Chemical Reduction Agents Research Articles

Biosynthesis of silver nanoparticles on yellow phosphorus slag and its application in organic coatings

Abstract This work concentrated on the decoration of AgNPs to yellow phosphorus slag (YPS) using both chemical (NaBH4) and biological (Areca catechu nut and Jasminum subtriplinerve leaf extracts) reducing agents, as well as its use as antibacterial and enhancement additives for organic coatings based on acrylic emulsion resin. It is the first study about the decoration of AgNPs on the surface of YPS using bio-reduction agents (A. catechu nut and J. subtriplinerve leaf extracts). The characteristics of YPS decorated by AgNPs (YPS@AgNPs) were determined using attenuated total reflectance infrared spectroscopy, scanning electron microscopy, X-ray diffraction, ultraviolet-visible spectroscopy and dynamic light scattering methods. To quantify the amount of AgNPs in YPS@AgNPs, atomic absorption spectroscopy was used. The results of YPS@AgNPs fabrication confirmed that the above green reduction agents had a higher efficiency and were more suitable than the chemical reduction agent (NaBH4). Moreover, the ability to inhibit the growth of bacteria strains of YPS@AgNPs using the J. subtriplinerve leaf extract as a reducing agent gave the best result among the three agents. In particular, the bactericidal activity of YPS@AgNPs against the new marine bacterium, Pseudomonas stutzeri B27, was evaluated, and it was found that YPS@AgNPs can inhibit the growth of an antibiotic-resistant bacterium, P. stutzeri B27. They enhance not only the mechanical properties but also the bactericidal ability of the water-borne acrylic resin coating.

Study of the effect of chemical reduction agent on the synthesis and structural properties of WO3-TeO2 and MoO3-TeO2 two-dimensional compounds.

Study of the effect of chemical reduction agent on the synthesis and structural properties of WO3-TeO2 and MoO3-TeO2 two-dimensional compounds.

Synthesis and characterization of novel compounds and determining their antifungal properties against rainbow trout pathogen, Saprolegnia sp. in vitro

Saprolegnia growth on trout eggs is a problem frequently encountered in fish hatcheries worldwide. In the present study silver nanoparticles (Ag NPs) were effectively grafted on the zeolite and bentonite framework using the chemical reduction method. Zeolite and bentonite, silver nitrate (AgNO3), and sodium borohydride (NaBH4) were used as inorganic solid supports, a silver precursor, and a chemical reduction agent, respectively. Silver ions were introduced into the porous zeolite through an ion-exchange path, in the external and interlamellar space of bentonite at room temperature. AgNO3 and NaBH4 were used as a silver precursor and reducing agent, respectively. The Ag/zeolite and Ag/bentonite nano compounds were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared (FTIR), X-ray powder diffraction (XRD), Energy-dispersive X-Ray spectroscopy (EDX) analysis. The results showed that Ag NPs form a spherical shape with uniform homogeneity in the particle size. The antifungal activity of Ag NPs in zeolites and bentonite were investigated against Saprolegnia sp. with different loads of nano composites and exposure time. All Ag/zeolite NCs and Ag/bentonite NCs were found to have antifungal activities. These results revealed that Ag NPs could be used as effective growth inhibitors in different biological systems, for instance in aquatic animal hatchery facilities.

Preparation and characterization of antifungal colloidal copper nanoparticles and their antifungal activity against Fusarium oxysporum and Phytophthora capsici

Copper nanoparticles (CuNPs) possess a promising antibacterial and antifungal activity with low-cost reagent and fabrication. In this study, we report the antifungal activity of pure CuNPs against Fusarium oxysporum (F. oxysporum) and Phytophthora capsici (P. capsici). CuNPs were prepared by reducing Cu2+ from copper(II) chloride dihydrate via a green chemical reduction agent using ascorbic acid as both reducing agent and antioxidant agent in aqueous media and polyvinylpyrrolidone as a stabilizer. The effect of the solution pH, reduction time, ascorbic-acid-to-Cu2+ molar ratio, role of stabilizing agent polyvinylpyrrolidone to particle size of CuNPs were studied. The antifungal activity of CuNPs at different concentrations and different particle sizes against two plant pathogenic fungi F. oxysporum and P. capsici has been tested by the agar disc diffusion technique. Characterizations were carried out by X-ray diffraction measurements, transmission electron microscopy, and ultraviolet–visible light, which revealed that the CuNPs obtained at different synthesis conditions have different particles size, resulting in different antifungal activities. The synthesized CuNPs demonstrated significant antifungal activity against F. oxysporum and P. capsici. F. oxysporum and P. capsici were entirely inhibited at the concentration of CuNPs of 30 ppm after 3 days of incubation and 7.5 ppm after 1 day of incubation, respectively. Our results suggest that synthesized CuNPs can be used as a novel antifungal agent in agriculture to control the plant pathogenic fungi of F. oxysporum and P. capsici.

