A novel one step synthesis of silver nanoparticles using room temperature ionic liquid and their biocidal activity

This article reports the synthesis of silver Nan particles (SNPs) using 1-(dodecyl) 2 amino-pyridinium bromide ionic liquid. This is a new one phase method for the synthesis of uniform monodispersed crystalline silver nanoparticles in a water-ionic liquid system. In this work, the functionalized room temperature IL acts as stabilizing agent and solvent. Hydrazine hydrate acts as reducing agent. To the best of our knowledge, there is no report of the synthesis of metal nanoparticles using this ionic liquid. The synthesis of silver nanoparticles is very primarily studied by UV-Visible spectroscopic analysis. The TEM and particle size distribution was used to study morphology and size of the particles. The charge on synthesized SNPs was determined by Zeta potential. The silver nanoparticles have been known to have inhibitory and bactericidal effect. The investigation of antibacterial activities of ionic liquid stabilized silver nanoparticles was performed by measurement of the minimum inhibitory concentration.     

Hexazamacrocycle assisted sensing of silver ion through facile synthesis of silver nanoparticles

The ease of generation of silver nanoparticles by using hexazamacrocycle ligand, L1 is utilized for the visual detection of the presence of silver ions at lower concentrations.     

Paramagnetic behaviour of silver nanoparticles generated by decomposition of silver oxalate

Silver oxalate Ag₂C₂O₄, was already proposed for soldering applications, due to the formation when it is decomposed by a heat treatment, of highly sinterable silver nanoparticles. When slowly decomposed at low temperature (125 °C), the oxalate leads however to silver nanoparticles isolated from each other. As soon as these nanoparticles are formed, the magnetic susceptibility at room temperature increases from −3.14 10⁻⁷ emu.Oe⁻¹.g⁻¹ (silver oxalate) up to −1.92 10⁻⁷ emu.Oe⁻¹.g⁻¹ (metallic silver). At the end of the oxalate decomposition, the conventional diamagnetic behaviour of bulk silver, is observed from room temperature to 80 K. A diamagnetic-paramagnetic transition is however revealed below 80 K leading at 2 K, to silver nanoparticles with a positive magnetic susceptibility. This original behaviour, compared to the one of bulk silver, can be ascribed to the nanometric size of the metallic particles.     

Silver nanoparticles blended PEG/PVA nanocomposites synthesis and characterization for food packaging

In this research investigation Silver nanoparticles were synthesised using rapid biological methods using leaf broth of Capparis zeylanica that provides an environmentally friendly, simple and efficient route for synthesis. Anti-microbial study was investigated against different pathogenic bacteria. Synthesized AgNPs were blended with PVA/PEG biopolymer blend and it has been confirmed by FTIR, DSC, Moisture absorption and Anti-microbial analysis that the AgNPs enhances the stability of the polymer PVA/PEG. This thin film composite shows an excellent characteristic in all aspect that able it for food packaging and bio medical applications.     

Preparation and characterization of stable monodisperse silver nanoparticles via photoreduction

Silver nanoparticles were synthesized by UV irradiation of [Ag(NH₃)₂]⁺ aqueous solution using poly(N-vinyl-2-pyrrolidone) (PVP) as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima around 420 nm. It was found that the formation rate of silver nanoparticles from Ag₂O was much quicker than that from AgNO₃, and the absorption intensity increased with PVP concentration as well as irradiation time. The maximum absorption wavelength (λ_max) was blue shift with increasing PVP content until 8 times concentration of [Ag(NH₃)₂]⁺ (wt%). The transmission electron microscopy (TEM) showed the resultant particles were 4–6 nm in size, monodisperse and uniform particle size distribution. X-ray diffraction (XRD) demonstrated that the colloidal nanoparticles were the pure silver. In addition, the silver nanoparticles prepared by the method were stable in aqueous solution over a period of 6 months at room temperature (25 °C).     

