One-pot synthesis of silver nanoplates and charge-transfer complex nanofibers

We describe a facile one-pot process to synthesize Ag nanoplates by reducing silver nitrate with 3,3',5,5'-tetramethylbenzidine (TMB) at room temperature. The silver nanoplates were highly oriented single crystals with (111) planes as the basal planes. TMB can be readily oxidized to charge-transfer (CT) complex between TMB, as a donor, and (TMB)(2+), as an acceptor. The pi-pi interaction of the neutral amine (TMB) and diiminium structure (dication, TMB2+) result in the formation of one-dimensional CT complex nanofiber.

One Pot, Facile Synthesis of Hierarchical Silver Nanostrip Assembling Architecture

Here we present a simple wet-chemical approach to synthesize flower-like silver nanostrip assembling architecture at room temperature. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images indicate that these microstructures with the diameter of similar to 500nm exhibit hietarchical characteristic. X-ray diffraction (XRD), energy-dispersed X-ray spectroscopy (EDX) and Raman spectroscopy indicate that poly (o-diaminobenzene) (PDB) also exists in the silver hierarchical microstructure.

Large-area silver-coated silicon nanowire arrays for molecular sensing using surface-enhanced Raman spectroscopy

A new and facile method to prepare large-area silver-coated silicon nanowire arrays for surface-enhanced Raman spectroscopy (SERS)-based sensing is introduced. High-quality silicon nanowire arrays are prepared by a chemical etching method and used as a template for the generation of SERS-active silver-coated silicon nanowire arrays. The morphologies of the silicon nanowire arrays and the type of silver-plating solution are two key factors determining the magnitude of SERS signal enhancement and the sensitivity of detection; they are investigated in detail for the purpose of optimization.

Environmentally friendly synthesis of highly monodisperse biocompatible gold nanoparticles with urchin-like shape

We report a facile and environmentally friendly strategy for high-yield synthesis of highly monodisperse gold nanoparticles with urchin-like shape. A simple protein, gelatin, was first used for the control over shape and orientation of the gold nanoparticles. These nanoparticles, ready to use for biological systems, are promising in the optical imaging-based disease diagnostics and therapy because of their tunable surface plasmon resonance (SPR) and excellent surface-enhanced Raman scattering (SERS) activity.

Dendrimers as "controllers" for modulation of electrodeposited silver nanostructures

Electrodeposition of silver nanostructures on a polyamidoamine (PAMAM) dendrimers-modified surface has been reported. The assembled PAMAM monolayer film was used as a substrate for electrodeposition. We found that the PAMAM dendrimers obviously affected nucleation growth and silver nanostructures (spherical, dendritic and "fish bone" shapes) were obtained, which were different from those deposited on unmodified surfaces. It was attributed to the unique structures and properties of PAMAM dendrimers compared with linear polymers.

Aggregation-based growth of silver nanowires at room temperature

We describe an aggregation-based growth mechanism for formation of silver nanowires at room temperature. It is found that the pH of solution and the concentration of L-cysteine capping molecules have an important effect on the formation and growth of nanowires. Characterization by atomic force microscopy (AFM) and UV-vis spectroscopy recorded as time clearly shows that the silver nanowires are grown at the expense of nanoparticles.

Photochemical synthesis and self-assembly of gold nanoparticles

Colloidal gold was prepared by UV light irradiation of the mixture of HAuCl4 aqueous solution and poly(vinyl pyrrolidone) (PVP) ethanol solution in the presence of silver ions. The resulting sheet-like nanoparticles were found to self-assemble into nanoflowers by a centrifuging process. The results of control experiments reflected that only suitable size sheet-like nanoparticles could assemble into the flower-like structures. The presence of Ag ions and PVP are essential for the formation process of nanoflowers.

Type I collagen-mediated synthesis of noble metallic nanoparticles networks and the applications in Surface-Enhanced Raman Scattering and electrochemistry

In this paper, we demonstrated an effective enviromentally friendly synthesis route to prepare noble metallic (Au, Ag, Pt and Pd) nanoparticles (NPs) networks mediated by type I collagen in the absence of any seeds or surfactants. In the reactions, type I collagen served as stabilizing agent and assembly template for the synthesized metallic NPs. The hydrophobic interaction between collagen and mica interface as well as the hydrogen bonds between inter- and intra-collagen molecules play important roles in the formation of collagen-metallic NPs networks. The noble metallic NPs networks have many advantages in the applications of Surface-Enhanced Raman Scattering (SERS) and electrochemistry detection. Typically, the as-prepared Ag NPs networks reveal great Raman enhancement activity for 4-ATP, and can even be used to detect low concentration of DNA base, adenine.

