Ag Nanoplates Research Articles

Green synthesis of silver nanoparticles by chemical reduction with hyaluronan

The paper reported a facile and green synthesis of silver nanoparticles by using hyaluronan (HA) as a reducing agent and soft template. The effect of reaction conditions on the Ag nanoparticle formation was investigated using UV–vis spectrophotometer, field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The application of Ag nanoparticles in surface enhanced Raman scattering (SERS) of HA was also evaluated. The results showed that the high pH value, temperature and molar ratio of HA to AgNO3 could accelerate the reduction rate of Ag+ and affect the Ag nanoparticle size. The Ag nanoplates could be fabricated with a low molar ratio of HA to AgNO3 by aging, which may be due to the selective adsorption and desorption of HA on the different crystallographic planes of Ag nanoparticles. The enhancement of Raman scattering effect was greatly dependent on the size and morphology of Ag nanoparticles.

Sculpturing Effect of Sodium Thiosulfate in Shape Transformation of Silver Nanoparticles from Triangular Nanoprisms to Hexagonal Nanoplates

Sodium thiosulphate (Na2S2O3) solution was used to etch silver nanoparticles (NPs) and transform them from triangular nanoprisms to hexagonal nanoplates. UV-Vis spectroscopy and transmission electron microscopy were used to monitor the evolution of the hexagonal Ag nanoplates. S2O3(2-) etched the corners of the triangular Ag nanoprisms, and the Ag atoms that were removed aggregated into small clusters. The facet-selective etching effect of S2O3(2-) can be mainly attributed to the surface energy difference of each face of the nanoplate. The mechanism of S2O3(2-) etching also involves formation of Ag2S2O3 on the nanoprisms vertices, which is followed by its hydrolysis and subsequent dissociation of Ag atoms to form stable Ag2S. The hexagonal Ag nanoplates showed higher surface-enhanced Raman scattering activity than the original nanoprisms.

Silver nanoplates as inkjet ink particles for metallization at a low baking temperature of 100 °C

Conductive patterns on a flexible polyimide film using Ag nanoplate ink of 10 wt% solid content were successfully fabricated by inkjet printing and baking at a low temperature of 100 °C. Sintering on these printed nanoplates at a low temperature (100 °C) led to the formation of connections between nanoplates. A four-point probe measurement indicated that the resistivity of the line obtained by printing nanoplates is 26.3 μΩ-cm and this is lower than that of the line obtained by printing spherical nanoparticles, 4.3 × 10 5 μΩ-cm.

Room-temperature synthesis of flowerlike Ag nanostructures consisting of single crystalline Ag nanoplates

We demonstrate a simple wet-chemical route for the high-yield synthesis of flowerlike silver nanostructures consisting of single crystalline Ag nanoplates by mixing AgNO 3 and p-phenylenediamine (PPD) in the presence of polyvinylpyrrolidone (PVP) at room temperature. PPD serves both as a reducing agent, and as an architecture soft template with PVP to the formation of such Ag nanostructures. It is found that the presence of PVP has a significant effect on the formation and growth of these novel nanostructures. The flowerlike silver nanostructures could serve as highly sensitive and reproductive surface-enhanced Raman scattering (SERS) substrates for chemical and biological detection.

Graphene buffered galvanic synthesis of graphene–metal hybrids

We report an in situ synthesis of graphene–metal hybrids using graphene as the buffer layer by a substrate-induced galvanic reaction. Ag nanoplates are obtained with the template effect of graphene, and their morphologies are tailored by light mediation. Our result suggests that defect sites or open edges of graphene favor binding with Ag atoms. The graphene–Ag hybrids have been used as Raman enhanced substrates for dye detection. The facile method for synthesis of graphene–metal hybrids opens up opportunities for the future development of optical, electronic and catalytic materials based on graphene and metals.

Orientation-selective removal of upright Ag nanoplates from a TiO2 film

Upright Ag nanoplates on a nanoparticulate TiO(2) film are oriented on the basis of plasmon-induced charge separation. Polarized visible light removes nanoplates oriented perpendicularly to polarization via excitation of in-plane transverse mode. Polarized near-infrared light removes nanoplates in parallel geometry via excitation of in-plane longitudinal mode.

Photoelectrochemical and Optical Behavior of Single Upright Ag Nanoplates on a TiO2 Film

Changes in morphology and optical properties of single Ag nanoplates on a nanoparticulate TiO2 film were studied by means of combined atomic force microscopy and optical dark-field microscopy with ...

