Methylene Blue Activity Research Articles

Effect of Hyaluronic Acid on the Activity of Methylene Blue in Photogeneration of 1O2

The effect of a natural polysaccharide (hyaluronic acid (HA)) on the photocatalytic activity of methylene blue (MB) was studied both under model conditions (a tryptophan photooxidation reaction in water) and with in vitro experiments on P. aeruginosa and S. aureus bacterial cultures. It was shown spectrophotometrically that, in the presence of HA, an increase in the optical density of the absorption bands λ = 665 nm and 620 nm—which correspond to the monomeric and dimeric forms of the dye, respectively—was observed in the EAS of the dye, while the ratio of the optical density of these bands remained practically unchanged. When adding HA to MB, the intensity of singlet oxygen 1O2 photoluminescence and the degree of fluorescence polarization of MB increase. The observed effects are associated with the disaggregation of molecular associates of the dye in the presence of HA. The maximum increase in the photocatalytic activity of MB (by 1.6 times) was observed in the presence of HA, with concentrations in a range between 0.0015 wt.% and 0.005 wt.%.

Photodynamic therapy with methylene blue and chlorin e6 photosensitizers: study on Ehrlich carcinoma mice model

Hypoxia negatively affcts the effctiveness of all types of anticancer therapy, in particular photodynamic therapy (PDT). In this regard, various approaches to overcome the limitations associated with hypoxia are widely discussed in the literature, one of them is the use of photosensitizers (PS) operating through the fist mechanism of the photodynamic reaction, such as methylene blue (MB). Previously, we have demonstrated that MB can have a positive effect on tumor oxygenation. In this work, we investigated the photodynamic activity of MB and a combination of MB with chlorin e6 on a tumor in vivo using a model of Ehrlich carcinoma. PDT was studied with the joint and separate administration of chlorin e6 and MB. The accumulation and localization of MB and its combination with chlorin e6 in vivo was assessed using video ˛uorescence and spectroscopic methods, and the effect of laser exposure on accumulation was analyzed. After the PDT with chlorin e6, MB and a combination of MB with chlorin e6, a good therapeutic effect and a decrease in the tumor growth rate were observed compared to the control, especially in groups with PDT with MB and with the simultaneous administration of chlorin e6 and MB. The level of tumor oxygenation on days 3 and 5 after PDT was higher for groups with irradiation, the highest oxygenation on the 5th day after PDT was observed in the group with PDT only with MB. Phasor diagrams of tumors after PDT show a deviation from the metabolic trajectory and a shift towards a longer lifetimes compared to the control tumor, which indicates the presence of lipid peroxidation products. Thus, tumor regression after PDT is associated with the direct destruction of tumor cells under the in˛uence of reactive oxygen species formed during PDT. Thus, the effectiveness of PDT with the combined use of MB and chlorin e6 has been demonstrated, and the main mechanisms of the antitumor effect of the combination of these PS have been studied.

Novel green CQDs/ZnO binary photocatalyst synthesis for efficient visible light irradiation of organic dye degradation for environmental remediation

The advancement of effective and sustainable water treatment depends on the creation of a highly active and controllable photocatalyst. A suitable site for increasing the activity of such a photocatalyst is the heterojunction. Organic dyes have become a major source of concern in recent years because they are so common in wastewater. Heavy metals have a high permanence in wastewater and may be carcinogenic. Low-waste, high-performance technologies are needed to remove organic dyes and heavy metals from wastewater. To determine their structural, photochemical, and optical properties, Carbon Quantum Dots (CQDs) (made from Tamarindus indica shell waste), ZnO (from Ficus Benghalensis), and CQDs/ZnO photocatalysts were synthesised using green route techniques, followed by calcination. Malachite Green (MG) and Methylene Blue (MB) are effectively photo-degraded by the synthesised CQDs, ZnO, and Green CQDs/ZnO Binary Photocatalyst under the irradiation of naturally occurring solar light. The maximum photocatalytic activity for MG and MB within 60 min was shown by the Green CQDs/ZnO Binary Photocatalyst, with 100 % and 100 %, respectively. The reduced rate of electron-hole recombination causes effective photocatalytic activity. According to experiments with free radical entrapment, O2 and h+ play an important role in photodegradation. The study thus presents a fresh approach to the synthesis of highly effective binary photocatalysts for their application in environmental remediation.

