Plasticized poly(lactic acid) (PLA) samples with embedded Cu-doped ZnO powder functionalized with Ag nanoparticles composites were prepared by melt blending processing technique. The effect of ...ZnO:Cu/Ag nanoparticles on the properties of plasticized PLA was investigated in terms of structural (by Attenuated total reflectance - Fourier Transform Infrared - ATR-FT-IR, X-Ray Diffraction analysis - XRD) and morphological (using Scanning Electron Microscopy - SEM and Transmission Electron Microscopy - TEM examination) modifications, thermal (Differential Scanning Calorimetry - DSC), mechanical (transmittance, tensile strength), barrier antimicrobial properties and also in respect to migration of Cu, Zn an Ag nanoparticles into food simulants. It was found that the increase of nanoparticle content (from 0.5 to 1.5 wt%) of PLA formulations leads to the increase of the degree of crystallinity of PLA. The overall migration of all samples into three food simulants was below 10 mg-dm-1, accepted value according to EU Regulation No 10/1011 for plastic materials and articles intended to come into contact with food. Based on the obtained results it can conclude that the optimum composition is PLA/ZnO:Cu/Ag 0.5, this bionanocomposite offering suitable mechanical and thermal properties, good barrier properties to ultraviolet light, water vapour, oxygen and carbon dioxide, antibacterial activity and low migration amount of nanoparticles into food simulants.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
► We used different ratios of alginate and k-carrageenan to obtain composite films. ► The composite films were cross-linked in two stages with CaCl2. ► The structures of the composite films were ...analysed by FTIR, XRD, DTG, TG and SEM. ► Cross-linked composite films show mechanical and swelling properties of hydrogels. ► The 1/3 alginate/k-carrageenan films are suitable for drug delivery applications.
The purpose of this work was to prepare an alginate/k-carrageenan composite film cross-linked with CaCl2 that could be used in biomedical applications. The influence of the alginate/carrageenan ratio on the composite films properties was studied in order to establish the optimal composition of the films. Several characterization methods such as: FTIR, XRD, TG/DTG, SEM were used, and the mechanical properties and the swelling behaviour of the obtained composite films were studied.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Despite the rapid development of a wide variety of materials, zinc oxidic based compounds remain important multifunctional materials. Optimization of synthesis parameters is an essential step in ...controlling the morpho-structural properties of nanomaterials. For example, preparation of high purity ZnO without additional calcination stage as well as achieving reproducible larger batches is still a great challenge of our days. In this study we report a simple synthesis route for ZnO nanoparticles at room temperature, without any additives and without additional calcination stages using diisopropylamine (DIA) as precipitating agent. The study is focused on changing the molar ratio, the volume and the flow rate of the reactants. Depending on the pH evolution, the phase composition can be controlled to form zinc oxide, zinc hydroxide or layered zinc acetate. Pure zinc oxide phase was obtained at pH ~8 with DIA excess at least of 3 mole. The changes of the morpho-structural and optical properties of samples were investigated by X-Ray diffraction, infrared spectroscopy, scanning electron microscopy, mineralogical optic microscopy, optical and photoluminescence spectroscopy. A better understanding of the crystalline phases formation was achieved using theoretical calculation (DFT) with a good match of the results with the experimental ones. Luminescent studies showed that the emission of ZnO is in green spectral domain at ~548 nm due to V
O
→ VB transitions while the layered zinc acetate exhibits a much more complex blue emission at ~ 442 and 476 nm due to Zn
i
contributions. The luminescent mechanism was proposed, in order to explain the luminescent behavior of samples.
Graphical Abstract
The pH evolution during the precipitation affects the morphology of the samples (layered, rounded aggregates). The blue or green luminescent emission is due to the presence of interstitial zinc (Zn
i
) and oxygen vacancies (V
o
) in layered zinc acetate or ZnO structures.
Highlights
ZnO, Zn(OH)
2
and Zn
5
(OH)
8
(Ac)
2
∙4H
2
O were prepared by precipitation.
Preparative parameters were optimized for larger batches of ZnO.
The phase purity and structural parameters are affected by pH evolution.
Triangular, rounded, tetragonal bipyramid and lamellar structures were obtained.
Blue and green luminescence peaked at 442 and 550 nm is due to Zn
i
and V
o
defects.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this study we present our first attempts to obtain silicate apatite phosphors by precipitation with NaOH under microwave conditions. Y and La precursors fired at different temperatures ...(800 °C÷1400 °C) led to phosphors with hexagonal apatite structure belonging to the space group P63/m and with crystallites size up to 105 nm. The structure and chemical composition of samples were evaluated based on FTIR, XRD and ICP-OES while the morphology, surface state and porosity were revealed using SEM and BET investigations. The impact of the firing temperature on the purity phase, crystalline order degree, crystallites size and luminescent properties of the apatite phosphors are discussed. It was found that the nature of rare earth (Y3+ or La3+) same as the incorporation degree of activator (Tb3+) is responsible for the apatites green - turquoise emission. ICP-OES measurements show that the Tb3+ amount incorporated in the apatite lattice increase with firing temperature and is lower in La-phosphors compared with Y-phosphors. The 5D4–7F5 transition observed in the green spectral domain was dominant in Y- phosphors while 5D3-7F6,5,4 transitions from blue spectral region was dominant in La-phosphors. The chromatic coordinates shifts from green to turquoise with firing temperature and depends on the excitation radiation, indicating the applicative potential of these phosphors in display screens for solid-state lighting applications.
