Water-dispersible Silver Nanoparticles Research Articles

Synthesis of Calixarene-Capped Silver Nanoparticles for Colorimetric and Amperometric Detection of Mercury (HgII, Hg0).

Calixarene-functionalized water dispersible silver nanoparticles have been synthesized and characterized on the basis of UV–vis, IR, X-ray diffraction, and high-resolution transmission electron microscopy analysis, and their sensing properties toward metal ions have been investigated. They selectively detect Hg2+ and Hg0 in solution and vapor phases, respectively, with distinct color change. Interference study with mixture of metal ions revealed no interference from any other metal ions used in this study. Their mechanism of detection involved Hg2+-aided displacement of calixarene moiety from the surface of the functionalized nanoparticles, followed by the formation of Ag–Hg amalgam due to interaction of Hg2+ with Ag0 and also the formation of assembly of Ag0 nanoparticles by dipole–dipole interaction of the bare-surfaced nanoparticles. Electrochemical study revealed that with the aid of functionalized nanoparticles, Hg2+ can be detected amperometrically with high sensitivity. The detection limits obtained for Hg2+ by UV–vis study and amperometry are 0.5 nM (0.1 ppb) and 10 nM (2 ppb), respectively. The new material has been used to detect Hg2+ in aqueous real sample and Hg0 in soil sample.

Green Synthesis of Silver Nanoparticles Decorated by Fe₃O₄/GO with Enhanced Catalytic Activity.

We report a simple and green approach to synthesize stable water-dispersible silver nanoparticles decorated by magnetic Fe3O4 and graphene oxide (GO). These results of UV-Vis spectra, along with TEM and SEM indicated that the water-dispersible silver nanoparticles had cluster flat structure and retained the optical properties of the original silver particle. Combining the advantages of Fe3O4 and GO, the composite nanoparticles showed enhanced catalytic activity with good recycling utilization rate by magnetic separation.

Synthesis and antibacterial activity of water-dispersible silver nanoparticles via micellar nanoreactors

We have synthesized silver nanoparticles (AgNPs) using micelles of sugar fatty acid ester by dissolving the surfactant in a mixture of iso-octane and n-butanol, with solid-liquid extraction. Highly concentrated, water-dispersible AgNPs were obtained after thorough washing with alcohol, to remove excess of sucrose fatty acid ester DK SS and salt, followed by drying. The particles were characterized for their size, morphology and crystallinity using UV-Visible spectrophotometry, Transmission Electron Microscopy and x-ray diffractometry. Antibacterial study, confirmed the activity of nanoparticles against E. coli, P. aeruginosa and S. aureus, which causes diseases including diarrhoea and several life-threatening infections. Antibacterial activity of E. coli and P. aeruginosa was found to be 2.5 fold and for S. aureus 1.6 fold compared to 50 ppm conc. of Silver Nitrate. Our method of producing nanoparticles is employed as a platform technology for synthesizing other inorganic nanoparticles. This is the first report discussing the use of micellar carriers for obtaining silver nanopowder, to the best of our knowledge, which has the potential to overcome limitations during fabrication of AgNPs using reverse/inverse micelles. Our method yielded nano-sized, water-dispersible AgNPs via an easy and economic approach. The one-pot approach possesses advantages in terms of cost and simplicity, as compared with traditional methods of producing powdered AgNPs using energy intensive and expensive techniques like lyophilisation. The developed method, thus, possesses immense potential for commercial synthesis of AgNPs.

Synthesis, characterization, mechanistic studies and antimicrobial efficacy of biomolecule capped and pH modulated silver nanoparticles

Increase in the resistance of bacterial strains toward marketed antibiotics formulations has generated a demand to carry out research on the development of new antimicrobial agents. Among the various bacterial toxic components, use of silver nanoparticles as antimicrobial agents is intriguing owing to their high potential activity against the growth of numerous microbes. Moreover, novel and more efficient agents can also be generated by precisely engineering the silver nanoparticles (AgNps) with other optimum antibacterial agents e.g. antimicrobial peptides. In this connection the present study involves the synthesis and detailed characterization of silver nanoparticles capped with building blocks of peptides i.e. amino acids under same reaction conditions. Among all the studied synthesized nanoparticles, histidine capped AgNps showed the most efficient antimicrobial behavior and subsequent studies displayed that histidine-AgNps were also able to significantly reduce the growth of antibiotic resistant strains such as Klebsiella pneumonia, Staphylococcus epidermidis and Staphylococcus aureus. Moreover, the combination of gentamicin and histidine-AgNps showed high synergic effect against bacterial strains. In a nutshell, this report gives a new direction for the development of highly effective antimicrobial agents entails amino acids and water dispersible silver nanoparticles.

