Growth Of Silver Nanostructures Research Articles

Radiation Induced Generation of Core–Shell Nanoparticles in Polyelectrolyte Films of Poly(acrylic acid)–Poly(ethylenimine) Complex with Copper and Silver Ions

Tuning the size and structure of bimetallic nanostructures is for the design of functional compounds with desirable properties. In this paper, the mechanisms that control radiation-induced assembly of bimetallic core–shell nanoparticles in polyelectrolyte matrices are discussed. The stages of Ag/Cu nanoparticle formation in the films of poly­(acrylic acid)–poly­(ethylenimine) complexes have been studied for the first time using X-ray diffraction analysis including synchrotron techniques combined with electron microscopy. The generation of silver nanostructures proceeds via their parallel nucleation and growth during the entire process of bimetallic nanoparticles formation. The sizes of shells are controlled by the competition between the growth of silver nanostructures and the formation of shells. Copper shells are generated in two stages: (1) ultrasmall nanostructures, which are slowly formed at the first stage, prevent the growth of silver nuclei; (2) as the shell improves, the growth rate of copper nanostructures increases dramatically. The results obtained demonstrate the possibility of single-stage controllable radiation-initiated synthesis of core–shell bimetallic nanoparticles directly in interpolyelectrolyte films.

The growth of silver nanostructures on porous silicon for enhanced photoluminescence: The role of AgNO3 concentration and deposition time

Silver nanostructures were obtained by using the electrodeposition method on n-type porous silicon (PSi) under different deposition times and concentrations of AgNO3 solutions. The analyses of the structural and photoluminescence properties of PSi/Ag were studied by SEM, XRD and photoluminescence spectroscopy. SEM analysis showed that the shape and size of Ag nanostructures significantly depend on the deposition time and concentration. It was found that spherical nanoparticles and thin Ag dendrites were obtained in short deposition times at 1 and 5 mM AgNO3 concentrations, whereas, Ag complex dendrite nanostructures formed in long deposition times. It was also found that only micro-sized Ag particles were formed at 10 mM. XRD results revealed that the degree of crystallization increases with increasing concentration. Photoluminescence analysis showed that the deposition time and concentration of AgNO3 remarkably affect the PL intensity of PSi/Ag samples. We determined a PL enhancement of ∼2.7 for the PSi/Ag deposited at 120 s for 1 mM AgNO3. The improved PL intensity of PSi/Ag nanostructures can be explained by the combination of quantum confinement and surface states. PL analyses also indicated that with increasing deposition time and AgNO3 concentrations, the PL intensity of PSi/Ag structures significantly decreases due to the auto-extinction phenomenon.

Experimental and Theoretical Study on the Structure, Optical Properties, and Growth of Metallic Silver Nanostructures in Ag3PO4

Theoretical and experimental studies were performed on the structure, optical properties, and growth of silver nanostructures in silver phosphate (Ag3PO4). This material was synthesized by the coprecipitation method and processed in a microwave-assisted hydrothermal system at 150 °C for different times. The structural behavior was analyzed by means of X-ray diffraction, Rietveld refinement, and Raman spectroscopy. Field emission gun scanning electron microscopy as well as transmission electron microscopy revealed the presence of irregular spherical-like Ag3PO4 microparticles; metallic silver nanostructures were found on their surfaces. The growth processes of Ag nanostructures when irradiated with an electron beam were explained by theoretical calculations. First-principles calculations, within a quantum theory of atoms in molecules framework, have been carried out to provide deeper insight and understanding of the observed nucleation and early evolution of Ag nanoparticles on Ag3PO4 crystals, driven by a...

One pot rapid synthesis of silver nanowires using NaCl assisted glycerol mediated polyol process

We report, one pot rapid synthesis of silver nanostructures from AgNO3 through glycerol mediated polyol process with the assistance of polyvinyl pyrrolidone (PVP) and NaCl. The growth of silver nanostructures was studied by monitoring changes in the position of localized surface plasmon resonance band using the UV-vis-NIR spectroscopy. Morphology of the silver nanostructures was indentified using the scanning electron microscope which confirms the formation of nanoparticle, V-shaped and linear silver nanowires. The favorable temperature and NaCl concentration to obtain nanoparticles, V-shaped and linear silver nanowires are optimized. 5 mM NaCl at 250°C produced 55 — 65 nm width, 4 μm long silver nanowires along [100] in PVP added glycerol medium within 25 minutes.

