Silver Microparticles Research Articles

Recyclability‐by‐design of Printed Electronics by Low‐Temperature Sintering of Silver Microparticles

AbstractA low‐temperature sintering mechanism of silver microparticles is established and used to enable the design‐for‐recycling of printed electronics. The formation of necks during the initial phase sintering of precipitated and atomized silver microparticles is studied. Temperature‐ and time‐dependent in‐situ analyses indicate the existence of a mobile silver species that provides efficient mass transport. The activation energy of neck formation identifies silver ion formation as the rate‐limiting step of low‐temperature silver sintering. It is demonstrated that resistivities of 271 times that of bulk silver can be attained after 40 minutes at 150°C. Low‐temperature sintering not only reduces the energy required during thermal treatment but it yields layers that are suitable for recycling, too. The resulting layers have conductive necks that are mechanically weak enough to be broken during recycling. Printed layers are redispersed and the recycled silver powder is reused without loss of the electrical performance in new prints. Their conductivities are industrially relevant, which makes this recyclability‐by‐design approach promising for manufacturing more sustainable printed electronics.

Metallization of leaf-derived lignocellulose scaffolds for high-performance flexible electronics and oligodynamic disinfection

Vascular tubules in natural leaves form quasi-fractal networks that can be metallized. Traditional metallization techniques for these lignocellulose structures are complex, involving metal sputtering, nanoparticle solutions, or multiple chemical pretreatments. Here we present a novel, facile, and reliable method for metallizing leaf-derived lignocellulose scaffolds using silver microparticles. The method achieves properties on-par with the state-of-the-art, such as broadband optical transmittance of over 80%, sheet resistances below 1 Ω/sq., and a current-carrying capacity exceeding 6 A over a 2.5 × 2.5 cm² quasi-fractal electrode. We also demonstrate copper electrodeposition as a cost-effective approach towards fabricating such conductive, biomimetic quasi-fractals. Additionally, we show that these metallized structures can effectively eliminate pathogenic microorganisms like fecal coliforms and E. coli, which are bacterial indicators of microbiological contamination of water. We finally show that these oligodynamic properties can be significantly enhanced with a small externally applied voltage, indicating the noteworthy potential of such structures for water purification and pollution control.

Liquid metal-enhanced composite conductive ink with improved electrical stability and durability for flexible electronics

For flexible electronics, conductive ink is a critical material with diverse applications. However, conventional inks, like those based on nano-silver, are expensive and result in printed patterns with limited conductivity stability. To address these limitations and enhance overall electrical performance, stability, and durability, this study developed a novel composite conductive ink incorporating liquid metal and silver microparticles. We fabricated conductive patterns and extensively investigated the sintering process, focusing on how liquid metal content and sintering techniques affect the resulting patterns' electrical performance and stability. Our findings reveal that incorporating liquid metal introduces a slight trade-off in the initial conductivity. However, subsequent thermal and hot-press sintering treatments significantly improve conductivity, with hot-press sintering leading to the most pronounced enhancement. Furthermore, the addition of liquid metal substantially bolsters the electrical stability of the patterns. Notably, conductive patterns fabricated using a 1:1 mass ratio of the ink exhibit ∆R/R0 values of only 1.72 and 0.432 after 5000 bending cycles, following thermal and hot-press sintering, respectively. This highlights the significant improvement in electrical stability and durability achieved by incorporating liquid metal into the conductive ink.

The Highly Durable Antibacterial Gel-like Coatings for Textiles.

