A dual-film platform for simultaneous bacterial disinfection and H₂S scavenging with integrated fluorescent sensing for real-time visual monitoring

Abstract

Slaughterhouse and meat-processing wastewater contains a complex mixture of organic pollutants, pathogenic bacteria, and toxic hydrogen sulfide (H₂S), posing serious risks to both public health and the environment. To address these challenges, we have developed a dual-film platform comprising: (1) a cellulose acetate (CA) film loaded with a cerium-based metal–organic framework (Ce-MOF) for efficient bacterial disinfection and H₂S scavenging, and (2) a CA film embedded with a fluorescent probe (JM-NO₂) for real-time visual monitoring of H₂S. The incorporation of JM-NO₂ into the CA matrix enables both naked-eye visualization and smartphone-based quantification of H₂S. The Ce-MOF film exhibits robust reactive oxygen species (ROS)-generating catalytic activity under mild conditions, enabling rapid microbial inactivation and effective H₂S elimination. In a dual-film configuration, sequential filtration through the Ce-MOF and JM-NO₂ films allows for simultaneous disinfection, H₂S removal, and immediate visual detection of residual H₂S. The system demonstrates excellent stability and sensitivity under environmentally relevant conditions. This dual-film platform offers a scalable and practical approach to wastewater treatment, integrating contaminant removal with real-time monitoring, and holds significant potential for environmental remediation and sustainable water management.

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1. Introduction

Wastewater generated from slaughterhouses and meat processing plants poses a significant environmental burden due to its complex composition, which includes high levels of organic matter, nutrients, fats, oils, and a range of hazardous contaminants.^1–3 These effluents originate from multiple stages of meat processing—including slaughtering, cleaning, deboning, and packaging—contributing to a substantial pollutant load.^4,5 Among these contaminants, hydrogen sulfide (H₂S) stands out as a particularly harmful pollutant.^6,7 As a colorless gas which is highly soluble in water with a characteristic foul odor, H₂S is highly toxic and corrosive, posing serious environmental, infrastructural, and public health concerns.^8,9 Its release into the environment can lead to air and water pollution, corrosion of wastewater infrastructure, and oxygen depletion in aquatic ecosystems.^10,11 Therefore, the efficient and sustainable removal of H₂S from wastewater has become a pressing goal in modern environmental management.

In addition to chemical pollutants, slaughterhouse wastewater frequently contains high concentrations of pathogenic bacteria,¹² which can contaminate downstream water bodies, promote the spread of waterborne diseases, and disrupt aquatic ecosystems.¹³ Accordingly, effective strategies that can simultaneously eliminate H₂S and inactivate microbial contaminants are essential for ensuring safe wastewater discharge and regulatory compliance.

Conventional methods for H₂S detection and removal often suffer from significant drawbacks, including high operational costs and a lack of real-time monitoring capabilities.^14–18 In recent years, fluorescent probes have become powerful tools for chemical sensing and bioimaging, offering excellent sensitivity, high selectivity and rapid response time. These advantages make them superior to conventional detection methods, particularly real-time monitoring applications.^19–23 And fluorescent probes have been designed for the detection of H₂S.^24–28 Among them, film-based fluorescent sensors are particularly attractive due to their portability, reusability, and ease of integration into treatment systems. These films enable simple visual readouts without the need for complex instrumentation, making them ideal for on-site monitoring applications.^29–33

Simultaneously, nanozymes—particularly metal–organic frameworks (MOFs)—have gained attention as promising agents for environmental remediation.^34–39 MOFs are crystalline, porous materials constructed from metal ions coordinated with organic ligands.^40–42 Compared to conventional nanozymes, MOFs offer well-defined structures and tunable properties.^43–45 By modulating metal valence states (e.g., Ce(III)/Ce(IV) and Fe(II)/Fe(III)) and ligand functionalities (e.g., porphyrins, imidazoles), MOFs can mimic natural oxidase (OXD) and peroxidase (POD) activity.^46–49 These enzyme-mimicking activities catalyze the generation of reactive oxygen species (ROS), including superoxide anions (˙O₂⁻) and hydroxyl radicals (˙OH), which can both oxidize H₂S and disinfect bacterial pathogens.^50–55 Therefore, MOF-based nanozymes provide dual functions for simultaneous pollutant scavenging and antimicrobial activity.

