Silver Nanosuspensions Research Articles

Effects of sepiolite addition to acrylic-latex paint on pull-off adhesion strength in nanosilver-impregnated and thermally-modified beech (Fagus orientalis L.) wood

Sepiolite is a silicate mineral that improves the fire properties in solid wood when mixed with a water-based coating. The present study was carried out to investigate and evaluate the effects of sepiolite addition to acrylic-latex paint on the pull-off adhesion strength, as an important characteristic of paints and finishes used in the modern furniture industry and historical furniture as well for preservation and restoration of heritage objects. Sepiolite was added at the rate of 10%, and brushed onto plain-sawn beech (Fagus orientalis L.) wood specimens, unimpregnated and impregnated with a 400 ppm silver nano-suspension, which were further thermally modified at 185 °C for 4 h. The results showed that thermal modification had a decreasing effect on the pull-off adhesion strength, primarily as a result of the thermal degradation of cell-wall polymers (mostly hemicelluloses). Still, a decreased wettability as a result of condensation and plasticization of lignin was also partially influential. Based on the obtained results,thermal modification was found to have a significant influence on pull-off adhesion strength. Sepiolite addition had a decreasing effectin all treatments, though the effect was not statistically significant in all treatments. The maximum and minimum decreases due to sepiolite addition were observed in the unimpregnated control (21%) and the thermally-modified NS-impregnated (4%) specimens. Other aspects of the sepiolite addition, and further studies that cover different types of paints and coatings, should be evaluated before coming to a final firm conclusion in this regard.

Effects of Nanosilver and Heat Treatment on the Pull-Off Strength of Sealer-Clear Finish in Solid Wood Species.

Pull-off strength is an important property of solid wood, influencing the quality of paints and finishes in the modern furniture industry, as well as in historical furniture and for preservation and restoration of heritage objects. The thermal modification and heat treatment of solid wood have been the most used commercial wood modification techniques over the past decades globally. The effects of heat treatment at two mild temperatures (145 and 185 °C) on the pull-off strength of three common solid wood species, i.e., common beech (Fagus sylvatica L.), black poplar (Populus nigra L.), and silver fir (Abies alba Mill.), were studied in the present research work. The specimens were coated with an unpigmented sealer-clear finish based on an organic solvent. The results demonstrated a positive correlation between the density and pull-off strength in the solid wood species. Heat treatment at 145 °C resulted in an increase in the pull-off strength in all three species, due to the formation of new bonds in the cell-wall polymers. Thermal degradation of the polymers at 185 °C weakened the positive effect of the formation of new bonds, resulting in a largely unchanged pull-off strength in comparison with the control specimens. Impregnation with a silver nano-suspension decreased the pull-off strength in beech specimens. It was concluded that density is the decisive factor in determining the pull-off strength, having a significant positive correlation (R-squared value of 0.89). Heat treatment at lower temperatures is recommended, to increase pull-off strength. Higher temperatures can have a decreasing effect on pull-off strength, due to the thermal degradation of cell-wall polymers.

Antibacterial Effect of Eco-Friendly Silver Nanoparticles and Traditional Techniques on Aged Heritage Textile, Investigated by Dark-Field Microscopy

An improper indoor microclimate has adverse effects on the state of preservation of historical textiles arranged in them, favoring the development of bacteriological microflora. The current study aims to combine traditional and innovative methods for cleaning and preserving a 100-year-old traditional blouse from Bihor, Romania. The material of the blouse was impregnated with 30 and 70 ppm silver nanosuspensions and washed with a substance obtained from boiling natural wood ash (lye). The research goals were to determine the antimicrobial action of lye washing and silver nanoparticles applied to the analyzed textile material and identify the way in which the environmental factors (light) act upon the conservation degree of textile objects impregnated with silver nanoparticles. All these procedures are eco-friendly and do not cause any damage to the constituent material of the fabrics. The use of the hyperspectral imaging technique proved the permeation of both 30 and 70 ppm silver nanosuspensions into the textile, producing changes in the textile’s reflectance spectrum after being treated with them. The results showed anti-bactericidal/fungal properties of both silver nanoparticles and lye. Microbiological analyses revealed that bacterial colonies were reduced to more than 95% in both cases. The antibacterial effect of silver nanoparticles on the textile material of the blouse was maintained throughout the duration of the study, and under normal environmental conditions, the effects would remain active for a long period.

