Singlet Oxygen Generation Efficiency Research Articles

Recent Advances in Thermally Activated Delayed Fluorescent Materials in Type II Photodynamic Therapy.

Photodynamic therapy (PDT) represents a novel, dual-stage cancer treatment approach that combines light energy and photosensitizers to destroy cancerous and precancerous cells through the generation of radicals (Type I) or singlet oxygen (Type II). Since the early 2010s, PDT has advanced significantly, with the focus shifting toward the exploration of molecules capable of thermally activated delayed fluorescence (TADF) as viable alternatives to traditional metallic complexes and organometallic compounds for producing the necessary active species. TADF molecules exhibit higher energy conversion efficiency, long-lived triplet excitons, tunable photophysical properties, and a small singlet-triplet energy gap, facilitating efficient intersystem crossing and enhanced singlet oxygen generation. As metal-free luminophores, they offer benefits such as reduced health risks, high structural flexibility, and biocompatibility, which can significantly enhance PDT treatment efficacy. Notably, in 2019, a pivotal shift occurred, with researchers concentrating their efforts on identifying and investing in potential molecules specifically for Type II PDT applications. This review presents the innovative use of materials characterized by closely spaced S1 and T1 orbitals, crucial for the efficient generation of singlet oxygen in PDT. Exploring these materials opens new avenues for enhancing the efficacy and specificity of PDT, offering promising for future cancer treatments.

Electronically regulated Mn-N site-loaded MXenes for highly efficient and selective singlet oxygen generation via PMS activation

In this study, a novel catalyst featuring dual-reactive sites of transition metal and nonmetal is presented, which modifies electronic polarization to enhance the selective generation of singlet oxygen (1O2), resulting in effective degradation of antibiotics. Using MXenes as a substrate, a structurally stable Mn-N@MXenes catalyst with controllable reactive sites was synthesized via a hydrothermal method by adjusting the content of the Mn-N precursor. The study revealed that the loading of Mn-N active sites changes the electronic structure and polarization of MXenes, resulting in asymmetric electronic structures and the generation of numerous oxygen vacancies. These characteristics enable the Mn-N@MXenes/PMS system to selectively generate 1O2 and superoxide radicals (O2∙-), with a synergistic index of 5.77. Compared to the MXenes/PMS system, the Mn-N@MXenes/PMS system significantly boosts the degradation efficiency of ofloxacin (OFL) from 71.32% to 96.07% under optimal conditions. The results demonstrate that during PMS activation, the catalyst maintains a nearly constant degradation rate after four cycles, exhibiting excellent stability and recyclability. Furthermore, the system shows superior performance and environmental adaptability in degrading actual water matrices and other pollutants. This study reveals electronic regulation mechanisms in catalyst design that facilitate pollutant degradation via both radical and non-radical pathways, offering new strategies for efficient degradation.

Enhancing Phototoxicity in BODIPY-Perylene Charge Transfer Dyads by Combined Iodination and Mesylation.

The uptake and phototoxicity of a family of BODIPY-perylene charge transfer dyads are compared in live cancer and non-cancer cell lines to evaluate their performance in imaging and photodynamic therapy (PDT). The impact of iodination and mesylation of the meso position of the compounds on their optical properties, cell uptake and toxicity are compared. Notably, across all derivatives the probes were minimally dark toxic up to 50 μM, (the maximum concentration tested), but exhibited outstanding phototoxicity with nanomolar IC50 values and impressive phototoxic indices (PI, ratio of dark IC50 to light IC50), with best performance for the mesylated iodinated derivative MB2PI, which had a PI of >218 and >8.9 in MCF-7 cells and tumour spheroids respectively. This is significantly higher than non-iodinated analogue MB2P in MCF-7 cells with an observed PI of >109 and slightly higher than MB2PI in spheroids with a PI of >8. This compound also showed interesting emission spectral variation with localisation that responded to stimulation of inflammation. Additional studies confirmed efficient singlet oxygen generation by the BODIPYs, suggesting a Type II mechanism of phototoxicity. Overall, the data indicates that combining charge transfer and iodination is an effective strategy for enhancing phototherapeutic capacity of BODIPY PS.

