Silver Dendrites Research Articles

Electrocrystallization of silver dendrites

Morphology of electrodeposited silver dendrites was investigated by scanning electron microscope (SEM). On the basis of morphological analysis, the structures and mechanism of growth were proposed. Silver dendrite is twin crystal with {111} twinning plane and direction of growth <112>. Mechanism of growth represents combinations of three steps: a) growth by propagation of twin planes, b) slip of twin planes and c) layer growth on the final (111) faces.

Optimized Silicon Nanostructures Formed by One-Step Metal-Assisted Chemical Etching of Si(111) Wafers for GaN Deposition

Nanostructuring of silicon substrates has been used as a technique to reduce defects in epitaxial GaN growths on them. To fabricate the nanostructures, metal-assisted chemical etching (MACE) is a promising method. In particular, the one-step MACE (using silver nitrate and HF solution) is highly attractive, due to its simple and low cost fabrication method. Here we report experimental results of etched silicon, using different etching conditions, in order to obtain an optimized etching conditions. Process conditions of 5.0 M of HF and 0.02 M of AgNO3 at 25°C without stirring was found to be suitable for patterning silicon substrates for subsequent GaN growth. We have also evaluated the effect of the presence of dendrites on the etch rate of silicon and determined that the etch rate was enhanced by the coverage of silver dendrite. It was found that the etching mode changed from a short etching time regime (Regime I) to a long etching time regime (Regime II). Etch rate was increased by almost 80% when silver dendrites coverage was at 64%. Further increase in dendrites coverage did not increase the etch rate. Additionally, GaN has been successfully grown on substrates prepared by this method.

Carbon nanotube and graphene oxide directed electrochemical synthesis of silver dendrites

A simple one-step electro-deposition method was employed for the synthesis of silver dendritic structures with the aid of graphene oxide (GO) modified multi-walled carbon nanotubes (MWCNTs) which are dispersed in an AgNO3 solution.

Sulfate-ion-assisted galvanic replacement tuning of silver dendrites to highly branched chains for effective SERS.

Morphology is a primary part of designing metal nanocrystals and nanomaterials with controlled functional properties. Here, we demonstrate the potential of foreign sulfate ions to tune the silver dendrites to highly branched chains through a simple galvanic replacement reaction without introducing any organic surfactants. We further illustrate the underlying mechanism according to diffusion-limited aggregation (DLA) in the presence of sulfate ions. The special aspects of this simple synthetic strategy are the control of both the nucleation process and the subsequent crystal growth stage by using sulfate ions as the ionic surfactants thereby tuning the total surface energies on various crystal facets in solution and transforming crystal growth habits of the products. Moreover, the highly branched silver chains (HBSCs) with pure surfaces have been successfully employed as a Raman probe for surface-enhanced Raman spectroscopic analysis of rhodamine 6G (R6G). The particular morphology of those HBSCs also makes them find potential applications in biosensing, catalysis and optics.

Chemical preparation and applications of silver dendrites

AbstractSilver dendrites have received immense attention because of their fascinating hierarchical structures and unique properties. Depending on the methods of synthesis, Ag dendrites can be implemented in numerous fields. This review summarizes a variety of Ag dendrites preparation techniques. The involved growth mechanisms are investigated in order to control the formation progress more effectively. With regard to the applications, this article mainly focuses on surface enhanced Raman spectroscopy, catalysis, superhydrophobic surface and surface enhanced fluorescence by using Ag dendrites. The remaining issues of the preparation methods, which impede the practical applications of Ag dendrites, are pointed out to enlighten their future research.

Tilt boundary induced heteroepitaxy in chemically grown dendritic silver nanostructures on germanium and their optical properties.

Dendritic silver nanostructures were prepared by a simple dip-and-rinse galvanic displacement reaction directly on germanium surfaces. The formation and evolution of these dendrites were investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). The present results clearly show a new type of heteroepitaxy, where the large lattice mismatch between silver and germanium is accommodated at the interface by the formation of low-energy asymmetric tilt boundaries. The overgrown samples reduce the strain by introducing crystal defects. Additionally, by employing cathodoluminescence (CL) spectroscopy and imaging with a field emission gun scanning electron microscope (FEG-SEM), we provide information on the surface plasmon assisted photon emission of a stack of Ag hexagonal nanostructures. Surface enhanced Raman scattering (SERS) studies show the suitability of such Ag nanodendritic structures as SERS active substrates.