Display omitted
•First attempts to prepare Ca2RE7.88Tb0.12(SiO4)6O2 under microwave conditions.•Incorporation degree of activator (Tb3+) increase with firing temperature.•Morpho-structure, surface state and porosity depend on synthesis conditions.•Green emission was obtained for Y-phosphors and turquoise for La-phosphors.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
La
10−x
Bi
x
(SiO
4
)
6
O
3
ceramics (x = 0; 0.1; 0.15; 0.2; 0.3) were obtained from precursors prepared by gel combustion using
l
-aspartic acid as fuel. This study presents the effect of Bi
3+
...doping level and sintering temperature on the morpho-structural and electrical properties of apatites. Processes involved in the apatite formation same as crystallization temperature were examined through TGA. The XRD patterns have showed that all samples adopt the apatite structure and crystallize in the hexagonal space group P-3(147). Samples crystallite size varies between ~ 58 and ~ 118 nm depending on the Bi
3+
doping level and the sintering temperature. In order to explain the conduction in apatite, the preferential position of Bi
3+
in lattice and the occupancy factors of O5, O6 were calculated by Rietveld refinement. ICP-OES and XPS measurements give the bismuth amount accommodated in apatite lattice and its oxidation states. The morphology, homogeneity and compactness of the ceramics at different Bi doping level were examined through SEM. The relative density of the material is enhanced by the sintering temperature up to 1500 °C, reaching 91.63% for sample doped with 1.5% Bi. Through EIS investigations, the conductivities at 500 °C, for sample doped with 1.5% Bi, are: 9.22 × 10
−5
Scm
−1
(sintered at 1400 °C) and 1.02 × 10
−3
Scm
−1
(sintered at 1500 °C), respectively, values which are higher than that of un-doped apatite (6.46 × 10
−5
Scm
−1
).
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Cooling all degrees of freedom of a molecule, a cluster, or even a nanoparticle which is suspended in a vacuum, is an experimental challenge. Without suitable schemes, cold or ultracold chemical ...reactions are not feasible. Methods such as laser based preparation of very slow atoms, decelerating molecules to low velocities with electric fields or freezing molecular ions into Coulomb crystals, are generally not suitable to cool the vibrational or rotational motion of molecules. This contribution describes a new method in which a beam of slow atoms or molecules (H, He, H2, or D2) is used for cooling charged particles confined in a multi-electrode rf trap. For reaching sub-K temperatures, the fast part of a cold effusive beam is removed with a shutter before the slow remaining neutrals interact with the ion cloud. The development of a pulsed cold beam source is discussed as well as suitable methods for determining the ion temperature. A challenging application is to prepare internally cold CH5+ for spectroscopy or chemistry. New experimental results for hydrogen abstraction in collisions with slow H atoms are reported at energies of a few meV. For evaluating these measurements and for predicting effective rate coefficients at lower energies, the kinematic conditions of the slow neutral beam-ion trap arrangement have been analyzed in detail. The potential of cooling ions such as protonated methane or H3+ with slow energy selected H atoms is briefly mentioned. An interesting process is the formation of weakly bound ions such as H4+ or CH6+ via radiative or ternary association. Such ions are ideal candidates for preparing the corresponding collision complexes very close (microeV) to the dissociation continuum using infrared transitions.
Introduction
Synthesis of nanostructured materials with well-controlled morphology and large specific surface area is essential in adsorption and catalysis for environmental depollution applications.
...Methods and objectives
In the present work, several varieties of high porous zinc indium sulfide (ZnIn
2
S
4
) were prepared using microwave-assisted and oil bath precipitation. The role of synthesis temperature and zinc concentration on the morpho-structure, porosity, and optical properties of ZnIn
2
S
4
was investigated.
Results
Hexagonal ZnIn
2
S
4
phase was formed at 180°C while disordered cubic ZnS-In
2
S
3
phase was identified at 160°C. Based on ICP-OES measurements, it was found that all samples contain lower amounts of zinc than theoretically expected leading to non-stoichiometric compounds. The specific surface area increases from 88.4 to 425.6 m
2
/g with temperature and zinc amount, values that are higher than those reported in literature. The morphology of ZnIn
2
S
4
is changing from agglomerated rounded nanoparticles to micro-flower, nano-petals, or hollow microspheres depending on the synthesis conditions. A growth mechanism was also proposed for all the nanostructures with different morphologies. The band gap of ZnIn
2
S
4
decreases from 3.61 to 2.81 eV due to morpho-structural and porosity changes. The blue-green luminescence was attributed to different defect sites in ZnIn
2
S
4
structures. Adsorption investigations of the methyl orange were carried out and discussed.