Artificial Light-Harvesting Systems with a Three-Step Sequential Energy Transfer Mechanism for Efficient Photocatalytic Minisci-Type Late-Stage Functionalization.

The natural process of photosynthesis involves a series of consecutive energy transfers, but achieving more steps of efficient energy transfer and photocatalytic organic conversion in artificial light-harvesting systems (ALHSs) continues to pose a significant challenge. In the present investigation, a range of ALHSs showcasing a sophisticated three-step energy transfer mechanism is designed, which are meticulously crafted using pillar[5]arene (WP[5]) and p-phenylenevinylene derivative (PPTPy), utilizing host-guest interactions as energy donors. Three distinct types of fluorescent dyes, namely Rhodamine B (RhB), Sulforhodamine 101 (SR101), and Cyanine 5 (Cy5), are employed as acceptors of energy. Starting from PPTPy-2WP[5], energy is sequentially transferred to RhB, SR101, and Cy5, successfully constructing a multi-step continuous energy transfer system with high energy transfer efficiency. More interestingly, as energy is progressively transferred, the efficiency of superoxide anion radical (O2 •-) generation gradually increased, while the efficiency of singlet oxygen (1O2) generation decreased, achieving the transformation from type II photosensitizer to type I photosensitizer. Furthermore, in order to fully utilize the energy harvested and reactive oxygen species (ROS) obtained, the ALHSs employ a multi-step sequential energy transfer process to enhance Minisci-type alkylation reactions with aldehydes through photocatalysis for late-stage functionalization in an aqueous environment, achieving a 91% yield.

Hypoxia-Active Iridium(III) Bis-terpyridine Complexes Bearing Oligothienyl Substituents: Synthesis, Photophysics, and Phototoxicity toward Cancer Cells.

In an effort to develop hypoxia-active iridium(III) complexes with long visible-light absorption, we synthesized and characterized five bis(terpyridine) Ir(III) complexes bearing oligothienyl substituents on one of the terpyridine ligands, i.e., nT-Ir (n = 0-4). The UV-vis absorption, emission, and transient absorption spectroscopy were employed to characterize the singlet and triplet excited states of these complexes and to explore the effects of varied number of thienyl units on the photophysical parameters of the complexes. In vitro photodynamic therapeutic activities of these complexes were assessed with respect to three melanoma cell lines (SKMEL28, A375, and B16F10) and two breast cancer cell lines (MDA-MB-231 and MCF-7) under normoxia (∼18.5% oxygen tension) and hypoxia (1% oxygen tension) upon broadband visible (400-700 nm), blue (453 nm), green (523 nm), and red (633 nm) light activation. It was revealed that the increased number of thienyl units bathochromically shifted the low-energy absorption bands to the green/orange spectral regions and the emission bands to the near-infrared (NIR) regions. The lowest triplet excited-state lifetimes and the singlet oxygen generation efficiency also increased from 0T to 2T substitution but decreased in 3T and 4T substitution. All complexes exhibited low dark cytotoxicity toward all cell lines, but 2T-Ir-4T-Ir manifested high photocytotoxicity for all cell lines upon visible, blue, and green light activation under normoxia, with 2T-Ir showing the strongest photocytotoxicity toward SKMEL28, MDA-MB-231, and MCF-7 cells, and 4T-Ir being the most photocytotoxic one for B16F10 and A375 cells. Singlet oxygen, superoxide anion radicals, and peroxynitrite anions were found to likely be involved in the photocytotoxicity exhibited by the complexes. 4T-Ir also showed strong photocytotoxicity upon red-light excitation toward all cell lines under normoxia and retained its photocytotoxicity under hypoxia toward all cell lines upon visible, blue, and green light excitation. The hypoxic activity of 4T-Ir along with its green to orange light absorption, NIR emission, and low dark cytotoxicity suggest its potential as a photosensitizer for photodynamic therapy applications.

