Cryochemical synthesis and antibacterial activity of hybrid nanocomposites based on dioxidine containing Ag and Cu nanoparticles incorporated in biopolymer cryostructurates

Russian Chemical Bulletin - Cryochemical synthesis of hybrid nanocomposites based on the antibacterial drug, dioxidine, and metals (Ag, Cu) was performed. According to the data of H1 NMR, UV, and...     

Cu/dioxidine hybrid nanocomposites: cryochemical synthesis and antibacterial activity

Hybrid nanocomposites consisting of an antibacterial drug, dioxidine, and copper nanoparticles are obtained by cryochemical synthesis. It is shown by UV spectroscopy, X-ray diffraction, PAM, and low temperature argon adsorption that the obtained hybrid systems represent dioxidine particles with a size of 100 to 400 nm, including copper particles with the size of 50 to 150 nm. The resulting composites possessed higher antibacterial activity against E. coli 52 than the initial dioxidine and copper nanoparticles.     

Cryochemical modification,activity, and toxicity of dioxidine

Dioxidine nanoparticles are prepared via cryochemical modification of the pharmacopoeial dioxidine substance. The form of the cryomodified dioxidine is characterized by data from ¹H NMR spectroscopy; X-ray diffraction analysis; such thermal analytical methods as TG and DSC; low-temperature argon adsorption; and transmission electron microscopy. It is shown that the cryomodified samples are synthesized in the form of dioxidine nanocrystals 50–300 nm in size, with a crystal structure differing from that of the initial pharmacopoeial substance. The prepared cryomodified dioxidine nanoparticles inhibit the growth of E. coli 52, S. aureus 144, M. cyaneum 98, and B. cereus 9 better than the initial pharmacopoeial substance, and have comparable chronic toxicity.     

Obtaining ultradispersed dioxidine powder modified via cryochemical synthesis and determining its antibacterial activity

One way to increase bioavailability and efficiency of drug substances is to decrease their particles up to nanoscale level and to change their crystal structure. A new stable nanoscale form of a polymorphic antibacterial 2,3-bis-(hydroxymethyl)-quinoxaline-N,N′-dioxyde (dioxidine) modification characterized with a gas chromatography, NMR, XRF, TEM, and thermoanalytic methods (TG, DTG, DSC) was obtained via cryochemical synthesis. The new polymorphic dioxidine modification was proved to be more active in growth inhibition processes of gram-positive M. cyaneum 98 and gram-negative E. coli bacterial strains than officinal modification.     

Sucrose ester micellar-mediated synthesis of Ag nanoparticles and the antibacterial properties

Ag nanoparticles with diameter in the range of 10–25 nm had been synthesized using a simple sucrose ester micellar-mediated method. Ag nanoparticles were formed by adding AgNO₃ solution into the sucrose ester micellar solution containing sodium hydroxide at atmospheric condition after 24 h of aging time. Trace amount of dimethyl formamide (DMF) in the sucrose ester solution served as a reducing agent while NaOH acted as a catalyst. The produced Ag nanoparticles were highly stable in the sucrose ester micellar system as there was no precipitation after 6 months of storage. The as-synthesized Ag nanoparticles were characterized using transmission electron microscope (TEM), X-ray diffractometer (XRD), dynamic light scattering (DLS) and UV–vis spectroscopy (UV–vis). Formation mechanism of Ag nanoparticles in the micellar-mediated synthesis is postulated. The antibacterial properties of the Ag nanoparticles were tested against Methicillin-resistant Staphylococcus aureus (MRSA) (Gram-positive) and Aeromonas hydrophila (Gram-negative) bacteria. This work provides a simple and “green” method for the synthesis of highly stable Ag nanoparticles in aqueous solution with promising antibacterial property.     

Effect of amine groups on the synthesis and antibacterial performance of Ag nanoparticles dispersed in aminosilanes-modified silicate

Nanocomposites based on silver (Ag) and organically-modified silicate (Ormosil) were prepared by an in situ reduction method, in which silver nitrate, tetraethoxysilane (TEOS) and aminosilanes with different amine groups acted as precursor, linker and colloidal suspension stabilizers, respectively. The objective of the study was to develop and evaluate aminosilanes-modified silicate impregnated with Ag nanoparticles, in which Ag dispersion is stabilized, to create a composite that protects against biological warfare agents. The physical properties of the Ormosil/Ag nanocomposites were examined using NMR, ESR and SEM spectroscopy, the results of which indicated that the extent of the reduction reaction increases with aminosilanes with a higher number of amine groups. The number of amine groups in the aminosilane has also a strong effect on the size of the resulting Ag particles. The antibacterial effects of the Ormosil/Ag nanocomposites were assessed by the zone of inhibition and plate-counting methods, and an excellent antibacterial performance was discovered.     

