The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon ...surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400-650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti(4+) to Ti(3+). The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.
A novel series of Cu(II) complexes with formula M(HL
n
)(ClO
4
)
2
·mH
2
O HL
n
: 13-membered pentaazamacrocyclic ligand resulted from condensation of
N
,
N
′-bis(2-aminoethyl)ethane-1,2-diamine,
l
...-tyrosine (HL
1
)/
l
-tryptophan (HL
2
)/
l
-phenylalanine (HL
3
) and formaldehyde were synthesized by one-pot method. Techniques such as ESI–MS, IR, UV–Vis and EPR spectroscopy provided data characterizing the complexes as mononuclear species. The course of thermal decomposition was followed using TG/DSC–MS analysis in air atmosphere. The TG curves showed a gradual decomposition in several stages that comprise dehydration, decomposition of perchlorate ions as well as fragmentation and oxidative degradation of the organic part. The intermediates formed after first stage of water elimination are stable on 40, 15 and 80 °C interval for complexes (
1
), (
2
) and (
3
), respectively. The compounds were tested on the eukaryotic unicellular organism
Saccharomyces cerevisiae
, showing variable actions in terms of toxicity, cellular uptake and capacity to alleviate growth defects associated with Cu, Zn-superoxide dismutase (SOD1) depletion.
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•Nanofibers with loaded ionic liquid were successfully produced.•Rised IL content reduce viscosity and increase conductivity electrospinning solution.•PEO-IL nanofibers' average ...diameter decreased with the increased IL content.•Thicker nanofibers were obtained with a higher molecular weight polymer.•Abcence of hydrogen bonds between ILs and PEO in electrospun nanofibers.
Keeping up with cutting edge research in the field of drug delivery, the overall goal of this study was to develop innovative electrospun nanofibers loaded with ionic liquids (ILs) as active pharmaceutical ingredients (APIs). For the first time, a novel approach was examined by combining biocompatible polymer, poly (ethylene oxide) (PEO), and pharmaceutical ILs in an electrospinning process to develop nanofibers with high drug loading (up to 47%). Firstly, two well-known local anaesthetic drugs, lidocaine and procaine, were modified into ILs with the salicylate, forming lidocaine salicylate and procaine salicylate. Its dual-functional nature and increased water solubility for 4- to 10-fold depending on the drug used contribute to overcoming current hurdles encountered by APIs such as poor solubility, low bioavailability, and polymorphism of the solid-state. Nanofibers were formulated using solutions tested for density, viscosity, electrical conductivity, and small-angle X-ray scattering by varying PEO molecular weight and the PEO to IL mass ratio. Scanning electron microscopy showed the surface morphology of the obtained nanofibers, while Fourier transform infrared spectroscopy and differential scanning calorimetry confirmed IL in the nanofibers in an amorphous state. Thus, nanofibers with incorporated IL represent well-known drugs in the new form and a novel dermal application delivery system.
The inkjet printing of the functional materials prepared by the sol-gel route is gaining the attention for the production of the variety of the applications not limited to the printed boards, ...displays, smart labels, smart packaging, sensors and solar cells. However, due to the gelation process associated with the changes from Newtonian to non-Newtonian fluid the inkjet printing of the sol-gel inks is extremely complex. In this study we reveal in-depth rheological characterization of the WO3 sols in which we simulate the conditions of the inkjet printing process at different temperature of the cartridge (20–60 °C) by analyzing the structural and rheological changes taking place during the gelation of the tungsten oxide (WO3) ink. The results provide the information on the stability of the sol and a better insight on the effects of the temperature on the gelation time. Moreover, the information on the temperature and the time window at which the inkjet printing of the sol-gel inks could be performed without clogging were obtained. The WO3 ink was stable in a beaker and exhibited Newtonian flow behavior at room temperature over 3 weeks, while the gelation time decreased exponentially with increasing temperature down to 0.55 h at 60 °C.
