Due to their unique structural properties bacterial cellulose (BC) hydrogels find possible usage in many fields such as cosmetology, food industry, or medicine. In this study, photoactive BC ...hydrogels are investigated through modifications of their structural, mechanical, and pro‐oxidant properties resulting from graphene quantum dots (GQDs) encapsulation. Detailed structural analysis is conducted by atomic force microscopy, transmission electron microscopy and scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction method. Dynamic mechanical analysis is performed to study the changes in storage modulus, loss modulus and tan δ. Pro‐oxidative properties of new designed composites are tested by electron paramagnetic resonance (EPR). Structural and mechanical analyses show successful encapsulation of GQDs into BC whereas EPR measurements indicate high potential of these composites for singlet oxygen production.
Photoactive GQDs‐BC composite hydrogels are produced by immersing BC in GQDs acetone solution. Detailed structural, chemical and mechanical analyses show that photoactive GQDs are encapsulated into BC polymer matrix. Porosity test shows significant pore enlargement of GQDs‐BC composite hydrogels. Composite hydrogels are highly potent oxygen radical generator and present advanced material for wound dressing application.
It is well known that geopolymers are a new group of binder materials of alumosilicate origin. Geopolymers are made by the reaction of precursor aluminosilicate materials with alkaline activator ...solutions. The current research relates to a low-cost and eco-friendly procedure, suitable of being implemented in two easy steps. The first step is the production of a solid phase based on fly ash (Obrenovac, Serbia) and eggshell ash as waste materials rich in calcium. The second step is alkali activating the solid phase using an alkaline activator (a mixture of NaOH and Na2SiO3) and procedures in proper laboratory conditions. Four samples with different eggshell ash content were synthesized. The concentration of used NaOH was 12 mol dm−3. The structural properties of all investigated samples were analyzed by XRD (X-ray diffraction), DRIFT (diffuse reflectance infrared Fourier transform), SEM (scanning electron microscopy) and UV/Vis spectroscopy analysis. XRD determined the amorphous halo with the presence of quartz as the crystal phase in all of the investigated samples. These results were confirmed by DRIFT analysis. The morphology of the samples was determined by SEM analysis. UV/Vis showed that the material could be a potential adsorbent.
Unsaturated fatty acid (FA)–modified nanocellulose (m‐NC) shows potential application in improving mechanical properties of unsaturated polyester/m‐NC nanocomposites (UPe/m‐NC). A polyester matrix is ...obtained by polycondensation of maleic anhydride and products of poly(ethylene terephthalate) depolymerization with propylene glycol. Two methods of NC modification are performed: direct esterification with oleic acid, linseed, or sunflower oil FAs, and esterification/amidation with maleic acid/ethylene diamine (MA/EDA) bridging group followed by amidation with methyl ester of FAs. Increases of stress at break in the ranges from 148.8% to 181.4% and from 155.8% to193.0% for UPe/m‐NC composites loaded with 1 wt% of NC modified directly or via MA/EDA cross‐linker, respectively, are obtained. Results of the modeling of tensile modulus, by using the Cox–Krenchel model, show good agreement with experimentally obtained data. The effect of FAs' cross‐linking capabilities on the dynamic‐mechanical and thermal properties of the UPe/m‐NC is studied. Cross‐linking density, modulus, and Tg of the nanocomposite show appropriate relation with the unsaturation extent/structure of NC modification.
Nanocrystalline cellulose is functionalized directly with fatty acid (FA) or via a vinyl/amino (maleic acid/ethylene diamine, MA/EDA) bridge. Vinyl reactive FA residues at NC surface copolymerize with the polyester chains. The MA/EDA bridging group forms dipole/induced dipole interaction with polyester chains. The FA and MA/EDA/FA‐modified nanocrystalline cellulose shows high reinforcement in polyester‐based composites.
The study of Cu(II) from aqueous solutions using the adsorption process on synthetically modified geopolymers was performed under static conditions. Three geopolymers (based on metaphase of Serbian ...clay, metaphase of German clay and metaphase of German clay plus 10% of carbon cloth) were used. The geopolymers were made by condensing a mixture of metaphases and alkali activator solution at a fixed ratio at room temperature and then at a temperature of 60 °C in a dry oven. Then, the geopolymer samples were pre-crashed to a fixed-radius size. Their properties were characterized by X-ray diffractometry (XRD), Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). Adsorption experiments were carried out under batch process as a function of the dose, concentration of metal, and contact time. The uptake of Cu(II) was rapid, and it increased with increasing metal concentration. The sorption percentage decreased with increasing concentration of Cu(II). The equilibrium adsorption capacity of geopolymers was measured and extrapolated using more isotherms. The data fit very well the linear Langmuir isotherm model. The pseudo-second-order kinetic model can well describe the adsorption behavior of Cu(II) ions with geopolymers samples. These results show that used geopolymers hold great potential to remove Cu(II) from industrial wastewater.
