Abstract
Flame spray pyrolysis was a process to produce oxide nanoparticles in a self-sustaining flame. When the produced nanoparticles were deposited on a substrate, nanostructured oxide thin films could be obtained. However, the size of the thin film was usually limited by the fixed substrate. Here, we demonstrated that thin film with a large area could be deposited by using the moving substrate, which was precisely controlled by servo motors. As a result, the flame tip could scan over the substrate and deposit the nanoparticles on it line by line, analogues to a printing process called flame-assisted printing (FAP). As an example, nanostructured bismuth-oxide thin films with a size of up to 20 cm × 20 cm were deposited with the FAP process. The bismuth-oxide thin film exhibited a stable electrochromic property with a high modulation of 70.5%. The excellent performance could be ascribed to its porous nanostructure formed in the FAP process. The process can be extended to deposit other various oxides (e.g., tungsten-oxide) thin films with a large size for versatile applications.
Highlights
Flame spray pyrolysis (FSP) was a process, in which solvent with the dissolved metal precursor was sprayed into liquid droplets
We proposed a flame-assisted printing (FAP) process based on FSP to fabricate porous bismuth-oxide thin film on fluorine-doped tin oxide (FTO)
During the process of FAP, porous structure comes into being with the formation of nanoparticles, primary particles and large particles [28]
Summary
FSP was a process, in which solvent with the dissolved metal precursor was sprayed into liquid droplets. The size of the produced powders ranges from a few nanometers to micrometers. FSP can be employed to produce oxide nanopowders (e.g., SiO2, TiO2, CeO2 and Al2O3) in a commercial scale [6–9]. The nanopowders from the FSP process can be either dropped or cast on the substrate to form the thin films, those films are usually dense with a low surface area, lacking nanofeatures. For the applications such as sensors, electrochemical and photoelectrochemical (PEC) devices, thin films with the porous structure are preferred [10–12].
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