Seed-Mediated Synthesis of Gold Nanorods: Role of …

Gold nanoparticles have attracted much interest because of their tunable Surface Plasmon Resonance (SPR) peaks, leading to important applications in the fields of chemistry, biology and materials sciences,,,,,,. As is well known, the SPR properties of metallic nanoparticles (NPs) can be calculated by solving Maxwell's equations in terms of theory, and exact solutions to Maxwell's equations are known only for spheres, concentric spherical shells, spheroids, and infinite cylinders. Specifically, Mie theory is the exact analytical solution of Maxwell's equations for a nanoparticle with defined shape. However, it is difficult to synthesize monodispersed noble metallic nanoparticles in a wide range of sizes and controlled shapes on a large scale, and their observed optical absorption property can not obey Mie theory prediction accurately.

Nanocomposites: synthesis, structure, properties and …

This review is concerned with the synthesis of metallic nanoparticles using plant extracts

Synthesis of Monodisperse Spherical Nanocrystals - …

Highly monodisperse sodium citrate-coated spherical silver nanoparticles (Ag NPs) with controlled sizes ranging from 10 to 200 nm have been synthesized by following a kinetically controlled seeded-growth approach via the reduction of silver nitrate by the combination of two chemical reducing agents: sodium citrate and tannic acid. The use of traces of tannic acid is fundamental in the synthesis of silver seeds, with an unprecedented (nanometric resolution) narrow size distribution that becomes even narrower, by size focusing, during the growth process. The homogeneous growth of Ag seeds is kinetically controlled by adjusting reaction parameters: concentrations of reducing agents, temperature, silver precursor to seed ratio, and pH. This method produces long-term stable aqueous colloidal dispersions of Ag NPs with narrow size distributions, relatively high concentrations (up to 6 × 1012 NPs/mL), and, more important, readily accessible surfaces. This was proved by studying the catalytic properties of as-synthesized Ag NPs using the reduction of Rhodamine B (RhB) by sodium borohydride as a model reaction system. As a result, we show the ability of citrate-stabilized Ag NPs to act as very efficient catalysts for the degradation of RhB while the coating with a polyvinylpyrrolidone (PVP) layer dramatically decreased the reaction rate.

A Facile pH Controlled Citrate-Based Reduction Method …

We develop a facile and effective strategy to prepare monodispersed Au spherical nanoparticles by two steps. Large-scale monocrystalline Au nanooctahedra with uniform size were synthesized by a polyol-route and subsequently Au nanoparticles were transformed from octahedron to spherical shape in a liquid under ambient atmosphere by non-focused laser irradiation in very short time. High monodipersed, ultra-smooth gold nanospheres can be obtained by simply optimizing the laser fluence and irradiation time. Photothermal melting-evaporation model was employed to get a better understanding of the morphology transformation for the system of nanosecond pulsed-laser excitation. These Au nanoparticles were fabricated into periodic monolayer arrays by self-assembly utilizing their high monodispersity and perfect spherical shape. Importantly, such Au nanospheres arrays demonstrated very good SERS enhancement related to their periodic structure due to existence of many SERS hot spots between neighboring Au nanospheres caused by the electromagnetic coupling in an array. These gold nanospheres and their self-assembled arrays possess distinct physical and chemical properties. It will make them as an excellent and promising candidate for applying in sensing and spectroscopic enhancement, catalysis, energy, and biology.

We present a rapid, simple, and efficient strategy for high yield synthesis of monodisperse, quasi-spherical Au nanocrystals (Au …
15/03/2017 · Transition metal ion-assisted synthesis of monodisperse, quasi-spherical gold nanocrystals via citrate reduction Zhang, P, …

Effect of Latent Heat in Boiling Water on the Synthesis …

Herein, we develop a facile and effective strategy to achieve monodispersed Au spherical nanoparticles. Firstly, large-scale monocrystalline Au octahedral nanoparticle with uniform size are synthesized by a straightforward polyol-route. The size dimensions of Au octahedra can be manipulated from tens to hundreds of nanometers. Secondly, non-focused laser irradiation technology is applied to transform Au particles from octahedron to spherical shape in a liquid under ambient atmosphere in short time. Ultra-smooth gold nanospheres with high monodispersity can be obtained by simply optimizing the laser fluence and irradiation time. Moreover, the morphology transformation of Au octahedral nanoparticle under the nanosecond laser irradiation strongly depends on a photothermal melting-evaporation process. Further, these Au nanoparticles can be fabricated into ordered arrays by self-assembly technique due to their high monodispersity and perfect spherical shape. Importantly, such Au nanospheres array shows a significantly SERS performance associated with their periodic structure due to existence of many SERS hot spots between neighboring Au nanospheres in an array. These gold nanospheres and their self-assembled arrays possess distinct physical and chemical properties that will make them as an excellent and promising candidate for applying in sensing and spectroscopic enhancement, catalysis, energy, and biology,,.

Monodispersity control in the synthesis of monometallic and bimetallic quasi-spherical gold and silver nanoparticles

cobalt with spherical morphologies ..

The size and morphology of the nanoparticles were determined by transmission electron microscopy (TEM), differential centrifugal sedimentation (DCS) and dynamic light scattering (DLS). TEM showed that the nanoparticles were nearly monodisperse, quasi-spherical, polycrystalline, and had a uniform diameter of 6 to 7 nm. Only nanoparticles with the highest silver content (Ag/Au 90:10) had a slightly larger diameter (≈11 nm). This trend was maintained by pure silver particles which showed a considerably larger diameter when synthesized with the same reaction parameters (≈30 nm). The TEM images in show a representative series of Ag/Au 10:90, 30:70, and 90:10 nanoparticles with PVP stabilization.

We propose a novel methodology to synthesize monodisperse gold–silver alloy nanoparticles (NPs) with fine control of size and composition. The synthesis is …

Ag NPs were in-site synthesized through microemulsion method by ..

shows the corresponding absorption spectra of Au NPs in DI water irradiated for 240 s at different laser fluences. It indicates that there is a remarkable blue shift in their localized surface plasmon resonances (LSPR) peak with increase of laser fluence due to shape changes of Au nanoparticle (). When Au nanooctahedra is irradiated by laser at 1.76 mJ cm−2 for 240 s, the LSPR peak shifts from 578 to 565 nm, which can be attributed to the slight melting of the Au octahedra corner, where the LSPR effect is extremely sensitive. While increasing fluence to 2.87 mJ cm−2, the absorption peak containing a shoulder peak appears. This curve can be divided into two peaks, centered at 540 and 570 nm, which correspond to the LSPR peaks of Au spherical and quasi-octahedral structures, respectively (). When laser fluence increased to 3.84 mJ cm−2, the LSPR peak is shifted into 542 nm because of the complete formation of Au nanospheres. While increasing into a high fluence of 5.50 mJ cm−2, the LSPR peak further shifts to 538 nm due to the size reduction of Au nanospheres. In short, a gentle laser irradiation at 3.84 mJ cm−2 can induce completely shape changes from octahedra to sphere and even size reduction, but it is not feasible to obtain a highly monodispersed spherical nanoparticles only by controlling the laser fluence.