Ag Precursor Research Articles

Novel Heating Elements for Induction Welding of Carbon Fiber/Polyphenylene Sulfide Thermoplastic Composites

Conductive films of carbon nanofibers (CNFs) decorated/coated with metals, either silver (Ag) or nickel (Ni) are fabricated using a solution casting process and used as novel heating elements (HEs) for induction welding of carbon fiber/polyphenylene sulfide (CF/PPS) thermoplastic composites. Prior to making the films, the metal‐coated CNFs are prepared by an electroless plating method using Ag or Ni precursors. A solution of the metal‐coated CNFs is then casted onto a pure PPS film to give a robust conductive film upon solvent evaporation and annealing in an oven at 200 °C. SEM observation and electrical resistivity measurements reveal that the CNFs are successfully coated with the metals which result in a significant decrease of the films’ electrical resistivity. A third type of HE is also fabricated by solution mixing Ag‐coated CNFs and magnetic Fe3O4 nanoparticles. The welding efficiency of the fabricated films is assessed for induction welding of two different types of thermoplastic composites, that is, unidirectional pre‐impregnated 16 plies ​​of CF/PPS compression‐molded in a quasi‐isotropic stacking sequence and 8‐ply of satin weave fabric CF/PPS compression‐molded in a cross‐ply stacking sequence. The mechanical apparent lap shear strength (LSS) of the induction‐welded joints is evaluated for the fabricated HEs and compared with the LSS of joints welded using conventional stainless steel mesh susceptors. Under similar testing conditions, Ag‐coated CNFs HEs lead to the highest LSS with an average value of ≈31.5 MPa. In general, the new HEs result in superior LSS and higher heating rates when compared to the metallic mesh counterparts. The present work offers a new perspective to push the boundaries toward high quality welding of thermoplastic composites using nanomaterials‐based HEs.

AgCl-doped CdSe quantum dots with near-IR photoluminescence.

We report the synthesis of colloidal CdSe quantum dots doped with a novel Ag precursor: AgCl. The addition of AgCl causes dramatic changes in the morphology of synthesized nanocrystals from spherical nanoparticles to tetrapods and finally to large ellipsoidal nanoparticles. Ellipsoidal nanoparticles possess an intensive near-IR photoluminescence ranging up to 0.9 eV (ca. 1400 nm). In this article, we explain the reasons for the formation of the ellipsoidal nanoparticles as well as the peculiarities of the process. The structure, Ag content, and optical properties of quantum dots are also investigated. The optimal conditions for maximizing both the reaction yield and IR photoluminescence quantum yield are found.

Bimetallic Au/Ag Core-Shell Superstructures with Tunable Surface Plasmon Resonance in the Near-Infrared Region and High Performance Surface-Enhanced Raman Scattering.

Due to the larger surface area and the synergistic effects between two noble metals, the bimetallic superstructures exhibit enhanced distinctive optical, catalytic, and photothermal performances and surface-enhanced Raman scattering (SERS) "hot-spot" effect, and thus have attracted great interest in various applications. Compared with the common Pd, Pt hierarchical structures coated onto Au nanoparticles (NPs), easily synthesized via fast autocatalytic surface growth arising from intrinsic properties of Pd and Pt metals, precisely controlling the hierarchical Ag growth onto Au NPs is rarely reported. In our present study, the reducing agent dopamine dithiocarbamate (DDTC) was covalently capped onto the first metal core (Au) to delicately control the growth model of the second metal (Ag). This results in heterogeneous nucleation and growth of Ag precursor on the surface of Au nanorods (NRs), and further formation of cornlike bimetallic Au/Ag core-shell superstructures, which usually cannot be achieved from traditional epitaxial growth. The thickness of the hierarchical Ag shell was finely tuned in a size range from 8 to 22 nm by simply varying the amount of the ratio between Ag ions and DDTC capped on Au NR core. The tunable Ag shell leads to anisotropic bimetallic Au/Ag core-shell superstructures, displaying two distinctive plasmonic resonances in the near-infrared region (NIR). In particular, the longitudinal surface plasmon resonance exhibits a broadly tunable range from 840 to 1277 nm. Additionally, the rich hot spots from obtained Au/Ag superstructures significantly enhance the SERS performance.

