Supported Silver Nanoparticles Research Articles

Controlled synthesis of reduced graphene oxide supported silver nanoparticles for selective and sensitive electrochemical detection of 4-nitrophenol

An electrochemical sensing platform made of a reduced graphene oxide-silver (rGO-Ag) nanocomposite was developed for the detection of 4-nitrophenol. The synthesis of the nanocomposite was monitored at different reaction times (2h, 6h, 10h and 15h) in modified Tollens’ test and characterized using UV-visible absorption spectrum, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy analyses. Completely spherical Ag nanoparticles (NPs) were found at a reaction time of 15h with an average particle size of 16nm. The nanocomposites prepared with different reaction times were used for the electrocatalytic reduction of 4-NP, and the rGO-Ag (15h) nanocomposite-modified glassy carbon (GC) electrode displayed a higher faradaic current at an overpotential of −0.5V toward 4-NP reduction. The rGO-Ag (15h) nanocomposite-modified electrode was used for the square wave voltammetric (SWV) detection of 4-NP in a 0.1M phosphate buffer (pH 7.2), and it showed a good sensitivity toward 4-NP detection even for a nanomolar concentration. The nanocomposite exhibited multi-linear ranges and 4-NP detection limit was found to be 1.2nM. The present sensor was stable and selective to 4-NP in the presence of its structural analogues such as 2-nitrophenol (2-NP), 2-aminophenol (2-AP), 3-aminophenol (3-AP), 4-aminophenol (4-AP), and 2,4-dichlorophenol (2,4-DCP). The rGO-Ag nanocomposite could be successfully applied for the determination of 4-NP in real water samples, and good recoveries were found.

Supported Silver Nanoparticle and Near-Interface Solution Dynamics in a Deep Eutectic Solvent

Type III deep eutectic solvents (DES) have attracted significant interest as both environmentally friendly and functional solvents that are, in some ways, advantageous to traditional aqueous systems. While these solvents continue to produce remarkable thin films and nanoparticle assemblies, their interactions with metallic surfaces are complex and difficult to manipulate. In this study, the near-surface region (2–600 nm) of a carbon surface is investigated immediately following silver nanoparticle nucleation and growth. This is accomplished, in situ, using a novel grazing transmission small-angle X-ray scattering approach with simultaneous voltammetry and electrochemical impedance spectroscopy. With this physical and electrochemical approach, the time evolution of three distinct surface interaction phenomena is observed: aggregation and coalescence of Ag nanoparticles, multilayer perturbations induced by nonaggregated Ag nanoparticles, and a stepwise transport of dissolved Ag species from the carbon surface. The multilayer perturbations contain charge-separated regions of positively charged choline-ethylene and negatively charged Ag and Cl species. Both aggregation-coalescence and the stepwise decrease in Ag precursor near the surface are observed to be very slow (∼2 h) processes, as both ion and particle transport are significantly impeded in a DES as compared to aqueous electrolytes. Altogether, this study shows how the unique chemistry of the DES changes near the surface and in the presence of nanoparticles that adsorb the constituent species.

Glycerol oxidehydration to pyruvaldehyde over silver-based catalysts for improved lactic acid production

Supported silver nanoparticles are identified as the optimal catalyst to convert glycerol into pyruvaldehyde. The use of this intermediate instead of dihydroxyacetone enables an alternative greener process for the preparation of lactic acid.

Supercritical carbon dioxide anchored highly dispersed silver nanoparticles on 4A-zeolite and selective oxidation of styrene performance

We developed a facile and new method for the production of a 4A-zeolite supported silver nanoparticle (Ag NP) composite catalyst using supercritical carbon dioxide (scCO2). The small (3–6 nm) and highly dispersed silver nanoparticles were formed on the 4A-zeolite with the assistance of scCO2 and hydrogen reduction. The anchored Ag NPs are smaller in size and more uniform in distribution on the 4A-zeolite, and favor a wide range of physical and chemical properties. In order to test the properties of the synthesized composite catalyst, the selective oxidation of styrene was introduced into the experiment. The composite catalyst synthesized by this new method exhibited excellent catalytic properties in the selective oxidation reaction of styrene compared with previous reports. Furthermore, two kinds of important chemical product, styrene oxide (SO) and benzaldehyde (BZ), could be controlled selectively by changing the oxidants and solvents used.

