Abstract
Crystalline linear polyethyleneimine (LPEI) is a fascinating polymer that can be used as a catalyst, template and scaffold in order to direct the formation of silica with controllable compositions and spatial structures under mild conditions. Considering the crystallization and assembly of LPEI is temperature-dependent, we adopted different accelerated cooling processes of a hot aqueous solution of LPEI in order to modulate the LPEI crystalline aggregates. We then used them in the hydrolytic condensation of alkoxysilane. A series of silica with nanofibrils, nanotubes and nanowire-based structures were achieved simply by the LPEI aggregates which were pre-formed in defined cooling processes. These specific one-dimensional nanoscale structures assembled into microscale fibers-, sheet- and platelet-like coalescences. Furthermore, the deposition kinetics was also researched by the combination of other characterizations (e.g., pH measurement, 29Si MAS NMR). As a preliminary application, the hybrids of LPEI@SiO2 were used not only as an agent for reducing PtCl42− into Pt but also as host for loading Pt nanoparticles. The Pt-loaded silica showed good catalytic properties in the reduction of Rhodamine B by dimethylaminoborane (DMAB).
Highlights
Tailoring materials on controlled architectures and compositions is of lasting importance for materials scientists since the properties and performance of materials are strongly dependent upon their structured compositions
Accumulated knowledge on biosilicification has revealed that a family of long-chain polyamines in organisms plays several key roles in the fabrication of silica: (i) Long-chain polyamines self-assemble into defined structures to act as templates and scaffolds for directing the spatial structure of silica; (ii) the specific functional groups contained in the long-chain polyamines can promote the hydrolysis and condensation of silica source and the subsequent aggregation of silica species
We have found many simple factors such as solvents, pH, concentrations and additives to modulate linear polyethyleneimine (LPEI) aggregates from aqueous solution during the natural cooling process [15,16,17,18,19,20,21,22,23,24]
Summary
Tailoring materials on controlled architectures and compositions is of lasting importance for materials scientists since the properties and performance of materials are strongly dependent upon their structured compositions. To overcome some shortcomings of our previous methods and to achieve the diverse technique of sophisticated silica processing seen in biological systems, we further attempted to develop controllable and scalable approaches for modulating 1D structure-based LPEI aggregates and their directing silica formation. Since the crystallization of LPEI is temperatures-dependent, it was expected that nucleation and growth of crystalline LPEI aggregates should be controlled by the temperature change in the cooling process. To confirm this idea, several accelerated cooling processes different from the previous natural cooling was chosen and conducted by the direct addition of given amounts of the crushed ice to.
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