Laser assisted synthesis of silver nanoparticles in silica aerogel by supercritical deposition technique

Silver nanoparticles (AgNPs) were synthesized in the pores of silica aerogel by supercritical deposition technique. The sample was impregnated with the precursor Ag(hfac)COD dissolved in supercritical carbon dioxide. Conversion was performed by laser irradiation at the wavelength of 405nm, which matches the plasmon band of AgNPs. The synthesis process was visualized by measuring the extinction spectra in real time. We show that near-spherical AgNPs with the size of few nanometers can be synthesized fast and locally within the irradiated area of the sample. The concentration of AgNPs can be tuned by the time of exposition. The irradiation-assisted conversion is shown to be efficient both under supercritical conditions and after partial or complete depressurization.

A general strategy toward the large-scale synthesis of the noble metal-oxide nanocrystal hybrids with intimate interfacial contact for the catalytic reduction of p-nitrophenol and photocatalytic degradation of pollutants

The construction of noble metal-oxide nanocrystal hybrids (MOHs) with good interface contact, broadly tunable composition and high yield is critical for their application in the advanced fields. In this paper, a general route was developed for constructing MOHs with intimate interfacial contact based on the coordination of an organic agent with multiple kinds of metal precursors. In the synthesis, critic acid, desirable sources for metal nanoparticles (NPs; for example, Ag+ salts), oxides (for example, Zn2+ salts) and ethylene glycol were dissolved in water. After heating at low temperature to produce the precursor gels and subsequent calcination under air, one kind of the ions (Zn2+) was transformed into an oxide (ZnO) in company with the reduction of another ion (Ag+) to generate metal NPs (Ag). Benefitting from the uniform distribution of Ag and Zn precursor in the gels, the Ag/ZnO composites with good interface contact were finally formed. The Ag/ZnO hybrids can be used as effective catalysts for the catalytic reduction of p-nitrophenol and photocatalytic degradation of pollutants. Under optimized conditions, the Ag/ZnO showed a rate approximately 1.5 times higher than that of Degussa P25 TiO2 for the degradation of rhodamine B. The OH· radicals and ·O2 − play predominant roles in the photocatalytic reaction. The Ag/ZnO can also act as an effective catalyst for the reduction of p-nitrophenol with good reuse performance. The present route is also suitable to construct MOHs with other components (Pt/TiO2, Pt/ZnO, etc.). The route is promising to produce MOHs due to the virtues of the easy synthesis process and high yields.

Synthesis of high-purity silver nanorods with tunable plasmonic properties and sensor behavior

Through anisotropic Ag overgrowth on the surface of Au nanobipyramids (AuNBPs), high-purity and size-controlled Ag nanorods (Au/AgNRs) are obtained by a simplified purification process. The diameters of the Au/AgNRs are determined by the size of the as-prepared AuNBPs, and the lengths of the Au/AgNRs are tunable using different amounts of Ag precursor in the growth solution. Surface-enhanced Raman scattering (SERS) studies using Rhodamine-6G (R6G) as a test molecule indicate that the Au/AgNRs have excellent sensing potential. The tunable optical properties and strong electromagnetic effect of the Au/AgNRs, along with their superior SERS signal enhancement, show that Au/AgNRs are promising for further applications in plasmon sensing and biomolecular detection.

Incorporating Ag into Pd/Ni Foam via Cascade Galvanic Replacement to Promote the Methanol Electro-Oxidation Reaction

In this work we intercalated an Ag layer between Pd surface and Ni substrate to form PdAg/Ni ternary architectures to promote the sluggish methanol oxidation reaction (MOR). The PdAg/Ni foam structures were prepared within short time via a cascade galvanic replacement method, in which an Ag precursor partially replaced a commercial Ni foam support first, followed by a Pd precursor partially replacing the formed Ag layer. X-ray diffraction and X-ray photoelectron spectroscopy proofs suggested that a part of the formed Ag was alloyed with the active Pd loaded on the Ni foam surface. It was interestingly found that: 1) incorporation of Ag into Pd/Ni foam could provide significantly improved electrocatalytic activities for the MOR, which mainly originated from the synergistic effects between Pd and Ag in the formed PdAg alloy; 2) the electrocatalytic activity of PdAg/Ni foam was highly dependent on the atomic ratio of Pd to Ag, and among synthesized electrocatalysts the best Pd55Ag45/Ni foam offered a mass activity of 3.3 times of the Pd/Ni binary counterpart; 3) the proposed Pd55Ag45/Ni foam also exhibited excellent performance durability during frequent cyclic voltammetric and simulated startup-shutdown measurements.

