Silver Dendrites Research Articles

Synthesis of dendritic silver nano powder using pulsing electrolysis in ammonia solution

A method to produce nano silver structures with high purity is pulsing electrolysis. In this paper the effects of potential, ammonia concentration (NH3), silver ion concentration [Ag+], total time, Ton, Toff and Trev on this process were studied. The considered parameters were varied as follows: electrical potential = 5 ? 10 V; [NH3] = 40 ? 80 g/L; [Ag+] = 0.1 ? 0.5 g/L; total time = 15 ? 30 min; Ton = 1 ? 8 ms; Toff = 1 ? 8 ms; and Trev = 0 ? 4 ms. In order to optimize these parameters, the fractional factorial design of experiments was used. A silver dendritic structure was produced with nano size arm. The phase composition and morphology of the synthetized dendritic silver nanostructures was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The optimum condition to synthesize the dendritic silver nano powders were 7.52 V; [NH3] = 64.75 g/L; [Ag+] = 0.45 g/L; total time = 17.59 min; Ton = 6.97 ms; Toff = 4 ms; and Trev = 1.89 ms. A mathematical model was also presented. The predicted silver nano size dendrite arm at the optimum condition was found to be 87.29 nm which was very close to the experimental value of 90 nm.

Modeling the growth of dendritic electroless silver colonies using hexagonal cellular automata

In this paper, we present results of in silico simulation of dendritic electroless silver colony growth model on a hexagonal cellular automata lattice. A cellular automaton, based on a NetLogo framework, was used to replicate the behavior of a colony. Experiments showed that a Hex Cell Aggregation model from NetLogo library, which we used as a base, can demonstrate the patterns similar to those in experimental data. However, several features of the colony growth cannot be explained within the existing model and require its modifications.

Photochemical synthesis of dendritic silver nano-particles for anti-counterfeiting

An ambient condition, polymer assisted photo-synthesis of silver dendrites with highly tunable geometry and sizes.

Electroless deposited silver dendrites for SERS identification of natural dyes on laboratory-dyed and historic textiles

Nanostructured silver having dendritic morphology is known to provide meaningful Raman signal enhancements. Herein, commercial silicon wafers were easily functionalized with silver dendrites by Galvanic electroless displacement. The superficial oxide layer was removed by treating the wafers with diluted HF to expose the pure silicon, which reacted with silver nitrate to form metallic silver. The morphology of the deposited silver nanostructures was assessed by SEM measurements. Afterwards, the potentialities of the fabricated substrates were tested in the analysis of several natural organic dyes used in antiquity, especially in textile dyeing, by surface-enhanced Raman scattering (SERS) spectroscopy. For the analysis, laboratory-dyed textiles were micro-extracted with a mild aqueous treatment, and the liquid fraction adsorbed and pre-concentrated on pure or functionalized silicon. The method was also applied to the analysis of dyes in archaeological Coptic textiles (30 B.C.-640 A.D.) of Egyptian origin. Together with the identification of the organic dye, the assessment of the inorganic mordant was obtained by surfaced-enhanced laser-induced breakdown spectroscopy (SENLIBS).

Copper-surrogated galvanic displacement of silver dendrite imprinted on flexible and transparent silk fibroin membrane as a SERS-active substrate and sub-dividable catalyst

By employing copper grid as a surrogate agent, we present a facial, reagent-free and cost-effective approach to imprint the exquisite silver dendroid nanostructures on flexible silk fibroin membrane, which double roles as both optical enhancers and catalytic-active sites over many chemical reactions. Unlike the conventional rigid substrates, this hybrid Ag/protein composite exhibits many previous-inaccessible properties of flexibility, transparency, biocompatibility, molecular permeability and optical manipulation. The galvanic displacement was facilitated by a high pressure uv-lamp illumination (365 nm), shortening the dendroid growth time to be within a few minutes. The resulting substrate was characterized by microscopic image, revealing a decent 3D Ag dendrite architecture and interpenetrated crystal network, which arguably enlarged the entire surface area and keenly regulated the optical/electric property of fibrillated protein film. The underlying principle of copper-initiated silver reduction and growth of crystal structure was discoursed and verified with in-situ spectroscopic interrogation. Moreover, our comprehensive study supports that sub-dividable substrate enables to perform catalytic reaction under a wide range of conditions. This exploration renders a thrust to expand biopolymeric membrane into a wide breadth of applications of bendable devices through chemical modifications, exhaustively and economically.

