thermogravimetric studies
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Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1215
Author(s):  
Catalina Ionica Ciobanu ◽  
Iulian Berladean ◽  
Elena-Luiza Epure ◽  
Aurel Simion ◽  
Gabriela Lisa ◽  
...  

Bent-core liquid crystals (BCLC) have been widely studied as a result of their unusual polar and chiral properties. Similar to calamitic and discotic molecules, BCLC molecules also exhibit nematic phases, besides other higher order mesophases. The aim of this work is to comparatively analyze the mesomorphic behavior of some bent-core 1,3-disubstituted benzene core compounds derived from resorcinol and isophthalic acid. Thus, the two classes of compounds differ in the nature of the orientation of the ester bond between the benzene central core and the two branches attached to the core. The mesomorphic behavior was elucidated by polarized light optical microscopy and differential calorimetry. Given the relatively high isotropic points of the compounds, confirmation of the thermal stability in the domains manifesting liquid crystalline properties was performed by thermogravimetric studies. The theoretical explanation of the difference in mesomorphic behavior for the two classes was based on molecular modeling studies.


2021 ◽  
pp. 1-10
Author(s):  
Ellen Hieckmann ◽  
Kaitlin K. K. Kammerlander ◽  
Lydia Köhler ◽  
Laura Neumann ◽  
Stefan Saager ◽  
...  

Algae like diatoms are widely studied as a means to remediate anthropogenically contaminated sites. In the present study, CL (cathodoluminescence) and EDX (energy-dispersive X-ray) spectroscopy in an SEM (scanning electron microscope) were optimized for the detection of Eu(III) sorbed on diatom biosilica. The required stability of biosilica under a focused electron beam was extensively investigated. Using experimentally determined data of thermal properties, the temperature increase within biosilica exposed to an electron beam was simulated by finite element calculations based on results from Monte Carlo simulations of electron scattering. Complementary thermogravimetric studies substantiated a chemical stability of biosilica in a wide temperature range, confirming its suitability for long-lasting SEM investigations. In subsequent EDX measurements, characteristic Eu lines were detected. Eu was found to preferentially accumulate and aggregate on silica fragments. CL spectra were obtained for the Eu(III) reference material, EuCl3. For Eu-loaded biosilica, even parts without detectable Eu signal in the EDX spectra show significant Eu(III) signals in the CL spectra. This highlights the sensitivity of CL in studying f-element sorption. CL data showed that Eu(III) was distributed on the entire surface. In conclusion, this work demonstrates the merit of CL and EDX methods for sorption studies on biogenic materials.


2021 ◽  
Vol 29 ◽  
pp. 191-195
Author(s):  
E. N. Shamilov ◽  
A. S. Abdullaev ◽  
V. E. Shamilli ◽  
T.Y. Asgerova ◽  
Sh. I. Gahramanova ◽  
...  

Aim. The synthesized and characterized of the complex nickel (II) with tryptophan [NiL2 (H2O)2]; L = Trp. It is shown that the composition of the complex obtained depends on the ratio of the initial components. Methods. The composition and structure of the complex were studied by elemental, TG/DrTG-DTA analysis and IR spectroscopy. The method of IR showed that the ligand in the composition of the metal complex enter the neutral form and coordinate with the complexing agent through the nitrogen atom. Results. The results of thermogravimetric studies have shown that the final product of the thermal decomposition of all compound is metal oxide, respectively. Conclusions. Have been studied the biological properties – the toxicity has been evaluated, the influence of the complex on the resistance to hypoxia and ant radiation activity has been determined. Keywords: tryptophan, nickel, tryptophan-metal complexes, amine groups, IR spectroscopy, thermogravimetry, toxicity, antiradiation activity.


2021 ◽  
Vol 12 (3) ◽  
pp. 3647-3663

A durable and environmentally friendly flame-retardant treatment process on wool via graft co-polymerization of vinyl phosphonic acid (VPA) was investigated. The influence of temperature, time, VPA, and catalyst on the grafting yield (GY) was studied. Employing response surface methodology, the grafting parameters were optimized, and the highest GY was achieved. Thermogravimetric studies showed a 3.86% increase in the remaining char ratio at 750°C for the wool fabric after graft co-polymerization of VPA. Flame retardancy of wool fabrics was evaluated with respect to their limiting oxygen indices (LOI) and the ease of ignition measurements. The sample with 8.1% GY exhibited a 35.89% increase in LOI and over a 3.66-fold increase in ignition time. The chemical structure of the grafted wool is proposed according to FTIR and 31P Solid-state MAS NMR evidence. The presented flame-retardant finish process was deemed to be a green and durable substitute for the conventional, semi-durable, and non-environmentally friendly processes.


Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 611
Author(s):  
Ekaterina Orlova ◽  
Elena Kharitonova ◽  
Timofei Sorokin ◽  
Alexander Antipin ◽  
Nataliya Novikova ◽  
...  

The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. Presumably, the high-temperature phase I41/acd of Nd2MoO6 single crystals is retained at room temperature. The reason for the loss of the center of symmetry in the structures of La2MoO6 and Pr2MoO6 and the transition to the space group I4¯c2 is the displacement of oxygen atoms along the twofold diagonal axes. In all structures, Mg cations are localized near the positions of the Mo atoms, and the splitting of the positions of the atoms of rare-earth elements is found. Thermogravimetric studies, as well as infrared spectroscopy data for hydrated samples of Ln2MoO6 (Ln = La, Pr, Nd), pure and with an impurity of Mg, confirm their hygroscopic properties.


Author(s):  
B. S. Burlaka

Interleukin-1 receptor antagonist (IL-1Ra) is an active pharmaceutical ingredient obtained by the method of gene transformation of Escherichia coli, provides a neuroprotective effect, namely – inhibition of oxidative modification of proteins, normalization of functional activity of mitochondrial energy, mitochondrial energy. Early complex physical-chemical, microbiological, and biopharmaceutical studies have developed a new intranasal formulation, the formulation of which contains: IL-1Ra, sodium carboxymethyl cellulose, D-panthenol, benzalkonium chloride, trilon B, Tween-80, phosphate buffer solution. Given the peculiarities of the technological process, when creating a new gel dosage form, it is necessary to justify the temperature of the carrier base, the introduction of the active substance into the base, as well as to predict the possible chemical interaction of individual components in the dosage form. Therefore, the application of thermogravimetric analysis in pharmaceutical technology is relevant. The aim of the work is to conduct thermogravimetric studies of a new nasal form with an antagonist of interleukin-1β (IL-1Ra). Materials and methods. The objects of thermogravimetric studies were: semi-finished product-solution of the receptor antagonist of interleukin-1 (IL-1Ra). Excipients were: sodium carboxymethylcellulose, tween-80, D-panthenol, trilon B, benzalkonium chloride. To ensure the appropriate pH value used phosphate buffer solution (pH 6.0), according to the recipe to State Pharmacopoeia 2 ed. In addition to the individual components of the finished nasal gel, also prepared nasal gel without IL-1Ra, as well as gel with IL-1Ra. The thermographic analysis was performed on a derivatograph – Shimadzu DTG-60 (Japan) with a platinum-platinum-rhodium thermocouple when heating the samples in aluminum crucibles (from 15 °C to 250 °C). Al2O3 was used as a reference substance. The heating rate was 10 °C per minute. The weight of the test samples ranged from 19.22 mg to 52.91 mg. The derivatograph graphically recorded the obtained data in the form of curves T, DTA, TGA. The T curve on the derivatogram shows the change in temperature, and the TGA curve shows the change in mass of the sample during the study period. The DTA curve reflects the differentiation of thermal effects, contains information about endothermic and exothermic maxima, can be used for qualitative evaluation of the derivatogram. Results. The study consisted of two stages. At the first stage, we studied the derivatograms of experimental samples – individual ingredients of the finished nasal gel - active and excipients, namely: IL-1Ra, sodium carboxymethylcellulose, tween-80, D-panthenol, trilon B, benzalkonium chloride, phosphate buffer solution 6.0. In the second stage, samples of nasal gels were prepared: nasal gel with the required amount of excipients, in addition to the active substance – IL-1Ra, as well as a nasal gel containing IL-1Ra and the required amount of excipients. As a result, we obtained some parameters of thermogravimetric analysis in the form of a graphical image – derivatograms, which were then analyzed. Conclusions. Thermogravimetric studies of individual components of nasal gel with IL-1Ra, as well as nasal gels with active substance and without active substance, were found that the manufacturing process of gel with IL-1Ra should be carried out taking into account thermolabile compounds. First, you need to prepare the base without preservative and IL-1Ra. Then at a temperature not exceeding 40 °C dissolve the preservative, and then when cooled to 20 °C add IL-1Ra. It was found that the developed dosage form of the gel with IL-1Ra is a mixture of active and excipients, the ingredients of which do not interact with each other and can be combined in one dosage form.


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