Hospital-acquired infections are considered a priority for public health systems since they pose a significant burden for society. High-touch surfaces of healthcare centers, including textiles, provide a suitable environment for pathogenic bacteria to grow, necessitating incorporating effective antibacterial agents into textiles. This paper introduces a highly durable antibacterial gel-like solution, Silver Shell™ finish, which contains chitosan-bound silver chloride microparticles. The study investigates the coating's environmental impact, health risks, and durability during repeated washing. The structure of the Silver Shell™ finish was studied using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The TEM images showed a core-shell structure, with chitosan forming a protective shell around groupings of silver microparticles. The field-emission scanning electron microscopy (FESEM) demonstrated the uniform deposition of Silver Shell™ on the surfaces of the fabrics. AATCC Test Method 100 was employed to quantitatively analyze the antibacterial properties of the fabrics coated with silver microparticles. Two types of bacteria, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), were used in this study. The antibacterial results showed that after 75 wash cycles, a 100% reduction for both S. aureus and E. coli in the coated samples using crosslinking agents was observed. The coated samples without a crosslinking agent exhibited 99.88% and 99.81% reductions for S. aureus and E. coli after 50 washing cycles. To compare the antibacterial properties toward non-pathogenic and pathogenic strains of the same species, MG1655 model E. coli strain (ATCC 29213) and a multidrug-resistant clinical isolate were used. The results showed the antibacterial efficiency of the Silver ShellTM solution (up to 99.99% reduction) coated on cotton fabric. AATCC-147 was performed to investigate the coated samples' leaching properties and the crosslinking agent's effects against S. aureus and E. coli. All coated samples demonstrated remarkable antibacterial efficacy, even after 75 wash cycles. The crosslinking agent facilitated durable attachment between the silver microparticles and cotton substrate, minimizing the release of particles from the fabrics. Color measurements were conducted to assess the color differences resulting from the coating process. The results indicated fixation values of 44%, 32%, and 28% following 25, 50, and 75 washing cycles, respectively.

Copper and silver microparticles for high-performance conductive inks in electronic chip shielding

The development of conductive inks has increased in recent years, especially for applications in electronic devices. Inks can be applied by spraying on the IoT chips and forming a shield against electromagnetic interference (EMI). This technology is called conformal shielding, which reduces EMI on the component. Micro and nanoparticles of copper or silver are often used in the composition of the inks, but the high cost of silver and the oxidation of copper limit the application. Another option is using particles with a copper core covered by silver (Cu–Ag), as it overcomes both limitations of the pure metals mentioned. So, there is an opportunity to use these conductive inks as an alternative to traditional EMI shielding methods such as metal cans, sputtering coating, and electroless nickel. Therefore, this work synthesized Cu–Ag particles to use in a conductive ink applied by spray coating. The film's resistivity and shielding effectiveness (SE) were measured. The morphology, size, and chemical composition of the particles were evaluated. The particles presented an irregular shape with complete and partial coverage of silver over copper. The ink showed an electrical resistivity of ∼10−04 Ω cm at 200 °C in sintering. It was also tested on different substrates with better adhesion to PET. The shielding efficiency was −44 dB according to the ASTM d4935 norm. A painting on the chips with a low-thickness film covering all modules demonstrated suitability to conformal shielding.

Self-adhesive, stretchable waterborne polyurethane-based flexible film as wearable conformal strain sensor for motion and health monitoring

Wearable tensile strain sensors are of great importance in both motion monitoring and next-generation, personalized health diagnostics. The accuracy, reliability and stability of the signals obtained from these sensors are significantly dependent on the conformal contact between the flexible sensor and the skin surface. In this study, we have developed a flexible double-layer film as a wearable tensile strain sensor by a simple solution-blending method and a layer-by-layer spraying method. D-sorbitol was incorporated into a waterborne polyurethane (WPU) emulsion to enhance film adhesion, achieving a strength of 7.91 N/m, and to disrupt hydrogen bonds between the WPU chains. This disruption facilitates more straightforward conformational changes of the chains under stress, thereby substantially enhancing the mechanical flexibility of the film. The sensing layer was subsequently constructed by spraying silver microparticles, exhibiting extremely high sensitivity (gauge factor = 103.01) over a 19.3% strain range. This sensor can effectively monitor joint motions and subtle muscle movements as tensile strain sensors.