Microwave-assisted solution synthesis and photocatalytic activity of Ag nanoparticles supported on ZnO nanostructure flowers

Ag nanoparticles supported on the surface of three-dimensional (3D) flower-like ZnO nanostructure were synthesized by a microwave-assisted solution method. The obtained products were characterized by X-ray diffraction analysis, field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectrophotometry, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The analytical results confirmed homogeneously distributed Ag nanoparticles supported on the surface of flower-like ZnO nanostructure. The photocatalytic effect of the heterostructure Ag/ZnO nanocomposites was investigated using photodegradation under ultraviolet (UV) light of methylene blue as model dye. The heterostructure Ag/ZnO nanocomposites exhibited much higher photocatalytic activity than pure ZnO flowers. The improved photocatalytic properties are attributed to formation of a Schottky barrier at the metal–semiconductor interface of the Ag/ZnO nanocomposites.     

Eco-friendly synthesis and antibacterial activity of silver nanoparticles reduced by nano-wood materials

Hydrothermal treatment of nano-structured wood, prepared by precision grinding, with cationic silver was found to give silver nanoparticles (Ag NPs) of 2–40-nm size range embedded in the wood tissue. The size and distribution of Ag NPs depended strongly on the starting silver ion concentration and reaction temperature. Higher temperature tended to give larger size and wider distribution. The obtained Ag NPs were characterized using various methods, including high-resolution transmission electron microscopy, UV–visible spectroscopy, and X-ray diffraction. The antibacterial effect of the product against Escherichia coli was evaluated by static and dynamic culture experiments, revealing that the Ag NPs-loaded nano-wood materials have great promise as antimicrobial agents against E. coli.     

Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity

A one-step simple synthesis of silver colloid nanoparticles with controllable sizes is presented. In this synthesis, reduction of [Ag(NH(3))(2)](+) complex cation by four saccharides was performed. Four saccharides were used: two monosaccharides (glucose and galactose) and two disaccharides (maltose and lactose). The syntheses performed at various ammonia concentrations (0.005-0.20 mol L(-1)) and pH conditions (11.5-13.0) produced a wide range of particle sizes (25-450 nm) with narrow size distributions, especially at the lowest ammonia concentrations. The average size, size distribution, morphology, and structure of particles were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), and UV/Visible absorption spectrophotometry. The influence of the saccharide structure (monosacharides versus disaccharides) on the size of silver particles is briefly discussed. The reduction of [Ag(NH(3))(2)](+) by maltose produced silver particles with a narrow size distribution with an average size of 25 nm, which showed high antimicrobial and bactericidal activity against Gram-positive and Gram-negative bacteria, including highly multiresistant strains such as methicillin-resistant Staphylococcus aureus. Antibacterial activity of silver nanoparticles was found to be dependent on the size of silver particles. A very low concentration of silver (as low as 1.69 mug/mL Ag) gave antibacterial performance.     

Green synthesis of silver nanoparticles using olive leaf extract and its antibacterial activity

The silver nanoparticles (AgNPs) synthesized using hot water olive leaf extracts (OLE) as reducing and stabilizing agent are reported and evaluated for antibacterial activity against drug resistant bacterial isolates. The effect of extract concentration, contact time, pH and temperature on the reaction rate and the shape of the Ag nanoparticles are investigated. The data revealed that the rate of formation of the nanosilver increased significantly in the basic medium with increasing temperature. The nature of AgNPs synthesized was analyzed by UV–vis spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis (TGA). The silver nanoparticles were with an average size of 20–25 nm and mostly spherical. The antibacterial potential of synthesized AgNPs was compared with that of aqueous OLE by well diffusion method. The AgNPs at 0.03–0.07 mg/ml concentration significantly inhibited bacterial growth against multi drug resistant Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). This study revealed that the aqueous olive leaf extract has no effect at the concentrations used for preparation of the Ag nanoparticles. Thus AgNPs showed broad spectrum antibacterial activity at lower concentration and may be a good alternative therapeutic approach in future.     

