Screen printing of silver nanoparticle suspension for metal interconnects

Silver nanoparticle suspensions were synthesized by chemical reduction method using a formaldehyde reductant. Polyvinyl pyrrolidone (PVP) of two different molecular weights (M.W.=8,000 and 29,000) was used as a stabilizer for the suspensions. PVP of a smaller molecular weight could produce silver suspensions of nanoparticle size around 20 nm. Water-based conductive silver inks with different silver concentrations were prepared and tested for suitability for screen printing. We have successfully printed silver metal lines on glass substrates using a 400 mesh screen-mask with 60wt.% silver ink prepared in this study. Curing at a low temperature of 200 °C for an hour was found sufficient to reach the lowest resistivity value with the synthesized ink. For a line with a width and thickness of 0.5 mm and 2.12 μm, respectively, it exhibited a resistivity of 3.3×10⁻⁵ Ω·cm, which could serve as conducting lines for various electronic applications.     

Mechanical and dielectric properties of 3D printed highly porous ceramics fabricated via stable and durable gel ink

A novel, efficient, versatile strategy was carried out to fabricate highly porous ceramic parts based on the combination of strong colloidal gel ink fabricated with high boiling point organic solvents and DIW technique. The preparation and optimization of inks and the effect of heating temperature on the phase composition, microstructure, mechanical properties and dielectric properties of ceramic parts were systematically investigated. The strong colloidal ink exhibits excellent ambient stability and printability. The sintering temperatures bring about the evolution of phases, structural mechanical properties and dielectric properties of ceramic parts. Ultimately, Si₂N₂O single wall ceramic parts with a frame density of 1.07?1.14 g/cm³ and an apparent porosity of 53.13 ± 1.29% were successful fabricated. The dielectric constant and dielectric loss of Si₂N₂O sample (1650℃) are only 4.24 and 0.0049, respectively. This strategy provides a reference for in-situ synthesis of high-performance porous ceramic components based on the DIW.     

Fabrication of polycrystalline silver nanowires via reversed micelle with amphiphilic diblock copolymer and aluminum oxide template at controlled temperature

An amphiphilic diblock copolymer consisting of methyl methacrylate and methacrylic acid was synthesized using atom transfer radical polymerization via a hydrolysis process design. Silver nanoparticles were synthesized by a reverse micelle method using the synthesized diblock copolymer as a surfactant. Silver nanoparticle‐embedded fibers were then fabricated using an anodic aluminum oxide template. Silver nanoparticle‐embedded porous polymer fibers were fabricated by adding unreactive diphenyl sulfide in polymer matrix. They are expected to be applied to recyclable metal catalyst systems. After sintering of silver nanoparticle‐embedded polymer fibers at a relatively lower temperature, silver nanowires were fabricated. Moreover, the surfactant effect on both self assembly of nanoparticle clusters and silver nanowires surface smoothness were compared with the previously reported results. Silver nanoparticles coordinated amphiphilic copolymer was found to reveal higher thermal resistance. POLYM. COMPOS., 31:1352–1359, 2010. © 2009 Society of Plastics Engineers     

Synthesis of silver nanoparticles using reducing agents obtained from natural sources (Rumex hymenosepalus extracts)

We have synthesized silver nanoparticles from silver nitrate solutions using extracts of Rumex hymenosepalus, a plant widely found in a large region in North America, as reducing agent. This plant is known to be rich in antioxidant molecules which we use as reducing agents. Silver nanoparticles grow in a single-step method, at room temperature, and with no addition of external energy. The nanoparticles have been characterized by ultraviolet-visible spectroscopy and transmission electron microscopy, as a function of the ratio of silver ions to reducing agent molecules. The nanoparticle diameters are in the range of 2 to 40 nm. High-resolution transmission electron microscopy and fast Fourier transform analysis show that two kinds of crystal structures are obtained: face-centered cubic and hexagonal.     

Research of antibacterial activity on silver containing yttria-stabilized–zirconia bioceramic

An antibacterial bioceramic, silver containing yttria-stabilized zirconia (YSZ), was fabricated by sintering for dental prosthesis applications. The biocompatibility, hemocompatibility and antibacterial ability of the silver containing YSZ were evaluated. The addition of silver did not cause tetragonal phase to transform into monoclinic phase and the silver containing YSZ maintained an excellent mechanical property. Furthermore, the sintered silver containing YSZ showed no toxicity and possessed a good antibacterial ability against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) cell.     