Sandwich-structured Ag/graphene/Au hybrid for surface-enhanced Raman scattering

The Ag/graphene/Au nanostructure as an efficient surface enhanced Raman scattering (SERS)-active substrate was fabricated by sandwiching the reduced graphene oxide (rGO) between plasmonic silver dendrites and gold nanoparticles layers by a simple electrodeposition method. The surface plasmons aroused in the Ag-rGO interface could be effectively transferred from the silver to the top gold by rGO interlayer, which favored the higher SERS activity of Ag/rGO/Au hybrid compared to the Ag/rGO and Au/rGO/Au ones due to the more localized plasmon resonance on the gold surface. Furthermore, the reduction degree of rGO interlayer impacted the nucleation and growth of gold on the rGO surface and therefore the Raman signal for Rhodamine B molecules absorbed on the Ag/rGO/Au sandwich nanostructure. The rGO sheets and the top gold nanoparticles film also effectively protected the silver dendrites from oxidation under ambient condition. This Ag/rGO/Au sandwich nanostructure was useful for the development of an efficient SERS-based chemical sensor because of the simply fabrication, adjustable SERS activity, long-term stability and high reproducibility.

A novel strategy to prepare silver nanoparticles by ethanol-induced shape conversion of silver dendrites from modified galvanic replacement

The fabrications of the silver nanostructures with various shapes have been successfully conducted by using an ultrasound assisted galvanic replacement reaction (GRR) in aqueous solutions containing silver nitrate and copper sheet using PVP as stabilizer. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to characterize the as-synthesized silver products. The results show that a variety of silver nanostructures, such as silver dendrites, the triangular, hexagonal, disk nanoplates and spherical nanoparticles, can be yielded in large scale by facilely tuning the silver nitrate concentrations, temperature and concentration of PVP in aqueous solutions. The as-synthesized silver dendrites were deposited in ethanol without any field (UV or visible light irradiation) or thermally induced activation, a significantly spontaneous evolution in morphology occurred from the fractal structure to silver nanoparticles at room temperature. Moreover, the mechanisms of the architectural reconstruction of silver nanostructures in ethanol at room temperature by self-assemble were discussed. The proposed dissolution recrystallization process induced by ethanol may be responsible for the morphological reconstructure of the as-synthesized Ag dendrites.

Electrochemical determination of dissolved oxygen based on three dimensional electrosynthesis of silver nanodendrites electrode

In this paper, a highly sensitive electrochemical sensor for dissolved oxygen was prepared. A glassy carbon electrode was modified with silver nanodendrites that were synthesized by electrochemical deposition on the electrode without the use of a surfactant or template. The electrode displayed efficient electrocatalytic reduction of dissolved oxygen to form hydroxy ions via a four-electron reduction pathway, and a significant decrease in the respective overvoltage. The sensor responded linearly to dissolved oxygen in the 1.0–66.7 μM concentration range, and had a remarkably good sensitivity (0.169 μA μM−1) at an applied potential of −300 mV (vs. Ag/AgCl). The lower detection limit was 0.043 μM (at the signal-to-noise ratio of 3), and the response time was 5 s. The good performance was attributed to the enlarged electro-active surface of the dendritic silver nanostructures and to the efficiency of electron transfer between dissolved oxygen and the electrode. The sensor also showed good reproducibility, long-term stability, and relative good selectivity.

Photochemical assisted formation of silver nano dendrites and their application in amperometric sensing of nitrite

Herein, we describe a photochemical route for the synthesis of silver (Ag) dendrites nanostructure using phenothiazine (PTZ) as a reductant as well as stabilizer without any extra control viz. surfactant, pH etc. This hybrid material derived from nanoscale silver capped with phenothiazine and its oxidation product (PTZH) has been explored for the development of a highly sensitive electro-sensor of nitrite ions. Further, a possible reaction mechanism for the formation of the silver dendrites nanostructure has also been proposed. The synthesized hybrid material (Ag–PTZH) has been characterized by UV-visible spectroscopy, cyclic voltammetry, transmission electron microscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. This hybrid material modified electrode efficiently catalyzes the electrochemical oxidation of nitrite at the potential of 0.44 V vs. AgCl/Ag and shows a linear response towards nitrite ion sensing with 2.43 μA μM−1 sensitivity and 2.3 nM limit of detection at a S/N (signal-to-noise ratio) of 3. The electrochemistry behind this sensing of nitrite is probably due to high connectivity throughout the silver dendrites nanostructure capped with phenothiazine and its oxidation product which exhibits high electron transfer kinetics via interaction of Ag–PTZH with oxygen atoms of NO2−.

