Oxidation Of MB Research Articles

G-C3N4/CuO loaded polyester fabric as effective Fenton-like dip-catalyst for the oxidation of dyes

This work aims to assess the catalytic efficiency for the degradation of organic dyes through advanced oxidation using a novel catalyst PE/g-C3N4-CuO. Polyester (PE) serves as an inert support, while the active catalyst comprises nanoparticles of graphitic carbon nitride g-C3N4-and copper oxide (CuO). The PE/g-C3N4-CuO was successfully prepared by sonicating g-C3N4 onto the PE matrix followed by the deposition of CuO nanoparticles, an efficient and reusable “dip catalyst”. Various physicochemical techniques have been employed to characterize the synthesized g-C3N4, CuO, and PE/g-C3N4-CuO such as FTIR, XRD, SEM, TEM, XPS and TGA. The composite is used for the oxidation of MB, MO, CR and RhB dyes via advanced oxidation process in presence of H2O2 as oxidant. In addition, the impacts of several parameters, such as pH, catalyst surface, CuO loading (%), H2O2 and MB concentration, on the degradation kinetics were thoroughly examined. A removal efficiency (94 %) of MB and TOC (80 %) has been attained for 30 min of the reaction using a surface of 4 cm2 PE/5%g-C3N4-10%CuO. The synthetized composite presented high stability after five reaction cycles with no discernible decrease in catalytic activity. Furthermore, OH were determined as the main reactive oxidative species (ROSs) responsible for highly efficient MB degradation. Finally, catalyst stability and recyclability demonstrated that the PE/g-C3N4-CuO might serve as a substitute Fenton-like catalyst for the oxidation of dyes and environmental cleanup.

Oxidized myoglobin: Revealing new perspectives and insights on factors affecting the water retention of myofibrillar proteins

The impact of oxidized myoglobin (Mb) on myofibrillar protein (MP) oxidation and water retention was investigated. Results showed that the oxidation of Mb increased with increasing concentration of oxidized linoleic acid (OLA). In the presence of 100 mmol/L OLA, hemin iron decreased by 62.07 % compared to the control group. Further investigation showed that mild oxidation of Mb (≤10 mmol/L OLA) increased the water retention and the absolute value of the zeta potential of MP, whereas excessive oxidation (>10 mmol/L OLA) decreased these properties. With the increase of Mb oxidation, the carbonyl content in MP increased, and α-helices changed to random helix. And the tertiary structure changed. Pearson correlation analysis suggested that oxidized Mb affected the water retention of MP, which was closely related to hemin iron and non-hemin iron. In conclusion, OLA induced Mb oxidation, further promoted MP oxidation and affected its water retention.

PH-Dependent photocatalytic performance of faceted BiOBr semiconductor particles in degradation of dyes

Bismuth oxyhalides, such as bismuth-oxy-bromide (BiOBr), show high performance in photocatalytic oxidation of water pollutants. Process conditions, and in particular the pH of the solution, largely affect the photocatalytic efficacy, which is fundamentally poorly understood. We prepared {001} faceted bismuth-oxy-bromide (BiOBr), and determined by advanced AFM analysis that the surface charge of the {001} facet of BiOBr is slightly positive at acidic pH (pH 3) and significantly negative and increasing in negative surface charge in the order pH 6 < pH 9. Decomposition of MB or RhB by illumination of BiOBr is strongly favored by basic conditions (pH 9-10), as evident from discoloration experiments, and determination of the TOC as a function of time of illumination. Reference experiments show the pH dependent degradation profiles cannot be explained by differences in quantities of adsorption of the dye, but rather by the lifetime and/or quantity of BiOBr related photoexcited (surface) charge carriers (holes and electrons) – correlating with surface charge. Using MeOH and other scavengers, we show oxidation of MB or RhB is mainly induced by superoxide anions (•O2− radicals) at low pH and by holes or hydroxyl radicals at high pH – in agreement with surface charge induced band bending. This study provides novel understanding of the pH dependence of the rates of photocatalytic degradation of dyes using BiOBr photocatalysts.

