Synthesis of silver nanoparticles from electronic scrap by chemical reduction

In the present research, the use of electronic waste in the synthesis of silver nanoparticles was investigated. For this purpose, electronic scraps were used as a consumable part to synthesize silver nanoparticles. The results revealed that by optimizing the time and temperature of the dissolution process using nitric acid solution up to 90%, silver can be extracted from these parts. The temperature of 60°C and the duration of one hour were determined as the optimum conditions for this phase. Afterward, the synthesis of silver nanoparticles was checked using silver nitrate solution. The results indicated that the concentration of initial silver nitrate had a significant impact on the quality of the final product so that the best conditions for the synthesis of silver nanoparticles with suitable properties were provided at 1 molar concentration. Phase studies indicated that the main phase of the synthesized silver particles had an FCC structure and no unwanted phase was observed. Ultraviolet-visible analysis of the synthesized powder revealed that the main peak for the silver nanoparticles appeared in the wavelength range of 400 to 450 nm. DLS analysis revealed that precursor's particles inside the sol were below 15 nm. Based on AFM and TEM investigations, the particles synthesized under these conditions had nanometric spherical morphology with uniform particle size distribution.

Microleakage in class II restorations of two bulk fill resin composites and a conventional nanohybrid resin composite: an in vitro study at 10,000 thermocycles

Background The contraction presented by resin composites causes an increase in stress at the tooth-resin interface, causing micro-gaps that allow microleakage. This study aims to evaluate the degree of in vitro marginal microleakage in class II restorations with two bulk fill resin composites compared to a conventional nanohybrid resin composite. Methods The present study was an in vitro experimental design. A total of 30 standardized class II cavities were prepared in 15 human molars (mesially and distally). These cavities were later distributed in 3 groups according to the type of resin. Groups A and B were restored with bulk fill resin composites (Filtek—3 M/ESPE and Tetric N-Ceram—Ivoclar/Vivadent respectively) in a single increment of 4 mm. Group C was restored with the Filtek Z350 XT – 3 M/ESPE resin composite and two increments of 2 mm. Later, the restorations were subjected to 10,000 thermocycles between 5 °C to 55 °C and immersed in a silver nitrate solution (1 M for 24 h). The crowns were then sectioned mesiodistally and observed under the stereomicroscope to determine the degree of marginal microleakage at the occlusal and cervical areas. The results were analyzed with the Kruskal–Wallis and the Mann–Whitney U statistical tests. Results There were no statistically significant differences regarding the degree of microleakage between the three types of resin composites in the occlusal and cervical areas (p > 0.05). Similarly, there were no significant differences after comparing each resin type in its occlusal and cervical area (p > 0.05). Conclusion Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites showed no statistically significant differences with the conventional nanohybrid resin composite Filtek Z350XT at both occlusal and cervical areas.

UV-Light Mediated Biosynthesis of Silver Nanowires; Characterization, Dye Degradation Potential and Kinetic Studies

Herrin, a simple and eco-friendly method for the synthesis of silver nanowires (Ag-NWs) has been reported. Silver nanowires were synthesized using Psidium guajava seed extract that acted as a reducing agent as well as a stabilizing agent for silver nitrate solution. Synthesis was carried out at 50 °C temperature under continuous UV-irradiation. Silver nanowires were initially characterized by a UV-visible and FTIR spectrophotometer. In addition, morphology and particle size of synthesized Ag-NWs were determined using Field Emission Scanning Electron Microscopy and X-ray diffraction (XRD) techniques. Nanowires were found to have 12.8 μm length and 200–500 nm diameter and cubic phase morphology. Furthermore, the catalytic potential of Ag-NWs for the degradation of methyl orange dye (MO) was determined. The selected dye was degraded successfully that confirmed the catalytic potential of Ag-NWs. The authors concluded that Ag-NWs can be synthesized using plant extract having excellent morphological features as well as impressive catalytic potential.