Selective synthesis of hexagonal Ag nanoplates in a solution-phase chemical reduction process

Two-dimensional (2-D) Ag nanoplates have surface plasmon resonances which can be tuned from the visible to the near-IR by varying the size and morphology of the nanoplates. Due to their anisotropic structures and different surface energy distributions, Ag nanoplates—especially triangular ones—are kinetically stable and can transform into other nanostructures. Taking advantage of the synergetic effects of HNO3 and Cl− in the reduction solution, uniform Ag hexagonal nanoplates (HNPs) have been captured during the transformation of Ag triangular nanoplates (TNPs). The dimensions of the Ag HNPs can be controlled by changing the concentrations of reagents in the reaction or/and reduction solutions. Resonance absorption spectra of the obtained Ag HNPs indicated that their in-plane resonance peaks could be tuned from the visible to the near-IR region, showing their potential applications in medical diagnosis.

Seeded Growth of Uniform Ag Nanoplates with High Aspect Ratio and Widely Tunable Surface Plasmon Bands

Silver nanoplates with an extremely high aspect ratio (up to over 400) and a widely tunable surface plasmon resonance (SPR) band have been successfully synthesized by combining the concepts of selective ligand adhesion and seeded growth. Citrate ligands are used as the sole surfactant to effectively block overgrowth on the basal {111} facets and only allow growth in the lateral direction. By slowing down the reaction rate using Ag-citrate complex as precursor, the thin nature of Ag nanoplates is maintained with the edge length grown up to 4 μm, which ensures the high aspect ratio and the widely tunable SPR band. We also observe a size distribution focusing effect that helps to produce uniform nanoplates as well as narrow SPR bands over a wide range, which is important in many practical applications.

Facile synthesis, stabilization, and anti-bacterial performance of discrete Ag nanoparticles using Medicago sativa seed exudates

The biogenic synthesis of metal nanomaterials offers an environmentally benign alternative to the traditional chemical synthesis routes. Colloidal silver (Ag) nanoparticles were synthesized by reacting aqueous AgNO(3) with Medicago sativa seed exudates under non-photomediated conditions. Upon contact, rapid reduction of Ag(+) ions was observed in <1 min with Ag nanoparticle formation reaching 90% completion in <50 min. Effect of Ag concentration, quantity of exudate and pH on the particle size and shape were investigated. At [Ag(+)]=0.01 M and 30°C, largely spherical nanoparticles with diameters in the range of 5-51 nm were generated, while flower-like particle clusters (mean size=104 nm) were observed on treatment at higher Ag concentrations. Pre-dilution of the exudate induced the formation of single-crystalline Ag nanoplates, forming hexagonal particles and nanotriangles with edge lengths of 86-108 nm, while pH adjustment to 11 resulted in monodisperse Ag nanoparticles with an average size of 12 nm. Repeated centrifugation and redispersion enhanced the percentage of nanoplates from 10% to 75% in solution. The kinetics of nanoparticle formation were monitored using ultraviolet-visible spectroscopy and the Ag products were characterized using transmission electron microscopy, selected-area electron diffraction, scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy. X-ray photoelectron spectroscopy was used to investigate the elements and chemical environment in the top layers of the as-synthesized Ag nanoparticles, while the metabolites in the exudate were analyzed using gas chromatography-mass spectroscopy. To our knowledge, this is the first account of M. sativa seed exudate assisted synthesis and stabilization of biogenic Ag nanoparticles; the nanoplates are notably smaller and better faceted compared with those synthesized by vascular plant extracts previously reported. Stabilized films of exudate synthesized Ag nanoparticles were effective anti-bacterial agents.

Silver triangular nanoplates as electrocatalyst for oxygen reduction reaction

Triangular Ag nanoplates with large and small sizes were successfully synthesized for oxygen electroreduction. From the results of the x-ray diffraction analysis, it was concluded that Ag nanoplates of small size are the crystals that are essentially composed of (111) planes. The data provided by electrochemical measurement and the Koutecky–Levich equation showed that the electron numbers involved in the oxygen reduction reaction of small and large Ag nanoplates are 3.27 and 3.16, respectively. Small Ag nanoplates exhibit maximum activity towards the oxygen reduction reaction.

