Biocidal effects of organometallic materials supported on ZSM-5 Zeolite: Influence of the physicochemical and surface properties.

Antifouling coatings containing biocidal agents can be used to prevent the accumulation of biotic deposits on submerged surfaces; however, several commercial biocides can negatively affect the ecosystem. In this study, various formulations of a potential biocide product comprising copper nanoparticles and capsaicin supported on zeolite ZSM-5 were analyzed to determine the influence of the concentration of each component. The incorporation of copper was evidenced by scanning electron microscopy and energy dispersive spectroscopy. Similarly, Fourier-transform infrared spectroscopy confirmed that capsaicin was supported on the zeolite surface. The presence of capsaicin on the external zeolite surface significantly reduced the surface area of the zeolite. Finally, bacterial growth inhibition analysis showed that copper nanoparticles inhibited the growth of strains Idiomarina loihiensis UCO25, Pseudoalteromonas sp. UCO92, and Halomonas boliviensis UCO24 while the organic component acted as a reinforcing biocide.

Towards recycling of waste carbon fiber: Strength, morphology and structural features of recovered carbon fibers.

Carbon fiber is one of the most widely used materials in high demand applications due to its high specific properties, however, its post-recycling properties limit its use to low performance applications. In this research, the carbon fiber recovering is examined using two methods: two-step pyrolysis and microwave-assisted thermolysis. The results indicate that the fibers recovered by pyrolysis show reduced surface and structural damage, maintaining the original mechanical properties of the fiber with losses below 5%. The fibers recovered by microwaves undergo significant surface changes that reduce their tensile strength by up to 60% and changes in their graphitic structure, increasing their degree of crystallinity by Raman index ID/IG from 1.98 to 2.86 and their amorphous degree by ID"/IG ratio from 0.411 to 1.599. Recovering fibers from microwave technique is 70% faster compared to two step pyrolysis, and provides recycled fibers with superior surface activation with the presence of polar functional groups -OH, -CO, and -CH that react with the epoxy matrix. The thermal, morphological, structural and mechanical characterizations of the recovered fibers detailed in this work provide valuable findings to evaluate their direct reuse in new composite materials.

Ultrafast carbon nanotubes growth on recycled carbon fibers and their evaluation on interfacial shear strength in reinforced composites.

The global demand for products manufactured with carbon fibers (CFs) has increased in recent years; however, the waste generated at the end of the product lifetime has also increased. In this research, the impact of the addition of carbon nanotubes (CNTs) on the interlaminated resistance of recycled carbon fibers (RCFs) was studied. In this work, a recycling process of the composite material was applied via thermolysis to obtain the CFs, followed by the growth of CNTs on their surface using the Poptube technique. The recycling temperature were 500 °C and 700 °C; and ferrocene and polypyrrole were used to grow CNTs on CFs surface. CNTs were verified by Raman spectroscopy and scanning electron microscopy (SEM). Finally, to determine the interlaminar resistance, a double cantilever beam (DCB) test was performed. The results indicate that with Poptube technique, CNTs can be grown on RCFs using both impregnations. Thermolysis recycling process at 500 °C allowed CFs without resin residues and without visible damage. The DCB tests showed a decrease in the fracture resistance in mode I loading of 34.9% for the polypyrrole samples and 29.3% for the ferrocene samples compared with the virgin carbon fibers (VCFs) samples with a resistance of 1052.5 J/m2.

Dual antifungal activity against Candida albicans of copper metallic nanostructures and hierarchical copper oxide marigold-like nanostructures grown in situ in the culture medium.

AIMS: This study aimed to determine in vitro activity of copper nanoparticles and copper nanowires against Candida albicans strains and to assess their effects on morphology and submicron structure. METHODS AND RESULTS: The microdilution method determined the minimal inhibitory concentration (MIC) of copper nanoparticles (CuNPs) and copper nanowires (CuNWs) against three strains of C. albicans: ATCC 10231 and two clinical strains (C and E). Effects on the morphology and ultrastructure of C. albicans strains were examined by scanning electron microscopy and transmission electron microscopy. MIC for CuNPs was 129·7 µg ml-1 for strain ATCC 10231, 1037·5 µg ml-1 for strain C and 518·8 µg ml-1 for strain E. MIC for CuNWs was similar for all strains tested (260·3 µg ml-1 ). SEM and TEM studies showed alterations in morphology, cell wall and the complete collapse of the yeast after incubation with CuNPs. In contrast, most of the yeast cells maintained their structure with an intact cell wall, and only decreased the number and size of fimbriae when C. albicans was exposed to CuNWs. CuNPs and CuNWs formed hierarchical copper oxide nanostructures growing in situ in the culture medium. Results suggest a dual mechanism for antifungal activity: (i) free Cu2+ ions act as a biocide, (ii) sharp edges of marigold-like petal nanostructures could injure the cellular wall and membrane and cause the death of the yeast. CONCLUSIONS: CuNPs and CuNWs inhibited the growth of the three strains of C. albicans tested. Moreover, CuNPs disrupted cell wall with leakage of the cytoplasmic content. Each concentration of the series used for the determination of the activity of CuNPs and nanowires against C. albicans formed copper oxide marigold-like nanostructures. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that CuNPs and CuNWs are good candidates for formulating new therapeutic agents for candidiasis.

