Crafting cellulose hollow microspheres with cellulose nanosheets

Nano-/micro-cellulose has attracted significant attention in advanced materials due to its cellulosic properties as well as the important hallmarks of nano-/micro-materials. However, current approaches for the preparation of them are predominantly limited to "top-down" strategies which yield mostly whisker-/fiber-like morphologies. Therefore, it is imperative to develop cellulose-based nano-/micro-materials with diversified architectures. Here, we report the preparation of cellulose nanosheets composed of cellulose nanofibrous network, using cellulose solution as the precursor, via a "bottom-up" strategy. Due to its excellent water dispersibility and stability, these cellulose nanosheets can be assembled to form cellulose hollow microspheres through an ice-melting-induced lyophilization technique. The property and application of the cellulose microspheres can be further expanded by preparing composite microspheres via co-assembling cellulose nanosheets with functional nanomaterials. This work not only provides a simple, mild, and green approach through a new type of "bottom-up" strategy which may shed light on the design and preparation of nano-/micro-materials, but also offers novel cellulose-based nano-/micro-materials which may find wide applications in various fields due to the distinct architectures.