Room-temperature synthesis of silica supported silver nanoparticles in basic ethanol solution and their antibacterial activity

A facile and environmentally friendly route was developed to synthesize silica supported silver nanoparticles through the reduction of Ag+ ions in basic ethanol solution without adding any other reducing agents or surfactants at room temperature.

Green synthesis of graphene quantum dots and silver nanoparticles compounds with excellent surface enhanced Raman scattering performance

Here, silica (SiO2) supported silver nano-particles (Ag NPs) and graphene quantum dots (GQDs) compounds were designed and synthesized via a “green” photochemical approach and an electrophoresis deposition technique in order to provide a highly active surface-enhanced Raman scattering (SERS) substrate. In this approach, the electrochemically prepared aqueous solution of GQDs was used as a solvent and a reducing agent to synthesize in-situ Ag-GQDs compounds under Ultraviolet (UV) irradiation. These compounds were collected on a SiO2 supported Si substrate through the electrophoresis deposition technique. Benefiting from their proper size (1–4 nm) and distribution in the spatial gaps between adjacent Ag NPs, GQDs could act as “hot spot” sites for lighting up the Raman scattering signals. Together with the enhanced adsorption of Rhodamine 6G (R6G) molecules through π-π stacking, the electrostatic interactions from GQDs, and the enlarged specific surface area provided by the SiO2 template, the as-prepared substrate exhibited a strong SERS signal with excellent reproducibility. The detection limit of R6G was pushed to 8.0 × 10−14 M. We hope our work provides a time-saving and facile approach for the design and creation of ultrasensitive SERS substrate for trace species detection.

Reactions of methyl radicals with silica supported silver nanoparticles in aqueous solutions

Silica supported silver nanoparticles (Ag°–SiO2–NCs, NCs=nanocomposites) suspended in aqueous solutions are efficient catalysts for the dimerization of methyl radicals to produce ethane, while bare silica is quite inert towards the interaction with methyl radicals. In the presence of small amounts of ethanol adsorbed on the SiO2 surface, the reaction path with methyl radicals is changed and methane is formed as the major product.

Dipping into a drink: Basil-seed supported silver nanoparticles as surface-enhanced Raman scattering substrates for toxic molecule detection

High-density plasmonic Ag nanoparticles (Ag-NPs) have been synthesized on a three-dimensional framework of natural basil seeds as the inexpensive substrates for surface-enhanced Raman scattering (SERS). The Ag-NPs decorated basil seeds (denoted as Ag-NPs@basil-seeds) are dipped into the analyte solution for rapid detection of methyl parathion in orange juice. Alternatively, they are incorporated into a microfluidic chip for online measurement of melamine in milk. The porous basil seeds can absorb trace melamine into the micro-cavity in the seeds, which load the melamine molecules into the gap where high-density “hot spots” appear under laser excitation. Hence the Ag-NPs@basil-seeds not only separate and pre-concentrate the trace analyte but also expose the analyte into the strong plasmonic field. This unique feature can eliminate the pre-treatment of analyte prior to SERS detection, and improve the sensitivity of the sensor.

A highly robust and reusable polyimide-supported nanosilver catalyst for the reduction of 4-nitrophenol

Abstract

Skin wound healing with chitosan thin films containing supported silver nanospheres

Dermal wound healing involves complex histo-molecular events aimed to repair the discontinuity of the epithelium. Employing nanometric silver particles provides an efficient antimicrobial effect for several dermal infections. The aim is to elucidate imminent advantages of silver nanoparticles, such as the possibility of modulating the epithelial cell repair process. Through the nanostructural implementation of chitosan thin films supporting silver nanoparticles, it was feasible to evaluate in vivo the efficacy and evolution of dermal recuperation after surgical damage. The characterization of chitosan silver nanoparticle films was performed by UV–visible spectra and Fourier transform infrared spectroscopy, X-ray diffraction, and high-resolution electron microscopy. An important dermal healing was accomplished in animals that were treated with chitosan films supporting silver nanoparticles, as confirmed by a histopathological analysis of the skin after 12 days of treatment. The developed chitosan thin film supporting an optimized amount of silver nanoparticles could be employed to treat diseases related to wound healing.