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•Mixtures of benzocainium ibuprofenate in menthol:decanoic acid with molar ratios of 1:2, 1:1 and 2:1 were prepared.•More pronounced solvation ability of system with an excess of ...decanoic acid (Men:DecA/1:2) than the other systems.•System with excess decanoic acid leaves the possibility that its excess makes interactions with the ionic liquid.•The presence of benzocainium ibuprofenate increases structural organization in all three NADES systems.
In this work, the mixture of the active pharmaceutical ingredient ionic liquid (API-IL) benzocainium ibuprofenate and natural deep eutectic solvents (NADESs) of menthol:decanoic acid with the molar ratios 1:2, 1:1 and 2:1 were prepared, and nature of interactions in these systems was investigated for the first time. These systems of hydrophobic API-IL-NADES are mixtures that are compatible and offer an opportunity for the topical application of ionic liquids, which are in a liquid state above room temperature and do not dissolve in water well. Ionic liquid and NADESs with different molar ratios were synthesized and characterized using infrared and nuclear magnetic resonance spectroscopy and differential scanning calorimetry. The densities, speeds of sound, and viscosities of the studied mixtures were measured in the temperature range from T = (293.15 to 318.15) K at different API-IL molalities. From obtained thermodynamic properties, it was discussed how the mole fraction of the NADES components influences the molecular and solvent performance.
A new co-crystal with the formula Ni(bpy)(acr)2(H2O)·MA (bpy = 2,2′-bipyridine, acr = acrylate and MA = melamine) has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis ...and single crystal X-ray diffraction. The complex contains discrete unities of Ni(bpy)(acr)2(H2O) and melamine linked in a complex network by both hydrogen bonds and π-π stacking interactions. Structural characterization revealed that Ni(II) adopts an octahedral distorted stereochemistry, and acrylate ions present both unidentate and chelate coordination modes. Thermal decomposition occurs in four steps, the ligands being stepwise released in the order of water, acrylate, bipyridine and melamine. The antimicrobial activity of the obtained complex, its precursor (Ni(bpy)(acr)2(H2O)) and melamine were assessed against planktonic (minimal inhibitory concentration—MIC) and biofilm-embedded (minimal biofilm eradication concentration—MBEC) Gram-positive and Gram-negative bacterial strains. The obtained results revealed that the new complex and its precursor exhibited a superior activity compared to MA, the highest susceptibility being recorded for the Staphylococcus aureus strain. The MIC and MBEC ranges were very similar, indicating the potential of this complex and its precursor to develop novel anti-biofilm agents.
The influence of 4 different anions on hydrogen bonding interactions and energetic properties Cd picolinamide complexes have been studied. Bulky, tetrahedral anions inhibit the formation of strong ...head-to-head amide interaction and azide anion promotes the formation of insensitive energetic coordination polymer.
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A novel group of energetic compounds, known as energetic coordination polymers (ECPs), can be rationally designed by introducing of highly energetic ions like ClO4-, N3–, NO3– and NO2– into a polymeric framework. Herein we report the preparation of four novel cadmium(II) complexes with picolinamide (pia) as ligand and different ions: Cd(pia)3(ClO4)2·2H2O (1), Cd(NO3)(ac)(pia)2 (2), Cd(NO2)2(pia)2 (3), Cd2(μ1,1-N3)4(pia)2n Cd(μ1,1-N3)2(pia)n (4). The presence of different anions from starting Cd(II) salts caused the formation of discrete coordination compounds(1, 2 and 3), and coordination polymer (4). In 2, 3 and 4 anions are coordinated to Cd(II), while in 1 perchlorate anions act as a counterion. The molecular and crystal structure analysis has shown that in all compounds pia acts as N,O-chelator in various coordination arrangements depending on the present anion (1, 2 and 4 - distorted octahedral, 3- distorted square antiprismatic). In the crystal structures, the dominant mode of intermolecular interaction is a strong head−to−head amide hydrogen bond, with exception of 1. Structural analysis of herein-reported compounds and previously described Cd(pia)A (A – anion) compounds has shown that bulky tetrahedral anions (ClO4- and SO42-) inhibit the formation of the strong head−to−head amide hydrogen bonds. The investigations of energetic properties and sensitivity indicate a possible application of compound 4 as a secondary explosive material with energetic properties like those of LA (lead azide), mercury fulminate, or ammonium nitrate.
