A DFT study of inclusion complexes of the antituberculosis drugs pyrazinamide and isoniazid with cucurbit[7]uril

A photoactive system, (2E)-3-{3-[(Z)-naphthalen-1-yldiazenyl] phenyl} prop-2-enoic acid, was synthesized and incorporated on to beta-cyclodextrin (β-CD) core through esterification of the hydroxyl groups of β-CD with the free carboxyl moiety of the chromophoric system by DCC coupling. The silver nanoparticle was synthesized by the reduction reaction executed on silver acetate in presence of dodecyl amine. The silver nano particles were dispersed in β-CD aggregates modified with photoactive system by phase transfer mechanism. The products were characterized by elemental analysis, melting point determination, UV–visible, FT-IR and NMR (¹H and ¹³C) spectral methods and SEM and TGA-DTG thermal studies. The thermal studies shows that the silver nanoparticle dispersed functionally modified beta cyclodextrin exhibited enhanced thermal stability compared to the functionalised β-CD.     

On the coefficient inverse problem of heat conduction in a degenerating domain

ABSTRACT

In the paper, we consider a coefficient inverse problem for the heat equation in a degenerating angular domain. It has been shown that the inverse problem for the homogeneous heat equation with homogeneous boundary conditions has a nontrivial solution up to a constant factor consistent with the integral condition. Moreover, the solution of the considered inverse problem is found in explicit form. In conclusion, statements of possible generalizations and the results of numerical calculations are given.     

Thermal oxidation effect on structural and optical properties of?heavily doped phosphorus polycrystalline silicon films

The study reported in this paper contributes to better understanding the thermal oxidation effect on structural and optical properties of polycrystalline silicon heavily in situ P-LPCVD films. The deposits, doped at levels 3×10¹⁹ and 1.6×10²⁰ cm⁻³, have been elaborated from silane decomposition (400 mTorrs, 605°C) on monosilicon substrate oriented 〈111〉. The thermal oxidation was performed at temperatures: 850°C during 1 hour, 1000, 1050, and 1100°C during 15 minutes. The XRD spectra analysis pointed out significant 〈111〉 texture evolution, while in the case of 〈220〉 and 〈311〉 textures, the intensities are practically invariant (variations fall in the uncertainty intervals). The optical characterizations showed that refractive index and absorption coefficient are very sensitive to the oxidation treatment, mainly when the doping level is not very high. We think that atomic oxygen acts as defects passivating agent leading to carriers’ concentration increasing. Besides, the optical behavior is modeled in visible and near infrared, by a seven-term polynomial function n ²=f(λ ²), with alternate signs, instead of theoretically unlimited terms number from Drude’s model. It has been shown that fitting parameters fall on Gaussian curves like they do in the theoretical model.     

Effective hydrogenation and surface damage induced by MW-ECR plasma of fine-grained polycrystalline silicon

This work reports the investigations on the effects of the hydrogenation process of thin film polycrystalline n⁺pp⁺ mesa silicon cells using MW-ECR plasma in a conventional PECVD system. Different operating parameters such as MW-ECR power, annealing temperature and the doping level of the emitter region were varied. The n⁺-type emitter regions were obtained by phosphorus diffusion in a conventional furnace using an oxide doping source containing phosphorus (P507 or P509 solutions, from Filmtronics Inc.). The MW hydrogenation was carried out at a sample temperature of 400°C for 60 min. Both types of emitters formed from P507 and P509 showed V _oc of 155 mV and 206 mV, which increased linearly to 305 mV and 331 mV, respectively, after hydrogenation when the MW power varied from 200 to 650 W. However, the sheet resistances of the n⁺ emitter region showed a slight increase depending upon hydrogenation power because of its etching. In a further study, hydrogenated samples were annealed in neutral or forming gas (FG) and we observed interesting results on V _oc in the presence of FG. The FG annealing temperature study revealed a strong dependence of V _oc on MW power, which affected the etching level of emitter and emitter dopant concentration, which controls the diffusion of hydrogen ions during post-hydrogenation step. The results were explained in detail by combining the effects of MW power and dopant level of the emitter.     

Inclusion complexes of ortho-anisidine and β-cyclodextrin: A quantum mechanical calculation

The structural aspects for the complexation of ortho-anisidine (O-AN)/β-cyclodextrin were explored by using PM6, density function theory B3LYP/6-31G*, M05-2X/6-31G*, B3PW91/6-31G*, MPW1PW91/6-31G*, HF/6-31G* methods and several combinations of ONIOM2 hybrid calculations. Calculations were performed upon the inclusion complexation of β-cyclodextrin (β-CD) with neutral (O-AN1) and cationic (O-AN2) species of ortho-anisidine. The obtained results with PM6 method clearly indicate that the formed complexes are energetically favored, the complex of O-AN2/β-CD in B orientation is significantly more favorable than the others energetically. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify the donor–acceptor interactions between ortho-anisidine and β-CD.     

Theoretical investigation study based on PM3MM and ONIOM2 calculations of β-Cyclodextrin complexes with diphenylamine

The inclusion complex of β-cyclodextrin (β-CD) and diphenylamine (DPA) was investigated by using PM3MM, DFT, HF and ONIOM2 methods. The most stable structure was obtained at the optimum position and angle. The results indicate that the inclusion complex formed by DPA entering into the cavity of β-CD from its wide side (the secondary hydroxyl group side) is more stable than that formed by DPA entering into the cavity of β-CD from its narrow side (the primary hydroxyl group side). The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify the donor–acceptor interactions between diphenylamine and β-CD. A study of these complexes in solution was carried out using the CPCM model to examine the influence of solvation on the stability of the diphenylamine β-CD complex.     

Influence of gamma-radiation on the optical properties of modified polyvinyle chloride

Abstract

The optical absorption spectra of polyvinyle chloride, PVC, doped with Cd and Pb is presented. The effect of γ radiation doses in range of 2–200 Mrad on the fundamental absorption edge Λ_g was determined. On the basis of quantitative analysis of obtained data, the calculated absorption coefficient, α, the absorption index, K, and the optical energy gap E_opt, were found to be radiation and dopant dependent. The results are discussed on the basis of the radiation induced degradiation of PVC.