Bacterial cellulose membrane supported three-dimensionally dispersed silver nanoparticles used as membrane electrode for oxygen reduction reaction in phosphate buffered saline

A novel bacterial cellulose (BC) membrane supported silver nanoparticles (AgNPs) was synthesized with a facile in situ growth method. The physicochemical properties of AgNP/BC were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results demonstrate that AgNPs with diameters of 10–20nm were anchored throughout the three-dimensional network of BC membrane. The as-prepared AgNP/BC membrane was used as cathodic electrode to investigate its catalytic activity to oxygen reduction reaction (ORR) in phosphate buffered saline (PBS) for the first time. As a result, the maximum current density obtained with AgNP/BC was −3.94mAcm−2, which was higher than Ag electrode and AgNP. Besides, the maximum current density of AgNP/BC only decreased 4.3% in electrolyte with 10mmolL−1 glucose. Such AgNP/BC membrane with advantages including biocompatibility, facile synthesis, high catalytic activity and good glucose tolerance could be valuable to ORR in implanted glucose fuel cells.

ChemInform Abstract: Catalysis by Mont K‐10 Supported Silver Nanoparticles: A Rapid and Green Protocol for the Efficient ipso‐Hydroxylation of Arylboronic Acids.

Abstract A mild and efficient methodology has been developed for the ipso-hydroxylation of arylboronic acids using montmorillonite K-10 supported silver nanoparticles (AgNPs) as catalyst and aqueous H2O2 as oxidant. The reactions were performed at room temperature within short reaction time under solvent- and base-free conditions. This catalyst shows good reusability.

Enhanced photochemistry of ethyl chloride on Ag nanoparticles.

Enhanced photodecomposition of ethyl chloride (EC) adsorbed on SiO2/Si (100) supported silver nanoparticles (Ag NPs) under ultrahigh vacuum (UHV) conditions has been studied in order to assess the potential contribution of plasmonic effects. The cross section for photodecomposition of EC and overall photoyield were found to increase with increasing photon energy regardless of the plasmon resonant wavelength and with Ag coverage without any noticeable particle size effect. The influence of EC-Ag NPs separation distance on the rate of EC decomposition was studied in order to examine potential local electric field influence on the photodissociation process. Long (∼5 nm) photoactivity decay distance has been observed which excludes local surface plasmon dominance in the photodecomposition event. These findings suggest that the alignment of excited electron energy and adsorbate affinity levels is central for efficient photochemical reactions, whereas short-range electric field enhancement by plasmon excitation on top and at the immediate vicinity of silver nanoparticles does not have any measurable effect.

Catalysis by mont K-10 supported silver nanoparticles: a rapid and green protocol for the efficient ipso-hydroxylation of arylboronic acids

A mild and efficient methodology has been developed for the ipso-hydroxylation of arylboronic acids using montmorillonite K-10 supported silver nanoparticles (AgNPs) as catalyst and aqueous H2O2 as oxidant. The reactions were performed at room temperature within short reaction time under solvent- and base-free conditions. This catalyst shows good reusability.

Optimizing the design and synthesis of supported silver nanoparticles for low cost water disinfection.