Tailoring Copper Foam with Silver Dendrite Catalysts for Highly Selective Carbon Dioxide Conversion into Carbon Monoxide.

The present study outlines the important steps to bring electrochemical conversion of carbon dioxide (CO2) closer to commercial viability by using a large-scale metallic foam electrode as a highly conductive catalyst scaffold. Because of its versatility, it was possible to specifically tailor three-dimensional copper foam through coating with silver dendrite catalysts by electrodeposition. The requirements of high-yield CO2 conversion to carbon monoxide (CO) were met by tuning the deposition parameters toward a homogeneous coverage of the copper foam with nanosized dendrites, which additionally featured crystallographic surface orientations favoring CO production. The presented results evidence that Ag dendrites, owing a high density of planes with stepped (220) surface sites, paired with the superior active surface area of the copper foam can significantly foster the CO productivity. In a continuous flow-cell reactor setup, CO Faradaic efficiencies reaching from 85 to 96% for a wide range of low applied cathode potentials (<1.0 VRHE) along with high CO current densities up to 27 mA/cm2 were achieved, far outperforming other tested scaffold materials. Overall, this research provides new strategic guidelines for the fabrication of efficient and versatile cathodes for CO2 conversion compatible with large-scale integrated prototype devices.

Silicon-silver dendritic nanostructures for the enhanced photoelectrochemical splitting of natural water

We report on the photoelectrochemical (PEC) splitting of natural water (pH 7) using silicon (Si) nanowires fitted with silver (Ag) dendrites (dendritic nanostructures) as working electrodes (photoanodes). A detailed study of the PEC water splitting process was carried out using linear sweep voltammetry, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) measurements. The measured photocurrent density of 1.7 mA/cm2 at an external voltage of −0.6 V under white light illumination demonstrates the efficient decomposition of natural water using dendritic nanostructures as working electrodes. This decomposition is mainly attributed to a significant strengthening of the effective interface between working electrode surface/water and to a decline in the recombination of photoinduced carriers in the presence of Ag dendrites. We propose that the Schottky barrier between Si and Ag dendritic nanostructures favors enhanced photoinduced charge carrier separation. Photoinduced holes in Si are transferred to Ag dendrites (nano branches and leaves) that serve as a charge sink to effectively carry out the PEC oxidation of water. Photoinduced charge carrier separation enhancement was corroborated by the kinetics of our carrier recombination study. We obtained a reasonably long transient period of 80 s for the photoinduced carriers. EIS results show that the charge transfer resistance (150 Ω) of the dendritic nanostructure surface is low enough to promote interfacial charge transfer. This resistance generated a large carrier concentration of ∼1.1 × 1020 cm−3 at the working electrode/water interface according to an M-S analysis. An applied bias-photon-to-current-conversion efficiency level of roughly 4% is reported, demonstrating the efficient PEC splitting of natural water.

Silver morphology indicating the evolution of concentration heterogeneity

Heterogeneity is the main problem of scaleups. The common strategy to solve this problem is the enhancement of transport. Here we show an alterative by figuring out the role of heterogeneity and then controlling the heterogeneity for desired products. We employed a gel system to create a diffusion limitation and to discover how the local concentration heterogeneity influences the shape development of silver particles in an electrochemical synthesis process. An interesting phenomenon was observed that the shapes of silver particles were dependent on their location. Silver dendrites were synthesized around the electrode, while polycrystalline spheres were obtained at the forward growth front. The mixture of dendritic and spherical particles was observed between the electrode and the growth front. A temporal evolution of concentration heterogeneity was proposed to interpret the dependence of particle morphology with location. This interpretation was confirmed by regulating the concentration distribution in different gel systems and at different reaction rates. This paper showed that the concentration distribution plays a significant role in the shape development of particles, and controlling the local heterogeneity promises an alternative for the rational synthesis of materials.

Superhydrophobic SERS substrates based on silver dendrite-decorated filter paper for trace detection of nitenpyram

In the present work, highly sensitive Raman detection of nitenpyram using superhydrophobic filter paper as substrates is introduced. The process is simple, and efficient. By sequentially coating silver dendrites and Octyltrimethoxysilane (OTMOS) on filter paper, we produced highly active surface-enhanced Raman scattering (SERS) substrates which show advancing and receding water contact angles of θA/θR = 159°/156°. Nitenpyram, a type of pesticides popularly used in agriculture, can be easily detected with the detection limit as low as 1 nM using the superhydrophobic filter paper as SERS substrates, which validates their use in Raman applications.

