Synthesis, characterization and antibacterial activity of copper, nickel and bimetallic Cu–Ni nanoparticles for potential use in dental materials

AbstractThe antibacterial effect is a desirable property in dental materials. Development of simple methods for the preparation of nanosized metal particles has attracted significant attention because of their future applications due to unusual size-dependent antibacterial properties. Copper (Cu), Nickel (Ni) and bimetallic Cu–Ni nanoparticles were prepared by a simple chemical method and their antibacterial activity was tested against the widely used standard human pathogens Staphylococcus aureus (gram-negative) and Escherichia coli (gram-positive). Additionally, these nanoparticles were tested against the dental pathogen Streptococcus mutans. Our results are promising for potential use in dental materials science

Evaluation of Self-Etching Adhesive and Er:YAG Laser Conditioning on the Shear Bond Strength of Orthodontic Brackets

The purpose of this study was to evaluate the shear bond strength, the adhesive remnant index scores, and etch surface of teeth prepared for orthodontic bracket bonding with self-etching primer and Er:YAG laser conditioning. One hundred and twenty bovine incisors were randomly divided into four groups. In Group I (Control), the teeth were conditioned with 35% phosphoric acid for 15 seconds. In Group II the teeth were conditioned with Transbond Plus SEP (5 sec); III and IV were irradiated with the Er:YAG 150 mJ (11.0 J/cm2), 150 mJ (19.1 J/cm2), respectively, at 7–12 Hz with water spray. After surface preparation, upper central incisor stainless steel brackets were bonded with Transbond Plus Color Change Adhesive. The teeth were stored in water at 37°C for 24 hours and shear bond strengths were measured, and adhesive remnant index (ARI) was determined. The conditioned surface was observed under a scanning electron microscope. One-way ANOVA and chi-square test were used. Group I showed the significantly highest values of bond strength with a mean value of 8.2 megapascals (MPa). The lesser amount of adhesive remnant was found in Group III. The results of this study suggest that Er:YAG laser irradiation could not be an option for enamel conditioning

Ferromagnetic resonance study on the influence of the electrolytic bath acidity on the magnetic anisotropy of Ni nanowires

n this work, a ferromagnetic resonance study on the influence of the electrolytic bath acidity on the magnetic anisotropy and hardness parameter of arrays of 50 nm diameter Ni nanowires in porous alumina membranes, is reported. Fine tuning the effective magnetic anisotropy of the arrays has been achieved by progressively changing the nanowires microstructure from polycrystalline textured to single-crystalline as the electrolyte acidity is reduced. The micro-structural analysis carried out by X-ray diffraction and high resolution transmission electron microscopy has revealed that a preferred crystal texture is not a sufficient condition for the enhancement of the magnetic anisotropy. Instead, a correlation between the increase of crystallite size and quality, and the increase of both the magnetic anisotropy and hardness parameter has been shown. Ferromagnetic resonance and alternating gradient magnetometry experiments have shown that no additional magnetic contributions take place in Ni NWs grown from highly acidic electrolytes (pH 1.6), whereas a significant additional anisotropy contribution progressively appears as the electrolyte acidity is reduced (pH 5.0). Besides the careful adjustment of electrodeposition conditions, achieving a very long length for the nanowires is also a key requirement to have a precise control on the effective magnetic anisotropy energy, which can be fine tuned in the wide range from 64 − 167 kJ⋅m− 3 as a result of an energy enhancement of magnetoelastic origin. Ferromagnetic resonance measurements have demonstrated that nanocomposites based on arrays of nanowires made of low cost and abundant elements like Ni exhibit hardness parameters in the range 0.47–0.75 within the semihard region, where those with κ > 0.5 are suitable for permanent magnet applications. These features make arrays of low diameter Ni nanowires very appealing for their use in the development of agile microwave and spintronic devices

Efficient Removal of Heavy Metals from Aqueous Solutions Using a Bionanocomposite of Eggshell/Ag-Fe

Eggshell and an easily synthesized bionanocomposite of eggshell with Ag-Fe nanoparticles demonstrated to be efficient adsorbent materials for the removal of lead, arsenic, and mercury from water. The natural material and the bionanocomposite were characterized by TEM and XRD. Ag-Fe nanoparticles vary from 1 to 100 nm in size. Equilibrium times of the adsorption systems were achieved between 4 and 8 h. The experimental adsorption data fitted the pseudo-second and Elovich models; therefore, the adsorption of heavy metals ions took place mainly by a chemical process. The adsorption capacity of eggshell in mg/g was 7.01 for As5+, 3.90 for Pb2+, and 1.51 for Hg2+, while the nanocomposite adsorption capacity was 17.7 for As5+, 27.8 for Pb2+ and 15.88 for Hg2+

Polyurethane-Keratin Membranes: Structural Changes by Isocyanate and pH, and the Repercussion on Cr(VI) Removal

Keratin has the capacity to interact with metal ions. In order to take advantage of this potential, a novel membrane with polyurethane and keratin has been developed and studied for removal of Cr(VI) from aqueous solution. Physicochemical and morphological properties of these hybrid membranes were studied, varying synthesis parameters such as the type of isocyanate and pH in keratin solution. The effects of using diphenyl-methane-diisocyanate or toluene-diisocyanate and modifying the pH in keratin solutions were evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, and dynamical mechanical analysis. Results show that pH has a strong influence on morphology and on Cr(VI) removal efficiency. When pH in keratin solution is low (2.5), the protein separates from water, and a more closed cell in the membrane is obtained affecting its mechanical properties. The removal efficiency of Cr(VI) was also assessed at different pH values of chromium solutions. These results show that when pH of the Cr solution is acidic (at 1.5), the Cr(VI) removal percentages increase significantly, reaching up to a 58%. Thus this paper demonstrates the successful combination of synthetic and natural polymers depending on the process parameters to be applied in the critical purpose of remediation of Cr(VI) contamination

Antimicrobial Activity of Biogenic Silver Nanoparticles from Syzygium aromaticum against the Five Most Common Microorganisms in the Oral Cavity

Syzygium aromaticum (clove) has been used as a dental analgesic, an anesthetic, and a bioreducing and capping agent in the formation of metallic nanoparticles. The main objective of this study was to evaluate the antimicrobial effect in oral microorganisms of biogenic silver nanoparticles (AgNPs) formed with aqueous extract of clove through an ecofriendly method “green synthesis”. The obtained AgNPs were characterized by UV-Vis (ultraviolet-visible spectroscopy), SEM-EDS (scanning electron microscopy–energy dispersive X-ray spectroscopy), TEM (transmission electron microscopy), and ζ potential, while its antimicrobial effect was corroborated against oral Gram-positive and Gram-negative microorganisms, as well as yeast that is commonly present in the oral cavity. The AgNPs showed absorption at 400–500 nm in the UV-Vis spectrum, had an average size of 4–16 nm as observed by the high-resolution transmission electron microscopy (HR-TEM), and were of a crystalline nature and quasi-spherical form. The antimicrobial susceptibility test showed inhibition zones of 2–4 mm in diameter. Our results suggest that AgNPs synthesized with clove can be used as effective growth inhibitors in several oral microorganisms