Nucleation and growth of silver nanostructures onto HOPG electrodes in the presence of picolinic acid

Fil: Vazquez, Cecilia Irene. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigaciones en Fisico-quimica de Cordoba. Universidad Nacional de Cordoba. Facultad de Ciencias Quimicas. Instituto de Investigaciones en Fisico-quimica de Cordoba; Argentina

A novel method to realize the transition from silver nanowires to nanoplates based on the degradation of DNA

Silver “nano-necklaces” and nanoplates in DNA/Tris–EDTA (TE) solution are prepared using hydrothermal method. The nano-necklaces are composed of many spherical silver nanoparticles which are joined together by the DNA chain. Further the transition from silver nano-necklaces to triangular and hexagonal nanoplates is realized based on the degradation of DNA. Transmission electron microscopy, selected area electron diffraction, ultraviolet–visible spectroscopy, X-ray diffraction, and agarose gel electrophoresis are used to characterize silver nanoparticles and the change of DNA structure. The results show that TE acts as not only the buffer solution but also the reducing agent. DNA serves as templates to offer the nucleation sites and induce the growth of silver nanostructures. Hydrothermal process provides high temperature and pressure to activate the reducing property of TE and denature or degrade DNA molecules. The formation mechanism of silver nano-necklaces and nanoplates has also been studied.

Novel Bottom‐Up SERS Substrates for Quantitative and Parallelized Analytics

Surface-enhanced Raman spectroscopy (SERS) is an emerging technology in the field of analytics. Due to the high sensitivity in connection with specific Raman molecular fingerprint information SERS can be used in a variety of analytical, bioanalytical, and biosensing applications. However, for the SERS effect substrates with metal nanostructures are needed. The broad application of this technology is greatly hampered by the lack of reliable and reproducible substrates. Usually the activity of a given substrate has to be determined by time-consuming experiments such as calibration or ultramicroscopic studies. To use SERS as a standard analytical tool, cheap and reproducible substrates are required, preferably with a characterization technique that does not interfere with the subsequent measurements. Herein we introduce an innovative approach to produce low-cost and large-scale reproducible substrates for SERS applications, which allows easy and economical production of micropatterned SERS active surfaces on a large scale. This approach is based on an enzyme-induced growth of silver nanostructures. The special structural feature of the enzymatically deposited silver nanoparticles prevents the breakdown of SERS activity even at high particle densities (particle density >60%) that lead to a conductive layer. In contrast to other approaches, this substrate exhibits a relationship between electrical conductivity and the resulting SERS activity of a given spot. This enables the prediction of the SERS activity of the nanostructure ensemble and therewith the controllable and reproducible production of SERS substrates of enzymatic silver nanoparticles on a large scale, utilizing a simple measurement of the electrical conductivity. Furthermore, through a correlation between the conductivity and the SERS activity of the substrates it is possible to quantify SERS measurements with these substrates.

The atomistic growth of silver clusters on a Si(111)7 × 7 surface

We repot here the growth of silver nanostructures on a Si(111)7 × 7 surface using scanning tunneling microscopy(STM). It is found that the each Ag atom hops each half unit cells of 7 × 7 structure and forms dimers, trimers, tetramers and pentamers inside the half unit cells. We estimate intercell hopping rates of (1.39±0.16) × 10−4 1/s for trimers and (1.33±0.14) × 10−31/s for tetramers. We also observed the intracel motion of trimers.

Synthesis and Growth Mechanisms of Ag Metallo-Organic Nanoparticles in Different Morphologies by Using Polymer-Mediated Polyol Process

Mono-dispersed silver nanoparticles with various morphologies were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinylpyrrolidone) (PVP). The effects of the concentration of AgNO3, temperature, adding rates of PVP and AgNO3 injected into ethylene glycol as well as molar ratio between the repeating unit of PVP and AgNO3 were discussed. By varying the temperature and reaction time, silver nanocubes, nnoprisms and nanospheres were obtained. It is indicated that at elevated temperatures, the ethylene glycol can reduce Ag+ ion into Ag atoms, and thereby inducing the nucleation and growth of silver nanostructures in the solution phase. In the polymer-mediated polyol process, PVP plays a critical role in producing silver nanostructures with good stability and size/shape uniformity. As a result, both the crystallinity of a seed and extent of PVP coverage on the seed were instrumental in controlling the morphology of Ag nanoparticles.