Conclusion
Oil - bath samples present a higher adsorption ability than micro-wave samples due to structural and morphology differences.
Graphical abstract
Silicates with apatite structure have become one of the most promising candidates for solid-state lighting applications. Herein we report the synthesis of pure apatite Ca
2
Y
7.76
Ce
0.12
Tb
0.12
...(SiO
4
)
6
O
2
phosphors with enhanced luminescence via a simple precipitation method. The aim of this study is to optimize the precipitation reaction through pH control and TEOS amount. In this respect, different types of precursors were prepared by precipitation between yttrium–calcium–cerium–terbium nitrates and NaOH at various pH. The extremely complex decomposition processes of precursors are discussed based on thermogravimetric analysis. The structure, morphology, surface state and porosity of both precursors and phosphors were investigated based on FTIR, XRD, SEM and BET. It was found that the crystallinity degree of the precursors decreases from 36% to 5% with the increase of pH from 7 to 11. After the thermal treatment, the phosphors become pore-less and well crystallized with crystallite sizes up to 106 nm. The phase composition of the phosphors strongly depends on the pH during the precipitation. Synthesis performed with 40% excess of TEOS at pH 11 led to phosphors with pure apatite structure and enhanced luminescence. Under excitation with 365 nm the apatite phosphors exhibits a broad emission band in the range of 350–480 nm, due to transitions in Ce
3+
and narrow lines in range of 480–650 nm specific for transitions in Tb
3+
.
Highlights
Gel precursors are prepared by precipitation at different pH for synthesis of apatite phosphors.
pH affects the morpho-structure and surface state of both precursors and phosphors.
Pure apatite with crystallites size of 66.5 nm was obtained at pH 11.
Effect of pH on Ce
3+
and Tb
3+
emission intensities was discussed in detail.
Apatites show blue, white-turquoise or greenish colour depending on excitation.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Aim
This study aimed at unprecedented physical and chemical evaluation of the ‘green plastics’ polyhydroxyalkanoates (PHAs), in an extremely halotolerant Halomonas elongata strain 2FF under high‐salt ...concentration.
Methods and Results
The investigated bacterial strain was isolated from the surface water of the hypersaline Fără Fund Lake. The 16S rRNA gene sequence phylogeny and phenotypic analysis indicated that the isolate belonged to H. elongata. PHA inclusions were observed by Sudan Black B, Nile Red staining, and transmission electron microscopy during growth at high salinity (10%, w/v, NaCl) on 1% (w/v) d‐glucose. The produced polymer was quantitatively and qualitatively assessed using crotonic acid assay, elemental analysis, Fourier transform infrared and Raman spectroscopies. Additionally, X‐ray powder diffraction, 1H‐NMR spectroscopy, and differential scanning calorimetry were applied. The investigations showed that the intracellular polymer was polyhydroxybutyrate (PHB) of which the strain produced up to 40 wt% of total cell dry weight after 48 h. The analysis of phaC gene from the isolated H. elongata strain indicated that the encoded PHA synthase belongs to Class I PHA synthase family.
Conclusions
Overall, our investigations pointed out that the halotolerant H. elongata strain 2FF was capable to produce significant amounts of PHB from d‐glucose, and PHAs from various carbon substrates at high‐salt concentrations.
Significance and Impact of the Study
The tested strain showed the ability for significant production of natural, biodegradable polymers under nutrient limitation and hypersaline conditions suggesting its potentiality for further metabolic and molecular investigations towards enhanced biopolymer production. Additionally, this study reports on the unprecedented use of Raman and XPRD techniques to investigate PHAs of an extremely halotolerant bacterium, thus expanding the repertoire of physical methods to study green plastics derived from extremophilic microorganisms.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Inorganic luminescent materials comprise a wide range of compounds showing a large area of applications in sensing, imaging, drug delivery or optical-electrical displays. In this study, various ...luminescent zinc hydroxy-carbonate compounds were prepared by precipitation using different precipitating agents such as LiOH, NH
3
, Na
2
CO
3
and (NH
4
)
2
CO
3
. The morpho-structure and optical properties of samples are investigated by X-Ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), adsorption and porosity measurements (BET), optical (UV–Vis) and photoluminescence (PL) spectroscopy. The phase composition, morphology and porosity of zinc hydroxide (ZH) and zinc hydroxy-carbonates (ZHC) strongly depends on the evolution of pH and availability of different ionic species during the precipitation. The spherical particles of zinc hydroxy-carbonate compounds with sizes ranging between 5 and 20 nm, exhibits strong tendency to form layered or spongy aggregates. BET investigations show that the porosity is distributed either at the surface (ZH) or in the depth of the particles (ZHC) and the specific surface area of samples varies between 15 m
2
/g. and 55 m
2
/g. The effect of various amounts of Cu
2+
on optical properties of samples is also discussed. Luminescent studies confirm that interaction with Cu
2+
leads first to enhancement and then to quenching of the purple–blue emission of samples while, the energy band gap decreases due to the apparition of new acceptor–donor levels in the optical band gap. A mechanism is proposed to explain the luminescent behavior of the samples.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