Flame synthesis of mixed tin‐silver‐copper nanopowders and conductive coatings

The single‐step direct synthesis of tin‐silver‐copper nanopowders and nanostructured coatings using the flame‐based high‐temperature reducing jet (HTRJ) process is reported. Nanostructured coatings were deposited and sintered within the HTRJ reactor to study the effect of reductive sintering temperature on their electrical conductivity and surface morphology. Although the ultimate application of these nanoparticles is in printed electronics, which requires dispersing them as stable inks before depositing and sintering them, our approach of direct deposition from the gas phase provides an upper limit on the conductivity achievable with a given composition. The directly deposited coatings had high electrical conductivity, including a value of 2 × 10⁶ S/m for 36 wt % Cu‐40 wt % Ag‐24 wt % Sn sintered at 200°C. This is twice the conductivity of a pure silver coating prepared under similar conditions. Moreover, similarly high electrical conductivity was achieved using only 20% Ag with sintering at 300°C. © 2015 American Institute of Chemical Engineers AIChE J, 62: 408–414, 2016     

Antibacterial activity of photocatalytic electrospun titania nanofiber mats and solution-blown soy protein nanofiber mats decorated with silver nanoparticles

Highly porous photocatalytic titania nanoparticle decorated nanofibers were fabricated by electrospinning nylon 6 nanofibers onto flexible substrates and electrospraying TiO₂ nanoparticles onto them. Film morphology and crystalline phase were measured by SEM and XRD. The titania films showed excellent photokilling capabilities against E. coli colonies and photodegradation of methylene blue under moderately weak UV exposure (≤ 0.6 mW/cm² on a 15-cm illumination distance). In addition, solution blowing was used to form soy protein-containing nanofibers which were decorated with silver nanoparticles. These nanofibers demonstrated significant antibacterial activity against E. coli colonies without exposure to UV light. The nano-textured materials developed in this work can find economically viable applications in water purification technology and in biotechnology. The two methods of nanofiber production employed in this work differ in their rate with electrospinning being much slower than the solution blowing. The electrospun nanofiber mats are denser than the solution-blown ones due to a smaller inter-fiber pore size. The antibacterial activity of the two materials produced (electrospun titania nanoparticle decorated nanofibers and silver-nanoparticle-decorated solution-blown nanofibers) are complimentary, as the materials can be effective with and without UV light, respectively.     

Characterization of silver and silver/nickel composite particles prepared by spray pyrolysis

Pure silver and silver/nickel composite particles were prepared by spray pyrolysis of aqueous solutions of AgNO₃, and mixed salts of AgNO₃ and Ni(NO₃)₂·6H₂O, respectively. In the case of pure silver, reduction to metallic silver and subsequent sintering to highly spherical and dense particles took place immediately and almost simultaneously once favorable conditions for the former were imposed, irrespective of the nature of the carrier gas. For the composite particles, the high rates of reduction and sintering of the silver were still maintained, while crystallization of the silver, and the reduction and sintering of the nickel were considerably retarded, compared to the spray pyrolysis of each pure salt. Once the counterpart salt was added, the size of the composite particles increased compared to that of each pure metallic particles, but it was little affected by the furnace set temperature, the residence time and the molar ratio of the two precursor salts. Within single particles, an increase in either the temperature or the residence time caused segregation—silver in the shells and nickel in the cores—and improved the particles' surface smoothness and sphericity accordingly.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

Controllable fabrication of PS/Ag core-shell-shaped nanostructures

In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures. Ultimately, the optimum parameters were obtained through a series of experiments, and well-dispersed, uniformly coated PS/Ag core-shell-shaped nanostructures were successfully fabricated. The formation mechanism of the PS/Ag core-shell-shaped nanostructures was also explained.     

