Reduction of methylene blue during the ionization process

Methylene blue is readily reduced during the process of ionization in methods as diverse as electron ionization, direct exposure probe electron ionization, direct exposure probe chemical ionization, solid sample secondary ion mass spectrometry, liquid sample secondary ion mass spectrometry and fast atom bombardment mass spectrometry. The reduction of methylene blue need not initially involve the abstraction of hydrogen from the solvent present in the latter two methods.     

Inactivation of dengue virus by methylene blue/narrow bandwidth light system

Peracetic acid was one of the most commonly used disinfectants on solid surfaces in hospitals or public places. However, peracetic acid is an environmental toxin. Therefore, safer, alternative disinfectants or disinfectant systems should be developed. Because photodynamic virus inactivation with methylene blue (MB)/light system has proven effective in blood banking, MB was selected as a photosensitizing agent, dengue virus as a model virus for enveloped RNA viruses, and an in-house fabricated narrow bandwidth light system overlapping the absorption spectrum of MB as the light source. Dengue virus was mixed with different concentrations of MB, and illuminated by the narrow bandwidth light system under different illumination distances and times. The amount of dengue virus remaining was evaluated by plaque forming assays. Results showed that the concentration of MB working solution, illumination intensity of light source, illumination distance and time were four key factors affecting efficiency of virus inactivation using the MB/narrow bandwidth light system. Dengue virus could be completely inactivated at 2.5 m in 5 min when MB >/= 1.0 microg/ml. However, when the distance reached 3.0 m, only greater concentrations of MB (2.0 microg/ml) could completely inactivate virus in a reasonably short time (20 min), and smaller concentrations of MB (1.0 microg/ml) could only completely inactivate virus using longer times (25 min). The results of this virus inactivation model indicate that our MB/narrow bandwidth light system provides a powerful, easy way to inactivate dengue viruses.     

Photocatalytic degradation of methylene blue over N-doped MnWO4 under visible light irradiation

In recent years, the transition-metal tungstate materials with formula MWO₄ have attracted much attention in photocatalytic environmental purification due to their interesting structural and optical properties. Among the others, manganese tungstate (MnWO₄) has attracted particular attention because of its appropriate bandgap energy (2.67 ​eV) with tunable optical and electrical properties, chemical stability, and low cost which makes a suitable photocatalyst. Nevertheless, the manganese tungstate (MnWO₄) based materials are less explored as visible light responsive photocatalysts for wastewater purification. Hence, both parent and N-doped MnWO₄ are synthesized by a hydrothermal method with different nitrogen contents (5, 10, and 15 ​mol%). The as-prepared photocatalysts were characterized by XRD, SEM-EDS, TEM-SAED, FT-IR, UV–Vis DRS, XPS and PL techniques. The photocatalytic activities of the synthesized samples were evaluated by degradation of methylene blue (MB) dye under the visible light irradiation. All the N-doped MnWO₄ samples exhibited enhanced visible-light photocatalytic activity compared to the parent MnWO₄, and the optimal dopant amount of nitrogen was 15 mol% for the best photocatalytic activity. The active species generated during the process of MB degradation are investigated by scavenging experiments. Further, the reusability of the 15 ​mol% N-doped MnWO₄ photocatalyst was examined in three consecutive catalytic runs.     

AgBr/nanoAlMCM-41 visible light photocatalyst for degradation of methylene blue dye

A novel photocatalytic material was synthesized by dispersion of AgBr in nanoAlMCM-41 material. The AgBr/nanoAlMCM-41 sample shows strong absorption in the visible region because of the plasmon resonance of Ag nanoparticles in AgBr/nanoAlMCM-41. The catalysts were characterized using XRD (X-ray diffraction), UV-visible diffused reflectance spectra (UV-vis DRS) and scanning electron microscopy (SEM). The photocatalytic activity and stability of the synthesized catalysts were evaluated for methylene blue (MB) degradation in aqueous solution in the presence of 200 W tungsten filament Philips lamp. Several parameters were examined, catalyst amount, pH and initial concentration of MB, AgBr loading. The effect of dosage of photocatalyst was studied in the range 0.05-1.00 g/L. It was seen that 0.1 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. The support size was obtained about 9-100 nm. In the same way, the average size of AgBr nanoparticles was about 10nm before visible radiation. After visible radiation the average size of AgBr nanoparticles was about 25 nm.     

