Methylene Blue Reduction Research Articles

Fe3O4@SiO2 nanoparticles-supported Cu(II) complex: An efficient and reusable nanocatalyst for treating environmental pollutants in aqueous medium

The present research aims to design and produce a unique and magnetically rectifiable catalyst through immobilizing copper(II) over the Fe3O4@SiO2 nanoparticles (NPs) surface. The fabricated catalysts were determined as VSM, EDS, XRD, FT-IR, TG-DTG, and FESEM procedures. The prepared catalyst demonstrated superior catalytic performance in the reduction of Cr(VI) and 4-nitrophenol (4-NP) and degradation of organic dyes like methylene blue (MB) and congo red (CR) in aqueous media. Remarkable attributes of this method are high efficiency, removal of a homogeneous catalyst, easy recovery from the reaction mixture, and uncomplicated route. The amount of activity in this catalytic system after several stages of recovery and reuse was almost constant. In general, NaBH4 induced degradation/reduction of MB, CR, and 4-NP, and formic acidinduced reduction of chromium(VI) to chromium(III) catalyzed with prepared catalyst within a very short time. Moreover, compared to related research, this catalyst showed less reaction time.

Tradition of raw milk consumption and its health impact among people living in the coastal regions of Bangladesh

Milk is a nutrient-rich liquid food for human and animals. However, owing to its complex biochemical structure and high water activity, it serves as an outstanding microorganism growth medium under suitable conditions. People in Bangladesh's coastal areas have a lifestyle and tradition that includes drinking raw milk for nutrition or as an energy drink, which presents a health risk to them. The present cross-sectional study was carried out to determine the reasons for drinking raw milk in coastal areas, as well as the public health impact of doing so. A total of 100 respondents were interviewed and subsequently, milk samples were collected for quality testing through methylene blue reduction test (MBRT). Among 100 respondent 70 were consumers and 30 were farmers. Results showed that the samples of farmers were better than that of consumers. The majority of raw milk consumers were male who thought raw milk was more nutritious than heat-treated milk. Furthermore, the majority of them were professionally engaged in farming. Both consumers and farmers had less educational qualifications, managed their cattle in dirty environments, practiced extensive grazing system on communal grazing areas and around one fourth of them vaccinated their animals. Furthermore, the findings revealed that 40% of respondents were between the ages of 35 and 45, with 62% reporting no health complications as a result of drinking raw milk and the remainder reporting mainly gastrointestinal problems. According to the findings of this report, the quality of raw cow milk was poor; unhygienic practices and poor animal husbandry at farm level predisposed farmers, consumers and the public to risk of contracting milk-borne infections and associated bacterial resistances. It is recommended that veterinarians, extension officers and all stakeholders should play their roles in ensuring safe quality milk supply to consumers.
 Asian Australas. J. Biosci. Biotechnol. 2021, 6 (1), 10-18

Development of alginate@tin oxide–cobalt oxide nanocomposite based catalyst for the treatment of wastewater

In this study, tin oxide‑cobalt oxide nanocatalyst was prepared by a simple method, which grew in spherical particles with an average diameter of 30 nm. Tin oxide–cobalt oxide was further wrapped in alginate polymer hydrogel (Alg@tin oxide–cobalt oxide), and both materials were utilized as nanocatalysts for the catalytic transformation of different pollutants. Tin oxide–cobalt oxide and Alg@tin oxide–cobalt oxide nanocatalysts were tested for the catalytic reduction of 4-nitrophenol, congo red, methyl orange, methylene blue (MB) and potassium ferricyanide in which sodium borohydride was used as a reducing agent. Tin oxide–cobalt oxide and Alg@tin oxide–cobalt oxide nanocatalysts synergistically reduced MB in shorter time (2.0 and 4.0 min) compared to other dyes. The reduction conditions were optimized by changing different parameters. The rate constants for MB reduction were calculated and found to be 1.5714 min−1 and 0.6033 min−1 using tin oxide–cobalt oxide and Alg@tin oxide–cobalt oxide nanocatalysts, respectively. Implementing Alg@tin oxide–cobalt oxide nanocatalyst toward MB reduction in real samples proved its efficacy in sea and well water samples. The catalyst could be easily recovered, recycled and revealed a minimal loss of nanoparticles, which offering a competition and replacement with reputable commercial catalysts.