Effects of Maillard reaction products on myoglobin-mediated lipid oxidation during refrigerated storage of carp

Lipid oxidation is the major cause of quality deterioration in freshwater fish, especially mediated by myoglobin (Mb). This study aimed to investigate the antioxidant mechanism of Maillard reaction products (MRPs) in Mb-mediated lipid oxidation in common carp (Cyprinus carpio). MRPs exhibited promising antioxidant and antimicrobial capacities based on the reduced content of peroxide and thiobarbituric acid-reactive substances and inhibited microbial growth. MRPs inhibited the oxidation of Mb by lowering the transfer from oxymyoglobin to metmyoglobin and improving the stability of heme iron. The correlation analysis showed that MRPs regulated the formation of free radicals by maintaining the reduced structure of Mb and the integrity of heme iron, and also directly inhibited the formation of oxidation products in a chain radical reaction. The texture and electronic nose analysis indicated that MRPs could delay the structural disruption and flavor deterioration of surimi. Therefore, MRPs could effectively inhibit Mb-induced lipid oxidation and further control the resulting changes in the flavor and texture of surimi.

Amine-stabilized boronate groups at the surface of modified TiO2 under circumneutral pH conditions: Application to selective photocatalytic degradations

TiO2 has been functionalized by using 3-aminopropyltrimethoxy silane (APTMS) and 4-carboxyphenylboronic acid (CPBA). Solid state NMR indicated that ca. 50% of the amino groups did not react with CPBA, and stabilized vicinal boronate groups even at circumneutral pH, i.e. outside the stability range of isolated boronate ions (pH > 8.8). The as demonstrated existence of stabilized boronate groups at circumneutral pH has been used to carry out the proof of concept for selective photocatalytic degradations. In particular, irradiating bare TiO2 induced the expected oxidation of two model pollutants (alizarin red, AR and methylene blue, MB) dissolved in the reacting medium. Instead, the presence of boronate groups at the surface of TiO2 prevented the photocatalytic degradation of adsorbed AR, while simultaneously allowing oxidation of MB. Results are of environmental interest, and pave the way to processes enabling recovery of valuable compounds and simultaneous photocatalytic degradation of other noxious and/or useless species present in the same stream.

MoS2 nanosheets embedded in α-FeOOH as an efficient cathode for enhanced MFC-electro-Fenton performance in wastewater treatment

Microbial fuel cell-electro-Fenton system (MEF) has attracted attention due to refractory organic pollutants removal, where H2O2 is in-situ produced without external energy supply. Enhancement of H2O2 production and the activation of H2O2 to ·OH are the keys to improve degradation performance. Development of bifunctional catalytic cathode is a viable strategy. Herein, the α-FeOOH/MoS2 nanocomposites was fabricated by a novel facile hydrothermal method based on molybdenite-exfoliated MoS2 nanosheets suspension, which was used as modified cathode in a MEF system. The obtained α-FeOOH/1 wt%MoS2 cathode exhibited highest power density of 292.38 mW/m2, which was about 3.7 and 1.7 times higher than that of graphite plate and α-FeOOH, respectively. Doping of MoS2 nanosheets significantly enhanced electrocatalytic activity of the cathode and promoted in-situ H2O2 generation. Meanwhile, the exposed reductive Mo4+ on the surface of MoS2 could greatly facilitate the conversion cycle of Fe(III)/Fe(II), leading to the efficient activation of H2O2 into ·OH. The MEF with α-FeOOH/1 wt%MoS2 cathode exhibited excellent degradation and mineralization performance for MB, rhodamine B and tetracycline hydrochloride at optimized reaction condition. Furthermore, the MEF can simultaneously achieve MB oxidation and Cr(VI) reduction, and the corresponding removal ratio can reach up to 91.45% and 100%, respectively. Based on simple preparation method as well as recyclability and excellent catalytic property, the α-FeOOH/MoS2 composite catalyst is considered as a promising MEF cathode for efficient wastewater treatment.

Synthesis of Bimetallic FeCu-MOF and Its Performance as Catalyst of Peroxymonosulfate for Degradation of Methylene Blue.