In this study, we report a dual-film system that integrates chemical sensing, pollutant removal, and microbial disinfection into a single platform (Scheme 1). The first film consists of CA embedded with a cerium-based MOF (Ce-MOF), designed for the oxidative removal of H₂S and antibacterial treatment. The Ce-MOF demonstrates both OXD-like and POD-like catalytic activities across a broad pH range, promoting robust ROS generation. These ROS serve a dual role by (1) oxidizing and neutralizing H₂S and (2) effectively inactivating bacterial contaminants. The second film is composed of cellulose acetate (CA) doped with a small-molecule fluorescent probe, JM-NO₂. This film is non-emissive under normal conditions but becomes highly fluorescent upon reacting with H₂S, enabling rapid, visual, and quantitative detection of H₂S in aqueous environments. JM-NO₂ exhibits excellent sensitivity (detection limit: 23.8 nM), high selectivity and strong anti-interference capacity, making it suitable for real-world wastewater analysis.

Scheme 1 (a) Schematic illustration of the dual-film system for bacterial inactivation, H₂S monitoring and scavenging. (b) The probe's structure and its fluorescent response to H₂S for visual monitoring. (c) Ce-MOF's OXD- and POD-like activities for microbial disinfection.

Together, this dual-film system offers a multifunctional, low-cost, and environmentally friendly solution for slaughterhouse wastewater treatment. It enables (1) effective H₂S scavenging, (2) broad-spectrum bacterial disinfection, and (3) real-time, visual monitoring of H₂S levels. This integrated approach holds significant promise for advancing wastewater management practices in meat processing and other high-impact industries.

2. Results and discussion

2.1. Synthesis and optical response of JM-NO₂ toward H₂S

The fluorescent probe JM-NO₂ was synthesized as outlined in Scheme S1. Its structure was fully characterized by ¹H/¹³C NMR spectroscopy and high-resolution mass spectrometry (as shown in Fig. S1–S5). The probe's optical response to H₂S was evaluated using NaHS as the H₂S donor. As shown in Fig. 1a, JM-NO₂ (20 μM) in phosphate buffer (PB) containing 2% DMSO exhibits negligible fluorescence in the absence of H₂S. Upon addition of H₂S, the fluorescence intensity at 487 nm (λ_ex = 425 nm) increases progressively, reaching a plateau at ∼25 μM H₂S. The fluorescence response is rapid, with equilibrium achieves within 25 minutes (Fig. S6), indicating the probe's high sensitivity and fast kinetics.

Fig. 1 (a) Fluorescence spectra of JM-NO₂ (20 μM) with H₂S at different concentrations (0–30 μM). (b) Linear relationship plot of JM-NO₂ fluorescence intensity versus H₂S concentration. (c) UV-Vis absorption spectra of JM-NO₂ (20 μM) with H₂S at different concentrations (0–30 μM). (d) Effect of pH on the fluorescence intensity of JM-NO₂ (20 μM) with and without H₂S (30 μM). (e) Fluorescence spectra of JM-NO₂ (20 μM) in the presence of H₂S and other analytes (200 μM). (f) Histogram showing the selectivity and anti-interference of JM-NO₂ (20 μM) toward H₂S (30 μM) in the presence of other substances (200 μM) (ex = 425 nm).

A linear correlation between H₂S concentration and fluorescence intensity can be observed (Fig. 1b). The limit of detection (LOD), calculated via the 3σ/k method, is 23.8 nM—well below the WHO limit for H₂S in drinking water (1.47 μM).⁵⁶ Compared with reported probes for H₂S (Table S1), JM-NO₂ offers key advantages, including a turn-on fluorescence response, lower detection limit, and the ability to detect H₂S in water. The absorption maximum of JM-NO₂ at 495 nm exhibits a blue shift to 422 nm in the presence of H₂S, accompanied by a visible color change from brown to light yellowish green. UV-vis absorption titration confirmed this shift, with a decreasing 495 nm band and emerging 422 nm peak (Fig. 1c and Fig. S7).

