Preparation and characterization of a novel nanocomposite: silver nanoparticles decorated cerasome

In this study, a novel artificial hybrid vesicle, nano silver particles decorated cerasome were fabricated through sol–gel and self-assemble methods as well as in situ reduction. Samples were characterized in terms of hydrodynamic size and surface morphology via dynamic light scattering as well as scanning and transmission electron microscopies. Analysis through energy dispersive X-ray spectrometer proved the existence of silver particles. Due to the high morphological stability of cerasome, Silver nanoparticles with a size of about 5–10 nm can be deposited on the surface without any stabilizers. The UV spectra revealed a single symmetric extinction peak at 406 nm, confirming the spherical shape of the synthesized silver nanoparticles. Several reducing agents were screened before confirming sodium borohydride (NaBH₄). Comparison of different NaBH₄/lipid ratios (K_{NaBH4/cerasome-forming lipid}) was then carried out in order to ascertain its effect. Investigation of the stability of this hybrid vesicles was carried out, indicating that it can be stored at 4 °C for at least 3 months without any morphological change. Results demonstrated that this hybrid vesicle has excellent morphological stability, which impart it significant potential for various applications such as being an antibacterial material and a radio sensitization agent.     

Controlled Synthesis of Narrow-Dispersed Copper Nanoparticles

A controlled synthesis method for preparing narrow-dispersed copper nanoparticles, using water and ethylene glycol as the reaction media respectively, has been reported. In order to obtain pure-phase copper nanoparticles using water, the reaction time of 8 h is essential. Owing to the reduction property of ethylene glycol, the reaction rate using ethylene glycol is higher. In addition, the amount of reduction agent can reduce largely. Polyvinyl pyrrolidone plays great role on the size of copper particles, and the increasing of polyvinyl pyrrolidone concentration attributes to the smaller dimension particles. The mean diameter is about 4 nm when the concentration of polyvinyl pyrrolidone is 0.5 mmol/L. Polyvinyl pyrrolidone acts as the polymeric capping agents in the reaction, preventing the agglomeration of the copper nanoparticles. When water is the reaction medium, Cu²⁺ complex is reduced to Cu⁺ complex firstly, and the further reduction of Cu⁺ forms the pure copper nanoparticle.     

Fabrication of flower-like silver nanoparticles for surface-enhanced Raman scattering

The flower-like silver nanoparticles have been synthesized by reducing silver nitrate (AgNO₃) with ascorbic acid (AA) as the reductant and polyvinyl pyrrolidone (PVP) as the capping agent under vigorous stirring. Such flower-like nanoparticles are aggregates of small nanoplates and nanorods. They were tested as substrates for the surface-enhanced Raman scattering (SERS), showing high sensitivity for detecting Rhodamine 6G (R6G) at a concentration as low as 10^-7 mol/L. It has been found that replacing mechanical stirring with ultrasound sonication would drastically change the particle morphology, from flower-like nanoparticles to well-dispersed smaller nanoparticles. Furthermore, when trace amounts of NaCl were added into the reagents, well-dispersed Ag nanoparticles formed even in vigorous stirring. These phenomena can be explained with the diffusion and reactant supply during nucleation and growth of Ag nanoparticles.     

Morphology and size-controlled synthesis of silver nanoparticles in aqueous surfactant polymer solutions

We have employed a number of reducing and capping agents to obtain Ag(0) metallic nanoparticles of various sizes and morphologies. The size and morphology were tuned by selecting reducing and capping agents. Spherical particles of 15 and 43 nm diameter were obtained when 1 wt% aqueous starch solution of AgNO₃ precursor salt was reduced by d(+)-glucose and NaOH, respectively, on heating at 70 °C for 30 min. Smaller size particles obtained in the case of d(+)-glucose reduction has been attributed to the slow reduction rate by mild reducing agent d(+)-glucose compared to strong NaOH. Conducting the reduction at ambient temperature of silver salt in liquid crystalline pluronic P123 and L64 also gave spherical particles of 8 and 24 nm, respectively, without the addition of any separate reducing agent. NaOH reduction of salt in ethylene glycol (11 g)/polyvinyl pyrolidone (PVP; 0.053 g) mixture produced large self-assembled cubes of 520 nm when smaller (26–53 nm) star-shaped sharp-edged structures formed initially aggregated on heating the preparation at 190 °C for 1 h. Increasing the amount of PVP (0.5 g) in ethylene glycol (11 g) and heating at 70 °C for 30 min yielded a mixture of spherical and non-spherical (cubes, hexagons, pentagons, and triangle) particles without the addition of an extra reducing agent. Addition of 5 wt% PVP to 1 wt% aqueous starched solution resulted in the formation of a mixture of spherical and anisotropic structures when solution heated at 70 °C for 1 h. Homogeneous smaller sized (29 nm) cubes were synthesized by NaOH reduction of AgNO₃ in 12.5 wt% of water-soluble polymer poly(methyl vinyl ether) at ambient temperature in 30 min reaction time.     