Controlled Photooxidation via Singlet Oxygen Generation by Triplet Harvesting in a Heavy Atom Free Pure Organic Dithienylethene-Naphthalene Diimide.

Noninvasive control over the reversible generation of singlet oxygen (1O2) has found the enormous practical implications in the field of biomedical science. However, metal-free pure organic emitters, connected with a photoswitch, capable of generating "on-demand" 1O2 via triplet harvesting remain exceedingly rare; therefore, the utilization of these organic materials for the reversible control of singlet oxygen production remains at its infancy. Herein, an ambient triplet mediated emission in quinoline-dithienylethene (DTE)-core-substituted naphthalene diimide (cNDI) derivative is unveiled via delayed fluorescence. The quinoline-DTE-cNDI triad displayed enhanced photoswitching efficiency via double FRET mechanism. It was found to have direct utilization in controlled photosensitized organic transformations via efficient generation of singlet oxygen (yield ΦΔ~0.55 in DCM and 0.73 in methanol). The designed molecule exhibits a long-lived emission (τ∼1.1 μs) and very small singlet-triplet splitting (ΔEST) of 0.13 eV empowering it to display delayed fluorescence. Comprehensive steady state and time-resolved emission spectroscopy (TRES) analyses along with DFT calculations offer detailed understandings into the excited-state manifolds of organic compound and energy transfer (ET) pathways involved in 1O2 generation.

Graphene Quantum Dots from Natural Carbon Sources for Drug and Gene Delivery in Cancer Treatment

Cancer therapy is constantly evolving, with a growing emphasis on targeted and efficient treatment options. In this context, graphene quantum dots (GQDs) have emerged as promising agents for precise drug and gene delivery due to their unique attributes, such as high surface area, photoluminescence, up-conversion photoluminescence, and biocompatibility. GQDs can damage cancer cells and exhibit intrinsic photothermal conversion and singlet oxygen generation efficiency under specific light irradiation, enhancing their effectiveness. They serve as direct therapeutic agents and versatile drug delivery platforms capable of being easily functionalized with various targeting molecules and therapeutic agents. However, challenges such as achieving uniform size and morphology, precise bandgap engineering, and scalability, along with minimizing cytotoxicity and the environmental impact of their production, must be addressed. Additionally, there is a need for a more comprehensive understanding of cellular mechanisms and drug release processes, as well as improved purification methods. Integrating GQDs into existing drug delivery systems enhances the efficacy of traditional treatments, offering more efficient and less invasive options for cancer patients. This review highlights the transformative potential of GQDs in cancer therapy while acknowledging the challenges that researchers must overcome for broader application.

Spectroscopic insights into BSA-mediated deaggregation of m-THPC

Meta-tetra(hydroxyphenyl)chlorin (m-THPC) is among the most potent photosensitizers, known for its high singlet oxygen generation efficiency. However, its clinical effectiveness in photodynamic therapy (PDT) is compromised by its propensity to aggregate in aqueous solutions, adversely affecting its photophysical properties and therapeutic potential. A series of spectroscopic techniques, including UV-Vis absorption, fluorescence spectroscopy, and laser flash photolysis, revealed that m-THPC exhibits significant aggregation, particularly in MeOH-PBS mixtures with MeOH content below 30%. This aggregation adversely affects its photophysical properties leading to reduced fluorescence quantum yield and most importantly reducing its singlet oxygen quantum yield. This study introduces the use of bovine serum albumin (BSA) to counteract the aggregation of m-THPC, aiming to enhance its solubility, stability, and efficacy in physiological settings. Through advanced spectroscopic analyses we demonstrated that the m-THPC@BSA complex exhibits restored photophysical properties characteristic for monomeric form. Notably, the complex showed a significant restoration of the singlet oxygen quantum yield (ΦΔ = 0.21) compared to aggregated m-THPC. These results underscore the potential of BSA to preserve the monomeric form of m-THPC, mitigating aggregation-induced losses in singlet oxygen production. Our findings suggest that BSA-mediated delivery systems could play a crucial role in optimizing the clinical utility of hydrophobic photosensitizers like m-THPC.