Synthesis and Characterization of WO3/BiVO4/Graphene Ternary Nanocomposites for the Photodegradation of Methlyene Blue and Tetracycline

In this study, a hydrothermal method was employed to synthesize the ternary nanocomposites comprising WO3/BiVO4/Graphene, all driven by visible light. The characteristics of these nanocomposites were interpreted through techniques such as UV–Vis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoluminescence spectroscopy (PL). The enhanced performance of the composite, attributed to its heightened capability for separating charge carriers, outperformed that of the individual semiconductor components. The PL results validated the composite's improved charge separation. The nanocomposites have weaker PL peaks, indicating slower e−/h+ recombination. The balanced concentrations of the mixed semiconductors in the composite affected both PL intensity and photodegradation efficiency. The photocatalytic degradation of methylene blue (MB) and tetracycline (TC) was observed by nanocomposites. The heterogeneous nanocomposite WOBV/G-5 with 0.03 mg graphene content has a better photocatalytic activity for both MB (63 %) and TC (80 %) than other concentrations. It has also been investigated using TOC and COD analysis. Moreover, zeta potential analysis and pH analysis have been done to check the conductivity of optimized photocatalyst. Additionally, to check the stability of WOBV/G-5 photocatalyst, recyclability test that shows 58 % degradation rate after five cycles and analysis of XRD after recyclability have also been performed. Role of active species (h+, O2−, and OH.) was observed by using different scavengers (EDTA, BQ, and IPA) in trapping experiment that plays a vital role in photocatalytic degradation process.

Effect of Saponin on Methylene Blue (MB) Photo-Antimicrobial Activity Against Planktonic and Biofilm Form of Bacteria.

Bacterial resistance has led to the spread of bacterial infections such as chronic wound infections. Finding solutions for combating resistant bacteria in chronic wounds such as Staphylococcus aureus and Pseudomonas aeruginosa became an attractive theme among researchers. P. aeruginosa is a gram negative opportunistic human pathogenic bacterium that is difficult to treat due to its high resistance to antibiotics. S. aureus (gram negative bacterium) also has a high antibiotic resistance, so that it is resistant to vancomycin (VRSA), tetracycline, fluoroquinolones and beta-lactam antibiotics including penicillin and methicillin (MRSA). In particular, S. aureus and P. aeruginosa have intrinsic and acquired antibiotic resistance, making the clinical management of infection a real challenge, especially in patients with comorbidities. aPDT can be proposed as a new method in the treatment of multi-drug resistant bacteria in chronic wound infection conditions. In this study, the effect of saponin (100 μg/mL) on photodynamic inactivation on planktonic and biofilm forms of P. aeruginosa (ATCC 27853) and S. aureus (ATCC 25923) strains and on Human Dermal Fibroblast (HDF) cells was investigated. Methylene blue (MB) was used as photosensitizer (0, 10, 50, 100 μg/mL). The light source was a red LED source (660 nm; power density: 20 mW/cm2) which is related to the maximum absorption of MB. The results showed that the use of saponin in combination with MB-aPDT (Methylene Blue-antibacterial photodynamic therapy) reduces the phototoxic activity of MB due to decreasing the monomer form of MB. This result was obtained by spectrophotometric study. Also, the result of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay showed that 8 min of irradiation (660 nm)at 10 μg/mL concentration of alone MB had the lowest phototoxic effect on HDF cells. Due to reduced phototoxic properties of MB in this method, detergents containing saponins not recommended to applied at the same time with MB-aPDT in wound infection area.