Highly dispersed Ag/TiO2via adsorptive self-assembly for bactericidal application

The strong electrostatic adsorption (SEA) technique was used for the preparation of Ag/TiO2by driving the Ag precursor onto the TiO2surface.

Fabrication of High Efficient Silver Nanoparticle Catalyst Supported on Poly(glycidyl methacrylate)–Polyacrylamide

Fabrication of highly efficient silver nanoparticle (Ag NP) catalysts supported on polyacrylamide (PAM)-modified poly(glycidyl methacrylate) (PGMA) microspheres was reported herein, for where PAM was used as the robust anchors because of its abundant amide groups. Well-dispersed Ag NPs with an average diameter of 9.7 nm were obtained on the PGMA–PAM microspheres (Ag NPs@PGMA–PAM). Excellent catalytic activity of Ag NPs@PGMA–PAM was observed in the reduction of 4-nitrophenol using sodium borohydride in water at room temperature, indicated by an activity parameter that was 6–1725 times higher than those reported in the literature. In addition, easy regulation on the size of Ag NPs was achieved through the adjustment on the concentration of the Ag precursor, AgNO3. Therefore, the synthetic method proposed herein was confirmed as being effective for the synthesis of the highly efficient catalyst Ag NPs@PGMA–PAM. This would contribute to the preparation of highly efficient catalyst of supported noble metals an...

Highly Efficient Silver-Cobalt Composite Nanotube Electrocatalysts for Favorable Oxygen Reduction Reaction.

This paper reports the synthesis and characterization of silver-cobalt (AgCo) bimetallic composite nanotubes. Cobalt oxide (Co3O4) nanotubes were fabricated by electrospinning and subsequent calcination in air and then reduced to cobalt (Co) metal nanotubes via further calcination under a H2/Ar atmosphere. As-prepared Co nanotubes were then employed as templates for the following galvanic replacement reaction (GRR) with silver (Ag) precursor (AgNO3), which produced AgCo composite nanotubes. Various AgCo nanotubes were readily synthesized with applying different reaction times for the reduction of Co3O4 nanotubes and GRR. One hour reduction was sufficiently long to convert Co3O4 to Co metal, and 3 h GRR was enough to deposit Ag layer on Co nanotubes. The tube morphology and copresence of Ag and Co in AgCo composite nanotubes were confirmed with SEM, HRTEM, XPS, and XRD analyses. Electroactivity of as-prepared AgCo composite nanotubes was characterized for ORR with rotating disk electrode (RDE) voltammetry. Among differently synthesized AgCo composite nanotubes, the one synthesized via 1 h reduction and 3 h GRR showed the best ORR activity (the most positive onset potential, greatest limiting current density, and highest number of electrons transferred). Furthermore, the ORR performance of the optimized AgCo composite nanotubes was superior compared to pure Co nanotubes, pure Ag nanowires, and bare platinum (Pt). High ethanol tolerance of AgCo composite nanotubes was also compared with the commercial Pt/C and then verified its excellent resistance to ethanol contamination.