Bimetallic MOFs have recently emerged as promising materials for wastewater treatment based on advanced oxidation processes. Herein, a new bimetallic MOF (FeCu-MOF) was fabricated by hydrothermal process. The structural, morphological, compositional and physicochemical properties of the as-synthesized bimetallic FeCu-MOF were characterized by XRD, FT-IR, SEM, TEM, BET, and XPS. TEM and XPS confirmed the homogeneous distribution of CuO2 nanoparticles in the as-synthesized materials. The result of wastewater treatment indicated that 100% of MB was removed by 6.0 mM PMS activated with 0.6 g/L of FeCu-MOF in 30 min. The high catalytic performance of FeCu-MOF was probably due to the accelerated electron and mass transfer resulting from the existence of a homogeneous distribution of unsaturated metal sites and an abundant mesoporous structure. The obtained results from the competitive quenching tests demonstrated that sulfate radicals (SO4•−) were the major species responsible for MB oxidation. In addition, hydroxyl (·OH) and singlet oxygen (1O2) also had a nonnegligible role in the MB removal. Interestingly, the addition of acetate ion (CHCOO−) promoted the removal of MB while other anions (including NO2−, H2PO4−, SO42−, HPO42−, and HCO3−) inhibited the MB removal. Furthermore, a possible mechanism based on both heterogeneous and homogeneous activation of PMS was proposed, along with the MB degradation mechanism.

Effect of hydrogen bond interaction in precursor on photocatalytic oxidation of MB by C-GA/g-C3N4 composites

It is well known that the design of precursor structure is an effective method to optimize the photocatalytic activity of g-C3N4, and it will be interesting to investigate the relationship between the precursor structure and the structure of the target catalyst. In this paper, by adjusting the addition amount of glutaraldehyde (GA), three kinds of glutaraldehyde/dicyandiamide (GA/DCDA) precursors with equilibrium/imbalance hydrogen bond interaction can be obtained, and the carbonized glutaraldehyde (C-GA)/g-C3N4 composite catalysts with different carbon content can be obtained after calcination. The obtained C-GA/g-C3N4 composite catalysts have different photocatalytic activity for methylene blue degradation. Compared with the original g-C3N4, the photocatalytic activity of C-GA/g-C3N4-2 composite is increased by 2.69 times. Through the analysis of thermal decomposition kinetics and structural characterization, we can see that the equilibrium interaction in the structure of GA/DCDA-2 precursor can promote the conversion of dicyandiamide to melamine, and glutaraldehyde carbonization will form more C-GA, and form a composite catalyst with closer interaction with g-C3N4. C-GA with close interaction and higher content can effectively promote the separation of photogenerated carriers and visible light absorption, thus improving its photocatalytic activity.

Lipid oxidation product nonenal and myoglobin oxidation

SummaryProvocative studies have proposed that the common 9 carbon lipid oxidation product, 4‐hydroxy‐2‐nonenal (HNE), increases myoglobin (Mb) autoxidation. Oxidised Mb (Fe3+ Mb or metMb) formation leads to an unappealing meat discoloration. Since Mb also facilitates lipid oxidation, an HNE induced increase in Mb autoxidation would constitute a positive feedback loop. However, NMR studies have noted that only fatty acids with carbon chain length exceeding 10 can significantly bind to Mb. They predict that HNE should not interact with Mb. The present study has used optical and NMR spectroscopy methods to determine if HNE interacts with Mb and if that interaction leads to an increased oxidation of Mb. The study finds no convincing evidence that HNE interacts with Mb and accelerates Mb autoxidation or oxidation by electron transfer. However, the presence of ethanol in the solution will increase Mb oxidation.

Expression and characterization of rainbow trout Oncorhynchus mykiss recombinant myoglobin

Recombinant expression system was established for rainbow trout myoglobin (Mb) considering its unique primary structure of having one unusual deletion and two cysteine residues in contrast to the other fish Mbs. The obtained recombinant Mb without His-tag showed non-cooperative thermal denaturation profile. The presence of free cysteine residue(s) in rainbow trout Mb was demonstrated by reacting with a sulfhydryl agent, 4, 4´-dithiodipyridine, which ultimately resulted in the oxidation of Mb with characteristic changes in visible absorption spectra. Besides, the recombinant Mb displayed steady peroxidase reactivity indicating in vivo roles of Mb as a reactive oxygen species scavenger. The findings of the present study indicate that the solitary rainbow trout Mb, which ultimately manifest typical secondary structure pattern and corroborate characteristic functionality, can be over expressed in recombinant system devoid of fusion tag.

