MB Molecules Research Articles

Modulation of release behaviors of methylene blue from degradable silica-methylene blue@octacalcium phosphate powders with different shell structures

Abstract Methylene blue-loaded silica (silica-MB) was coated by a shell of polyethylene glycol (PEG), citrate ions and octacalcium phosphate (OCP) through a facile sol–gel method. The influences of molecular weight of PEG, addition amount of PEG and citric acid on the phase, morphology and chemical composition of samples were characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. Compared with that of silica-MB, the sustained-release behavior of MB from silica-MB@OCP was sensitive to the shell structure and the pH value of culture solution. At each time interval, the ratio of absorbance of MB monomers over that of MB dimers released from silica-MB@OCP was higher than that from silica-MB, indicating that the significant influence of interaction density among the network of PEG, citrate ions and OCP on the release behavior of MB. Silica-MB and silica-MB@OCP were degraded when MB molecules diffused to the culture solution from solid silica matrix, which would shed light on the self-destruction investigation of drug/drug carrier systems in the biological system.

Electrically-charged recyclable graphene flakes entangled with electrospun nanofibers for the adsorption of organics for water purification.

Graphene flakes were entrapped between nylon 6 nanofiber layers and the resulting assembly was used as a recyclable water purification membrane. Water purification was achieved via adsorption of the model organic pollutant (methylene blue; MB) on the surface of the graphene component. Desorption of these MB molecules was achieved by applying high voltage, which increased the removal efficiency of the recycled membrane. The adsorption and desorption mechanisms were evaluated in detail. The material characteristics of the membrane were analyzed by scanning electron microscopy, Raman, UV-visible, and Fourier transform infrared analyses.

Reactivity of iron-based nanoparticles by green synthesis under various atmospheres and their removal mechanism of methylene blue

The reduction degradation pathway of MB molecules.

Synthesis of AgBr/Ag4P2O7 composite photocatalyst and enhanced photocatalytic performance

Ag4P2O7 and AgBr/Ag4P2O7 photocatalysts were synthesized by a simple precipitation reaction, and their structures were characterized by X-ray powder diffraction, scanning electronic microscopy, Brunauer–Emmett–Teller surface area analysis, X-ray photoemission spectroscopy, UV–vis absorption spectroscopy, photoluminescence, and surface photovoltage techniques. Photocatalytic degradations of methylene blue over Ag4P2O7 and AgBr/Ag4P2O7 were also studied under visible light irradiation. AgBr/Ag4P2O7 exhibited excellent photocatalytic efficiency, with the activity higher than that of Ag4P2O7. The band gap and valence band of Ag4P2O7 were 2.67 eV and 1.93 eV, respectively. Ag4P2O7 failed to produce OH radicals by directly oxidizing OH− because the oxidation potential of OH− was 2.7 eV. Therefore, electrons excited by light reacted with O2 to produce O2− radicals that then formed OH radicals. Finally, OH radicals oxidized MB molecules. The matching energy bands of Ag4P2O7 and AgBr in the AgBr/Ag4P2O7 heterocatalysts effectively separated the photo-induced charges, which may enhance the photocatalytic activity of Ag4P2O7.

Spectroscopic investigation of colloidal CdS quantum dots–methylene blue hybrid associates

Spectral properties of hydrophilic associates of colloidal CdS quantum dots (QDs) with methylene blue molecules (MB) prepared by sol–gel method have been studied. The two basic types of hybrid associates were found using FTIR spectra technique. The first-type associates are characterized by planar location of MB heterocycle on QDs spherical interface. In this case MB dimerization is not observed. Both nitrogen and sulfur heteroatoms and double =N+–(CH3)2 bonds of MB are participants of association which causes to conformation of MB heterocycle and π-conjugation length decrease. In UV–Vis absorption and luminescence spectra blue shift of MB peaks for QD-MB associates in comparison with MB spectra in solutions and gelatin was found. The second type of association mostly involves MB nitrogen heteroatoms and CdS QDs interface atoms. At the same time, peaks of UV–Vis and luminescence spectra are red shifted. In this case, dimerization manifestation of MB in QD-MB associates was found. Using the time correlated single photon counting technique resonance electronic excitation energy transfer from recombination luminescence center of CdS QDs to MB molecules was found. Its efficiency is in the range of 0.36–0.51.

