Dual-Responsive and ROS-Augmented Nanoplatform for Chemo/Photodynamic/Chemodynamic Combination Therapy of Triple Negative Breast Cancer.

Integrating chemodynamic therapy (CDT) and photodynamic therapy (PDT) into one nanoplatform can produce much more reactive oxygen species (ROS) for tumor therapy. Nevertheless, it is still a great challenge to selectively generate sufficient ROS in tumor regions. Meanwhile, CDT and PDT are restricted by insufficient H2O2 content in the tumor as well as by the limited tumor tissue penetration of the light source. In this study, a smart pH/ROS-responsive nanoplatform, Fe2+@UCM-BBD, is rationally designed for tumor combination therapy. The acidic microenvironment can induce the pH-responsive release of doxorubicin (DOX), which can induce tumor apoptosis through DNA damage. Beyond that, DOX can promote the production of H2O2, providing sufficient materials for CDT. Of note, upconversion nanoparticles at the core can convert the 980 nm light to red and green light, which are used to activate Ce6 to produce singlet oxygen (1O2) and achieve upconversion luminescence imaging, respectively. Then, the ROS-responsive linker bis-(alkylthio)alkene is cleaved by 1O2, resulting in the release of Fenton reagent (Fe2+) to realize CDT. Taken together, Fe2+@UCM-BBD exhibits on-demand therapeutic reagent release capability, excellent biocompatibility, and remarkable tumor inhibition ability via synergistic chemo/photodynamic/chemodynamic combination therapy.

Effect of High Static Magnetic Fields on Biological Activities and Iron Metabolism in MLO-Y4 Osteocyte-like Cells.

There are numerous studies that investigate the effects of static magnetic fields (SMFs) on osteoblasts and osteoclasts. However, although osteocytes are the most abundant cell type in bone tissue, there are few studies on the biological effects of osteocytes under magnetic fields. Iron is a necessary microelement that is involved in numerous life activities in cells. Studies have shown that high static magnetic fields (HiSMF) can regulate cellular iron metabolism. To illustrate the effect of HiSMF on activities of osteocytes, and whether iron is involved in this process, HiSMF of 16 tesla (T) was used, and the changes in cellular morphology, cytoskeleton, function-related protein expression, secretion of various cytokines, and iron metabolism in osteocytes under HiSMF were studied. In addition, the biological effects of HiSMF combined with iron preparation and iron chelator on osteocytes were also investigated. The results showed that HiSMF promoted cellular viability, decreased apoptosis, increased the fractal dimension of the cytoskeleton, altered the secretion of cytokines, and increased iron levels in osteocytes. Moreover, it was found that the biological effects of osteocytes under HiSMF are attenuated or enhanced by treatment with a certain concentration of iron. These data suggest that HiSMF-regulated cellular iron metabolism may be involved in altering the biological effects of osteocytes under HiSMF exposure.

A rational study of the influence of Mn2+-insertion in Prussian blue nanoparticles on their photothermal properties.

We investigated a series of Mn2+-Prussian blue (PB) nanoparticles NazMnxFe1-x[Fe(CN)6]1-y□y·nH2O of similar size, surface state and cubic morphology with various amounts of Mn2+ synthesized through a one step self-assembly reaction. We demonstrated by a combined experimental-theoretical approach that during the synthesis, Mn2+ substituted Fe3+ up to a Mn/Na-Mn-Fe ratio of 32 at% in the PB structure, while for higher amounts, the Mn2[Fe(CN)6] analogue is obtained. For comparison, the post-synthetic insertion of Mn2+ in PB nanoparticles was also investigated and completed with Monte-Carlo simulations to probe the plausible adsorption sites. The photothermal conversion efficiency (η) of selected samples was determined and showed a clear dependence on the Mn2+amount with a maximum efficiency for a Mn/Na-Mn-Fe ratio of 10 at% associated with a dependence on the nanoparticle concentration. Evaluation of the in vitro photothermal properties of these nanoparticles performed on triple negative human breast adenocarcinoma (MDA-MB-231) cells by using continuous and pulsed laser irradiation confirm their excellent PTT efficiency permitting low dose use.