Gum Acacia- and Gum Tragacanth-Coated Silver Nanoparticles: Synthesis, Physiological Stability, In-Vitro, Ex-Vivo and In-Vivo Activity Evaluations

The current research article presents development, characterization, stability, antimicrobial activity, antispasmodic activity and antidiarrheal activity of silver nanoparticles synthesized and stabilized by polymeric coating of gum tragacanth solution. The nanoparticles were developed by a chemical reduction of silver nitrate. The reducing sugars and polysaccharides-based natural polymers such as gum acacia, gum tragacanth, alginates and cellulose derivatives were investigated as both reducing agents and stabilizers of silver nanoparticles. Influence of the molar concentration of silver nitrate, type and concentration of reducing agent on the formation and stability of silver nanoparticles have been investigated in detail. The stability or aggregation behavior of silver nanoparticles when diluted with simulated gastric fluid, simulated intestinal fluid and phosphate buffer saline were investigated to understand the influence of biological fluids on the stability of silver nanoparticles. SNPs in basic buffers were found to be more stable compared to those in acidic buffers. Silver nanoparticles were characterized by UV absorption spectrometry, particle size and zeta potential analyzer, FTIR spectroscopy, differential scanning calorimetry, X-ray diffraction and atomic force microscopy. SNPs were found spherical within 2.5–4 nm as per atomic force microscopic studies. The silver nanoparticles developed from gum tragacanth were better and more stable than those produced by gum acacia. The smaller particle size, low polydispersity index and high zeta potential resulted in silver nanosuspensions stable over a period of six months. The silver nanoparticles were found to exhibit significant antimicrobial, antispasmodic and antidiarrheal activities.

Dose dependent intra-testicular accumulation of silver nanoparticles triggers morphometric changes in seminiferous tubules and Leydig cells and changes the structural integrity of spermatozoa chromatin

Citrate-coated silver nanoparticles were synthesized in one step method using tri-sodium citrate and silver nitrate at pH 6.1. After synthesis, the resulting silver nano-suspension was characterized using UV–visible spectroscopy, dynamic light scattering, high resolution-scanning electron microscopy, energy dispersive x-ray spectroscopy and fourier transform infrared-spectroscopy. The particles were intraperitoneally injected into Swiss albino male mice for a period of one complete spermatogenic cycle. The LD50 was determined following the procedure of Dixon's Up-and-Down method. The intra-testicular level of silver was measured using the technique of inductively coupled plasma-mass spectrometry. The intra-testicular location of accumulated nanoparticles was observed using auto-metallography. The cytology and volume of Leydig cells were assessed and analysed. Following the exposure to silver nanoparticles, it was found that accumulation of nanoparticles inside the seminiferous tubules is a dose-dependent process. The deposition of silver agglomerate induced morphometric changes in the lumen of seminiferous tubules and Leydig cells. The exposure also caused significant changes at the level of structural integrity of sperm chromatin material and variable damages to sperm DNA.

Heat Treatment of Pine Wood: Possible Effect of Impregnation with Silver Nanosuspension

The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat treatment. Impregnation of wood with a 400-ppm silver nanosuspension was carried out under an initial vacuum pressure of 0.07 MPa, followed by a pressure of 0.25 MPa for thirty minutes, before heat treatment. Heat treatment was carried out under hot air at three relatively mild temperatures, 145, 165, and 185 °C. Results showed improvement of some properties in heat-treated wood at 145 °C. This was indicative of the improving impact caused by hornification and irreversible hydrogen bonding in the course of water movements due to heat treatment; significant fluctuations in the intensities of FTIR spectra bands at 1750–1500 cm−1 were corroborating evidence of chemical alterations in hemicellulose polymer. The high mass loss at temperature 185 °C, and the extreme thermal degradation thereof, overcame the improving effects of hornification and formation of irreversible hydrogen bonds, consequently mechanical properties decreased significantly. Interaction of different elements involved made it hard to predict properties in specimens modified at 165 °C. Impregnation of specimens with nanosilver suspension resulted in significant increase of mass loss in specimens heat-treated at 185 °C, and significant fluctuations in properties of specimens heat-treated at 145 °C.