Assessment of photocatalytic performance of Fe/N-TiO2 photocatalysts prepared by liquid phase plasma process

Abstract To improve the photocatalytic performance of TiO2 photocatalysts, a new method, liquid phase plasma (LPP) method, was used to introduce nitrogen and iron oxide. Interstitial or substitutional nitrogen and Fe3+ iron nanoparticles were impregnated on the surface of TiO2 by LPP reaction without additional chemical reduction agent and the amount of iron of modified TiO2 photocatalysts was affected by the amount of initial precursor. The adsorption edge of modified TiO2 photocatalysts was shifted to the visible region in proportion to the amount of nitrogen and iron oxide, and the band gap energy was decreased, and the photocatalytic activity was confirmed by PL and EPR analysis. The photocatalytic activities of modified TiO2 photocatalysts were measured under UV and blue LED lamps and compared with pure TiO2 powder (P-25). The modified TiO2 exhibited better photocatalytic degradation performance than pure TiO2 under blue LED light conditions, but exhibited low degradation activity under UV LED light conditions. Through GC–MS analysis, it was found that the methylene blue was finally decomposed into an inorganic substance through intermediates such as benzene sulfonic acid and phenol by OH radicals. From these results, we found that the modified TiO2 photocatalysts can be easily prepared using the LPP method and can be used in the visible region.

Disulfide linkage assignment based on reducing electrochemistry and mass spectrometry using a lead electrode

The study of disulfide linkage is a crucial part of the quality assessment of biopharmaceutical products because disulfide bonds stabilize the tertiary structure of proteins and maintain protein functions. Therefore, a suitable method is highly required for disulfide linkage assignment when nested disulfide bonds formed with closely spaced cysteine residues. A novel approach for disulfide linkage assignment of disulfide-rich peptides and proteins via electrochemical reduction on a lead electrode with mass spectrometry is presented in this paper. The method features partial electrochemical reduction and alkylation of peptides followed by alkylated peptide sequencing based on tandem mass spectrometry. Lead was chosen for the first time as an electrode material for disulfide bond reduction, because it has the advantages of maintenance free (only infrequent polishing needed), easy operation in DC mode, and reusability. Without any special sample preparation and any chemical reduction agents, disulfide bond in peptides can be cleaved rapidly. The new method was successfully tested with two peptides and one protein containing nested disulfide bonds.

Modulating amyloid fibrillation in a minimalist model peptide by intermolecular disulfide chemical reduction.

Peptide structural transformation and aggregation is associated with a large number of outsider aetiology diseases, and it is intrinsically linked to amyloid peptide aggregation. Diphenylalanine self-assembled structures are used as robust minimalist beta amyloids not only to elucidate protein aggregation but also to generate hydrogels. Herein, we employed a neutral model peptide Ac-Phe-Phe-Cys-NH2 (Ac-FFC-NH2) to elucidate the role of intermolecular disulfide bonds in protein fibrillation. The Ac-FFC-NH2 peptide initially self-assembles into nanospheres that evolve to amyloid type fibrils under mild oxidative conditions. Incubation of the peptide in the presence of the chemical reduction agent TCEP inhibits the formation of the fibrils, detecting only spherical nanostructures with no secondary structure. Importantly, we triggered the transformation of the preformed linear straight amyloid fibrils to non-fibrillar structures by TCEP treatment. Under this condition, the amyloid bundles are transformed into rings, which evolve to a new spherical microstructure. We showed that the chemical reduction of intermolecular S-S in internal amyloid sequences might favour the off-path intermediates of amyloid fibril growth, even when the fibrils are formed. Our findings demonstrated that in internal amyloid sequences, the formation of intermolecular S-S promotes the formation of amyloid type fibrils; meanwhile, its reduction stabilises non-fibrillar structures. Altogether, this work provides fundamental understanding at the molecular and supramolecular level, thus facilitating the rational design of therapeutic tools for protein aggregation diseases.