Preparation and characterization of sub-20 nm CuX@Ag1 core-shell nanoparticles by changing concentration of silver precursor

Ultrafine Ag-coated Cu (Cu@Ag) nanoparticles (NPs) less than 20 nm in diameter were prepared. After synthesizing ultrafine Cu NPs using a solvothermal method to serve as the core particles, Cu@Ag NPs were fabricated with different initial Ag precursor concentrations, resulting in different thicknesses, densities, and uniformities of Ag shells. The average thickness and density of the Ag shell increased with increasing initial Ag precursor concentration in a Cu:Ag atomic ratio from 6:1 to 1:1. However, excessive Ag precursor concentrations induced homogeneous nucleation and growth of surplus fine pure NPs. Ag dewetting behavior and Cu oxidation in the Cu4@Ag1 NPs were observed, they occurred during heating at 200 and 250 °C, respectively. The electrical resistivities of sintered Cu4@Ag1 films decreased with increasing temperature from 200 to 240 °C. The resistivity after washing the OA and sintering for 60 min at 240 °C in air was measured to be 4.96 × 10−3 Ω cm. The film was sintered in nitrogen using the ink containing non-washed Cu4@Ag1 NPs indicated the lower resistivity of 2.70 × 10−3 Ω cm owing to the non-oxidation atmosphere, although the chemically capped oleylamine in the core-shell NPs hindered the sintering behavior.

One-pot electrodeposition of cobalt flower-decorated silver nanotrees for oxygen reduction reaction

In this paper, we demonstrate a simple fabrication of bimetallic silver (Ag) and cobalt (Co) nanostructures (AgCo) with various Ag to Co relative contents via electrochemical co-deposition. A series of AgCo catalysts was electrodeposited on glassy carbon (GC) electrodes at −0.57V vs. SCE in the deposition solutions, containing Ag precursor, Co precursor, Triton X-100, and 0.3M KNO3 aqueous solution, with various Ag to Co precursor concentration ratios (1:x, x was varied from 3 to 11). The films, deposited with the total deposition charge of 0.042C, were denoted as Ag1Cox. SEM and TEM analyses showed that Ag1Cox formed a structure consisted of flower-like Co grown on tree-like Ag backbones while it had more Co flowers with a greater x. The ORR activities were examined in 0.1M NaOH solution with rotating disk electrode (RDE) voltammetry and Ag1Co7 showed the best catalytic activity. The co-deposition mechanism was further investigated by varying the deposition time of Ag1Co7. At the early stage of deposition, Ag-tree branches were formed predominantly, followed by the growth of flower-like Co nanostructures on the Ag nanotrees: More Co flowers were produced on Ag backbones with longer deposition time, being attributed to both a less negative reduction potential of Ag+ to Ag than Co2+ to Co and promoted Co2+ reduction on the initially formed Ag surface. Ag1Co7 electrodeposited for 200s, consisted of ∼14% Co, showed the greatest ORR catalytic activity which was better or comparable to noble metal Pt.

“One-Pot” Synthesis and Photocatalytic Hydrogen Generation with Nanocrystalline Ag(0)/CaTiO3 and in Situ Mechanistic Studies

We describe a previously not reported “one-pot” synthesis of nanocrystalline Ag(0)/CaTiO3 in aqueous suspension and the following in situ photocatalytic testing in the same suspension to generate hydrogen. The Ag(0)/CaTiO3 showed an enhancement of photocatalytic hydrogen generation rate vs CaTiO3 precursor. The obtained Ag(0)/CaTiO3 photocatalyst was ex situ characterized by XPS, XRD, UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy, and concluded to have metallic silver nanoparticles on the surface of calcium titanate nanocrystals. The three photocatalytic mechanisms in Ag(0)/CaTiO3 were considered: (a) bandgap narrowing in CaTiO3, (b) enhanced electron–hole separation in CaTiO3, and (c) excitation of surface plasmon resonance (SPR) in metallic Ag nanoparticles. In mechanistic studies, photocatalytic suspensions with CaTiO3 precursor, with silver precursor, and with both CaTiO3 and Ag precursors to form Ag(0)/CaTiO3 were illuminated, flash-frozen to 77 K, and charact...

