Composite Silver Nanoparticles Research Articles

Determination of Photothermal and EMI Shielding Efficiency of Graphene–Silver Nanoparticle Composites Prepared under Low-Dose Gamma Irradiation

Silver nanoparticles (Ag NPs) have been produced by low-dose (1–20 kGy) gamma irradiation of silver nitrate in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene). The large surface area of those graphene-based materials combined with the presence of oxygen-containing functional groups on the surface provided successful nucleation and growth of Ag nanoparticles, which resulted in a uniformly covered graphene surface. The obtained Ag nanoparticles were spherical with a predominant size distribution of 10–50 nm for graphene oxide and 10–100 nm for electrochemically exfoliated graphene. The photothermal efficiency measurement showed a temperature increase upon exposure to a 532 nm laser for all samples and the highest photothermal efficiency was measured for the graphene oxide/Ag NP sample prepared at 5 kGy. Electromagnetic interference (EMI) shielding efficiency measurements showed poor shielding for the composites prepared with graphene oxide. On the other hand, all composites prepared with electrochemically exfoliated graphene showed EMI shielding to some extent, and the best performance was measured for the samples prepared at 5 and 20 kGy doses.

Revolutionary composites of silver and zinc oxide nanoparticles from Hardwickia binata: Unleashing their potent antioxidant and anticancer properties

In the present of the study, was utilized the leaf extract of H. binata to synthesize Ag-ZnO nanocomposites. The nanocomposites were characterized using various techniques, including UV, FTIR, XRD and SEM-EDX. Nanocomposites are known for their promising properties, such as mechanical, thermal, electrical and optical characteristics, which have attracted significant attention from both academia and industry, resulting in active research in various fields. The introduction of silver (Ag) into the nanocomposites enabled them to exhibit UV light absorption at 366 nm, while the presence of zinc confirmed the peak at 431 nm. XRD analysis was carried out to determine the crystal structure and composition of the materials. The antibacterial properties of the Ag-ZnO nanocomposites were evaluated using the disc diffusion method, revealing the highest inhibition against the bacteria strain Bacillus subtilis (19 mm) compared to other strains. Furthermore, the nanocomposites demonstrated strong antioxidant activity against DPPH (56 %), ABTS (59 %) and exhibited anti-inflammatory activity (62 %). Additionally, the Ag-ZnO nanocomposites showed promising anti-cancer properties, as evidenced by their effectiveness against a skin cancer cell line (A431-69 %). Moreover, the nanocomposites displayed significant photocatalytic activity, resulting in a 70 % degradation rate. Overall, this study successfully synthesized Ag-ZnO nanocomposites that exhibited robust antibacterial, antioxidant, anti-inflammatory, and anticancer properties. These findings suggest the potential application of these nanocomposites in cancer treatment and environmental studies, particularly in dye degradation.

Enhancing Mechanical and Antimicrobial Properties of Dialdehyde Cellulose-Silver Nanoparticle Composites through Ammoniated Nanocellulose Modification.

Given the widespread prevalence of viruses, there is an escalating demand for antimicrobial composites. Although the composite of dialdehyde cellulose and silver nanoparticles (DAC@Ag1) exhibits excellent antibacterial properties, its weak mechanical characteristics hinder its practical applicability. To address this limitation, cellulose nanofibers (CNFs) were initially ammoniated to yield N-CNF, which was subsequently incorporated into DAC@Ag1 as an enhancer, forming DAC@Ag1/N-CNF. We systematically investigated the optimal amount of N-CNF and characterized the DAC@Ag1/N-CNF using FT-IR, XPS, and XRD analyses to evaluate its additional properties. Notably, the optimal mass ratio of N-CNF to DAC@Ag1 was found to be 5:5, resulting in a substantial enhancement in mechanical properties, with a 139.8% increase in tensile elongation and a 33.1% increase in strength, reaching 10% and 125.24 MPa, respectively, compared to DAC@Ag1 alone. Furthermore, the inhibition zones against Escherichia coli and Staphylococcus aureus were significantly expanded to 7.9 mm and 15.9 mm, respectively, surpassing those of DAC@Ag1 alone by 154.8% and 467.9%, indicating remarkable improvements in antimicrobial efficacy. Mechanism analysis highlighted synergistic effects from chemical covalent bonding and hydrogen bonding in the DAC@Ag1/N-CNF, enhancing the mechanical and antimicrobial properties significantly. The addition of N-CNF markedly augmented the properties of the composite film, thereby facilitating its broader application in the antimicrobial field.