Monitoring catalytic degradation of dye molecules on silver-coated ZnO nanowire arrays by surface-enhanced Raman spectroscopy

Catalytic degradation of organic dye molecules has attracted extensive attention due to their high toxicity to water resources. In this paper, we propose a novel method for the fabrication of uniform silver-coated ZnO nanowire arrays. The degradation of typical dye molecule rhodamine 6G (R6G), as an example, is investigated in the presence of the as-prepared silver-coated ZnO nanowire arrays. The experimental results show that such composite nanostructures exhibit high catalytic activity, and the reaction follows pseudo-first-order kinetics. Furthermore, these nanowire arrays are desirable SERS substrates for monitoring the catalytic degradation of dye molecules. Compared with traditional UV-visible spectroscopy, SERS technology can reflect more truly the catalytic degradation process occurring on the surface of the catalysts.

Sensitive turn-on fluorescent detection of cyanide based on the dissolution of fluorophore functionalized gold nanoparticles

We report a simple fluorescent method for sensitive cyanide detection based on the dissolution of Rhodamine B-adsorbed gold nanoparticles by cyanide.

Sensitive detection of cysteine based on fluorescent silver clusters

In this work,we report the application of novel, water-soluble fluorescent Ag clusters in fluorescent sensors for detecting cysteine, an important biological analyte. The fluorescence of poly(methacrylic acid) (PMAA)templated Ag clusters was found to be quenched effectively by cysteine, but not when the other alpha-amino acids were present. By virtue of the specific response, a new, simple, and sensitive fluorescent method for detecting cysteine has been developed based on Ag clusters. The present assay allows for the selective determination of cysteine in the range of 2.5 x 10(-8) to 6.0 x 10(-6) M with a detection limit of 20 nM at a signal-to-noise ratio of 3. Based on the absorption and fluorescence studies, we suggested that cysteine quenched the emission by the thiol-adsorption-accelerated oxidation of the emissive Ag clusters. The present study shows a promising step toward the application of silver clusters, a new class of attractive fluorescence probes.

Characterization and optimization of AuNPs labeled by Raman reporters on glass based on silver enhancement

In this report, gold nanoparticles (AuNPs) labeled by Raman reporters (AuNPs-R6G) were assembled on glass and used as the seeds to in situ grow silver-coated nanostructures based on silver enhancer solution, forming the nanostructures of AuNPs-R6G@Ag, which were characterized by scanning electron microscopy (SEM) and UV-visible spectroscopy. More importantly, the obtained silver-coated nanostructures can be used as a surface enhancement Raman scattering (SERS) substrate. The different SERS activities can be controlled by the silver deposition time and assembly time of AuNPs-R6G on glass. The results indicate that the maximum SERS activity could be obtained on AuNPs-R6G when these nanostructures were assembled on glass for 2 h with silver deposition for 2 min.

DNA based gold nanoparticles colorimetric sensors for sensitive and selective detection of Ag(I) ions

In this work, we reported both unlabeled and labeled sensing strategies for Ag(I) ions detection by using the DNA based gold nanoparticles (AuNPs) colorimetric method. In the unlabeled strategy, C-base riched single strand DNA (C-ssDNA) enwinded onto AuNPs to form AuNPs/C-ssDNA complex. In the labeled method, sulfhydryl group modified C-ssDNA (HS-C-ssDNA) was covalently labeled on AuNPs to produce AuNPs-S-C-ssDNA complex. In both strategies, C-ss DNA or HS-C-ssDNA could enhance the AuNPs stability against the salt-induced aggregation. However, the presence of Ag(I) ions in the obtained AuNPs/C-ssDNA or AuNPs-S-C-ssDNA complex would decrease such stability to display purple even blue colors due to the formation of Ag(I) ions mediated C-Ag(I)-C base pairs. Through this phenomenon, Ag(I) ions could be detected qualitatively and quantitatively using both unlabeled and labeled sensing strategies.

Efficient preparation of silver nanoplates assisted by non-polar solvents

In the paper, we report an efficient method to prepare high yield (up to 97%) of silver nanoplates. Synthesis of silver nanoplates was carried Out in a binary solvent system of N,N-dimethylformamide (DMF) and toluene, in which DMF served as the reductant and polyvinylpyrrolidone (PVP) as the capping agent. By increasing the ratio of toluene to DMF to 7:6, silver nanoplates can be Successfully synthesized; otherwise other shaped nanoparticles would be the major products. The nanoplate sample was characterized by TEM, HRTEM, SAED, XRD, AFM and UV-visible spectroscopy, proving the high nanoplate purity of this sample. The influence of toluene content, other solvents, AgNO3 concentration, preparation temperature and chloride ions was also examined, which suggests that the function of nonpolar solvents in this system is to enhance the PVP coverage on silver surface and, furthermore, to facilitate the preferential adsorption of PVP on two (I I I) facets of silver nanoplates.