NIR-light-induced surface-enhanced Raman scattering for detection and photothermal/photodynamic therapy of cancer cells using methylene blue-embedded gold nanorod@SiO2 nanocomposites

Methylene blue-loaded gold nanorod@SiO2 (MB-GNR@SiO2) core@shell nanoparticles are synthesized for use in cancer imaging and photothermal/photodynamic dual therapy. For the preparation of GNR@SiO2 nanoparticles, we found that the silica coating rate of hexadecylcetyltrimethylammonium bromide (CTAB)-capped GNRs is much slower than that of PEGylated GNRs due to the densely coated CTAB bilayer. Encapsulated MB molecules have both monomer and dimer forms that result in an increase in the photosensitizing effect through different photochemical pathways. As a consequence of the excellent plasmonic properties of GNRs at near-infrared (NIR) light, the embedded MB molecules showed NIR light-induced SERS performance with a Raman enhancement factor of 3.0 × 1010, which is enough for the detection of a single cancer cell. Moreover, the MB-GNR@SiO2 nanoparticles exhibit a synergistic effect of photodynamic and photothermal therapies of cancer under single-wavelength NIR laser irradiation.

Methylene blue covalently attached to single stranded DNA as electroactive label for potential bioassays

Methylene blue is an electroactive molecule that has been employed for the detection of the DNA hybridization event in electrochemical sensors. However, its use as a covalent label is very scarce and in most of the cases, non-covalent interactions (hydrophobic, electrostatic) are employed. Although it has advantages as simplicity and fewer number of procedure steps, the covalent attachment is less exploited in the development of these sensors. In this article, the electrochemical behavior of methylene blue attached to different DNA-strands is studied. Several lengths (15- and 30-mer) and different degree of DNA modification (MB-DNA, MB-DNA-MB and MB-DNA-SH) have been studied. The highest signals were obtained for longer strands with two MB molecules. In all the cases the signal is enhanced by CNT-nanostructuration of the electrode. Adsorption on these modified screen-printed electrodes allowed the amplification by employing an accumulation time. In this way, a sensitivity of −0.2864μAμM−1 and a limit of detection of 800nM for a 120s accumulation time were obtained.

Atomistic simulations of thiol-terminated modifiers for hybrid photovoltaic interfaces

Small aromatic molecules such as benzene or pyridine derivatives are often used as interface modifiers (IMs) at polymer/metal oxide hybrid interfaces. We performed a theoretical investigation on prototypical thiol-terminated IMs aimed at improving the photovoltaic performances of poly(3-hexylthiophene)/TiO2 devices. By means of first-principles calculations in the framework of the density functional theory we investigate 3-furanthiol (3FT), 4-mercaptobenzoicacid (4MB), and 6-isoquinolinethiol (6QT) molecules. We discuss the role of these molecules as modifiers alternative to 4-mercaptopyridine (4MP) which has recently shown to induce a large improvement in the overall power conversion efficiency of mesoporous films of TiO2 infiltrated by poly(3-hexylthiophene). The IMs investigated are expected to keep the beneficial features of 4MP giving at the same time the possibility to further tune the interlayer properties (e.g., its thickness, stability, and density). Dense interlayers of 6QT turn out to be slightly unstable since the titania substrate induces a compressive strain in the molecular film. On the contrary, we predict very stable films for both 3FT and 4MB molecules, which makes them interesting candidates for future experimental investigations.

Dye adsorption of mesoporous activated carbons produced from NaOH-pretreated rice husks

In continuation of previous work on utilizing rice husks, this study aimed to prepare mesoporous activated carbons using residues of sodium hydroxide-pretreated RHs, and then examine their dye adsorption performance. The influences of the activation temperature and activation time on the surface area, pore volume, and pore radius of the activated carbon were investigated based on nitrogen adsorption/desorption isotherms and transmission electron microscopy. The adsorptive behavior of the mesoporous activated carbons obtained under optimum preparation conditions was evaluated using methyleneblue as the model adsorbate. The adsorption kinetics was studied by pseudo-first-and pseudo-second-order models, and the adsorption isotherms were studied by Langmuir and Freundlich models. The pseudo-second-order model and Langmuir isotherm were found to fit well the adsorption characteristics of the as-prepared mesoporous activated carbons. Thermodynamic data of the adsorption process were also obtained to elucidate the adsorption thermo-chemistry between the activated carbons produced from NaOH-pretreated RHs and MB molecules.

