Thermodynamic parameters (densities, viscosities, speed of sound, and refractive index) of four series of alkaline activators were determined over the temperature range from 15 to 60 degreesC for the ...pro cess of geopolymerization. Mixtures of Na.sub.2SiO.sub.3 and NaOH of different molar concentrations (from 2M to 8M with step 2) were used as an alkaline activator. The sample with the highest NaOH concentration also shows the highest values of all thermodynamic parameters. Metakaolin, obtained by calcination of kaolin at 750 degreesC, was used as the starting material. The samples were characterized by X-ray diffraction (XRD), FTIR and Raman spectroscopy, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-Ray (EDX) Spectroscopy. Results of FTIR analysis correlated with results of Raman Spectroscopy. Due to the polymerization process, the changes in the phonon spectrum were confirmed. The different concentrations of activators do not notably change the Si/Al ratio. Keywords: geopolymer; density; viscosity; speed of sound; refractive index; FTIR; Raman spectroscopy
This study aimed to evaluate the physical (particle size and ζ-potential) and techno-functional properties (emulsifying and foaming) of goat milk powders enriched with grape pomace seed extract ...(TME), as promising food ingredients in the formulation of functional food. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman spectroscopies, along with advanced chemometric tools were employed as well as Scanning Electron Microscopy (SEM) for analyzing TME powders. All powders exhibited a unimodal particle size distribution and ζ-potential values more negative than −36 mV. ATR-FTIR and Raman spectroscopies combined with principal component analysis (PCA) demonstrated distinct separation among skimmed goat milk (M), thermally treated skimmed goat milk (TM), and TME powders in different spectral regions (amide I, II, III, and fingerprint region). This separation resulted from the applied thermal treatment, the presence of phenolic compounds and their complexes with goat milk proteins, and the formation of Maillard reaction products. SEM analysis confirmed the different morphology and shapes of M, TM and TME powders. The 0.1% solutions of M, TM and TME exhibited good emulsifying properties (emulsion activity index and emulsion stability index) but showed poor foaming properties, except for the M sample. Solution concentrations higher than 0.1% for all samples (0.5% and 1.0%) displayed poor techno-functional properties. In summary, a schematic representation of the arrangement of casein micelles in 0.1% M, TM and TME samples, on oil/water and air/water surfaces was provided. The production of TME powders represents an innovative strategy for waste recovery in the production of functional food ingredients with good emulsifying properties.
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•Heated goat milk (TM) were mixed with grape pomace seed (SE) extracts.•SE extracts didn't significantly change the ζ-potential of goat milk micelles.•Changes in the secondary structure of milk proteins were observed after SE addition.•Different microstructures of goat milk powders were found by SEM.•0.1% solutions of goat powders showed good emulsifying and poor foaming properties.
Gamma irradiation provides an alternative pathway to conventional gold nanoparticle synthesis because it is simple, fast, and economical. Here, we employed gamma irradiation at low doses (1–20 kGy) ...to obtain gold nanoparticles (Au NPs) anchored onto graphene oxide (GO) sheets. GO was selected as a suitable platform for the nucleation and growth of Au NPs because of its large surface area and good dispersibility in water due to the presence of polar oxygen-containing functional groups in its structure. Gamma irradiation at all the applied doses led to the reduction of chloroauric acid and the formation of evenly distributed Au NPs at the GO surface, simultaneously causing the reduction of GO and partial restoration of the graphene structure. As-prepared Au NPs have predominately spheric shapes and the smallest nanoparticles were reported for the dose of 1 kGy. The increase in the irradiation dose caused either the growth of larger particles (5 and 10 kGy) or the broad distribution of particles’ sizes (20 kGy). All samples showed a temperature increase upon exposure to 800 nm laser and photothermal efficiency was the highest for the sample prepared at 20 kGy.
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•Low-dose gamma irradiation was employed to obtain gold nanoparticles anchored onto graphene oxide sheets.•Gold nanoparticles were homogeneously distributed at the graphene oxide surface and have predominately spheric shapes.•The smallest nanoparticles were reported for the dose of 1 kGy.•An increase in the irradiation dose caused the change in particles’ sizes.•The photothermal efficiency was the highest for the sample prepared at 20 kGy.
