New packaging materials based on biopolymers are gaining increasing attention due to many advantages like biodegradability or existence of renewable sources. Grouping more antimicrobials agents in ...the same packaging can create a synergic effect, resulting in either a better antimicrobial activity against a wider spectrum of spoilage agents or a lower required quantity of antimicrobials. In the present work, we obtained a biodegradable antimicrobial film that can be used as packaging material for food. Films based on chitosan as biodegradable polymer, with ZnO and Ag nanoparticles as filler/antimicrobial agents were fabricated by a casting method. The nanoparticles were loaded with citronella essential oil (CEO) in order to enhance the antimicrobial activity of the nanocomposite films. The tests made on Gram-positive, Gram-negative, and fungal strains indicated a broad-spectrum antimicrobial activity, with inhibition diameters of over 30 mm for bacterial strains and over 20 mm for fungal strains. The synergic effect was evidenced by comparing the antimicrobial results with chitosan/ZnO/CEO or chitosan/Ag/CEO simple films. According to the literature and our preliminary studies, these formulations are suitable as coating for fruits. The obtained nanocomposite films presented lower water vapor permeability values when compared with the chitosan control film. The samples were characterized by SEM, fluorescence and UV-Vis spectroscopy, FTIR spectroscopy and microscopy, and thermal analysis.
One of the main problems faced by libraries, archives and collectors is the mold degradation of the paper-based documents, books, artworks etc. Microfungi (molds) emerge in regular storage conditions ...of such items (humidity, usually over 50%, and temperatures under 21 °C). If the removal of the visible mycelium is relatively easy, there is always the problem of the subsequent appearance of mold as the spores remain trapped in the cellulosic, fibrillary texture, which acts as a net. Moreover, due to improper hand hygiene bacteria contamination, old books could represent a source of biohazard, being colonized with human pathogens. An easy and accessible method of decontamination, which could offer long term protection is therefore needed. Here, we present a facile use of the ZnO nanopowders as antimicrobial agents, suitable for cellulose-based products, conferring an extended antibacterial and anti-microfungal effect. The proposed method does not adversely impact on the quality of the cellulose documents and could be efficiently used for biodegradation protection.
Cotton textile waste (CW) and crushed bricks (CB) are wastes generated by the textile and construction industries that cause adverse effects on the environment. This paper explores the effect of ...adding 1, 2, 5, and 10 wt.% of CW and CB, instead of natural sand under 1 mm (50 to 100 vol.%), on the properties of concrete. The study included the analysis of workability, density, water absorption, thermal conductivity, mechanical strengths, and electron microscopy. The results show that the presence of CW and CB increased the water required to obtain the same slump value as reference, R. Concretes with CW provided better performance in terms of density, water absorption (for 1 wt.%), and splitting strength (for 1 to 2 wt.%). The 28 days of compressive strength decreased with increasing CW (33.3 MPa for R and 26.9 MPa for 2 wt.% of CW). The partial substitution of sand decreased the workability and density and increased the mechanical strength of concrete. The presence of both CW and CB decreased workability, density, and mechanical strengths. Regarding the ability of concrete to transfer heat, the addition of CW and CB decreased the thermal conductivity value (e.g., 0.32 W/(m·K) for 1 wt.% of CW compared to 0.37 W/(m·K) for reference).
Airborne particulate matter (PM) are a major environmental pollutant adversely affecting human health. Exposure to atmospheric PM is correlated with significant damages to physiological systems from ...respiratory and circulatory level to reproductive and central nervous systems. The paper describes the elemental composition of a particular category of PM2.5 – microspheres, originate in exhaust pipes of automobiles and deposited onto vegetation planted along the roads. Microspheres were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). Based on size and chemical composition, the hazard on human health of identified microspheres was evaluated. SEM investigation showed that microspheres size was between 3 and 0.5 μm. EDX analysis indicate that microspheres have a complex elemental structure, which concentrate mainly Si and Al in combination with Mg, Na, Fe, K, Ca and Cl, and seldom Ba and Ti. Our results showed that detected airborne microsphere are breathable and potential harmful to human health.
This work proposes a new method for obtaining poly(3-hydroxybutyrate) (PHB)/microfibrillated cellulose (MC) composites with more balanced properties intended for the substitution of petroleum-based ...polymers in packaging and engineering applications. To achieve this, the MC surface was adjusted by a new chemical route to enhance its compatibility with the PHB matrix: (i) creating active sites on the surface of MC with γ-methacryloxypropyltrimethoxysilane (SIMA) or vinyltriethoxysilane (SIV), followed by (ii) the graft polymerization of methacrylic acid (MA). The high efficiency of the SIMA-MA treatment and the lower efficiency in the case of SIV-MA were proven by the changes observed in the Fourier transform infrared FTIR spectra of celluloses. All modified celluloses and the PHB composites containing them showed good thermal stability close to the processing temperature of PHB. SIMA-modified celluloses acted as nucleating agents in PHB, increasing its crystallinity and favoring the formation of smaller spherulites. A uniform dispersion of SIMA-modified celluloses in PHB as a result of the good compatibility between the two phases was observed by scanning electron microscopy and many agglomerations of fibers in the composite with unmodified MC. The dual role of SIMA-MA treatment, as both compatibilizer and plasticizer, was pointed out by mechanical and rheological measurements. This new method to modify MC and obtain PHB/MC composites with more balanced stiffness–toughness properties could be a solution to the high brittleness and poor processability of PHB-based materials.