Enhancing of ofloxacin oxidation current through the overvoltage position displacement using carbon paste electrode modified by silver particles: Analytical application in water

In this study, a modified carbon paste electrode with silver particles (Ag–CPE) was used for ofloxacin (OFL) detection with enhanced over-potential for low concentrations. The incorporation of silver particles on carbon paste was confirmed by scanning electron microscopy. Electrochemical behavior of ofloxacin at carbon paste electrode (CPE) and Ag–CPE was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The OFL interaction with Ag+ was derived from the oxidation of silver during anodic scan has been investigated under different conditions. The strong binding affinity of Ag+ with 1.0 ​× ​10−5 ​M OFL resulted in the upward shift of the OFL potential, which shifted potential from 0.85 to 0.95 ​V. The modification of carbon paste electrode by silver microparticles has enhanced the oxidation current with over-potential of OFL at low concentrations without a decrease of the current. The influence of the sweeping potential range on OFL oxidation was optimized. The calibration curve for ofloxacin at Ag–CPE is linear in the range from 4.0 ​× ​10−6 to 1.0 ​× ​10−3 ​M, and the detection limit was 9.47 ​× ​10−7 ​M. Possible effects of inorganic ions and organic substances were investigated but did not cause any significant interferences. Furthermore, the repeatability, reproducibility, and stability of the present sensor were done with satisfactory results. The proposed method was successfully applied to OFL determination in tap water samples.

Ag nanoflowers as single-particle, multi-wavelength SERS active platforms

Surface-enhanced Raman spectroscopy (SERS) has been successfully employed in several fields of interest such as biosensing, in-situ catalysis studies, and archeology, in this regard, the production of nanostructures for the SERS effect is the core of scientific research. Up to now a lot of different types of metallic nanoparticles and nanosurfaces were produced in trying to match the theoretical enhancement of 1014. This work presents a novel SERS active substrate with a high enhancement and a wide range of exciting wavelengths. Specifically, we synthesize Ag Nanoflowers (AgNFs), spherical silver micro-particles with a diameter of 1.7 μm and a nano-rough surface. When AgNFs are deposited onto a substrate thanks to their dimension is possible, to find a single isolated micro-particle and study the signal enhancement of an analyte adsorbed onto its surface. The SERS properties at a single-particle level were studied using a standard molecule 4-mercaptobenzoic acid (4-MBA). Thanks to their extinction spectrum, expanding throughout the visible range, we were able to systematically study the enhancement for several single Ag NFs with 532, 633, and 785 nm laser wavelengths, finding a maximum enhancement factor in the order of 108- 109. This result is of great interest because demonstrates that such nanomaterial can be easily used to study every kind of analyte at low concentrations with any exciting wavelength thus avoiding other undesired optical phenomena, such as luminescence or degradation of the analyte.

Influence of the Heat Transfer Process on the Electrical and Mechanical Properties of Flexible Silver Conductors on Textiles.

With the increase in the popularity of wearable and integrated electronics, a proper way to manufacture electronics on textiles is needed. This study aims to analyze the effect of different parameters of the heat transfer process on the electrical and mechanical properties of flexible electronics made on textiles, presenting it as a viable method of producing such electronics. Wires made from different composites based on silver microparticles and an insulating layer were screen-printed on a release film. Then, they were transferred onto a polyester cloth using heat transfer with different parameters. Research showed that different heat transfer parameters could influence the electrical properties of screen-printed wires, changing their resistance between -15% and +150%, making it imperative to adjust those properties depending on the materials used. Changes in the settings of heat transfer also influence mechanical properties, increasing adhesion between layers at higher temperatures. This study shows the importance of tailoring heat transfer properties and the differences that these properties make.

The Influence of Magnetic Fields on the Electrical Conductivity of Membranes based on Cotton Fabric, Honey, and Microparticles of Carbonyl Iron and Silver