Preparation of nano-silver-supported activated carbon using different ligands

In this study, we investigated the effect of water soluble ligands [i.e., sodium borohydride (NaBH₄), polyvinyl alcohol, glucose and galactose] on the preparation of nano-silver-supported activated carbon (AC). Ligand-stabilized Ag nanoparticle dispersion characteristics were also compared with those of ligand-free Ag nanoparticles. The nanoparticle distribution was investigated using a scanning electron microscope (SEM) which enabled a qualitative analysis of ligand-dependent nanoparticle adsorption onto AC. Silver nanoparticles with average sizes ranging from 7 to 20 nm were synthesized with different coatings. In particular, silver nanoparticles reduced and stabilized by NaBH₄ were found to have a dense and homogenous dispersion of sizes in the range of 100–400 nm on the AC surface. These particles also seemed to remain on the AC surface after rinsing with water. The distribution of silver nanoparticles prepared in the presence of NaBH₄/PVA was not as good as the one prepared with NaBH₄. Their aggregate size varied from 300 to 600 nm on the AC surface and particles greater than 500 nm were eliminated from the AC surface upon rinsing with water. Glucose- and galactose-stabilized silver nanoparticles did not display an extensive adsorption and their adsorption seemed to be poor. However, glucose-stabilized silver nanoparticles could still be detectable to some extent after rinsing, while galactose-stabilized ones could not. Antimicrobial studies showed that all silver-containing carbons studied in this study inhibit bacterial growth and act as bacteriostatic agents.     

Preparation of silver nanoparticles with controlled particle size

Silver colloids show different colors due to light absorption and scattering in the visible region based on plasmon resonance. The resonance wavelength depends on particle size and shape. Here we report chemical reduction methods for preparation of silver nanoparticles exhibiting multicolor in aqueous solutions. Depending on chemical conditions the obtained nanoparticles are different regarding size and morphology.In order to investigate the relationship between size, stability and color of silver colloids we obtained silver nanoparticles in aqueous solutions using different reducing agents. The effect of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) on stabilization of obtained silver colloids was investigated. We have also studied the effect of silver precursor and its concentration on the formation of stable silver colloids.UV-VIS spectrum for silver colloids contains a strong plasmon band near 410 nm, which confirms silver ions reduction to Ag° in the aqueous phase. The formation of metal silver was also confirmed by powder X-ray diffraction (XRD) analysis. The diameter size of silver nanoparticles was in the range from 5 nm to 100 nm     

The Influence of the Capping Agent on the Oxidation of Silver Nanoparticles: Nano‐impacts versus Stripping Voltammetry

The influence of capping agents on the oxidation of silver nanoparticles was studied by using the electrochemical techniques of anodic stripping voltammetry and anodic particle coulometry (“nano‐impacts”). Five spherical silver nanoparticles each with a different capping agent (branched polyethylenimine (BPEI), citrate, lipoic acid, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP)) were used to perform comparative experiments. In all cases, regardless of the capping agent, complete oxidation of the single nanoparticles was seen in anodic particle coulometry. The successful quantitative detection of the silver nanoparticle size displays the potential application of anodic particle coulometry for nanoparticle characterisation. In contrast, for anodic stripping voltammetry using nanoparticles drop casting, it was observed that the capping agent has a very significant effect on the extent of silver oxidation. All five samples gave a low oxidative charge corresponding to partial oxidation. It is concluded that the use of anodic stripping voltammetry to quantify nanoparticles is unreliable, and this is attributed to nanoparticle aggregation.     

