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(a) Scheme of the nanofabrication approach developed in this work to prepare an ordered array of Au−Ag nanotubes in a planar configuration. (1) Growth of Ag nanowires over nanograted silicon structures and (2) transformation of the solid Ag nanowires into Au− Ag nanotubes by means of galvanic replacement using HAuCl 4 . (b) Cross-section and (c) plane-view scanning electron microscope images (SEM) showing the Ag nanowire arrays as-grown over the nanopatterned silicon substrate. (d) TEM micrograph of an Ag nanowire and (e) the associated selected-area electron diffraction pattern indexed according to the crystallographic database of facecentered cubic silver (JCPDS no. 004-0783).
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Hollow bimetallic nanostructures are of great importance for various applications. Understanding the fundamental mechanisms occurring during the synthesis of such nanomaterials by wet chemistry remains very challenging. This Article reports a mechanistic study on the galvanic replacement reaction between planar arrays of silver nanowires grown site...
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... However, the reported studies were limited to the comprehension of the conversion process of zero- dimensional nanostructures. Here, we apply for the first time galvanic replacement in gold(III) chloride (HAuCl 4 ) to an array of highly ordered silver nanowires grown over a nanopatterned silicon substrate ( Figure 1a). Two protocols are explored allowing synthesizing a broad panel of gold−silver hollow nanostructures. ...
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... Journal of Physical Chemistry C Article ■ RESULTS AND DISCUSSION Growth of the Ag Nanowires Template. Figure 1b and c shows SEM micrographs of the Ag nanowire arrays used as template for the growth of Au−Ag nanotubes. The nanowires are ∼150 nm in diameter and periodically separated by a gap of about 70 nm; the length of the nanowires is defined by the length of the nanograting structures, which may reach several centimeters depending on the size of the substrate. ...
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... In this study, the length of the nanowires was fixed to 1 cm. The TEM micrograph (Figure 1d) and the associated selected area electron diffraction (SAED) pattern (Figure 1e) reveal the granular morphology and the polycrystalline structure of the nanowires. In addition, the presence of continuous rings in the SAED pattern indicates that the Ag crystallites forming the nanowire do not exhibit a preferential crystallographic orientation. ...
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... In this study, the length of the nanowires was fixed to 1 cm. The TEM micrograph (Figure 1d) and the associated selected area electron diffraction (SAED) pattern (Figure 1e) reveal the granular morphology and the polycrystalline structure of the nanowires. In addition, the presence of continuous rings in the SAED pattern indicates that the Ag crystallites forming the nanowire do not exhibit a preferential crystallographic orientation. ...
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... After 5 min of conversion, one can clearly remark a change in the morphology of the nanowires, and large colloids are formed on the surface of the sample (Figure 2a). In addition, the surface of the nanowires becomes extremely rough (Figure 2b) as compared to the one before treatment (Figure 1c), and they are constituted of spherical nanodomes; in addition, some pinholes can be seen at the surface of the nanoobjects. From the cross- section view of these nanostructures, one can conclude that they were partially carved and they did not fully transform into nanotubes ( Figure 2c). ...
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... the other hand, the morphology and roughness of the nanowires (Figure 2e) are found to be very similar to the ones observed in case of 5 min of treatment, but the pinholes are no longer visible. As demonstrated by X-ray photoelectron spectroscopy, the formed cubes are the products of AgCl precipitation ( Figure S1). The AgCl precipitation can be easily removed by rinsing the samples in distilled water saturated with NaCl ( Figure S2). ...
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... compared to single-walled nano- tubes, the fabrication of double-walled nanotubes requires additional deposition and treatment steps. For the synthesis of the first shell, Ag nanowires are deposited by magnetron sputtering for 40 s (Figure 7a, step 1). After their growth, the Ag nanowires are treated for 5 min in a solution of HAuCl 4 with 1 mM of concentration saturated with NaCl ( Figure 7a, step 2). ...
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In this paper, we systematically investigated the effects of concentration and amount of silver nanowires (AgNWs) suspension on the optoelectronic properties and microstructures of flexible transparent conductive films (FTCFs) composed of AgNWs with an average diameter of about 25 nm and length of 15.5 μm. AgNW–FTCFs were prepared on polyethylene t...
