Fig. 1

Morphological structure evolution. a Schematic illustration of the whole synthetic process. The inset TEM images in a correspond to O-iGZNFs and O-dGZNFs. b SEM image of as-spun NFs. HR-TEM images and SAED patterns of c O-iGZNFs and d O-dGZNFs. e HAADF-STEM mapping of O-dGZNFs: red—carbon, orange—nitrogen, yellow—oxygen, cyan—germanium, and green—zinc. Scale bars: a 500 nm, b 10 μm, c, d 5 nm and 5 1/nm, and e 50 nm