JM-NO₂ exhibits stable and robust fluorescence responses to H₂S across a broad pH range (6.0–10.0), supporting its utility in environmental samples (Fig. 1d). To evaluate the selectivity and anti-interference capability of JM-NO₂, a series of substances (cations, anions, and biothiols) were added to the JM-NO₂ solution, including cations (Na⁺, Ca²⁺, K⁺, Al³⁺, Zn²⁺, Mg²⁺, Fe³⁺, Cu²⁺, Ba²⁺), anions (CO₃²⁻, SO₄²⁻, PO₄³⁻, H₂PO₄⁻, HPO₄²⁻, Cl⁻, F⁻), small-molecule biological thiols (Cys, GSH and HCy), inorganic sulfur species such as thiosulfate (S₂O₃²⁻), bisulfite (HSO₃⁻), and sulfite (SO₃²⁻). As shown in Fig. 1e, compared to H₂S, the fluorescence at 487 nm shows almost no change for the probe in the presence of the other substances. Furthermore, the presence of other substances has no obvious effect on the detection of H₂S (Fig. 1f). The above results demonstrate that JM-NO₂ possesses strong selectivity and anti-interference ability, confirming the probe's high specificity for H₂S even in complex matrices.

2.2. Mechanism of JM-NO₂ response to H₂S

The reaction mechanism was elucidated by high-resolution mass spectrometry. Upon addition of NaHS, peaks corresponding to 2,4-dinitrobenzenethiol (m/z = 198.9812, negative ion mode) and coumarin 343 (m/z = 308.0891, positive ion mode) were observed (Fig. 2a, b and Fig. S8, S9). The initially weak fluorescence of JM-NO₂ is due to photoinduced electron transfer (PET). Upon H₂S-triggered cleavage of the ether bond, PET is disrupted, enabling a nucleophilic attack by the resulting phenol on the intramolecular ester, forming highly fluorescent, water-soluble coumarin 343 via acetone elimination and proton transfer (Fig. 2c), which emits bright green fluorescence.

Fig. 2 (a) HRMS spectrum of JM-NO₂ after addition of H₂S (positive ion mode). (b) HRMS spectrum (negative ion mode). (c) Schematic illustration of the recognition mechanism of JM-NO₂ toward H₂S.

2.3. Development of a JM-NO₂-doped CA film for H₂S detection

To facilitate practical application, JM-NO₂ was embedded into a cellulose acetate (CA) film. Immersion in H₂S-containing solution causes a visible color change (brown to pale yellowish green) under ambient light and a concentration-dependent increase in green fluorescence under 365 nm UV illumination (Fig. 3a). Fluorescence changes are perceptible to the naked eye above 3 μM H₂S. For field analysis, fluorescence images are captured with a smartphone, and the green-channel (G-value) intensity is quantified via a color analysis app. A strong linear relationship (R² = 0.99) is observed between G-value and H₂S concentration (0–24 μM, Fig. 3b), highlighting the film's utility for rapid, visual, and quantitative detection.

Fig. 3 (a) Photographs of the JM-NO2-containing CA film under visible light and under 365 nm UV irradiation after immersion in H₂S solutions of different concentrations (0–24 μM). (b) On-site detection platform for H₂S using a smartphone-based method, with the corresponding calibration curve of G-value versus H₂S concentration.