Physical and Mechanical Properties of Thermally-Modified Beech Wood Impregnated with Silver Nano-Suspension and Their Relationship with the Crystallinity of Cellulose.

The aim of this study was to investigate the physical and mechanical properties of thermally modified beech wood impregnated with silver nano-suspension and to examine their relationship with the crystallinity of cellulose. Specimens were impregnated with a 400 ppm nanosilver suspension (NS); at least, 90% of silver nano-particles ranged between 20 and 100 nano-meters. Heat treatment took place in a laboratory oven at three temperatures, namely 145, 165, and 185 °C. Physical properties and mechanical properties of treated wood demonstrated statistically insignificant fluctuations at low temperatures compared to control specimens. On the other hand, an increase of temperature to 185 °C had a significant effect on all properties. Physical properties (volumetric swelling and water absorption) and mechanical properties (MOR and MOE) of treated wood demonstrated statistically insignificant fluctuations at low temperatures compared to control specimens. This degradation ultimately resulted in significant decrease in MOR, impact strength, and physical properties. However, thermal modification at 185 °C did not seem to cause significant fluctuations in MOE and compression strength parallel to grain. As a consequence of the thermal modification, part of amorphous cellulose was changed to crystalline cellulose. At low temperatures an increased crystallinity caused some of the properties to be improved. Crystallinity also demonstrated a decrease in NS-HT185 in comparison to HT185 treatment. TCr indices in specimens thermally treated at 145 °C revealed a significant increase as a result of impregnation with nanosilver suspension. This improvement in TCr index resulted in a noticeable increase in MOR and MOE values. Other properties did not show significant fluctuations, suggesting that the effect of the increased crystallinity and cross-linking in lignin was more than the negative effect of the low cell-wall polymer degradation caused by thermal modification. Change of amorphous cellulose to crystalline cellulose, as well as cross-linking in lignin, partially ameliorated the negative effects of thermal degradation at higher temperatures and therefore, compression parallel to grain and modulus of elasticity did not decrease significantly. Overall, it can be concluded that increased crystallinity and cross-linking in lignin can compensate for some decreased properties caused by thermal modification, but it would be significantly dependent on the temperature under which modification is carried out. Impregnating specimens with silver nano-suspension prior to thermal modification enhanced the effects of thermal modification as a result of improved thermal conductivity.

Anti-oxidant, Cytotoxic and Apoptotic studies of root bark assisted Silver Nanoparticles from Aphanamixis polystachya

The aim of the present investigations was to fabricate and prepare silver nanoparticles from the root bark of Aphanamixis polystachya available in Western Ghats of India and also to assess their antioxidant, cytotoxic and apoptotic activity. The root bark extract of the plant, A. polystachya was used for the green synthesis of silver nanoparticles (AgNP). The AgNP were characterized with the help of UV-Vis Spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), Energy Dispersive X-Ray Analysis (EDAX), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD)and Thermogravimetric analysis. The cytotoxic and apoptotic effects were studied using methanolic extract and AgNP of A. polystachya on human breast cancer cells (MCF-7 and MDA-MB-231). Silver nanosuspension was formulated, and in vitro, antioxidant activity by DPPH assay and Nitric Oxide assay were assessed on a methanolic extract of the root bark and silver nanosuspension of A. polystachya. The percentage cell growth on MCF-7 cells was found to be 39.8, 21.6, 18.0 and 15.6 at 10, 20, 40 and 80µg/ml respectively. In the case of MDA-MB231 cells, the percentage of cell growth was found to be 99.2, 80.0, 67.2 and 54.6 at 10, 20, 40 and 80 µg/ml. Growth inhibition (GI50) of <10µg and >80µg was observed in MCF-7 and MDA-MB231 cell lines. A. polystachya silver nanosuspension significantly enhanced the antiradical potential against nitric oxide scavenging assay (IC50 4.7µg/ml) as compared with methanolic extract of A. polystachya. The formulation of silver nanosuspension of A. polystachya significantly enhanced the antiradical potential as compared with the methanolic extract of root bark of A. polystachya.