Structural characterization of octreotide impurities by on-line electrochemistry-tandem mass spectrometry

Octreotide, an octapeptide derivative of natural somatostatin, is widely used in the treatment of the secretion of gastrointestinal cancers, pituitary tumors, and acromegaly. To prolong the drug release, octreotide is extensively encapsulated with poly (D, L-lactic-co-glycolic acid) (PLGA) microspheres. While peptide impurities may be generated during fabrication of peptide-loaded microspheres and drug delivery processes, making the identification of peptide impurities a challenging task. For structural characterization of octreotide impurities, a new method based on mass spectrometry coupled with electrochemistry (EC-MS) was developed in this study. An electrospray ionization source with a grounded needle design was chosen as the coupling interface between electrochemistry and mass spectrometry, which simplifies instrument configuration and thus operation. Without any special sample preparation and any chemical reduction agents, disulfide bond in peptides was cleaved rapidly. The de novo sequencing octreotide and three acylated octreotides were easily obtained with followed tandem mass spectrometry. The results demonstrate that this method is suitable for fast evaluation and characterization of peptide containing disulfide bonds.

Effect of the GO Reduction Method on the Dielectric Properties, Electrical Conductivity and Crystalline Behavior of PEO/rGO Nanocomposites.

The effect of the reduction method to prepare reduced graphene oxide (rGO) on the melt linear viscoelastic properties, electrical conductivity, polymer matrix crystalline behavior and dielectric properties of PEO-rGO nanocomposites was investigated. Reduction was performed chemically with either sodium borohydride (NaBH4) or hydrazine monohydrate (N2H4·H2O) or both reduction agents consecutively as well as thermally at 1000 °C. The different reduction methods resulted in exfoliated rGO sheets with different types and amounts of remaining functional groups, as indicated by FT-IR, Raman, TGA and XRD characterization. Moreover, their electrical conductivity ranged between 10−4 and 10−1 S/cm, with the consecutive use of both chemical reduction agents being far superior. PEO nanocomposites with filler loadings of 0.5 wt %, 1 wt % and 2 wt % were prepared by solvent mixing. The rGO fillers affected the melt linear viscoelastic and crystalline behavior of the PEO matrix and resulted in nanocomposites with a substantially increased electrical conductivity. Despite the wide variability in filler conductivity, the effects on the polymer nanocomposite properties were less distinctive. A correlation was obtained between the reduction of the mobility of the polymer chains (evaluated by the glass transition temperature) and the dielectric strength of the interfacial polarisation originating from the effective entrapment of GO/rGO filler charges at the interface with the less conductive PEO. Thus, favorable interactions of the polar PEO with the filler led to reduced mobility of the PEO chains and thereby a more effective entrapment of the filler charges at the PEO interface.

The Effect of Silver Nanoparticles Size, Produced Using Plant Extract from Arbutus unedo, on Their Antibacterial Efficacy.

Silver nanoparticles (AgNPs) have been demonstrated to restrain bacterial growth, while maintaining minimal risk in development of bacterial resistance and human cell toxicity that conventional silver compounds exhibit. Several physical and chemical methods have been reported to synthesize AgNPs. However, these methods are expensive and involve heavy chemical reduction agents. An alternative approach to produce AgNPs in a cost-effective and environmentally friendly way employs a biological pathway using various plant extracts to reduce metal ions. The size control issue, and the stability of nanoparticles, remain some of the latest challenges in such methods. In this study, we used two different concentrations of fresh leaf extract of the plant Arbutus unedo (LEA) as a reducing and stabilizing agent to produce two size variations of AgNPs. UV-Vis spectroscopy, Dynamic Light Scattering, Transmission Electron Microscopy, and zeta potential were applied for the characterization of AgNPs. Both AgNP variations were evaluated for their antibacterial efficacy against the gram-negative species Escherichia coli and Pseudomonas aeruginosa, as well as the gram-positive species Bacillus subtilis and Staphylococcus epidermidis. Although significant differences have been achieved in the nanoparticles’ size by varying the plant extract concentration during synthesis, the antibacterial effect was almost the same.

