Attachment Of Ag Nanoparticles Research Articles

Antibacterial Activity of the Green Synthesized Plasmonic Silver Nanoparticles with Crystalline Structure against Gram-Positive and Gram-Negative Bacteria.

Nanoparticles (NPs) have attracted considerable interest in numerous fields, including agriculture, medicine, the environment, and engineering. The use of green synthesis techniques that employ natural reducing agents to reduce metal ions and form NPs is of particular interest. This study investigates the use of green tea (GT) extract as a reducing agent for the synthesis of silver NPs (Ag NPs) with crystalline structure. Several analytical techniques, including UV-visible spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD), were used to characterize the synthesized Ag NPs. The results of UV-vis revealed that the biosynthesized Ag NPs exhibited an absorbance plasmonic resonance peak at 470 nm. According to FTIR analyses, the attachment of Ag NPs to polyphenolic compounds resulted in a decrease in intensity and band shifting. In addition, the XRD analysis confirmed the presence of sharp crystalline peaks associated with face-centered cubic Ag NPs. Moreover, HR-TEM revealed that the synthesized particles were spherical and 50 nm in size on average. The Ag NPs demonstrated promising antimicrobial activity against Gram-positive (GP) bacteria, Brevibacterium luteolum and Staphylococcus aureus, and Gram-negative (GN) bacteria, Pseudomonas aeruginosa and Escherichia coli, with a minimal inhibitory concentration (MIC) of 6.4 mg/mL for GN and 12.8 mg/mL for GP. Overall, these findings suggest that Ag NPs can be utilized as effective antimicrobial agents.

Antimicrobial and barrier properties of polyacrylic acid/GO hybrid nanocomposites for packaging application

Herein, a green and low-cost approach is established for the designing of polyacrylic acid//Graphene Oxide/Silver (PAA/GO/Ag) nanocomposites, by utilizing sodium alginate as a reducing agent in an aqueous medium via in situ polymerization technique. The outstanding thermal stability, remarkable tensile properties, and distinctive chemical resistance of PAA/GO/Ag nanocomposites are credited to the fabrication of Ag nanoparticles (NPs). The thermal stability of such composites showed its resistance up to 600 °C with a residue of 21%. The oxygenated functional groups absorption intensity for PAA/GO/Ag (at 3635 cm−1) is found to be less than the other precursors proving the attachment of Ag NPs on the GO based polymer matrix. The HRTEM images provide a transparent layer-like structure confirming the presence of GO and dark distorted spherical shapes for Ag NPs with an average diameter of 50–70 nm of the designed composite. The zone of inhibition against Escherichia coli (E. Coli) bacteria determines the antibacterial activities of PAA/GO/Ag nanocomposites with various wt% of Ag NPs. The oxygen barrier behaviour of PAA/GO/Ag nanocomposites is raised by eleven folds with the incorporation of 27 × 10−3 wt% of Ag NPs as compared to PAA/GO matrix. Therefore, the reinforcement of Ag NPs enhances the thermal stability, chemical resistance, oxygen barrier, and antimicrobial properties of the PAA/GO matrix, on account of which our synthesized material stands as a beneficial candidate for packaging applications.

Enhanced visible-light photocatalytic activity of Ag/In2S3 photocatalysts induced by Schottky contact and SPR of Ag

In this work, a highly photocatalytic Ag/In2S3 was synthesized via the hydrothermal and photoreduction method. The as-prepared photocatalysts were confirmed by XRD, SEM, HRTEM, and XPS showing that Ag nanoparticles were decorated on the In2S3 surface. Photocatalytic activities of photocatalysts were investigated for photodegradation of methyl orange (MO) under visible light. The Ag/In2S3 composites showed the enhanced photocatalytic efficiency of 97% under visible light irradiation for 90 min, which was about 3.0 times higher than that of pure In2S3. The enhanced photocatalytic performance could be owing to the SPR of Ag and the Schottky junction formed between Ag and In2S3. Our PL results indicate the inhibited recombination of the photogenerated electron–hole pairs in In2S3 upon the attachment of Ag nanoparticles. The active species tests demonstrate that the superoxide radical (·O2−) and h+ are responsible for the efficient degradation of MO over Ag/In2S3. In addition, it also proposes a potential mechanism for enhancing the photocatalytic activity.