The paper presents chemical and structural analysis of geopolymer materials which are obtained by alkali-activated calcined clay (metakaolin) originated from Serbia under strictly defined conditions. ...Characterization of the metakaolin and geopolymers molecular structure has been done using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The paper presents the possibility of obtaining geopolymer structure and differences in chemical and structural characterization of these materials taking into account the concentration of NaOH as a variable parameter. The results of MALDI analysis of metakaolin and synthesized geopolymer structures using various matrix system: 2,4,6 trihydroxyacetophenone (THAP), α-cyano-4-hydroxycinnamic, 2,6 dihydroxyacetophenone and laser desorption/ionization, have shown that THAP matrix is the most appropriate for analysing these aluminosilicate materials.
Nowadays, it is a great challenge to develop new medicines for treating various infectious diseases. The treatment of these diseases is of utmost interest to further prevent the development of ...multi-drug resistance in different pathogens. Carbon quantum dots, as a new member of the carbon nanomaterials family, can potentially be used as a highly promising visible-light-triggered antibacterial agent. In this work, the results of antibacterial and cytotoxic activities of gamma-ray-irradiated carbon quantum dots are presented. Carbon quantum dots (CQDs) were synthesized from citric acid by a pyrolysis procedure and irradiated by gamma rays at different doses (25, 50, 100 and 200 kGy). Structure, chemical composition and optical properties were investigated by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis spectrometry and photoluminescence. Structural analysis showed that CQDs have a spherical-like shape and dose-dependent average diameters and heights. Antibacterial tests showed that all irradiated dots had antibacterial activity but CQDs irradiated with dose of 100 kGy had antibacterial activity against all seven pathogen-reference bacterial strains. Gamma-ray-modified CQDs did not show any cytotoxicity toward human fetal-originated MRC-5 cells. Moreover, fluorescence microscopy showed excellent cellular uptake of CQDs irradiated with doses of 25 and 200 kGy into MRC-5 cells.
Iron oxide, in the form of magnetite (MG)-functionalized porous wollastonite (WL), was used as an adsorbent for heavy metal ions (cadmium and nickel) and oxyanions (chromate and phosphate) removal ...from water. The porous WL was synthesized from calcium carbonate and siloxane by controlled sintering process using low molecular weight submicrosized poly(methyl methacrylate) as a pore-forming agent. The precipitation of MG nanoparticles was carried out directly by a polyol-medium solvothermal method or via branched amino/carboxylic acid cross-linker by solvent/nonsolvent method producing WL/MG and WL-γ-APS/MG adsorbents, respectively. The structure/properties of MG functionalized WL was confirmed by applying FTIR, Raman, XRD, Mössbauer, and SEM analysis. Higher adsorption capacities of 73.126, 66.144, 64.168, and 63.456 mg g
for WL-γ-APS/MG in relation to WL/MG of 55.450, 52.019, 48.132, and 47.382 mg g
for Cd
, Ni
, phosphate, and chromate, respectively, were obtained using nonlinear Langmuir model fitting. Adsorption phenomena were analyzed using monolayer statistical physics model for single adsorption with one energy. Kinetic study showed exceptionally higher pseudo-second-order rate constants for WL-γ-APS/MG, e.g., 1.17-13.4 times, with respect to WL/MG indicating importance of both WL surface modification and controllable precipitation of MG on WL-γ-APS.
Multiferroic materials attracted a lot of attention in recent years because of their significant scientific interest and technological applications. The multiferroic core/shell powders have a better ...connectivity between the phases, resulting in superior dielectric and magneto electric properties. In this study, the influence of preparation condition on structure and properties of BaTiO
3
/α-Fe
2
O
3
core/shell composite materials was examined. The five samples were obtained by varying synthesis conditions, such as synthesized method (co-precipitation and sonochemical method) and pH values of solution. XRD and Raman spectroscopy analyses were performed in order to determine phase composition and structural changes within samples. Morphology modifications were examined by SEM and EDS analyses. Finally, effect of structural and microstructural changes on magnetic and electrical properties was detected and explained.
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