Water-Soluble Rotaxane-Type Porphyrin Dyes as a Highly Membrane-Permeable and Durable Photosensitizer Suitable for Photodynamic Therapy.

Porphyrins have emerged as highly effective photosensitizers in the field of photodynamic therapy (PDT) because of their high singlet oxygen generation efficiency. However, most porphyrin derivatives do not have adequate water solubility and cell membrane permeability suitable for use in PDT. In addition, they frequently suffer from low durability under photoirradiation. Here, we propose rotaxane-type photosensitizers, in which a porphyrin axle is irreversibly encapsulated within cyclodextrins (CDs), to overcome the drawbacks of porphyrins for PDT. The rotaxane-type photosensitizers were synthesized in high yields by employing a cooperative capture strategy. The CD derivatives worked as a transparent shell to impart a porphyrin axle not only with water solubility but also with photostability. These rotaxanes showed higher cell membrane permeability and photoinduced cytotoxic abilities than talaporfin sodium, presently used as a clinical photosensitizer. The rotaxane-based photosensitizer could have potential for being ideal PDT drugs.

Spectral-luminescence properties of PV corrolazines with axial alkoxide ligands

New phosphorus(V) complexes of octaphenyl substituted tetrapyrazinocorrolazines (TPyzCA) containing in the axial positions alkoxide ligands [TPyzCAP(OC2H4X)2] (X = Pr, NMe2, OH) were synthesized using the one-pot procedure and effect of acid on their spectral luminescence and photochemical properties was studied. The presence of fused pyrazine rings increases the ability to bind axial ligands compared to benzo-fused corrolazine (TBzCA). Excited state properties are strongly dependent on the solvation effects. The effect of excited state quenching by photoinduced electron transfer is observed only for the dimethylaminoethoxide complex of TPyzCA in polar solvents, like THF or DMSO. Still, it is absent in dichloromethane, toluene, and for TBzCA derivatives. The hydroxyethoxide complex of TPyzCA and dimethylaminoethoxide complex of TBzCA exhibit efficient fluorescence and high singlet oxygen generation ability in DMSO solution.

Near-Infrared Heptamethine Cyanine Photosensitizers with Efficient Singlet Oxygen Generation for Anticancer Photodynamic Therapy.

Near-infrared photosensitizers are valuable tools to improve treatment depth in photodynamic therapy (PDT). However, their low singlet oxygen (1O2) generation ability, indicated by low 1O2 quantum yield, presents a formidable challenge for PDT. To overcome this challenge, the heptamethine cyanine was decorated with biocompatible S (Scy7) and Se (Secy7) atom. We observe that Secy7 exhibits a redshift in the main absorption to ~840 nm and an ultra-efficient 1O2 generation capacity. The emergence of a strong intramolecular charge transfer effect between the Se atom and polymethine chain considerably narrows the energy gap (0.51 eV), and the heavy atom effect of Se strengthens spin-orbit coupling (1.44 cm-1), both of which greatly improved the high triplet state yield (61 %), a state that determines the energy transfer to O2. Therefore, Secy7 demonstrated excellent 1O2 generation capacity, which is ~24.5-fold that of indocyanine green, ~8.2-fold that of IR780, and ~1.3-fold that of methylene blue under low-power-density 850 nm irradiation (5 mW cm-2). Secy7 exhibits considerable phototoxicity toward cancer cells buried under 12 mm of tissue. Nanoparticles formed by encapsulating Secy7 within amphiphilic polymers and lecithin, demonstrated promising antitumor and anti-pulmonary metastatic effects, exhibiting remarkable potential for advancing PDT in deep tissues.