Photodynamic inactivation of methylene blue and tungsten-halogen lamp light against food pathogen Listeria monocytogenes

The aim of this study was to verify the bactericidal effect and the damage of photodynamic inactivation (PDI) using methylene blue (MB) and tungsten-halogen lamp over Listeria monocytogenes via atomic force microscopy, absorption spectrophotometry, agarose gel electrophoresis, real-time PCR and SDS-PAGE. The obtained data indicated that the viability of L. monocytogenes was ca 7-log reduced by illumination with 10 min tungsten-halogen lamp light under the presence of 0.5 μg mL(-1) MB, and this bactericidal activity against L. monocytogenes of PDI increased proportionally to the concentration of MB and the duration of irradiation. Moreover, after irradiation with MB and visible light, the leakage of intracellular contents was estimated by spectrophotometer at OD(260) and OD(280), which correlated with morphological alterations. Furthermore, genomic DNA cleavage and protein degradation were also detected after PDI treatment. Consequently, breakage of the membrane, damage of the genomic DNA and degradation of bacterial proteins may play an important role in the mechanisms involved in PDI-MB bactericidal activity on L. monocytogenes.     

Determination of methylene blue by resonance light scattering method using silica nanoparticles as probe

A simple and novel method was developed to determine methylene blue(MB) by resonance light scattering(RLS) using silica nanoparticles(SiO_2NPs) as the probe.It was found that MB could enhance the RLS intensity of SiO_2NPs.Moreover,the increase in RLS intensity was linear with the concentration of MB over the range of 0.01-3.0 μg mL~(-1).The limit of detection(LOD) was as low as 4.36 ng mL~(-1)(3σ) and the relative standard deviation(RSD) was 2.4%(n=6).Under the optimum experimental conditions,this proposed method was successfully applied for the determination of MB in aquaculture samples with recoveries between 96.3% and 107%.Possible mechanisms for the RLS enhancement of SiO_2NPs in the presence of MB were also discussed.     

Effect of CO2 activation of carbon xerogels on the adsorption of methylene blue

The effect of physical activation with CO₂ of carbon xerogels, synthesized by pyrolysis of a resorcinol-formaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The activation with CO₂ lead?to carbon materials with micropore volumes ranging from $0.28\ \mathrm{to}\ 0.98~\mathrm{cm}^{3}\,\mathrm{g}_{\mathrm{C}}^{-1}$ . MB-adsorption isotherm studies showed that the increase of micropore volume and corresponding surface area led to: (i) a significant improvement in the capacity of MB-adsorption at monolayer coverage, from $212\ \mathrm{to}\ 714~\mathrm{mg}\,\mathrm{g}_{\mathrm{C}}^{-1}$ , and (ii) an increase of the binding energy related to Langmuir isotherm constant up to 45 times greater than those of commercial microporous activated carbons used as reference (NORIT R2030, CALGON BPL and CALGON NC35). It is proposed that the increase of the binding energy results from chemical cleaning of the O-groups onto carbon surface as a consequence of CO₂-activation, increasing the π–π interaction between MB and graphene layers of the carbon xerogels. Finally, a series of batch kinetics were performed to investigate the effect of CO₂-activation conditions on the mechanism of MB-adsorption. Experimental data were fitted using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. From pseudo-second-order kinetic model, one observes an increase in the initial rate of MB-adsorption from 0.019 to 0.0565 min^?1, by increasing the specific surface area from $630\ \mathrm{to}\ 2180~\mathrm{m}^{2}\,\mathrm{g}_{\mathrm{C}}^{-1}$ via CO₂-activation. Depending on the activation degree of the carbons, two different mechanisms control the MB-adsorption rate: (i) at low activation degree, the intraparticle diffusion is the rate-limiting phenomenon, whereas (ii) at high activation degree, the reactions occurring at the solid/liquid interface are the rate-limiting steps.     

