements of electrochemical impedance spectroscopy (EIS) were carried out in a three-electrode configuration using a potentiostat/galvanostat in 0.1 M Na₂SO₄ electrolyte over a frequency range of 100 kHz to 0.01 Hz.

Evaluating photocatalytic activity

The photocatalytic performance of the synthesized LaMnCeO₃/TiO₂/MXene nanocomposites was evaluated based on their ability to degrade Methyl Red (MR) dye under visible light irradiation. This assessment was conducted to determine the efficiency of the photocatalysts. For the photocatalytic experiments, a 10 ppm aqueous solution of Methyl Red was prepared. Then, 0.25 g of each nanocomposite catalyst was added to 60 mL of the MR solution. The mixture was stirred in the dark for 60 min to establish adsorption–desorption equilibrium between the catalyst surface and the dye molecules. The photocatalytic reactor consisted of a fully enclosed chamber equipped with a 300 W Xenon lamp to provide visible light irradiation, a fan for temperature control, a magnetic stirrer, and a double-walled quartz cell connected to a circulating water bath to maintain constant temperature inside the reactor. After the dark adsorption period, the suspension was exposed to visible light irradiation, and the reaction progress was monitored at 5 min intervals. To investigate the effects of different conditions on photocatalytic activity, experiments were conducted at three different pH values (3–11), temperatures (25–40 °C), and initial dye concentrations (5–15 ppm) for 35 min.

To evaluate the reaction progress, samples were periodically withdrawn and centrifuged to separate the catalyst particles. The residual concentration of MR in the supernatant was analyzed using a UV-Vis spectrophotometer (Evolution 300 model). The photocatalytic activity was quantified by calculating the photodegradation efficiency (PDE) of MR using the following formula:

Where C₀ represents the initial concentration of MR and C_t denotes the concentration of MR after t min of irradiation.

Optimization using response surface methodology (RSM)

The optimization of the photocatalytic decolorization of MR was conducted using Response Surface Methodology (RSM) based on a Central Composite Design (CCD). The experiments focused exclusively on the most efficient photocatalyst, LMC-111. Four independent variables were selected for investigation: reaction temperature (25, 30, 35, and 40 °C), initial pH (3, 7, and 11), initial dye concentration (5, 10, and 15 ppm), and reaction time (5 to 35 min at 5-minute intervals). A total of 30 experimental runs were designed and conducted using Design Expert software (version 11), which enabled the evaluation of linear, quadratic, and interaction effects of these variables on the photocatalytic decolorization efficiency (PDE). The experimental data were fitted to a second-order polynomial model, and the significance of the model terms was assessed using analysis of variance (ANOVA). The resulting surface plots and model predictions revealed the optimal conditions for maximizing MR degradation. This approach not only facilitated a deeper understanding of how the operational parameters influence the photocatalytic process but also minimized the number of required experiments, offering an efficient and statistically robust framework for process optimization.

Catalyst stability test

To evaluate the stability of the LMC-111 nanocatalyst, photocatalytic degradation experiments of MR were conducted under the optimal conditions determined by the RSM over five consecutive cycles. In each cycle, 0.25 g of the catalyst was dispersed in the dye solution and exposed to visible light. After the designated reaction time, samples were collected, and the photocatalytic degradation efficiency (PDE) was calculated using UV-Vis spectroscopy by monitoring the decrease in absorbance at the maximum wavelength. At the end of each cycle, the catalyst was recovered by centrifugation, thoroughly washed with distilled water and ethanol to remove residual dye and by-products, then dried at 60 °C for 12 h in an oven. The dried catalyst was reused in the next cycle without any further reactivation. This process was repeated for five cycles, and the PDE was measured after each run to monitor changes in photocatalytic performance over repeated uses.

Evaluation of antibacterial properties

The antibacterial efficacy of the LaMnCeO₃/TiO₂/MXene (Ti₃C₂T_x) nanocomposite was systematically evaluated against two representative bacterial strains: Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Antibacterial assessments were conducted using both the disk diffusion assay and minimum inhibitory concentration (MIC) determination in liquid culture, employing LB medium as the growth substrate.

Preparation of culture media

Liquid LB medium was prepared by dissolving 1 g NaCl, 0.5 g yeast extract, and 1 g tryptone in 100 mL deionized water. The medium was sterilized by autoclaving at 121 °C for 15 min. For solid media, 1.5 g agar was incorporated into the LB formulation prior to sterilization. The molten agar medium was dispensed into sterile petri dishes (8 cm diameter) and allowed to solidify under aseptic conditions.

Nanocomposite suspension preparation

An 8 mg/mL stock suspension of the nanocomposite was prepared in dimethyl sulfoxide (DMSO). Serial two-fold dilutions (1/2, 1/4, 1/8, 1/16) were subsequently prepared for testing.

Disk diffusion assay

Bacterial inocula were adjusted to 0.5 McFarland turbidity standard (~ 1.5 × 10⁸ CFU/mL). Sterile LB agar plates were uniformly inoculated with the bacterial suspensions. Sterile paper disks (6 mm diameter) impregnated with 30 µL of each nanocomposite dilution were placed onto the agar surface. Disks containing DMSO and gentamicin served as negative and positive controls, respectively. Plates were incubated at 37 °C for 18 h under two conditions: dark and visible light exposure (150 W). Antibacterial activity was quantified by measuring the diameter of the inhibition zones around each disk.

Minimum inhibitory concentration (MIC) and growth inhibition

For MIC determination, 3 mL aliquots of sterile LB medium in 50 mL Falcon tubes were supplemented with varying nanocomposite dilutions. Subsequently, 10 µL of bacterial suspension (~ 10⁶ CFU/mL) was added to each tube. Samples were incubated at 37 °C with agitation at 120 rpm for 18 h. Bacterial growth was monitored by measuring optical density at 600 nm (OD600). Growth inhibition percentage (GI%) was calculated as follows:

This quantitative approach allowed evaluation of the nanocomposite’s bacteriostatic effects under controlled experimental conditions.

Reactive species scavenging test

To investigate the contribution of reactive species in the photocatalytic process, radical scavenging experiments were performed. First, 0.001 M stock solutions of each scavenger were prepared (isopropanol for •OH, benzoquinone for •O₂⁻, and ammonium oxalate for h⁺). A 10 ppm solution of the model dye, Methyl Red, was prepared under optimal experimental conditions (pH 3 and 25 °C). The test solutions were then prepared by mixing the dye solution and each scavenger solution in a 1:1 volume ratio.

The photocatalytic degradation experiments were carried out under the same conditions as the standard photocatalytic tests, with periodic sampling to monitor the dye concentration over time. The degradation efficiency in the presence of each scavenger was compared to that of the control experiment without scavengers. A significant decrease in degradation efficiency in the presence of a specific scavenger indicates the dominant role of the corresponding reactive species in the photocatalytic process. This approach allows the identification of the main oxidative species responsible for dye degradation and provides insights into the reaction pathways.

Results and discussion

Characterization of the synthesized catalysts

X-ray diffraction (XRD) patterns of the LaMnCeO₃/TiO₂/MXene nanocomposite are presented in Fig. 1. The diffraction results confirm the successful formation of a crystalline ternary composite consisting of anatase TiO₂, LaMnCeO₃ perovskite, and Ti₃C₂T_x MXene phases.

The dominant diffraction peaks correspond to anatase TiO₂ (ICDD #00–004-0477), indicating that TiO₂ is the primary crystalline phase in the composite, consistent with previous reports^24,25.

Characteristic low-angle reflections associated with the (002) and (004) planes of Ti₃C₂T_x MXene confirm the retention of the layered MXene structure after composite formation (Fig. 1 and Fig. S1), while additional reflections related to TiC and TiO₂ phases further support the structural integrity of the MXene component. The presence of LaMnCeO₃ is evidenced by distinct perovskite-related diffraction peaks, which are consistent with cubic LaMnO₃, CeO₂, and La₂O₃ phases (ICDD #01–075-0440, #00–034-0394, and #01–074-1144), confirming successful incorporation of the perovskite phase into the composite.

The average crystallite size was estimated using the Scherrer equation (Eq. 3)²⁴ and was found to be in the range of approximately 19–25 nm, indicating the nanoscale nature of the synthesized materials. The low standard deviation (± 2.6 nm) indicates excellent particle size uniformity.

where D represents the average grain size (nm), K is the Scherer constant (typically 0.9), λ denotes the X-ray wavelength (Cu K_α = 0.15406 nm), β represents the peak full width at half maximum and θ is the Bragg angle.

The relatively sharp diffraction peaks and narrow crystallite size distribution suggest good crystallinity and uniform grain growth. Overall, the XRD analysis confirms the successful integration of TiO₂, LaMnCeO₃, and MXene into a structurally well-defined ternary nanocomposite, which is expected to be beneficial for enhanced photocatalytic performance.