Silver nanoparticles (AgNPs) were successfully synthesized and impregnated on silica using chemical reduction methods. XPS and Ag K-edge XANES analysis revealed that the impregnation of AgNPs onto silica using a chitosan + sodium borohydride (NaBH4) method results in higher silver loading and Ag(0)/Ag(I) ratio compared to that obtained using NH3 + NaBH4/glucose methods. The effects of the dosage of chitosan on silver loading, Ag(I) release, and bactericidal activities of AgNP-impregnated silica were investigated, with results showing that, at high dosages of chitosan, Ag(I) released from AgNP-impregnated silica plays an important role in disinfection, while AgNP-mediated bactericidal action dominates at low dosages of chitosan. To further decrease the manufacturing cost, partially oxidized "black rice husk ash" containing substantial residual carbon was applied as AgNP support and found to lead to a greater degree of silver impregnation and to exhibit a longer disinfection lifetime than that of lower carbon content silica supports. On the basis of these findings, it is clear that considerable scope exists for careful optimization in the design and production of AgNP-based bactericidal materials for water treatment purposes.

Chitosan films containing mesoporous SBA-15 supported silver nanoparticles for wound dressing.

Chitosan films containing mesoporous SBA-15 supported silver nanoparticles (AgNPs) were prepared to be applied as a potential wound dressing material. First SBA-15-silver nanoparticle (SBA-15-Ag) composite materials were prepared by a controlled annealing process without the use of organic solvents and reagents. The SBA-15-AgNPs were characterized in detail by X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy which evidenced the presence of uniformly distributed silver nanostructures inside the silicate pores. UV-vis spectra of the sample showed a band at 430 nm characteristic of the surface plasmon resonance of silver nanoparticles with a diameter below 10 nm and X-ray photoemission spectra confirmed the formation of metal-nanoparticles on the silicate template. Then SBA-15-Ag was used to prepare chitosan films which were characterized in detail. In particular, they showed good hydration properties, water vapor transmission rate and mechanical properties. After hydration films exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria.

Twin Polymerization: A Unique and Efficient Tool for Supporting Silver Nanoparticles on Highly Porous Carbon and Silica

Invited for the cover of this issue is the group of Heinrich Lang at the University of Chemnitz, Germany. The cover image shows highly porous materials of type Ag@C (red) and Ag@SiO2 (blue), obtained by twin polymerization from the appropriate silver(I) carboxylate as silver source and 2,2'-spirobi[4H-1,3,2-benzodioxasiline] as the specific twin monomer.

Twin Polymerization: A Unique and Efficient Tool for Supporting Silver Nanoparticles on Highly Porous Carbon and Silica (Eur. J. Inorg. Chem. 20/2014)

Twin Polymerization: A Unique and Efficient Tool for Supporting Silver Nanoparticles on Highly Porous Carbon and Silica (Eur. J. Inorg. Chem. 20/2014)

Twin Polymerization: A Unique and Efficient Tool for Supporting Silver Nanoparticles on Highly Porous Carbon and Silica

AbstractA convenient approach for the straightforward synthesis of highly dispersed silver nanoparticles (below 5 nm) in a carbon or silicon dioxide matrix through twin polymerization is reported. The obtained mainly microporous carbon (type I isotherm) and mesoporous silica materials (type IV isotherm) exhibit a rather high surface area (carbon = 1034 m2 g–1, SiO2 = 666 m2 g–1).

Silver nanoparticles: synthesis and application in mineralization of pesticides using membrane support

Pesticides are deliberately used for controlling the pests in agriculture and public health, due to which, a part of it is present in the drinking water. Due to their widespread use, they are present in both surface and ground water. Most of the pesticides are resistant to biodegradation and are found to be carcinogenic in nature even at trace levels. Conventional methods of pesticide removal are disadvantageous due to their inherent time consumption or expensiveness. Nanoparticles alleviate both of these drawbacks and hence, they can be effectively utilized for the mineralization of pesticides. To prevent the presence of nanoparticles in the purified water after mineralization of pesticides, they need to be incorporated on a support. In earlier studies, researchers employed activated carbon and alumina as support for silver nanoparticles in pesticide mineralization. However, not many studies have been carried out on polymeric membranes as support for silver nanoparticles in the mineralization of pesticides (chlorpyrifos and malathion). With this in view, a detailed study has been carried out to estimate the mineralization potential of silver nanoparticles (synthesized using glucose) supported on cellulose acetate membrane. It is observed that the silver nanoparticles can effectively mineralize the pesticides, and the concentration of nanoparticles enhances the rate of mineralization.