A molecular imprinting electrochemical sensor for detection of anticancer drug amsacrine

PurposeThe purpose of this study is to develop a molecular imprinting electrochemical sensor for the specific detection of the anticancer drug amsacrine. The sensor used a composite of bacterial cellulose (BC) and silver nanoparticles (AgNPs) as a platform for the immobilization of a molecularly imprinted polymer (MIP) film. The main objective was to enhance the electrochemical properties of the sensor and achieve a high level of selectivity and sensitivity toward amsacrine molecules in complex biological samples.Design/methodology/approachThe composite of BC-AgNPs was synthesized and characterized using FTIR, XRD and SEM techniques. The MIP film was molecularly imprinted to selectively bind amsacrine molecules. Electrochemical characterization, including cyclic voltammetry and electrochemical impedance spectroscopy, was performed to evaluate the modified electrode’s conductivity and electron transfer compared to the bare glassy carbon electrode (GCE). Differential pulse voltammetry was used for quantitative detection of amsacrine in the concentration range of 30–110 µM.FindingsThe developed molecular imprinting electrochemical sensor demonstrated significant improvements in conductivity and electron transfer compared to the bare GCE. The sensor exhibited a linear response to amsacrine concentrations between 30 and 110 µM, with a low limit of detection of 1.51 µM. The electrochemical response of the sensor showed remarkable changes before and after amsacrine binding, indicating the successful imprinting of amsacrine in the MIP film. The sensor displayed excellent selectivity for amsacrine in the presence of interfering substances, and it exhibited good stability and reproducibility.Originality/valueThis study presents a novel molecular imprinting electrochemical sensor design using a composite of BC and AgNPs as a platform for MIP film immobilization. The incorporation of BC-AgNPs improved the sensor’s electrochemical properties, leading to enhanced sensitivity and selectivity for amsacrine detection. The successful imprinting of amsacrine in the MIP film contributes to the sensor's specificity. The sensor's ability to detect amsacrine in a concentration range relevant to anticancer therapy and its excellent performance in complex sample matrices add significant value to the field of electrochemical sensing for pharmaceutical analysis.

Comparative Antibacterial Activity of Clay-Supported Silver Nanoparticles Prepared by Conventional Heating and Microwave Methods

AbstractThe synthesis of multifunctional composites still relies on the use of conventional methods. However, these methods are expensive, time consuming and require high volumes of reducing agents which are often toxic. In this study, composites of bentonite-supported silver nanoparticles were prepared comparatively by the conventional heating method and the rapid microwave method; and their antibacterial activity was investigated against Escherichia coli and Staphylococcus aureus. The crystalline nature of the composites was evaluated by X-ray diffraction (XRD), while transmission electron microscope (TEM) coupled with energy-dispersive spectroscope was used for morphology and elemental analysis, respectively. Surface area and pore size analysis of the composites were conducted by the Brunauer, Emmett and Teller analyzer. TEM images revealed successful synthesis of the composites with a better dispersion of the nanoparticles achieved through microwave, where nanoparticle sizes were 6–38 nm and 9–56 nm by the conventional method. It is worth noting that the composites were prepared in less than 30 min using microwave as compared to 2 h of the conventional method. The XRD spectra confirmed the formation of silver and not any other impurities of the metal. These results revealed that, although the two methods are comparable, microwave method is efficient and time saving and can, therefore, synthesize composites with well-dispersed and narrow distributed nanoparticles. The antibacterial results demonstrated that the prepared composites are effective in the inactivation of various bacteria. These composites could be applied in water treatment, wound dressing, packaging, etc.