Encapsulation of Photosensitizer into Multilayer Microcapsules by Combination of Spontaneous Deposition and Heat‐Induced Shrinkage for Photodynamic Therapy

Annealing of PDADMAC/PSS multilayer microcapsules assembled on PSS-doped CaCO(3) particles at 80 °C for 30 min reduces their size dramatically from 6.9 ± 0.3 to 3.1 ± 0.5 µm. Methylene blue molecules are encapsulated by spontaneous deposition and post-annealing with a concentration of 22 mg · mL(-1), which is 1000 times higher than the feeding value. The unreleased MB molecules are retained stably for a long time, which are then protected by the capsules against reductive enzymes and keep their photodynamic activity. The viability of HeLa cells incubated with the MB-loaded capsules decreases sharply from ≈ 75 (dark cytotoxicity) to ≈ 20% after irradiation with a laser at 671 nm and 60 J · cm(-2) for 75 s.

Effect of pH Solution on the Optical Properties of Cationic Dyes in Dye/Maghnia Montmorillonite Suspensions

The interaction of three cationic dyes (Methylene blue, MB; Neutral red, NR; and Malachite green oxalates, MG) with montmorillonite clay from Maghnia deposit in aqueous suspensions was investigated using visible absorption spectroscopy. The stability of the optical properties of dyes in aqueous solutions and in dye/clay suspension was assessed in terms of the absorption bands maxima as a function of pH. The optimal pH for favorable adsorption of the dyes, i.e. ≥ 90% has been achieved in aqueous solutions at 6 for NR and at 7 for both MB and MG respectively. The adsorption of MB leads to the methacromatic effect. MB agglomerates occurred predominantly in the clay with high charge density, even with low charge density. The redistribution of MB molecules over the surface of clay at higher acidic medium causing a reduction of the dye aggregation. However, the interactions of NR and MG with clay differ in certain aspects from those of MB. The adsorption of NR is accompanied by a red shift of the main band at low pH, whereas, the conjugate form of NR, remains stable at neutral and higher pH. A blue shift of the main band is observed at pH 6, which is consistent with externally and internally adsorbed dye cations. For MG, a slight stability of the main bands in clay suspension at acidic and neutral pH, while, the band attributed to MG cations shifs to longer wavelengths at pH 9. To explain the relationship between the layer charge density and the adsorption, so- colled model 2-pKa of surface complexation (SCM) was developed.

Catalytic property of TiO2/PS complex nanoparticles prepared via a novel TSM

With an average size of 7 nm and good catalytic property under the natural light, TiO2/PS complex nanoparticles were successfully prepared through a novel two-step method (TSM) from TiCl4, used as both the catalyst for polymerization of styrene and Ti source, and styrene monomer and characterized by TG-DTA, XRD, IR, TEM and UV-Vis techniques. Its catalytic property was evaluated by the decolourization and degradation of dye MB solution under the natural light. From its TEM, the particles with an average size of 7 nm were observed without the separation of TiO2 and PS phases, i.e., TiO2/PS was hybrid material in nanosize scale. IR spectrum of TiO2/PS showed increase of unsaturated degree and growth of the group C=O on the chain of PS and Ti–O–C coordination bond between TiO2 and PS. The nanosize of the TiO2/PS complex particles and the conjugated structure and polar groups of PS were advantageous to good adsorptive property and strong interaction of PS and TiO2. And they brought multi-functions of inorganic and organic materials in the single material. Catalytic experiments indicated that the complex nanoparticles could catalytically degrade dye MB solution in 10 min under the natural light while P25 basically showed adsorptive property for MB molecules under the same conditions.

Surface Plasmons Control the Dynamics of Excited Triplet States in the Presence of Gold Nanoparticles

Aqueous gold nanoparticles (AuNPs) cause a large increase in the yield of methylene blue triplets ((3)MB*) obtained upon 650 nm laser excitation as a result of surface plasmon field interactions that can be described as transmitter-receiver antenna effects. Two distinct (3)MB* populations are observed; a fast decaying one (tau(T) approximately 25 ns) is believed to be due to molecules on the AuNP surface at the time of excitation and is described as static quenching. A longer lived (3)MB* population has lifetimes in the tens of microseconds but is subject to an anomalously high rate constant for a AuNP quenching of 6.4 x 10(13) M(-1) s(-1). This ultrafast quenching is attributed to a nonrandom distribution caused by the AuNP plasmon field that preferentially excites MB molecules located in the proximity of the AuNP where they are subject to antenna type interactions with the nanoparticle and are spatially predisposed for efficient quenching.