Reduced Graphene Oxide Paper: Fabrication by a Green Thermal Reduction Method and Preliminary Study of its <i>In Vitro</i> Cytotoxicity

Graphene films have been intensively explored because of their unique mechanical and physicochemical properties for potential applications in field of tissue engineering and implants. However, for biomedical applications, it is necessary to fully understand the toxicity and biocompatibility of the prepared graphene films since different synthesis method might lead to different biological properties. Here we report a step-by-step thermal reduction method of preparing reduced graphene oxide (rGO) film directly on various substrates at low heating temperature (below about 200 °C) without requiring any chemical reduction agent like hydrazine or other reductants (therefore we call it green method). Slowly heating GO hydrosol that was coated on the surface of a glass cell-culture dish or inside of a polypropylene tube from room temperature to 60, 100, and 160 °C for 12 h, respectively, a shiny and flat surface without crumpled structure or tiny pores was formed. We peeled it off from the substrate to explore its cytotoxicity. The results exhibited that the rGO film was biocompatible with Cal-72 cell but against Escherichia coli bacteria. Our work confirmed that rGO film produced by the green reduction method is cytocompatible with mammalian cells, which makes this rGO film a promising material for tissue engineering scaffold or as a surface-modification coating of an implant.

МЕТИЛОВИЙ ЕСТЕР {1-[2-(4-НІТРОФЕНІЛ)-2-ЦІАНОВІНІЛ]ФЕНОКСИ}ОЦТОВОЇ КИСЛОТИ В РЕАКЦІЯХ ВІДНОВЛЕННЯ

3-(Het)aryl-3-(2-alkoxyphenyl)acrylonitriles are very practical polyfunctional molecules for organic synthesis; in particular difficult objects with near placed active groups can be easy obtained by the reduction of 3-(het)aryl-3-(2-alkoxyphenyl)acrylonitriles fragments. But now only reduction of activated C=C bond in such molecules mostly investigated. Previously it was shown by us that the action of sodium borohydride on esters of {2-[2-cyano-2-(4-nitrophenyl)vinyl]phenoxy}acetic acid caused not only saturation of C=C bond but also reduction of ester group to alcohol. So the results of reduction of 3-(het)aryl-3-(2-alkoxyphenyl)acrylonitriles can be more interest when other electrophilic fragment presents in molecule. And the aim of current work is the investigation of methyl ester of {2-[2-cyano-2-(4-nitrophenyl)vinyl]phenoxy}acetic acid behaviour in different reductive medium. Because of the very high electrophylity of observed molecule it's unfeasible to obtain good result in reactions with strong nucleophyles or with chemical reduction agents; that's why the hydrogenation in mild condition was used on the first step. It was found that the nitro group and the activated C=C bond were reducted simultaneously by H2 at 1.2 atm presure and room temperature with Pd/C catalizing; so methyl ester of {2-[2-(4-aminophenyl)-2-cyanoethyl]phenoxy}acetic acid was formed. Further hydrogenation took place on higher H2 presure (80 atm); and as a result of the saturation of C≡N bond methyl ester of {2-[3-amino-2-(4-aminophenyl)propyl]phenoxy}acetic acid creation occurred. The last compound can be transformed into 2-{2-[3-amino-2-(4-aminophenyl)propyl]phenoxy}ethanol by the LiAlH4 action. Such interesting structure also can be synthetized through the reduction of 3-[2-(2-hydroxyethoxy)phenyl]-2-(4-nitrophenyl)propionitrile that was obtained earlier: in the first step hydrogenation (1.2 atm H2) produced 3-[2-(2-hydroxyethoxy)phenyl]-2-(4-aminophenyl)propionitrile which nitrile group was reducted by LiAlH4 in the second step.