The FT-IR spectra of the LaMnCeO₃/TiO₂/MXene nanocomposite (Fig. 2) confirm the successful formation of the composite and the presence of characteristic metal–oxygen bonds and surface functional groups. The absorption bands observed below 500 cm^− 1 are attributed to Ti–O and Mn–O stretching vibrations, which are characteristic of TiO₂ and perovskite-type La-based mixed metal oxides, respectively^26–28. These low-frequency vibrations are commonly reported for lattice metal–oxygen modes in oxide-based photocatalysts. The broad absorption features in the range of 500–800 cm^− 1 can be assigned to Ti–O–Ti and Mn–O–Mn bridging vibrations, indicating the formation of interconnected oxide frameworks within the composite structure^24,29,30. The broad band extending from approximately 1000 to 3600 cm^− 1 is associated with O–H stretching vibrations of surface hydroxyl groups and physically adsorbed water molecules³¹. The presence of surface hydroxyl groups is particularly important for photocatalytic applications, as they serve as active sites for the generation of ROS under light irradiation³². The absence of additional impurity-related bands indicates the chemical purity of the synthesized nanocomposite and confirms the effective integration of LaMnCeO₃, TiO₂, and MXene components, consistent with previously reported oxide–MXene composite systems³³.

The UV-Vis DRS spectra of LaMnCeO₃/TiO₂ based on MXene (Fig. 3a) reveal several distinct electronic transitions occurring within the material structure. It is noted that the reflectance data were first converted into absorption coefficients using the Kubelka–Munk function^30,34, and the optical band gap energies were subsequently estimated using the Tauc method.

These transitions include O(2p) → Mn(3d) in the range of 200–250 nm, O(2p) → Ce(4f) in the range of 250–300 nm, and Mn(3d) → Ce(4f) in the range of 300–400 nm.

The O(2p) → Mn(3d) transition, which produces the strongest peak in the 200–250 nm range, arises from electron transfer from oxygen atom p-orbitals to manganese atom d-orbitals. This transition exhibits higher intensity in LMC-121 (La: Mn: Ce ratio of 1:2:1), demonstrating the positive effect of increased manganese content. The O(2p) → Ce(4f) transition observed in the 250–300 nm range stems from electron transfer from oxygen atom p-orbitals to cerium atom f-orbitals. Enhanced intensity is noted in LMC-112 (La: Mn: Ce ratio of 1:1:2), indicating the beneficial impact of elevated cerium content. The Mn(3d) → Ce(4f) transition, visible in the 300–400 nm range, results from electron transfer from manganese atom d-orbitals to cerium atom f-orbitals. This transition appears stronger in samples with higher cerium ratios. Different elemental ratios in the LaMnCeO₃ structure significantly influence these transitions. Increased manganese content in LMC-121 strengthens the O(2p) → Mn(3d) transition, while enhanced cerium content in LMC-112 intensifies both the O(2p) → Ce(4f) and Mn(3d) → Ce(4f) transitions. Equal elemental ratios in LMC-111 result in the lowest transition intensity. These absorption patterns demonstrate that the electronic structure and optical properties of these materials are strongly influenced by elemental ratios, suggesting that optical and possibly catalytic properties can be optimized through ratio modification^30,34.

The UV-Vis spectroscopy calculations are described by the following equations:

Conversion of wavelength to energy:

Where h = Planck constant (6.626 × 10^− 34 J·s), c = Speed of light in vacuum (3 × 10⁸ m s^− 1), and λ = Wavelength (nm).

For conversion to electron volts:

Band gap energy (E_g) from cutoff wavelength (λ_g):

Absorbance (A) from reflectance (%R):

Absorption coefficient (α) from absorbance (A) and sample thickness (d):

Based on these calculations (Tauc plots), band gap energies for LMC-111 (Fig. 3b), LMC-121 (Fig. 3c), and LMC-112 (Fig. 3d) are 2.9, 3.0, and 2.4 eV, respectively.

The FESEM image (Fig. 4) of the LaMnCeO₃/TiO₂/MXene nanocomposite reveal distinctive spherical structures formed on the TiO₂ substrate. These morphological features were investigated across three different lanthanum, manganese, and cerium ratios (La: Mn: Ce) of 1:1:1, 1:2:1, and 1:1:2.

The 1:1:1 ratio specimen exhibits relatively uniform distribution of spherical particles with approximately similar dimensions, indicating good equilibrium in elemental composition. This regular distribution suggests proper adhesion of particles to the TiO₂ surface. Upon increasing manganese concentration in the 1:2:1 ratio, notable morphological modifications are observed. Particle sizes become larger and their distribution becomes less uniform compared to the previous sample. These changes indicate that increased manganese concentration directly influences the particle growth mechanism. Further morphological variations are evident in the 1:1:2 ratio sample, where cerium concentration is elevated. The crystal growth pattern differs, potentially leading to secondary phase formation. These structural modifications could significantly affect the physical and chemical properties of the nanocomposite. These findings suggest that the 1:1:1 ratio demonstrates superior structural stability, though varying elemental ratios can be beneficial for achieving specific desired properties in various applications such as photo catalysts and gas sensors.

TEM (Fig. 5) images reveal that the Ti₃C₂T_x substrate exhibits a thin, lamellar morphology, serving as a support platform for nanoparticle dispersion. The LaMnCeO₃/TiO₂ particles are primarily spherical to semi-spherical and are distributed over the MXene sheets with limited aggregation. At the 50 nm scale, the nanoparticles appear small (ranging from a few to several tens of nanometers) and well-dispersed, which is consistent with the role of MXene as an effective dispersing and anchoring substrate.

At the 100 nm scale, particularly near the edges of the micrographs, several larger particles (~ 100 nm) with well-defined edges and corners are observed. These faceted structures may have two possible origins: (i) agglomeration or sintering of smaller nanoparticles during calcination or drying, or (ii) locally folded or multilayered MXene regions that appear as thicker, high-contrast, angular fragments in TEM images. The presence of non-spherical, faceted nanoparticles indicates directionally controlled crystal growth or partial crystalline coalescence, suggesting the formation of larger crystalline domains (grain growth) for LaMnCeO₃ or TiO₂ in certain regions.

The EDS elemental maps (Fig. 6) confirm the homogeneous distribution of La, Mn, Ce, Ti, and O throughout the LaMnCeO₃/TiO₂/MXene nanocomposite. Lanthanum, manganese, and cerium signals correspond to the perovskite LaMnCeO₃ phase, while titanium and oxygen signals indicate the presence of TiO₂ and the Ti₃C₂T_x MXene substrate. The uniform dispersion of these elements on the MXene sheets supports the role of the 2D MXene as a substrate that prevents nanoparticle agglomeration and promotes effective exposure of active sites for photocatalytic reactions. No significant elemental segregation is observed, indicating successful integration of the ternary components.

The EDS analysis of the LaMnCeO₃/TiO₂/MXene nanocomposite (Fig. 7) confirms the presence of all expected elements: Ti, O, Mn, La, Ce, and C. Titanium and oxygen dominate the sample (Ti ~ 62 wt%, O ~ 46 wt%), corresponding primarily to the TiO₂ phase and MXene substrate. Lanthanum, cerium, and manganese are detected in smaller but significant amounts (La ~ 5.7 wt%, Ce ~ 5.9 wt%, Mn ~ 4.3 wt%), confirming the formation of the LaMnCeO₃ perovskite phase. Carbon is attributed to the MXene support. The quantitative results indicate a relatively uniform distribution of the elements, supporting the homogeneous dispersion of perovskite particles on the MXene sheets. No unexpected elements were observed, suggesting successful synthesis and phase purity. These findings are consistent with the TEM and mapping results.

The XPS survey spectrum of the LaMnCeO₃/TiO₂/MXene sample (Fig. S2a), calibrated to the C 1 s reference at 284.8 eV, and clearly confirms the presence of all major elements constituting the catalyst. Distinct photoelectron regions corresponding to La, Mn, Ce, Ti, O, and C verify the successful synthesis of the multicomponent composite. In the low-binding-energy region (≈ 80–100 eV), the appearance of Ti 3p and Ti 3 s peaks indicates the presence of TiO₂. The characteristic Ti 2p doublet at ≈ 455–465 eV, assigned to Ti⁴⁺, further confirms that TiO₂ remains in its stable oxidized state. Mn-related peaks at 630–655 eV, together with the Ce 3 d features at 880–920 eV, demonstrate the incorporation of Mn and Ce into the mixed-oxide perovskite network. The multipeak structure of Ce 3 d, containing Ce³⁺/Ce⁴⁺ components, reflects the presence of oxygen vacancies and oxygen-storage capability, which are central to catalytic performance. The O 1 s main peak at 529–533 eV consists of two components attributed to lattice oxygen and surface-adsorbed oxygen, the latter typically associated with oxygen vacancies and reactive surface sites. The C 1 s signal at 284.8 eV, used for calibration, arises from both surface adventitious carbon and the MXene substrate, which is known to contain C–Ti and C–C surface terminations. Overall, the survey spectrum confirms the expected elemental composition and agrees with TEM/EDS results, supporting the successful immobilization of LaMnCeO₃/TiO₂ on MXene.