Fabrication and Evaluation of Silver-Indium Catalysts for Electrochemical CO2 Reduction to CO

CO2 has been one of the problematic greenhouse gases, and there have been a lot of efforts to reduce it through capturing, storage, and conversion [1,2]. Ultimately, CO2 needs to be reduced to high energy state fuels including CO. However, CO2 is stable molecule and requires high potential for electrochemical reduction process. Also, hydrogen evolution reaction (HER) occurs at similar potential, thus a selective catalytic reduction is essentially required for electrochemical reduction of CO2 to fuels, in this case CO [3]. So far, Au and Ag catalysts have been studied extensively as candidate catalysts for CO production [4]. Even though Au has provided slightly higher activity, Ag is continuously suggested as a reliable candidate with cost effectiveness. In this work, we developed AgIn catalysts through co-deposition method. It has been known to have large overpotential to HER, which will improve the selectivity of Ag in production of CO over H2. The co-electrodeposition was done through controlling the ratio of amounts of In and Ag precursors in the deposition bath. The fabricated catalysts were analyzed through FE-SEM for surface analysis, EDS to find out Ag and In composition, and XRD to identify the crystal structure and degree of alloy. Also, chronoamperometry (CA) was used to measure and calculate CO2 reduction efficiency using home-made H type cell. Gas chromatography (GC) was used to analyze produced amounts of CO. The results showed that AgIn catalysts was deposited in dendritic morphology and showed much better CO faradaic efficiency than Ag only catalysts. Reference 1. Lu, Q.; Rosen, J.; Zhou, Y.; Hutchings, G. S.; Kimmel, Y. C.; Chen, J. G.; Jiao, F. Nat Commun 2014, 5. 2. Rosen, J.; Hutchings, G. S.; Lu, Q.; Rivera, S.; Zhou, Y.; Vlachos, D. G.; Jiao, F. ACS Catalysis 2015, 5, 4293. 3. Hall, A. S.; Yoon, Y.; Wuttig, A.; Surendranath, Y. Journal of the American Chemical Society 2015, 137, 14834. 4. Zhou, L. Q.; Ling, C.; Jones, M.; Jia, H. Chemical Communications 2015, 51, 17704.

Microstructural, spectroscopic, and antibacterial properties of silver-based hybrid nanostructures biosynthesized using extracts of coriander leaves and seeds

Coriander leaves and seeds have been highly appreciated since ancient times, not only due to their pleasant flavors but also due to their inhibitory activity on food degradation and their beneficial properties for health, both ascribed to their strong antioxidant activity. Recently, it has been shown that coriander leaf extracts can mediate the synthesis of metallic nanoparticles through oxidation/reduction reactions. In the present study, extracts of coriander leaves and seeds have been used as reaction media for the wet chemical synthesis of ultrafine silver nanoparticles and nanoparticle clusters, with urchin- and tree-like shapes, coated by biomolecules (mainly, proteins and polyphenols). In this greener route of nanostructure preparation, the active biocompounds of coriander simultaneously play the roles of reducing and stabilizing agents. The morphological and microstructural studies of the resulting biosynthesized silver nanostructures revealed that the nanostructures prepared with a small concentration of the precursor Ag salt (AgNO3 =5 mM) exhibit an ultrafine size and a narrow size distribution, whereas particles synthesized with high concentrations of the precursor Ag salt (AgNO3 =0.5 M) are polydisperse and formation of supramolecular structures occurs. Fourier transform infrared and Raman spectroscopy studies indicated that the bioreduction of the Ag− ions takes place through their interactions with free amines, carboxylate ions, and hydroxyl groups. As a consequence of such interactions, residues of proteins and polyphenols cap the biosynthesized Ag nanoparticles providing them a hybrid core/shell structure. In addition, these biosynthesized Ag nanomaterials exhibited size-dependent plasmon extinction bands and enhanced bactericidal activities against both Gram-positive and Gram-negative bacteria, displaying minimal inhibitory Ag concentrations lower than typical values reported in the literature for Ag nanoparticles, probably due to the synergy of the bactericidal activities of the Ag nanoparticle cores and their capping ligands.