An attempt towards fabricating reduced graphene oxide composites with traditional polymer processing techniques by adding chemical reduction agents

Graphene based polymer composites have attracted considerable attention for both fundamental studies and practical applications. Fabricating polymer/reduced graphene oxide (rGO) composites via a readily mass-producible and environment-friendly technique is imperative for industry production. In this work, we tried to add various kinds of chemical reductants as “modifier” and study the possibility of in situ chemical reduction of graphene oxide (GO) during traditional thermoplastic processing of polymer and GO mixture. The thermal analysis and structural characterization revealed that among the 4 kinds reductants we investigated, hydroquinone (HQ) can effectively reduce GO during the commonly used melt-blending or twin-roller miller mixing processing. For an ethylene vinyl acetate copolymer (EVA) composite prepared by melt-blending of EVA and GO (95:5 in mass) at 100 °C, the heat of reduction corresponds to the remove of oxygen-containing groups on GO in the composite is 50.6 J/g. In contrast, the value for the composite with 5 wt% HQ is only 1.6 J/g. The significant decreased values of reduction heat suggested the effective reduction of GO due to the addition of HQ. Although the reducing ability of HQ is weak relatively, our work confirms that it is possible to chemically reduce GO during traditional processing of polymer materials, which is helpful to develop a large-scale producible, cost-effective and environment-friendly approach for the fabrication of polymer/rGO composites.

Preparation by sonophotodeposition method of bimetallic photocatalysts Pd–Cu/TiO2 for sustainable gaseous selective oxidation of methanol to methyl formate

It has been demonstrated that sonophotodeposition can be one choice as a green method to synthesize bimetallic supported photocatalysts with enhanced performance for selective oxidations. A series of Pd–Cu supported on Titania-P90 photocatalysts were successfully prepared using this innovative method of effective synergistic combination of sonication and light. In addition, our method does not require the use of strong chemical reduction agent and it is executed in a short time, room temperature and atmospheric pressure. The prepared materials were characterized by a number of techniques such as High-Resolution Transmission Electron Microscopy (HRTEM), DR UV–vis spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and powder X-ray diffraction (XRD). Additionally, better bimetallic systems were obtained (methanol conversion >50% and selectivity to methyl formate >80%) by SonoPhotoDeposition (SPD) than in the case of the conventional photodeposition methodology. It has been discussed the possible reasons of the observed slight deactivation (8% after 2h reaction test) of the best performing material in gas phase methanol selective photo-oxidation.

Three-dimensional patterning of solid microstructures through laser reduction of colloidal graphene oxide in liquid-crystalline dispersions.

Graphene materials and structures have become an essential part of modern electronics and photovoltaics. However, despite many production methods, applications of graphene-based structures are hindered by high costs, lack of scalability and limitations in spatial patterning. Here we fabricate three-dimensional functional solid microstructures of reduced graphene oxide in a lyotropic nematic liquid crystal of graphene oxide flakes using a pulsed near-infrared laser. This reliable, scalable approach is mask-free, does not require special chemical reduction agents, and can be implemented at ambient conditions starting from aqueous graphene oxide flakes. Orientational ordering of graphene oxide flakes in self-assembled liquid-crystalline phases enables laser patterning of complex, three-dimensional reduced graphene oxide structures and colloidal particles, such as trefoil knots, with 'frozen' orientational order of flakes. These structures and particles are mechanically rigid and range from hundreds of nanometres to millimetres in size, as needed for applications in colloids, electronics, photonics and display technology.

Size control of copper nanoparticle by electron beam irradiation

Mono-dispersed copper nanoparticles with various sizes are prepared to control the electron beam energy, beam currents, and absorbed doses. This method is a simple, quick, single step, and green process because no chemical reduction agent is used and no by product is produced. The copper particles were observed by transmission electron microscopy (TEM), UV-vis spectrometer, and energy dispersive spectrometer (EDS). Copper nanoparticles have unique properties with a surface plasmon resonance effect. The size of the nanoparticles can influence their optical properties. The positions of plasmon absorption in these copper nanoparticles can be various owing to the different sizes. It has been recognized that the plasmon position of copper nanoparticles is shifted to a long wavelength according to the increased size. The size control of the copper particles can be achieved by adjusting the electron beam irradiation conditions.