2.4. Synthesis and characterization of Ce-MOF

Cerium metal–organic frameworks (Ce-MOF) are considered promising candidates for developing novel biomimetic oxidase and peroxidase nanozymes due to the Ce(III)/Ce(IV) redox pair's properties, offering potential for H₂S removal and disinfection to ensure quality of wastewater treatment and discharge. To enable catalytic disinfection and H₂S scavenging, a Ce-MOF was synthesized using (NH₄)₂Ce(NO₃)₆ and 1,3,5-benzenetricarboxylic acid (Fig. 4a). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images reveal that Ce-MOF exhibits predominantly spherical morphology with diameters ranging 300–400 nm (Fig. 4b and c). Dynamic light scattering (DLS) analysis indicates a slightly larger hydrodynamic diameter of 531 nm (Fig. S10). EDS mapping indicates that C, O, and Ce are uniformly distributed on the Ce-MOF surface (Fig. 4d). The structure of Ce-MOF was confirmed by X-ray diffraction (XRD) analysis, with the XRD pattern of Ce-MOF showing good agreement with the calculated Ce-MOF-808 curve (Fig. 4e). The survey spectrum of X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of C, O, and Ce (Fig. 4f), further verifying successful Ce-MOF synthesis. High-resolution Ce 3d analysis of Ce-MOF (Fig. 4g) indicates mixed-valence Ce(III)/Ce(IV) states. The characteristic Ce(III) signature includes the 903.91 eV peak corresponding to the Ce 3d_3/2 component (labeled as u^I) and the 885.40 eV peak corresponding to the Ce 3d_5/2 component (labeled as v^I) (Table S2). While Ce(IV) exhibits six distinct subpeaks: 916.93, 906.95 and 901.15 eV belonging to the Ce 3d_3/2 component (u^III, u^II, and u), as well as 898.87, 887.04, and 882.37 eV corresponding to the Ce 3d_5/2 component (v^III, v^II, and v).⁵⁷ Quantitative analysis (peak fitting and peak area integration calculations) shows Ce(IV) dominates the surface composition which was determined to be 63.64%. These results demonstrate the successful synthesis of mix-valence Ce-MOF.

Fig. 4 Ce-MOF's synthesis and characterization. (a) Schematic diagram illustrating the Ce-MOF preparation. (b) Ce-MOF's TEM image (scale bar: 200 nm). (c) Ce-MOF's SEM image (scale bar: 200 nm). (d) Ce-MOF's EDS mapping. (e) Ce-MOF's XRD pattern. (f) Ce-MOF's XPS spectrum. (g) Ce-MOF's high-resolution Ce 3d XPS spectrum.

2.5. Ce-MOF's oxidase-like and peroxidase-like activities

The catalytic (nanozyme) activities of Ce-MOF were assessed using 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation assays. Ce-MOF demonstrates both oxidase-like (OXD-like) and peroxidase-like (POD-like) activities. OXD-like activity converts O₂ into ˙O₂⁻, while POD-like activity decomposes H₂O₂ into ˙OH (Fig. 5a). The ˙O₂⁻ generated by OXD-like activity and the ˙OH generated by POD-like activity can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB) in the absence and presence of H₂O₂, respectively, which exhibits characteristic absorption at 652 nm. Therefore, colorimetric determination using TMB was employed to validate the Ce-MOF's OXD-like and POD-like activities. As shown in Fig. 5b, TMB + Ce-MOF and H₂O₂ + TMB + Ce-MOF exhibit distinct UV absorption peaks at 652 nm, whereas no corresponding absorption peaks can be observed in the control groups TMB + H₂O₂ and H₂O₂+ Ce-MOF. This indicates that Ce-MOF possesses OXD-like and POD-like activities. The effect of pH on Ce-MOF's OXD-like and POD-like activities was then investigated. Ce-MOF exhibits high OXD-like and POD-like activities over a broad pH range (Fig. S11a and b). Notably, while most reported nanozymes exhibit enhanced activity in acidic conditions, Ce-MOF maintains high activity across a broad pH range. Even at pH = 7.4, its OXD-like and POD-like activities remain exceptionally prominent, a characteristic that significantly outperforms many reported nanozymes (Tables S3 and S4). At pH = 7.4, as shown in Fig. 5c, d, f and g, Ce-MOF's steady-state kinetic parameters follow the classical Michaelis–Menten equation and Lineweaver–Burk model. The Michaelis constant (K_m) represents the enzyme–substrate binding affinity, where lower values indicate stronger binding interactions. The maximum reaction rate (V_max) corresponds to the enzyme's maximum catalytic efficiency (conversion efficiency at substrate saturation). For OXD-like activity (TMB substrate), we obtain K_m = 0.041 mM and V_max = 2.58 × 10⁻⁷ M s⁻¹, respectively (as shown in Fig. 5c and d), indicating exceptionally strong substrate affinity and efficient catalytic conversion. Similarly, POD-like activity (H₂O₂ substrate) shows K_m = 1.339 mM and V_max = 2.48 × 10⁻⁷ M s⁻¹, respectively (as shown in Fig. 5f and g). Notably, these kinetic parameters outperform most reported nanozymes (Tables S3 and S4), especially the K_m value, which is reduced by an order of magnitude compared to most reported values. These values indicate high catalytic efficiency and substrate affinity of the Ce-MOF.