Citations
... Due to their antimicrobial activity, Ag and Cu based nanomaterials play an important role in the treatment of several issues caused by bacteria and viruses. The green synthesis of Ag-Cu bimetallic nanoparticles and their biomedical and catalytic applications have been extensively reported [7].However, there are efficient synthesizing methods and important properties such as dielectrics, electrochemical and thermal characteristics that still need to be investigated. The aim of this study is to prepare Silver-Copper bimetallic nanoparticles and study their structural and optical behaviour. ...
Silver-based nanomaterials have proven interesting and promising material for numerous applications such as biosensor, antimicrobial, anticancer agent, catalyst, food and water treatment, energy storage devices etc. In this study, nanoparticles of Silver and Copper were prepared by chemical reduction method, using hydrazine hydrate and Sodium borohydride as reducing agent. Fine powder of Ag-Cu nanoparticles (NPs)was obtained. The structural analysis of the sample wasdone using Powder XRD, SEM and TEM images and particle size analysis by DLS.The chemical purity and the elemental compositions of synthesized NPs were studied using SEM-EDX. Optical properties of the Ag-Cu NPs were analyzed using UV-DRS spectrum and FTIR spectrum. PXRD reveals that the NPs are highly crystalline in nature. The average crystallite size is30 nm. SEM and TEM images confirm the spherical morphology, and the particle size is in nm. The DLS-particle size analyzer shows the size distribution of most of the NPs ranging from 9 nm to 100 nm. The EDX analysis reveals the percentage of elemental composition as 14.71, 9.06 and 76.23 for silver, copper and oxygen respectively. UV-DRS spectrum shows the absorption maximum occur at 371 nm. Due to the synergistic effect of silver and copper, there is blue shift in the absorption maximum. The IR spectrum discloses the metal oxide bond in the synthesized NPs.
... The GRR between silver nanowires and chloroauric acid was directly observed using in situ transmission X-ray microscopy (TXM), providing intuitive visual evidence for the formation of hollow gold-silver nanotube structures [24]. Tessier et al. [25] pointed out that based on the GRR between silver nanowires and chloroaurate is an important way to realize highly ordered bimetallic Junqi Tang ...
Silver nanowire (AgNWs) is a typical precious metal nanowire with excellent electrical conductivity, light transmittance, and flexural resistance, which can be widely used in the fields of catalysis, optoelectronics, flexible display devices and biomedicine. We have prepared gold-silver bimetallic nanostructures based on AgNWs as templates and controlled gold nanoparticles coating on the surface of AgNWs by chemical reduction method. The catalytic efficacy of this gold-silver bimetallic nanowires (AuAg BNWs) for the hydroreduction of 4-nitrophenol to 4-aminophenol was analyzed using this nanostructure as a nanocatalyst. Due to the large number of small-sized gold nanoparticles on the surface of the nanostructure, it shows good catalytic activity, and the apparent rate constants and the turnover frequency reach 0.108− 1 min and 43.41 h− 1, respectively. In addition, the surface enhanced Raman scattering (SERS) properties of this AuAg BNWs structure were analyzed using crystal violet as a probe molecule. Because the plasmonic-enhanced localized electric field effect, the nanostructure also exhibited good SERS enhanced properties. Based on these studies, it is advantageous to the preparation of gold-silver bimetallic nanostructures and their applications in catalysis and SERS sensing.
... The temperature of the chemical replacement reaction may affect the morphology and content of the Au nanostars deposited on the surface of the steel plate, thereby influencing the performance of the SERS substrate [20,21]. In order to assess the impact of this factor, SEM and Raman spectroscopy of R6G were used to analyze a series of Au nanostar substrates created through immersion in HAuCl 4 solution with a concentration of 2.54 mM at 5 °C, 15 °C, 25 °C, 35 °C, and 45 °C for 3 h. ...
... It is not difficult to find through Fig. 6a-e that the Au nanostars was easy to form tentacles at low temperatures. This may be due to the fact that at low temperatures, the number of gold nanoparticles produced at the beginning of the reaction is small and the molecular motion force is low, thus inhibiting the collision nucleation between gold nanoparticles and making it easier to adsorb and adhere to form tentacles [21]. On the contrary, at high temperature, the chemical reaction is fast, thus producing a large number of fast-moving gold nanoparticles in a short time, and the collision nucleation between the particles directly forms large size gold nanoprogenitor nuclei. ...