Ultrasmall Zwitterionic Polypeptide-Coordinated Nanohybrids for Highly Efficient Cancer Photothermal Ferrotherapy.

Ferroptosis therapy (FT) based on the Fenton reaction of ferrous nanoparticles has been becoming a unique strategy for cancer treatment; however, current ferrous nanoparticles suffer from slower Fenton reaction kinetics, lower ferroptosis efficacy, and long-term toxicity, so it is urgent to construct biocompatible ferrous nanomaterials with highly efficient Fenton reaction activity for cancer FT. Inspired by single-atom catalysis and size-determined tumor penetration, we conceived an innovative strategy for constructing ultrasmall zwitterionic polypeptide-coordinated nanohybrids of PCGA@FeNP with about 6 nm by utilizing thiol/hydroxyl-iron cooperative coordination chemistry. The ultrasmall size, unsaturated ferrous coordination, and intracellular acidic pH could accelerate the Fenton reaction, thus boosting the efficacy of ferroptosis. Moreover, those coordinated nanohybrids exhibited prominent photothermia with 59.5% conversion efficiency, further accelerating the Fenton reaction and inducing a synergistic effect between FT and photothermal therapy (PTT). In vitro and in vivo GPX-4 expression ascertained that PCGA@FeNP indeed induced effective FT and synergistic FT-PTT. Remarkably, in vivo FT-PTT completely ablated 4T1 solid tumors by one treatment, presenting outstanding and synergistic antitumor efficacy via the photothermia-boosted ferroptosis and apoptosis pathways. This work supplies a practicable strategy to fabricate ultrasmall zwitterionic coordination nanohybrids for highly efficient cancer FT and FT-PTT theranostics with potential clinical transitions.

Iron Self-Boosting Polymer Nanoenzyme for Low-Temperature Photothermal-Enhanced Ferrotherapy.

In this work, an iron self-boosting polymer nanoenzyme was prepared by using pyrrole-3-carboxylic acid as a monomer and iron as an oxidizing agent via a simple and one-step method [hereafter referred to as FePPy nanoparticles (NPs)]. In fact, researchers previously paid negligible attention on the iron element during the polymerization reaction of polypyrrole, thus the intrinsically catalytic functions and enzymatic activities of the high iron content (wt %: 21.11%) are ignored and not fully explored. As expected, results demonstrate that the as-synthesized FePPy NPs can decompose H2O2 to generate hydroxyl radicals (•OH) which exhibit enzyme characteristics, further inducing a nonapoptotic ferroptosis pathway. Moreover, the nanoenzyme shows impressive photothermal properties which can accelerate the Fenton reactions to enhance ferroptosis. The combined photothermal and ferroptosis therapy of FePPy NPs was found to have high efficacy. With the properties of easy synthesis, high efficacy, and good biocompatibility, the FePPy NPs are considered as potential agents for cancer treatments.

Paraquat degradation by photocatalysis: experimental desing and optimization.

This study describes the experimental design and optimization of application TiO2 catalysts doped with 0.5, 1, 1.5, 2.0% of Fe. The catalysts were prepared using the impregnation method applied in Paraquat herbicide degradation. The catalysts were characterized by the following techniques: specific surface area and volume, mean pore diameter (BET method), scanning electron microscopy and photoacoustic spectroscopy. The characterization presented results indicating that both calcination temperature and the increase nominal metallic load affected by the structure of catalysts, changing the textural properties, as well as the band gap. The catalyst that presented the best herbicide removal percentage was TiO2 calcined at 773 K with removal of 90.2%. However, according to the experimental design and optimization, both variables (calcination temperature and Fe percentage) are significant in the process. In addition, a positive effect was found in the interaction between the two variables. The values show that a third order kinetic model better described the Paraquat photocatalytic degradation.