In the present work, we report that the manufacturing of new environmentally friendly and low-cost materials with electrical conductivity can be roughly and finely tuned by an external magnetic field for technical and biomedical applications. With this aim in mind, we prepared three types of membranes based on cotton fabric impregnated with bee honey, carbonyl iron microparticles (CI), and silver microparticles (SmP). In order to study the influence of the metal particles and the magnetic field on the electrical conductivity of membranes, electrical devices were made. Using the "volt-amperometric" method, it was found that the electrical conductivity of the membranes is influenced by the mass ratio (mCI: mSmP) and by the B values of the magnetic flux density. It was observed that in the absence of an external magnetic field, adding microparticles of carbonyl iron mixed with silver microparticles in mass ratios (mCI: mSmP) of 1:0, 1:0.5, and 1:1 causes the electrical conductivity of the membranes based on cotton fabrics impregnated with honey to increase 2.05, 4.62, and 7.52 times, respectively, compared with that of the membrane based on cotton fabrics impregnated with honey alone. When applying a magnetic field, the electrical conductivity of the membranes with microparticles of carbonyl iron and silver increases with increasing magnetic flux density B. We conclude that the membranes are very good candidates for the fabrication of devices to be used in biomedical applications due to the possibility of remote, magnetically induced release of the bioactive compounds from honey and silver microparticles into the area of interest during medical treatment.

Biosynthesis of Silver Nano/Micro-Particles Using <i>Sambiloto</i> (<i>Andrographis paniculata</i>) Leaves Extract: Effect of AgNO<sub>3</sub> Solution Concentrations

Silver nano/micro particles have been successfully produced via biosynthesis using sambiloto (Andrographis paniculata) leaves extract as the reductor agent. The obejctive of current was to study the effect of four different AgNO3 solution concentrations (i.e. 0.0125, 0.025, 0.05, 0.075 M) on the production of silver nano/micro particles via biosynthtesis. The sambiloto extract concentration used in this study was 0.5% w/v. The silver nano/micro particles produced via biosynthesis was characterized using UV-Vis spectrophotometer and Scanning Electron Microscopy (SEM). The UV-Vis analysis results showed that absorbance peaks for all four samples were observed at wavelength around 450 nm, which can be attributed to the presence silver nano/microparticles. The absorbance peak values for all samples were 0.1115; 0.0876; 0.052; 0.0424 for AgNO3 solution concentration of 0.0125; 0.025; 0.05; 0.075 M, respectively. The UV-Vis analysis results could also qualitatively conclude that the size of silver nano/micro particles produced at lower AgNO3 solution concentration were smaller than the size of silver nano/micro particles produced at higher AgNO3 solution concentration. In the other hand, SEM image showed that the size of silver particles prepared using AgNO3 solution concentration of 0.075 M was in the range of 5 – 10 μm, hence it can be called silver micro-particles. It was assumed that the size of silver nano/micro particles produced at higher AgNO3 solution concentration were bigger than the size of silver nano/micro particles produced at lower AgNO3 solution concentration.

Magnetizable Membranes Based on Cotton Microfibers, Honey, Carbonyl Iron, and Silver Nanoparticles: Effects of Static Magnetic Fields and Medium-Frequency Electric Fields on Electrical Properties

In this work, we present the manufacturing process of magnetizable membranes based on cotton microfibers, honey, carbonyl iron, and three different concentrations of silver microparticles. Each membrane is used as a dielectric material for the fabrication of electrical devices. By using the plane capacitor method, the electrical capacitance and dielectric loss tangent are measured in a medium-frequency alternating field superimposed on a static magnetic field. From the obtained data, the time constants of the devices, the components of complex dielectric permittivity, and the electrical conductivity of the membranes as a function of the electric field frequency and magnetic flux density can be extracted. The results show that the obtained membranes can be useful for the fabrication of low-cost and environmentally friendly magneto-active membranes that are required for various technical and biomedical applications.

Preparation of activated carbon fibers (ACF) impregnated with metallic silver particles from cotton-woven wastes and its performance as an antibacterial agent