The aim of this study is to develop a simple but rapid method for the determination of foodborne pathogens in complex matrices (beverages) by surface enhanced Raman spectroscopy (SERS) combined with Au nanostar solid-phase substrates. The star-shaped singlet Au nanostructure was formed on the surface of a stainless steel sheet by chemical replacement reaction. Rhodamine 6G verified the sensitivity and reproducibility of this substrate, and the relative standard deviations of the SERS intensity at 1312 cm⁻¹, 1364 cm⁻¹, and 1510 cm⁻¹ displacements were 3.40%, 5.64%, and 3.48%, respectively. By detecting four pathogens in beverage samples on Au nanostar substrates, the utility of the SERS assay was demonstrated, while the combination of principal component analysis (PCA) and hierarchical cluster analysis (HCA) further enabled the isolation and identification of pathogens. The results of spiked beverages were validated in conventional culture identification and Vitek 2 Compact biochemical identification system experiments. Thus, this research demonstrated that Au nanostar substrates can be effectively utilized for the recognition of pathogenic bacteria and have immense promise to advance the progress of quick detection of foodborne pathogens and food safety.
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... Among them, nanoporous materials show superior properties due to their interconnected nanostructures and large surface areas [17][18][19]. A myriad of techniques is available for the synthesis of porous nanostructures [20,21]. Among them, dealloying has received particular attention due to its simple methodology [17,22]. ...
Nanostructured noble metal thin films are highly studied for their interesting plasmonic properties. The latter can be effectively used for the detection of small and highly diluted molecules by the surface-enhanced Raman scattering (SERS) effect. Regardless of impressive detection limits achieved, synthesis complexity and the high cost of gold restrict its use in devices. Here, we report on a novel two-step approach that combines the deposition of a silver–aluminum thin film with dealloying to design and fabricate efficient SERS platforms. The magnetron sputtering technique was used for the deposition of the alloy thin film to be dealloyed. After dealloying, the resulting silver nanoporous structures revealed two degrees of porosity: macroporosity, associated to the initial alloy morphology, and nanoporosity, related to the dealloying step. The resulting nanoporous columnar structure was finely optimized by tuning deposition (i.e., the alloy chemical composition) and dealloying (i.e., dealloying media) parameters to reach the best SERS properties. These are reported for samples dealloyed in HCl and with 30 atom % of silver at the initial state with a detection limit down to 10 ⁻¹⁰ mol·L ⁻¹ for a solution of rhodamine B.
... This finding is most likely due to the significant difference between the concentrations of Cu 2+ (200 ppm) and Ag + (2 ppm) ions. As the kinetics of redox replacement reactions are significantly affected by the concentration of the more-noble element [50], the markedly higher concentration of Cu 2+ ions compared to Ag + ions facilitates the reaction rate of redox replacement reaction between Cu 2+ ions and Zn, and consequently more Cu was deposited on the electrode. Moreover, in order to investigate the effects of increased EDRR cycles on the composition of Cu/Zn/Ag coatings, the EDS analysis of EDRR samples with 400 cycles has been conducted on two new samples prepared using the same E 1 , t 1 and t 2 as sample S1 and S2. ...
The electrodeposition-redox replacement (EDRR) method was investigated for the preparation of two types of functional surfaces. A synthetic solution simulating Zn process solution containing 65 g/L Zn, 200 ppm Cu, 2 ppm Ag and 10 g/L H2SO4 was used as the source for creating functional surfaces EDRR experiments. The effects of operating parameters such as deposition potential (E1), deposition time (t1), and redox replacement time (t2) have been comprehensively studied. When E1 was selected to deposit Zn as the sacrificial metal, coherent Cu/Zn/Ag coatings with various chemical compositions, crystalline phases and surface morphology were obtained depending on the selected t1 and t2. The Cu/Zn/Ag coatings also exhibited competitive corrosion resistance (Ecorr = −683 to −634 mV vs. Hg/Hg2SO4, jcorr = 1.6–4.1 μA/cm²) when compared to those detailed in the literature. In contrast, when E1 was selected so that Cu was the sacrificial metal, separated Cu/Ag particles with controllable chemical composition, particle size (82–170 nm) and tunable surface plasmon resonance (SPR) behavior were formed through the variation of t1 and t2. In addition to the ability to tailor different functionalities for the surfaces from the same solutions, the process was performed in a single electrochemical cell without the addition of any complexing agents. Overall, these promising results demonstrated the versatility of the EDRR method to create various high value-added functional materials from complex hydrometallurgical solutions which contain multiple metal impurities.