Development of a novel bi-enzymatic silver dendritic hierarchical nanostructure cascade catalytic system for efficient conversion of starch into gluconic acid

The natural cascade processes lead to inspire researchers to bring diverse biocatalysts together in an artificial way. In this work, we are going to introduce a brilliant double enzyme microsystem prepared from co–immobilization of glucose oxidase (GOD) and glucoamylase (GA) on silver dendrites hierarchical (Ag–DH) nanostructure through Ugi four-component reaction (Ugi–4CR) in water, as the green solvent at ambient temperature. The success preparation of the unique biocatalyst system was confirmed by FT–IR, UV–Vis, TGA, XRD, TEM, FE–SEM, AFM and elemental analysis. The properties of free and immobilized enzymes were investigated and compared. The immobilized GA and GOD had higher Km (Michaelis constant) and lower Vmax (maximum reaction velocity) than their native forms. The values of activation energy (Ea) for both the immobilized enzymes were smaller than those with native enzymes, implying that the immobilized enzymes are more temperature insensitive. The obtained double enzyme microsystem was employed as a biocatalyst for one pot transformation of starch to gluconic acid as an exclusive cascade reaction under mild conditions and in aqueous medium, and the final product obtained in high yield. Moreover, the artificial biomimetic microsystem exhibited high stability and reusability after eight cycles. These results demonstrated the feasibility of this approach for co-immobilization of enzyme on hierarchical structures may be extended to other biocatalytic cascades, thereby opening a new window for the other artificial biotransformations in chemistry.

Correlation between crystal structure and morphology of potentiostatically electrodeposited silver dendritic nanostructures

Abstract Silver dendritic nanonstructures obtained by the potentiostatic electrolysis from different electrolytes at different overpotentials were characterized by the scanning electron microscopy (SEM) technique and X-ray diffraction analysis of the produced particles. The needle-like and fern-like dendrites were formed from the nitrate electrolyte at overpotentials inside and outside plateaus of the limiting diffusion current density, respectively. The three-dimensional pine-like dendrites constructed from approximately spherical grains were formed from the ammonium electrolyte at overpotentials both inside and outside plateaus of the limiting diffusion current density. The morphology of silver dendrites was correlated with their crystal structure at the semi quantiative level. The change of crystal orientation from the strong (111) preferred orientation for the needle-like dendrites to almost randomly orientied spherical grains in the pine-like dendrites obtained at the overpotential outside the plateau of the limiting diffusion current density was observed. This trend in change of crystal orientation and morphology of Ag nanostructures was accompanied by considerable increase of the specific surface area (SSA) of the produced powders. The average crystallite sizes were in the range of 38–50 nm, proving nanostructural character of the formed Ag particles.

Direct Detection of Toxic Contaminants in Minimally Processed Food Products Using Dendritic Surface-Enhanced Raman Scattering Substrates.

We present a method for the surface-enhanced Raman scattering (SERS)-based detection of toxic contaminants in minimally processed liquid food products, through the use of a dendritic silver nanostructure, produced through electrokinetic assembly of nanoparticles from solution. The dendritic nanostructure is produced on the surface of a microelectrode chip, connected to an AC field with an imposed DC bias. We apply this chip for the detection of thiram, a toxic fruit pesticide, in apple juice, to a limit of detection of 115 ppb, with no sample preprocessing. We also apply the chip for the detection of melamine, a toxic contaminant/food additive, to a limit of detection of 1.5 ppm in milk and 105 ppb in infant formula. All the reported limits of detection are below the recommended safe limits in food products, rendering this technique useful as a screening method to identify liquid food with hazardous amounts of toxic contaminants.