Although activated carbon has been the subject of numerous research applications in water treatment, purification, catalysis, etc., its production is mainly focused on granular and powder presentations due to the commonly used raw materials (e.g., wood, phenolic resin, etc.). Herein, we report an easily established methodology for preparing activated carbon fibers (ACF) using cotton-woven wastes as raw material under chemical activation with H3PO4. We tested different experimental conditions between the activating agent and the cotton fabrics using a randomized-block experimental design with the specific surface area of the activated fibers as the response variable. A highly microporous structure was obtained with an average specific surface area of 1060 m2/g and pore size of 17 Å. The fibers were later impregnated with metallic silver particles using an immersion process in AgNO3 solutions followed by drying and a thermal decomposition to promote the nucleation and precipitation of non-regular shaped silver particles with sizes on the micro and nanoscale within the fiber’s porous. The novel material showed a strong antibacterial effect and a complete inhibition of bacterial culture growth with silver contents as low as 200 ppm. • Cotton-woven wastes are suitable precursors for activated carbon fibers production. • Esterification of cellulose-based raw materials is the activation mechanism. • Production of activated carbon fibers with a specific surface area up to 1200 m 2 /g. • Considerably dimension and structural stability reduction from the original fiber. • High antibacterial activity due to the presence of metallic silver microparticles.

Stretchable printed circuit board integrated with Ag-nanowire-based electrodes and organic transistors toward imperceptible electrophysiological sensing

Wearable devices with excellent mechanical stretchability, comparable to that of human skin, are highly desirable for preventing discomfort and dermatitis. Composite material systems that use metal particles and elastomers are promising for realizing intrinsic stretchable electrodes with high conductivity and enhancing mechanical flexibility of wearable devices. However, it is challenging to achieve stable device performance under mechanical deformation using stretchable electrodes. In this study, stretchable electrodes with enhanced conductivity and stretchability are developed and integrated with organic transistors to fabricate a stretchable printed circuit board (PCB) that acts as a voltage amplifier under large strains. The stretchable electrodes are composed of silver microparticles, a small quantity of silver nanowires (AgNWs), and an elastomer matrix, which demonstrated a conductivity of 8.5 × 103 S cm−1 at a curing temperature of 100 °C. The observed conductivity was 3.6 times higher than that of electrodes without AgNWs. Owing to the addition of AgNWs, the durability strain in cyclic stretching increased from 10% to 75%; the increment can be attributed to the suppression of microcrack propagation. Moreover, the proposed stretchable PCB was applied to fabricate a voltage amplifier, which enabled stable amplification by 14 times under 0% and 75% strain owing to a mechanical rigid-soft patterning designed into the substrate according to the rigidness of the mounted components. The stabilization technologies in the proposed stretchable PCB can contribute to the development of wearable devices for long-term usage to assist the early detection of diseases.

Probing the Conductive and Tribological Behaviors of Solid Additives in Multiply Alkylated Cyclopentanes for Sliding Electrical Contact.

Sliding electrical contacts need to be lubricated by conductive lubricants to perform low energy dissipation, high reliability, and long service life. This work studied the thermal stability, anti-corrosion capacity, and conductive, and tribological behaviors of several solid additives in multiply alkylated cyclopentanes (MACs), including carbon nanotubes (CNTs), multilayer graphene (MG), and silver microparticles. The results showed that all the additives possessed favorable thermal stability and corrosion resistance; in particular, CNTs and MG exhibited lower and more stable electrical contact resistance (ECR) and better lubricity abilities than Ag microparticles. Moreover, based on the characterization of the worn surfaces and the film thickness calculation, the favorable conductive and tribological properties of CNTs and MG were related to the high conductivity and specific structure of the additives and the good chemical inertness of MACs.

Investigation of the influence of the modified packaging plastic film on the mayonnaise quality parameters during storage

The emergence of new polymer materials, available antimicrobial drugs and modification methods create favorable prerequisites for the invention of a new generation of packaging. It should be related with scientific justification and experimental confirmation of their effectiveness and complete safety. The research of influence of packaging polyethylene film modified with silver and zinc microparticles on organoleptic, physico-chemical and microbiological indices of mayonnaise quality during its storage has been performed. The packaging film was obtained on an extruder XQI-800 using silver salt and zinc oxide. The content of particles in the modified polyethylene film was silver - 38 mg/kg, zinc - 1020 mg/kg. It is shown that mayonnaise stored in a modified plastic film for 3 months at room temperature in a place exposed to light meets the requirements of microbiological safety: there are no bacteria of the Escherichia coli group (ESCH) (coliforms), pathogenic microorganisms, including salmonella, as well as yeast and mold. The organoleptic characteristics and acidity index of mayonnaise were found to be in full compliance with the standardized values during storage, and the dynamics of changes in lipid peroxide number was significantly less intensive than those established for mayonnaise stored in unmodified polyethylene film. The degree of migration of silver and zinc particles into mayonnaise during its storage for 3 months was found to be 23.7% and 16% respectively. The results obtained allow us to evaluate the modified film as a perspective packaging material.