•PLGA-Fe3O4@G coatings with antimicrobial properties.•Uniform coatings.•Biocompatible surfaces.
The aim of this study was to obtain improved coatings for advanced surfaces with increased ...biocompatibility and resistance to microbial colonization and biofilm formation. The prepared magnetite nanoparticles functionalized with gentamicin (Fe3O4@G) have been embedded into poly(lactic-co-glycolic acid) (PLGA) spheres by oil-in-water emulsion. The PLGA-Fe3O4@G spheres were deposited on glass and silicone surfaces by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The obtained thin coatings were analyzed by Scanning Electron Microscopy (SEM) and Infrared Microscopy (IRM). The antimicrobial and antibiofilm efficiency of coatings was tested with respect to Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) clinical strains by viable cells counts assay, performed at different time intervals. The obtained results proved that coatings based on PLGA-Fe3O4@G spheres exhibited an efficient antimicrobial activity against both adherent and sessile bacterial cells. Besides their excellent anti-adherence and antibiofilm effect, the obtained MAPLE-deposited coatings were highly biocompatible, allowing the normal development and growth of cultured human amniotic fluid stem cells. This approach could be successfully applied for the optimization of medical surfaces in order to control and prevent microbial colonization and further development of biofilm associated infections.
Zinc oxide has attracted wide research interest due to its unique properties. Its band gap width, high refractive index, high electrical conductivity, and high optical transmission in the visible, ...etc., have made it suitable for a variety of applications, such as gas sensors, varistors, optoelectronic devices, etc. The first part of the paper presents three methods for the synthesis of zinc oxide nanoparticles: sol–gel, polyol, and hydrothermal methods. Then, we report on the characteristics of the powders in terms of structure, composition and morphology as well as of in-vitro testing on cell cultures. The influence of the nanoparticles on cell viability was evaluated by the lactate dehydrogenase method. It turns out that all ZnO powders tested present high cytotoxicity. Also, it is found that the synthesis method significantly influences cell viability, the lowest one being obtained for nanopowders synthesized by the sol–gel method.
The aim of the research was to prepare silica adsorbents using an environmentally friendly pathway, a template synthesis with saponin biosurfactant as a structure-directing agent. The adsorbents ...prepared in this way exhibit improved adsorption properties while maintaining environmental innocuousness. For the preparation of porous silica, the biosurfactant template sol–gel method was used with tetraethoxysilane as a silica precursor. The silica adsorbents were analyzed by FTIR spectroscopy, nitrogen adsorption–desorption and SEM/EDX microscopy, TEM/HRTEM microscopy, and thermogravimetric analyses. Batch tests were carried out to remediate Pb(II)/Cd(II) ions in single/binary aqueous solutions, and the effect of the surfactant on the adsorption properties was assessed. The optimal adsorption parameters (pH, contact time, initial concentration of metal ions) have been determined. The adsorption was fitted using Langmuir and Freundlich adsorption isotherms and kinetic models. Mathematical modeling of the retention process of Pb(II) and Cd(II) ions from binary solutions indicated a competitive effect of each of the two adsorbed metal ions. The experimental results demonstrated that saponin has the effect of modifying the silica structure through the formation of pores, which are involved in the retention of metal ions from aqueous solutions and wastewater.
Polymer nanodielectrics characterized by good flexibility, processability, low dielectric loss and high dielectric permittivity are materials of interest for wearable electronic devices and ...intelligent textiles, and are highly in demand in robotics. In this study, an easily scalable and environmentally friendly method was applied to obtain polysiloxane/nanosilica nanocomposites with a large content of nanofiller, of up to 30% by weight. Nanosilica was dispersed both as individual particles and as agglomerates; in nanocomposites with a lower amount of filler, the former prevailed, and at over 20 wt% nanosilica the agglomerates predominated. An improvement of both the tensile strength and modulus was observed for nanocomposites with 5-15 wt% nanosilica, and a strong increase of the storage modulus was observed with the increase of nanofiller concentration. Furthermore, an increase of the storage modulus of up to seven times was observed in the nanocomposites with 30 wt% nanosilica. The tensile modulus was well fitted by models that consider the aggregation of nanoparticles and the role of the interface. The dielectric spectra showed an increase of the real part of the complex relative permittivity with 33% for 30 wt% nanosilica in nanocomposites at a frequency of 1 KHz, whereas the loss tangent values were lower than 0.02 for all tested nanodielectrics in the radio frequency range between 1 KHz and 1 MHz. The polysiloxane-nanosilica nanocomposites developed in this work showed good flexibility; however, they also showed increased stiffness along with a stronger dielectric response than the unfilled polysiloxane, which recommends them as dielectric substrates for wearable electronic devices.
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