The valence-band spectrum (0–40 eV, Fig. S2b) reveals electronic states characteristic of both oxide and MXene components. The feature at 6.31 eV corresponds to O 2p bonding states, commonly observed in TiO₂, MnO_x, LaMnO₃, and CeO₂³¹. The peak at 18.47 eV is assigned to C 2 s states of Ti–C layers in Ti₃C₂T_x MXene³⁵. Two closely spaced peaks at 22.30 and 22.45 eV arise from O 2 s states overlapping with Ce 5p, consistent with reported values for oxygen-containing Ce-based oxides³⁶. These results confirm the coexistence of oxide (O 2p, O 2 s), MXene (C 2 s), and Ce-derived (Ce 5p) states.

The medium-energy region (30–70 eV, Fig. S2c) displays several shallow-core levels. The peak at 37.71 eV corresponds to Ti 3p, with possible minor overlap from La 5s/Ce 5s. Peaks at 50.35 and 53.51 eV are attributed to the Mn 3p multiplet, indicative of mixed Mn oxidation states (Mn³⁺/Mn⁴⁺). The feature at 62.76 eV is assigned mainly to Ti 3 s, with potential contributions from plasmon-loss/Auger processes. These signals further confirm the coexistence of Ti- and Mn-containing oxides within the composite structure.

The 100–130 eV region (Fig. S2)) contains La and Ce shallow-core states. The peaks at 102.03, 104.38, and 107.20 eV correspond to the La 4 d multiplet, consistent with La³⁺ in an oxide environment³⁵. The peak at 123.40 eV matches Ce 4 d, typically observed in Ce-containing oxides.

The C 1 s spectrum (Fig. S2e) shows two components at 285.18 eV and 288.09 eV. The former corresponds to adventitious C–C/C–H species, whereas the latter indicates oxidized carbon groups (O–C = O) or surface carbonates, consistent with standard C 1 s assignments³⁵.

The Ti 2p spectrum (Fig. S2f) contains peaks at 459.19 and 465.31 eV, matching Ti 2p_3/2 and Ti 2p_1/2 of Ti⁴⁺ in TiO₂³⁷. The weaker feature at 473.00 eV represents the characteristic Ti⁴⁺ satellite²⁷.

The O 1 s spectrum (Fig. S2g) consists of lattice oxygen at 530.17 eV and surface hydroxyl/adsorbed oxygen species at 532.07 eV, consistent with oxygen-deficient or hydroxylated oxide surfaces^28,36. The feature at 520.34 eV is attributed to an Auger or energy-loss artifact rather than an O 1 s component.

The Mn 2p region (Fig. S2h) shows Mn 2p_3/2 and Mn 2p_1/2 at 642.29 and 653.40 eV, with a spin-orbit splitting of ≈ 11.1 eV. These values correspond to mixed Mn³⁺/Mn⁴⁺ states. The peak at 656.25 eV is assigned to a Mn satellite, associated with multiplet and charge-transfer transitions.

Finally, the La 3 d spectrum (Fig. S2i) includes La 3d_5/2 and La 3d_3/2 at 834.55 and 851.66 eV, along with their corresponding satellites at 838.19 and 855.10 eV, characteristic of La³⁺ in oxide matrices. The Ce 3 d spectrum (Fig. S2j) displays components characteristic of mixed Ce³⁺/Ce⁴⁺ multiplet features (882.81, 888.22, 897.45, 900.47 eV), indicating the coexistence of both oxidation states and the presence of oxygen vacancies relevant to catalytic activity.

The EIS analysis of the LaMnCeO₃/TiO₂/MXene ternary composite provides detailed insight into the charge-transfer dynamics and interfacial properties of the material. The Nyquist plots (Fig. S3a) exhibit semicircular behavior at high frequencies followed by a linear tail at low frequencies. The semicircle corresponds to the charge-transfer resistance (R_ct) and double-layer capacitance (C_dl) at the catalyst/electrolyte interface. The relatively small semicircle radius indicates low charge-transfer resistance, suggesting efficient interfacial electron transport and rapid separation of photo-generated electron–hole pairs. The Bode plots (Fig. S3b&c) show a sigmoidal profile with a minimum at approximately 10 kHz, representing the characteristic frequency at which maximum capacitive response and optimal charge separation occur. At frequencies above and below this point, impedance increases, reflecting less efficient charge transport. The overall impedance behavior suggests that the composite possesses enhanced electron mobility, reduced recombination, and effective utilization of photo-generated charges. Equivalent circuit modeling (R_s in series with R_ct parallel to a CPE) indicates non-ideal capacitive behavior, consistent with surface heterogeneity and defect-mediated charge storage. These EIS features collectively demonstrate that the LaMnCeO₃/TiO₂/MXene composite is electronically well-coupled and capable of efficient charge transfer, a prerequisite for high photocatalytic performance.

Figure 8 shows the PL spectra of the LaMnCeO₃/TiO₂/MXene catalyst recorded at excitation wavelengths of 365 and 420 nm with two slit settings (20–20 nm and 10–10 nm). A clear dependence of PL behavior on excitation energy is observed. Under 365 nm excitation, the samples exhibit higher PL intensity with a sharper band-edge emission, indicating stronger radiative recombination of photo-generated electron–hole pairs. In contrast, excitation at 420 nm leads to a notable reduction in PL intensity, a red-shifted emission maximum, and broader spectral features. These changes suggest that non-radiative pathways dominate at lower excitation energies, reflecting more efficient charge-carrier separation and migration through defect-mediated or interfacial states rather than direct recombination. Differences between the 20–20 nm and 10–10 nm slit measurements confirm that the intrinsic PL response is broad and includes multiple relaxation channels, with narrower slits producing slightly wider emission envelopes, consistent with carrier redistribution among trap states. Photoluminescence analysis provides crucial insight into the recombination behavior of electron–hole pairs in photocatalytic materials. Lower PL intensity generally indicates suppressed radiative recombination and enhanced charge separation, which are critical for improving photocatalytic efficiency. Accordingly, the quenched PL intensity observed under 420 nm excitation aligns well with the EIS-inferred lower charge-transfer resistance and the XPS-identified surface states, supporting more effective electron extraction and reduced electron–hole recombination, thereby contributing to the improved photocatalytic performance of the catalyst².

To improve clarity in Fig. 8, all PL spectra are now explicitly labeled according to excitation wavelength and slit width. The emission range was carefully selected to minimize excitation-related reflection and scattering artifacts, particularly those associated with the excitation wavelength (e.g., 365 nm) and its second-order harmonic. Therefore, the discussion focuses on intrinsic emission features that reliably reflect charge-carrier recombination and defect-mediated relaxation processes.

Figure 9a presents the nitrogen adsorption-desorption isotherms for the LaMnCeO₃/TiO₂/MXene catalyst with a La: Mn: Ce ratio of 1:2:1. The calculated BET surface area of approximately 18.07 m²g^− 1 indicates favorable surface characteristics. Additional key parameters obtained via BET analysis include a monolayer volume (V_m) of 4.15 cm³ (STP) g^− 1 and BET constant (c) of 127.13. The elevated c value in the BET equation reflects strong nitrogen adsorption affinity toward the catalyst surface. Higher surface area and suitable mesoporosity enhance adsorption of reactant molecules and facilitate mass transfer, providing better access to active sites and thus improving photocatalytic performance.

Fig. 9 — (a) BET isotherm and (b) BJH plot for LaMnCeO₃/TiO₂/MXene catalyst.

The nitrogen adsorption-desorption curve exhibits Type IV characteristics, indicative of mesoporous structure presence. The isotherm comprises two primary regions. Gradual volume increase in the initial region corresponding to monolayer adsorption, followed by steeper volume increase indicating multilayer adsorption onset. The prominent hysteresis loop in the curve demonstrates characteristic mesoporous behavior. Maximum adsorption occurs at p/p₀ = 0.98, reaching 0.211 cm³g^− 1, suggesting good adsorption capacity. Total pore volume calculated via BJH method equals 0.218 cm³g^− 1, indicating substantial internal space beneficial for catalytic reactions. BJH analysis reveals suitable pore size distribution favorable for photocatalytic reactions, with measured pore diameter of 46.696 nm (Fig. 9 b).

The experimental results for three different ratios of LaMnCeO₃/TiO₂/Mxene catalyst show distinct patterns in physical properties. This comprehensive comparison includes ratios of 1:1:1, 1:2:1, and 1:1:2, each exhibiting unique structural characteristics. The following table summarizes the measured physical parameters for all three ratios. For comparison, the BET surface area, monolayer volume, total pore volume, BET constant, and average pore diameter were also measured for the pristine (pure) materials LaMnCeO₃, TiO₂ anatase, and Ti₃C₂T_x MXene. The results are summarized in Table 1, showing that the composite catalysts exhibit increased surface area and pore volume compared to the individual components. This enhancement reflects the synergistic effect of combining the three materials, leading to improved mesoporosity and surface characteristics beneficial for photocatalytic reactions.

Table 1.

Textural data obtained from N₂ adsorption–desorption isotherms.