Photocatalytic Generated Oxygen Species Properties by Fullerene Modified Two-Dimensional MoS2 and Degradation of Ammonia Under Visible Light

In this study, photocatalytic degradation of ammonia in petrochemical wastewater is investigated by solar light photocatalysis. Two-dimensional ultra-thin atomic layer structured MoS2 are synthesized via a simple hydrothermal method. We examine all prepared samples by means of physical techniques, such as SEM-EDX, HRTEM, FT-IR, BET, XRD, XPS, DRS and PL. And, we use fullerene modified MoS2 nanosheets to enhance the activity of photochemically generated oxygen (PGO) species. Surface area and pore volumes of the MoS2-fullerene samples significantly increase due to the existence of MoS2. And, PGO oxidation of MB, TBA and TMST, causing its concentration in aqueous solution to decrease, is confirmed by the results of PL. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the PGO effect increase in the case with modified fullerene. The experimental results show that this heterogeneous catalyst has a degradation of 88.43% achieved through visible light irradiation. The product for the degradation of NH3 is identified as N2, but not NO2−or NO3−.

Thermal Instability Induced by 4-Hydroxy-2-Nonenal in Beef Myoglobin

The secondary products of lipid oxidation, such as 4-hydroxy-2-nonenal (HNE), compromise myoglobin (Mb) redox stability and can thus impact thermal stability. Previous studies examined HNE-induced redox instability in beef Mb, whereas investigations are yet to be undertaken to evaluate the relationship between lipid oxidation and thermal stability of beef Mb. Therefore, the objective of the present study was to investigate the direct influence of HNE on thermal stability of beef Mb at meat conditions. Beef oxymyoglobin (0.15 mM) was incubated with HNE (1.0 mM) at pH 5.6 and 4°C for 21 d in the dark. Metmyoglobin formation, percentage Mb denaturation (PMD), and HNE adduction sites in Mb were examined on days 0, 7, 14, and 21. The experiment was replicated 3 times (n = 3). The data were evaluated using the MIXED procedure of SAS, and the differences among means were detected at the 5% level using the least significant difference test. The HNE-treated samples exhibited greater (P &amp;lt; 0.05) metmyoglobin formation and PMD than the controls. Additionally, the PMD difference between HNE-treated and control samples increased (P &amp;lt; 0.05) over time. Mass spectrometric analyses indicated that the number of HNE adduction sites increased with storage, and 6 histidines (positions 24, 36, 64, 93, 113, and 152) were adducted on day 21. HNE adduction at the distal histidine (position 64), which is critical to he me stability, was observed only on days 14 and 21. An increase in PMD on days 14 and 21 in HNE-treated samples could be partially due to the adduction at distal histidine. These findings indicated that HNE compromises thermal stability of beef Mb, possibly through altering the conformation of the heme protein by nucleophilic adduction.

Visible light responsive photoactive polymer supported on carbonaceous biomass for photocatalytic water remediation

Polymers have emerged as a new group of photoactive materials owing to their excellent optical and electronic properties. In this work, we report the synthesis and application of novel conjugated polymer for photocatalytic water remediation. The photoactive polymer was fabricated via the heat polymerization of Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) into the Polyvinylpyrrolidone (PVP) host polymer (with mass ratio of 98%). TCTA is an electron rich with high lying LUMO and band gap of Eg = 3.4 eV, however, its polymerization with PVP results in higher visible light response until 900 nm. Two conjugated polymer samples were prepared with low and high TCTA contains, namely CP1 and CP2, respectively. The as-prepared photoactive samples were used as photoredox catalysts for the photocatalytic reduction of Cr(VI) and oxidation of MB under visible light (420 nm). CP2 showed higher visible light response, better electrochemical activity and excellent photocatalytic activity compared to CP1. In terms of Cr(VI) photoreduction, CP2 (0.25 g/L) can totally reduce Cr(VI) (20 ppm) at pH ranging from 3 to 8 under visible light. A total reduction of 40 ppm of Cr(VI) was found within 60 min using 0.75 g/L of CP2. 98% of MB was oxidized within 90 min using 0.25 g/L of CP2 under visible light. The photoactive polymer was supported into lignocellulosic biomass for higher surface area and better stability. As a result, this latter composite showed an enhanced adsorption capacity and photocatalytic efficiency towards Cr(VI) and MB compared to bare photoactive polymer. The main compounds used to fabricate this composite including PVP and natural biomass are eco-friendly, safe and low-cost which make it economically feasible photocatalyst for water remediation or other photoredox systems.

