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191.
Density functional theory (DFT) studies are done to investigate structural and electronic properties of (5,5) chirality single walls boron nitride nanotubes (BNNTs) in the armchair model interacting with metformin (MF) on the surface and ends. Our calculations consider the exchange-correlation energies with the Hamprecht–Cohen–Tozer–Handy functional within the generalized gradient approximation (HCTH-GGA) and the double polarized DNP base function. The geometry optimization follows the minimum energy criterion for all six geometries we have considered. Results show that the MF is adsorbed through the groups NH2–NH at one end of the nanotube. The system polarity is increased which indicates the possible dispersion and solubility. Moreover the interaction between these species induces an increase in the chemical reactivity of the order of 0.42 eV. Meanwhile the solvation in water keeps the semiconductor characteristics of both nanotube and MF. The work function of the BNNT-MF is drastically reduced respect to the pristine system when the BN nanotube is doped at its surface and ends with carbon. This means that the functionalized BN nanotube facilitates conditions to improve field emission. 相似文献
192.
Liping Liao Bing Wu Dr. Evgeniya Kovalska Dr. Vlastimil Mazánek Dr. Martin Veselý Ivo Marek Lucie Spejchalová Prof. Dr. Zdeněk Sofer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13235-13241
The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li+-, Na+-, and K+-based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb2CTx electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li2SO4, Na2SO4, and K2SO4 electrolytes with d-spacing. Additionally, our results showed that the Nb2CTx electrode exhibited higher electrochemical performance in the presence of Li2SO4 than in that of Na2SO4 and K2SO4. This is partly because the smaller-sized Li+ transports quickly and intercalates between the layers of Nb2CTx easily. Poor ion transport in the Na2SO4 electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li+>Na+>K+. Our experimental studies provide direct evidence for the intercalation mechanism of Li+, Na+, and K+ on the 2D layered Nb2CTx electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes. 相似文献
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J. Oueslati A. Rayes C. Ben Nasr F. Lefebvre 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):693-705
The synthesis and structures of two new compounds with the general formula N(C2H4NH3)3(H2TO4)(HTO4)·2H2O (T = P, As) are reported. They crystallize with triclinic unit cells and are isotropic. We determined the structure of phosphate salt. The following unit cell parameters were found: a = 9.886(4), b = 9.308(2), c = 10.140(3) Å, α = 109.38(2), β = 108.83(3), γ = 74.40(3)°, V = 819.2(5) Å3, and ρcal. = 1.537 g · cm?3. The crystal structure was solved with a final R = 0.042 for 3748 with I > 3σ I). The space group is P-1 and Z = 2. The atomic arrangement can be described as a three-dimensional network of hydrogen bonds made up from HnPO4 3?n (n = 1, 2) anions and H 2 O molecules between which are trapped the tris(2-ammoniumethyl)amine cations. Solid-state 13C and 31P MAS-NMR spectroscopies are in agreement with X-ray structure. Ab initio calculations allow the attribution of the phosphorus signals to the independent crystallographic sites. 相似文献
198.
Sutanjay Saxena 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):387-393
The dynamic release of drug propranolol HCl from the propranolol HCl–resin complex (PRC) loaded calcium alginate beads has been studied in the buffer media of pH 1.2 at the physiological temperature 37°C. The PRC encapsulated beads demonstrated nearly 58.04% release while naked PRC particles released 98.00% drug in 24 h in the gastric fluid. The amount of drug released was found to increase with and decrease in the amount of sodium alginate in the beads. Similarly, with the increase in the amount of entrapped PRC particles within the beads, the quantity of drug released was also observed to increase. The degree of crosslinking of beads also affected the release kinetics. Interestingly, the release from naked PRC particles followed ‘first‐order’ kinetics while PRC particles, entrapped in calcium–alginate beads, exhibited ‘diffusion controlled’ release behavior as indicated by liner nature of fractional release vs. √t plot. 相似文献
199.
Yvon Pointud Anne-Gaelle Valade Christelle Pointon Georges Jeminet Jose-Luis Beltran 《Supramolecular chemistry》2013,25(4):261-269
The binding abilities of a new class of 14-membered ring ligands bearing diketal dilactam functions were explored by UV-visible spectrophotometry. Their formation constants, determined in THF solution, showed appreciable complexation with divalent cations (stability order: Sr2+≥Ca2+>Zn2+≥Mg2+>Ba2+) whereas no association was observed with monovalent cations. The stoichiometry of the complexes formed was essentially 1:1 although sometimes a low percentage (<10%) of 1:2 (cation–ligand) species was detected. The corresponding formation constants determined by computation (STAR program) were in the range 1.5<log?β 11<4.8 and 4.4<log?β 12<7.1. They depend significantly on the nature of the substituents. In addition, solvent extractions carried out in a water–chloroform system showed the highest constants (log K ex) for the most substituted macrocycles 7b and 7c (norephedrine series) with a lipophilic skeleton. 相似文献
200.
o-Dihyroxy-3-phenylchromenone derivatives, namely, 6,7-dihydroxy-3-(3′,4′-dimethoxyphenyl)chromenone and 6,7-dimethoxy-3-(3′,4′-dihydroxyphenyl)chromenone, were obtained from 2,4,5-trihydroxybenzaldehyde/3,4-dimethoxyphenylacetic acid and 2-hydroxy-4,5-dimethoxybenzaldehyde/3,4-dihydroxyphenylacetic acid, respectively, in the presence of acetic anhydride and sodium acetate under an inert atmosphere, after treatment with MeOH/HCl(aq). The chromenone-crown ethers were prepared from cyclic condensation of o-dihydroxy-3-phenylchromenones with poly(ethylene glycol) ditosylates in the presence of CH3CN/alkali metal carbonates. The chromatographically purified novel chromenone-crown ethers were identified by 1H NMR, MALDI-TOF mass spectrometry and elemental analysis. The fluorescence and UV–vis spectroscopic properties of the obtained chromenone-crown ethers and their complexes with Li+, Na+ and K+ perchlorate salts were estimated in acetonitrile. The quantum yields of novel chromenone-crown ethers were determined by the comparative method. 相似文献