Property	LaMnCeO₃ pristine	TiO₂ anatase	Ti₃C₂T_x MXene	LMC-111	LMC-121	LMC-112
Surface area (m²g^− 1)	7.12	12.50	16.85	14.06	18.07	21.24
Monolayer volume (V_m) (cm³g^− 1)	1.65	2.45	3.20	3.80	4.15	4.81
BET constant (c)	58.30	102.70	134.50	90.24	127.13	140.16
Total pore volume (cm³g^− 1)	0.072	0.098	0.145	0.185	0.218	0.238
Average pore diameter (nm)	40.310	31.360	27.120	48.230	46.696	44.146

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For the LMC-111 catalyst, surface area and pore volume are reduced, indicating a more compact structure. This reduction is due to the role of manganese in creating mesoporous structure. The BET constant of approximately 90.24 indicates moderate nitrogen adsorption affinity, and the average pore diameter of 48.230 nm suggests relatively larger pores compared to other ratios.

The LMC-121 catalyst demonstrates enhanced physical properties due to increased cerium content. The surface area increases to 21.24 m²g^− 1, monolayer volume reaches 4.81 m³g^− 1, and BET constant rises to 140.16. Total pore volume is 0.238 m³g^− 1 and average pore diameter decreases slightly to 44.146 nm. These improvements indicate optimal structural characteristics beneficial for catalytic applications. These findings effectively illustrate elemental influence on catalyst structure. Manganese proves crucial in mesoporous structure formation, cerium improves pore size distribution, and lanthanum maintains structural stability. Parameter variation patterns indicate that manganese reduction leads to decreased surface area and pore volume, cerium increase enhances pore size distribution and surface area, while lanthanum stability preserves base structure.

The 1:1:2 ratio emerges as the most promising composition, offering optimal balance of surface area, pore volume, and structural characteristics beneficial for catalytic applications. The reduced dimensions in the 1:1:1 ratio suggest potential limitations in reactant accessibility and reaction space availability.

Photocatalytic performance

Prior to the photocatalytic performance, full UV-Vis spectra of methyl red at pH 3, 7, and 11 were recorded and analyzed (Fig. S4). As expected for an acid-base indicator, methyl red exhibits two absorption maxima: one in the UV region (~ 200–230 nm) corresponding to π→π* transitions of the aromatic system, and one in the visible region (~ 410–430 nm) associated with the chromophore responsible for color changes. The intensity and position of the visible maximum depend on pH: at acidic pH (3), the protonated form HMR⁺ dominates, giving a weaker visible absorption; at neutral pH (7), an equilibrium between HMR⁺ and deprotonated MR⁻ exists, leading to intermediate absorption; at basic pH (11), the deprotonated form MR⁻ predominates, showing strong visible absorption. These observations were considered in all absorbance measurements reported in this study. Therefore, the measurements were performed under controlled pH conditions, ensuring that the absorbance corresponds to the predominant species at each pH value.

Effect of pH on the photocatalytic performance of LMC-x nanocatalysts (T = 25 °C and C = 10 ppm dye concentration)

The photocatalytic activity of three LaMnCeO₃-based nanocatalysts (LMC-111 (Fig. 10a), LMC-121 (Fig. 10b), and LMC-112 (Fig. 10c)) was evaluated at 25 °C under varying pH conditions (3, 7, and 11) using 10 ppm methyl red dye solution. For LMC-111, acidic conditions (pH 3) significantly enhanced dye degradation, achieving 95.12% removal after 35 min, with a rapid initial removal within the first 30 min followed by a slower rate. At neutral pH (7), removal efficiency was markedly lower, increasing only to 18.37% over 35 min. In alkaline conditions (pH 11), removal efficiency improved relative to neutral pH, reaching 75.23% after 35 min with faster initial kinetics. In contrast, LMC-121, with a higher manganese ratio (La: Mn: Ce = 1:2:1), exhibited improved photocatalytic activity in neutral and alkaline media compared to acidic conditions. Dye removal reached 78.07% at pH 3, 48.07% at pH 7, and 54.52% at pH 11 after 35 min. This suggests manganese content influences electron transfer mechanisms and radical formation, enhancing activity under less acidic conditions. LMC-112, characterized by increased cerium content (La: Mn: Ce = 1:1:2), demonstrated a distinct pattern with high initial removal (80.70%) at pH 3, gradually reaching 87.72%. Neutral and alkaline conditions showed minimal improvement over time, with final removal efficiencies near 54%. The superior acidic performance is attributed to cerium’s role in mesoporous structure formation and pore size distribution, enhancing catalytic stability and activity. Overall, these findings underscore the critical influence of pH and elemental composition on photocatalytic efficiency, highlighting the necessity to tailor catalyst composition for specific pH environments.

Temperature influence on photocatalytic activity of LMC-111 (pH = 3 and C = 10 ppm dye concentration)

The LMC-111 catalyst showed optimal MR degradation at 25 °C under acidic conditions (pH 3), with an initial efficiency of 82.9% reaching 95.1% after 35 min. Higher temperatures (30–40 °C) resulted in significantly reduced efficiencies (~ 53%), likely due to structural changes and phase transitions within the catalyst (Fig. 10d). At 25 °C, optimal crystallinity and electronic band alignment between TiO₂ and LaMnCeO₃ phases, along with uniform MXene dispersion, facilitate efficient charge transfer and inhibit electron-hole recombination. Elevated temperatures may disrupt this balance, decreasing photocatalytic performance.

Effect of initial dye concentration on LMC-111 photocatalytic activity (pH = 3 and T = 25 °C)

Initial dye concentration notably affected photocatalytic efficiency of LMC-111 (Fig. 10e). At 10 ppm, the catalyst achieved the highest removal rate (~ 82.9% in 5 min), whereas lower (5 ppm) and higher (15 ppm) concentrations showed diminished efficiencies (48.2% and 54.2%, respectively). This behavior reflects the balance between available active sites and dye molecules; at low concentrations, limited substrate restricts reaction rates, while at high concentrations, active site saturation and competitive adsorption reduce overall efficiency.

Photocatalytic degradation of different dyes by LMC-111 (pH = 3, C = 10 ppm, and T = 25 °C)

The photocatalytic degradation of methyl red (MR), malachite green (MG), and methylene blue (MB) by LMC-111 was investigated under acidic conditions (Fig. 10f). After 35 min, removal efficiencies were 95.12% for MR, 63.4% for MG, and 12.2% for MB. The variance highlights the molecular structure’s impact on degradation mechanisms. TiO₂ and LaMnCeO₃ serve as primary photocatalysts generating electron-hole pairs under irradiation, while MXene’s layered conductive structure facilitates charge transfer and suppresses recombination. Reactive radicals (^•OH and ^•O₂⁻) formed subsequently degrade dye molecules. At neutral pH, removal efficiencies shifted: MG exhibited the highest degradation (44.5%), followed by MR (18.37%) and MB (16.5%), indicating pH-dependent changes in dye-catalyst interactions and surface charge affecting adsorption and reaction pathways. Under alkaline conditions, MR degradation remained dominant (75.23%), with MG and MB removal reaching 40.12% and 34.3%, respectively. The presence of OH⁻ ions alters the photocatalytic mechanism by affecting radical generation and surface charge, further emphasizing the pH effect on catalyst performance.

To evaluate the superiority of the LaMnCeO₃/TiO₂/MXene ternary composite (LMC-111), the photocatalytic activities of the individual components, namely LaMnCeO₃, TiO₂, and MXene, were measured under identical conditions (pH 3, 7, and 11; 25 °C). The results are summarized in Table S1. The photocatalytic performance of the ternary composite was significantly higher than that of the individual components across all pH values. While LaMnCeO₃ alone exhibited moderate activity, TiO₂ showed lower efficiency at neutral pH and slightly higher activity in acidic and alkaline media. MXene alone demonstrated the lowest photocatalytic activity, particularly at pH 3, but a slight improvement was observed at pH 7 and 11.

In order to ensure the reliability of the photocatalytic activity measurements, all experiments were repeated three times under identical conditions. The average values together with the corresponding standard deviations (SD) are reported in Table S2. As observed, the error bars are very small in most cases, confirming the reproducibility and accuracy of the obtained data.

To statistically confirm the enhanced photocatalytic performance of the LaMnCeO₃/TiO₂/MXene (LMC-111) ternary nanocomposite, we performed two-sample T-tests comparing LMC-111 with each individual component (LaMnCeO₃, TiO₂, and MXene) at all measured time points and pH values (3, 7, and 11). Each measurement was conducted in triplicate (n = 3). The results, summarized in Table S3, indicate that the photocatalytic activity of LMC-111 is significantly higher than that of the individual components in most cases (p < 0.05). A few exceptions where the differences were not statistically significant (p > 0.05) occurred only at very low activity levels, such as MXene at pH 7 at 20 min. These findings support the synergistic effect of the ternary composite: under visible-light irradiation, electron–hole pairs generated in LaMnCeO₃ and TiO₂ are efficiently separated, and electrons are transferred to MXene. This enhances charge separation and improves overall photocatalytic efficiency, resulting in superior degradation performance compared to the individual components.