A comparative study of the antibacterial mechanisms of silver ion and silver nanoparticles by Fourier transform infrared spectroscopy

In this study, we performed the first comparative study of the antibacterial mechanisms of silver ion (Ag⁺) and silver nanoparticles (AgNPs) on Escherichia coli (E. coli) using Fourier transform infrared (FTIR) spectroscopy. Through a thorough analysis of the FTIR spectra of E. coli after silver treatment in the spectral regions corresponding to thiol group, protein, lipopolysaccharide (LPS), and DNA, we were able to reveal a multifaceted antibacterial mechanism of silver at the molecular level for both Ag⁺ and AgNPs. Features of such mechanism include: (1) silver complexes with thiol group; (2) silver induces protein misfolding; (3) silver causes loss of LPS from bacterial membrane; (4) silver changes the overall conformation of DNA. Despite the similarities between Ag⁺ and AgNPs with respect to their antibacterial mechanisms, we further revealed that Ag⁺ and AgNPs display quite different kinetics for silver-thiol complexation and loss of LPS, with Ag⁺ displaying fast kinetics and AgNPs displaying slow kinetics. At last, we proposed a hypothesis to interpret the observed different behaviors between Ag⁺ and AgNPs when interacting with E. coli.     

Synthesis and applications of silver nanoparticles

Over the past few decades, nanoparticles of noble metals such as silver exhibited significantly distinct physical, chemical and biological properties from their bulk counterparts. Nano-size particles of less than 100 nm in diameter are currently attracting increasing attention for the wide range of new applications in various fields of industry. Such powders can exhibit properties that differ substantially from those of bulk materials, as a result of small particle dimension, high surface area, quantum confinement and other effects. Most of the unique properties of nanoparticles require not only the particles to be of nano-sized, but also the particles be dispersed without agglomeration. Discoveries in the past decade have clearly demonstrated that the electromagnetic, optical and catalytic properties of silver nanoparticles are strongly influenced by shape, size and size distribution, which are often varied by varying the synthetic methods, reducing agents and stabilizers. Accordingly, this review presents different methods of preparation silver nanoparticles and application of these nanoparticles in different fields.     

Spontaneous formation of silver nanoparticles in aminosilica

We report a rapid and spontaneous metallization process associated with sol–gel reaction of aminosilane that can be utilized to synthesise silver embedded silica nanocomposite without involving additional reducing agents. The reduction reaction induced by bis[3-(trimethoxysilyl)propyl]ethylenediamine (enTMOS) involves amine functional moieties, which drive the reduction reaction with presence of water. Cyclic voltammetry was used to investigate the redox potential of enTMOS and its relation to chemical environment. It was found that the oxidation potential of enTMOS depending on the amount of water (water:enTMOS (v/v) = 8:1–0:1) ranges from 0.48 to 0.68 V versus Ag/AgCl electrode in methanol. The oxidation potential of aminosilane decreases with water content and becomes more negative than that of Ag, suggesting the aminosilane acts as a silver reducing agent while serving as a matrix to encapsulate silver nanoparticles after reacting with water. This process has been utilized to produce evenly dispersed silver nanoparticles with sizes ranging from 5 to 20 nm in both liquid and solid forms of aminosilane, allowing us to prepare silver nanoparticles doped silica nanocomposite that exhibits enhanced electrochemical properties.     

Synthesis of silver nanoparticles with different shapes

Today the synthesis of silver nanoparticles is very common due to their numerous applications in various fields. Silver nanoparticles have unique properties such as: optical and catalytic properties, which, depend on the size and shape of the produced nanoparticles. So, today the production of silver nanoparticles with different shapes which have various uses in different fields such as medicine, are noted by many researchers. This article, is an attempt to present an overview of the shape-controlled synthesis of silver nanoparticles using various methods.     

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.     

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.     