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•Magnetometric studies of the BaTiO3/Fe2O3 samples prepared using five different chemical routes were done.•Decoration of BaTiO3 grains with hematite nanoparticles was observed ...instead.of a well defined core-shell structure.•Tendency of the iron-oxide nanoparticles to form agglomerates reduces the possibility of a continuous shell formation around the core.•Magnetic properties of these composites are dominated by the properties of fine iron-oxide nanopowder.
The manuscript shows the studies of structural and magnetic properties of BaTiO3/Fe2O3 samples prepared using five different chemical routes. We show that the undertaken processes leaded to the decoration of BaTiO3 grains with hematite nanoparticles, but not to a creation of a well-defined core-shell structure. These studies revealed that a strong tendency of the iron-oxide nanoparticles to form agglomerates, significantly reduces the possibility of a continuous shell formation around the core, and at the same time it promotes inter-particle interactions between magnetic nanoparticles. A detailed analysis of the results obtained in the structural and magnetic studies, allowed to state that magnetic properties of these composites are dominated by the properties of fine iron-oxide nanopowder. The collected isothermal magnetization curves clearly indicate the canted antiferromagnetic properties characteristic for hematite, while the ac magnetization results exhibit the collective freezing process to the cluster glass like state (characteristic for interacting system of magnetic nanoparticles). This work provides detailed studies of systems prepared under different conditions and methods, which can serve as an important step towards obtaining well defined BaTiO3/Fe2O3 core-shell structures.
Nickel-modified titanate/TiO2 catalysts were prepared by deposition of nickel ions onto hydrothermally prepared titanate supports, followed by hydrogen temperature-programmed reduction. Two different ...nickel precursors (hydroxide and carbonate) were used to tune reducibility and to vary the crystal phase structure of the final catalysts. The precursor reducibility and functional properties of the final catalysts were investigated systematically using various characterisation techniques. The results revealed a more facile reduction of the hydroxide precursor compared to its carbonate counterpart. Moreover, it was found that the formation of the anatase phase was favoured by the use of the hydroxide precipitation agent. The photocatalytic activity towards hydrogen production of the prepared catalysts was evaluated in the presence of 2-propanol under simulated solar light irradiation. A thorough study of the photocatalytic performance of the synthesised catalysts was conducted as a function of the precipitation agent used and the reduction temperature applied. The catalyst with dominant anatase crystal phase displayed the highest photocatalytic activity with a maximum H2 production rate of 1040 μmol h−1 g−1, this being more than four times higher than that of its carbonate counterpart. The catalysts with titanate structure showed similar activity, independent of the precipitation method used. The nanotubular structure was found to be the dominant factor in the stability of photocatalysts under long-run working conditions.
The goal of this study was to investigate the characteristics of grape skin extract (GSE) spray dried with different carriers: maltodextrin (MD), gum Arabic (GA) and skim milk powder (SMP). The grape ...skin extract was obtained from winery by-product of red grape variety
Prokupac
(
Vitis vinifera
L.). The morphology of the powders, their thermal, chemical and physical properties (water activity, bulk and tapped densities, solubility), as well as release studies in different pH conditions were analyzed. Total anthocyanin content and total phenolic content were determined by spectrophotometric methods. MD and GA-based microparticles were non-porous and spherical, while SMP-based ones were irregularly shaped. The process of spray drying
Prokupac
GSE using these three carriers produced powders with low water activity (0.24–0.28), good powder characteristics, high yields, and solubility higher than 90%. The obtained dissolution/release profiles indicated prolonged release of anthocyanins and phenolic compounds in different mediums, especially from GSE/GA microparticles. These results have shown that grape skin as the main by-product of wine production could be used as a source of natural colorants and bioactive compounds, and microencapsulation as a promising technique for the protection of these compounds, their stabilization in longer periods and prolonged release.
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