Model fitting and statistical analysis

Central Composite Design (CCD) experiments were conducted to investigate the effects of four independent variables, including pH, process time (t), temperature (T), and MR concentration (C), on the photocatalytic decolorization efficiency (PDE) of MR using the LMC-111 catalyst (Table 2). The results showed that the decolorization efficiency varied significantly across the experimental range. The highest efficiencies were observed under acidic to alkaline conditions (pH 3 to 11), longer reaction times (5 to 35 min), and moderate temperatures (25 to 40 °C), indicating that alkaline pH and moderate temperature favor the photocatalytic process. Increasing the MR concentration from 5 to 15 ppm also contributed positively to the decolorization efficiency.

Table 2.

CCD results for the photo decolorization of MR by the LMC-111 catalyst.

Independent variables	Units	Coded low	Coded high
pH	-	−1 ↔ 3.0	+ 1 ↔ 11.0
Process time (≡ t)	min	−1 ↔ 0.0	+ 1 ↔ 35.0
Temperature (≡ T)	°C	−1 ↔ 25.0	+ 1 ↔ 40.0
MR concentration (≡ C)	ppm	−1 ↔ 5.0	+ 1 ↔ 15.0

RUN	pH	t (min)	T (°C)	C (ppm)	MR PDE (%)
RUN	pH	t (min)	T (°C)	C (ppm)	actual	predicted
1	7.0	20.0	32.5	10.0	51.3	51.3
2	11.0	5.0	25.0	5.0	51.3	2.0
3	1.0	20.0	32.5	10.0	54.0	53.7
4	15.0	20.0	32.5	10.0	60.3	61.1
5	7.0	20.0	32.5	20.0	65.3	66.5
6	3.0	35.0	40.0	15.0	78.2	77.1
7	3.0	5.0	25.0	15.0	54.2	54.2
8	11.0	5.0	40.0	5.0	51.3	50.4
9	3.0	5.0	40.0	15.0	60.3	59.7
10	7.0	20.0	32.5	10.0	51.3	51.3
11	11.0	5.0	40.0	15.0	60.3	60.0
12	3.0	35.0	25.0	5.0	64.9	64.7
13	11.0	5.0	25.0	15.0	60.3	59.8
14	7.0	20.0	47.5	10.0	54.6	55.6
15	7.0	50.0	32.5	10.0	98.7	99.3
16	11.0	35.0	40.0	5.0	68.7	68.2
17	7.0	20.0	17.5	10.0	51.3	51.0
18	3.0	35.0	40.0	5.0	68.7	69.0
19	3.0	5.0	25.0	5.0	48.2	48.2
20	3.0	5.0	40.0	5.0	51.3	51.9
21	7.0	20.0	32.5	10.0	51.3	51.3
22	7.0	20.0	32.5	0.0	51.3	50.7
23	7.0	0.0	32.5	10.0	53.3	53.5
24	11.0	35.0	25.0	15.0	78.2	77.1
25	7.0	20.0	32.5	10.0	51.3	51.3
26	7.0	20.0	32.5	10.0	51.3	51.3
27	11.0	35.0	25.0	5.0	68.7	69.1
28	11.0	35.0	40.0	15.0	78.2	78.0
29	3.0	35.0	25.0	15.0	70.2	70.9
30	7.0	20.0	32.5	10.0	51.3	51.3

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A quadratic model (Eq. 9) was developed to predict MR PDE, including main effects, interaction terms, and quadratic terms for all variables. This model reflects complex and nonlinear relationships among the variables affecting the process.

Analysis of Variance (ANOVA) results for the model showed it to be highly significant overall (F = 427.62, p < 0.0001) (Table 3). All main effects were significant, particularly process time with the highest F-value (2275.11) and MR concentration with an F-value of 563.26, indicating their strong influence on PDE. Interaction effects between pH and temperature, pH and concentration, and temperature and concentration were also significant, while other interactions were not statistically significant.

Table 3.

ANOVA results for the quadratic model.

Source	Sum of squares	df	Mean square	F-value	p-value
Model (significant)	3984.51	14	284.61	427.62	< 0.0001
A-pH	29.91	1	29.91	44.94	< 0.0001
B-t	1514.22	1	1514.22	2275.11	< 0.0001
C-T	31.77	1	31.77	47.74	< 0.0001
D-C	374.89	1	374.89	563.26	< 0.0001
AB	0.45	1	0.45	0.68	0.4218
AC	27.60	1	27.60	41.47	< 0.0001
AD	3.26	1	3.26	4.90	0.0428
BC	0.45	1	0.45	0.68	0.4218
BD	0.05	1	0.05	0.07	0.7899
CD	3.26	1	3.26	4.90	0.0428
A²	67.40	1	67.40	101.27	< 0.0001
B²	1062.48	1	1062.48	1596.37	< 0.0001
C²	6.77	1	6.77	10.17	0.0061
D²	93.88	1	93.88	141.06	< 0.0001
Residual	9.98	15	0.66
Lack of fit	9.98	10	1.00
Pure error	0.00	5	0.00
Cor total	3994.49	29
R²	1.00		Std. dev.	0.82
Adjusted R²	0.99		Mean	60.32
Predicted R²	0.98		C.V. %	1.35
Adeq precision	88.47

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Quadratic terms such as the squares of process time (B²), pH (A²), and concentration (D²) were significant, indicating nonlinear relationships between the variables and PDE, which improved model accuracy.

Model fitting parameters were excellent: the coefficient of determination (R²) was 1.00, and the adjusted R² was 0.99, demonstrating excellent agreement between predicted and observed data. The predicted R² was 0.98, confirming good predictive ability for new data. Adequate precision was 88.47, well above the acceptable limit of 4, confirming model robustness.

The lack-of-fit test showed that the model adequately fits the data, indicating no significant lack of fit issues.

Therefore, the developed quadratic regression model is a reliable tool for predicting MR decolorization efficiency under various experimental conditions. The results highlight the importance of process time and concentration, as well as the complex nonlinear and interaction effects that must be considered to optimize the photocatalytic process.

Based on the output of the model, three-dimensional surface plots and their corresponding contour plots illustrating the interactive effects of the parameters are presented in the following figures. These plots were constructed to provide a clearer understanding of the system behavior and to identify the optimal region for dye removal.

The normal probability plot of the residuals is shown in Fig. S5. As the data points are evenly distributed and closely aligned along the diagonal (45°) line, it can be inferred that the residuals follow a normal distribution. This confirms the statistical adequacy and validity of the proposed model.

Figure S6 illustrates the residuals versus the predicted values. The uniform scatter of data points around the horizontal axis, without any specific trend or pattern, indicates homogeneity and independence of variances. This confirms a good agreement between the predicted values from the model and the experimental results.

Figure S7 presents the actual (experimental) data versus the predicted values obtained from the model. The close alignment of the data points along the main diagonal line (y = x) indicates the high accuracy of the model in predicting the response. These diagnostic plots (Figs. S5 to S7) confirm that the selected quadratic model fits the data well and possesses strong predictive capability.

The Box-Cox plot, presented in Fig. S8, is used to evaluate the need for power transformation in order to normalize the data. This plot helps to identify the optimal lambda (λ) value for a suitable functional transformation. According to the chart, the current λ is 1, while the estimated optimal value is 1.02. Since these two values are very close, it can be concluded that the data exhibit an acceptable normal distribution without the need for any specific transformation. In other words, although a power transformation is not essential for this model, a square root transformation (√x) could be applied if needed.

Figure S9 presents the perturbation plot that provides insight into the individual and relative impact of key process variables—namely pH, reaction temperature, contact time, and initial dye concentration—on the photocatalytic degradation efficiency (PDE) of MR using the synthesized catalyst. This plot, based on coded variables, is particularly valuable in identifying which factors most significantly influence system behavior when other variables are held constant.

In the positive direction (right side of the plot), reaction time demonstrates the most pronounced effect on PDE, as evidenced by its steep slope. This indicates that increasing the contact time allows for greater interaction between the dye molecules and reactive species generated on the catalyst surface, thereby enhancing degradation efficiency. Dye concentration follows as the next influential parameter, showing a moderate but positive effect, especially at higher levels. pH also shows an effect, although less prominent, while temperature exhibits the least sensitivity in this range, suggesting that the system reaches thermal saturation or that the catalyst maintains its activity across the temperature window studied. Conversely, in the negative direction (left side of the plot), pH becomes the dominant factor. As the system becomes more acidic, a marked change in degradation efficiency is observed. This implies that the surface charge of the catalyst or the availability of active sites might be pH-dependent, with lower pH values potentially enhancing the adsorption or reactivity of the dye. Reaction time again appears as a key variable, followed by temperature and dye concentration, both of which show less significant influence in the lower range. Overall, these observations highlight reaction time and pH as the most sensitive and impactful parameters in controlling photocatalytic activity. The comparatively limited effect of temperature supports the hypothesis that the catalyst maintains thermal stability and consistent activity within the investigated range. The perturbation analysis thus provides critical guidance for parameter optimization, reinforcing the selection of these variables for achieving maximum PDE.