An in situ study on the coalescence of monolayer-protected Au-Ag nanoparticle deposits upon heating

The structural evolution of thiolate-protected nanoparticles of gold, silver, and their alloys with various Au/Ag ratios (3:1, 1:1, and 1:3) upon heating was investigated by means of in situ synchrotron radiation X-ray diffraction. The relationships between the coalescence and composition of nanoparticles, as well as the surfactant reactions, were clarified. Experimental results show that there existed a critical temperature ranging from 120°C to 164°C, above which the tiny broad X-ray diffraction peaks became sharp and strong due to particle coalescence. The coalescence temperatures for alloy nanoparticle deposits were clearly lower than those for pure metals, which can be ascribed to the rivalry between the thermodynamic effect due to alloying and the interactions between surface-assembled layers and the surface atoms of the nanoparticles. The strong affinity of thiolates to Ag and thus complex interactions give rise to a greater energy barrier for the coalescence of nanoparticles into the bulk and subsequent high coalescence temperature. The influences of particle coalescence on the optical and electrical properties of the nanoparticle deposits were also explored.     

Synthesis of silver nanoparticles and antibacterial property of silk fabrics treated by silver nanoparticles

A silver nanoparticle solution was prepared in one step by mixing AgNO₃ and a multi-amino compound (RSD-NH₂) solution under ambient condition. RSD-NH₂ was in-house synthesized by methacrylate and polyethylene polyamine in methanol, which has abundant amino and imino groups. However, the characterization of silver nanoparticles indicated that these nanoparticles are easy to agglomerate in solution. Therefore, an in situ synthesis method of silver nanoparticles on the silk fabrics was developed. The examined results confirmed that the in situ synthesized silver nanoparticles were evenly distributed on the surface of fibers. The inhibition zone test and the antibacterial rate demonstrated that the finished fabrics have an excellent antibacterial property against Staphylococcus aureus and Escherichia coli. Moreover, the nanosilver-treated silk fabrics were laundered 0, 5, 10, 20, and 50 times and still retained the exceptional antibacterial property. When the treated fabrics were washed 50 times, the antibacterial rate is more than 97.43% for S. aureus and 99.86% for E. coli. The excellent laundering durability may be attributed to the tight binding between silver nanoparticles and silk fibers through the in situ synthesis. This method provides an economic method to enhance the antibacterial capability of silk fabrics with good resistance to washings.     

Lightweight silver@carbon microsphere@graphene (Ag@CMS@GR) composite materials for highly efficiency electromagnetic interference shielding properties

In this article, lightweight silver@carbon microsphere@graphene (Ag@CMS@GR) composite materials were fabricated. First, carbon microsphere (CMS) was prepared by redox hydrothermal method in the presence of FeCl₃ and polyvinyl alcohol. Next, on the surface, silver was deposited to form Ag@CMS particles. And finally, the graphene sheets were added to connect Ag@CMS particles to obtain Ag@CMS@GR composites. Because of the silver nanoparticle may form a conductive pathway, Ag@CMS with relative high content of silver nanoparticles show superior EMI shielding properties. Next, graphene was introduced into Ag@CMS with relative low content of silver particles to form Ag@CMS@GR composites, which is helpful for decreasing the apparent density of composites to around 1.01 g·cm⁻³. And the composites also show good EMI shielding properties. The highest SE and specific SE values of Ag@CMS@GR reached 39.26 dB and 38.87 dB·cm³·g⁻¹ with 5 wt % graphene content. The EMI shielding mechanism of Ag@CMS@GR composites was discussed. It can be potentially used for lightweight EMI shielding applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48459.     

Colloidal silver nanoparticles modified electrode and its application to the electroanalysis of Cytochrome c

A colloidal silver nanoparticles (CSNs) chemically modified electrode was prepared and its application to the electroanalysis of Cytochrome c (Cyt. c) was studied. The CSNs were prepared by reduction of AgNO₃ with NaBH₄, and were stabilized by oleate. They could be efficiently immobilized on the surface of a silver electrode. The result showed that the CSNs could clearly enhance the electron transfer process between Cyt. c and the electrode compared with bulk silver electrode. Linear sweep voltammetric measurement of Cyt. c at the chemical modified electrode indicated that the oxidative peak current of Cyt. c was linear to its concentration ranging from 8.0 nmol L⁻¹ to 3.0 μmol L⁻¹ with the calculated detection limit was about 2.6 nmol L⁻¹. The direct electrochemistry of Cyt. c was also studied by cyclic voltammetry.     