Determination of α-Tocopherol in Vegetable Oils Using a Molecularly Imprinted Polymers–Surface-Enhanced Raman Spectroscopic Biosensor

We report the development of a novel hybrid "capture-detection" molecularly imprinted polymers-surface-enhanced Raman spectroscopic (MIPs-SERS) biosensor for the detection and quantification of α-tocopherol (α-Toc) in vegetable oils. α-Toc served as the template for MIPs synthesis. Methacrylic acid formed as the functional monomer. Ethylene glycol dimethacrylate was the cross-linking agent, and 2,2'-azobisisobutyronitrile was used as the initiator. The synthesized MIPs functioned to rapidly and selectively adsorb and separate α-Toc from oil components. We validated a dendritic silver nanostructure synthesized by a displacement reaction to be a suitable SERS substrate for the enhancement of Raman signals. Second-derivative transformations and chemometric models based upon SERS spectral features confirmed the possibility of a rapid and precise detection and quantification of different spiking levels of α-Toc in four different sources of vegetable oils (Mahalanobis distance from 15.93 to 34.01 for PCA model; R > 0.92, RMSE < 0.41 for PLSR model). The MIPs-SERS biosensor had a high sensitivity as well as a good recovery for α-Toc analysis in vegetable oils. The entire analysis required 15 min or less to complete with limited sample preparation.

Recovery and quantitative detection of thiabendazole on apples using a surface swab capture method followed by surface-enhanced Raman spectroscopy

We developed a rapid and simple method which combines a surface swab capture method and surface-enhanced Raman spectroscopy for recovery and quantitative detection of thiabendazole on apple surfaces. The whole apple surface was swabbed and the swab was vortexed in methanol releasing the pesticide. Silver dendrites were then added to bind the pesticide and used for enhancing the Raman signals. The recovery of the surface swab method was calculated to be 59.4–76.6% for intentionally contaminated apples at different levels (0.1, 0.3, 3, and 5ppm, μg/g per weight). After considering the releasing factor (66.6%) from the swab, the final accuracy of the swab-SERS method was calculated to be between 89.2% and 115.4%. This swab-SERS method is simple, sensitive, rapid (∼10min), and quantitative enough for QA/QC in plant procedure. This can be extended to detect other pesticides on raw agricultural produce like pears, carrots, and melons etc.

Dendritic silver nanostructures obtained via one-step electrosynthesis: effect of nonanesulfonic acid and polyvinylpyrrolidone as additives on the analytical performance for hydrogen peroxide sensing

The electrochemical deposition of silver nanodendrites (AgNDs) on pure graphite sheet (PGS) electrodes, both in the absence of surfactant/templates and in the presence of 1-nonanesulfonic acid (NS) or polyvinylpyrrolidone (PVP) additives, is reported. The synthesis carried out without additives and with NS produced a bigger amount of large size AgNDs (dimension of 1–5 μm), with scarce influence played by NS, while the deposition with PVP favoured the formation of smaller spherical particles (with average diameter below 150 nm). The performances of the electrodes towards the electroreduction of H2O2 were investigated by chronoamperometry at −0.4 V and at more cathodic applied potentials (−0.6 and −0.8 V). The electrodes fabricated without additives and in the presence of NS displayed similar performances, while those fabricated with PVP exhibited significantly lower sensitivity. This suggests that AgNDs present enhanced electrocatalytic activity in respect to the spherical aggregates, since the Ag amount deposited on PGS was practically the same. The best amperometric responses among those recorded at −0.4 V in PBS (pH 6.7) exhibited a linear range extending from 0.1 to 3.5 mM, a detection limit of about 20 μM and a sensitivity close to 200 mA M−1 cm−2. The proposed electrodes display sensitivities which are markedly better than those reported in the literature for similar Ag-based sensors.

Weak Magnetic Field Effects on Silver Dendrite Formation

Abstract Effects of a weak magnetic field (&amp;lt;0.1 T) on silver dendrite formation were studied using a ferrite magnet. By application of a 87 mT field, the silver dendrite pattern changed considerably, although chemical yields of formed silver dendrite, formed copper ion, and consumed copper metal decreased very slightly.