Concentration of 2,3 bisphosphoglycerate in cattle affected with acute ruminal acidosis.

The main objective of the study conducted here was to estimate the concentration of 2,3‐Bisphosphoglycerate (2,3‐BPG), 1,3‐Bisphosphoglycerate (1,3‐BPG), bisphospho‐glycerate mutase (BPGM) and 3‐phosphoglycerate (3PG) in cattle clinically diagnosed with acute ruminal acidosis. A secondary objective was to examine the physical and chemical characteristics of the ruminal fluid in affected cattle. A total of 20 cattle clinically diagnosed with acute ruminal acidosis and eight clinically normal cattle were included in this study. The results showed that decrease of ruminal pH changed the ruminal fluid colour, odour and consistency, as well as decreased the sedimentation time, increased the methylene blue reduction time, and decreased ruminal microflora motility. The study indicated that the concentration of 2,3‐BPG, BPGM and BPGP decreased with the decrease of ruminal pH, while 3‐PG concentration was not affected with the decrease of ruminal pH. In conclusion, 2,3‐BPG could play a role in the pathogenesis of ruminal acidosis, and thus, the intravenous administration of sodium bicarbonate is important, particularly in severe cases, to correct any systemic acidosis that can decrease 2,3‐BPG concentration and results in tissue hypoxia.

A novel AgMoOS bimetallic oxysulfide catalyst for highly efficiency catalytic reduction of organic dyes and Chromium (VI)

To detoxify chemical pollutants discharge from industries, the researchers pursue always to get new, cost-effective, environmentally friendly and efficient technologies. Herein, novel silver molybdenum oxysulfide (AgMoOS) catalyst which is monoclinic structure with spherical shape nanoparticle and uniform distribution of its elemental composition was successfully synthesized by a facile method. The catalytic performance of AgMoOS was employed for the reduction of methylene blue (MB), methyl orange (MO), 4-Nitrophenol (4-NP), Rhodamine B (RhB) and Chromium (VI) in presence of NaBH4 under dark condition and a fastest reduction activity was obtained with 2-AgMoOS. A 10 mg of 2-AgMoOS completely reduced 100 mL of 20 ppm of MB, MO, 4-NP, RhB and Cr6+ within 6, 6, 15, 24 and 24 min, respectively and the reduction kinetic data indicated that the catalytic activity of all AgMoOS catalysts toward these chemical pollutants followed the order: MB > MO > 4-NP > RhB > Cr6+ ions. The re-usability data toward the reduction of MB, cyclic voltammogram, XPS and XRD spectrum of 2-AgMoOS after the reaction were confirmed a good stability and durability of AgMoOS catalyst. Hence, AgMoOS is an efficient catalyst and provides a practical application for toxic organic dyes degradation and toxic inorganic pollutants containing waste water treatment and other environmental issues.

Biosynthesis of Silver Nanoparticles Using Malva Sylvestris Flower Extract and Its Antibacterial and Catalytic Activity

In this study, silver nanoparticles (AgNPs) were synthesized by using Malva sylvestris flower extract. Different parameters such as, pH, extract volume, silver nitrate concentration, temperature and reaction time were controlled correctly and the effect of them on the synthesis of nanoparticles were investigated. Some of techniques like, UV-Vis, FTIR, SEM, TEM, and XRD were used to analyze the characteristics of AgNPs. According to our results, the shape and size of nanoparticles were spherical and about 20 - 30 nm range, respectively. In addition, the surface plasmon resonance (SPR) of nanoparticles occurred in 445 nm. The effect of catalytic activity AgNPs synthesized on the reaction Sodium Borohydride (NaBH4) with Methylene Blue (MB) and its antibacterial activity on (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonellatyphy murium) as a references bacteria have been studied. Also, the effect of Malva sylvestris flower extract on them was measured and analyzed precisely. The results showed ability of catalytic activity on the reduction of MB. Further, synthesized nanoparticles have significant ability antibacterial activity against gram negative bacteria (Escherichia coli and salmonella typhy murium).