A completely green approach to the synthesis of dendritic silver nanostructures starting from white grape pomace as a potential nanofactory

A simple, eco-friendly, cost-effective and rapid microwave-assisted method has been developed to synthetize dendritic silver nanostructures, composed of silver nanoparticles (AgNPs), using white grape pomace aqueous extract (WGPE) as both reducing and capping agent. With this aim, WGPE and AgNO3 (1 mM) were mixed at different ratio, and microwave irradiated at 700 W, for 40 s. To understand the role of bioactive compounds involved in the green synthesis of AgNPs, preliminary chemical characterization, FT-IR analysis and 1H NMR metabolite profiling of WGPE were carried out. The effects of bioactive extract concentration and stability over time on AgNPs formation were also evaluated. WGPE-mediated silver nanostructures were then characterized by UV–vis, FTIR analyses, and scanning electron microscopy. Interestingly, the formation of dendritic nanostructures, originated from the self-assembly of Ag rounded nanoparticles (average diameter of 33 ± 6 nm), was observed and ascribed to the use of microwave power and the presence of organic components within the used WGPE, inducing an anisotropic crystal growth and promoting a diffusion-limited aggregation mechanism. The bio-dendritic synthetized nanostructures were also evaluated for potential applications in bio-sensing and agricultural fields. Cyclic voltammetry measurements in 0.5 M phosphate + 0.1 M KCl buffer, pH 7.4 showed that green AgNPs possess the electroactive properties typical of AgNPs produced using chemical protocol. The biological activity of synthetized AgNPs was evaluated by in-vitro antifungal activity against F. graminearum. Additionally, a phytotoxicity evaluation of synthetized green nanostructures was carried out on wheat seed germination. Results highlighted the potential of WGPE as green agent for bio-inspired nanomaterial synthesis, and of green Ag nanostructures, which can be used as antifungal agent and in biosensing applications.

Versatility of electrochemically grown dendrites in the undergraduate laboratory

We describe an experiment to fabricate atomic-scale contacts using electrochemically grown silver wires. The formation of a single-wire junction is directly observed and captured by an optical microscope, while electrical conductance of the wire, simultaneously recorded, is shown to be quantized. Further, a diffusion-limited aggregate (DLA) simulation is performed to compare the observed fractal formed by the silver dendrites. Our experiment directly exposes undergraduate students to exciting contemporary physics ranging from atomic-scale switches to fractal formation, all on a single experimental platform.

Preparation of Silver-Doped Alumina Spherical Beads with Antimicrobial Properties

The synthesis of composites with antibacterial properties is of great interest for the development of new biomedical applications. The antimicrobial properties of silver have been verified against microorganisms such as bacteria, viruses, and fungi; interest in silver has been renewed, so several technologies are currently in development, especially in dental materials. The purpose of this work was to improve the parameters for producing silver-doped alumina spherical beads using sodium alginate as a sacrificial template. Alumina is a biocompatible and thermally stable ceramic, while silver was used for its bactericidal properties. The obtained spheres presented a mean diameter of 2 mm, with an irregular surface and intertwined particles after a sintering process. After electrodeposition, white spheres turned to a dark gray color, demonstrating the presence of silver nanoparticles and fractal silver dendrites on the surface. Spheres were characterized by SEM, FTIR, and XRD. Antimicrobial activity of the alumina-AgP spheres against E. coli, S. aureus, K. pneumoniae, and S. mutans was analyzed by turbidimetry. The specific antimicrobial activity of all the composites showed specific antibacterial effects, independently of the amount of silver deposited, probably due to the differences in the microbial cell wall structures. Therefore, antibacterial activity depends on microbiological and structural characteristics of each bacterium.

Super Antiwetting Surfaces for Mitigating Drag-Out of Deep Eutectic Solvents.

Deep eutectic solvents (DESs) are, at room temperature, about dozens to hundreds of times more viscous than water, which brings pretty thick residues on solid surfaces, for example, causing drag-out and weight loss in the transfer process. Unfortunately, until now little work had been done for solving this knotty problem. In this study, the super antiwetting surface, i.e., super-DES-phobic surface (defined as DES contact angle > 150°) is proposed and fabricated successfully by a facile coating technique. Hierarchical silver dendrites on copper foam substrate provide effective dual-roughness surfaces showing stable superDESphobicity. The superDESphobic surface can repel the DESs and their derived solutions even under elevated temperature of about 120 °C and the impact attack of drops. It is also found that the superDESphobic surface can significantly delay the DESs freezing and reduce the adhesion strength of the frozen DESs. Interestingly, the superDESphobic surface can be applied as an effective tool for gauging the density of DES using an ∼2 μL droplet in virtue of its super antiwetting property. The super antiwetting surfaces show promise for potential applications in DES self-cleaning and antifreezing.