Hetero-Core-Shell BiNS-Fe@Fe as a Potential Theranostic Nanoplatform for Multimodal Imaging-Guided Simultaneous Photothermal-Photodynamic and Chemodynamic Treatment.

Photothermal/photodynamic therapy (PTT/PDT) and synergistic therapeutic strategies are often sought after, owing to their low side effects and minimal invasiveness compared to chemotherapy and surgical treatments. However, in spite of the development of the most PTT/PDT materials with good tumor-inhibitory effect, there are some disadvantages of photosensitizers and photothermal agents, such as low stability and low photonic efficiency, which greatly limit their further application. Therefore, in this study, a novel bismuth-based hetero-core-shell semiconductor nanomaterial BiNS-Fe@Fe with good photonic stability and synergistic theranostic functions was designed. On the one hand, BiNS-Fe@Fe with a high atomic number exhibits good X-ray absorption, enhanced magnetic resonance (MR) T2-weighted imaging, and strong photoacoustic imaging (PAI) signals. In addition, the hetero-core-shell provides a strong barrier to decline the recombination of electron-hole pairs, inducing the generation of a large amount of reactive oxygen species (ROS) when irradiated with visible-NIR light. Meanwhile, a Fenton reaction can further increase ROS generation in the tumor microenvironment. Furthermore, an outstanding chemodynamic therapeutic potential was determined for this material. In particular, a high photothermal conversion efficiency (η = 37.9%) is of significance and could be achieved by manipulating surface decoration with Fe, which results in tumor ablation. In summary, BiNS-Fe@Fe could achieve remarkable utilization of ROS, high photothermal conversion law, and good chemodynamic activity, which highlight the multimodal theranostic potential strategies of tumors, providing a potential viewpoint for theranostic applications of tumors.

Dual-Modal FexCuySe and Upconversion Nanoparticle Assemblies for Intracellular MicroRNA-21 Detection.

In situ quantification and imaging of low-level intracellular microRNAs (miRs) are important areas in biosensor research. Herein, DNA-driven FexCuySe@upconversion nanoparticle (UCNP) core@satellite nanostructures were developed to probe microRNA-21 (miR-21). FexCuySe@UCNP probes displayed dual signals: upconversion luminescence (UCL) and magnetic resonance imaging (MRI). In the presence of miR-21, the luminescence signal was restored and the T2 value was significantly increased because of dissociation of UCNPs from the assemblies. There was a good linear relationship between the dual signals and the expression levels of miR-21 in the range of 0.035-31.824 amol/ngRNA. The limit of detection (LOD) was 0.0058 amol/ngRNA for the luminescence intensity and 0.0182 amol/ngRNA for the MRI signal. This method opens a new avenue for intracellular miR-21 detection with high sensitivity and specificity.

A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity.

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl2 (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t1/2) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl2 complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.

Rapid degradation of dimethoate and simultaneous removal of total phosphorus by acid-activated Fe(VI) under simulated sunlight.

Ferrate (Fe(VI)) is usually effective for oxidizing a variety of organic pollutants within a few seconds, but some recalcitrant asorganophosphorus pesticides such as dimethoate require higher dose of Fe(VI) and inorganic phosphorus produced by mineralization is difficult to remove. In this study, acid-activated ferrate (Fe(VI)) was firstly used to degrade organophosphorus pesticides dimethoate and simultaneously remove total phosphorus (TP) from solution under simulated sunlight. At a Fe(VI):dimethoate molar radio of 15:1, dimethoate was almost completely removed within 20 min and 47% of TP in the solution was removed by the reduction product of Fe(VI) within 240 min. Electron paramagnetic resonance (EPR) and terephthalic acid (TA) fluorescence experiments showed that •OH radicals were continuously generated in the system, and •OH formation pathway was proposed. Importantly, the involvement of •OH in acid-activated Fe(VI) process was confirmed for the first time by EPR. In the acid-activated Fe(VI)/simulated sunlight system, the removal of dimethoate and TP gradually increased with the decrement of activation pH, whereas the increase of molar ratio of Fe(VI):dimethoate enhanced the removal of dimethoate and TP. The addition of inorganic anions (HCO3- and NO2-) had obvious inhibitory effects on dimethoate and TP removal. Eight degradation products including O,O,S-trimethylphosphorothiate, omethoate and 2-S-methyl-(N-methyl) acetamide were determined by gas chromatography mass spectrometry (GC-MS) analysis, and two possible degradation pathways were proposed. The insights gained from this study open a new avenue to simultaneously degrade and remove organic contaminants.