Efficient generation of singlet oxygen (1O2) by CoP/Ni2P@NF for degradation of sulfamerazine through a heterogeneous electro-Fenton process at circumneutral pH

In electro-Fenton (EF), the development of a catalytic material with wide pH application range and high interference resistance is more suitable for practical wastewater treatment. In this study, the nanoneedle-shaped CoP/Ni2P heterostructure loaded onto a nickel foam substrate (CoP/Ni2P@NF) was successfully fabricated, which was used as a cathode material for heterogeneous electro-Fenton (Hetero-EF) to degrade sulfamerazine (SMR) at circumneutral pH. The SMR degradation efficiency within 90 min went to 100% and 87% at initial pH of 6.8 and 11, respectively. Experiments and theoretical calculations demonstrated that the heterostructure of CoP/Ni2P redistributed the interfacial charge and accelerated the electron transfer, resulting in different two-electron oxygen reduction (2e−ORR) selectivity and activity than CoP and Ni2P. The ion interference and complex water quality experiment exhibited that the degradation performance remained almost unchanged, showing better anti-interference ability and complex water quality applications. Through quenching experiments and EPR tests, it is confirmed that singlet oxygen (1O2) was the major reactive oxygen species (ROS) and 1O2 was converted from hydroxyl radical (·OH) adsorbed on the catalyst surface. This study provides an efficient catalyst for the application of Hetero-EF to remove organic compounds in complex water at circumneutral pH.

Generation of singlet oxygen inside living cells: correlation between phosphorescence decay lifetime, localization and outcome of photodynamic action

Photodynamic therapy (PDT) is a promising alternative treatment for localized lesions and infections, utilizing reactive oxygen species (ROS) generated by photosensitizers (PS) upon light activation. Singlet oxygen (1O2) is a key ROS responsible for photodynamic damage. However, the effectiveness of PS in biological systems may not correlate with the efficiency of singlet oxygen generation in homogeneous solutions. This study investigated singlet oxygen generation and its decay in various cellular microenvironments using liposome and ARPE-19 cell models. Rose Bengal (RB), methylene blue (MB), and protoporphyrin IX (PpIX) were employed as selected PS. Lifetimes of singlet oxygen generated by the selected photosensitizers in different cellular compartments varied, indicating different quenching rates with singlet oxygen. RB, located near cell membranes, exhibited the highest phototoxicity and lipid/protein peroxidation, followed by PpIX, while MB showed minimal cytotoxicity in similar conditions. Singlet oxygen decay lifetimes provide insights into PS localization and potential phototoxicity, highlighting the importance of the lipid microenvironment in PDT efficacy, providing useful screening method prior to in vivo applications.Graphical abstract

Near-infrared hemicyanine photosensitizer for targeted mitochondrial viscosity imaging and efficient photodynamic therapy

As a severe threat to human health, cancer has always been one of the most significant challenges facing the medical field. However, there is currently no effective technology or method to diagnose and treat cancer simultaneously. Therefore, developing a new approach that integrates diagnosis and treatment holds promise as a means of achieving personalized and precise cancer therapy. In this study, we developed a novel dual-functional near-infrared mitochondrial-targeted photosensitizer, Hcy-I, which is capable of simultaneously monitoring cellular viscosity and specifically targeting mitochondria for photodynamic therapy. Compared with traditional hemicyanine dyes, the introduction of iodine atoms in Hcy-I enhanced spin–orbit coupling (SOC) and promoted the intersystem crossing (ISC) rate, thereby increasing the efficiency of singlet oxygen (1O2) generation. In vitro experiments demonstrated that Hcy-I exhibited high sensitivity to viscosity variations and efficiently generated 1O2 under 638 nm laser irradiation, with an 1O2 quantum yield of up to 48.9 %. Cell experiments further revealed that this photosensitizer could effectively target mitochondria for photodynamic therapy, disrupting mitochondrial membrane potential and inducing cell death. When treated with Hcy-I at a concentration of 0.8 µM, the survival rate of HepG-2 cells was only 13 %. These results suggested that Hcy-I had the potential to integrate cancer diagnosis and treatment. The research not only promotes the development of photodynamic thereby technology, but also opens up new avenues for the diagnosis and treatment of cancer.