Pyrophosphate functionalized silver nanoparticles for colorimetric determination of deferiprone via competitive binding to Fe(III)

The authors describe a colorimetric assay for the determination of the iron chelating drug deferiprone by using water dispersible silver nanoparticles functionalized with pyrophosphate groups (Pyro-AgNPs). The pyro-AgNPs are capable of cooperatively binding Fe3+ ions, and this results in a color change from yellow (peaking at 402 nm) to red (peaking at 520 nm) due to aggregation. However, this binding is competitively overruled, and hence aggregation is prevented in the presence of increasing concentrations of deferiprone. Consequently, the color (which is due to localized surface plasmon resonance) gradually changes from red to yellow, and this can be correlated to the concentration of the drug. The relative amounts of silver nanodispersion and pyrophosphate anions, of the pH values of the medium, and reaction times were optimized. Under the best conditions, the method exhibits a consistent optical response in the 6.0 to 100 μM deferiprone concentration range, with a 280 nM detection limit. The assay is selective over several amino acids, saccharides, and inorganic ions. The method was applied to the determination of deferiprone in pharmaceuticals and in spiked human plasma samples.

Water-dispersible fluorescent silver nanoparticles via sputtering deposition over liquid polymer using a very short thiol ligand

We have developed a novel physical approach for size-controlled synthesis of metal nanoparticles via sputtering deposition over liquid matrix. Here we report a novel water-dispersible, negatively charged fluorescent silver nanoparticles through this method with a very short anionic thiolate ligand. Our previous result showed that multiple hydrogen bonds between carboxylic groups in surface ligands resulted in a very poor dispersilibity of formed nanoparticles, however neutralized sodium 3-mercaptopropionate used in this work could overcome this limitation. We successfully obtained NIR fluorescent, water-dispersible silver nanoparticles for the first time among physical-based approach. Results presented here therefore will widen the spectrum of novel and environmental-friendly strategy for functionalized metal nanoparticles or fluorescent clusters.

Scrupulous recognition of biologically important acids by fluorescent “turn off-on” mechanism of thaicalix reduced silver nanoparticles

Water dispersible silver nanoparticles (AgNps) were prepared using thiacalix[4]arene tetrahydrazide (TCTH) as a reducing and stabilizing agent. TCTH-AgNps were characterized by surface plasmon resonance (SPR), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). Relatively uniform 20nm spherical particles of TCTH-AgNps were efficiently formed over a pH range of 5–9 and from 10–40°C. The interaction behavior of TCTH-AgNps with different amino acids was investigated using spectrophotometry and spectrofluorimetry. Among the amino acids tested, only tryptophan and histidine showed fluorescence quenching and fluorescence enhancement, respectively. The linear detection range by Stern–Volmer plot was 5nmol/L to 0.48μmol/L for tryptophan and 4nmol/L to 0.54μmol/L for histidine. TCTH-AgNps were able to effectively reduce the levels of gram-positive bacteria, gram-negative bacteria, and fungi. These properties argue for the potential use of TCTH-AgNps as detectors of histidine and tryptophan and as antibiotics.

Selective and reactive hydration of nitriles to amides in water using silver nanoparticles stabilized by organic ligands

Water-dispersible silver nanoparticles stabilized by silver–carbon covalent bonds were prepared. They exhibited high catalytic activities for the selective hydration of nitriles to amides in water. The activation of a nitrile group by the functional groups of the substrates and the hydrophobic layer on the nanoparticles influenced the catalyzed reaction were confirmed. Alkyl nitriles could also be selectively hydrated.

Green synthesis of water-dispersible silver nanoparticles at room temperature using green carambola (star fruit) extract

Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the presence of carambola fruit extract at different pH. The UV–Vis absorption revealed that with increase in pH of the solution, the intensity of the peaks became higher and narrower along with blue shift signifying decrease in particle size. Crystallinity of Ag in the synthesized product was determined by X-ray diffraction. Fourier transform infrared spectroscopy confirmed the presence of polyols, aldehydes, amines and organic acids in the fruit extract which became useful as capping and reducing agent for the synthesis of AgNPs. Transmission electron microscopy showed the average particle size of Ag as 16, 13 and 12 nm for pH 4, pH 7 and pH 10, respectively, while the corresponding sizes determined by DLS method were found to be 169, 134 and 80 nm. The high negative zeta potential values indicated dispersion stability of AgNPs. The present method is important in terms of green, energy-efficient and environmentally friendly process.

Synthesis of water-dispersible silver nanoparticles by thermal decomposition of water-soluble silver oxalate precursors.

Silver oxalate, one of the coordination polymer crystals, is a promising synthetic precursor for transformation into Ag nanoparticles without any reducing chemicals via thermal decomposition of the oxalate ions. However, its insoluble nature in solvents has been a great disadvantage, especially for systematic control of crystal growth of the Ag nanoparticles, while such control of inorganic nanoparticles has been generally performed using soluble precursors in homogeneous solutions. In this paper, we document our discovery of water-soluble species from the reaction between the insoluble silver oxalate and N,N-dimethyl-1,3-diaminopropane. The water-soluble species underwent low-temperature thermal decomposition of the oxalate ions at 30 °C with evolution of CO2 to reduce Ag+ to Ag0. Water-dispersible Ag nanoparticles have been successfully synthesized from the water-soluble species in the presence of gelatin via similar thermal decomposition at 100 °C. The gelatin-protected and water-dispersible Ag nanoparticles with a mean diameter of 25.1 nm appeared. In addition, antibacterial activity of the prepared water-dispersible Ag nanoparticles has been preliminarily investigated.