Thermally induced dispersive optical bistability in silver nanosuspensions produced by pulsed laser ablation method

The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studied experimentally, using Fabry–Perot and Mach–Zehnder interferometry methods. Two Ag nanosuspensions of different sizes were produced by different fluences of pulsed laser ablation method in distilled water. The pulsed Nd:YAG laser of 7 ns pulse width, 1064 nm wavelength and different fluences was employed to produce Ag nanosuspensions. Experimental observations were performed by an ultraviolet–visible–near infrared spectrophotometry. Structure and size of prepared Ag nanoparticles were diagnosed using transmission electron microscope images. Fabry–Perot and Mach–Zehnder interferometry methods were used to carry out the optical bistability process in prepared Ag nanosuspensions. In two considered interferometers, the obtained phase shifts of the hysteresis loops based on the optical bistability are inversely proportional to the nonlinear refractive index of samples and thickness of Ag nanosuspensions cells. Results indicate that the induced thermal effect of the optical bistability can be tuned by modifying parameters such as the nonlinear refractive index and applied interferometry methods. Hence, a desirable situation for the thermo-optical effects of the optical bistability can be easily realized in Ag nanosuspensions.

Aging of silver nanocolloids in sunlight: particle size has a major influence

Environmental contextTransformation of silver nanoparticles in the environment is an important issue because the form they take directly influences what effect they have. We show that the size of the primary particles of silver nanosuspensions is a major factor determining their evolution under sunlight irradiation (dissolution, formation of nanoseeds and nanoprisms, agglomeration). The persistence of nano-sized silver particles after exposure to sunlight irradiation implies that their ecotoxicological impact will likely last well beyond their introduction in the environment. AbstractThe environmental fate of silver nanoparticles (Ag NPs) is a serious cause for concern with regard to their ecotoxicity. In this study, an aging scenario intended to evaluate the effect of sunlight on three Ag NP suspensions of various particle size was assessed. Suspensions of citrate-stabilised Ag NPs of 20, 60, and 100 nm diameter were aged for a week in a climatic chamber under controlled temperature (40 °C) and irradiation (1.44 W m−2 at 420 nm). The suspensions were analysed by asymmetric flow field flow fractionation – inductively coupled plasma mass spectrometry (AF4-ICP-MS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The AF4-ICP-MS monitoring showed that only a small fraction (10 % at most) of the primary 20 nm particles are converted into multi-faceted particles. Larger particles undergo shape modifications correlated with dissolution (60 nm Ag NPs) and aggregation (100 nm Ag NPs) processes. Silicate structures – supposedly originating from the glassware degradation – stabilise the primary particles. The occurrence of smaller Ag seeds, also associated with silicates, was revealed and quantified by AF4-ICP-MS and confirmed by TEM. The physical fractionation of the particles according to their size provided by AF4, together with the quantitative analysis provided by ICP-MS, helped to determine the role of size in the fate of silver nanoparticles under sunlight exposure.

Contribution of single particle inductively coupled plasma mass spectrometry and asymmetrical flow field-flow fractionation for the characterization of silver nanosuspensions. Comparison with other sizing techniques

Agreements and discrepancies are pointed out in the comparison between spICP-MS, AF4-MALLS-ICP-MS, and other routine techniques for nanoparticle sizing. Calibration protocols play an important role in analytical result quality.

Effects of heat treatment on sound absorption coefficients in nanosilver‐impregnated and normal solid woods

Effects of impregnation with silver nano-suspension as well as heat-treatment on sound absorption coefficients (AC) were studied in tangential direction of five different solid woods based on their importance. AC was measured at two frequencies of 250 and 500 Hz. A 400 ppm nanosuspension was used for the impregnation; silver nanoparticles had a size range of 30-80 nm. Based on the obtained results, the species reacted significantly different in absorbing sound at the two frequencies. Impregnation with nano-suspension substantially decreased AC at the lower frequency of 250 Hz; it did not show any particular trend when AC was measured at the frequency of 500 Hz. Heat treatment significantly increased AC at the frequency of 250 Hz. ACs of mulberry tended to be similar at the two frequencies; in the other four species though, ACs were significantly different. High significant correlations were found in the hardwoods between the ACs measured at the two frequencies.