Graphical Abstract: Eur. J. Inorg. Chem. 27/2010

AbstractThe cover picture a selection of cutting‐edge areas of research on one‐ and two‐dimensional inorganic nanomaterials. I. Pastoriza‐Santos et al. (p. 4288 ff) discuss high‐yield methods of synthesis of both Au and Ag nanoplates and their optical properties, as represented by the EELS Intensity distribution map of one silver triangle (middle), related to applications in surface‐enhanced Raman scattering (SERS). The magnetic Pd and Pt nanoparticles covered with alkanethiol groups (top left) are the topic of the Microreview by A. Miyazaki, T. Enoki, et al. (p. 4279 ff), who also report on charge transfer at the metal–organic interface. In their Microreview R. Tenne et al. (p. 4233 ff) demonstrate how the encapsulation of one‐dimensional crystals in inorganic nanotubes lead to filled inorganic nanotube composites (two views of which are in the bottom left and right corners of the cover picture). The double‐walled carbon nanotubes (top right) with optical and chemical activity, which can be applied in preparing multifunctional hybrid materials, are covered in the Short Communication by Y. A. Kim et al. (p. 4305 ff). Thanks are due to all these research groups for contributing their designs to make up this composite cover picture.

Synthetic Routes and Plasmonic Properties of Noble Metal Nanoplates Classes of Nanomagnets Created from Alkanethiol‐Coated Pt or Pd Nanoparticles and Their Alloys with Co One‐ and Two‐Dimensional Inorganic Crystals inside Inorganic Nanotubes Covalent Attachment of Aromatic Diisocyanate to the Sidewalls of Single‐ and Double‐Walled Carbon Nanotubes (Eur. J. Inorg. Chem. 27/2010)

AbstractThe cover picture a selection of cutting‐edge areas of research on one‐ and two‐dimensional inorganic nanomaterials. I. Pastoriza‐Santos et al. (p. 4288 ff) discuss high‐yield methods of synthesis of both Au and Ag nanoplates and their optical properties, as represented by the EELS intensity distribution map of one silver triangle (middle), related to applications in surface‐enhanced Raman scattering (SERS). The magnetic Pd and Pt nanoparticles covered with alkanethiol groups (top left) are the topic of the Microreview by A. Miyazaki, T. Enoki, et al. (p. 4279 ff), who also report on charge transfer at the metal–organic interface. In their Microreview R. Tenne et al. (p. 4233 ff) demonstrate how the encapsulation of one‐dimensional crystals in inorganic nanotubes lead to filled inorganic nanotube composites (two views of which are in the bottom left and right corners of the cover picture). The double‐walled carbon nanotubes (top right) with optical and chemical activity, which can be applied in preparing multifunctional hybrid materials, are covered in the Short Communication by Y. A. Kim et al. (p. 4305 ff). Thanks are due to all these research groups for contributing their designs to make up this composite cover picture.

Nanophase Evolution at Semiconductor/Electrolyte Interface in Situ Probed by Time-Resolved High-Energy Synchrotron X-ray Diffraction

Real-time evolution of nanoparticles grown at the semiconductor/electrolyte interface formed between a single crystalline n-type GaAs wafer and an aqueous solution of AgNO(3) has been studied by using high-energy synchrotron X-ray diffraction. The results reveal the distinct nucleation and growth steps involved in the growth of anisotropic Ag nanoplates on the surface of the GaAs wafer. For the first time, a quick transit stage is observed to be responsible for the structural transformation of the nuclei to form structurally stable seeds that are critical for guiding their anisotropic growth into nanoplates. Reaction between a GaAs wafer and AgNO(3) solution at room temperature primarily produces Ag nanoplates on the surface of the GaAs wafer in the dark and at room temperature. In contrast, X-ray irradiation can induce charge separation in the GaAs wafer to drive the growth of nanoparticles made of silver oxy salt (Ag(7)NO(11)) and silver arsenate (Ag(3)AsO(4)) at the semiconductor/electrolyte interface if the GaAs wafer is illuminated by the X-ray and reaction time is long enough.

Liquid–liquid interface assisted synthesis of size- and thickness-controlled Ag nanoplates

Here we proposed a synthetic method of high-purity Ag nanoplates by the reduction of aqueous Ag + ions at the aqueous–organic interface with the reductant ferrocene. We demonstrated that the as-prepared Ag nanoplates can be widely tunable from 600 nm to 7 μm in size and from 10 to 35 nm in thickness, simply by adjusting the component of organic phase. To our knowledge, there are few methods to tailor the size and the thickness of metal nanoplates in such a large range although many efforts have been made aiming to realize it. Our proposed synthetic strategy is rapid, template-free, seed-less, and high-yield, and could be applied to synthesize analogous two-dimensional nanostructures of other noble metals, such as Pt, Au, and Pd.