Comparative Study of the Antimicrobial Effect of Nanocomposites and Composite Based on Poly(butylene adipate-co-terephthalate) Using Cu and Cu/Cu2O Nanoparticles and CuSO4.

Nanocomposites and a composite based on poly(butylene adipate-co-terephthalate) (PBAT) were synthesized using commercial copper nanoparticles (Cu-NPs), copper/cuprous oxide nanoparticles (Cu|Cu2O-NPs), and copper sulfate (CuSO4), respectively. The Cu|Cu2O-NPs were synthesized using chemical reduction and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synthesis of Cu|Cu2O-NPs yielded a mixture of Cu and Cu2O, with metal Cu having a spherical morphology of approximately 40 nm in diameter and Cu2O with a diameter of 150 nm. To prepare the nanocomposites (NCs) and the composite material (MC), the NPs and the CuSO4 salt were incorporated into the PBAT matrix in concentrations of 1, 3, and 5% p/p via an ex situ method. Fourier transform infrared spectroscopy (FTIR), a tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and agar diffusion assays were used for structural, thermomechanical, and antimicrobial characterization. Results showed that the reinforcements did not modify the chemical structure of the PBAT and only slightly increased the percentage of crystallization. The mechanical and thermal properties of the PBAT did not change much with the addition of fillers, except for a slight increase in tensile strength and thermal stability, respectively. The agar diffusion antimicrobial assays showed that the NCs and MCs had good inhibitory responses against the nonresistant strains Enterococcus faecalis, Streptococcus mutans, and Staphylococcus aureus. The MCs based on CuSO4 had the highest biocidal effect, even against the resistant bacteria Acinetobacter baumannii.

Synthesis of Copper Nanowires and Their Antimicrobial Activity on Strains Isolated Persistent Endodontic Infections.

Copper nanowires, Cu-NWs may have a good antimicrobial effect in endodontic treatment. The objective of this work was to synthesize, characterize and evaluate the antibacterial activity of Cu-NWs on strains obtained from human root canal. A wide distribution of Cu-NWs diameters from 30 to 90 nm was obtained with lengths ranging from 5 to 40 µm. Structural analysis of Cu-NWs showed crystalline planes, which corresponded to Cu, with preferential growth in the direction [110]. The geometric mean MICs was of 289.30 µg/mL, with a MIC50 of 256 µg/mL and a MIC90 of 512 µg/mL for Cu-NWs. Cellular viability of 28 a biofilm tends to decrease the longer it is exposed to Cu-NWs. Synthesized and characterized Cu-NWs have a good antimicrobial effect against clinical strains used in the present study and has a potential to be used for disinfection of the root canal system.

Fabrication and characterization of a diluted magnetic semiconducting TM co-doped Al:ZnO (TM=Co, Ni) thin films by sol-gel spin coating method.

Effect of transition metal oxides (TM=Co and Ni) co-doping on the crystallinity, surface morphology, grain growth and magnetic properties of nanostructure Al:ZnO thin films has been studied for diluted magnetic semiconductor applications. Al:ZnO thin films were fabricated by sol-gel spin coating on p-type Si (100) substrates. Fabrication of hexagonal wurtzite TM co-doped Al:ZnO thin films having thickness 2µm was successfully achieved. The Raman spectra of the TM co-doped Al:ZnO thin films showed a broad vibrational mode in the range 520-540cm(-1) due to crystal defects created co-doping elements in the ZnO host lattice. Scanning electron microscopy (SEM) revealed that the films are composed of uniform size, polycrystalline dense ZnO particles with defect free, smooth surfaces. The surface roughness was further verified with atomic force microscopy (AFM). The energy dispersive X-ray spectroscopic analysis (EDX) confirmed the stoichiometric compositions of the TM co-doped Al:ZnO films. The magnetic measurements exhibited that the Co, Al:ZnO and Ni, Al:ZnO thin films were ferromagnetic at room temperature.

Synthesis and characterization of gallium colloidal nanoparticles.

In this work, gallium colloidal nanoparticles (Ga-Nps) were synthesized by chemical liquid deposition (CLD). This method involved the deposition of metallic atoms with organic solvents (THF, acetone and 2-propanol) in a freezing matrix of the solvent at 77K, in order to obtain core-shell Ga-Nps which were characterized by: FT-IR, UV-Vis, TEM, SAED and electrophoretic mobility measurements. TEM images revealed a wide distribution of the apparent size of the particles and apparent average size of 5.65, 8.11 and 13.87 nm for Ga-Nps obtained with 2-propanol, THF and acetone, respectively. UV spectra showed absorption bands of metal plasmons, interesting quantum size effects and plasmon absorption bands of particles aggregated to lambda(280) and lambda(325). Electrophoretic mobility allowed to evidence that nanoparticles had a negative charge as well as to observe that the zeta potential of the colloidal dispersions decreased over time, showing a significant tendency to the aggregation of Ga-Nps. The importance of the functionalization of metal nanoparticles with high dielectric constant solvents in the stabilization of colloidal systems was also observed. FT-IR spectroscopy revealed that the interaction of Ga surface with the solvent possibly produces a (GaC) bond. Experimental details, structural and thermal stability studies were also analyzed in this work.