Strong blue-light emission in flexible branched nanowire-on-nanowire pristine ZnO nanoarchitectures constructed via tandem multiprong growth†

Zinc oxide (ZnO) exhibits an outstanding ability to form a wide range of nano/microstructures. At an enhanced environmental temperature (T_E = 33.1 °C), flexible branched single-crystalline (SC) nanowire-on-nanowire (NW-on-NW) pristine ZnO nanoarchitectures (NAs) have been synthesized for the first time through a simple ambient-pressure vapor-phase transport (VPT) process. We proposed that the construction of the spider-plant-like ZnO NAs is via a tandem multiprong vapor–solid–solid growth mode using larger gold catalysts, instead of the conventional single-prong vapor–liquid–solid growth mechanism. Notably, unlike the previous results for single-component SC ZnO NWs, unexpectedly, the oxygen-deficient SC NW-on-NW pristine ZnO NAs exhibit a very strong solitary blue-light (BL) emission peak at 494 nm, where a self-activated multiphoton process called a hierarchical photonic chain reaction (HPCR) mechanism was suggested. Our work enriches the VPT-grown flexible branched SC NW-on-NW pristine ZnO NAs with BL photoluminescence, and provides the first evidence for the multiprong growth that was predicted many years ago.