From 1D Nanofibers to 3D Nanofibrous Aerogels: A Marvellous Evolution of Electrospun SiO2 Nanofibers for Emerging Applications

Abstract

One-dimensional (1D) SiO2 nanofibers (SNFs), one of the most popular inorganic nanomaterials, have aroused widespread attention because of their excellent chemical stability, as well as unique optical and thermal characteristics. Electrospinning is a straightforward and versatile method to prepare 1D SNFs with programmable structures, manageable dimensions, and modifiable properties, which hold great potential in many cutting-edge applications including aerospace, nanodevice, and energy. In this review, substantial advances in the structural design, controllable synthesis, and multifunctional applications of electrospun SNFs are highlighted. We begin with a brief introduction to the fundamental principles, available raw materials, and typical apparatus of electrospun SNFs. We then discuss the strategies for preparing SNFs with diverse structures in detail, especially stressing the newly emerging three-dimensional SiO2 nanofibrous aerogels. We continue with focus on major breakthroughs about brittleness-to-flexibility transition of SNFs and the means to achieve their mechanical reinforcement. In addition, we showcase recent applications enabled by electrospun SNFs, with particular emphasis on physical protection, health care and water treatment. In the end, we summarize this review and provide some perspectives on the future development direction of electrospun SNFs.

3D fibrous aerogels from 1D polymer nanofibers for energy and environmental applications

“…7b). 56 The shapes of 3D fibrous aerogels (Fig. 7c) can be controlled, and the fabrication is possible to be scaled up by simply using a large shaping mold.…”

“…Since then, the freeze-drying technique has been widely used to prepare 3D brous aerogels of nanocellulose, ceramics, metals, carbon nanotubes (CNTs), graphene, graphene oxide (GO), and biopolymers. [47][48][49][50][51][52][53][54][55] Subsequently, Ding's group 56 rst reported to use shortened electrospun nanobers as the building blocks to prepare 3D brous aerogels by the freeze-drying technique. The formation mechanism of interconnected and hierarchically structured pores of 3D brous aerogels is shown in Fig.…”

“…(f) Optical and infrared images of ceramic fibrous aerogels exposed to a butane blowtorch for 120 s. Reproduced with permission. 56 Copyright 2020, Springer Nature. (g) Optical photograph of the front side subjected to a butane blowtorch flame.…”

Flexible-in-rigid polycrystalline titanium nanofibers: a toughening strategy from a macro-scale to a molecular-scale

“…As a result, the switchable bond lengths and bond angles in silicon oxygen tetrahedra endow a single SiO 2 nanofiber with surprising flexibility. 12 However, it is still a challenging task yet fascinating to produce flexible nanofibers composed of robust and polycrystalline TiO 2 , and some other functional oxides with low crystalline temperatures, such as ZrO 2 , Fe 2 O 3 , ZnO, and CeO 2 .…”

“…10 On a molecular scale, the firm and solid ionic bonds make TiO 2 inherently brittle in shearing and tension, 11 being quite different from the recently demonstrated flexible SiO 2 nanofibers featuring an amorphous nature. 12 Generally, the continuous random network of Si–O–Si bonds has multitudinous angles ranging from 120° to 180°. As a result, the switchable bond lengths and bond angles in silicon oxygen tetrahedra endow a single SiO 2 nanofiber with surprising flexibility.…”