Structure of a Zinc Porphyrin-Substituted Bacterioferritin and Photophysical Properties of Iron Reduction.

The iron storage protein bacterioferritin (Bfr) binds up to 12 hemes b at specific sites in its protein shell. The heme b can be substituted with the photosensitizer Zn(II)-protoporphyrin IX (ZnPP), and photosensitized reductive iron release from the ferric oxyhydroxide {[FeO(OH)]n} core inside the ZnPP-Bfr protein shell was demonstrated [Cioloboc, D., et al. (2018) Biomacromolecules 19, 178-187]. This report describes the X-ray crystal structure of ZnPP-Bfr and the effects of loaded iron on the photophysical properties of the ZnPP. The crystal structure of ZnPP-Bfr shows a unique six-coordinate zinc in the ZnPP with two axial methionine sulfur ligands. Steady state and transient ultraviolet-visible absorption and luminescence spectroscopies show that irradiation with light overlapping the Soret absorption causes oxidation of ZnPP to the cation radical ZnPP•+ only when the ZnPP-Bfr is loaded with [FeO(OH)]n. Femtosecond transient absorption spectroscopy shows that this photooxidation occurs from the singlet excited state (1ZnPP*) on the picosecond time scale and is consistent with two oxidizing populations of Fe3+, which do not appear to involve the ferroxidase center iron. We propose that [FeO(OH)]n clusters at or near the inner surface of the protein shell are responsible for ZnPP photooxidation. Hopping of the photoinjected electrons through the [FeO(OH)]n would effectively cause migration of Fe2+ through the inner cavity to pores where it exits the protein. Reductive iron mobilization is presumed to be a physiological function of Bfrs. The phototriggered Fe3+ reduction could be used to identify the sites of iron mobilization within the Bfr protein shell.

Physical assessments of termites (Termitidae) under 2.45 GHz microwave irradiation.

Demands for chemical-free treatments for controlling insect pests are increasing worldwide. One such treatment is microwave heating; however, two critical issues arise when using microwaves as a heat source: intensive labor and excessive energy-consumption. Optimization is thus required to reduce energy consumption while effectively killing insects. Currently, the lethal effect of microwaves on insects is considered to be due to the temperature of the irradiated materials. This study examines how the conditions of irradiation, such as resonance or traveling mode, changed the conversion of electromagnetic energy into heat when 2.45 GHz microwaves penetrated the body of the termite, C. formosanus. Our results indicated that it is possible to heat and kill termites with microwaves under resonance condition. Termites were however found to be very tolerant to microwave irradiation as the permittivity of the insect was low compared with other reported insects and plants. Electron spin resonance revealed that termites contained several paramagnetic substances in their bodies, such as Fe3+, Cu2+, Mn2+, and organic radicals. Interestingly, irradiation with traveling microwaves hardly produced heat, but increased the organic radicals in termite bodies indicating non-thermal effects of microwaves.

High selectivity and effectiveness for removal of tetracycline and its related drug resistance in food wastewater through schwertmannite/graphene oxide catalyzed photo-Fenton-like oxidation.