... Nanoscale galvanic replacement (NGR) is one of the promising areas of chemical nanomaterials, that has been developing rapidly in the last decade [1][2][3][4][5][6][7][8][9][10][11]. This is due to relative simplicity of the practical implementation of the galvanic replacement and their ample capabilities to yield functional nanostructured materials on metal [1,2,4] and semiconductor [6,10] surfaces. ...
... This is due to relative simplicity of the practical implementation of the galvanic replacement and their ample capabilities to yield functional nanostructured materials on metal [1,2,4] and semiconductor [6,10] surfaces. There are two following main types of NGR: (1) deposition of nanoparticles on macro-surfaces [1,[6][7][8][9][10]12,13], and (2) fabrication of metal nanostructures [2][3][4][5]11,14,15], preferably mono-, bimetal (core@shell, hollow) and framework nanoparticles. The morphology of these deposits and the geometry of the nanostructures are determined by thermodynamic and kinetic parameters, which are interdependent and change in the course of galvanic replacement reactions. ...
This mini-review summarizes the publications of the last decade dedicated to the study of
the formation of metal nanostructures by galvanic replacement reaction in a non-aqueous
medium (organic solvents and ionic liquids). It is shown that among modern methods of
surface modification of nanostructures, galvanic replacement reaction belongs to one of
the most effective ones in terms of preparing new materials and application of metal films.
However, controlled formation of nanostructures is not always possible in aqueous solutions
due to the occurrence of side chemical and electrochemical processes. The latter can be
prevented in non-aqueous media, making them promising in chemistry of nanomaterials.
A significant difference between the formation of M1/M2 nanostructures, where either
electronegative (Mg, Al, Si, Zn, Co) or electropositive (Cu, Ag) elements serve as a
sacrificial surface (M1), is illustrated by the galvanic replacement reactions occurring in
organic solvents (ethanol and organic aprotic solvents) and ionic liquids. The data on the
influence of the nature of non-aqueous media and the basic parameters of the galvanic
replacement process (solution composition, temperature and duration) on the deposits
morphology and the geometry of the deposited particles are reported. It is shown that the
galvanic replacement method in a non-aqueous medium promotes the controlled deposition
of metallic nanoparticles on the macro- and nanosurfaces of the substrate and allows
obtaining nanomaterials with predetermined functional properties.
... Nowadays, silver nanowires synthesized by polyol method are the most popular precursor template in various synthetic routes of gold nanotubes [24][25][26][27][28]. On the one hand, they have perfect crystal matching and do not need additional steps to remove the template after the reaction. ...
In this paper, the optical properties and local electric field distribution of transverse plasmon mode of a single pentagonal gold nanotube are studied for the first time by the discrete dipole approximation (DDA). The theoretical simulation results of pentagonal gold nanotube are closer to the actual experiment compared with circular section. We find that the transverse plasmon peaks can be exponentially red shift from visible to infrared region via controlling the inner diameter. In addition, the transverse plasmon peak firstly blue shifts and then red shifts in the visible region with the increase of outer diameter. Further analysis shows that the spectra red shift with the increase of outer diameters when scattering is dominant. Local electric field analysis reveals that thin tube wall is easier to excite higher-order plasmons modes. Localized surface plasmon resonance (LSPR) peaks of gold nanotube mainly come from dipole resonance and quadrupole resonance. The surface charges of inner and outer tube walls are changed by tuning the inner diameter and outer diameter parameters of pentagonal gold nanotube. The selective controlling transverse plasmon spectra of gold nanotube are realized, which is of great significance to the study of optical properties of gold nanotube and the application of molecular detection and biological imaging.