Enhanced visible-light photocatalytic activity and antibacterial behaviour on fluorine and graphene synergistically modified TiO2 nanocomposite for wastewater treatment

ABSTRACT The photocatalytic reduction of methylene blue was recognized as an economical and effective way for dye removal. To enhance photocatalytic activity under visible-light condition, fluorine and graphene synergistically modified TiO2 (F-TiO2/rGO) nanocomposites were successfully prepared by sol–gel method. Characterization results showed F ions played an essential role in the formation of TiO2 nanoparticles. Between the fluorine sources selected, NH4F was more optimal than NaF doping on the grounds that the existence of Na+ ion was an inevitable factor for the production of brookite. F-TiO2/rGO nanocomposite obtained by adding 5%at NH4F significantly narrowed the bandgap energy from approximately 3.17 to 2.41 eV. Box–Behnken design was adopted to optimize the MB photo-degradation process by F(5%NH4F)-TiO2/rGO nanocomposites under different reaction conditions. Moreover, the antibacterial behaviour of this novel material was also investigated by Escherichia coli (E. coli) bacteria under visible light. The morphology changes of E. coli cells were directly observed by field emission scanning electron microscope and further confirmed that the excellent sterilization of F-TiO2/rGO nanocomposites resulted from the active species. The outstanding photocatalytic performance and antibacterial behaviour of F-TiO2/rGO nanocomposite was attributed to the synergistic effect of photocatalytic redox reaction and adsorption. These results indicated F(5%NH4F)-TiO2/rGO nanocomposite was a promising antibacterial photo-adsorbent for wastewater treatment improvement.

Express-Method for Determination of the Oxidizing Capacity of Activated Sludge and Its Biofilms in Pulp and Paper Mill

Microbial dehydrogenase activity can help to determine the oxidizing capacity of activated sludge. Here we propose an innovative and automated express-method based on rapid determination of dehydrogenase activity. The measurement is based on the rate of methylene blue reduction by living microbial cells in suspension. A single analysis takes 10 min. The method was adapted for biofilms immobilized on the floating carriers of industrial bioreactors and the kinetics of biological oxidation by activated sludge and biofilms was compared. New parameters were proposed to characterize the biological oxidation under low oxygen levels. The obtained make it possible to quickly determine the dehydrogenase activity of activated sludge and biofilms and promptly monitor the effectiveness of industrial biological wastewater treatment.

Cu–Ag Alloy Nanoparticles in Hydrogel Nanofibers for the Catalytic Reduction of Organic Compounds

Nanoalloys or alloy nanoparticles containing multiple metals are of great interest because the combination of multiple metals in close proximity can grant enhanced properties including stability, activity, and selectivity arising from synergism that cannot be accessed by the combination of individual metals. In this study, we have produced nanoalloys in stable flexible electrospun hydrogel nanofibers composed of poly(acrylic acid) and poly(allylamine hydrochloride). The hydrogel fibers were loaded with metal ions such as copper and silver through an immersion in metal salt solutions followed by a chemical reduction to form the metal nanoparticles. The hydrogel matrix allowed for the absorption of metal ions into the fibers and provided a viscous environment to promote the formation of alloy particles in the small diameter range (<25 nm). The proposed fabrication process is advantageous in terms of simplicity, controllability, and versatility. The reductions of 4-nitrophenol and methylene blue were performed to test and compare the catalytic activity of monometallic nanoparticles and copper–silver bimetallic nanoparticles. The copper–silver bimetallic nanoparticles demonstrated preferred selectivity for the reduction of 4-nitrophenol and higher catalytic activity for the reduction of methylene blue. Overall, we have developed promising stable flexible nanocomposites for catalytic reduction of organic redox compounds, and other catalytic nanoalloy systems could be further studied by modification of the procedure.

