Metal Nanoparticles In Water Research Articles

One-Step Photochemical Green Synthesis of Water-Dispersible Ag, Au, and Au@Ag Core-Shell Nanoparticles.

A simple and green synthetic protocol for the rapid and effective preparation of Ag, Au and Au@Ag core-shell nanoparticles (NPs) is reported based on the light irradiation of a biocompatible, water-soluble dextran functionalized with benzophenone (BP) in the presence of AgNO3 , HAuCl4 , or both. Photoactivation of the BP moiety produces the highly reducing ketyl radicals through fast (<50 ns) intramolecular H-abstraction from the dextran scaffold, which, in turn, ensures excellent dispersibility of the obtained metal NPs in water. The antibacterial activity of the AgNPs and the photothermal action of the Au@Ag core-shell are also shown.

Electron- and Hydride-Reservoir Organometallics as Precursors of Catalytically Efficient Transition Metal Nanoparticles in Water.

Nanoparticles (NPs) are actively investigated for their efficient use in catalysis, but their means of synthesis is a key factor influencing their catalytic properties owing to surface coverage with byproducts. Here, neutral electron- and hydride-rich late transition metal organometallics are compared for the synthesis of late transition metal NPs in the presence of poly(vinylpirolidone) (PVP). In particular, the effect of electron-reservoir donors, hydride-reservoir donors, and electron-rich dimers yielding NPs electrostatically stabilized by cationic organometallics are compared in terms of NP size and catalytic efficiency. The catalytic reactions scrutinized with excellent results include 4-nitrophenol reduction to 4-aminophenol by NaBH4 for the AuNPs and PdNPs, and Suzuki-Miyaura reactions for the PdNPs. The nature of the reductant has more influence on the NP size in the case of AuNPs than PdNPs, and the best NP catalysts are obtained with hydride-reservoir complexes as reductants. The less bulky hydride donors are superior, with the complex [CoCp(ŋ4 -C5 H6 )] (Cp=ŋ5 -C5 H5 ) giving the NPs with the best catalyst efficiencies for both reactions. Protection of the NP cores by the organometallic sandwich salt is found to be the key to catalytic efficiency.

A theoretical investigation of the optical properties of metal nanoparticles in water for photo thermal conversion enhancement

Nanofluids are used in photo thermal absorbers such as direct absorption solar collectors (DASC) to improve the absorption and heat transfer. A range of experimental studies have investigated the photo thermal conversion in nanofluids based on metal nanoparticles. The photo thermal conversion efficiency depends mainly on the ability of the metal nanoparticle based nanofluid to absorb light which in turn is governed by the particle localized surface plasmon resonance (LSPR). In this article we investigate the optical properties of metal nanoparticles in water, and based on this we judge their suitability for use in water based nanofluids. We simulate the optical properties and provide an overview of the absorption, scattering and extinction properties of solid and spherical aluminum, silver, copper and gold nanoparticles suspended in water. We study nanoparticle diameters between 20 and 140nm for the wavelength range 300–1350nm (200–1250nm for aluminum). We compare our simulation results with the available experimental results presented in the literature, and find good agreement.

The ‘Nano-to-Nano’ Effect Applied to Organic Synthesis in Water

The remarkable benefits associated with the attraction of polyethylene glycol (PEG)-containing nanomicelles to metal nanoparticles in water allows for varying types of important catalysis to be done under very mild and green conditions.

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties.

Silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal–organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryotic cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.

直鎖ポリスチレンを安定化剤とする金属ナノ粒子の水中における触媒作用

直鎖ポリスチレンを安定化剤とする金属ナノ粒子の水中における触媒作用

A foolproof method for phase transfer of metal nanoparticles via centrifugation.

Our new approach using centrifugal force provides a simple and foolproof method for the phase transfer of metal nanoparticles to organic solvents. The centrifugation following functionalization by thiol-containing molecules on the metal nanoparticles in water pushed the metal nanoparticles down to the chloroform compulsorily.

Nano Scale Methods for Water Pollution Monitoring

The article deals with issues related to the textiles coated with metal nanoparticles and detection of the concentrations of released particles in water. The main risks associated with the use of metal covered textiles are detaching of metal nanoparticles from the material during use and care and thus polluting the environment, or inhaled to get in a human or animal body. Nanoparticles can be detached from the textile during washing also, thus polluting the water body and making detriment to the living beings in them. This article aims to look at equipment for nanoparticle size and concentration detection in liquids. Described the world's most popular methods (Microscopy techniques, Photon Correlation Spectroscopy, Nanoparticle Tracking Analysis) and compared to new, alternative method - Gas Discharge Visualization (GDV) electrography. Within the framework of the article analyzed the advantages and disadvantages of each method and estimated the perspective of GDV electrography for detection of metal nanoparticles in water.

Highly Stable Water‐Soluble Platinum Nanoparticles Stabilized by Hydrophilic N‐Heterocyclic Carbenes

AbstractControlling the synthesis of stable metal nanoparticles in water is a current challenge in nanochemistry. The strategy presented herein uses sulfonated N‐heterocyclic carbene (NHC) ligands to stabilize platinum nanoparticles (PtNPs) in water, under air, for an indefinite time period. The particles were prepared by thermal decomposition of a preformed molecular Pt complex containing the NHC ligand and were then purified by dialysis and characterized by TEM, high‐resolution TEM, and spectroscopic techniques. Solid‐state NMR studies showed coordination of the carbene ligands to the nanoparticle surface and allowed the determination of a 13C–195Pt coupling constant for the first time in a nanosystem (940 Hz). Additionally, in one case a novel structure was formed in which platinum(II) NHC complexes form a second coordination sphere around the nanoparticle.