In situ synthesis of palladium nanoparticles on multi-walled carbon nanotubes and their electroactivity for ethanol oxidation

Pd nanoparticles (Pd-NPs) were prepared and directly anchored on the surface of multi-walled carbon nanotubes (MWCNTs) in the absence of chemical reduction agent, where MWCNTs were used as both the chemical reduction agent and the support substrate of Pd-NPs. Effect of various surfactants on the in situ deposition of Pd-NPs on MWCNTs was investigated. When MWCNTs were modified with a cationic surfactant (hexadecyl trimethyl ammonium bromide, CTAB), the amount of the Pd-NPs (Pd-NP/CTAB-MWCNT) generated by such an in situ deposition method gets a notable increase, and the size of the as-synthesized Pd-NPs becomes smaller, compared with those in the absence of any surfactant (Pd-NP/MWCNT) or in the presence of an anionic surfactant SDS (Pd-NP/SDS-MWCNT) and a neutral surfactant OP (Pd-NP/OP-MWCNT). Results show that the MWCNTs modified with CTAB are propitious to the in situ reduction of Pd2+. Among the prepared catalysts, Pd-NP/CTAB-MWCNT displays the highest electroactivity for ethanol oxidation in alkaline media.

Spectroscopy Study of Silver Nanoparticles Produced by Chemical Reduction

In this study, Ag nanoparticles were synthesized using two chemical reduction agents; ethylene glycol and sodium borohydride. Different particle size distributions were obtained and characterized by transmission electron microscopy. Ag nanoparticles concentrations of 1, 2 and 4 parts per million (gmL-1) were prepared and studied by ultraviolet-visible spectroscopy (UV-Vis) and atomic absorption spectrophotometry (AAS). In the UV-Vis results a characteristic band at 420 nm were observed. However, when the concentration of silver decreased, a change in band intensity was detected. Atomic absorption spectrophotometry measurements from different solutions of Ag nanoparticles showed a linear behavior similar to the silver standard solution in the concentration range 1 to 4 mgL-1. However, up 4 mgL-1 concentrations, the slope of the calibration curve is increases when the concentration of Ag nanoparticles is increased too.

Implementation of a biotechnological process for vat dyeing with woad

The traditional process for vat dyeing with woad (Isatis tinctoria L.) basically relies on microbial reduction of indigo to its soluble form, leucoindigo, through a complex fermentative process. In the 19th century, cultivation of woad went into decline and use of synthetic indigo dye and chemical reduction agents was established, with a consequent negative impact on the environment due to the release of polluting wastewaters by the synthetic dyeing industry. Recently, the ever-growing demand for environmentally friendly dyeing technologies has led to renewed interest in ecological textile traditions. In this context, this study aims at developing an environmentally friendly biotechnological process for vat dyeing with woad to replace use of polluting chemical reduction agents. Two simple broth media, containing yeast extract or corn steep liquor (CSL), were comparatively evaluated for their capacity to sustain the growth and reducing activity of the strain Clostridium isatidis DSM 15098(T). Subsequently, the dyeing capacity of the CSL medium added with 140 g L⁻¹ of woad powder, providing 2.4 g L⁻¹ of indigo dye, was evaluated after fermentation in laboratory bioreactors under anaerobic or microaerophilic conditions. In all fermentations, a sufficiently negative oxidation/reduction potential for reduction of indigo was reached as early as 24 h and maintained up to the end of the monitoring period. However, clearly faster indigo dye reduction was seen in the broth cultures fermented under strict anaerobiosis, thus suggesting the suitability of the N₂ flushing strategy for enhancement of bacterial-driven indigo reduction.

Unidirectional Redox‐Stimulated Movement around a CC Single Bond

A remarkable challenge for the design of molecular machines is the realization of a synchronized and unidirectional movement caused by an external stimulus. Such a movement can be achieved by a unidirectionally controlled change of the conformation or the configuration. Biphenol derivatives are one possibility to realize a redox-driven unidirectional molecular switch. For this reason, a 4,4'-biphenol derivative was fixed to a chiral cyclopeptidic scaffold and stimulated by chemical oxidants and reduction agents. The conformation of the switch was determined by DFT calculations by using B3LYP and the 6-31G* basis set. The switching process was observed by UV and circular dichroism (CD) spectroscopic measurements. Several oxidation agents and various conditions were tested, among which (diacetoxy)iodobenzene (DAIB) in methanol proved to be the best. In this way it was possible to synthesize a redox-stimulated molecular switch with a movement that is part of a rotation around a biaryl binding axis.