Synthesis of 1D magnetic Fe3O4@SiO2/TiO2 nanostir bar photocatalyst for the degradation of MB under UV light

Here, a novel one-dimensional (1D) magnetic Fe3O4@SiO2/TiO2 nanostir bar both with high-efficient adsorption and photocatalysis of Methylene blue (MB) has been explored. Firstly, silicon and titanium precursor were loaded on the surface of Fe3O4 through the static magnetic induced self-assembly. Then the TiO2/SiO2 hybrid shell were formed by the hydrothermal treatment process to achieve the 1D magnetic nanostir bar. The 1D magnetic Fe3O4@SiO2/TiO2 photocatalyst exhibited good adsorption capacity and degradation activity of MB. The adsorption capacity of MB by Fe3O4@SiO2/TiO2(60 %) was 40 mg g−1. The apparent reaction rate constant of Fe3O4@SiO2/TiO2 (60 %) was 0.129 min−1. This work will provide a general strategy to explore other useful 1D magnetic nanomaterials for micro-reaction system.

Silver doped barium titanate nanoparticles for enhanced visible light photocatalytic degradation of dyes

Due to the rapid growth of global population, new, fast and reliable methods must be developed to purify contaminated water. Various photocatalysts have been developed to remove organic dyes from water. Herein, Ag doped BaTiO3 has been synthesized using a facile solvothermal method and its excellent photocatalytic activities were demonstrated in degradation of both anionic and cationic dyes under visible light illumination. Ag doped BaTiO3 nanoparticles showed greater efficacy in the degradation of methylene blue (MB) and eosin yellow (EY) than undoped BaTiO3 nanoparticles, which makes them a better candidate for photocatalysis. 1.0 AgBT sample showed the highest photocatalytic activity for MB (99.1 % in 100 min) and EY (99.3 % in 60 min) dye degradation compared with those of other samples. Further, the trapping experiments revealed that hydroxyl radicals and holes are the active species in the photocatalytic process of MB and EY dye degradation and recycle test showed excellent stability of the synthesized material.

Thermo-responsive cascade antimicrobial platform for precise biofilm removal and enhanced wound healing.

Bacterial infection, tissue hypoxia and inflammatory response can hinder infected wound repair. This study aimed to develop a multifunctional specific therapeutic photo-activated release nanosystem [HMPB@MB@AuNPs@PMB@HA (HMAPH)] by loading photosensitizer methylene blue (MB) into hollow mesoporous Prussian blue nanostructures and modifying the surface with gold particles, polymyxin B (PMB) and hydrophilic hyaluronic acid. The HMAPH was characterized using transmission electron microscopy, UV-vis, Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photon spectroscopy. The photothermal performance, iron ion release and free radical generation of the HMAPH were measured under different conditions to investigate its thermo-responsive cascade reaction. The antibacterial ability of HMAPH was investigated using live/dead fluorescence tests. The morphology and membrane integrity of Pseudomonas aeruginosa (P. aeruginosa) were investigated using transmission electron microscopy. The anti-biofilm activity of HMAPH was evaluated using crystal violet and SYBR Green I staining. Finally, we established a mouse model of a skin wound infected by P. aeruginosa to confirm the in vivo effectiveness of HMAPH. We used immunofluorescent staining, hematoxylin-eosin staining, Masson staining and enzyme-linked immunosorbent assay to examine whether HMAPH promoted wound healing and reduced inflammatory damage. In this study, hyaluronic acid was decomposed under the action of hyaluronidase. Also, the exposed nanomaterials specifically bound to the outer membrane of P. aeruginosa through PMB to increase the membrane sensitivity to photodynamic treatment. Under dual-light irradiation, a large amount of iron ions released by HMAPH underwent a Fenton reaction with H2O2 in bacteria to generate hydroxyl radicals (•OH), enabling direct killing of cells by hyperthermia. Additionally, the photodynamic activity of MB released by photo-induced activation led to the generation of reactive oxygen species, achieving synergistic and effective inhibition of P. aeruginosa. HMAPH also inhibited biofilm formation and downregulated the expression of virulence factors. In vivo experiments revealed that HMAPH accelerated the healing of P. aeruginosa-infected wounds by promoting angiogenesis and skin regeneration, inhibiting the inflammatory response and promoting M1 to M2 polarization. Our study proposed a strategy against bacteria and biofilms through a synergistic photothermal-photodynamic-Fenton reaction, opening up new prospects for combating biofilm-associated infections.