Highly stable water-soluble platinum nanoparticles stabilized by hydrophilic N-heterocyclic carbenes.

Controlling the synthesis of stable metal nanoparticles in water is a current challenge in nanochemistry. The strategy presented herein uses sulfonated N-heterocyclic carbene (NHC) ligands to stabilize platinum nanoparticles (PtNPs) in water, under air, for an indefinite time period. The particles were prepared by thermal decomposition of a preformed molecular Pt complex containing the NHC ligand and were then purified by dialysis and characterized by TEM, high-resolution TEM, and spectroscopic techniques. Solid-state NMR studies showed coordination of the carbene ligands to the nanoparticle surface and allowed the determination of a (13)C-(195)Pt coupling constant for the first time in a nanosystem (940 Hz). Additionally, in one case a novel structure was formed in which platinum(II) NHC complexes form a second coordination sphere around the nanoparticle.

Concentrated synthesis of metal nanoparticles in water

Proposed mechanism of nanoparticle formation at high concentration.

Non-toxic nanoparticles from phytochemicals: preparation and biomedical application

Nanoparticles (NPs) have various applications in biomedicine and drug delivery carriers and also are widely used in cosmetics. However, the preparation of biocompatible and non-toxic nanomaterials is a very important issue as most of the starting materials are synthesized using toxic chemical reagents. This review introduces the preparation of biocompatible NPs in a range of their concentrations using phytochemicals for biomedicine and biotechnology. Phytochemicals are natural products that are extracted from plants, vegetables, and fruits. Phytochemicals serve as reducing agents and stabilizers during NP synthesis to convert metal ions to metal NPs in water. Possible applications of such nanomaterials in biomedical sciences are also described in this review.

Highly selective reduction of nitroarenes by iron(0) nanoparticles in water

Highly selective reduction of nitroarenes has been achieved using iron metal nanoparticles in water at room temperature. A wide spectrum of reducible functionalities remained inert under the reaction conditions. During the reaction a change in shape of Fe nanoparticles was observed.

ChemInform Abstract: Cyclodextrins and Their Applications in Aqueous‐Phase Metal‐Catalyzed Reactions

AbstractReview: 132 refs.

A New Route for Mass Production of Uniform Metal Nanoparticles in Water by Means of Laser Light Induced Processes

In this contribution, we report a new route for mass fabrication of metal nanoparticles with monodisperse shape and narrow size distribution in water applying exclusively physical processes. For this purpose, we have combined pulsed laser ablation with the technique of selective laser tailoring. For example, pulsed laser ablation from a gold plate in water results in a large amount of nanoparticles with radii in the range of R = 75 nm with a relatively broad size distribution of sigma = 31%. This broad size distribution has been subsequently narrowed in a single irradiation step to sigma = 20% without a significant change of the mean nanoparticle radius utilizing selective laser tailoring. The main advantage of the laser based process, besides rapid processing, is that no chemicals, which are undesired for many applications, are necessary. Hence, mass production of nanoparticles with narrow size and monodisperse shape distribution in water becomes feasible.

Noble Metal Nanoparticles Stabilized by Cyclodextrins: A Pertinent Partnership for Catalytic Applications

For economic and ecological purposes, the design of stable and reusable noble metal nanoparticles in water has become a concern over the past few years. Among the various water-soluble protective agents, cyclodextrins proved to be attractive candidates to efficiently stabilize catalytically active nanospecies in aqueous media and also to improve the mass transfer in aqueous-organic two-phase systems. Various catalytic reactions such as arenes hydrogenations, olefins reduction or cross-coupling reactions were successfully achieved with good yields and selectivities according to the relevant choice of the cyclodextrins (cavity or functionalization). Keywords: Nanoparticles, Noble metal, Cyclodextrins, Catalysis, Water

Cyclodextrins and their applications in aqueous-phase metal-catalyzed reactions

Abstract During these last years, cyclodextrins have greatly contributed to the development of catalytic processes in water. These cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units improve the mass transfer in aqueous-organic two-phase systems and are useful compounds to design new catalysts. Thus, chemically modified cyclodextrins can be used to: (1) significantly increase the rate and selectivity of reactions catalyzed by water-soluble organometallic complexes; (2) design new water-soluble ligands for aqueous organometallic catalysis; (3) stabilize catalytically active noble metal nanoparticles in water; (4) facilitate reactions catalyzed by supported metals or metallic powder in water.

Chemically Modified Cyclodextrins: An Attractive Class of Supramolecular Hosts for the Development of Aqueous Biphasic Catalytic Processes

During these last years, cyclodextrins have contributed greatly to the development of catalytic processes in water. These cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units improve the mass transfer in aqueous-organic two-phase systems and are useful compounds to design new catalysts. Thus, chemically modified cyclodextrins can be used to: (i) increase significantly the rate and selectivity of reactions catalyzed by water-soluble organometallic complexes, (ii) design new water-soluble ligands for aqueous organometallic catalysis, (iii) stabilize catalytically active noble metal nanoparticles in water and (iv) favour the dispersion and activation of the palladium on charcoal in water.

Reduction of carbon dioxide during the synthesis of metal nano-particles in water

An effort was made to synthesize “carbon-free” metal (Fe 0, Co 0, Ni 0) nano-particles via the reduction of their salts with BH 4 − in aqueous solutions. Surprisingly it was found that when the synthesis is carried out in the presence of CO 2, e.g., in aerated solutions, the CO 2 is catalytically reduced by BH 4 − on the surface of the metal particles. Carbon-free metals can be prepared by reduction under an inert atmosphere. Thus metal surfaces might have acted as catalysts for CO 2 fixation, probably via the initial formation of carbon clusters, in the reductive atmosphere in the prebiotic era.