Inhibitory role of copper and silver nanocomposite on important bacterial and fungal pathogens in rice (Oryza sativa)

Rice (Oryza sativa) being among the most important food crops in the world is also susceptible to various bacterial and fungal diseases that are the major stumbling blocks in the way of increased production and productivity. The bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae and the sheath blight disease caused by Rhizoctonia solani are among the most devastating diseases of the rice crop. In spite of the availability of array of chemical control, there are chances of development of resistance. Thus, there is a need for the nanotechnological intervention for management of disease in the form of copper and silver nano-composites. The copper (CuNPs) and silver nanoparticles (AgNPs) were synthesized using green route and characterized using different high throughput techniques, i.e., UV–Vis, FT-IR, DLS, XRD, FE-SEM, TEM. The particle size and zeta potential of synthesized CuNPs and AgNPs were found 273 nm and − 24.2 mV; 95.19 nm and − 25.5 mV respectively. The nanocomposite of CuNPs and AgNPs were prepared having particle size in the range of 375–306 nm with improved stability (zeta potential − 54.7 to − 39.4 mV). The copper and silver nanoparticle composites evaluated against Xanthomonas oryzae pv. oryzae and Rhizoctonia solani were found to have higher antibacterial (inhibition zone 13 mm) and antifungal activities (77%) compared to only the copper nanoparticle (8 mm; 62% respectively). Net house trials of nano-composite formulations against the bacterial blight of rice also corroborated the potential of nanocomposite formulation. In silico studies were carried out selecting two disease-causing proteins, peptide deformylase (Xanthomonas oryzae) and pectate lyase (Rhizoctonia solani) to perform the molecular docking. Interaction studies indicatedthat both of these proteins generated better complex with CuNPs than AgNPs. The study suggested that the copper and silver nano-composites could be used for developing formulations to control these devastating rice diseases.

Enhanced thermoluminescence, radioluminescence, and optically stimulated luminescence from lithium fluoride and silver nanoparticles composites

Plasmonic properties of metals can increase the sensitivity of ionizing radiation dosimeters. In this work, we study the plasmon resonance of silver nanoparticles (AgNp) to increase the optically stimulated luminescence (OSL) intensity of lithium fluoride (LiF) polycrystals. We produced LiF/Ag nanocomposites with different volumes of a silver nanoparticle dispersion and investigated their OSL response. We also investigated their thermoluminescence (TL) and radioluminescence/scintillation (RL) responses. X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy characterized the synthesized materials. XRD results clearly show the characteristic peaks of LiF and AgNps. TEM images revealed silver nanoparticles with diameters between 80 and 120 nm and LiF crystals with sizes between 1 and 5 μm. Reflectance spectroscopy showed a band around 420 nm, attributed to the plasmon resonance of silver nanoparticles. The responses of the OSL curves to X-ray irradiation were analyzed, showing higher OSL sensitivity with 14 mL AgNp, attributed to the AgNp plasmon resonance. A significant increase in TL and RL intensity could be observed for the LiF/Ag nanocomposites. TL, RL, and OSL results support that addition of AgNps do not lead to the creation of more and new traps or luminescent centers. The increase of TL and RL intensities is therefore related to the coupling of the luminescent centers with the AgNPs plasmons, in an energy-transfer mechanism (plasmon-coupled emission), whereas the enhanced OSL intensity directly correlates with the increased photoionization cross-section of the electronic traps under plasmon resonance conditions (plasmon-coupled excitation). Therefore, these results indicate that AgNp are potential candidates to increase the OSL, TL, and RL intensity from LiF dosimeters.

Fabrication of chitosan/fibrin-armored multifunctional silver nanocomposites to improve antibacterial and wound healing activities

A wound healing substitute promotes rapid tissue regeneration and protects wound sites from microbial contamination. The silver-based antiseptic frequently moist skin stains, burns and irritation, penetrates deep wounds and protects against pathogenic infections. Thus, we formulated a novel fibrin/chitosan encapsulated silver nanoparticle (CH:F:SPG-CH:SNP) composites bandage accelerating the polymicrobial wound healing. Electrospinning method was employed to form the nano-porous, inexpensive, and biocompatible smart bandages. The structural, functional, and mechanical properties were analyzed for the prepared composites. The biological capacity of prepared CH:F:SPG-CH:SNP bandage was assessed against NIH-3 T3 fibroblast and HaCaT cell lines. In vitro hemolytic assays using red blood cells were extensively studied and explored the low hemolytic effect (4.5 %). In addition, the improved drug delivery nature captured for the CH:F:SPG-CH:SNP composite bandage. Antibacterial experiments were achieved against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Lactobacillus bulgaricus using zone inhibition method. Moreover, in-vivo wound healing efficacy of fabricated smart bandage was evaluated on the albino Wistar rats which revealed the significant improvement on the postoperative abdomen wounds.