Double-shell PANS@PANI@Ag hollow microspheres and graphene dispersed in epoxy with enhanced microwave absorption

Double-shell hollow conductive poly(acrylonitrile) microspheres@polyaniline@Ag (PANS@PANI@Ag) was synthesized by a facile two-step method. Polyaniline-coated poly(acrylonitrile) microspheres (PANS@PANI) prepared by in situ polymerization exhibited a porous, corrugated and compact conductive network, making for the formation and attachment of Ag nanoparticles. Incorporating these hollow conductive spheres and reduced graphene oxide (RGO) into epoxy resin, a lightweight microwave absorber was brought out. The chemical composition, micro-structure surface morphology and electromagnetic properties were thoroughly characterized and analyzed. The calculated results showed that the optimal reflection loss (RL) was − 44.9 dB at 9.16 GHz with a constitution of 1 wt% dielectric RGO and 1 wt% conductive PANS@PANI@Ag, and the corresponding effective bandwidth was about 2 GHz. However, the microwave absorption capacity gradually reduced with the raise of PANS@PANI@Ag content, derived from the high conductivity leading to more microwave reflection. As the PANS@PANI@Ag content increased to 5 wt%, the minimum RL was − 14.7 dB and still remained an effective absorption performance with a lower density of 0.47–0.53 g/cm3. Therefore, the as-obtained composites paved a new route for lightweight and strong absorption microwave absorbers in commercial and military application.

Structural analysis of graphene oxide/silver nanocomposites: optical properties, electrochemical sensing and photocatalytic activity

In the present study, graphene oxide/silver (GO/Ag) nanocomposites were synthesized via a facile simple one pot chemical reduction method using ethylene glycol/sodium borohydrate (EG/NaBH4) as solvent and reducing agent. GO was selected as a substrate and stabilizer to prepare GO/Ag nanocomposites. The synthesized GO/Ag nanocomposites were characterized by a series of techniques. Highly monodispersed stable crystalline silver nanoparticles having a face-centered cubic (fcc) phase were confirmed by X-ray powder diffraction (XRD) on GO signature. Scanning electron microscopy images showed that Ag nanoparticles are deposited on the GO sheet with a narrow size distribution. Transmission electron microscopy observations revealed that large numbers of Ag nanoparticles were uniformly distributed on GO sheet and well separated with an average size of 18 nm. Ultraviolet–visible (UV–Vis) spectroscopic results showed the peak of GO and surface plasmon resonance (SPR) of Ag nanoparticles. The SPR property of GO/Ag nanocomposites showed that there was an interaction between Ag nanoparticles and GO sheet. The intensities of the Raman signal of GO/Ag nanocomposites are gradually increased with attachment of Ag nanoparticles i.e. there is surface-enhanced Raman scattering activity. Electrochemical investigations indicated that the nanocomposites possessed an excellent performance for detecting towards 4-nitrophenol. An application of the obtained GO/Ag nanocomposites as a catalyst in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 was demonstrated. The GO/Ag nanocomposites exhibited high activity and stability for the catalytic reduction of 4-nitrophenol. The prepared GO/Ag nanocomposites act as photo-catalysts.

