Graphene oxide nanoplatelets (GO) were prepared from expanded graphite (EG) and functionalized with triethylenetetramine (GO-TETA). The GO-TETA consisted of a few layers of graphene (~4–6 layers), as determined by atomic force microscopy and Raman spectroscopy. X-ray photoelectron spectroscopy showed that the TETA was covalently linked to the GO in the GO-TETA sample. Epoxy composites based on the diglycidyl ether of bisphenol A with TETA as a hardener and with 0.5–3.0 wt% additions of EG and GO-TETA were investigated. The results showed that the addition of the nanofillers led to an increase of ~20 °C in the glass transition temperature. A slight increase in the ratio of the elastic modulus/hardness of the nanocomposites was observed by nanoindentation tests carried out at a depth range of 300 nm–1.3 μm; these tests indicated a tendency of increased fracture toughness. Microindentation had an enhancement of 40 % in hardness for the 1 wt% composite with GO-TETA relative to the corresponding value for the neat epoxy. 相似文献
We investigate the fabrication of nanometric patterns on silicon surfaces by using the parallel-local anodic oxidation technique with soft stamps. This method yields silicon oxide nanostructures 15?nm high, namely at least five times higher than the nanostructures made with local anodic oxidation using atomic force microscopy, and thanks to the size of the stamp enables one to pattern the surface across a centimetre length scale. To implement this technique, we built a machine to bring the metallized polydimethylsiloxane stamp in contact with the silicon surface, subsequently inserted in a sealed chamber with controlled relative humidity. The oxide nanostructures are fabricated when a bias voltage of 36?V is applied between the stamp and the silicon for 2?min, with a relative humidity of 90%. The flexibility of the stamp enables a homogeneous conformal contact with the silicon surface, resulting in an excellent reproducibility of the process. Moreover, by means of two subsequent oxidations with the same stamp and just rotating the sample, we are able to fabricate complex nanostructures. Finally, a detailed study of the oxidation mechanism, also using a finite element analysis, has been performed to understand the underlying mechanism. 相似文献
This study aimed to evaluate the effects of hesperidin (HE) on in vitro osteoclastogenesis and dietary supplementation on mouse periodontal disease and femoral bone phenotype. RAW 264.7 cells were stimulated with RANKL in the presence or absence of HE (1, 100 or 500 µM) for 5 days, and evaluated by TRAP, TUNEL and Western Blot (WB) analyses. In vivo, C57BL/6 mice were given HE via oral gavage (125, 250 and 500 mg/kg) for 4 weeks. A sterile silk ligature was placed between the first and second right maxillary molars for 10 days and microcomputed tomography (μCT), histopathological and immunohistochemical evaluation were performed. Femoral bones subjected or not to dietary HE (500 mg/kg) for 6 and 12 weeks were evaluated using μCT. In vitro, HE 500 µM reduced formation of RANKL-stimulated TRAP-positive(+) multinucleated cells (500 µM) as well as c-Fos and NFATc1 protein expression (p < 0.05), markers of osteoclasts. In vivo, dietary HE 500 mg/kg increased the alveolar bone resorption in ligated teeth (p < 0.05) and resulted in a significant increase in TRAP+ cells (p < 0.05). Gingival inflammatory infiltrate was greater in the HE 500 mg/kg group even in the absence of ligature. In femurs, HE 500 mg/kg protected trabecular and cortical bone mass at 6 weeks of treatment. In conclusion, HE impaired in vitro osteoclastogenesis, but on the contrary, oral administration of a high concentration of dietary HE increased osteoclast numbers and promoted inflammation-induced alveolar bone loss. However, HE at 500 mg/kg can promote a bone-sparing effect on skeletal bone under physiological conditions. 相似文献
The ideal food packaging materials are recyclable, biodegradable, and compostable. Starch from plant sources, such as tubers, legumes, cereals, and agro-industrial plant residues, is considered one of the most suitable biopolymers for producing biodegradable films due to its natural abundance and low cost. The chemical modification of starch makes it possible to produce films with better technological properties by changing the functional groups into starch. Using biopolymers extracted from agro-industrial waste can add value to a raw material that would otherwise be discarded. The recent COVID-19 pandemic has driven a rise in demand for single-use plastics, intensifying pressure on this already out-of-control issue. This review provides an overview of biopolymers, with a particular focus on starch, to develop sustainable materials for food packaging. This study summarizes the methods and provides a potential approach to starch modification for improving the mechanical and barrier properties of starch-based films. This review also updates some trends pointed out by the food packaging sector in the last years, considering the impacts of the COVID-19 pandemic. Perspectives to achieve more sustainable food packaging toward a more circular economy are drawn. 相似文献
This work reports the magnetite-functionalization and biological evaluation of eugenol by the co-precipitation method employed only Fe2+ under mild conditions and control from the amount of the incorporated magnetite. Magnetic nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), hydrodynamic size distribution (Zetasizer), and vibrating sample magnetometer (VSM). SEM images showed that EUG·Fe3O4 similar in shape to a nanoflower. The FTIR spectrum confirmed the presence of characteristic EUG and Fe3O4 bands in the EUG·Fe3O4 sample, the XRD analysis showed that the magnetite functionalization with eugenol slightly affected the Fe3O4 crystal structure, while the VSM measurements demonstrate that EUG·Fe3O4 1:1 shows a superparamagnetic behavior, suggesting small non-interacting particles. The in vitro safety profile and cytotoxicity of free eugenol, magnetite pristine, EUG·Fe3O4 1:1, EUG·Fe3O4 1:5, and EUG·Fe3O4 1:10 was investigated using human cell lines (keratinocytes and melanoma). The results demonstrate the high biocompatibility of EUG·Fe3O4 in HaCat cells and the greater specificity for the A375 cell line. Furthermore, the magnetite-functionalization with eugenol decreased the toxic effects of free eugenol on healthy cells. Antibacterial tests were performed in different bacterial strains. The experimental data showed that among the magnetic compounds, the microorganisms were only sensitive to treatment with EUG·Fe3O4 1:1. Regarding the antibiofilm activity assay, it can be observed that only the EUG·Fe3O4 caused a significant decrease in biomass when compared to the positive control. Finally, it can be concluded that EUG·Fe3O4 proves to be a potential candidate for future studies for drug delivery of cancer and bacterial infections treatments.