Ionic liquids-assisted greener preparation of silver nanoparticles

1. Download : Download high-res image (298KB)
2. Download : Download full-size image

     

Aptamer-functionalized silver nanoparticles for scanometric detection of platelet-derived growth factor-BB

In this work, we reported a scanometric assay system based on the aptamer-functionalized silver nanoparticles (apt-AgNPs) for detection of platelet-derived growth factor-BB (PDGF-BB) protein. The aptamer and ssDNA were bound with silver nanoparticles by self-assembly of sulfhydryl group at 5′ end to form the apt-AgNPs probe. The apt-AgNPs probe can catalyze the reduction of metallic ions in color agent to generate metal deposition that can be captured both by human eyes and a flatbed scanner. Two different color agents, silver enhancer solution and color agent 1 (10 mM HAuCl₄ + 2 mM hydroquinone) were used to develop silver and gold shell on the surface of AgNPs separately. The results demonstrated that the formation of Ag core–Au shell structure had some advantages especially in the low concentrations. The apt-AgNPs probe coupled with color agent 1 showed remarkable superiority in both sensitivity and detection limit compared to the apt-AuNPs system. The apt-AgNPs system also produced a wider linear range from 1.56 ng mL⁻¹ to 100 ng mL⁻¹ for PDGF-BB with the detection limit lower than 1.56 ng mL⁻¹. The present strategy was applied to the determination of PDGF-BB in 10% serum, and the results showed that it had good specificity in complex biological media.     

Colloidal silver nanoparticles stabilized by a water-soluble triosmium cluster

Silver nanoparticles stabilized by the water soluble triosmium cluster Os₃(μ-H)(CO)₁₀S(CH₂)₁₀COO]Na were prepared by both photochemical and chemical reduction of silver nitrate. The silver nanoparticles were characterized by UV-Vis spectroscopy and high resolution TEM. The particles obtained by chemical reduction showed remarkable stability.     

Preparation of silver nanoparticles in liquid crystalline systems

Silver nanoparticles preparation and the aggregation stability of the particles was investigated in lamellar liquid crystalline systems. A liquid crystal of HDTABr/pentanol/water was first prepared. The water content was next increased while keeping the mass ratio of HDTABr and pentanol constant. Silver nanoparticles were produced by replacing the aqueous phase by Ag sols of various concentrations (0.5–5×10^–3 mol/l) or by an in situ preparation method, i.e., interlamellar reduction of Ag⁺ ions in the liquid crystalline phase. The stability of the silver nanoparticles was monitored by UV-VIS spectroscopy and TEM. The particle size ranged from 5 to 44 nm. The kinetic of silver nanoparticle aggregation was investigated. The effect of nanoparticles on structural ordering in liquid crystals was studied by XRD measurements and it was established that the lamellar distance (d_L) was only slightly altered. Electronic Publication     

Direct formation of silver nanoparticles in cuttlebone-derived organic matrix for catalytic applications

Development of biologically derived materials for the construction of materials with new functions is a crucial intersection of materials science and biotechnology, which is currently a topic of research interest. In this paper, we report on the use of cuttlebone-derived organic matrix (CDOM) as scaffold and reducer for the formation of silver nanoparticles (AgNPs). The experiment was carried out by simple immersing of CDOM in tollen’s reagent and incubating at 80 °C. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs are influenced by the incubation time and protein component in CDOM. Furthermore, the AgNPs–CDOM composite was applied to catalyze the reduction of 4-nitrophenol in the presence of NaBH₄, and it can be easily separated from the liquid-phase reaction system during the reusing cycles.     