Selectively and effectively for removal of tetracycline (TC) and its related antibiotic resistance gene from food wastewater matrix with high-salt and high COD characteristics is highly desirable. In this work, novel schwertmannite/graphene oxide (SCH/GO) nanocomposites were synthesized through a facile oxidation-coprecipitation method. The SCH/GO nanocomposites were characterized by TEM, XRD, BET, PL, DRS, XPS and FTIR. In the presence of 1 mM H2O2, the SCH/GO catalyzed Fenton-like oxidation can thoroughly degrade TC under visible light irradiation, even under nature sunlight, whose second-order kinetic rate constant was about 15 times higher than that of pure SCH. SCH/GO was capable of highly selectively capturing and effectively degrading TC in the presence of similar concentration of Cl-, NO3-, SO42- and PO43- with that of food wastewater, even at organic matters concentration of 12.5 times than that of TC. At the same time, the removal of total organic carbon (TOC) and chemical oxygen demand (COD) in aforementioned food wastewater in SCH/GO+H2O2+Vis system reached 27.3 % and 34.5 % after 60 min, respectively. The inhibition zone experiments authenticated that the removal of drug resistance of bacteria by TC degradation intermediates can be achieved very well without producing secondary contamination in this system.

Rapid degradation of tetracycline hydrochloride by heterogeneous photocatalysis coupling persulfate oxidation with MIL-53(Fe) under visible light irradiation.

This work demonstrates a facile route to assemble MIL-53(Fe) by solvothermal method. Sulfate radical-based advanced oxidation processes (SR-AOPs) coupling with photocatalysis based on MIL-53(Fe) were investigated under visible light. The catalytic effect of MIL-53(Fe) for the degradation of tetracycline hydrochloride (TC-HCl) was systematically studied, as well as the reusability of the catalyst and the effect of operating parameters. The results indicated that 99.7 % of TC (300 mg/L) could be degraded within 80 min in the SR-AOPs coupling with photocatalysis processes, as compared to 71.4 % for the SR-AOPs and only 17.1 % for the photocatalysis. The trapping experiments and electron spin-resonance spectroscopy (ESR) showed the photogenerated electrons of MIL-53(Fe) under visible light irritation were trapped by persulfate to generated sulfate radicals which effectively suppressed the recombination of photogenerated carriers. And also, the SO4- could be formed by the conversion between Fe (Ⅲ) and Fe (Ⅱ) in MIL-53(Fe). Moreover, OH and O2- generated by the reaction increased significantly due to the increase of SO4- which generated more OH and reduced photogenerated carrier recombination respectively. Thus, the degradation efficiency of TC-HCl was improved. Furthermore, the degradation pathway for TC-HCl was proposed using the theoretical calculations and liquid chromatography coupled with mass spectrometry.

Enhancement of ionizing radiation-induced catalytic degradation of antibiotics using Fe/C nanomaterials derived from Fe-based MOFs.

In present work, we studied a novel Fe/C nanomaterial fabricated using Fe-based metal organic frameworks (MOFs) as precursors through thermal pyrolysis to catalyze gamma irradiation-induced degradation of antibiotics, cephalosporin C (CEP-C) and sulfamethazine (SMT) in aqueous solution. The MOFs-derived Fe/C nanomaterials (DMOFs) had the regular octahedrons structure of MOFs and contained element C, Fe and O, while Fe° with a fraction of Fe3O4 and Fe2O3 were identified. Results showed that DMOFs addition could accelerate the generation of OH during gamma irradiation, while the intermediates of bonds cleavages of antibiotic molecules and OH addition were identified. DMOFs were more effective to improve the decomposition of antibiotic having the higher adsorption capacity like SMT. The degradation rate of CEP-C and SMT increased by 1.3 times and 1.8 times, and TOC reduction at 1.0 kGy reached 42 % and 51 %, respectively by gamma/DMOFs treatment, while only 20.2 % (CEP-C) and 4.5 % (SMT) of TOC reduction were obtained by γ-irradiation alone. The crystal structure, functional groups and magnetism of DMOFs changed slightly after gamma irradiation, which made it possible to be reused. DMOFs were promising to enhance the degradation of antibiotics during gamma irradiation.