Fig. 5 Ce-MOF's oxidase-like and peroxidase-like properties. (a) Schematic diagram illustrating Ce-MOF's nanozymes activity and the method for detecting nanozymes activity. (b) UV-Vis absorption spectra of H₂O₂ + TMB, H₂O₂ + Ce-MOF, TMB + Ce-MOF, and H₂O₂ + TMB + Ce-MOF at pH = 7.4. The corresponding color changes are displayed in the inset. Michaelis–Menten kinetics (c) and corresponding Lineweaver–Burk plot (d) of Ce-MOF's OXD-like activity using TMB as substrate in phosphate buffer (pH 7.4). (e) EPR spectra of DMPO capture of ˙O₂⁻ after different treatments. Michaelis–Menten kinetics (f) and corresponding Lineweaver–Burk plot (g) of Ce-MOF's POD-like activity using H₂O₂ as substrate in phosphate buffer (pH = 7.4). (h) EPR spectra of DMPO capture of ˙OH after different treatments.

To further validate the enzymatic mechanisms (Ce-MOF's POD-like and OXD-like activities), we employed electron paramagnetic resonance (EPR) spectroscopy with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap. DMPO specifically captures ˙O₂⁻, forming the stable DMPO–OOH adduct that can be detected by EPR. As shown in Fig. 5e, the EPR spectrum exhibits a six-line signal composed of four main peaks and two minor peaks, with the main peak intensities being nearly 1 : 1 : 1 : 1 characteristic of ˙O₂⁻. The control group lacks this signal, confirming OXD-like activity. When verifying POD-like activity, using DMPO as a spin trap (which captures ˙OH, forming DMPO–OH), we detect ˙OH generation through the characteristic 1 : 2 : 2 : 1 four-line signal observed in the EPR spectrum (Fig. 5h). The absence of this signal in control experiments confirms the ˙OH production originates specifically from the POD-like activity of Ce-MOF.

2.6. H₂S scavenging by Ce-MOF monitored via JM-NO₂

To verify that the ˙O₂⁻ generated by Ce-MOF's OXD-like can undergo redox reactions with H₂S to remove H₂S, we first investigated the H₂S removal efficiency of Ce-MOF in aqueous solutions, using JM-NO₂ as a fluorescent indicator of H₂S level. As shown in Fig. 6a, when no H₂S is present, adding Ce-MOF to the JM-NO₂ system results in little change in fluorescence. However, when H₂S is present, a concentration-dependent fluorescence quenching at 487 nm with increasing Ce-MOF amounts can be observed (Fig. 6b and c). When the Ce-MOF amount reaches 120 μg mL⁻¹, the fluorescence intensity is nearly quenched, indicating that ˙O₂⁻ can efficiently reacts with H₂S and effectively removes H₂S. The final oxidation products of H₂S were detected using ion chromatography (IC), as shown in Fig. 6d. Compared with the sulfate standard solution, the reaction system exhibits a peak at 5.0 min, indicating that the ˙O₂⁻ generated by Ce-MOF's OXD-like activity react with H₂S and ultimately form SO₄²⁻, resulting in the removal of H₂S. Additionally, the peak at 7.5 minutes corresponds to phosphates in the PB, and the peak at 3.4 minutes may be an intermediate product of H₂S oxidation.⁵⁸