Curing kinetics study of melamine–urea–formaldehyde resin Likozar, Blaž; Korošec, Romana Cerc; Poljanšek, Ida ...
Journal of thermal analysis and calorimetry,
09/2012, Letnik:
109, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
The influence of the preconditioning at different temperatures on the cure kinetics of melamine–urea–formaldehyde resins coated on stone wool was investigated under acidic conditions using ...differential scanning calorimetry and thermogravimetry. The higher pre-treatment temperature was applied, to which resin-coated stone wool was exposed, the lower was the mass loss during the experiment. Kinetic model parameters were determined in two different manners, with the parameters being independent of preconditioning temperature and dependent on the latter. The apparent orders of reaction were approximately two (all of them being within the range 0.96–2.33), which would imply that cross-linking predominantly proceeds via the bimolecular reaction of either melamine or urea and formaldehyde. Nonetheless, the apparent orders of reaction decreased as a function of preconditioning temperature. The apparent activation energies varied less with preconditioning temperature, assuming values between 64.2 and 78.5 kJ mol
−1
. The applicability of
n
th-order reaction kinetic models was consequently validated for two other dynamic thermal regimes.
A new derivative 5-phenyl-7-methyl-1,2,4-triazolo1,5-
a
pyrimidine (pmtp) was synthesised by 1 + 1 condensation of benzoylacetone and 3-amino-4H-1,2,4-triazole. Single crystal X-ray diffraction ...revealed that the pmtp crystallises in monoclinic system, P21/n spatial group. In order to modulate the biological activity, new species M(pmtp)Cl
2
·nH
2
O (M: Co,
n
= 2; M: Ni,
n
= 3; M: Cu,
n
= 1; M: Zn,
n
= 0) were synthesised by one-pot method. Chemical analysis, molar conductivities, IR, UV–Vis-NIR and EPR spectroscopy, as well as magnetic data recorded at room temperature provided useful information concerning the molecular formula, stereochemistry and ligand coordination mode. The modifications at heating and also the thermodynamic effects that accompany them were investigated by thermal analysis. The nature of the gaseous products formed in each step was evidenced by simultaneous TG/DSC/EGA measurements. Processes as water and chloride elimination, fragmentation and oxidative degradation of the triazolopyrimidine derivative were observed during the thermal studies. The final residue was the most stable metallic oxide as X-ray powder diffraction indicates. Zinc (II) and copper (II) complexes exhibited the most significant antimicrobial activity against a wide spectrum of Gram-positive and Gram-negative bacterial strains, both reference and clinical resistant ones, in planktonic and biofilm state. The minimal biofilm eradication values were two to four times lower than the minimal inhibitory concentrations demonstrating the potential of the obtained complexes to act as anti-pathogenic agents.
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► The acidic treatment considerably shortened the α-MnO2 nanorods. ► α-MnO2 nanorods with higher potassium contents undergo to the structural changes at higher temperatures. ► Up to ...500°C no structural and morpholigcal changes are observed.
The effect of heat treatment on the structure and morphology of α-MnO2 nanorods with different potassium contents was investigated. These nanorods, prepared by ion exchange, were thermally treated at 500, 800, 1000 and 1100°C, and characterized with X-ray diffraction and electron microscopy. The structure and morphology of the starting sample remained preserved up to 500°C. The first structural and morphological changes were observed when α-MnO2 nanorods with different potassium contents were heated at 800°C. The sample with the highest potassium content decomposed only partially to α-Mn2O3, while the decomposition of the α-MnO2 to α-Mn2O3 was complete in the sample with the lowest potassium content. Morphologically, both samples were composed of nanorods and grains. When the temperature was increased to 1000 and 1100°C, both the structure and morphology changed: the α-MnO2 nanorods completely decomposed to Mn3O4 grains. The acidic media in which the ion exchange took place shortened the α-MnO2 nanorods.
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