Green synthesis of protein capped silver nanoparticles from phytopathogenic fungus Macrophomina phaseolina (Tassi) Goid with antimicrobial properties against multidrug-resistant bacteria

In recent years, green synthesis of nanoparticles, i.e., synthesizing nanoparticles using biological sources like bacteria, algae, fungus, or plant extracts have attracted much attention due to its environment-friendly and economic aspects. The present study demonstrates an eco-friendly and low-cost method of biosynthesis of silver nanoparticles using cell-free filtrate of phytopathogenic fungus Macrophomina phaseolina. UV-visible spectrum showed a peak at 450 nm corresponding to the plasmon absorbance of silver nanoparticles. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) revealed the presence of spherical silver nanoparticles of the size range 5 to 40 nm, most of these being 16 to 20 nm in diameter. X-ray diffraction (XRD) spectrum of the nanoparticles exhibited 2θ values corresponding to silver nanoparticles. These nanoparticles were found to be naturally protein coated. SDS-PAGE analysis showed the presence of an 85-kDa protein band responsible for capping and stabilization of the silver nanoparticles. Antimicrobial activities of the silver nanoparticles against human as well as plant pathogenic multidrug-resistant bacteria were assayed. The particles showed inhibitory effect on the growth kinetics of human and plant bacteria. Furthermore, the genotoxic potential of the silver nanoparticles with increasing concentrations was evaluated by DNA fragmentation studies using plasmid DNA.     

The Anti-Fasciolasis Properties of Silver Nanoparticles Produced by Trichoderma harzianum and Their Improvement of the Anti-Fasciolasis Drug Triclabendazole

Recently, new strains of Fasciola demonstrated drug resistance, which increased the need for new drugs or improvement of the present drugs. Nanotechnology is expected to open some new opportunities to fight and prevent diseases using an atomic scale tailoring of materials. The ability to uncover the structure and function of biosystems at the nanoscale, stimulates research leading to improvement in biology, biotechnology, medicine and healthcare. The size of nanomaterials is similar to that of most biological molecules and structures; therefore, nanomaterials can be useful for both in vivo and in vitro biomedical research and applications. Therefore, this work aimed to isolate fungal strains from Taif soil samples, which have the ability to synthesize silver nanoparticles. The fungus Trichoderma harzianum, when challenged with silver nitrate solution, accumulated silver nanoparticles (AgNBs) on the surface of its cell wall in 72 h. These nanoparticles, dislodged by ultrasonication, showed an absorption peak at 420 nm in a UV-visible spectrum, corresponding to the plasmon resonance of silver nanoparticles. The transmission electron micrographs of dislodged nanoparticles in aqueous solution showed the production of reasonably monodisperse silver nanoparticles (average particle size: 4.66 nm) by the fungus. The percentage of non hatching eggs treated with the Triclabendazole drug was 69.67%, while this percentage increased to 89.67% in combination with drug and AgNPs.     

Enhanced photoluminescence property and mechanism of Eu3+‐doped tellurite glasses by the silver and gold nanoparticles

In this work, the silver or gold nanoparticle single‐existing and co‐existing tellurite glasses doped with Eu³⁺ were prepared, and the influence of gold or silver nanoparticles on the photoluminescence of tellurite glasses doped with Eu³⁺ were investigated. The photoluminescence of tellurite glasses doped with Eu³⁺ was enhanced by the surface plasmon absorption of gold or silver nanoparticles, and the maximum luminescence enhancement factors caused by the silver and gold nanoparticles are 4.8 and 3.5 factors, respectively. The differentiation of luminescence enhancement mechanisms caused by the gold or silver nanoparticles was demonstrated. The enhanced luminescence mechanism of the Au nanoparticle single‐existing tellurite glasses doped with Eu³⁺ was from the increasing of radiative decays rate caused by the Au nanoparticles. The excitation field enhancement caused by the Ag nanoparticles was responsible for the luminescence enhancement of the Ag single‐existing tellurite glasses doped with Eu³⁺. About 4.2‐factor luminescence enhancement was observed in the Ag and Au nanoparticle co‐existing tellurite glasses doped with Eu³⁺, which is attributed to the increasing of radiative decays rate and excitation field enhancement caused by the Au and Ag nanoparticles.     