Detection of nucleic acid lesions during photochemical inactivation of RNA viruses by treatment with methylene blue and light using real-time PCR

The mechanism of bacteriophage photoinactivation by methylene blue and light (MB+L) involves genomic RNA damage. In this study, two RNA viruses, Sindbis virus (SINV) and hepatitis C virus were treated by MB+L and their nucleic acids were amplified to show that RNA lesions occurred during inactivation. During MB+L inactivation, the viral load of both viruses was significantly reduced as MB+L exposure increased. The nucleic acid amplification of treated viral RNA was inhibited in a time-dependent manner and the percentage inhibition of amplification reached about 99% after 30 min of treatment. Furthermore, as compared to SINV viral infectivity detected by quantification of the 50% tissue culture infective dose (TCID(50)), the inhibition of SINV RNA amplification strongly correlated with a decrease in in vitro infectivity (R(2) > 0.94), suggesting that RNA serves as the main target during MB+L inactivation.     

Q beta bacteriophage photoinactivated by methylene blue plus light involves inactivation of its genomic RNA

Methylene blue (MB) is being used as a sensitizer for the photodynamic inactivation of viral contaminants, including the human immunodeficiency virus, in blood and blood components used in medical treatment. We recently showed that oxygen-dependent photodynamic inactivation of the RNA bacteriophage Q beta with MB plus light (MB + L) is associated with the formation of 8-oxo-7,8-dihydroguanine, protein carbonyls, RNA-protein crosslinkages and minor amounts of RNA strand breaks. We report herein, with the use of infectious RNA assays, that the lethal lesions in Q beta phage following MB + L exposure can be accounted for, and thereby most likely reside in, the RNA component of the phage but that the protein component of the virion contributes to the inactivation. The formation of RNA-protein crosslinkages as the primary inactivating type of lesion is put forth as the most probable model of the inactivation mechanism due to the sensitivity with which RNA-protein crosslinks are formed in response to MB + L exposure and the expectation of the powerful inactivating power of this type of lesion.     

Pulse radiolysis of methylene blue and toluidine blue in PVA

Pulse radiolysis experiments were carried out with aqueous solutions of thionine dye methylene blue (MB) and toluidine blue in the presence of polyvinyl alcohol. The transient spectra obtained show maxima at 400 and 880 nm and are assigned to the respective semiquinone radical anions. The semiquinone radical decayed by a second order process. Furthermore, MB in PVA films were bleached by γ-radiolysis and the change in absorption was found to be linear with the dose.     

A sensitive resveratrol assay with a simple probe methylene blue by resonance light scattering technique

A novel resonance light scattering (RLS) method was developed for the determination of resveratrol based on the interaction between resveratrol and methylene blue (MB). It was found that at pH 8.69, the weak RLS intensity of MB was remarkably enhanced by the addition of trace amount of resveratrol with the maximum peak located at 385.0 nm. Under the optimum conditions, a good linear relationship between the enhanced RLS intensities and the concentrations of resveratrol was obtained over the range of 2.0-14.0 μg ml(-1) with the detection limit (3σ) of 0.63 μg ml(-1). The results of the analysis of resveratrol in synthetic samples and human urine are satisfactory, which showed it may provide a more sensitive, convenient, rapid and reproducible method for the detection of resveratrol, especially in biological and pharmaceutical field. In this work, the characteristics of RLS, absorption and fluorescence spectra of the resveratrol-MB system, the influencing factors and the optimum conditions of the reaction were investigated.     

Modeling the mechanism involved during the sorption of methylene blue onto fly ash

Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using fly ash as an adsorbent. Operating variables studied were initial dye concentration, fly ash mass, pH, and contact time. Maximum color removal was observed at a basic pH of 8. Equilibrium data were represented well by a Langmuir isotherm equation with a monolayer sorption capacity of 5.718 mg/g. Sorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics. Rate constants at different initial concentrations were estimated. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D(i) values were estimated at different initial concentrations and the average value was determined to be 2.063 x 10(-9)cm2/s. Analysis of sorption data using a Boyd plot confirms the particle diffusion as the rate-limiting step for the dye concentration ranges studied in the present investigation (20 to 60 mg/L).     