The Influence of Aging on the Structure and Properties of Composite Materials Based on Polyurethane and Silver Nanoparticles

The aging processes and their influence on structure, thermophysical and antimicrobial properties of polymer nanocomposites based on segmented polyurethane and silver nanoparticles were studied. It was established that an increase in the intensity of intermolecular interactions of polyurethane occurred regardless of the concentration of silver in the silver nanoparticles due to a change in the packing of macromolecules. It was shown that in the process of aging of composites, the effective size of crystallites of polymer matrix decreases and varies in the range of 1.35–1.50 nm. The most pronounced effect of aging is manifested on the melting temperatures of the crystalline phase of polyurethane and the degree of crystallinity. It was found that polyurethane–silver nanoparticle composites exhibit a very high inhibitory capacity against Staphylococcus aureus, Escherichia coli, and Candida albicans. It is shown that aging processes do not affect the antimicrobial characteristics of the studied materials, which indicates their stability. Due to their unique characteristics, synthesized nanocomposite films can be promising for use as antimicrobial coatings in various applications.

Poly (Vinyl Alcohol) Hydrogels Boosted with Cross-Linked Chitosan and Silver Nanoparticles for Efficient Adsorption of Congo Red and Crystal Violet Dyes.

In our previous work, three different weight ratios of chitosan/PVA (1:3, 1:1, and 3:1) were blended and then cross-linked with trimellitic anhydride isothiocyanate (TAI) at a concentration depending on their chitosan content, obtaining three hydrogels symbolized by H13, H11, and H31. Pure chitosan was cross-linked with TAI, producing a hydrogel symbolized by H10. Further, three H31-based silver nanoparticles composites (H31/AgNPs1%, H31/AgNPs3%, and H31/AgNPs5%) were also synthesized. They were investigated, for the first time in this study, as adsorbents for Congo Red (CR) and Crystal Violet (CV) dyes. The removal efficiency of CR dye increased with increasing H10 content in the hydrogels, and with increasing AgNP content in the composites, reaching 99.91% for H31/AgNPs5%. For CV dye, the removal efficiency increased with the increase in the PVA content. Furthermore, the removal efficiency of CV dye increased with an increasing AgNP content, reaching 94.7% for H31/AgNPs5%. The adsorption capacity increased with the increase in both the initial dye concentration and temperature, while with an increasing pH it increased in the case of CV dye and decreased in the case of CR dye. The adsorption of CV dye demonstrated that the Freundlich isotherm model is better suited for the experimental results. Moreover, the results were best fitted with pseudo-second-order kinetic model.

Improving beta phase of spin coated PVDF thin films by doping with silver nanoparticles

This research deals with the effect of process parameters of spin coating such as spinning speed, weight composition of silver nanoparticles (AgNP), and annealing duration on the phase change of polyvinylidene fluoride (PVDF) thin films. FTIR spectroscopy along with XRD confirmed the transformation of α to β-phase in the PVDF thin films. The spin coated films exhibited higher β-fraction than that of the pristine PVDF. The β-fraction in the thin films was mainly influenced by the addition of AgNP. The DSC results showed decrease in crystallinity from 63.74 to 53.21% with increase in spinning speed from 1000 to 3000 rpm due to the over-stretching of crystalline lamellae.

Antimicrobial Effect of Silver Nanoparticles and Combination with Cotrimoxazole against Salmonella Typhi in Vitro and in Animal Model