CuO NPs incorporated into electron-rich TCTA@PVP photoactive polymer for the photocatalytic oxidation of dyes and bacteria inactivation

Herein we report the synthesis of electron-rich TCTA@PVP conjugated polymer (CP) modified with CuO NPs as a photocatalyst for water remediation and disinfection under visible light (λ > 420 nm). CP@CuO showed an extended visible light response up to 900 nm. The photoactivities of bare CP, CP@Cu and CP@CuO with and without peroxymonosulfate (PMS) addition were tested towards the oxidation of MB under visible light. It was found that the incorporation of Cu(II) or CuO into CP platform enhances the photocatalytic activity and PMS activation due to the synergistic effects in terms of better visible light response and high yield photogenerated reactive oxygen species. In addition, rich-electron CP can help the redox recycling of Cu(I) and Cu(II) species via electron transfer from CP to CuO under visible light, which in turn facilitates the activation of PMS (HSO5−) to HSO4 radicals. The photocatalytic antibacterial activity of CP@CuO by considering E.Coli inactivation in water under UV–vis light was investigated.

Hourglass-type polyoxometalate-based crystalline materials as efficient cooperating photocatalysts for the reduction of Cr(vi) and oxidation of dyes

Hourglass-type polyoxometalate-based crystalline materials exhibit efficient photocatalytic activities towards simultaneous photocatalytic Cr(vi) reduction and organic MB oxidation.

Effects of the E.Coli exotoxin alpha-hemolysin on human chorioamniotic membranes.

Herein we report the synthesis of electron-rich [email protected] conjugated polymer (CP) modified with CuO NPs as a photocatalyst for water remediation and disinfection under visible light (λ > 420 nm). [email protected] showed an extended visible light response up to 900 nm. The photoactivities of bare CP, [email protected] and [email protected] with and without peroxymonosulfate (PMS) addition were tested towards the oxidation of MB under visible light. It was found that the incorporation of Cu(II) or CuO into CP platform enhances the photocatalytic activity and PMS activation due to the synergistic effects in terms of better visible light response and high yield photogenerated reactive oxygen species. In addition, rich-electron CP can help the redox recycling of Cu(I) and Cu(II) species via electron transfer from CP to CuO under visible light, which in turn facilitates the activation of PMS (HSO5−) to HSO4 radicals. The photocatalytic antibacterial activity of [email protected] by considering E.Coli inactivation in water under UV–vis light was investigated.

Dual-signal amplification strategy for miRNA sensing with high sensitivity and selectivity by use of single Au nanowire electrodes

MicroRNAs (miRNAs) have been applied as biomarkers and better detection of their expression profiles plays important roles in early diagnosis of cancers. In this work, a simple dual-signal amplification strategy has been used to construct a novel nanosensor on single Au nanowire electrodes (SAuNWEs) for miRNA-16 detection based on the “signal-on” and “signal-off” features during hybridization/de-hybridization process. The ferrocene-labeled aptamer capture probe (Fc-CP-16) is designed to hybridize with thiolated methylene blue-labeled DNA probe (MB-CP) on SAuNWE to form duplex DNA, and the addition of miRNA-16 can lead to the dissociation of duplex structure due to the highly matched sequences between miRNA-16 and Fc-CP-16. The remaining MB-CP can thus tend to recover its hairpin structure at the presence of Mg2+ through the hybridization of its complementary sequences. During this hybridization/de-hybridization process, the changes of Fc and MB oxidation peaks can be recorded, and there has a linear relationship between the sum of dual-signal changes (ΔI=ΔIMB+|ΔIFc|) and the logarithm of miRNA-16 concentrations, which can be used to detect miRNA-16. Including miRNA extraction, the dual-signal amplification strategy for miRNA sensing assay was carried out about 2 h for the detection in real samples. This novel nanosensor has small dimension, good selectivity, rapid response and regeneration ability, which can satisfy the need for early cancer marker detection in cells/organelles.