Synthesis of Ag Nanoplates on GaAs Wafers: Evidence for Growth Mechanism

Direct synthesis of Ag nanoplates on GaAs wafers has been developed in our group through a simple solution/solid interfacial reaction (SSIR) strategy, in which aqueous solutions of pure AgNO3 react with the GaAs wafers at room temperature [J. Phys. Chem. C 2009, 113, 6061; 2008, 112, 8928; Chem. Mater. 2007, 19, 5845]. However, a number of questions are still not clear yet regarding the roles of different possible pathways for reducing Ag+ ions in the growth of Ag nanoplates. In this article, we try to answer these remaining questions by specifically designing experiments and extracting direct evidence from systematic characterizations of different samples. It is conclusive that growth of high-quality Ag nanoplates on GaAs wafers is ascribed to the good separation between nucleation and growth steps, which are driven by two different reduction pathways. At the nucleation step, fast reduction of Ag+ ions with a high concentration of surface electrons is crucial for the formation of Ag nuclei with multiple ...

Porous Ag–Pd triangle nanoplates with tunable alloy ratio for catalyzing electroless copper deposition

Porous triangular Ag–Pd nanoplates of various bimetallic ratios were prepared by a galvanic displacement reaction in which Pd(OAc) 2 reacted with Ag nanoplates. In order to reduce the interaction of free hexadecyltrimethylammonium bromide (CTAB) with the synthesized Ag–Pd nanoplates during this reaction, Ag nanoplate/CTAB solution was precipitated by high-speed centrifugation before synthesizing the porous bimetallic nanotemplates. The kinetics of electroless copper deposition (ECD) catalyzed by these bimetallic nanoplates are analyzed by using a quartz crystal microbalance (QCM). The results reveal that Ag 18Pd 1 nanoplates show better catalytic activity than Ag 18Pd 1.5 and Ag 18Pd 2 nanoplates. Further, the catalytic activity of the porous nanoplates in the ECD bath can be controlled by varying their alloy ratios.

Synthesis of Out‐of‐Substrate Au–Ag Nanoplates with Enhanced Stability for Catalysis

Trägerfixierte Nanoplättchen bestehend aus einer Gold-Silber-Legierung (siehe Bild) wurden durch Abscheidung von Silber-Nanoplättchen auf einem Galliumarsenid-Wafer und anschließendes Überwachsen und Legieren mit der Goldkomponente synthetisiert. Die hohe spezifische Oberfläche der Nanoplättchen sorgt für eine hohe katalytische Effizienz dieses Materials.

Synthesis of Out‐of‐Substrate Au–Ag Nanoplates with Enhanced Stability for Catalysis

Gold-silver alloy nanoplates with out-of-substrate orientation are synthesized on large-area supports by growth of silver nanoplates on gallium arsenide wafers followed by an overgrowth and alloying process. The surfaces of the nanoplates are highly exposed to the surrounding environment, thus increasing their catalytic efficiency.

Fabrication of Hierarchical Nanostructure of Silver via a Surfactant-Free Mixed Solvents Route

The dendritic Ag nanostructure with ordered branches and a “clean” surface has been successfully prepared via a facile surfactant-free and acetone-based mixed solvents route at room temperature. Experiments and structural characterizations reveal that the dendritic Ag nanostructure is evolved from the initially generated triangular nanoplates by the reaction of AgNO3 with l-ascorbic acid to the dendrites through both the Ostwald ripening and the oriented attachment growth processes. The acetone plays the key role in controlling the nucleation, growth, conversion, and assembly of the Ag nanoparticles. In the absence of acetone, only the polyhedral particles can be obtained. The yield of the dendrites is dependent on the volume ratio of acetone to water. The present work provides an example for the synthesis of a novel metal nanostructure by simply adjusting the solvent components, which is important for the qualitative understanding of the solvent effect on the morphology of nanostructures and the controllable synthesis of desired nanostructures. The dendritic Ag nanostructure possesses surface-enhanced Raman scattering (SERS) performance similar to that from triangular Ag nanoplates, and they both show much better SERS enhancement ability than that of polyhedral Ag particles which might be relative to their different geometric shapes and microstructures. It is expected that the dendritic Ag nanostructure may find potential applications such as in catalysis, molecular probe, and biological sensing.