Introduction: Salmonella typhi is a large group of gram-negative bacilli with Enterobacteriaceae and common pathogens between humans and animals, which is the main cause of typhoid fever in humans. One of the most common antibiotics in the treatment of Salmonella is cotrimoxazole, but due to the widespread use of antibiotics, bacterial resistance has developed. The aim of this study was to investigate the antibacterial effect of silver nanoparticles and its combination with the antibiotic cotrimoxazole to produce a more effective antimicrobial drug against Salmonell typhi.
 Methods: In this experimental study, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for silver nanoparticles and combination with cotrimoxazole, was performed based on microdilution method. Then, their antibacterial effects were investigated in infected mouse model. In order to analyze the results statistically, SPSS software version 16 was used. In this test, P< 0.05 was considered as a significant level.
 Results: MIC and MFC of silver nanoparticles for Salmonella typhi were 4 ppm and 8 ppm respectively, composition of silver nanoparticles with cotrimoxazole for Salmonella typhi were 62 ppm and 125 ppm and cotrimoxazole for Salmonella typhi were 500 ppm and 1000 ppm. Mouse model to study the antibacterial effect of silver nanoparticles and combination with cotrimoxazole against Salmonella typhi infection was confirmed., Silver nanoparticles had the highest antibacterial effect and cotrimoxazole has the lowest antibacterial effect than other groups.
 Conclusion: Silver nanoparticles are very effective compared to other groups, especially the antibacterial cotrimoxazole.

Silver Nanoparticles Loaded on Chitosan-g-PVA Hydrogel for the Wound-Healing Applications.

Silver nanoparticle composites have abundant biomedical applications due to their unique antibacterial properties. In the current work, green tea leaf extract was used as a natural reducing agent to synthesize AgNPs (AgNPs) using microwave irradiation technology. Furthermore, microwave irradiation has been used for the preparation of AgNPs/chitosan (Ch) grafted polyvinyl alcohol (PVA) hydrogel samples. To approve the accomplishment of AgNPs hydrogel polymer, UV-spectrum, TEM, and FT-IR spectrum analyses and the release of silver ions, actions were taken. The wound-healing ability of the prepared hydrogel samples was measured via both the in vitro (fibroblast cells) and the in vivo using rat models. It was found that chitosan-grafted polyvinyl alcohol, including AgNPs, exhibited excellent antibacterial activity against E. coli and S. aureus using the agar diffusion method. It can be said that microwave irradiation was successful in creating a hydrogel that contained silver nanoparticles. A wound that was still open was successfully treated with these composites.

Silver nitrate concentration on silver nanoparticles formation attached on cellulose nanocrystal matrix

Cellulose nanocrystals (CNCs) with silver nanoparticle composites are used in various applications, ranging from packaging to biomedical. Therefore, the optimum performance of this hybrid nanomaterial can be achieved by controlling agglomeration in the silver nanoparticle synthesis. The agglomeration behaviour can be monitored by integrating CNCs as polymer matrix during the synthesis. This work aimed to investigate the effect of silver nanoparticles (AgNPs) synthesised from different silver precursor concentrations and loaded on the surface of CNCs. The cellulose nanocrystal was isolated from an oil palm empty fruit bunch (EFB). The AgNPs were synthesised by using the reduction technique of silver nitrate at 0.1 M and 0.5 M concentrations and with the aid of glucose solution. The AgNPs_CNC nanosuspension was analysed by using UV–Vis spectroscopy, FTIR, DSC, and FESEM/EDX. The spectroscopy data from UV–Vis indicated a strong absorption peak at 385 nm due to the formation of the nanoparticles in AgNPs_CNC_0.5 nanosuspension. Meanwhile, the morphological result showed that the AgNPs formed were spherical in shape (57.8 nm) with strong existence of silver, carbon, and oxygen. Therefore, the AgNPs_CNC nanosuspension was successfully synthesised by using 0.5 M silver nitrate with uniform and well-distributed nanoparticles.

Fungi-Templated Silver Nanoparticle Composite: Synthesis, Characterization, and Its Applications

The self-assembly of nanoparticles on living bio-templates is a promising synthetic methodology adopted for synthesizing nano/microstructures with high efficiency. Therefore, the method of bio-templating offers various advantages in controlling the geometries of nano/microstructures, thereby increasing the efficiency of the synthesized material towards various functional applications. Herein, we utilized a filamentous fungus (Sclerotium rolfsii) as a soft bio-template to generate silver nanoparticle (AgNP) microtubules adhering to the fungal hyphae. The resulting composite combines the unique properties of silver nanoparticles with the biological activity of the fungi. The 3D fungal hyphae–silver nanoparticle (FH-AgNP) composite was characterized using SEM, elemental analysis, and the X-ray diffraction technique. Additionally, to highlight the functional application of the synthesized composite, dye degradation studies of methylene blue under visible light was effectuated, and a percentage degradation of 67.86% was obtained within 60 min, which highlights the potent catalytic activity of FH-AgNPs in dye degradation. Further, the antibacterial study of the composite was carried out against the bacterium Escherichia coli, and it was found that 200 μg of the composite exhibited maximum antibacterial properties against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria. Overall, fungi-templated silver nanoparticle composites are a promising area of research due to their combination of biological activity and unique physical and chemical properties.