Study of adsorption of methylene blue and new methylene blue in liquid-solid interface by slab optical waveguide spectroscopy

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid–solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. Effect of pH on adsorption on MB and NMB was investigated. Binding rate constant analysis showed that both MB and NMB on bare SOWG demonstrates larger association constants than those on ODS-SOWG. Interactions of MB and NMB on bare SOWG and ODS-SOWG were analyzed by molecular mechanics calculation method. The binding energy change was in the following order: E_NMB–bare > E_MB–bare > E_NMB–ODS > E_MB–ODS.     

亚甲基蓝光度法测苯唑西林

在pH8.6～9.8的条件下,亚甲基蓝与苯唑西林反应生成蓝色离子缔合物。体系的最大吸收波长位于606nm,线性范围为0～4.0mg/L,表观摩尔吸光系数为2.60×104L·mol-1.cm-1,探讨了适宜的反应条件、方法的精密度及可靠性。方法已用于药物中阿莫西林的测定。     

Simultaneous determination of methylene blue and new methylene blue by slab optical waveguide spectroscopy and artificial neural networks

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. The simultaneous determinations of both MB and NMB were explored by flow injection SOWG spectrophotometric analysis and artificial neural networks (ANNs) for the first time. Concentrations of MB and NMB were estimated simultaneously with the ANNs. Results obtained with SOWG were compared with those got by conventional UV-visible spectrophotometry.     

Photocatalytic degradation of methylene blue on Fe3+-doped TiO2 nanoparticles under visible light irradiation

Fe³⁺-doped TiO₂ composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of Fe³⁺/TiO₂ nanoparticles under visible light irradiation. The influence of doping amount of Fe³⁺ (ω: 0.00%–3.00%) on photocatalytic activities of TiO₂ was investigated. Results show that the size of Fe³⁺/TiO₂ particles decreases with the increase of the amount of Fe³⁺ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe³⁺ can control the conversion of TiO₂ from anatase to rutile. The doping amount of Fe³⁺ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The appropriate doping of Fe³⁺ can markedly increase the catalytic activity of TiO₂ under visible light irradiation. __________ Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)]     

三角形Au@TiO2介孔催化剂可见光降解亚甲蓝

利用溶胶凝胶法制备出一种三角形Au@TiO₂核壳材料。经过水热晶化,该材料膨胀至300 nm,壳层TiO₂晶化为介孔锐钛矿相,但核心三角形Au颗粒的形貌保持不变。采用粉末X射线衍射(PXRD)、ζ电位、高分辨透射电子显微镜(HRTEM)、热重分析(TGA)、光致发光(PL)光谱、光电流(i-t)以及光催化降解技术,对样品的结构和性能进行了系统、详细的检测与分析。经过晶化处理的Au@TiO₂在可见光波段的光降解亚甲蓝性能比未晶化时有了显著的提升, 1 mg·mL^-1 Au@c-TiO₂可以在可见光照射1 h后实现对60 mg·L^-1亚甲蓝全降解。电子顺磁共振(EPR)测试表明·O₂^-和·OH两种自由基对光降解起到了很大作用。通过综合分析实验结果和时域有限差分(FDTD)分析,探究了催化反应的机理。     

Bismuth-containing layered double hydroxide as a novel efficient photocatalyst for degradation of methylene blue under visible light

Layered double hydroxide (LDH)-based photocatalysts have emerged as a very promising candidate to replace TiO₂, owing to their unique layered structure, tunable band gaps, low cost, ease of scale-up, and good photocatalytic activity. Bismuth-doped ZnCr-LDH was studied as photocatalyst in the photodegradation of methylene blue (MB). The structure and morphology of ZnCr-LDH and ZnCrBi-LDH were characterized using a different mode of delegated tools, e.g., FTIR, XRD, UV–Vis, FESEM–EDX, and TEM measurements. FESEM and TEM image of the synthesized LDHs showed that the synthesized LDH is smooth overlapping crystals, and they are approximately in hexagonal form. The material was found to be a good photocatalyst for degradation of methylene blue in visible light, and the results showed that the photocatalytic activity of ZnCrBi-LDH sample is higher than of ZnCr-LDH sample. According to the kinetic data, the reaction rate constant of ZnCrBi-LDH is approximately four times higher than the apparent reaction rate constant of ZnCr-LDH. The catalytic activity was retained even after four methylene blue degradation cycles, indicating that the LDH could be an important addition to the field of wastewater treatment.