Fig. 6 (a) Fluorescence spectra of JM-NO₂ (20 μM), JM-NO₂ + Ce-MOF (120 μg mL⁻¹), and JM-NO₂ + H₂S (300 μM). (b) Fluorescence spectra of JM-NO₂ (20 μM) + H₂S (300 μM) with varying concentrations of Ce-MOF. (c) Fluorescence intensity at 487 nm of JM-NO₂versus Ce-MOF level. (d) Ion chromatography (IC) under different reaction conditions (ex = 425 nm).

2.7. Ce-MOF's antibacterial properties

Ce-MOF's nanozyme activities of can generate ROS to achieve efficient bactericidal effects. However, POD-like activity requires the addition of exogenous hydrogen peroxide as a catalytic substrate, which greatly limits its practical application. Therefore, our subsequent studies utilized the Ce-MOF's OXD-like activity to eliminate bacteria in wastewater by the ˙O₂⁻ generated by the MOF. We evaluated the antimicrobial efficacy of Ce-MOF against representative Gram-negative (Escherichia coli, E. coli) and Gram-positive (Staphylococcus aureus, S. aureus) strains using standard plate count assays. As demonstrated in Fig. 7a, neither the cellulose acetate (CA) film nor the JM-NO₂ probe alone exhibits significant antibacterial effects compared to untreated controls. In striking contrast, Ce-MOF treatment significantly reduces colonies counts of both bacteria strains. Quantitative results of the plate counts are presented in Fig. 7b (E. coli) and Fig. 7c (S. aureus), respectively. Ce-MOF (at 1 mg mL⁻¹) achieves inactivation rates of 94.6% and 92.7% for E. coli and S. aureus, respectively. Thus, due to its OXD-like activity, Ce-MOF nanozyme can serve as potent and broad-spectrum bactericides.

Fig. 7 Antimicrobial performance of Ce-MOF. (a) Plate colony counts of bacteria (E. coli and S. aureus) under different conditions. Survival rates of (b) E. coli and (c) S. aureus under different conditions based on plate counts.

2.8. Application of the dual-film system in slaughterhouse and meat-processing wastewater treatment

The last step in wastewater treatment is disinfection. This process involves killing or removing harmful microorganisms to ensure the water is safe for reuse or discharge. Hence, we prepared the dual-film system for the last-step treatment of slaughterhouse and meat-processing wastewater, so as to achieve simultaneous H₂S scavenging, bacterial disinfection, and real-time, visual monitoring of H₂S levels before discharge. The schematic illustration of the dual-film platform for final- stage treatment of slaughterhouse wastewater is shown in Fig. 8a. Film 1 (the Ce-MOF-loaded CA film) and film 2 (JM-NO₂-loaded CA film) are mounted on the filtering cylinder, In the last-step treatment, the slaughter wastewater was filtered through film 1 and film 2 sequentially. Film 1 removes bacteria and H₂S, while film 2 enables visual monitoring of residual H₂S. As shown in Fig. 8a, water passes sequentially through film 1 (with varying Ce-MOF contents) and film 2. As shown in Fig. 8b, when water passes through film 1 containing different amounts of Ce-MOF (0–10 wt%) and then film 2, the color of film 2 clearly changes from pale green to brown under ambient light. While under 365 nm UV light irradiation, the green fluorescence intensity of film 2 gradually decreases, as the Ce-MOF content in film 1 increases. When the Ce-MOF content in film 1 reaches 10 wt%, the green fluorescence intensity of film 1 becomes almost invisible, indicating that the H₂S content in the treated water is extremely low. With 2.5 wt% of Ce-MOF in film 1, film 1 can achieve 99.7% bactericidal rate (Fig. 8c and e). This indicates that Ce-MOF has excellent bactericidal properties. Ce-MOF loading of 10 wt% on the cellulose acetate membrane simultaneously achieves high efficiency in both H₂S removal and a bactericidal rate of 99.8%. As shown in Fig. 8d, we used a smartphone to capture fluorescent color images of film 2 and digitized the images using a color scanning application. By analyzing the green-channel intensity (G-value) of the images, we could accurately reflect the extent of H₂S removal at different Ce-MOF concentrations in film 1. The stability of the films was evaluated under ambient storage conditions. For the JM-NO2 films, stability was assessed by periodically testing their H₂S detection performance. Each film exhibits bright and comparable fluorescence after reaction with H₂S (quantified by G-value analysis in Fig. S13), confirming excellent stability for H₂S sensing. For the Ce-MOF films, a dual-film testing approach was employed: NaHS solution (as H₂S donor) was first passed through the Ce-MOF film, and the residual H₂S was quantified downstream using a JM-NO2 film. The consistently weak fluorescence of the JM-NO2 films (Fig. S14) indicate stable and effective H₂S removal by the Ce-MOF films over time. These experimental results clearly demonstrate that this dual-film system provides effective bacterial disinfection, efficient H₂S removal, and real-time, visual feedback on effluent quality. It offers significant potential for deployment in industrial, municipal, and domestic wastewater treatment scenarios.