Primula vulgaris'ten Sentezlenen Gümüş Nanopartiküllerin Antimikrobiyal ve Antioksidan Potansiyeli

In this study, biosynthesis and in vitro phytochemical composition, antibacterial and antioxidant activities of silver nanoparticles were investigated by using aqueous leaf, flower and root extracts of Primula vulgaris (P. vulgaris subsp. vulgaris). The synthesized silver nanoparticles (AgNPs) were confirmed by color conversion and ultraviolet-visible (UV-visible) spectrophotometry. The appearance of a dark brown color and a UV absorption spectrum range at 440 nm confirmed the synthesized silver nanoparticles. The antimicrobial activity of silver nanoparticles synthesized from the leaf of P. vulgaris; S. aureus 25±1, S. epidermidis 20±1, P. aeruginosa 20±1, A. hydrophila 21±1, C. albicans 25±1, C. tropicalis 25±1, C. parapsilosis 22±1 and C. glabrata 20±1 mm zone diameter was determined. The most antimicrobial effect of P. vulgaris leaf aqueous extract; S. aureus 20±1, S. epidermidis 18±1, A.hydrophila 15±1, P. aeruginosa 12±2, C. albicans 18±1, C. glabrata 18±1, C.tropicalis15±2, and C. parapsilosis 15±2 mm zone diameter was revealed. The presence of flavonoids, terpenoids, protein, and carbohydrates was found to be higher in silver nanoparticles synthesized in the flower part of P. vulgaris, according to phytochemical screening. While saponins were detected in P. vulgaris root extracts, tannins and protein were detected in the leaf extract. The flower had the highest total phenolic extract content of the silver nanoparticle (29.08±0 mg GAE/g DW), while the leaf and root had the lowest total phenolic content of 9.06±0.5 and 8.64±3.3 mg GAE/g DW, respectively. The flower had the highest total phenolic extract content of the plant aqueous extracts (25.10±0.2 mg GAE/g DW), while the leaf and root had the lowest (8.28±0.5 and 5.20±0.0 mg GAE/g DW, respectively).The DPPH (1,1-Diphenyl-2-picrylhydrazil) assay was used to assess free radical scavenging activity. The antioxidant activity of AgNPs biosynthesized using P. vulgaris flower extract was 90.6 %, while P. vulgaris flower aqueous extracts were 86.3 %. This can be concluded that silver nanoparticles synthesized using P. vulgaris flower extract are useful in the preparation of pharmacologically useful drugs.

Kaolin-Supported Silver Nanoparticles as an Effective Catalyst for the Removal of Methylene Blue Dye from Aqueous Solutions.

Water contamination by organic dyes has become a reason for severe environmental pollution and has been threatening the aquatic ecosystem. In this study, kaolin-supported silver nanoparticle (Ag-NP) composites were synthesized by a facile two-step adsorption-reduction method through the reduction of silver ions adsorbed onto locally available, inexpensive, and easily pretreated kaolin surfaces by using sodium borohydride (NaBH4) for the catalytic degradation of methylene blue (MB) dye in aqueous solution. The morphology, structure, surface area, and interaction of the synthesized materials were investigated by scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy, respectively. Characterization results showed the successful growth of Ag-NPs on the kaolin surface. To understand the catalytic degradation performance of the catalyst, batch experiments were carried out using MB dye as a model dye. The catalytic reduction tests confirmed the importance of Ag-NPs and the high catalytic activities of the synthesized Ag-NPs/kaolin composite toward MB dye reduction. The degradation results indicated that the increased Ag-NP content on the kaolin surface through repeating cycles could effectively enhance the removal of MB dye from an aqueous solution. The kinetic analysis of the MB dye degradation of the catalyst has fitted the pseudo-first-order kinetic model. More than 97% removal efficiency was still present after five reuse cycles, demonstrating exceptional stability and reusability of the composite. In conclusion, the Ag-NPs supported kaolin (Ag-NPs/kaolin) composite was found to be a promising catalyst for the excellent catalytic activity to reduce a model dye MB from the aqueous solution in the presence of NaBH4 with catalytic efficiency higher than 97% and a reduction rate constant, k red, higher than 0.86 min-1.