稳定分散的纳米银溶胶的制备及其表征

Stable aqueous dispersive colloidal Ag nanoparticles were prepared by reducing silver nitrate with sodium borohydride in the presence of 3-mercaptopropionic acid. The formation process of the Ag nanoparticles was investigated by UV-Visible spectroscopy and transmission electron microscopy. The results show that the spherical and rodlike particles and aggregates are formed in the initial stage of the reaction， then the rodlike particles and aggregates are gradually decomposed into small spherical particles， and the final obtained Ag nanoparticles with an average size of 8 nm are in uniform shapes and narrow size distribution， and the colloid remains stable for more than one month， which makes it convenient for use in practice. The presence of capping agent plays an extra role over nanoparticles stabilization and morphology. The presence of capping agent on the surface of Ag nanoparticle is confirmed by the X-ray photoelectron spectroscopy. It is found that Ag nanoparticles are negatively charged in alkaline condition， whereas they are positively charged in acid condition. Electrosteric effect is responsible for their long-term stability.     

A High-Performance Catalytic and Recyclability of Phyto-Synthesized Silver Nanoparticles Embedded in Natural Polymer

The present work deals with phytogenic synthesis of Ag NPs in the natural polymer alginate as support material using Aglaia elaeagnoidea leaf extract as a reducing, capping, and stabilizing agent. Ag nanoparticles embedded in alginate were characterized using UV–Vis absorption spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy techniques and selected area electron diffraction techniques. The formation of AgNPs embedded in the polymer was in spherical shape with an average size of 12 nm range has been noticed. The prepared embedded nanoparticles in polymer were evaluated as a solid heterogeneous catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and methylene blue to leuco methylene blue in the liquid phase using sodium borohydride (NaBH₄) as reducing agent. The silver nanoparticles embedded polymer exhibited extraordinary catalytic efficacy in reduction of 4-NP to 4-AP and the rate constant is 0.5054 min^?1 at ambient conditions. The catalyst was recycled and reused up to 10 cycles without significant loss of catalytic activity. The preparation of Ag–CA composite was facile, stable, efficient, eco-friendly, easy to recycle, non-toxic, and cost effective for commercial application.     

Green Synthesis and Characterization of Silver Nanoparticles Using Ferocactus echidne Extract as a Reducing Agent

The green synthesis of silver nanoparticles using an aqueous extract of Ferocactus echidne(a member of the cactus family) as a reducing agent is reported. It is simple, efficient, rapid, and ecologically friendly compared to chemical-mediated methods. Ferocactus echidne is a plant of high medicinal value and rich in polyphenolic antioxidants. The extraction is simple and the product rapidly reduces silver ions without involvement of any external chemical agent. The reduction of silver nanoparticles was characterized by ultraviolet-visible spectrometry as a function of time and concentration. The results show that Ferocactus echidne reduces silver ions within 6 h depending upon the concentration. Further increases in reaction time may result in a blue shift, indicating an increase in particle size, whereas concentration had a minor effect on the particle size. The structure of synthesized nanoparticles was investigated by infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and elliptical in shape with diameters of 20 to 60 nm. X-ray diffraction confirmed the formation of silver nanoparticles with an approximate 20 nm particle size calculated using the Debye-Scherer equation. Biological tests revealed that the silver nanoparticles were active against gram positive and negative bacteria( Escherichia coli and Staphylococcus aureus) and fungi (Candida albicans), indicating their broad spectrum antibiotic and antifungal abilities.     

Microwave-Assisted Green Synthesis of Gold Nanoparticles Using Olibanum Gum (Boswellia serrate) and its Catalytic Reduction of 4-Nitrophenol and Hexacyanoferrate (III) by Sodium Borohydride

In this work we report straightforward, an economically viable, one-step microwave-assisted green synthesis of well stabilized gold nanoparticles (AuNPs) by reducing chloroauric acid with natural water soluble olibanum gum (Boswellia serrate). The olibanum gum acts as a dual role of reducing and capping agent for synthesis of AuNPs. The formation of AuNPs was confirmed using UV–Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and electron diffraction. The results indicated that the synthesized NPs were well dispersed and spherical in shape had an average diameter of 3 ± 2 nm. The reaction parameters significantly affected the formation of NPs, as the concentration of gum and irradiation time increases the formation of NPs particles increases and size of particles are reduced. In addition, it has been shown that these olibanum gum capped AuNPs functioned as effective homogeneous catalyst for the reduction of two model reactions hexacyanoferrate(III) and 4-nitrophenol by sodium borohydride. The kinetic investigations were carried out at different amount of AuNPs and different temperatures.     