In situ photoreduction of structural Fe(III) in a metal-organic framework for peroxydisulfate activation and efficient removal of antibiotics in real wastewater.

Structural Fe(III) is widely found in various coordination complexes and inorganic compounds. In this work, a typical Fe-based metal organic framework (MOF) (viz. MIL-100(Fe)) was chosen as an example in the activation of peroxydisulfate (PDS) for the removal of antibiotic pollutants. Interestingly, an auto-acceleration effect was observed in the process of MIL-100(Fe) activating PDS aided by visible light irradiation. Compared to the processes with MIL-100(Fe)-activated PDS alone and the photo-activated PDS alone, the degradation efficiency of sulfamethoxazole (SMX) obtained in the visible light assisted PDS activation by MIL-100(Fe) process was enhanced by 2.1 and 5.6 times, respectively. Therein, the photogenerated electrons from MIL-100(Fe) carried out an in situ reduction of the surface structural Fe(III) to form Fe(II), which in turn significantly improved the PDS activation efficiency in the generation of ·OH and O2-· radicals for the removal of SMX. The degradation pathways of SMX were deduced based on the experimental results and theoretical calculations. Acute toxicity estimation indicated the formation of less toxic products after the treatment of SMX. Additionally, degradation of five antibiotics in the real wastewater were investigated to further confirm the advantages of such in situ photoreduced structural Fe(III) in MOFs to activate the PDS process.

Smart, Photothermally Activated, Antibacterial Surfaces with Thermally Triggered Bacteria-Releasing Properties.

The development of effective antibacterial surfaces to prevent the attachment of pathogenic bacteria and subsequent bacterial colonization and biofilm formation is critically important for medical devices and public hygiene products. In the work reported herein, a smart antibacterial hybrid film based on tannic acid/Fe3+ ion (TA/Fe) complex and poly(N-isopropylacrylamide) (PNIPAAm) is deposited on diverse substrates. This surface is shown to have bacteria-killing and bacteria-releasing properties based on, respectively, near-infrared photothermal activation and subsequent cooling. The TA/Fe complex has three roles in this system: (i) as a universal adhesive "anchor" for surface modification, (ii) as a high-efficiency photothermal agent for ablation of attached bacteria (including multidrug resistant bacteria), and (iii) as a robust linker for immobilization of NH2-terminated PNIPAAm via either Michael addition or Schiff base formation. Moreover, because of the thermoresponsive properties of the immobilized PNIPAAm, almost all of the killed bacteria and other debris can be removed from the surface simply by lowering the temperature. It is shown that this hybrid film can maintain good antibacterial performance after being used for multiple "kill-and-release" cycles and can be applied to various substrates regardless of surface chemistry or topography, thus providing a broadly applicable, simple, and reliable solution to the problems associated with surface-attached bacteria in various healthcare applications.

Two-photon excited fluorescent silica nanoparticles loaded with iron(II) as a probe for determination and imaging of hydrogen peroxide in living cells.

A method is described for determination and optical imaging of hydrogen peroxide (H2O2) by using the two-photon (TP) excited fluorescence of silica (SiO2) nanoparticles containing Fe(II) ions. In the presence of H2O2, hydroxyl radicals (•OH) are produced via the Fenton reaction. This leads to quenching of the green fluorescence of a TP-excitable organic dye loaded into the SiO2NPs. Fluorescence is excited at 370 nm and has an emission peaking at 447 nm. The degree of quenching increases linearly in the 2.5 to 100 µM H2O2 concentration range. The nanoprobe is highly selective and sensitive, with a detection limit of 336 nM. The nanoprobe is biocompatible and was successfully used to image changes in the H2O2 concentration in HeLa cells via TP fluorescence imaging. Graphical abstractSchematic rpresentation of the detection of H2O2 by using the two-photon excited fluorescence of silica nanoparticles (TP-SiO2NPs) containing Fe2+. H2O2 triggers the Fenton reaction to produce hydroxyl radicals (•OH), which quench the green fluorescence of the SiO2NPs.

