Structure Analysis for Hydrate Models of Ethyleneimine Oligomer by Quantum Chemical Calculation

Structure analyses for hydrate models of ethyleneimine oligomer (5-mer as model of PEI) were investigated by quantum chemical calculations. Conformation energies and structures optimized for hydrate models of (ttt)5 and (tgt)5 conformers were examined. Hydrate ratio, h [h = H2O/N (mol)], was set from 0.5 to 2. In anhydrates, (tg+t)5 conformer was more stable (?1.8 kcal/m.u.) than (ttt)5. In hydrates, (ttt)5 conformers were more stable (?0.7 - ?4.3) than (tg+t)5. These results corresponded to experimental results that anhydrous linear PEI crystal changes from double helical to single planar chain in hydration process. Structures calculated for (ttt)5 agreed in those observed for hydrates of PEI. In all (tg+t)5 conformers, O???H bonds between waters were found with the decreases of N???H bonds between imino group and water. The O???H bonds in (tg+t)5 conformer resulted in its high chain torsion, and strongly related with instability and structure change (large swelling).

In vitro Studies on Binding and Release of Vascular Endothelial Growth Factor in Heparinized Bovine Pericardiums

Objective： To investigate binding and release of vascular endothelial growth factor （VEGF） and its effect on adhesion and proliferation of endothelial cells （ECs） in acellular fresh specimens of bovine pericardiums, which were modified by heparinization. Methods： Cross-linked aeellular fresh specimens of bovine perieardiums were heparinized by three methods： （1） heparinizcd N-（3-diinethylaminopropyl）-N＇-ethylcarbodiimide hydrochloride （EDC） treated acellular tissue samples; （2） heparinized poly（ethyleneimine） （PEI） treated acellular tissue samples; （3） heparinized EDC-PEI treated aeellular tissue samples. Controlled release of VEGF and its effect on adhesion and proliferation of ECs was evaluated. Results： In the present study, binding and release of VEGF had better performance in heparinized EDC-PEI treated group, compared with heparinized EDC-alone treated group and heparinized PEI -alone group. We could observe enhanced ability to adhesion and proliferation via modest moisture and effective controlled binding and release of VEGF. Conclusion： Binding of VEGF in heparinized EDC treated group was stable, while reiease of VEGF in heparinized treated group was adjusted freely. Interestingly, controlled binding and release of VEGF could exert beneficial effect on adhesion and proliferation of ECs in heparinized EDC-PEI treated group.

Mechanosynthesis of polymer-stabilized lead bromide perovskites:Insight into the formation and phase conversion of nanoparticles

The application of polymers to replace oleylamine(OLA)and oleic acid(OA)as ligands for perovskite nanocrystals is an effective strategy to improve their stability and durability especially for the solution-based processing.Herein,we report a mechanosynthesis of lead bromide perovskite nanoparticles(NPs)stabilized by partially hydrolyzed poly(methyl methacrylate)(h-PMMA)and highmolecular-weight highly-branched poly(ethylenimine)(PEI-25K).The as-synthesized NP solutions exhibited green emission centered at 516 nm,possessing a narrow full-width at half-maximum of 17 nm and as high photoluminescence quantum yield(PL QY)as 85%,while showing excellent durability and resistance to polar solvents,e.g.,methanol.The colloids of polymer-stabilized NPs were directly processable toform stable and strongly-emitting thin films and solids,making them attractive as gain media.Furthermore,the roles of h-PMMA and PEI-25K in the grinding process were studied in depth.The h-PMMA can form micelles in the grinding solvent of dichloromethane to act as size-regulating templates for the growth of NPs.The PEI-25K with large amounts of amino groups induced significant enrichment of PbBr_(2)in the reaction mixture,which in turn caused the formation of CsPb_(2)Br_(5)-mPbBr_(2)and CsPbBr_(3)-Cs_(4)PbBr_(6)-nCsBr NPs.The presence of CsPbBr_(3)-Cs_(4)PbBr_(6)-nCsBr NPs was responsible for the high PL QY,as the Cs_(4)PbBr_(6)phase with a wide energy bandgap can passivate the surface defects of the CsPbBr_(3)phase.This work describes a direct and facile mechanosynthesis of polymer-coordinated perovskite NPs and promotes in-depth understanding of the formation and phase conversion for perovskite NPs in the grinding process.

Methyl Orange removal by a novel PEI-AuNPs-hemin nanocomposite

A novel poly（ethyleneimine）/Au nanoparticles/hemin nanocomposite （PEI-AuNPs-Hemin） acting for Methyl Orange （MO） removal has been synthesized. PEI-AuNPs was prepared firstly and it was then linked to heroin through the coupling between carboxyl groups in hemin and amino groups in PEI without the activation of carboxyl groups. The high reactivity and stability of AuNPs contributed greatly in the formation of the amido bonds in the nanocomposite. Fourier transform infrared spectroscopy, transmission electron microscopy and UV-visible spectroscopy were used to characterize the PEI-AuNPs-Hemin. Results show that PEI-AuNPs-Hemin has strong adsorption for MO. Adsorption and degradation experiments were carried out at different pHs, nanocomposite concentrations and UV irradiation times. Removal of MO in acidic solutions was more effective than in basic solutions. The real-time study showed that the MO degradation with the nanocom- posite under UV irradiation was a fast process. In addition, the photocatalytic degradation mechanism was proposed. The study suggests that the PEI-AuNPs-Hemin may have promising applications in environmental monitoring and protection.