Highly-loaded silver nanoparticles in ultrafine cellulose acetate nanofibrillar aerogel

A facile method was developed to load a large amount of silver nanoparticles into a biodegradable and biocompatible cellulose acetate (CA) nanofibrillar aerogel in a controlled manner. The micro-sized CA fibrils were separated into nano-sized fibrils by salt-assisted chemical treatment in a water-acetone co-solvent to give a nanofibrillar structure with a diameter of 20-50 nm, BET surface area of 110 m²/g, and porosity of 96%. Using the high electron-rich oxygen density in the CA macromolecules and the large surface area of the CA nanoporous structure as an effective nanoreactor, the in-situ direct metallization technique was successfully used to synthesize Ag nanoparticles with an average diameter of 2.8 nm and a loading content of up to 6.98 wt%, which can hardly be achieved by previous methods. This novel procedure provides a facile and economic way to manufacture Ag nanoparticles supported on a porous membrane for various biomedical applications.     

Antibacterial studies of bio-functionalized carbon decorated silver nanoparticles (AgNPs)

In the present report, Lemon juice (bio-extract) extract was efficaciously used for the synthesis of bio-functionalized silver nanoparticles (Ag-1, Ag-2 & Ag-3 NPs) and decorated with carbon material obtained from mustard oil. The morphology, size, crystal structure, formation and interaction were studied by means of innumerable analytical methods including scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD results approve the formation of AgNPs with face-centered cubic (fcc) lattice. The XRD results also exhibit some unassigned peaks which might be due to the presence of bio-organic materials on the surface of AgNPs. The bands observed from the IR spectra showing the involvement of biomolecules onto the surface of silver nanoparticles. Mostly citric acid plays a major role in bio-reduction, capping agent, and stabilization of silver ions. We attained maximal inhibition zone (2.10 ​± ​0.05 and 2.03 ​± ​0.027) counter to gram-negative bacteria K. pneumoniae and P. bacilli with Ag-3 respectively, but lowest inhibition zone (1.27 ​± ​0.22) contrary to S. aureus as a gram-positive bacteria with Ag-2.     

Application of micellar electrokinetic chromatography for detection of silver nanoparticles released from wound dressing

The recent emergence of nanotechnology has provided a new therapeutic modality in case of silver nanoparticles. Dressings containing silver form the basis for the treatment of burns and wounds, either acute or chronic ones. The aim of the study was to examine silver release from the different wound dressings: commercially available (Atrauman Ag, Aquacel Ag) and experimental (FKDP‐AgNPs) using MEKC. In order to characterize prepared keratin based wound dressing before and after its modification with AgNPs, a compositional analysis was conducted using energy dispersive X‐ray spectroscopy. Nanosilver toxicity was evaluated with the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4 sulfophenyl)‐2H‐tetrazolium test. Silver release from wound dressings was assessed using MEKC. The best separation was observed for MEKC in 20 mM borate buffer at pH 9 with 20 mM SDS addition. In vitro studies showed silver at higher concentration than 10 ppm exerted a toxic effect on fibroblasts isolated from diabetic mice versus. NIH/3T3 and BJ cell lines (p < 0.05). We observed silver was released more gradually from experimental FKDP‐AgNPs wound dressing, in compare to commercially available wound dressings. The fast and low‐cost method utilizing MEKC can be used in clinical practice to detect silver release from the wound dressings.     

Green biosynthesis of silver nanoparticles using Torreya nucifera and their antibacterial activity

Silver nanoparticles were biosynthesized with the aid of a novel and eco-friendly biological material Torreya nucifera. Temperature and extract concentration were found to influence the size and shape of the biosynthesized silver nanoparticles. Morphological images of biosynthesized nanomaterials revealed that the particles are in spherical shape and size ranging between 10 and 125 nm. Crystalline nature of nanoparticles in face centered cubic (fcc) structure was ensured by diffraction pattern peaks corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes. Characterization of the biosynthesized nanoparticles was performed by the X-ray diffraction and Fourier Transform Infrared spectroscopy analyses. FT-IR analysis indicates that nanoparticles are bound to proteins through amine groups of the aminoacid. Furthermore the biosynthesized nanoparticles were found to be highly effective against Salmonella typhimurium bacterium, which validates its potential applications as antibacterial agents in drinking water treatment and in food packagings.