Synthesis of a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin.

Porphyrin compound-based photochemical molecules and biomaterials have been synthesized for photosensitivity and bioimaging experiments. However, most porphyrin photosensitizers have limited application in biological environments owing to severe aggregation in aqueous solutions. In the present study, we prepared amphipathic and photosensitive copolymers using zinc porphyrin via consecutive atom transfer-free radical polymerizations (ATRPs) comprising photoresponsive and thermosensitive chain segments. Furthermore, we evaluated the photocatalytic activity of the copolymer for methylene blue (MB) in water. Methods: First, we synthesized a photoresponsive ain segment of poly (6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate) (ZnPor-PAzo); then, ZnPor-PAzo was used as a macroinitiator and was polymerized with N-isopropylacrylamide (NIPAM) via ATRPs to obtain a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin [(ZnPor-PAzo)-PNIPAMs]. Results: The polydispersity index (M w/M n) of (ZnPor-PAzo)-PNIPAMs was 1.19-1.32. Furthermore, its photoresponsive and thermosensitive characteristics were comprehensively studied. Discussion: The end-functionalized diblock copolymer (ZnPor-PAzo)-PNIPAM exhibits obvious fluorescence and efficient photocatalytic activity for aqueous MB under visible light.

Facile synthesis of silver chloride-polyaniline nanocomposites and its photocatalytic activity for the degradation of methylene blue

Herein, we report a green and an effective strategy for the synthesis of polyaniline-silver chloride (AgCl@PANI) nanocomposites by using facile in-situ chemical oxidative polymerization method in the presence of as-synthesized silver nanoparticles (Ag NPs) for the study of their photocatalytic activity towards the photodegradation of methylene blue (MB) under UV irradiation. The contents of Ag NPs varied from 2% to 6% during polymerization reaction to get AgCl@PANI nanocomposites. These synthesized polymer nanocomposites were characterized for their structural and optical properties, thermal stability, dc conductivity and photocatalytic activity by FT-IR spectroscopy, XRD, UV–Vis spectroscopy, TGA, SEM, standard four probe method and the photodegradation activity of MB, respectively. XRD analysis confirm the successful formation of AgCl@PANI nanocomposites without the presence of additional phases. TGA shows that AgCl@PANI nanocomposites have excellent thermal stability due to the barrier effect of AgCl moieties bounded with in the polymer chain and the strong physiochemical interactions between PANI and AgCl as inferred from FT-IR and UV–vis analysis. Under UV irradiation, the AgCl@PANI nanocomposite, with 4 wt% of Ag NPs (AgCl@PANI-4%), demonstrated excellent photocatalytic activity for MB degradation with the photodegradation percentage of ∼ 99 % in 20 min. The experimental findings illustrate that the superior photocatalytic activity of AgCl@PANI nanocomposites is owing to incorporation of AgCl moieties in the polymer structure, less needed energy for the formation of electron-hole pairs in the quinoid ring of PANI in the UV-region, enhanced light absorption owing to smaller grain size morphology, high surface area of the nanocomposite and high electrical conductivity (128 mS.cm−2). These results suggest the potential of these synthesized conjugated polymer-based nanocomposites as a photocatalyst for cost-effective and efficient wastewater treatment for the industrial applications.