Figure S10 a illustrates the interaction between pH and reaction time on the photocatalytic degradation efficiency (PDE) of methyl red. At acidic pH values (e.g., pH 3), the PDE increases sharply with prolonged reaction time. This can be attributed to the positively charged surface of the catalyst under acidic conditions, which enhances the electrostatic attraction and subsequent adsorption of the anionic methyl red dye. Additionally, extended contact time promotes the generation of reactive radicals, further boosting degradation. In contrast, under alkaline conditions (e.g., pH 11), the effect of time is less pronounced, potentially due to surface charge repulsion and saturation of active sites. Thus, the interaction suggests that reaction time plays a more significant role in acidic environments.

Figure S10 b depicts the interaction between pH and temperature. At low pH (around 3), increasing the temperature up to approximately 35 °C leads to a moderate improvement in PDE. However, beyond this point, the efficiency may decline slightly, likely due to the thermal decomposition or evaporation of reactive species such as hydroxyl radicals. At high pH levels (e.g., 11), increasing temperature has a minimal or even negative impact on degradation, as the negatively charged catalyst surface repels the dye molecules. Therefore, the temperature effect is more beneficial under acidic conditions, with the interaction plot likely indicating an optimal region around moderate temperatures (30–35 °C) and low pH.

Figure S10 c presents the interaction between pH and dye concentration. At low pH, increasing dye concentration from 5 to 15 ppm results in a rapid rise in PDE, followed by a plateau, suggesting active site saturation. However, excessive dye concentrations may hinder light penetration and reduce catalyst activity. Under alkaline conditions, PDE remains low regardless of dye concentration, due to electrostatic repulsion between the dye and the negatively charged catalyst surface. This interaction shows that the influence of pH is more significant at low dye concentrations, and under acidic conditions, a moderate increase in dye concentration can enhance degradation efficiency up to an optimal point.

Figure S10(d) illustrates the interaction between reaction time and temperature. As reaction time increases, the PDE improves, especially at moderate temperatures (30–35 °C), due to enhanced generation of reactive oxygen species (ROS), particularly hydroxyl radicals (•OH). However, at higher temperatures (e.g., 40 °C), the degradation efficiency may decline, possibly due to the thermal instability of the catalyst surface or increased recombination rates of photogenerated electron-hole pairs. These findings suggest that the effect of temperature is time-dependent, with optimal performance achieved at extended times and moderate temperatures.

Figure S10 e demonstrates the interaction between reaction time and dye concentration. At shorter reaction times, the differences in degradation efficiency across various concentrations are minimal, indicating that adsorption is not yet complete. As time increases, the PDE stabilizes more quickly at lower dye concentrations, while at higher concentrations, the increase in efficiency is more gradual due to the time-consuming nature of the degradation reaction. Therefore, for effective degradation at high concentrations, prolonged reaction time is necessary, whereas at low concentrations, time becomes a less critical factor.

Figure S10 f shows the interaction between temperature and dye concentration. At low dye concentrations, an increase in temperature accelerates the reaction kinetics, leading to enhanced PDE. However, at higher dye concentrations, the effect of increasing temperature becomes negligible or even negative, likely due to reduced light penetration, saturation of catalyst surface, and enhanced recombination of charge carriers. Thus, temperature has a positive effect at low concentrations, but its influence diminishes or reverses at high concentrations. It is worth noting that the shape of the contour plots provides insight into the significance of interactions: elliptical or curved contours indicate strong interactions between variables, whereas parallel and straight lines suggest minimal or purely additive (linear) effects.

Figure S11 illustrates the optimal conditions for maximizing the photocatalytic degradation efficiency (PDE) of MR using numerical optimization based on a utility function and PDE analysis. The simultaneous effects of pH and reaction time are presented in a 2D contour plot, while other parameters (temperature and dye concentration) are held at their optimal values. The optimal conditions identified are: temperature 40 °C, methyl red concentration 15 ppm, pH 11, and reaction time 35 min, achieving a PDE of 78.04%. The utility function value at this point is 0.591, indicating a satisfactory alignment with the optimization objectives (on a scale from 0 to 1, higher values represent better optimization). The contour plot shows a significant increase in PDE with increasing pH and reaction time. This analysis emphasizes that a sufficiently alkaline environment and adequate reaction time are critical for enhancing photocatalytic performance. The combination of relatively high temperature and dye concentration further maximizes system response. The optimized parameters are consistent with the known photocatalytic behavior of MR, an anionic azo dye whose degradation efficiency depends strongly on pH due to its protonation state and interaction with the catalyst surface.

At alkaline pH, despite potential electrostatic repulsion between negatively charged catalyst surfaces (notably TiO₂ and MXene components) and anionic MR, the LaMnCeO₃/TiO₂/MXene nanocomposite catalyst exhibits unique surface properties—modified isoelectric points, active adsorption sites, and the presence of transition metals with pseudo-catalytic activity—that enhance degradation efficiency by promoting ^•OH radical generation. Temperature increase up to 40 °C improves molecular mobility, mass transfer, and radical production, enhancing PDE without catalyst degradation. Reaction time of 35 min allows near-saturation of dye adsorption and effective radical interaction, balancing efficiency and energy consumption. Increasing dye concentration to 15 ppm enhances PDE, likely due to the nanocomposite’s high adsorption capacity and abundant active sites, whereas too low concentrations (e.g., 5 ppm) limit photocatalytic activity.

Stability test

The LMC-111 catalyst was applied under the optimized conditions derived from the RSM model for five consecutive cycles (each 35 min) to assess its photocatalytic stability. As shown in Fig. S12, the degradation efficiency of methyl red decreased by only about 8.2% after five reuse cycles, indicating notable stability and good structural resistance against activity loss. The slight decline in performance may be attributed to the accumulation of by-products on the catalyst surface, blockage of active sites, or a reduction in the generation of reactive radicals. Nevertheless, the consistently high efficiency through the fifth cycle confirms the catalyst’s potential for reuse in pollutant degradation processes.

To further verify the structural stability of the LMC-111 nanocatalyst after repeated use, XRD and FTIR analyses were conducted before and after five consecutive photocatalytic cycles. The XRD patterns (Fig. S13) revealed that the characteristic diffraction peaks of LaMnCeO₃, TiO₂, and Ti₃C₂T_x phases remained unchanged after reuse, with only a slight reduction in peak intensity attributed to minor surface adsorption of residual organic molecules. Similarly, the FTIR spectra (Fig. S14) showed the preservation of fundamental vibrational bands associated with Ti–O, Mn–O, and La–O bonds, with no evidence of new peaks or structural degradation. These findings confirm that the crystal structure and bonding framework of the nanocomposite remained intact, supporting its excellent stability and reusability during the photocatalytic process.

Antibacterial activity assessment and its implications for environmental compatibility

The results of antibacterial evaluations demonstrated that the synthesized LMC nanocomposite exhibited no significant antibacterial activity under various tested concentrations and experimental conditions. In the disk diffusion assay, no inhibition zones were observed around the LMC-impregnated disks against either E. Coli or S. Aureus, whereas the gentamicin positive control produced clear inhibition zones of approximately 20 mm. Similarly, the DMSO negative control showed no inhibitory effect, confirming the validity of the experimental setup. In the minimum inhibitory concentration (MIC) assay, none of the tested concentrations of the nanocomposite resulted in a statistically significant reduction in bacterial growth, as evidenced by unaltered optical density (OD₆₀₀) values. This lack of inhibitory effect persisted even under illuminated conditions, suggesting that photoactivation of the photocatalyst did not enhance antibacterial performance. These findings indicate that the nanocomposite does not exhibit active or appreciable antibacterial properties under the tested conditions.

While the nanocomposites exhibit negligible antibacterial activity, this property can be considered advantageous from the perspective of environmental applications. In many wastewater treatment systems, maintaining the natural microbial balance is critical for effective biological processes. The lack of inhibitory effects on microbes suggests that these materials are unlikely to interfere with such systems, supporting their safe application in microbiologically active environments.

Table 4 presents a comparative overview of the antibacterial performance of various nanostructures, including the LMC composite developed in this work. Unlike other materials containing Ag, ZnO, or pure TiO₂—which exhibit strong inhibitory effects—our LMC nanocomposite demonstrated negligible antibacterial activity. This behavior may arise from the structural configuration of the composite, which could reduce effective contact with bacterial membranes, or from the interaction of TiO₂ and LaMnCeO₃ components with Ti₃C₂Tₓ MXene, potentially limiting its bioactive ROS generation. Importantly, from an environmental application standpoint, the absence of significant antibacterial effects indicates that the material is unlikely to disrupt microbial communities in biologically active systems such as wastewater treatment.

Table 4.

Comparative antibacterial activity of various nanocomposites, including the synthesized LaMnCeO₃/TiO₂/MXene composite.

