A spontaneous combustion reaction for synthesizing Pt hollow capsules using colloidal carbon spheres as templates

Here we report a spontaneous combustion reaction in synthesizing Pt hollow capsules. In brief, Pt nanoparticles were loaded on the surface of colloidal carbon spheres by wet-chemical impregnation. When Pt-loaded carbon spheres were taken out of an argon-filled tube furnace at room temperature and exposed to air, they underwent spontaneous combustion. The internal carbon spheres templates were removed to leave nanostructured Pt hollow capsules. There are at least two critical conditions for the occurrence of the spontaneous combustion: the Pt particle size is below 5.8 nm, and the hydrogen content in the carbon spheres is above 2.570 wt %. Such a reaction is interesting for the preparation of metal hollow spheres and is also relevant with respect to removal of accumulated carbon on catalysts and for soot oxidation at room temperature.     

Non‐invasive probing of pharmaceutical capsules using transmission Raman spectroscopy

We demonstrate how transmission Raman geometry can be effectively used for non‐invasive probing of the content of pharmaceutical capsules. This approach is particularly beneficial in situations where the conventional Raman backscattering method is hampered or fails because of excessive surface Raman or fluorescence signals emanating from the capsule shell material, which pollute the much weaker subsurface Raman signals with undesired noise. It is demonstrated that such interfering signals can be effectively suppressed by the transmission geometry. The ability to avoid surface fluorescence and Raman signals in conjunction with the superior, bulk‐probing properties of the transmission Raman geometry provides an analytical technique ideally suited for fast on‐line process control monitoring applications in pharmaceutical industry where rapid, chemically specific bulk analysis is required. Copyright © 2007 John Wiley & Sons, Ltd.     

Polyelectrolyte complex capsules as a material for enzyme immobilization

The polyelectrolyte complex (PEC) membrane formed by cellulose sulfate and poly(dimethyldiallylammonium chloride) was used to encapsulate lactate dehydrogenase. The exclusion limit of the membrane was found to be low enough to secure irreversible entrapping of the enzyme. The obtained capsules were checked for their functionality in a stirred-batch reactor by following the kinetics of NADH oxidation. The data were fitted with an isotropic kinetic model including competitive product-inhibition phenomenon. The results of mathematical modeling demonstrated that the anisotropic system, like PEC capsules, could be satisfactorily described by the isotropic model.     

Selective Encapsulation of Disaccharide Xylobiose by an Aromatic Foldamer Helical Capsule

Xylobiose sequestration in a helical aromatic oligoamide capsule was evidenced by circular dichroism, NMR spectroscopy, and crystallography. The preparation of the 5 kDa oligoamide sequence was made possible by the transient use of acid‐labile dimethoxybenzyl tertiary amide substituents that disrupt helical folding and prevent double helix formation. Binding of other disaccharides was not detected. Crystallographic data revealed a complex composed of a d ‐xylobiose α anomer and two water molecules accommodated in the right‐handed helix. The disaccharide was found to adopt an unusual all‐axial compact conformation. A dense network of 18 hydrogen bonds forms between the guest, the cavity wall, and the two water molecules.     

内置胶囊混凝土的裂缝自愈合行为分析和试验

研究了一种具有裂缝自愈合行为的内置胶囊混凝土.首先,建立了描述修复胶囊在混凝土中的分布和取向函数;然后,根据混凝土的破坏机理,确定了修复胶囊的破坏应力;第三,通过实验分析了修复胶囊的几何参数和体积率对混凝土性能的影响,得到了几何参数和体积率的最佳取值范围;第四,利用ANSYS对修复胶囊进行了有限元分析,确定了其合理的壁厚,为修复胶囊材料的选择提供了一种研究方法;最后,进行了内置胶囊混凝土试验,取得了一定的自愈合效果.     

Tuning the Guest‐Binding Ability of a Helically Folded Capsule by In Situ Modification of the Aromatic Oligoamide Backbone

Starting from a previously described aromatic oligoamide helically folded capsule that binds tartaric acid with high affinity and diastereoselectivity, we demonstrate the feasibility of the direct in situ modification of the helix backbone, which results in a conformational change that reduces its affinity for guests by two orders of magnitude. Specifically, ring contraction of the central pyridazine unit into a pyrrole in the full helical sequence was investigated by using electrochemical and chemical processes. The sequence containing the pyrrole was synthesized independently in a convergent manner to ascertain its structure. The conformation of the pyrrolic folded capsule was elucidated in the solid state by X‐ray crystallography and in solution by using ¹H and ¹³C NMR spectroscopy. Solution studies revealed an unanticipated solvent‐dependent equilibrium between the anti–anti and syn–syn conformations of the pyrrole ring with respect to its two adjacent pyridine units. Titrations of the pyrrole‐containing sequence monitored by ¹H NMR spectroscopy confirmed the expected drop in affinity for tartaric acid and malic acid that arises from the conformation change in the backbone that follows the replacement of the pyridazine by a pyrrole. The reduction of the pyridazine to a pyrrole was characterized by cyclic voltammetry both on the entire sequence and on a shorter precursor. The lower cathodic potential of the precursor made its preparative‐scale electroreduction possible. Direct in situ modification of the pyridazine within the entire capsule sequence was achieved chemically by using zinc in acetic acid.