Cu-coated graphitic carbon nitride (Cu/CN) with ideal photocatalytic and antibacterial properties

An improved photocatalytic activity of Graphitic carbon nitride (CN) photocatalyst was achieved by incorporating Cu2+ into CN in the presence of hyperbranched polyethylene amine (HPEI) as a capping agent. The addition of Cu to CN (CNHPEI+Cu) increased the photocatalytic degradation efficiency of wastewater dye pollutant methylene blue (MB) from 42 % to 95 %. E. coli and MS2 performed best in terms of inactivation to CNHPEI+Cu, achieving 5.5 ± 0.3 and 5.3 ± 0.1 log inactivation after 60 min of exposure, respectively. Excellent catalyst reusability and photocatalytic activity for MB in various types were obtained. To investigate the photocatalyst structure, morphology, optical, and photoelectric properties, we used X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and photocatalytic activity. It was found through XRD and XPS that the prepared photocatalysts were made up of Cu-doped CN and that the valence state of Cu was Cu0. Under the visible part of the solar spectrum (>400 nm), the N2 adsorption-desorption isotherms of pure CN, CNHPEI, and CNHPEI+Cu showed that copper did not alter the microstructure of pure CN. The photocatalytic activity of CNHPEI+Cu was improved by incorporating Cu0 into CN, as this reduces the rate of electron-hole recombination in pure CN and accelerates the separation of electron-hole pairs. Electron spin resonance (ESR) spin trap experiments on the production of reactive oxygen species (ROS) from CNHPEI+Cu under visible light indicate that the presence of superoxide radicals (O2•−), hydroxyl radicals (•OH) and holes could enhance the photocatalytic activity of the material.

Superior Photocatalytic and Antibacterial Activity of Cadmium Selenide Nanoparticles Doped by Titanium or Lanthanum

This contemporary work delineates the photocatalytic and antibacterial activity of titanium (Ti) and lanthanum (La)‐doped cadmium selenide (CdSe) nanoparticles produced by a simple wet chemical method. Studies using diffraction and microscopy reveal that the synthesized samples devised cubic crystalline structure. The incorporation of the dopant into the host material is analyzed using X‐ray diffraction, scanning electron microscope–EDAX, and transmission electron microscopic studies. The photocatalytic activity Ti‐ and La‐doped CdSe nanoparticles results in improved degradation toward methylene blue (MB) dye under direct solar irradiation. This unique behavior is ascribed to the enhanced light absorption tendency with larger charge separation efficiency. Ongoing operational factors like initial dye concentration, catalyst dose, pH, and duration are evaluated regarding their effects on MB dye degradation. The photocatalytic activity for MB follows pseudo‐first‐order kinetics. The antibacterial activity of Ti– and La–metal‐doped CdSe is tested against Pseudomonas arueginosa and Staph aureus bacteria. The Ti–CdSe and La–CdSe nanoparticles show good antibacterial activity after 24 h of bacterial growth Pseudomonas arueginosa and Staph aureus, respectively. Based on the findings, Ti–CdSe and La–CdSe nanoparticles exhibit an enhanced photocatalytic and antibacterial activity when compared with CdSe nanoparticles.

Mucoadhesive liquid crystal precursor system for photodynamic therapy of oral cancer mediated by methylene blue

Oral cancer is one of the most prevalent types of cancer head and neck cancers worldwide. Photodynamic therapy (PDT) has demonstrated great potential against cancers, reducing long-term morbidity. In this study, we investigated the incorporation of methylene blue (MB) in a mucoadhesive liquid crystal precursor system (LCPS) for oral cancer treatment. The photostability and the in vitro release, permeation, and retention profile of MB-loaded LCPS (MB-LCPS) were investigated, as well as its in vitro PDT activity against normal (HaCaT) and tumoral (HSC-3) cell lines. LCPS increased the photostability of MB and exhibited a prolonged release profile of MB. In addition, LCPS increased the retention of MB in the porcine esophageal mucosa by around 3 times higher than the MB solution. The retention of MB in LCPS was around 2 times greater than its permeability, which is suitable for guaranteeing the maintenance of the therapy in the oral cavity. In vitro cytotoxicity assay indicated that MB-LCPS increased the antitumoral activity of MB after 20 min of irradiation at 660 nm and 12.5 J/cm2. The results obtained suggest that the developed formulation is an interesting strategy for the potential application in the treatment of oral cancer by PDT.