Multiple Exciton Dissociation in CdSe Quantum Dots by Ultrafast Electron Transfer to Adsorbed Methylene Blue

Multiexciton generation in quantum dots (QDs) may provide a new approach for improving the solar-to-electric power conversion efficiency in QD-based solar cells. However, it remains unclear how to extract these excitons before the ultrafast exciton-exciton annihilation process. In this study we investigate multiexciton dissociation dynamics in CdSe QDs adsorbed with methylene blue (MB(+)) molecules by transient absorption spectroscopy. We show that excitons in QDs dissociate by ultrafast electron transfer to MB(+) with an average time constant of approximately 2 ps. The charge separated state is long-lived (>1 ns), and the charge recombination rate increases with the number of dissociated excitons. Up to three MB(+) molecules per QD can be reduced by exciton dissociation. Our result demonstrates that ultrafast interfacial charge separation can effectively compete with exciton-exciton annihilation, providing a viable approach for utilizing short-lived multiple excitons in QDs.

Incorporation of Ag nanoparticles into membrane mimetic systems composed by phospholipid layer‐by‐layer (LbL) films to achieve surface‐enhanced Raman scattering as a tool in drug interaction studies

AbstractThe synergistic effect produced by nanoparticles when incorporated into different systems used as analytical tools represents a growing research field nowadays. On the other hand, the study of interactions involving pharmacological drugs and biological membranes using phospholipids as mimetic systems is a research field already well established. Here, we combine both the anionic phospholipid dipalmitoyl phosphatidyl glycerol (DPPG) and negative Ag nanoparticles (AgNP) to form layer‐by‐layer (LbL) multilayered films using the cationic polymer poly(allylamine hydrochloride) (PAH) as the supporting polyelectrolyte, which were further investigated in the presence of a phenothiazine compound (methylene blue—MB). The molecular architecture of the LbL films in terms of controlled growth, morphology with micro and nanometer spatial resolutions, and dispersion of both AgNP and MB within the DPPG matrix was determined combining spectroscopy [ultraviolet–visible (UV–Vis) absorption and micro‐Raman spectroscopy] and microscopy [scanning electron microscopy (SEM) and atomic force microscopy (AFM)]. The results showed that the LbL films can be grown in a controlled way at nanometer thickness scale with the surface morphology susceptible to the presence of both AgNP and MB. The surface‐enhanced phenomenon was applied to investigate the LbL films taking the advantage of the strong surface‐enhanced resonance Raman scattering (SERRS) signal presented by the MB molecules. Besides, as MB is a pharmacological drug of interest, its molecular arrangements when dispersed in LbL films containing DPPG, which is the biological membrane mimetic system here, were investigated. In this case, the AgNP played a key role in achieving the MB SERRS signal. Copyright © 2009 John Wiley & Sons, Ltd.

Fabrication and characterization of Meldola's blue/zinc oxide hybrid electrodes for efficient detection of the reduced form of nicotinamide adenine dinucleotide at low potential

We report the synthesis and the electrochemical properties of hybrid films made of zinc oxide (ZnO) and Meldola's blue dye (MB) using cyclic voltammetry (CV). MB/ZnO hybrid films were electrochemically deposited onto glassy carbon, gold and indium tin oxide-coated glass (ITO) electrodes at room temperature (25 ± 2 °C) from the bath solution containing 0.1 M Zn(NO 3) 2, 0.1 M KNO 3 and 1 × 10 −4 M MB. The surface morphology and deposition kinetics of MB/ZnO hybrid films were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) techniques, respectively. SEM and AFM images of MB/ZnO hybrid films have revealed that the surfaces are well crystallized, porous and micro structured. MB molecules were immobilized and strongly fixed in a transparent inorganic matrix. MB/ZnO hybrid films modified glassy carbon electrode (MB/ZnO/GC) showed one reversible redox couple centered at formal potential ( E 0′) −0.12 V (pH 6.9). The surface coverage ( Γ) of the MB immobilized on ZnO/GC was about 9.86 × 10 −12 mol cm −2 and the electron transfer rate constant (ks) was determined to be 38.9 s −1. The MB/ZnO/GC electrode acted as a sensor and displayed an excellent specific electrocatalytic response to the oxidation of nicotinamide adenine dinucleotide (NADH). The linear response range between 50 and 300 μM NADH concentration at pH 6.9 was observed with a detection limit of 10 μM (S/N = 3). The electrode was stable during the time it was used for the full study (about 1 month) without a notable decrease in current. Indeed, dopamine (DA), ascorbic acid (AA), acetaminophen (AP) and uric acid (UA) did not show any interference during the detection of NADH at this modified electrode.