Diatom Mediated Production of Fluorescent Flower Shaped Silver-Silica Nanohybrid

Fabrication of flower-like nanostructures are gaining attention because of their high surface/volume ratio and extensive adsorption capacity. In the present investigation, flower-shaped, autofluorescent silver-silica (Ag-SiO2) hybrid nanoparticles have been fabricated exploiting diatoms as a source of nanosilica. Two different species of Gedaniella including G. flavovirens and G. mutabilis showed their efficacy in synthesizing fluorescent Ag-SiO2 nanoflowers (NFs) and nanospheres (NSs) against 9 mM silver nitrate solution, respectively. The biogenic nanoconjugate (Ag-SiO2) was characterized by Uv-vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), scanning (SEM) and transmission (TEM) electron microscopy. Production of Ag-SiO2 hybrid nanoparticle was confirmed by observing both Ag and Si signals from a single nanoparticle in an EDS study. The broad and single absorption band at ~420 nm in Uv-vis spectroscopy confirmed proper miscibility and production of hybrid nanoparticles. The Ag-SiO2 nanohybrids revealed autofluorescent property under the blue light region (excitation ~450–490 nm). SEM images of particles synthesized by G. flavovirens revealed the production of microscopic flower shaped Ag-SiO2 particles with several layers of petals. A TEM study confirmed that the synthesized Ag-SiO2 NFs are variable in size with 100–500 nm in diameter. Decolorization of methylene blue after exposure to Ag-SiO2 particles confirmed catalytic activity of synthesized nanostructures. This eco-friendly method provides a new dimension in nanobiotechnology for biogenesis of such hierarchical nanostructure in a cost-effective way.

Copper Electroless Metallization of Cellulose Paper via Polydopamine Coating and Silver Catalyst

The paper presents the results of copper electroless metallization of cellulose paper with the use of a polydopamine coating and silver catalyst. The polydopamine coating was deposited via a simple dip method using a dopamine hydrochloride solution in 10 mM TRIS-HCl buffer with a pH of 8.5. The research showed that as a result of this process, cellulose fibers were covered with a homogeneous layer of polydopamine. The unique properties of the polydopamine coating allowed the reduction of silver ions from silver nitrate solution and the deposition of silver atoms on the paper surface. Deposited silver served as a catalyst in the autocatalytic electroless copper-plating process. The copper layer covered the entire surface of the paper sheet after 5 min of metallization, favorably affecting the electrical properties of this material by lowering the surface resistivity. The deposited copper layer was further characterized by good adhesive strength and high susceptibility to deformation.

Formulation of Clitoria ternatea Leaves-mediated Silver Nanoparticles to Control Aedes aegypti Larvae

Introduction: Global rise in the Aedes-borne diseases and harmful effects of synthetic insecticides has diverted research to explore secondary metabolites in plants as mosquito control agent in the form of nanoparticles. Current study investigated Clitoria ternatea-mediated nanoparticles against Aedes aegypti. Methods: The aqueous and hexane leaf extracts of C. ternatea were assayed against Ae. aegypti early fourth instars. The extract-mediated silver nanocomposites (AgNCs) were synthesized after optimizing the volume and concentration of silver nitrate solution. The synthesis was tracked by the colour change of reaction mixture from pale yellow to dark brown followed by monitoring with UV-Visible spectroscopy and Dynamic Light Scattering. Results: The biosynthesis of 3 mM, 4 mM and 5 mM AgNCs was traced at 438, 401 and 407 nm, respectively. The average particle size distribution ranged from 34.62 to 60.64 nm and polydispersity index was 0.6-0.7. The 24 h larval exposure with aqueous and hexane leaf extracts demonstrated respective LC50 values of 53.057 and 42.179 mg/L, which decreased significantly on larvicidal assay with NCs. The 5mM AgNCs showed the maximum efficiency with LC50 of 10.317 mg/L after 24 h. Scanning and transmission electron microscopy images demonstrated a spherical, poly-dispersed structure with diameter in the 1-27 nm range. The assays against non-targets; Moina and Cyclops ascertained the eco-safety of NCs. Conclusion: The study demonstrated the C. ternatea leaf extract as possible effective mosquito nano-larvicide, alternate to traditional insecticides. Field studies, which could not be held due to the current pandemic, would further ascertain the possible use of these NCs against Aedes larvae.