Development of Blended Biopolymer-Based Photocatalytic Hydrogel Beads for Adsorption and Photodegradation of Dyes.

Blended biopolymer-based photocatalytic hydrogel beads were synthesized by dissolving the biopolymers in 1-ethyl-3-methylimidazolium acetate ([Emim][Ac]), adding TiO2, and reconstituting the beads with ethanol. The incorporation of modifying biopolymer significantly enhanced the adsorption capacity of the cellulose/TiO2 beads. Cellulose/carrageenan/TiO2 beads exhibited a 7.0-fold increase in adsorption capacity for methylene blue (MB). In contrast, cellulose/chitosan/TiO2 beads showed a 4.8-fold increase in adsorption capacity for methyl orange (MO) compared with cellulose/TiO2 beads. In addition, cellulose/TiO2 microbeads were prepared through the sol-gel transition of the [Emim][Ac]-in-oil emulsion to enhance photodegradation activity. These microbeads displayed a 4.6-fold higher adsorption capacity and 2.8-fold higher photodegradation activity for MB than the millimeter-sized beads. Furthermore, they exhibited superior dye removal efficiencies for various dyes such as Congo red, MO, MB, crystal violet, and rhodamine B, surpassing the performance of larger beads. To expand the industrial applicability of the microbeads, biopolymer/TiO2 magnetic microbeads were developed by incorporating Fe2O3. These magnetic microbeads outperformed millimeter-sized beads regarding the efficiency and time required for MB removal from aqueous solutions. Furthermore, the physicochemical properties of magnetic microbeads can be easily controlled by adjusting the type of biopolymer modifier, the TiO2 and magnetic particle content, and the ratio of each component based on the target molecule. Therefore, biopolymer-based photocatalytic magnetic microbeads have great potential not only in environmental fields but also in biomedical fields.

RED LASER PHOTODYNAMIC THERAPY OF MELANOMA B16 IN AN EXPERIMENTAL MODEL IN VIVO

Introduction: In recent decades, the incidence of melanoma among European population has been steadily increasing. In addition, the age of patients with this pathology is declining - today more than half of patients with melanoma are under 65 years. Melanoma is an aggressive metastatic tumor that is difficult to treat. The tumor is resistant to chemotherapy and radiotherapy. However, the mechanism of photodynamic action differs from the mechanism of cell damage by antitumor drugs or ionizing radiation. Therefore, there is a high probability that with the help of photodynamic therapy it will be possible to overcome the resistance of melanoma cells to damage. Materials and methods: The study was performed on melanoma tumors of B16 mice. The due methylene blue (MB) was used as a photosensitizer through the known affinity of this colorant to the melanin pigment of melanoma cells. The experiments used the radiation of two semiconductor lasers (Fotonika Plus, Cherkasy. Ukraine) with a wavelength of 660 nm, which corresponds to the maximum absorption of methylene blue. Results:The possibility of increasing the anti-melanoma photodynamic activity of MB with the help of a modifier - the natural polysaccharide chitosan was studied. B16 melanoma has been shown to be sensitive to PDT with MB and its sensitivity can be increased by using MB with the natural polysaccharide chitosan, which has immunoadjuvant properties. Conclusion: As a result of the presented research, a variant of PDT of B16 melanoma of mice was developed using MB sensitizer and chitosan immunoadjuvant, which includes intratumoral injection of MB together with chitosan, irradiation of tumors with a red laser with a wavelength of 660 nm, as well as the use of chitosan as an immunomodulatory factor.