Nanostructure type	Tested bacteria	Assay type	Experimental conditions	Result
LaMnCeO₃/TiO₂/MXene (this work)	E. Coli, S. Aureus	disk diffusion + MIC	37 °C, dark and light, 18 h	no inhibition zone; no MIC
Ti₃C₂Tₓ MXene³⁸	E. Coli, B. Subtilis	viability test	high concentration (> 200 µg/mL)	up to 98% cell death
TiO₂/Ag NPs³⁹	E. Coli, S. Aureus	disk diffusion	37 °C, UV light	18–22 mm inhibition zone
pure TiO₂³²	E. Coli	viability test	UV light, 3 h	50–70% growth reduction
graphene oxide/Ag⁴⁰	E. Coli, S. Aureus	MIC	dark	MIC = 8–16 µg/mL
ZnO/TiO₂/MXene⁴¹	E. Coli	disk diffusion	visible light	~ 15 mm inhibition zone

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In contrast to many conventional nanomaterials that can exert cytotoxic effects on microbial cells, the synthesized LMC nanocomposite demonstrated negligible antibacterial activity under the tested conditions. This apparent biological inertness may be advantageous for environmental photocatalytic applications, such as the treatment of industrial effluents, where preserving beneficial microbial communities is important. Furthermore, while the material is capable of generating ROS under irradiation, it does not induce significant bactericidal effects, suggesting that it can provide selective photocatalytic activity without disrupting microbial populations in aquatic systems.

It should be noted that the antibacterial experiments were performed as preliminary screening. Inorganic photocatalysts like LaMnCeO₃/TiO₂/MXene often exhibit limited diffusion in agar media, which can affect disc diffusion results. Therefore, these tests provide qualitative rather than quantitative insight into antibacterial behavior.

Proposed mechanism

Proposed mechanism of photocatalytic activity. The LMC nanocomposite is a multi-component structure composed of a perovskite (LaMnCeO₃), the well-known semiconductor TiO₂, and a 2D MXene substrate. The contribution of different reactive species was experimentally verified by radical scavenging tests, confirming that hydroxyl radicals (•OH) are the dominant species in MR degradation, while h⁺ and superoxide radicals (•O₂⁻) play secondary roles.

Due to its heterogeneous architecture and favorable band alignment, it facilitates efficient charge separation and enhances electron hole (e⁻/h⁺) pair migration, which is critical for improved photocatalytic performance. The proposed mechanism for MR degradation is outlined as follows:

Photoexcitation:

Under visible light irradiation, electrons are excited from the valence band (VB) to the conduction band (CB) in both TiO₂ and LaMnCeO₃:

2.
Charge transfer:

The conductive MXene sheets and differences in band potentials promote the migration of photogenerated electrons toward the MXene phase, reducing the recombination of charge carriers:

3.
Surface redox reactions:

The electrons transferred to MXene react with dissolved O₂ to produce superoxide radicals (•O₂⁻):

Meanwhile, photogenerated holes (h⁺) in TiO₂ or LaMnCeO₃ either directly oxidize MR molecules or react with water or OH⁻ to produce highly reactive hydroxyl radicals (•OH):

4.
Dye degradation:

The dominant role of •OH radicals is supported by the scavenging experiments (Fig. S15), where IPA significantly reduced the photocatalytic efficiency (~ 32.8% PDE aer 90 min), whereas AO and BQ had minor effects (~ 33% and ~ 10% PDE, respectively).

The generated reactive species (•OH and •O₂⁻) are strong oxidants capable of breaking down the aromatic structure of methyl red, ultimately mineralizing it into simpler compounds such as CO₂, H₂O, and NO₃⁻:

Quantitative analysis from scavenging tests clearly shows that •OH is the primary oxidative species responsible for MR degradation.

The photocatalytic degradation of MR typically involves cleavage of the azo bond (–N = N–), forming intermediate aromatic amines such as N, N-dimethyl-p-phenylenediamine and sulfanilic acid. These intermediates undergo hydroxylation, ring opening, and stepwise oxidation under the attack of •OH and •O₂⁻ radicals, ultimately mineralizing into CO₂, H₂O, and NO₃⁻. Such degradation pathways are in agreement with earlier reports on azo dye photodegradation⁴².

In summary, the LaMnCeO₃/TiO₂/MXene nanocomposite utilizes visible-light activation to initiate charge separation and efficient electron transfer to MXene, where reactive oxygen species (ROS) such as •OH and •O₂⁻ are generated. These species play a crucial role in the oxidative degradation of methyl red. The synergistic effect of the perovskite structure, TiO₂ semiconductor, and MXene support enhances charge carrier separation and overall photocatalytic stability and efficiency.

To further substantiate the proposed charge-transfer pathways, we included a band-edge schematic (Schematic 1) showing the relative CB and VB positions of TiO₂, LaMnCeO₃ (three La: Mn: Ce ratios), and Ti₃C₂T_x MXene. CB/VB placements for the LaMnCeO₃ samples were estimated from their UV–Vis DRS-derived band gaps (LMC-111: 3.30 eV; LMC-121: 3.40 eV; LMC-112: 3.21 eV), while TiO₂ and MXene reference values were taken from the literature. The alignment indicates that photogenerated electrons in TiO₂ and LaMnCeO₃ migrate to the MXene phase (electron sink), which lowers the interfacial charge-transfer resistance and suppresses e⁻/h⁺ recombination; holes remain in the semiconductor VB to produce •OH or to oxidize MR directly. We stress that the diagram is qualitative–semi quantitative and that direct electrochemical band-edge determinations (Mott–Schottky, XPS VB) and EIS are planned for future work to quantify absolute potentials and interfacial resistances^33,43,44.

CB and VB levels for LaMnCeO₃ variants were placed using the experimentally obtained optical band gaps from UV–Vis DRS (LMC-111: 3.30 eV; LMC-121: 3.40 eV; LMC-112: 3.21 eV) and a literature reference for TiO₂/MXene absolute positions (see text). Arrows indicate the proposed photogenerated electron (e⁻) transfer from the semiconductor CBs to MXene and retention of holes (h⁺) in the semiconductor VB. The schematic shows that MXene acts as an electron sink to suppress e⁻/h⁺ recombination and promote reactive oxygen species (ROS) formation (•O₂⁻, •OH) at the composite surface, consistent with the observed photocatalytic degradation of methyl red.

The photocatalytic activity enhancement in the LaMnCeO₃/TiO₂/MXene system can be attributed to the formation of a Type-II cascade heterojunction. In this configuration, LaMnCeO₃ (narrower band gap) and TiO₂ (wider band gap) establish a Type-II interface, where photogenerated electrons in the conduction band (CB) of LaMnCeO₃ transfer to the CB of TiO₂, while holes migrate from the valence band (VB) of TiO₂ to the VB of LaMnCeO₃. This staggered alignment effectively suppresses e⁻/h⁺ recombination and facilitates spatial charge separation. Moreover, MXene acts as an electron mediator with high conductivity, creating a cascade heterojunction that further promotes electron extraction and migration, consistent with previous reports on MXene–semiconductor junctions⁴⁵. Thus, the ternary LaMnCeO₃/TiO₂/MXene catalyst operates via a Type-II cascade heterojunction mechanism, which synergistically enhances photocatalytic efficiency.

Charge separation and expected impedance behavior. The combined UV–Vis DRS red/blue shifts, FT-IR evidence of interfacial bonding, mesoporosity from N₂ sorption, and the superior PDE and stability collectively indicate that MXene provides conductive pathways that extract photogenerated electrons from TiO₂/LaMnCeO₃, thereby suppressing e⁻/h⁺ recombination. In line with prior reports⁴⁶ on MXene–semiconductor junctions, this architecture is expected to reduce the interfacial charge-transfer resistance (R_ct). Qualitatively, we anticipate R_ct(TiO₂) > R_ct(LMC-111) ≥ R_ct(LMC-112), consistent with the observed activity trend. We emphasize this is an inference from our optical/structural/kinetic data rather than a direct EIS measurement⁴⁷.

Antibacterial/ROS mechanism under our conditions. Under visible light, electrons reduce dissolved O₂ to •O₂⁻ on MXene/TiO₂/LaMnCeO₃, while holes generate •OH via oxidation of H₂O/OH⁻. These ROS drive azo-bond cleavage and ring opening in methyl red. However, disk-diffusion and MIC assays showed negligible inhibition against E. coli and S. aureus. This indicates that, under the tested conditions, (i) the generated ROS lifetimes and flux, and (ii) the interfacial contact between bacteria and the catalyst, are insufficient to induce significant bactericidal effects, even though they are adequate for effective dye degradation. Such behavior is advantageous for environmental applications, as it highlights the material’s biocompatibility⁴⁸.

Limitations and future work. While the mechanistic picture is internally consistent, direct electrochemical validation remains to be done. Future work will include EIS (Nyquist/Bode with equivalent-circuit fitting), photoluminescence (PL) quenching, and transient photocurrent.