Antimicrobial and Antibiofilm Effects of Silver Nanoparticles Produced by Yarrowia lipolytica Against Vegetative and Starved Shigella

Silver nanoparticles have attracted much interest from scientists to develop nanosilver-based disinfectant products due to their unique properties of high antimicrobial activity. This study focused on biosynthesis, characterization, antimicrobial and antibiofilm effects of silver nanoparticles against vegetative and starved Shigella strains. The silver nanoparticles were synthesized using the yeast Yarrowia lipolytica and characterized by ultraviolet–visible spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial and antibiofilm activities of silver nanoparticles were tested against the growth of vegetative and starved Shigella strains. After the addition of silver nitrate solution to the supernatant of Y. lipolytica, we noticed the appearance of a brown-black coloration that suggested the formation of silver nanoparticles. The presence of silver nanoparticles was manifested by a maximum absorption in the ultraviolet–visible range, precisely at the wavelength 420[Formula: see text]nm. The crystalline nature and the stability of silver nanoparticles were confirmed, respectively, by XRD and FTIR analysis. The antibacterial activity of silver nanoparticles showed significant toxicity on Shigella strains indicating that the starved cells were more sensitive to treatment with silver nanoparticles than vegetative cells. Surprisingly, the biofilm formation had not been inhibited by silver nanoparticles for both vegetative and starved cells. In conclusion, a new class of nanosilver containing disinfectant nanoproducts will be promising for advanced environmental treatments including air disinfection, water disinfection, surface disinfection and personal hygiene that will help to prevent the further outbreak of diseases.

UV-light Mediated Green Synthesis of Silver Nanowires and Their Catalytic Degradation Potential Against Methyl Orange

In the present study, a simple and eco-friendly method for the synthesis of silver nanowires (Ag-NWs) has been reported. Psidium guajava seed extract was used as a reducing agent for silver nitrate solution at 70 °C temperature under continues UV-irradiation, for the production of Ag-NWs. Silver nanowires were initially characterized by using UV-visible and FTIR spectrophotometer. Synthesis of nanowires and involvement of functional groups was confirmed by FT-IR spectra. The morphology and particle size of synthesized Ag-NWs was determined using Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffraction (XRD). XRD results revealed cubic phase morphology of Ag-NWs. Nanowires were found having 12-8 μm length and 300-500 nm diameter. In addition, catalytic potential of the sample for degradation of methyl orange dye (MO) was tracked spectrophotometrically. The results exposed that; bio-synthesized silver nanowires were found having excellent morphological features as well as impressive catalytic potential.

Preparation and characterization of oxidized Multi-walled Carbon Nanotubes-Immobilized Aspergillus sp. Laccase Hybrid Materials

This work deals with preparation and characterization of immobilized laccase (Aspergillus sp.) over oxidized multi-walled carbon nanotubes (ox-MWCNTs) via simple mixing technique. The resulting materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and particle size distribution analysis using dynamic light scattering technique (DLS). The results showed that the TEM images exhibited more separate individual carbon bundles with particle size around of 396 nm after enzyme immobilization rather than the spaghetti-like tubes with size about 180 nm in the case of ox-MWCNTs. Also, the lowering in the zeta potential negative value (-5 mv) proved that the free carboxyl groups at ox-MWCNT surface were decreased after enzyme immobilization. Moreover, the thermal stability was decreased after enzyme immobilization using TGA. These results confirmed that the laccase could be reacted at the side walls of the ox-MWCNTs without structure damage. The biocatalytic effect of the immobilized laccase was investigated after its incubation with silver nitrate solution for 1 and 24 h. It can be concluded that the biocatalytic efficiency of the immobilized laccase could be enhanced after its incubation with silver nitrate solution for 24 h at room temperature relative to the free form. On the other hand, the enzyme stability was improved after immobilization up to 50ºC and at pH 3.0, while no remarkable differences on the activity values were observed for immobilized and free laccases at acidic pH range (4-6).