Single-Atom Ni Heterogeneous Catalysts Supported UiO-66 Structure: Synthesis and Catalytic Activities

Herein, the single-atom Ni site heterogeneous catalysts supported by the UiO-66 structure (University of Oslo-66 metal organic framework) were successfully synthesized by a postsynthetic metalation method, where Ni ions are covalently attached to the missing-linker defect sites at zirconium oxide clusters (Zr6O4(OH)4) in as-prepared UiO-66 structure, [Zr6O4(OH)4(BDC)(DMF)10(OH)10] (BDC (benzene-1,4-dicarboxylate), DMF (dimethylformamide)). The structure properties of the catalysts were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption isotherms (BET), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). It was found that single-atom Ni heterogeneous catalysts supported by the UiO-66 structure, UiO-66/Ni1.0 [Zr6O4(OH)4(C8H4O4)(DMF)10(OH)8Ni2(OH)2(Cl)2], showed a sphere-like morphology with a high specific surface area as well as good thermal stability. Specifically, the as-prepared UiO-66/Ni1.0 exhibited the excellent catalytic activity and stability for 4-nitrophenol reduction in terms of low activation energy ( E a = 23.15 kJ mo l − 1 ), high turnover frequency (76.19 molecules g-1 min-1), and high apparent rate constant ( k app = 0.956 mi n − 1 ). In addition, methylene blue (MB) was also chosen as the organic dye model for catalytic reduction reaction. The k app and TOF for the reduction of MB using UiO-66/Ni1.0 were 0.787 min−1 and 33.89 × 10 20 molecules g−1 min−1, respectively.

Fabrication and characterization of amidoxime-functionalized silica decorated with copper: a catalytic assembly for rapid reduction of dyes.

In this study, amidoxime-functionalized silica decorated with copper (AFS-Cu) was fabricated and tested for its catalytic application. Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were employed to characterize its structure and morphology. The application of AFS-Cu as a catalyst for the catalytic reduction of methylene blue (MB) in aqueous media using NaBH4 as reductant was evaluated. The ability to reuse as well as the effect of catalyst dose and pH of solution on the catalytic activity was investigated. The reduction of MB followed pseudo-first-order kinetics and the rate constant (k) was 0.6224 min-1. AFS-Cu was found to be a highly effective catalyst for MB reduction reaction and can be easily recovered and reused several times with no appreciable loss of catalytic activity.

Oligonucleotide-Based Reusable Electrochemical Silver(I) Sensor and Its Optimization via Probe Packing Density.

We report herein a selective, sensitive, and reusable electrochemical sensor for the detection of silver(I) ions. This sensor detects Ag+ through a structure-switching electrode-bound DNA by measuring the changes in the electron-transfer efficiency. A single-stranded DNA, featuring a methylene blue (MB)-tagged DNA hairpin structure, strategically provides selective binding for the silver-mediated coordination of cytosine–Ag+–cytosine complexes. The DNA-modified electrode produces a change in the electrochemical signal due to the redox current of the surface-confined MB tag. The “turn-on” signaling upon silver(I) ion binding could be attributed to a conformational change in the MB-tagged DNA from an open structure to a target-induced folding structure. Differential pulse voltammetry of the DNA-modified electrode showed that the MB reduction signal increased linearly with an increase in Ag+ concentrations in a range of 10–200 nM, with a detection limit of 10 nM. The structure-switching silver(I) ion sensor was amenable to regeneration by simply unfolding the electrode-bound MB-tagged DNA in 100 mM ethylenediaminetetraacetic acid, and it could be regenerated with no loss in signal gain upon subsequent silver(I) ion binding. We also demonstrated that by controlling the probe packing density on the electrode surface, the fabrication parameters can be varied to achieve optimal sensor performance.