Enhanced visible light photocatalytic degradation of methylene blue dye using efficient Mg/S co-doped TiO2 nanoparticles

Herein, the Mg-S co-doped TiO2 nanoparticles (NPs) were synthesized by the sol-gel method, and their photocatalytic activity of MB (methylene blue) dye was examined under simulated visible light. X-ray diffraction patterns of Mg-S co-doped TiO2 reveal an average crystallite size of 19.3 nm. Moreover, results showed that Mg/S co-doped TiO2 NPs had pure anatase structures with spherical morphology. The band gap energy Mg/S co-doped TiO2 was decreased from 3.12 to 2.78 eV by adding the doping and codoping of Mg and S into TiO2 NPs. The Mg/S co-doped TiO2 NPs showed excellent photocatalytic activity compared to pristine TiO2, Mg-TiO2, and S-TiO2 NPs. The maximum degradation efficiency of MB was achieved at 94.8% for Mg/S co-doped TiO2 NPs. Meanwhile, the possible photocatalytic mechanism of photocatalysts was discussed. Different weight percentages of Mg/S co-doped TiO2 were used to investigate the effect of the Ag concentration on antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the maximum antibacterial activity was achieved by 24 mm and 22 mm for TiO2 NPs membrane doped and co-doped with Mg/S. The current investigation delivers a promising strategy to promote photocatalytic activity to eliminate waterborne contaminants.

On the Photo-Eradication of Methicillin-Resistant Staphylococcus aureus Biofilm Using Methylene Blue.

This work compared the effectiveness of several Methylene Blue (MB)-based protocols for photo-eradication of biofilms formed on the surface of the glass and stainless steel discs by S. aureus MRSA isolates using a diode laser (λ = 665 nm; output power 40 mW; energy fluence was 189 J cm-2). The results obtained showed that MB alone, up to a concentration of 62.5 mgL-1, had limited photo-bactericidal activity. It was possible to enhance the activity of MB using two types of spherical gold nanoparticles of similar sizes, 15 ± 3 nm/20 ± 3 nm, but differing in the method of their synthesis and stabilization. The enhancement of the photodestruction effect was related to the increased production of hydroxyl radicals by the MB+gold nanoparticles mixture, and this mixture showed dark cytotoxicity against the cocci studied. Effective destruction (mortality above 99.9%) of the biofilms formed by MRSA isolates was also possible without the use of gold nanoparticles, but the concentration of MB had to be at least 125 mgL-1. A highly efficient protocol of photodestruction of biofilms, consisting of triple exposure of biofilms to laser light in the presence of MB alone, combined with the removal of dead bacteria protecting deep layers of pathogens against photosensitization, was also described.

Synergy of adsorption-photocatalysis and enriched surface oxygen vacancies over lignin-biochar/Bi2MoO6 nanocomposites for organic pollutant removal and bamboo ECF bleaching effluent treatment

LC/Bi 2 MoO 6 composites were successfully fabricated and applied to the effective degradation of methylene blue (MB) under visible light illumination. The composition, morphology and photoelectrochemical properties of prepared samples were characterized by various techniques. EPR analysis reveals that the density of surface oxygen vacancies was enhanced after lignin-biochar addition. Under optimal conditions, the degradation efficiency of MB over LC/Bi 2 MoO 6 was 95.34 % at 1 h under visible light irradiation, and the reaction rate constant ( k ) was 18.96 folds higher than that of pristine Bi 2 MoO 6 . The enhanced photocatalytic performance of LC/Bi 2 MoO 6 was due to the synergistic effect between adsorption-photocatalysis and enriched surface oxygen vacancies, which greatly promotes the separation of photogenerated charge carriers. Moreover, the MB degradation removal with LC/Bi 2 MoO 6 decreased by 3.84 % at 1 h under visible light irradiation after four cycles, illustrating excellent stability and reusability in the photocatalytic recycling process. Notably, the bandgap of Bi 2 MoO 6 decreased from 2.66 eV to 2.26 eV with the addition of lignin-biochar. Radical capture experiment and ESR characterization demonstrate that •OH radicals were the main active radical in the photocatalytic process, which increases the radical concentration during the combination of lignin-biochar. Furthermore, the LC/Bi 2 MoO 6 composites were also applied to the degradation of bamboo ECF bleaching effluent, with a higher COD Cr and AOX removal of 75.72 % and 69.64 %, respectively. Herein, this work provides a novel insight for constructing economic and efficient photocatalysts for wastewater remediation and biomass utilization. • A novel LC/Bi 2 MoO 6 composites with enriched oxygen vacancies was prepared. • LC/Bi 2 MoO 6 composites exhibits superior adsorption and visible-light photocatalytic activity for MB and bamboo ECF bleaching effluent degradation. • The photocatalytic mechanism of LC/Bi 2 MoO 6 was proposed.