Fig. 8 (a) Schematic diagram of the dual-film for the last-step slaughter wastewater treatment so as to achieve H₂S scavenging, bacterial disinfection, and real-time, visual monitoring of H₂S levels before discharge. (b) Photographs of CA film with different Ce-MOF contents after wastewater treatment, and photographs of the CA film doped with JM-NO₂ after wastewater treatment under ambient light and the fluorescent changes under 365 nm UV light. (c) Plate colony counts after wastewater treatment using CA films with different Ce-MOF contents. (d) H₂S detection in the discharged water after treatment based on a smartphone and a graph showing the relationship between G-values of JM-NO₂-loaded film (film 2) and Ce-MOF-loaded film with different Ce-MOF contents (film 1). (e) Survival rates after wastewater treatment using CA films with different Ce-MOF contents, based on plate counts.

3. Conclusions

In summary, we have developed a cellulose acetate-based dual-film platform that simultaneously achieves bacterial disinfection, H₂S scavenging, and real-time fluorescent monitoring of H₂S in aqueous environments. The Ce-MOF-loaded film (film 1) exhibits potent peroxidase- and oxidase-like catalytic properties, enabling efficient ROS generation for broad-spectrum antibacterial action and oxidative degradation of H₂S. The JM-NO₂-doped film (film 2) provides sensitive and selective turn-on fluorescence and visible color changes in response to residual H₂S, allowing intuitive on-site monitoring. This integrated system demonstrates excellent performance under environmentally relevant conditions, with robust antibacterial efficacy and H₂S detection in complex media such as slaughterhouse wastewater. The modularity, scalability, and dual functionality of the platform make it a promising candidate for practical application in wastewater treatment and environmental monitoring, particularly in the final disinfection and decontamination stages before effluent discharge.

Author contributions

Xiangshan Lei: conceptualization, data curation, formal analysis, methodology, writing – original draft. Fang Zeng: conceptualization, formal analysis, supervision, funding acquisition, writing – reviewing and editing. Shuizhu Wu: conceptualization, resources, formal analysis, funding acquisition, supervision, writing – reviewing and editing.

Conflicts of interest

There are no conflicts to declare.

Data availability

The data supporting this article have been included as part of the supplementary information (SI). Supplementary information: Additional experimental procedures, scheme for synthetic route, ¹H/¹³C NMR and HR mass spectra, time-dependent fluorescent intensity, absorption spectra, size distribution, and the comparison table. See DOI: https://doi.org/10.1039/d5tc03098f.

Acknowledgements

This work was supported by NSFC (52373209 and 22274057), the Fund of Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates (2023B1212060003).

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