Exploiting the Catalytic Ability of Polydopamine-Remodeling Gold Nanoparticles toward the Naked-Eye Detection of Cancer Cells at a Single-Cell Level

In this study, a catalytic polydopamine-remodeling gold nanoparticle sensitized with an antinucleolin AS1411 probe (pAu nanoprobe) is synthesized, where the surface of the gold nanoparticles (AuNPs) is modified with a spontaneous self-polymerization of a polydopamine coating that imparts the probe functionalization ability and antispecific protein binding while the intrinsic catalytic property of the AuNPs is preserved. The functionalized AS1411 probe exerts specific recognition with nucleolin protein that is found to be overexpressed on the surface of breast cancer cells (MDA-MB-231). Scanning electron microscopy (SEM) confirms that the specific binding of the pAu nanoprobe occurs at the cancer cell surface. Taking advantage of the catalytic ability of the pAu nanoprobe in reducing blue-colored methylene blue (MB) to colorless leuco-MB, a colorimetric biosensing platform is established based on the accessible catalytic active sites on the pAu nanoprobe toward MB. The specific binding inhibits the pAu nanoprobe from efficiently catalyzing the reduction of MB, resulting in a "turn-off" catalytic biosensing platform. The catalytic conversion of MB is inversely proportional to the concentration of the nucleolin protein and the cancer cells, yielding a detection limit of 15 pM of the nucleolin protein and two cancer cells. The presence of five orders of magnitude higher concentration of bovine serum albumin hardly affects the catalytic ability of the pAu nanoprobe, that is, 88% catalytic ability is still preserved, which validates the specificity of the proposed pAu nanoprobe. In particular, a distinct color contrast creates a significant signal-to-noise ratio so as to enable single-cell level detection of two cancer cells by naked-eye judgment. Moreover, the undiluted, real human serum samples spiked with the cancer cells were examined with an impressive recovery of 94 ± 0.3%, which holds great promise in cancer cell screening.

Bacteriological quality of raw milk marketed in and around Guwahati city, Assam, India.

Background and Aim:Milk is a highly perishable commodity, which is subjected to various types of contamination right from the farm level to the consumers’ table. This study aimed to assess the quality of raw milk sold in and around Guwahati city based on the microbial load.Materials and Methods:A total of 200 raw pooled milk samples collected from 25 different locations in and around Guwahati city were subjected to quality evaluation based on the methylene blue reduction test (MBRT), standard plate count, and coliform count as per the standard procedure.Results:Out of the 200 samples evaluated, more than 50% of them were graded as poor to very poor quality based on the MBRT results. None of the samples could be graded as excellent quality and only 14.5% were graded as good quality. The standard plate count and coliform count of all the raw milk samples were found to be significantly higher than the legal standard. A highly significant (p<0.01) difference was observed for standard plate count and coliform count among the different locations in and around Guwahati city.Conclusion:From the present study, it could be inferred that raw milk sold in most parts of Guwahati city do not confer to the legal microbiological standard and may pose a high risk of milk-borne illness among consumers of the city, which needs a systematic series of actions to be implemented properly.