Rationally Designed Graphene/Bilayer Silver/Cu Hybrid Structure with Improved Sensitivity and Stability for Highly Efficient SERS Sensing.

A simple and cost-effective strategy was rationally designed to fabricate a special sandwich structure consisting of graphene, bilayer silver, and a copper plate, which was used as a surface-enhanced Raman scattering (SERS) substrate for highly efficient SERS sensing and detection of trace molecules. Silver dendrite (AgD) nanostructures were subsequently grown on a silver nanosphere (AgNS)/Cu surface to form a bilayer silver/Cu structure, which showed a 1.5-fold Raman enhancement compared to that of the AgNS/Cu substrate. After depositing graphene on the bilayer silver/Cu substrate to obtain a sandwich structure, a higher SERS enhancement and better durability were enabled. The SERS performances, measured by a portable Raman instrument, showed that the optimized sandwich structure substrate exhibited high SERS sensitivity to crystal violet (CV) and rhodamine 6G (R6G) with low limit of detection of 10–9 and 10–8 M, respectively. Such a sandwich-structured substrate exhibited good reproducibility across the entire detection areas with an average relative standard deviation less than 5.9%, which permits its reliable quantitative detection of CV and R6G molecules. In addition, graphene both effectively improved the SERS performances and protected Ag nanocrystals from oxidation, which endowed the sandwich structure a long-term stability with deviation of characteristic peaks’ intensity lower than 3.6% after 25 days. This study indicates that the graphene/bilayer silver/Cu sandwich structure as a SERS substrate has a great potential in detecting environmental pollutants.

Freestanding silver dendrite/graphene oxide composite membranes as high-performance substrates for surface-enhanced Raman scattering

Herein we report the facile synthesis of freestanding silver dendrite (AgD)/graphene oxide (GO) composite membranes, and demonstrate their use as an efficient and robust substrate with large-area uniformity and good reproducibility for surface-enhanced Raman scattering (SERS) applications. The as-prepared composite membranes exhibit excellent sensitivity for detecting rhodamine 6G and 5,5′-dithiobis-(2-nitrobenzoic acid). The results suggest that AgD/GO nanocomposite membrane holds great promise as a high-performance SERS substrate for plasmonic sensing applications.

Silver Flakes and Silver Dendrites for Hybrid Electrically Conductive Adhesives with Enhanced Conductivity

Silver dendrites were prepared by a facile replacement reaction between silver nitrate and zinc microparticles of 20 μm in size. The influence of reactant molar ratio, reaction solution volume, silver nitrate concentration, and reaction time on the morphology of dendrites was investigated systematically. It was found that uniform tree-like silver structures are synthesized under the optimal conditions. Their structure can be described as a trunk, symmetrical branches, and leaves, which length scales of 5–10, 1–2 μm, and 100–300 nm, respectively. All features were systematically characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and x-ray powder diffraction. A hybrid fillers system using silver flakes and dendrites as electrically conductive adhesives (ECAs) exhibited excellent overall performance. This good conductivity can be attributed mainly to the synergy between the silver microflakes (5–20 μm sized irregular sheet structures) and dendrites, allowing more conductive pathways to be formed between the fillers. In order to further optimize the overall electrical conductivity, various mixtures of silver microflakes and silver dendrites were tested in ECAs, with results indicating that the highest conductivity was shown when the amounts of silver microflakes, silver dendrites and the polymer matrix were 69.4 wt.% (20.82 vol.%), 0.6 wt.% (0.18 vol.%), and 30.0 wt.% (79.00 vol.%), respectively. The corresponding mass ratio of silver flakes to silver dendrites was 347:3. The resistivity of ECAs reached as low as 1.7 × 10−4 Ω cm.

Analysis of Dendrite Images Formed by Electrochemical Migration in a Semiconductor Sensor

Dendrites were observed in the failure of semiconductor sensor devices. EDX analysis showed that the dendrites grown from bare sensor dice consisted of tin metal. The tin dendrites exhibited massive and dense branches. Dendrites grown from mechanically decapped parts consisted of silver. The silver dendrites exhibited delicate, lace-like structure. Binary and grey scale images of dendrites were analyzed for fractal dimension number and branch density. The tin dendrites had a higher, statistically significant branch density number than silver, due to tin’s more intricate branching pattern. Fractal numbers can be used to differentiate between tin and silver dendrites, even in the absence of EDX analysis equipment.