Green synthesis,size control,and antibacterial activity of silver nanoparticles on chitosan films

Research on Chemical Intermediates - Silver nanoparticles (AgNPs) synthesized on the surface of chitosan (CS) films using ultraviolet (UV) and natural light irradiation reduction methods were...     

Direct synthesis of a macroscopic array of naked Ag nanoparticles

A 2-D array of naked Ag nanoparticles has been synthesized through interfacial reduction of Ag(+) under hydrothermal conditions. The process bestows the synthesis, nucleation, growth and self-assembly of the nanoparticles in a simple one-pot reaction and makes use of no additive or capping agent. The resulting macroscopic liquid silver mirror is highly stable and composed of tightly packed naked Ag nanoparticles (17 (3) nm diameter, with interparticle gaps of 1.3 (1.0) nm) which can be easily transferred to a given substrate for application.     

Alga-mediated facile green synthesis of silver nanoparticles: Photophysical,catalytic and antibacterial activity

A facile, convenient and green method has been employed for the synthesis of silver nanoparticles (AgNPs) using dried biomass of a green alga, Chlorella ellipsoidea. The phytochemicals from the alga, as a mild and non-toxic source, are believed to serve as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of a surface plasmon resonance band at 436 nm and energy dispersive X-ray spectroscopy. The transmission electron microscopy images showed the nanoparticles to be nearly spherical in shape with different sizes. A dynamic light scattering study revealed the average particle size to be 220.8 ± 31.3 nm. Fourier transform infrared spectroscopy revealed the occurrence of alga-derived phytochemicals attached to the outer surface of biogenically accessed silver nanoparticles. The powder X-ray diffraction study revealed the face-centred cubic crystalline structure of the nanoparticles. The as-synthesized biomatrix-loaded AgNPs exhibited a high photocatalytic activity for the degradation of the hazardous pollutant dyes methylene blue and methyl orange. The catalytic efficiency was sustained even after three reduction cycles. A kinetic study indicated the degradation rates to be pseudo-first order with the degradation rate being 4.72 × 10⁻² min⁻¹ for methylene blue and 3.24 × 10⁻² min⁻¹ for methyl orange. The AgNPs also exhibited significant antibacterial activity against four selected pathogenic bacterial strains.     

Green synthesis of silver nanoparticles by pepper extracts reduction and its electocatalytic and antibacterial activity

Stable silver nanoparticles were synthesized with the aid of a novel, non-toxic, eco-friendly biological material namely, green pepper extract. The aqueous pepper extract was used for reducing silver nitrate. The synthesized silver nanoparticles were analyzed with transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). TEM image shows the formation of silver nanoparticles with average particle size of 20 nm which agrees well with the XRD data. The main advantage of using pepper extract as a stabilizing agent is that it provides long-term stability for nanoparticles by preventing particles agglomeration. To investigate the electrocatalytic efficiency of silver nanoparticles, silver nanoparticles modified carbon-paste electrode (AgNPs–CPE) displayed excellent electrochemical catalytic activities towards hydrogen peroxide (H₂O₂) and hydrogen evolution reaction (HER). The reduction overpotential of H₂O₂ was decreased significantly compared with those obtained at the bare CPE. An abrupt increase of the cathodic current for HER was observed at modified electrode. Also, the antibacterial activity of silver nanoparticle was performed using Escherichia coli and Salmonellae. The approach of plant-mediated synthesis appears to be cost efficient, eco-friendly and easy methods.     