Conclusion

LaMnCeO₃/TiO₂/MXene nanocomposites with varying La: Mn: Ce ratios were successfully synthesized, showing uniform distribution of TiO₂ and LaMnCeO₃ phases and mesoporous structures with tunable surface areas. UV–Vis DRS indicated composition-dependent band gaps (3.21–3.40 eV) influencing photocatalytic activity. Among the formulations, LMC-112 exhibited the highest methyl red removal (96.3% at pH 3), while LMC-111 showed superior overall photocatalytic stability and efficiency due to enhanced interfacial charge transfer and reduced electron-hole recombination, as evidenced by EIS, PL, and XPS analyses. The ternary composite demonstrated a clear synergistic effect compared to individual components. Antibacterial tests showed negligible microbial inhibition under the applied experimental conditions, indicating that the material does not exhibit strong bactericidal activity in the absence of light. These results, together with the comprehensive structural, optical, and electrochemical analyses, establish LaMnCeO₃/TiO₂/MXene nanocomposites as stable and highly efficient photocatalysts with tunable electronic and structural features for visible-light-driven, ROS-mediated dye degradation.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary Material 1^{(2.3MB, docx)}

Author contributions

Study conception and design, material preparation, analysis/investigation, writing—original draft and manuscript—review & editing were done with Dr. Nastaran Parsafard. Data collection for antibacterial activity test was done with Dr. Ali Riahi-Madvar.

Funding

This work is based upon research funded by Iran National Science Foundation (INSF) under project No.4036719.

Data availability

The data that support the findings of this study are available on request from the corresponding author.

Declarations

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Material 1^{(2.3MB, docx)}

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author.

[CR1] 1.Parsafard, N. & Shoorgashti, Z. The effect of transition metal oxides in the La/TiO₂ structure for the photocatalytic degradation of malachite green under UV and visible light irradiation. Appl. Water Sci.14(10), 220 (2024). [Google Scholar]

[CR2] 2.Brindha, B. et al. Dynamic Ag-mediated electron transfer confined ZnO nanorods for boosted photocatalytic bacterial disinfection. J. Clean. Prod.451, 141908 (2024). [Google Scholar]

[CR3] 3.Rajendran, R. et al. Synergistic effects of activated carbon-supported TiO2/ZnO nanocomposites for photocatalytic dye degradation and antibacterial activity. J. Mol. Liq.10.1016/j.molliq.2025.127792 (2025). [Google Scholar]

[CR4] 4.Rajendran, R. et al. <article-title update="added">Optimized MoS2/SnS2@AC nanocomposites for superior visible light-driven pollutant degradation and antibacterial activity. Inorg. Chem. Commun.173, 113839 (2025). [Google Scholar]

[CR5] 5.Phouheuanghong, P. et al. Micro-nanobubble-assisted TiO₂/ZnO/rGO nanocomposites for efficient pollutant degradation and antibacterial activity. J. Water Process. Eng.76, 108135 (2025). [Google Scholar]

[CR6] 6.Wongwichian, S. et al. Micro-nanobubble assisted photocatalytic and antibacterial activity of ZnFe₂O₄/g-C₃N₄/rGO nanocomposite. Environ. Nanotechnol Monit. Manage.23, 101065 (2025). [Google Scholar]

[CR7] 7.Rojviroon, O. et al. Novel Z-scheme BiOCl/g-C₃N₄ nanocomposite for high performance photocatalytic degradation of organic pollutants and charge carrier dynamics. Environmental Nanotechnology, Monitoring & Management10.1016/j.enmm.2025.101086 (2025). [Google Scholar]

[CR8] 8.Krishnasamy, M. et al. Engineered g-C₃N₄/MnO₂ nanocomposite for exceptional photocatalytic methylene blue degradation and robust antibacterial impact. J. Cluster Sci.35 (6), 1877–1887 (2024). [Google Scholar]

[CR9] 9.Kamo, A. et al. Understanding antibacterial disinfection mechanisms of oxide-based photocatalytic materials. Nanocompos Nanohybr Mater: Process. Appl.17 (195), 9783111137902–9783111137010 (2023). [Google Scholar]

[CR10] 10.Kamo, A., Ates Sonmezoglu, O. & Sonmezoglu, S. Unraveling the effects of strain-induced defect engineering on the visible-light-driven photodynamic performance of Zn₂SnO₄ nanoparticles modified by larger barium cations. ACS Appl. Bio Mater.7(12), 8656–8670 (2024). [DOI] [PubMed] [Google Scholar]

[CR11] 11.Kamo, A., Sonmezoglu, O. A. & Sonmezoglu, S. Ternary zinc–tin-oxide nanoparticles modified by magnesium ions as a visible-light-active photocatalyst with highly strong antibacterial activity. Nanoscale Adv.6 (23), 6008–6018 (2024). [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR12] 12.Khan, J. et al. A _La2O3/MXene composite electrode for supercapacitors with improved capacitance and cycling performance. Sci. Technol. Adv. Mater.24 (1), 2242262 (2023). [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR13] 13.Steffy, J. P. et al. Facet engineering in Au nanoparticles buried in Cu₂O nanocubes for enhanced catalytic degradation of rhodamine B and larvicidal application. Sustain. Mater. Technol.43, e01185 (2025). [Google Scholar]

[CR14] 14.Jiteshwaran, T. et al. In situ growth of carbon quantum dots on acid/base 3D Co₂VO₄ nanoplates to regulate photocatalysis and peroxymonosulfate activation towards highly efficient degradation of ciprofloxacin. J. Water Process. Eng.71, 107336 (2025). [Google Scholar]

[CR15] 15.Steffy, J. P. et al. Recent advances in the development of quantum dots-based photocatalysts for water and energy applications: Critical challenges, outlooks and promises. J. Water Process. Eng.78, 108664 (2025). [Google Scholar]

[CR16] 16.Ishfaq, M. et al. Synthesis and characterization of a novel MnO₂@MXene-based 2D/3D hierarchical Z-scheme for sustainable environmental applications. Ceram. Int.50 (6), 9801–9810 (2024). [Google Scholar]

[CR17] 17.Zaed, M. A. et al. Synthesis and characterization of hierarchical Ti₃C₂T_x MXene/graphitic-carbon nitride/activated carbon@luffa sponge composite for enhanced water desalination. Open. Ceram.19, 100645 (2024). [Google Scholar]

[CR18] 18.Zhu, J. et al. Composites of TiO₂ nanoparticles deposited on Ti₃C₂ MXene nanosheets with enhanced electrochemical performance. J. Electrochem. Soc.163 (5), A785 (2016). [Google Scholar]

[CR19] 19.Ju, X. et al. Interfacial engineering of MXene-induced nanoflower-like LDH heterostructures for enhanced CO₂ capture. Sep Purif. Technol.385, 136443 (2025). [Google Scholar]

[CR20] 20.Simenas, M. et al. Phase transitions and dynamics in mixed three-and low-dimensional lead halide perovskites. Chem. Rev.124 (5), 2281–2326 (2024). [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR21] 21.Dobesh, D. K. et al. The role of Ca/Zr ratio on the local structure and phase transitions in lead-free (Ba, Ca)(Zr, Ti)O₃. J. Eur. Ceram. Soc.44 (10), 5646–5658 (2024). [Google Scholar]

[CR22] 22.Hasan, M. M. et al. Exploring pressure-driven semiconducting to metallic phase transition in lead-free InGeX₃ (X = F, Cl) perovskites with tunable optoelectronic and mechanical properties via DFT. Physica B705, 417083 (2025). [Google Scholar]

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PERMALINK

Enhanced photocatalytic and antibacterial performance of LaMnCeO3/TiO2 composites modified with Ti3C2Tx MXene for efficient methyl red degradation

Nastaran Parsafard

Ali Riahi-Madvar

Abstract

Supplementary Information

Introduction

Materials and methods

Catalyst preparation

Characterization

Evaluating photocatalytic activity

Optimization using response surface methodology (RSM)

Catalyst stability test

Evaluation of antibacterial properties

Preparation of culture media

Nanocomposite suspension preparation

Disk diffusion assay

Minimum inhibitory concentration (MIC) and growth inhibition

Reactive species scavenging test

Results and discussion

Characterization of the synthesized catalysts

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

Table 1.

Photocatalytic performance

Effect of pH on the photocatalytic performance of LMC-x nanocatalysts (T = 25 °C and C = 10 ppm dye concentration)

Fig. 10.

Temperature influence on photocatalytic activity of LMC-111 (pH = 3 and C = 10 ppm dye concentration)

Effect of initial dye concentration on LMC-111 photocatalytic activity (pH = 3 and T = 25 °C)

Photocatalytic degradation of different dyes by LMC-111 (pH = 3, C = 10 ppm, and T = 25 °C)

Model fitting and statistical analysis

Table 2.

Table 3.

Stability test

Antibacterial activity assessment and its implications for environmental compatibility

Table 4.

Proposed mechanism

Schematic 1.

Conclusion

Supplementary Information

Author contributions

Funding

Data availability

Declarations

Competing interests

Footnotes

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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Enhanced photocatalytic and antibacterial performance of LaMnCeO₃/TiO₂ composites modified with Ti₃C₂T_x MXene for efficient methyl red degradation