Exciplexes or ground state complexes of (dibenzoylmethanato)boron difluoride and benzene derivatives? A study of their optical properties revisited via liquid state investigations and structure calculations

(Dibenzoylmethanato)boron difluoride (DBMBF2) was found to form with benzene (B) and its methylated derivatives (MB) in cyclohexane (cHex) two types of ground state complexes. The first complexes with low stoichiometries 2 : 1, 1 : 1 and 1 : 2 do not fluoresce when they are excited. On the other hand, the ground state complexes with high stoichiometry, DBMBF2-(B)(n) or DBMBF2-(MB)(n) (with n>> 2), exhibit a strong fluorescence in their excited states. These findings differ from the previous results, where the strongly fluorescing complexes have been argued to be the 1 : 1 and 1 : 2 exciplexes, complexes of the singlet excited state of DBMBF2 with one or two B or MB molecules. These differences are discussed in terms of the solute-solute and solute-solvent interactions when DBMBF2 and MB are solutes in cyclohexane or when MB is a co-solvent of cyclohexane in binary mixtures of DBMBF2. We also argue that the use of well-suited analytical methods is important for the determination of the nature of the various complexes. Furthermore, to understand the nature of the interactions between benzene and DBMBF2 molecules, we attempt to predict the sites of interaction between DBMBF2 and benzene molecules by determining theoretically the structure of the 1 : 1 complex.

Methylene Blue Dimerization Does Not Interfere in Surface-Area Measurements of Kaolinite and Soils

AbstractMethylene blue (MB) was adsorbed from aqueous solutions onto a kaolinite and four soil samples to determine the effects of MB dimerization on the measured surface area. Adsorption isotherms were prepared using four adsorbing solutions containing, respectively, 9, 46, 71, and 83% of MB molecules in the dimeric state. Langmuir-type isotherms were obtained in each case. The results indicate that equilibration occurs quickly. The aggregation state of MB molecules at the surface does not depend on the aggregation state in the initial adsorbing solutions, but on the final equilibrium concentration of MB. A comparison with the specific surface area measured by adsorption of ethylene glycol monoethyl ether indicates that MB adsorbs as a monomer, regardless of the aggregation number in solution. This result occurs owing to the strength of monomer-surface and monomer-monomer interactions. If monomer-surface interactions are favored, the MB dimer adsorbs in the monomeric form. If monomer-monomer interactions are favored, dimer adsorption may occur. The visible spectra of adsorbed molecules indicated that MB was present at the surface as a mixture of monomeric and dimeric species. These results suggest that dimers are formed in the contact region between two aggregating particles.

Self-aggregation of Methylene Blue in aqueous medium and aqueous solutions of Bu4NBr and urea

The self-aggregation of Methylene Blue [MB] (1×10−6–4×10−4 M) in water and in aqueous solutions of Bu4NBr (0.1–0.3 M) and urea (0.1–4 M) has been investigated by recording electronic spectra in the wavelength range 550 to 700 nm. Analysis of the spectral data yielded the dimer dissociation constant, and individual characteristic monomer and dimer spectra. By applying the exciton model for the first time, the interaction energy between the MB molecules in the dimer species has been evaluated. Further, information about the dimer geometry and the twist angle between the dipoles of the MB molecules in the dimer species has been obtained. Similar data have also been obtained for solutions of MB in aqueous urea and Bu4NBr solutions. The significant observation is the change in the dimer geometry from sandwich type to end-on-end type in the presence of urea and Bu4NBr. It is observed that the contribution to the interaction energy is mainly from van der Waal's type and dispersion forces, in addition to short-range forces involving multipoles. However, the contribution from hydrogen-bonding interactions between MB and water molecules is found to be significantly low. It is proposed that water structural effects and hydrophobic interactions are the major factors in the phenomenon of aggregation.

Trapped electrons in 2-methylbutane glass at 4.2 K

ESR studies were carried out on glassy and polycrystalline 2-methylbutane (2MB) γ-irradiated at 77 and 4.2 K. At 77 K in a polycrystalline matrix the secondary and tertiary 2MB radicals are stabilized, whereas in glassy samples the paramagnetic species are not observed at all. However, at 4.2 K in 2MB glass not only radicals but also electrons are trapped with very high efficiency G( e - t) = 1.3. The radiation yield of trapped electrons in 2MB glass at 4.2 K is about a factor of 2 higher than in 2-methylpentane and 2-methylhexane glasses. This result is suggested to be due to the low viscosity of 2MB glass at 4.2 K and to the spherical shape of 2MB molecules.