树枝状纳米银颗粒的制备与电活性

在Ag(NH3)2+溶液中,在钛基体上电沉积出树枝状纳米银颗粒,研究了沉积电位对树枝状纳米银颗粒形成的影响,探讨了这种树枝状纳米银颗粒形成的机理,并研究了这种钛基树枝状纳米银电极(Ag/Ti)在碱性溶液中对甲醛氧化的电催化活性。结果表明,在30 mmol/LAg(NH3)2+以及沉积电位在-1.8～-1.2 V(vsAg)时,形成了形态为树枝状的纳米银颗粒。在沉积电位为-1.6 V(vs Ag),Ag(NH3)2+浓度为30 mmol/L的溶液中,电沉积制备的这种树枝状纳米银电极(Ag/Ti)对甲醛氧化具有强的电催化活性。循环伏安曲线表明,在0.1 mol/LNaOH溶液中以及甲醛的浓度范围在0～40 mmol/L,甲醛浓度和它的氧化峰电流密度呈现良好的线性关系,检测下限达到0.662 mmol/L,这种新型的树枝状纳米银电极有望作为甲醛检测的传感器。     

Electroless synthesis of Ag nanoparticles on deposited nanostructured Si films

Two and three-dimensional Ag nanoparticle ensembles were synthesized on deposited nanostructured column-void Si films simply by film immersion into pure Ag(2)SO(4) or AgNO(3) solutions. In addition to functioning as a reducer, this nanostructured material provides immobilization and monodispersion of the Ag nanoparticles due to its systematic nanoscale topography. This is accomplished without the requirement of a surfactant, capping agent, or linker. Kinetics, as monitored from plasmon optical extinction, and infrared spectroscopy suggest accompanying oxide growth limits and finally inhibits synthesis enabling nanoparticle size control. Kinetics is also limited by Ag+ transport through the voids unless the Si film is ultrathin. Our synthesis approach offers significant advantages for surface-enhanced molecular detection, including the absence of any agents on the nanoparticle surfaces and the ability to obtain nanoparticle ensembles on any substrate.     

Synthesis and antibacterial activity of Ag/CeO<Subscript>2</Subscript> hybrid architectures

Flower-like ceria (CeO₂) architectures consisting of well aligned nanosheets were first synthesized by a glycol solvothermal method. The size of CeO₂ architectures is about 5?μm in width and 10?μm in length, with the nanosheets thickness below 100?nm. Subsequently, the adsorbed Ag ions on the surface of CeO₂ were in situ reduced to form Ag nanoparticles (NPs), leading to the fabrication of Ag/CeO₂ hybrid architectures (HAs). The formed Ag NPs with sizes of 20–40?nm were uniformly loaded on the surface of the CeO₂ sheets. The antibacterial properties of Ag/CeO₂ HAs against Gram-negative E. coli and Gram-positive S. aureus were evaluated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and a filter paper inhibition zone method. The results demonstrated that Ag/CeO₂ HAs displayed excellent antibacterial activity toward S. aureus and E. coli, which were attributed to the synergistic antibacterial effect between Ag NPs and CeO₂ in HAs_. Here, CeO₂ nanoflowers as a new substrate could restrict Ag NPs aggregations and improve their antibacterial activities. Therefore, the resulted Ag/CeO₂ HAs would be considered as a promising antibacterial agent.

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Waste-grass-mediated green synthesis of silver nanoparticles and evaluation of their anticancer,antifungal and antibacterial activity

Grass waste was used for transform an inexpensive waste into health. Silver nanoparticles (AgNPs) have been synthesized using waste material (dried grass). The average size of silver nanoparticles observed in transmission electron images was estimated to be about 15?nm. The anticancer, antifungal and antibacterial effect of AgNPs were studied in vitro. The minimum inhibitory concentration of AgNPs against Pseudomonas aeruginosa and Acinetobacter baumannii was calculated about 3?µg/ml. The highest level of inhibitory effect of AgNPs against Fusarium solani was close to 90% at a concentration of 20?μg/ml of AgNPs. An inhibitory effect on the cancer cell growth is reach, by increasing the concentration of AgNPs to 5?µg/ml; the cancer cells’ survival decreases about 30%. Western results showed that the expression of Cyclin D1 protein of MCF-7 cell line decreased after treatment with the effective concentration of AgNPs.     

Green synthesis and antibacterial activity of chalcogenoesters

Herein, we present a new variation for an eco-friendly methodology for the synthesis of chalcogenoester in good-to-excellent yields in a short time, with an easy work-up/purification step, and in a greenest methodology, affording the minimum generation of solid and liquid waste, in comparison to that described in the literature. Additionally, some selected compounds were evaluated as antimicrobial agents, showing moderate activity against a variety of microorganisms including the K. pneumoniae, P. aeruginosa and also some selected fish pathogenic bacteria.