Silver Microparticle-Enhanced Laser-Induced Breakdown Spectroscopy.

Enhanced emission was observed in the laser-induced breakdown spectroscopy (LIBS) atomic emission spectra of bacterial cells deposited upon a nitrocellulose filtration medium in the presence of one-micron silver microparticles. A deposition chamber was constructed that allowed a uniform coating of the filter with trace amounts of silver microparticles. Masses from 10 to 100 μg were deposited in a circular area of 52.18 mm2. A 30 s deposition time was used for all experiments resulting in a mass deposition of 39 μg ± 17 μg. This mass coverage on the filter provided for a single laser shot silver mass ablation of 3.3 ng per laser shot. LIBS spectra were acquired with single-shot 1064 nm laser pulses from specimens of E. coli, M. smegmatis, and E. cloacae deposited on both microparticle-coated filters and blank filters. An increase in emission intensity for all elements detected in the bacterial LIBS spectrum as well as the carbon emission which derives in part from the nitrocellulose filter medium was observed due to the ablation with silver microparticles relative to the intensity measured from the ablation of bacterial cells deposited on a blank filter. The ratio of emission intensity with microparticles to emission intensity without microparticles was measured to be 3.6 for phosphorus, 4.5 for magnesium, 5.3 for calcium, 4.0 for sodium, and 1.2 for carbon. An enhancement in LIBS emission intensity in the range of 1–10 was observed for all the spectra, with an average enhancement ratio of 4.3.

Template Electrochemical Synthesis of Hydroxyapatite on a Titania–Silver Composite Surface for Potential Use in Implantology

Modern materials science, both in terms of functional and structural materials, is actively developing towards the creation of structures with a given ordering. A wide range of methods involves ordering the structure according to a template shape. Template synthesis is one of the mots wide-spread approaches. Most often, the template synthesis method is implemented under conditions of limiting the growth of the phase due to the geometry of the template. In the present work, a template electrochemical method is considered for calcium hydroxyapatite (HAp) coating synthesis, based on the replication of the planar template texture during deposition. In this case, the template is an array of silver microparticles immobilized on an electrically conductive substrate, separated by an insulator layer. The developed approach is similar to the mask metallization widely used in planar technology. In this work, the possibility of the template pulsed electrodeposition of ceramics rather than metal is shown using HAp as an example. This approach is interesting for materials science, in particular, for obtaining micro-ordered hydroxyapatite structures—a crystallochemical analogue of the inorganic bone tissue component—on the surface of bone implants, which can be implemented to improve their biomedical characteristics. As a result of our study, we experimentally determined the conditions for obtaining the composite coating TiO2/Ag/Ca10(PO4)6(OH)2 with controlled phase structure, topology and localization of components on the surface, which was confirmed by Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and X-ray Diffraction (SEM, EDS and XRD). The absence of cytotoxicity for the osteoblast-like cells of the developed coating was revealed by cytological tests.

Preparation of Activated Carbon Fibers (Acf) Impregnated with Silver Microparticles from Cotton-Woven Wastes and its Performance as an Antibacterial Agent

Preparation of Activated Carbon Fibers (Acf) Impregnated with Silver Microparticles from Cotton-Woven Wastes and its Performance as an Antibacterial Agent

Fabrication of Popcorn-Like Silver Microparticles Film Array for in Situ Detection of Plasmonic Catalytic Reaction by Sers Spectroscopy Technique

Fabrication of Popcorn-Like Silver Microparticles Film Array for in Situ Detection of Plasmonic Catalytic Reaction by Sers Spectroscopy Technique