Removal of citrate-coated silver nanoparticles from aqueous dispersions by using activated carbon

This article describes studies on the efficiency of activated carbon as adsorbent for water-dispersible silver nanoparticles. Nanoparticles of average size around 60nm and negative zeta-potential were synthesized by reduction of Ag(I) ions with sodium citrate in aqueous medium. Activated carbon (Norit® CA1) intended for water purification was found to be an efficient adsorbent for silver nanoparticles. It was found that nanoparticle adsorption on activated carbon could be described by Freundlich and Langmuir isotherms. The presence of electrolytes favored nanoparticle deposition on the surface of activated carbon. When electrolytes were used above their critical coagulation concentration aggregated nanoparticles were settling down along with the carbon particles, where carbons were acting as filter aid. This allowed complete removal of nanoparticles from the aqueous dispersions. It is expected that these studies could be important for better understanding of the interactions between nanoparticles and solid–liquid interfaces, for preparation of nanoparticle/carbon composite materials, as well as for designing of methods for removal of metal nanoparticles from contaminated water during treatment of nanowastes.

Micromorphological cellular responses of MC3T3-E1 and RAW264.7 after exposure to water-dispersible silver nanoparticles stabilized by metal-carbon σ-bonds

With the continuous progress in nanomaterial development for biomedicine, the potential cytotoxicity of nanoparticles is drawing more attention and concern for clinical applications. The purpose of this study was to evaluate biological responses of new water-dispersible silver nanoparticles (Ag-NPs) stabilized by Ag-C σ-bonds in cultured murine macrophages (RAW264.7) and osteoblast-like cells (MC3T3-E1) using cell viability and morphological analyses. For RAW264.7, Ag-NPs seemed to induce cytotoxicity that was dependent on the Ag-NP concentration. However, no cytotoxic effects were observed in the MC3T3-E1 cell line. In microscopic analysis, Ag-NPs were taken up by MC3T3-E1 cells with only minor cell morphological changes, in contrast to RAW264.7 cells, in which particles aggregated in the cytoplasm and vesicles. The ability of endocytosis of macrophages may induce harmful effects due to expansion of cell vesicles compared to osteoblast-like cells with their lower uptake of Ag-NPs.

Ultrafine silver nanoparticles with excellent antibacterial efficacy prepared by a handover of vesicle templating to micelle stabilization

We report a role-switching method for preparing ultrafine water-dispersible silver nanoparticles with long-term stability based on a soft deformable block copolymer vesicle. Those ultrafine silver nanoparticles showed excellent antibacterial efficacy against both Gram-negative and Gram-positive bacteria with quite low minimum inhibitory concentrations (MICs) of 16.9 μg mL−1 and 8.45 μg mL−1, respectively.

Synthesis and antibacterial properties of water-dispersible silver nanoparticles stabilized by metal–carbon σ-bonds

The synthesis of 4-diazoniumcarboxylbenzene fluoroborate, a new water-soluble stabilizer for metal nanoparticles (NPs), is described. A stable dispersion of Ag NPs in water was successfully produced by a simultaneous aqueous reduction of this diazonium salt and silver nitrate by NaBH4. UV–vis spectra, TEM images, XRD patterns, and XPS spectra of the obtained Ag NPs revealed that they were stabilized by Ag–C σ-bonds. These NPs showed excellent antimicrobial properties against Staphylococcus aureus.

A Facile and Green Route to Silver Nanoparticles in Water

Stable water-dispersible silver nanoparticles with a narrow size distribution are obtained by light-assisted spontaneous reduction of silver nitrate with gelatin, which acts as both the reducing and the stabilizing agents, in water. The formation mechanism of the silver nanoparticles involves an in-situ conversion of Ag(+)-gelatin aggregates to gelatin-stabilized silver nanoparticles via a Ag(+)-mediated oxidation of primary amine groups of the gelatin to carboxylic acid groups. The resultant silver nanoparticles are well within the quantum size domain (10 nm). In addition, the nanoparticles are stable in aqueous solutions and can be separated easily by simple pH adjustment.

Preparation and characterization of water-dispersible silver nanoparticles stabilized by PEO-conjugated pro-drugs

ω-Anhydride-functionalized poly(ethylene oxide) (PEO) obtained from chain-end functionalization and anionic ring-opening polymerization of ethylene oxide usingn-butyllithium with potassiumt-butoxide in the presence of dimethylsulfoxide (DMSO) was found to be an efficient material for the preparation of water-soluble, polymeric pro-drugs. The reaction of ω-anhydride-functionalized PEO with sulfonamide or with vancomycin provided an efficient method to produce corresponding, water-soluble, PEO-conjugated sulfonamide or PEO-conjugated, vancomycin pro-drugs. These were used successfully to prepare water-dispersible, silver nanoparticles. In this study, the particle sizes were in the range of 5∼40 nm. The resulting products were characterized by1H NMR spectroscopy, transmission electron microscopy, electron and X-ray diffraction, size exclusion chromatography, and UV/Visible spectroscopy.