Facile preparation of visible light-sensitive layered g-C3N4 for photocatalytic removal of organic pollutants

The graphite-phase carbon nitride (g-C3N4) photocatalytic materials were prepared by one-step calcination method to degrade methylene blue (MB) and potassium butyl xanthate (PBX) under visible light irradiation. The prepared g-C3N4 photocatalytic materials were investigated in detail by various characterizations, and the experiments showed that the graphitic phase carbon nitride photocatalytic materials were successfully prepared by the one-step calcination method. The material possesses excellent optical properties and strong visible light absorption, thus achieving photocatalytic degradation of MB and PBX. The catalyst dosage, pH, the initial concentration of pollutants have important effects on photocatalytic activity of MB and PBX. The photocatalytic degradation efficiency was 98.99% for MB and 96.83% for PBX under the optimal conditions (catalyst dosage, initial pollutant concentration and pH value were 500 mg L−1, 20 mg L−1 and 7, respevtively). The photocatalytic mechanisms on MB and PBX were elucidated. ·OH was the key specie for MB, while ·O2− was the key specie for PBX. This study advances the development of photocatalytic technology for mineral wastewater.

Facile In–Situ Construction of Granular–Polyhedral Ag2O–Ag2CO3/Lamellar Bi2O2CO3–Bi2MoO6 Spherical Heterojunction with Enhanced Photocatalytic Activity Towards Pollutants

Bi2MoO6 hollow spheres as precursors, NaOH as etchant, and atmospheric CO2 as carbon source, a granular–polyhedral Ag2O–Ag2CO3/lamellar Bi2O2CO3–Bi2MoO6 spherical heterojunction material with full–spectrum photocatalytic properties was gained through a one step in–situ precipitation approach. Granular Ag2O, polyhedral Ag2CO3, and lamellar Bi2O2CO3 were deposited in–situ on the interior and exterior surfaces of Bi2MoO6 hollow spheres to form nanospheres with a diameter of about 2.8 μm. Using methylene blue (MB) as a model molecule, the effect of NaOH concentration and silver oxide loading on the catalyst activity were investigated to screen out the best catalyst. The results showed that the degradation rate of Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6-1/2–0.1 M was 3.45 and 2.71 times greater than those of Ag2O–Ag2CO3 and Bi2O2CO3–Bi2MoO6-0.1 M, respectively. Meanwhile, the visible light photocatalytic performance of Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6 toward MB and antibiotics (tetracycline hydrochloride (TC), chlorotetracycline hydrochloride (CTC)) were also examined. Results confirm that the heterogeneous materials displayed the boosted photocatalytic activity for MB, TC, and CTC. The boosted activity of the composite Ag2O–Ag2CO3/Bi2O2CO3–Bi2MoO6 is attributed to enhance light utilization, increase surface active sites, and formation of effective heterojunction between Ag2O–Ag2CO3 and Bi2O2CO3–Bi2MoO6. Capture experiments have shown the major active species in the photocatalytic degradation system. On the base of capture experiments and photoelectrochemical experiments, plausible photocatalytic mechanism has been postulated.