Organic‐Stabilizer‐Free Polyol Synthesis of Silver Nanowires for Electrode Applications

AbstractThe polyol reduction of a Ag precursor in the presence of an organic stabilizer, such as poly(vinylpyrrolidone), is a widely used method for the production of Ag nanowires (NWs). However, organic capping molecules introduce insulating layers around each NW. Herein we demonstrate that Ag NWs can be produced in high yield without any organic stabilizers simply by introducing trace amounts of NaCl and Fe(NO3)3 during low‐temperature polyol synthesis. The heterogeneous nucleation and growth of Ag NWs on initially formed AgCl particles, combined with oxidative etching of unwanted Ag nanoparticles, resulted in the selective formation of long NWs with an average length of about 40 μm in the absence of a capping or stabilizing effect provided by surface‐adsorbing molecules. These organic‐stabilizer‐free Ag NWs were directly used for the fabrication of high‐performance transparent or stretchable electrodes without a complicated process for the removal of capping molecules from the NW surface.

Organic-Stabilizer-Free Polyol Synthesis of Silver Nanowires for Electrode Applications.

The polyol reduction of a Ag precursor in the presence of an organic stabilizer, such as poly(vinylpyrrolidone), is a widely used method for the production of Ag nanowires (NWs). However, organic capping molecules introduce insulating layers around each NW. Herein we demonstrate that Ag NWs can be produced in high yield without any organic stabilizers simply by introducing trace amounts of NaCl and Fe(NO3 )3 during low-temperature polyol synthesis. The heterogeneous nucleation and growth of Ag NWs on initially formed AgCl particles, combined with oxidative etching of unwanted Ag nanoparticles, resulted in the selective formation of long NWs with an average length of about 40 μm in the absence of a capping or stabilizing effect provided by surface-adsorbing molecules. These organic-stabilizer-free Ag NWs were directly used for the fabrication of high-performance transparent or stretchable electrodes without a complicated process for the removal of capping molecules from the NW surface.

Size‐controlled synthesis of silver nanoparticles from silver mirror reaction in toluene

Size-controlled silver nanoparticles (Ag NPs) with a size of 2–15 nm have been synthesised from silver (Ag) mirror reaction in toluene, which refers to reduction of Ag precursor (Ag–dodecylamine complexes solution) by acetaldehyde (CH3CHO) in the presence of oleic acid (OLA). In this synthesis, the size of Ag NPs was finely tuned by just varying the Ag precursor concentrations (cAg). The addition of OLA can play an important role in stabilising the emerging Ag nuclei. With the OLA/Ag molar ratio at 3:1, the adsorption layer of enough OLA on the surface of the emerging Ag nuclei prevented the direct contact between Ag+ ions and Ag nuclei, and Ag nuclei grew up to their final size by the aggregation mechanism.

Ag-ZnO photocatalyst anchored on carbon nanofibers: Synthesis, characterization, and photocatalytic activities

In this study, a novel photocatalytic and antibacterial Ag-ZnO decorated carbon fiber composite was synthesized by a simple electrospinning method followed by the hydrothermal treatment. Aqueous suspension containing Ag and ZnO precursors with the carbon nanofibers was kept in the hydrothermal process at 140°C for 2h to obtain a homogenous distribution of Ag-ZnO NPs throughout the surface of carbon fibers. The studies of the photocatalytic degradation of methylene blue (MB) and antibacterial performance against Escherichia coli (E. coli) indicated that the as-synthesized composites show enhanced adsorption, visible-light-driven photocatalytic, and antibacterial properties than that of pristine ZnO particles. Therefore, this work provides a facile method of the preparation of carbon fiber based composites which may have potential applications in the environmental fields.

Dopamine-Directed In-Situ and One-Step Synthesis of Au@Ag Core-Shell Nanoparticles Immobilized to a Metal-Organic Framework for Synergistic Catalysis.

We report a facile and general approach to the formation of bimetallic core-shell Au@Ag nanoparticles (NPs) immobilized to metal-organic frameworks (MOFs) via a one-step synthetic route at room temperature. Dopamine (DA) is used as a moderate reductant, which can bind to negatively charged groups of MOFs through electrostatic interaction, and subsequently Au@Ag core-shell NPs are formed by in-situ reduction of the bimetallic Au and Ag precursors step-by-step spontaneously without pre-synthesized seeds. The as-formed Au@Ag core-shell NPs immobilized to MOFs exhibit excellent catalytic activity for the reduction of 4-nitrophenol (4-NPh) by NaBH4 to 4-aminophenol (4-APh) due to a synergistic effect and are highly stable as demonstrated by recycling experiments.