Photoactivation of a biodegradable polymer (PHB): Generation of radicals for pollutants oxidation

The PHB (poly (3-hydroxybutyrate)) film and nanocomposite act as catalysts in the oxidation of organic compounds, such as methylene blue dye (MB) using UV radiation. The results indicate that the materials produce in situ hydroxyl radicals, which are responsible for the deep oxidation of MB. The results showed for the first time that only the PHB polymer presents good catalytic activity (∼80%), indicating the possibility of avoiding the use of semiconducting metals in the processes. The main effect is the cleavage of the polymer chains which modifies the PHB structure. This effect also promotes the mineralization of the PHB polymer during the process. Thus, the polymer degrades organic molecules present in water and is also transformed without generating pollutant molecules, as shown by the ESI-MS analyzes. This new catalyst concept allows its use for up to 7 cycles efficiently without semiconductor metals.

Sun-light driven rapid photocatalytic degradation of methylene blue by poly(methyl methacrylate)/metal oxide nanocomposites

Discharge of dyes (major industrial coloring agents ∼700,000 tonnes) in environment is of concern due to their high perseverance, toxicity and carcinogenicity. Thus, effective elimination of organic dye (methylene blue) was carried out by poly(methyl methacrylate) (PMMA) incorporated metal oxide nanocomposites. Spherical and semi crystalline Fe3O4-PMMA, ZnO-PMMA, CuO-PMMA and Ni2O3-PMMA were self-assembled via green route employing Sapindus mukkorossi (Plant extract). At optimised conditions (dye conc: 2 mg L−1; catalyst: 80 mg: neutral pH) MO-PMMA showed maximum degradation efficiency (90–99%; t1/2 = 5.1–5.6 h) than that of individual MO (74–80%; t1/2 = 5.8–6.8 h) credited to improved thermal stability and surface area via incorporation of MO into PMMA matrix. Like MO, highest degradation with ZnO-PMMA (99%; Xm = 0.135 mg/g) followed by Ni2O3-PMMA (98%), CuO-PMMA (93%) and Fe3O4-PMMA (90%) could be attributed to its high surface area (85.32 m2 g−1) and least zeta potential (-22.5 eV). Adsorption of MB over catalyst was statistically significant with Langmuir isotherms (R2: 0.99 and p value: 0.0005) and first order kinetics with greatly reduced half-life. Comparatively higher degradation in sunlight than dark, and involving hydroxylation, oxidation and ring opening clearly reinforced boosted oxidation of MB by OH. Moreover, reduction in degradation (50-40%) in presence of OH scavengers supported the photocatalytic activity of nanocomposites. MB was degraded into minor non-toxic by-products such as (Z)-hexa-3,5-dien-1-ol and (Z)-buta-1,3-dien-1-ol and benzoquinone. Overall, by virtue of greater active sites, high surface activity and semiconducting nature, the as-synthesized MO-PMMA photocatalyst is a promising, recyclable (n = 10) and eco-friendly panorama in the treatment of organic- pollutants in water and wastewater-treatment.

Revisiting the problem of using methylene blue as a model pollutant in photocatalysis: The case of InVO4/BiVO4 composites

Evaluation of photocatalytic activity towards oxidative degradation of organic pollutants is of crucial importance in heterogeneous photocatalysis. In this study, we address the problem of using a visible-light absorbing dye, methylene blue, as a model pollutant in photocatalytic investigations based on experiments using visible light-responsive InVO4/BiVO4 composite photocatalyts. We found that InVO4/BiVO4 composites exhibit photoactivity in oxidative decomposition of MB under visible light, but no degradation was found in case of other dyes (e.g., rhodamine B or methyl orange) or transparent organic pollutants (e.g., 4-chlorophenol and diethyl phthalate). Detailed mechanistic studies demonstrate that the mechanism of photocatalytic degradation of MB depends on excitation light energy. If the InVO4/BiVO4 composite is excited exclusively (400 nm < λ < 500 nm), direct photocatalytic oxidation of MB occurs. Surprisingly, wavelength-resolved photocurrent measurements indicated that the degradation of MB under long-wavelength irradiation (λ > 560 nm), where MB can be excited but the InVO4/BiVO4 photocatalyst itself cannot, is not caused by the indirect mechanism involving sensitization and injection from the MB excited state to the conduction band of the photocatalyst. Instead, in this range the oxidation of MB is initiated by singlet oxygen formed via energy transfer from the excited MB to triplet oxygen, a degradation mechanism hitherto neglected in the literature. More generally, our study highlights the very peculiar photochemistry of MB in heterogeneous photocatalysis, and leads to the conclusion that MB is completely unsuitable for photocatalytic testing under visible light, and its use as a model pollutant should be definitely discouraged.