Towards mass production of a spherical montmorillonite@covalent organic framework@gold nanoparticles heterostructure as a high-efficiency catalyst for reduction of methylene blue

Gold nanoparticles (Au NPs) supported by a covalent organic framework (COF) exhibited a remarkably catalytic performance towards organic pollutants, while the application is limited by the recovery and reuse from the mixture due to the size of Au NPs@COF at the nanoscale. Herein, Au NPs were in situ reduced on the surface of sulfhydryl groups functionalized new COF with NaBH4, followed by the deposition on polydopamine modified micron-sized porous spherical montmorillonite (SMt) to construct a spherical SMt@COF@Au NPs heterostructure. SMt was used here due to its excellent adsorption ability towards methylene blue (MB), increasing the concentration of MB near COF@Au NPs, thus accelerating the catalytic reaction. Hence, the optimized apparent reduction rate constant (Kapp) and turnover frequency (TOF) in our experiment could reach 8.32 min−1 and 3.2 × 105 h−1, respectively, at 40 °C and pH values of 10, which is much better than the reported. Furthermore, micro-sized SMt with self-sedimentary property could be easily recovered from the mixture without any devices involved. More importantly, the granular micro-sized morphology of the SMt-based heterostructure could facile transport on the product line and reduce the fouling, facilitating mass production COF@Au NPs based catalyst for application.

Potential of Scenedesmus-fabricated ZnO nanorods in photocatalytic reduction of methylene blue under direct sunlight: kinetics and mechanism.

Organic synthetic dyes are widely used in several industries; however, their inherent resistance to biodegradation necessitates to investigate alternative methods for the remediation of this class of hazardous substances. In the present study, a green synthesis of ZnO nanorods was achieved in a fast, environment-friendly, and safe microwave process employing algal extract. Different metabolites like sugars, proteins, fatty acids, amino acids, and vitamins present in the algal extract reduced the Zn2+ into ZnO. The XRD analysis showed that the nanostructure was a crystalline hexagonal nanorod having a crystalline size of 27.37 nm. The XPS spectra of ZnO nanorod showed characteristic peaks at binding energy 1043, 1020, 496, 137, 87, and 8 eV corresponding to Zn2p1/2, Zn2p3/2, ZnLMM, Zn3s, Zn3p, Zn3d, respectively. The synthesized ZnO nanorods were in-situ functionalized and showed strong catalytic activity in photoreduction of a model organic dye methylene blue (MB) under direct sunlight irradiation. Synthesized ZnO nanorods showed a complete (100%) reduction of model dye MB from its 10 mg/L aqueous solution. The photocatalytic degradation of MB followed the Michaelis-Menten kinetics. The rate of ZnO-catalyzed photocatalytic degradation depends on the concentrations of ZnO, pH, and sunlight irradiation. The ZnO nanorod-catalyzed photoreduction of MB involves hydroxyl radicals. Algal-mediated and microwave-assisted synthesis provides a scalable source of metal oxide nanoparticles for the remediation of dye-containing wastewaters under natural sunlight. Apart from application in the removal of dyes, ZnO nanorods are excellent material for applications in semiconductors, electronics, optics, bio-imaging, and drug delivery.

Magnetite-Silica core-shell nanocomposites decorated with silver nanoparticles for enhanced catalytic reduction of 4-nitrophenol and degradation of methylene blue dye in the water

In this study, we synthesized multifunctional Fe3O4@SiO2/Ag magnetic nanocomposites (MNCs) by in situ method with an average size of 583 ± 4 nm. At different temperatures and pH, the catalytic properties of as-prepared MNCs were investigated for the degradation of methylene blue (MB) dye and reduction of 4-nitrophenol (4-NP) in an aqueous solution. The Fe3O4@SiO2/Ag MNCs were capable to remove 96.5% and 97% of MB and 4-NP respectively from aqueous media. The as-prepared MNCs were characterized by using Transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering analysis (DLS), Energy dispersive X-rays analysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible diffuse reflectance spectra (UV–vis DRS) and vibrating sample magnetometery (VSM). The rate constant for 4-NP and MB were calculated which were 0.385 ± 0.002 and 1.58 ± 0.09 min−1 respectively. The values of thermodynamics parameters enthalpy, Gibbs free energy, Entropy and activation energy were calculated for both MB and 4-NP. This nanocomposite exhibited easy synthesis, cost effective, high stability and fast separation using external magnet.