Preparation of nonaqueous silver nanosuspensions by in situ dispersion of the surface-modified nanoparticles

Abstract In this study, we have developed an in situ dispersion method to prepare nonaqueous Ag nanosuspensions by controlling microdroplet coalescence. A plate-type microchannel was constructed to initiate droplet coalescence. Under optimal conditions, the hexane-based nano-silver suspension with a high particle concentration of 0.47 mol/L and an average particle size of 10 nm could be controllably prepared. The effects of various operation parameters on droplet coalescence and particle dispersion were experimentally investigated. The stability of the dispersed silver nanoparticles in suspensions was significantly enhanced due to the in situ dispersion, and no obvious agglomeration could be observed in the experiments.

Effects of Nanosilver-Impregnation and Heat Treatment on Coating Pulloff Adhesion Strength on Solid Wood

Effects of impregnation with a silver nano-suspension, as well as of heat-treatment, on pull-off adhesion strengths of the coating system on three commercial solid wood species were studied. The wood species included beech, poplar, and fi r. The size range of silver nanoparticles was 30 – 80 nm. The specimens were coated with an un-pigmented sealer and a clear fi nish on the basis of an organic solvent. The results showed that the highest and the lowest pull-off strengths were found in beech specimens heat-treated at 145 °C (5.7 MPa) and in nanosilver-impregnated poplar specimens heat-treated at 185 °C (2.5 MPa), respectively. Impregnation with nanosilver decreased pull-off strength in the case of all species as a result of formation of micro checks in the cell walls caused by the impregnation under high pressure in vessel. Heat-treatment at the temperature lower than 145 °C increased pull-off strength as to the irreversible hydrogen bonding in the course of water movements within the pore system of the cell walls, resulting in extra bonds among cell wall components and higher mechanical properties. However, heat-treatment at the temperature higher than 185 °C signifi cantly decreased the strength as the degradation of hemicellulose and cell wall wood components caused signifi cant decrease in mechanical strength and cell wall thinning. High thermal conductivity coeffi cient of silver intensifi ed the impact of heat-treatment by rapid absorption of heat on the surface of the specimens.

High-speed video study of laser-induced forward transfer of silver nano-suspensions

High-speed video (100 000 fps) is used to examine the behavior of silver nanoparticle suspensions ejected from a donor substrate during laser-induced forward transfer (LIFT) as a function of viscosity, donor film thickness, and voxel area. Both high-speed video and inspection of the post-transferred material indicate dramatic changes in the behavior of the fluid as the viscosity of the nano-suspensions increases from that of inks (∼0.01 Pa·s) to pastes (>100 Pa·s). Over a specific range of viscosities (90–150 Pa·s) and laser fluences (35–65 mJ/cm2), the ejected voxels precisely reproduce the size and shape of the laser spot. This LIFT regime is known as laser decal transfer or LDT. Analysis of the high-speed video indicates that the speeds of the voxels released by the LDT process do not exceed 1 m/s. Such transfer speeds are at least an order of magnitude lower than those associated with other LIFT processes, thus minimizing voxel deformation during flight and upon impact with the receiving substrate. Variation in the threshold fluence for initiating the LDT process is measured as a function of donor film thickness and transfer spot size. Overall, the congruent nature of the silver nanopaste voxels deposited by LDT is unique among non-contact digital printing techniques given its control of the voxel's size and shape, thus allowing partial parallelization of the direct-write process.

Inkjet printing of silver nano-suspensions on ceramic substrates – Sintering temperature effect on electrical properties

The aim of this study is to investigate the effect of sintering temperature on the electrical properties of silver nano-suspensions inkjet printed on sintered alumina tapes. 1.68 × 10−8 Ω m minimum resistivity close to that of silver resistivity was measured after sintering at 700 °C. To our knowledge this value is one of the lowest measured on inkjet printed metallic lines. Optimisation of a commercial silver nano-suspension containing 15 nm silver particles was performed by adding water and ethylene glycol to original suspension, in order to reduce viscosity and allows printing through nozzle with small 21.5 μm diameter. After printing, line sintering was performed at different temperatures. Then, resistivity value was assessed on 14.40 cm line length.