Monitoring the Chemical Production of Citrus-Derived Bioactive 5-Demethylnobiletin Using Surface-Enhanced Raman Spectroscopy

To develop an accurate and convenient method for monitoring the production of citrus-derived bioactive 5-demethylnobiletin from the demethylation reaction of nobiletin, we compared surface-enhanced Raman spectroscopy (SERS) methods with a conventional high-performance liquid chromatography (HPLC) method. Our results show that both the substrate- and solution-based SERS methods correlated with the HPLC method very well. The solution method produced lower root-mean-square error of calibration and higher correlation coefficient than the substrate method. The solution method used an "affinity chromatography"-like procedure to separate the reactant nobiletin from the product 5-demthylnobiletin based on their different binding affinities to the silver dendrites. The substrate method was found simpler and faster to collect the SERS "fingerprint" spectra of the samples because no incubation between samples and silver was needed and only a trace amount of samples was required. Our results demonstrated that the SERS methods were superior to the HPLC method in conveniently and rapidly characterizing and quantifying 5-demethylnobiletin production.

Facile fabrication of leafy spikes-like silver dendrite crystals for SERS substrate

In this work, leafy spikes-like silver dendrites were synthesized in a large scale via facile strategy method and this kind of silver nanocrystals exhibit a special textured surface morphology with a wedge-shaped architecture and higher specific surface area. The influence of experimental parameters including reaction time, concentration of the reactants and the reaction temperature on the dendrite morphology was also discussed employing SEM and SERS method. It was found that these spikes-like silver dendrites obtained under the optimal condition could serve as highly sensitive substrates for surface-enhanced Raman scattering (SERS) detection.

Electrodeposition of Dendritic Silver Nanostructures and Their Application as Hydrogen Peroxide Sensor

Electrodeposition of Dendritic Silver Nanostructures and Their Application as Hydrogen Peroxide Sensor

Facile synthesis of Ag dendrites on Al foil via galvanic replacement reaction with [Ag(NH3)2]Cl for ultrasensitive SERS detecting of biomolecules

Symmetric silver dendrites have been synthesized on commercial aluminum foil via galvanic replacement reaction with [Ag(NH3)2]Cl. This process is facile and environmentally friendly, without the use of any templates, surfactants or oxidants, and also avoiding the introduction of fluoride anions as a strong toxicity resulting in hypocalcemia. The products were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and X-ray diffraction (XRD). SEM characterizations and electrochemical measurements including an electrochemical direct current polarization method and OCP-t technique demonstrate that chloride has proven to be the key factor to the formation of well-defined dendritic shape. The as-prepared Ag dendrites are developed as a surface-enhanced Raman scattering (SERS)-active platform for detection of folic acid, DNA and RNA with well resolved bands and high Raman intensities. The detection concentration for the three biomolecules reaches the level of 10−12M, and thus the symmetric silver dendrites can potentially be employed as effective SERS sensors for label-free and ultrasensitive biomolecule detection.

Unique flexible silver dendrites thin films fabricated on cellulose dialysis cassettes

This study reports on the deposition of flexible silver dendrites thin film on the cellulose membrane. The formation of dendritic silver nanostructures derives from the continuous aggregation growth of silver nanoparticles. The increase in the AgNO3 concentration showed the formation of anisotropic Ag thin films demonstrated by an increase in the surface roughness factor. The reported method represents a simplistic method for the deposition of silver dendrites nanostructure thin films. A combination of characterization techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy was used and all confirmed the formation of Ag dendrite thin films.

Preparation of Ag–Cu bimetallic dendritic nanostructures and their hydrogen peroxide electroreduction property

In this work, dendritic silver–copper (Ag–Cu) nanostructures were synthesised on a copper foil by electrodeposition and subsequently galvanic displacement reaction without any surfactant. The crystalline nature of the nanostructures was examined by X-ray diffraction, and the morphology of the material was investigated by field-emission scanning electron microscopy. The applied potential, displacement reaction time, and silver nitrate solution concentration exerted different effects on the nanoparticle shape. And a possible growth mechanism of the Ag–Cu dendrites was proposed based on the experimental results. The electrochemical properties of the Ag–Cu dendrite-modified electrode were characterised by linear sweep voltammetry. The reduction peak potential of hydrogen peroxide (H2O2) was about −0.25 V (vs. a saturated calomel electrode), which indicated that the as-synthesised Ag–Cu dendrites had favourable electroreduction activity towards hydrogen peroxide. At the same time, we found that the solution pH also affected the electrocatalytic ability of the dendrites for H2O2 reduction, which was important for the design of a NaBH4–H2O2 battery.