COMPOSITION AND QUALITY OF FRESH COW MILK OFFERED FOR SALE IN PARTS OF PLATEAU STATE OF NIGERIA.

The gross composition and quality of fresh cow milk purchased from Fulani milk vendors in three locations of Plateau State were investigated. Milk quality was assessed by the methylene blue reduction test while bacterial contamination was by the agar plate count and the direct microscopic count. The mean contents of total solids, butterfat, protein and ash of a total of 100 samples from Barkin Ladi, Jos and Bukuru markets were 12.45, 4.77, 3.90, 0.92; 12.85, 4.50, 3.68, 0.93; and 12.41, 5.26, 3.72, 0.91% respectively. The proximate constituents did not differ significantly between locations. The methylene blue test indicated that only 23.5% of the sample were of good quality while 41.2 and 35.3% were rated fair and poor respectively. No sample merited excellent rating. The agar plate count showed a range of 1.97 x 106 for Bukuru to 2.54 x 106 cells/ml for Jos market. The direct microscopic count showed the highest mean bacteria value for Barkin Ladi samples. The high bacterial counts as observed were probably indicative of poor milking hygiene and handling. It is suggested that such milk should be properly pasteurized before consumption and delivered/marketed early at source to reduce the time for microbial multiplication.

Using palladium nanoparticle-decorated lysozyme amyloid fibrils to catalyze the reduction of methylene blue

Amyloid fibrils’ stable structure and nice biocompatibility make them good candidates as the templates used in engineering and biomedicine. While palladium nanoparticles have been widely used as catalysts, their high surface energy results in aggregation of nanoparticles, leading to decreased catalytic activities. Here, we investigated the catalytic performance of palladium nanoparticles-deposited lysozyme amyloid fibrils through the reduction of methylene blue (MB). The palladium nanoparticles-decorated lysozyme fibrils were first synthesized and then characterized using several analytical tools. The progress of reductive MB degradation in the presence of sodium borohydride was monitored via UV–Vis spectrophotometry to investigate the catalytic efficiency of bare palladium nanoparticles and palladium nanoparticle/lysozyme fibril hybrids under different conditions. The kinetic data were analyzed using a pseudo-first order model. Finally, the magnitudes of apparent rate constants under different conditions and associated activation parameters were determined. We found that the level of nanoparticle aggregation decreased and the degree of MB conversion significantly increased upon incorporation of amyloid fibrils as the supporting carriers. Moreover, a lower activation energy was perceived when MB reduction was catalyzed by the palladium nanoparticle/fibril hybrids as compared with the bare nanoparticle counterpart. This study presents a nice example of applying amyloid fibril-based hybrid materials in one of the important engineering fields - catalysis.

Hydrothermal preparation of Ag/Fe3O4/Cellulose nanocrystals nanocomposite and its application in methylene blue removal

The preparation of reusable and eco-friendly materials from renewable biomass resources such as cellulose is an inevitable choice for the sustainable development. In this paper, Ag/Fe3O4/cellulose nanocrystals (CNC) nanocomposite was prepared and investigated its application in methylene blue (MB) removal. In the procedure, CNC was isolated from Vietnamese coconut husk fibers (CCH) biomass via a formic/peroxyformic acid process treatment and hydrochloric acid hydrolysis. The obtained CNC was used as a starting material to prepare Ag/Fe3O4 nanostructure by facile and green hydrothermal method. The nanocomposite was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and magnetic properties via vibrating sample magnetometer (VSM) analysis. The results showed that Ag/Fe3O4 was formed with a particle structure and dispersed on the CNC surface. All samples exhibited magnetic properties and the saturation magnetization (Ms) of Ag/Fe3O4 composite was reduced from 48 to 12 emu/g with adding CNC. Ag/Fe3O4/CNC magnetic nanocomposite demonstrated good adsorption of MB solution and exhibited a fast catalytic reduction of MB after immersion treatment by NaBH4, which showed potential applications in water treatment.