Transformation pathway and toxicity assessment of malathion in aqueous solution during UV photolysis and photocatalysis.

In drinking water treatment, complete mineralization of organophosphorus pesticides (OPPs) by UV-based advanced oxidation processes (UV AOPs) is rarely achieved. The formation of intermediate oxidation byproducts would likely have some profound effects on toxicity of the reaction solutions. This study investigated the intermediate oxidation byproducts, transformation pathway and toxicity of malathion solutions during the treatment processes of UV alone, UV/H2O2, UV/TiO2 and UV/Fenton. The main intermediate oxidation byproducts were derived using ultra-performance liquid chromatography - electrospray - time-of-flight mass spectrometry. Thereby the transformation pathway for each of these treatment processes was proposed. The results indicate that in UV photolysis, the transformation pathway of malathion proceeded initially via cleavage of the phosphorus-sulfur bonds while in photocatalysis, the desulfurization from a PS bond to a PO bond was the primary degradation pathway. Interestingly, only in the UV/TiO2 process a small fraction of malathion was found decomposed via a demethylation reaction. At the same time, a toxicity assessment of the treated solutions was conducted by both luminescence inhibition of Vibrio fischeri and inhibition of acetylcholinesterase (AChE). It was found that after UV AOP treatment, the toxicity of the malathion aqueous solution increased sharply. In contrast, no increase in toxicity was observed for the malathion aqueous solution after UV alone treatment. This study demonstrates that the high removal efficiency achieved by OPPs does not imply that detoxification of the water solution has been achieved. On the contrary, the toxicity of the treated solutions by OPPs may be increased significantly depending on the selected treatment processes.

Promoting sun light-induced photocatalytic degradation of toxic phenols by efficient and stable double metal cyanide nanocubes.

Aromatic substituted phenols and their by-products discharged from numerous industries are of environmental concern due to their toxic, carcinogenic, recalcitrant, and bioaccumulating properties. Therefore, their complete removal from waters by low-cost, efficient, environmentally friendly nanomaterial-based treatment techniques is desirable. Double metal cyanide complexes (DMCC) are the extremely useful heterogeneous and recoverable catalyst. Hence, green route has been developed for several DMCC and their photocatalytic efficiency was evaluated for degradation of toxic phenols. Herein, nanocubes for hexacyanocobaltate of iron (FeHCC ~ 200 nm), nickel (NiHCC < 10 nm), and zinc (ZnHCC ~ 500 nm) were synthesized after employing Aegle marmelos. Subsequently, at neutral pH and sunlight irradiation, 15 mg of catalysts were able to degrade the maximum extent of phenols (1 × 10-4 M) in the order: 3-aminophenol (96% ZnHCC > 94% FeHCC > 93% NiHCC) > phenol (94% ZnHCC > 92% FeHCC > 91% NiHCC) > 2,4-DNP (92% ZnHCC > 91% FeHCC > 90% NiHCC). This is attributed to highest basicity of 3-aminophenol containing excess of free electrons. Highest catalytic potential of ZnHCC (Xm = 0.54-0.43 mg/g) is because of its highest surface area and negative zeta potential along with sharp morphology and crystallinity. Adsorption of phenols over catalyst was statistically significant with Langmuir isotherms (R2 ≥ 0.96; p value ≤ 0.05). Small and non-toxic by-products like oxalic acid, benzoquinone, (Z)-hex-3-enedioic acid, (Z)-but-2-enal, and (Z)-4-oxobut-2-enoic acid were identified in GC-MS. Degradation modes involving hydroxylation, oxidative skeletal rearrangement, and ring opening clearly supported enhanced oxidation of phenols by •OH. Overall, due to greater active sites, high surface activity, low band gap, and semiconducting nature, DMCC revealed promising potential for solar photocatalytic remediation of wastewater.