Cairo pentagon tessellated covalent organic frameworks with mcm topology for near-infrared phototherapy

Despite the prevalent of hexagonal, tetragonal, and triangular pore structures in two-dimensional covalent organic frameworks (2D COFs), the pentagonal pores remain conspicuously absent. We herein present the Cairo pentagonal tessellated COFs, achieved through precisely chosen geometry and metrics of the linkers, resulting in unprecedented mcm topology. In each pentagonal structure, porphyrin units create four uniform sides around 15.5 Å with 90° angles, while tetrabiphenyl unit establish a bottom edge about 11.6 Å with 120° angles, aligning precisely with the criteria of Cairo Pentagon. According to the narrow bandgap and strong near-infrared (NIR) absorbance, as-synthesized COFs exhibit the efficient singlet oxygen (1O2) generation and photothermal conversion, resulting in NIR photothermal combined photodynamic therapy to guide cancer cell apoptosis. Mechanistic studies reveal that the good 1O2 production capability upregulates intracellular lipid peroxidation, leading to glutathione depletion, low expression of glutathione peroxidase 4, and induction of ferroptosis. The implementation of pentagonal Cairo tessellations in this work provides a promising strategy for diversifying COFs with new topologies, along with multimodal NIR phototherapy.

Synthesis and evaluation of 5,15-diaryltetrabenzoporphyrins as photosensitizers for photo-diagnosis and photodynamic activity of tumors

Photodynamic therapy (PDT) is a well-established treatment modality, typically conducted with single-wavelength irradiation, which may not always be optimal for varying tumor locations and sizes. To address this, photosensitizers with absorption wavelengths ranging from 550 to 760 nm are being explored. Herein, a series of 5,15-diaryltetrabenzoporphyrins (Ar2TBPs) were synthesized. All compounds displayed obvious absorption at 550–700 nm (especially at ∼668 nm), intense fluorescence, efficient generation of singlet oxygen and good photodynamic antitumor effects. Notably, compound I3 (5,15-bis[(4-carboxymethoxy)phenyl]tetrabenzoporphyrin) showed excellent cytotoxicity against Eca-109 cell line upon red light irradiation, with an IC50 value of 0.45 μM, and phototherapeutic index of 25.8. Flow cytometry revealed that I3 could induce distinct cell apoptosis. In vivo studies revealed that compound I3 selectively accumulated at tumor site and exhibited outstanding PDT effect with antitumor activity under single-time administration and light irradiation, and revealed more efficiency than the clinical photosensitizer Verteporfin. These findings underscore the considerable promise of I3 as a robust theranostic agent, offering capabilities in real-time fluorescence imaging and serving as a potent photosensitizer for personalized and precise photodynamic therapy of tumors.

Chemiexcitation-Triggered Photosensitizer Activation for Photooxidation of Aβ1-42 Aggregates.

Oxidative degradation of the pathogenic amyloid-β-peptide (Aβ) aggregation is an effective and promising method to treat Alzheimer's disease under light irradiation. However, the limited penetration of external light sources into deep tissues has hindered the development of this treatment. Therefore, we have designed an unprecedented chemiluminescence-initiated photodynamic therapy system to replace external laser irradiation, primarily composed of d-glucose-based polyoxalate (G-poly(oxalate)), the novel photosensitizer (BD-Se-QM), and bis [2,4,5-trichloro-6-(pentoxy-carbonyl) phenyl] ester. BD-Se-QM possesses excellent singlet oxygen (1O2) generation efficiency and the ability to photooxidize Aβ1-42 aggregates under white light. G-poly(oxalate) not only helps the nanosystem to cross the blood-brain barrier but also has sufficient oxalate ester groups to significantly enhance the efficiency of chemiluminescence resonance energy transfer. The oxalate ester groups in BD-Se-QM/NPs can chemically react with H2O2 to produce high-energy intermediates that activate BD-Se-QM, which can generate 1O2 to inhibit Aβ1-42 aggregates and also promote microglial uptake of Aβ1-42, reducing the Aβ1-42-induced neurotoxicity. The chemically stimulated nanoplatform not only solves the drug delivery problem but also eliminates the need for external light sources. We anticipate that this chemically excited nanosystem could also be used for targeted delivery of other small molecule drugs.