Simple Characterization of Green-Synthesized Silver Nanoparticles by Capillary Electrophoresis

The development of methodologies for the characterization of silver nanoparticles (AgNPs) synthesized using natural products has received increasing attention, especially to monitoring its stability and size for further application. In this paper, a capillary electrophoretic (CE) method is presented for characterization of AgNPs synthesized using honey or glucose as reducing agents. A simple electrolyte solution composed of 20 mM sodium borate and 20 mM sodium dodecylsulfate (SDS) at pH 8.5 was used for separation of AgNPs within a short analysis time (<12 min). The obtained results were compared with the traditional characterization techniques, such as transmission electron microscopy (TEM) and dynamic light scattering (DLS), showing satisfactory correlation in terms of size distribution. In addition, valuable information about electrophoretic mobility and zeta potential values of AgNPs was obtained by applying the CE-UV/Vis method. Thus, the proposed methodology represents a straightforward tool for the fast and cost-effective characterization of AgNPs within a single analysis, employing minimal amounts of reagents and samples.     

Green Synthesis of Fe and Fe/Pd Bimetallic Nanoparticles in Membranes for Reductive Degradation of Chlorinated Organics

Membranes containing reactive nanoparticles (Fe and Fe/Pd) immobilized in a polymer film (polyacrylic acid, PAA-coated polyvinylidene fluoride, PVDF membrane) are prepared by a new method. In the present work a biodegradable, non-toxic -"green" reducing agent, green tea extract was used for nanoparticle (NP) synthesis, instead of the well-known sodium borohydride. Green tea extract contains a number of polyphenols that can act as both chelating/reducing and capping agents for the nanoparticles. Therefore, the particles are protected from oxidation and aggregation, which increases their stability and longevity. The membrane supported NPs were successfully used for the degradation of a common and highly important pollutant, trichloroethylene (TCE). The rate of TCE degradation was found to increase linearly with the amount of Fe immobilized on the membrane, the surface normalized rate constant (k(SA)) being 0.005 L/m(2)h. The addition of a second catalytic metal, Pd, to form bimetallic Fe/Pd increased the k(SA) value to 0.008 L/m(2)h. For comparison purposes, Fe and Fe/Pd nanoparticles were synthesized in membranes using sodium borohydride as a reducing agent. Although the initial k(SA) values for this case (for Fe) are one order of magnitude higher than the tea extract synthesized NPs, the rapid oxidation reduced their reactivity to less than 20 % within 4 cycles. For the green tea extract NPs, the initial reactivity in the membrane domain was preserved even after 3 months of repeated use. The reactivity of TCE was verified with "real" water system.     

Phytochemical fabrication and characterization of silver nanoparticles by using Pepper leaf broth

The Pepper leaves extract acts as a reducing and capping agent in the formation of silver nanoparticles. A UV–Vis spectrum of the aqueous medium containing silver nanoparticles demonstrated a peak at 458 nm corresponding to the plasmon absorbance of rapidly synthesized silver nanoparticles that was characterized by UV–Vis spectrophotometer. The morphology and size of the benign silver nanoparticles were carried out by the transmission electron microscope (TEM) and field emission scanning electron microscope (FE-SEM). The sizes of the synthesized silver nanoparticles were found to be in the range of 5–60 nm. The structural characteristics of biomolecules hosted silver nanoparticles were studied by X-ray diffraction. The chemical composition of elements present in the solution was determined by energy dispersive spectrum. The FTIR analysis of the nanoparticles indicated the presence of proteins, which may be acting as capping agents around the nanoparticles. This study reports that synthesis is useful to avoid toxic chemicals with adverse effects in medical applications rather than physical and chemical methods.     

Optimized Synthesis of Silver Nanoparticles by Factorial Design with Application for the Determination of Melamine in Milk

A colorimetric method based on silver nanoparticles was developed for the determination of melamine in milk. Silver nanoparticles were synthesized without any stabilizer, using sodium borohydride as the reducing agent. Optimization of the variables for the formation of the nanoparticles was performed by factorial design, resulting in stable colloidal silver nanoparticles with a mean diameter of 14.0?±?2.7?nm. Spectrophotometric measurements performed at 475?nm showed a linear range from 0.033 to 1.50?mg?L^?1 of melamine with limits of detection and quantification of 0.009 and 0.031?mg?L^?1, respectively. The method provided highly sensitive determination of melamine in milk.     