... GRR is a redox process involving the oxidation of one metal, often called a sacrificial template, by ions of another metal in the solution. 17 The reaction is controlled by the difference in the standard reduction potentials of the two metal/metal ion couples involved. The first galvanic replacement reaction at the nanoscale was demonstrated with the Ag−Au system in 2002. ...
Hollow metallic capsules are of great interest given the large specific surface area and optical, electrical, and catalytic properties. To expand the possibilities of application and research of inorganic nano- and microparticles, new methodologies are being developed for obtaining metallic or multimetallic particles. For the first time, we propose a galvanic replacement reaction (GRR) with liquid gallium hydrocolloid to obtain a library of bi- and trimetallic functional capsules. The properties of the capsules are determined by the synthesis conditions, salt precursor, and stabilizer, providing control over the surface morphology and metal distribution. Furthermore, the resulting metallic capsules were tested for various functional properties, e.g., antimicrobial activity, and tailored for drug delivery systems. A wide variety of functional materials can be generated due to the ability to synthesize multimetallic capsules and incorporating a broad range of dopants.
... Different synthetic approaches could lead to the discovery of different silver nanowires with new properties. For example, there are high purity cylindrical silver nanowires selectively prepared by kinetic control of hydrothermal conditions [58], Ag nanowire arrays grown on nanograted silicon structures [59], pentagonal Ag nanowires prepared by the polyol process and so on. For the synthesis of silver nanowires, a large number of routes have been developed in recent years. ...
This review (with 106 references) summarizes the latest progress in the synthesis, properties and biomedical applications of gold nanotubes (AuNTs). Following an introduction into the field, a first large section covers two popular AuNTs synthesis methods. The hard template method introduces anodic alumina oxide template (AAO) and track-etched membranes (TeMs), while the sacrificial template method based on galvanic replacement introduces bimetallic, trimetallic AuNTs and AuNT-semiconductor hybrid materials. Then, the factors affecting the morphology of AuNTs are discussed. The next section covers their unique surface plasmon resonance (SPR), surface-enhanced Raman scattering (SERS) and their catalytic properties. This is followed by overviews on the applications of AuNTs in biosensors, protein transportation, photothermal therapy and imaging. Several tables are presented that give an overview on the wealth of synthetic methods, morphology factors and biological application. A concluding section summarizes the current status, addresses current challenges and gives an outlook on potential applications of AuNTs in biochemical detection and drug delivery.
Graphical abstract
... The galvanic replacement reaction, a class of sacrificial template methods, is a redox process between two metals with distinct reduction potentials. The reaction provides a simple and versatile route to fabricate a range of advanced multifunctional NPs with plasmonic cavities and porous walls [Chee et al. 2017;El Mel et al. 2016;Rycenga et al. 2009]. ...
... The DOPA-mediated reduction of gold ions took place progressively to produce gold shell morphologies (Fig. 3). Produced Ag/Au alloy nanostructures have nanobump morphologies because the galvanic replacement took place at individual Ag seeds on SiO 2 NP surfaces [El Mel et al. 2016;Lee et al. 2017]. As the galvanic reaction proceeded further, Ag seeds were depleted off and subsequently produced a Au NS to surround a SiO 2 nanosphere template. ...
We have prepared genuinely hollow Au nanourchins (HANUs) using SiO2 nanoparticles (NPs) as hard templates. Ag-SiO2 NPs were fabricated via amine-assisted reduction. Then, Au nanourchins (ANUs) were synthesized by the galvanic replacement reaction of Ag-SiO2 NPs using l-3,4-dihydroxyphenylalanine (DOPA) as a reductant and a capping agent. The silica cores of ANUs were etched using HF (aq) to produce HANUs. Measuring cross sections, we have found that HANUs have well-defined hollow morphologies. Compared with nanourchins made via DOPA-mediated reduction, HANUs hardly contain residual silver because very tiny silver seeds were used as the initiation sites of galvanic replacement. HANUs have revealed large surface-enhanced Raman scattering enhancement and a significant photothermal effect under a weak illumination.
Graphical Abstract