Efficient generation of singlet oxygen on Fe2O3/MoO3 Z-type heterojunction for removal of ciprofloxacin from water via photo-electro-Fenton-like system

Singlet oxygen (1O2), a typical reactive oxygen species (ROS) with selective oxidation properties, holds great application prospects in water environment treatment. However, the 1O2 generation mechanism in photo-electro-Fenton-like (PEF-like) system for water purification is still unclear. In this study, we developed a Fe2O3/MoO3 (abbreviated as FMO-x) Z-type heterojunction and achieved efficient degradation of ciprofloxacin (CIP). In-situ irradiated XPS, EPR, and DFT calculations confirmed that the coupling interface of FMO-1 Z-type heterojunction effectively enhanced the charge separation and transfer process, thus generating various ROS (1O2, ·O2−, ·OH and H2O2). In the FMO-1-PEF-like system, H2O2 was generated in-situ through 2e− ORR. In addition, ROS quantitative experiments showed that the yield of 1O2, ·O2− and ·OH was 29.76, 92.54 and 1.09 μmol·L−1 in 60 min, respectively. EPR and XPS results indicated two potential routes for the 1O2 generation: the reaction between ·O2− and Fe3+ and between ·O2− and H2O2. In the FMO-1-PEF-like system, the removal rate of CIP was 97.10 % in 60 min, and the kinetic constant was 0.0626 min−1, which was 1.32 and 1.55 times higher than that of Fe2O3 and MoO3. This work developed a method using Fe2O3/MoO3 Z-type heterojunction to understand the mechanism of the 1O2 generation in the PEF-like system.

Enhancing Emerging Pollutant Removal in Industrial Wastewater: Validation of a Photocatalysis Technology in Agri-Food Industry Effluents

Emerging pollutants in wastewater pose significant risks to human health and wildlife, particularly due to their persistence in treated effluents from WWTPs. Very recent research has focused on developing new techniques based on advanced oxidation processes using inorganic and organic photocatalysts for treating polluted effluents under visible light. This study investigates a pesticide-removal system utilizing heterogeneous photoactive polymeric materials P2, P3, and P4. These materials, engineered as hydrophilic polymeric microparticles and functionalized with Rose Bengal, have demonstrated efficient singlet oxygen generation and first-order kinetics in the degradation of AHMPD, a pyrimidine fungicide. Given that most studies in the literature have concentrated on urban WWTPs, with less emphasis on industrial wastewater treatment, this research focused on real water samples from the effluent of an industrial WWTP in the agri-food sector, which processes large volumes of citrus and where high concentrations of AHMPD and other pesticides were detected at certain times of the year. The degradation potential of photoactive materials P3 and P4 was evaluated, achieving removal rates of AHMPD up to 85% under conditions of pH = 11 with 48 h of exposure to visible light.

Efficient generation of singlet oxygen for photocatalytic degradation of antibiotics: Synergistic effects of Fe spin state reduction and energy transfer

Singlet oxygen (1O2) exhibits excellent degradation performance and stability in removing antibiotics from an aqueous environment. However, its production is limited by free radical competition. This study proposed a photocatalytic method employing ferrihydrite (Fh) as the base, coated with K-doped g-C3N4 and modified by AgCl (Ag/AgCl), leading to the KC3N4/AgCl/Fh composite for efficient 1O2 production. Compared with Fh, the loading of KC3N4 reduced Fe (III) spin, facilitating the rapid conversion of H2O2 to 1O2. The addition of Ag promoted the intersystem crossing process, decreasing the singlet-triplet energy gap from 0.0708 to 0.0458 eV, thereby effectively generating more triplet excitons to convert O2 into 1O2 in a targeted manner. The KC3N4/AgCl/Fh achieved a degradation rate of 98.10 % for enrofloxacin in 30 min, showing high effectiveness and stability. This work suggests a new way to create Fh-based photocatalysts for the efficient production of 1O2.