Method for controlling surface energies of paper substrates to create paper-based printed electronics

The creation of practical paper-based electronics requires secured conductivity with conductive silver tracks fabricated on a paper substrate. Various paper properties were explored for obtaining the key parameters intimately related to printed circuit qualities. A comparison of the resistance of silver tracks printed by ink-jet with a tetradecane-based ink of silver nanoparticles among four substrates—photo-quality ink-jet paper, matte-type ink-jet paper, coated offset paper, and uncoated laboratory sheets—implied the importance of pore size, porosity, surface roughness, and surface energy. Paper surface layers with small pore sizes and high porosities produced highly conductive, narrow silver tracks because of quick ink absorption, as observed in the photo-quality ink-jet paper. The surface roughness induced a high resistance to peel-off force at the expense of conductivity, and this improvement in the peel-off resistance is considered to be achieved because of the anchor effect of silver nanoparticle inks which fell into dents present on the rough paper surfaces. The widths of the silver tracks were significantly reduced by controlling the surface energies of the paper sheets. This tendency was remarkable, especially for uncoated laboratory sheets, and thus the conductivities of the silver tracks were successfully improved.     

Rheological Characterization of Aqueous 3Y‐TZP Inks Optimized for Direct Thermal Ink‐Jet Printing of Ceramic Components

Aqueous 3Y‐TZP inks with solid contents of 22 and 27 vol% were used for fabricating three‐dimensional ceramic components by the direct ink‐jet printing process (DIP). The DIP fabrication was realized using a thermal ink‐jet (TIJ) printing system. Despite the different physical properties of the inks, both inks were successfully ejected and deposited. To define the optimum window of the ink properties required for a stable printing operation, both ceramic inks as well as a typical TIJ ink were characterized in terms of particle size distribution, zeta potential, viscosity, surface tension, and the inverse Ohnesorge number (Oh^?1). Moreover, single drops of all inks were deposited and analyzed by scanning electron microscopy (SEM) to examine the form and integrity of the ejected drops. Demonstration objects (a base with curved channels and a sample molar tooth) were DIP fabricated using both of the ceramic inks. These objects show the potentials of the DIP process for ceramics manufacturing particularly by using TIJ printing systems.     

Surface modification of TPGS-b-(PCL-ran-PGA) nanoparticles with polyethyleneimine as a co-delivery system of TRAIL and endostatin for cervical cancer gene therapy

The efficient delivery of therapeutic genes into cells of interest is a critical challenge to broad application of non-viral vector systems. In this research, a novel TPGS-b-(PCL-ran-PGA) nanoparticle modified with polyethyleneimine was applied to be a vector of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and endostatin for cervical cancer gene therapy. Firstly, a novel biodegradable copolymer, TPGS-b-(PCL-ran-PGA), was synthesized and characterized. The nanoparticles were fabricated by an emulsion/solvent evaporation method and then further modified with polyethyleneimine (PEI) carrying TRAIL and/or endostatin genes. The uptake of pIRES2-EGFP and/or pDsRED nanoparticles by HeLa cells were observed by fluorescence microscopy and confocal laser scanning microscopy. The cell viability of TRAIL/endostatin-loaded nanoparticles in HeLa cells was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. Severe combined immunodeficient mice carrying HeLa tumor xenografts were treated in groups of six including phosphate-buffered saline control, blank TPGS-b-(PCL-ran-PGA) nanoparticles, blank TPGS-b-(PCL-ran-PGA)/PEI nanoparticles, and three types of gene nanoparticles. The activity was assessed using average increase in survival time, body weight, and solid tumor volume. All the specimens were then prepared as formalin-fixed and paraffin-embedded tissue sections for hematoxylin-eosin staining. The data showed that the nanoparticles could efficiently deliver plasmids into HeLa cells. The cytotoxicity of the HeLa cells was significantly increased by TRAIL/endostatin-loaded nanoparticles when compared with control groups. The use of TPGS in combination with TRAIL and endostatin had synergistic antitumor effects. In conclusion, the TRAIL/endostatin-loaded nanoparticles offer considerable potential as an ideal candidate for in vivo cancer gene delivery.