Enhanced conductivity of transparent and flexible silver nanowire electrodes fabricated by a solution-processed method at room temperature

A simple method was developed to increase the electrical conductivity of Ag nanowire (NW) transparent electrodes prepared at room temperature. By dipping Ag NW coated poly(ethylene terephthalate) (PET) film into AgBr solution with sodium ascorbate as reductant, Ag nanoparticles grow on the surface of Ag NWs and their junction positions. It was found that the attachment of Ag nanoparticles on Ag NWs decreases the electrode film resistance from 220–300Ω/sq. to 30–50Ω/sq., which is mainly due to the change in junction resistance with Ag nanoparticles functioning as a bridge for electron transportation between Ag NWs. Ag NW coated PET films have a transmittance of 85.0% at the spectral wavelength of 550nm, and this value does not change much after AgBr treatment. A mechanical study shows that Ag NW electrodes on flexible substrates have excellent robustness subjected to bending. The properties of transparent Ag NW electrodes prepared using our method meet the requirements of transparent electrodes for many applications and could be a replacement for indium tin oxide for flexible electronics and solar cells.

Non-aqueous colloidal processing route for fabrication of highly dispersed aramid nanofibers attached with Ag nanoparticles and their stability in epoxy matrixes

Abstract In order to achieve the one-dimensional alignment of Ag nanoparticles (NPs) in epoxy resins, a simple technique to attach Ag NPs on aramid nanofibers (ANFs) and then to disperse the prepared Ag NP/ANF composites in epoxy resins and their processing solvents has been established. To facilitate the attachment of Ag NPs on ANFs and the stabilization of the Ag NP/ANF composites, the surface of the Ag NPs was modified with polyethyleneimine (PEI) and an anionic surfactant that branches into alkyl- and polyethylene glycol-based chains, which improved the stability of the NPs in various solvents and polymers. The prepared Ag NPs were then dispersed into ethanol or toluene and mixed with an ANF suspension prepared in dimethyl sulfoxide (DMSO) with the assistance of ultrasonication. The effect that the solvents and the Ag NPs/ANFs ratio, during the mixing procedure, had on the morphology and stability of the prepared Ag NP/ANF composites was investigated. It was found that Ag NPs could attach on ANFs without forming strong aggregates, when ethanol was chosen as the solvent. An increase in the average diameter of the Ag NPs attached on the ANFs was observed as the relative number of Ag NPs increased; this could be due to the dissolution and reduction of Ag + during the ultrasonication treatment, assisted by the PEI layer on the Ag NPs. The prepared Ag NP/ANFs were found to be dispersible in epoxy/toluene mixtures and epoxy resins, and their long-term stability (>3 days) was ensured when the suspension viscosity was controlled at >1.7 Pa s.

Silver-Nanoparticle-Attached Indium Tin Oxide Surfaces Fabricated by a Seed-Mediated Growth Approach

By applying a seed-mediated growth method that had been reported for the chemical synthesis of Ag nanorods and nanowires in aqueous solution, we successfully attached Ag nanosphere and nanorod particles to indium tin oxide (ITO) surfaces. In this method, it is characteristic that the attachment can be performed without using bridging reagents, such as 3-mercaptopropyltrimethoxysilane, but rather through a two-step immersion into the seed solution first and then into the growth solution containing AgNO(3), cetyltrimethylammonium bromide, and ascorbic acid. It was found that the formed nanostructures were very sensitive to the amount of ascorbic acid in the growth solution. Whereas Ag nanoparticles grew on the ITO surface with a moderate dispersion when the concentration of ascorbic acid in the growth solution was 0.64 mM, the formation of nanorods and nanowires was observed when the ascorbic acid concentration was increased to 0.86 mM. The attachment of Ag nanoparticles onto the ITO surfaces was strong enough for further use, e.g., as a working electrode. From electrochemical measurements, it was confirmed that the outer spheres of the Ag nanoparticles involved in the redox reaction show the typical oxidation and reduction waves of Ag. In addition, the redox behavior of [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) was improved on the Ag-nanoparticle-attached ITO (AgNP/ITO) electrode, reflecting the low electron-transfer resistivity, which is a remarkable advantage of the present fabrication without using bridging reagents. This result indicated that the Ag nanoparticles promote the electron-transfer reactions by being present on the conducting ITO surface. The AgNP/ITO electrode was examined for the reduction of the methyl viologen dication in order to discuss some features of the present fabrication.