A new soft template-oriented method for the preparation of hollow analcime microspheres with nanosheets-assembled shells

Abstract

This paper highlights a controlled synthesis of two-dimensional analcime nanosheets templated by organic additives and an impressive strategy that hollow hierarchical analcime microspheres with layered shells can be assembled by taking advantage of the intrinsic growth law of material. Specifically, ultrathin analcime nanosheets were initially obtained by precisely manipulating the amounts of cetyltrimethylammonium cation (CTA+) and ethylenediaminetetraacetate (EDTA4−) in the synthesis system. As building blocks, these nanosheets then self-assembled layer by layer from outside to inside driven by the reversed crystal growth mechanism of analcime, resulting in a hollow structure with lamellar shells and enhanced specific surface area of 722.3 m2 g−1. Series of experiments were carried out in order to explore the influence of CTA+ and EDTA4− on the formation of analcime nanosheets. The results indicated that CTA+ was the micro-mesoporogen of hierarchical analcime and synergistically collaborated with EDTA4− in directing analcime nanosheets. The effect of hydrothermal temperature was discussed and a surfactant packing parameter (g = V/a 0 l) was cited to explain the behavior of organics. In addition, the investigation of hydrothermal process clearly revealed the crystallization and self-assembly process of hollow structure. And the UV Raman results unraveled that four-membered rings (4MRs) as the active building units for analcime framework were firstly formed in the synthesis gel, followed by reconstruction and self-assembly which lead to the formation of 6MRs and 8MRs.