Green Synthesis and Characterization of Silver Nanoparticles Using Ascomycota Fungi Penicillium nalgiovense AJ12

A new method for green synthesis of silver nanoparticles using the cell-free filtrate of Penicillium nalgiovense AJ12 as reducing and protecting agent was described. The pathway is based on the reduction of Ag¹⁺ by protein(s). Various techniques such as UV–Vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared and Zeta potential measurements were used to characterize the silver nanoparticle obtained. The results revealed synthesis of the spherical silver nanoparticles coated with protein(s). The average size of the particles obtained from TEM was 15.2 ± 2.6 nm. DLS measurements showed that the particle size was higher than that estimated from TEM measurements and was 25.2 ± 2.8 nm. Studies on the role of the cell-free filtrate proteins in the synthesis of silver nanoparticles indicated that the process is non-enzymatic but involves amino acids interactions with silver ions. It was found that the aqueous silver nanoparticles suspensions exhibited excellent stability over a wide range of ionic strength, pH and temperature.     

Pd-Ag合金纳米线的可见光辅助简易合成及其对乙醇的电催化氧化

以硝酸钯和硝酸银为金属前驱体,乙醇和柠檬酸钠作为还原剂,聚乙烯吡咯烷酮作为稳定剂和导向剂,以普通市售白炽灯作为光源,采用简易可见光辅助液相法合成了Pd-Ag合金纳米线。通过FESEM、TEM、HRTEM、PXRD和UV-Vis等技术对样品的形貌、晶体结构和光学性质进行了表征,并通过循环伏安法和计时电流法研究了Pd-Ag合金纳米线修饰玻碳电极对乙醇的电催化氧化。与相同条件下制备的纳米钯材料相比,Pd-Ag合金纳米线具有更好的电催化活性、抗中毒性和稳定性。     

Pd-Ag合金纳米线的可见光辅助简易合成及其对乙醇的电催化氧化

以硝酸钯和硝酸银为金属前驱体,乙醇和柠檬酸钠作为还原剂,聚乙烯吡咯烷酮作为稳定剂和导向剂,以普通市售白炽灯作为光源,采用简易可见光辅助液相法合成了Pd-Ag合金纳米线。通过FESEM、TEM、HRTEM、PXRD和UV-Vis等技术对样品的形貌、晶体结构和光学性质进行了表征,并通过循环伏安法和计时电流法研究了Pd-Ag合金纳米线修饰玻碳电极对乙醇的电催化氧化。与相同条件下制备的纳米钯材料相比,Pd-Ag合金纳米线具有更好的电催化活性、抗中毒性和稳定性。     

Fabrication of magnetite nanoparticles (Fe3O4-NPs) for catalytic pyrolysis of nutshells biomass

The fabrication of nanoparticles has been perused as a topic of critical importance in the present decades. Biosynthesis of nanoparticles employs plants extract instead of harmful chemicals. These plant extracts act as reducing and capping agents which is the most appropriate and eco-friendly method among all the preparative routs. In present study, the magnetite nanoparticles (Fe₃O₄-NPs) were fabricated using rapid, single step and benign biosynthetic rout by reduction of ferric nitrate nonahydrate solution with Ferocactus echidne aqueous extract containing ascorbic acid as a main reducing and capping agent. The structural and morphological properties of prepared iron oxide nanoparticles were investigated by Powder X-ray diffraction and scanning electron microscopy. The size of the synthesized nanoparticles was approximately 15 ± 2 nm as determined by Scherrer equation. The biosynthetically fabricated nanoparticles were employed as catalyst for pyrolysis of nutshells to produce biofuel. Catalytic pyrolysis of biomass yields biofuel as an alternative source of energy and chemical feed stock. Effect of temperature, heating rate, and amount of catalyst were investigated on conversion percentage and product yields. Aniline point, carbon residue, and cetane number of prepared bio-oil were also determined.     

Ionic liquid-assisted synthesis of silver nanorods by polyol reduction

<正>Silver nanorods have been successfully synthesized in large scale by the ethylene glycol(EG) reduction in the presence of ionic liquid(IL) 1-butyl-3-methylimidazolium tetrafluoroborate(bmimBF_4) and polyvinyl-pyrrolidone(PVP).The silver nanorods were characterized by scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),transmission electron microscopy(TEM),electron energy disperse spectroscopy(EDS) and UV-vis spectroscopy.The results showed that the uniform silver nanorods have an average diameter of about 100 nm and the aspect ratio from 15 to 20.IL,bmimBF_4 may play a role of capping agent together with PVP in the formation of silver nanorods.On the other band,bmimBF_4 may accelerate nucleation and improve the stability of the resulting Ag nanorods due to the low interface tension of IL.