Antibacterial and electrochemical evaluation of electrospun polyethersulfone/silver composites as highly persistent nanomaterials

AbstractSilver‐based antibacterial nanoparticles have demonstrated indices of possible bacterial resistance after consecutive periods of time, limiting their application on antibacterial surfaces. In this work, we fabricate electrospun composites of polyethersulfone (PES) and silver nanoparticles (AgNPs), displaying highly‐persistent antibacterial behavior after 10 bacterial expositions. The herein‐reported membranes were synthesized by changing the Ag loading (0.05, 0.5, and 5 wt%), adding polyvinylpyrrolidone as a dispersion promoter, and the resulting composites were evaluated after a different number of bacterial expositions against Escherichia coli (E. coli) aiming to determine their bacterial tolerance. SEM micrographs revealed that the PES fiber diameters decreased as a function of the silver content from 798 to 398 nm, attributed to the conductivity and the viscosity improvement by AgNPs introduction in the polymer solution during the electrospun process. Moreover, the surface roughness (determined by atomic force microscopy) and the contact angle changed with the Ag content, increasing the hydrophilic behavior and promoting a better interaction with the bacteria suspended in the solution. Antibacterial activity kinetics of PES/AgNPs fibers showed 75% bacterial inhibition against E. coli in the composite with 0.5 wt% Ag after 3 h of exposition, and 75% after 1.5 h in composites with 5 wt% of Ag. The ca. 25% survival bacteria were used for consecutive bacterial tolerance assays, where the antibacterial behavior was constant after 10 expositions. Interestingly, electrochemical tests confirmed that PES fibers could control the silver‐releasing process. Thus, PES/AgNPs composites avoid the bacterial adaptation process, which makes them suitable as functional antimicrobial nanomaterials.

Improved Electrical Conductivity and Strength of α-Al-Carbon Nanotubes Blended with Silver Nanoparticles Composites

An attempt has been made to develop a new enhanced electrical conductor nanocomposites using green synthesis silver nanoparticles (GAgNPs) modified carbon nanotubes (CNTs) reinforced aluminum nanocomposites. High-intensity ball milling and spark plasma sintering (SPS) were used to produce the composites. The nanocomposite' microstructure, strength, model, and electrical conductivity were all determined. 2%GAg.NPs in Al-4-percent CNTs helps to refine the grain structure of the Al-4-percent CNTs. More dislocation density was generated by the creation of sub-grain in the Al-4 percent CNTs+2 percent GAgNPs composite. Tensile strength and electrical conductivity were increased by 82.14 and 106.88% using Al-4-percent CNTs +2%GAg.NPs nanocomposite. The ductility mode of fracture associated with the tiny sub-grain produced at the surface was greatly improved when 2% GAgNPs were added to Al-4% CNTs. It was established that the GAgNPS can been used to coat CNTs enhance the strength and electrical conductivity of Al-4 percent CNTs nanocomposites.

Spontaneous Transformation of Biomedical Polymeric Silver Salt into a Nanocomposite: Physical-Chemical and Antimicrobial Properties Dramatically Depend on the Initial Preparation State.

An antimicrobial polyacrylic silver salt (freshly prepared, stored for one year and model-aged) was studied by physical–chemical techniques for nanoparticle detection. In all cases, this salt represents a composite of radical-enriched macromolecules and silver(0) nanoparticles. As time passed, the initial small spherical nanoparticles were converted into larger non-spherical silver nanoparticles. The initial highly water-soluble antimicrobial solid nanocomposite almost loses its solubility in water and cannot be used as an antimicrobial agent. Unlike insoluble solid silver polyacrylate, its freshly prepared aqueous solution retains a liquid-phase consistency after one year as well as pronounced antimicrobial properties. The mechanism of these spontaneous and model-simulated processes was proposed. These results have attracted attention for officinal biomedicinal silver salts as complex radical-enriched nanocomposite substances; they also indicate contrasting effects of silver polymeric salt storing in solid and solution forms that dramatically influence antimicrobial activity.