Enhanced UV Flexible Photodetectors and Photocatalysts Based on TiO2 Nanoplatforms

Abstract: In this study, titanium dioxide (TiO2) nanostructured films were synthesized under microwave irradiation through low temperature synthesis (80 °C) and integrated in ultraviolet (UV) photodetectors and as photocatalysts. Bacterial nanocellulose (BNC), tracing paper, and polyester film were tested as substrates, since they are inexpensive, flexible, recyclable, lightweight, and when associated to low temperature synthesis and absence of a seed layer, they become suitable for several low-cost applications. The nanostructured TiO2 films and substrates were structurally characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. The optical properties of all materials were investigated. The TiO2 nanostructured films were implemented as a photoactive layer of UV photodetectors and demonstrated significant increase of conductance upon exposed to UV irradiation. The photodetection behaviour of each material was investigated by in-situ Kelvin probe force microscopy experiments, in which the contact potential difference varied under dark or UV irradiation conditions, demonstrating higher shift for the BNC-based UV photodetector. Photocatalytic activity of the films was assessed from rhodamine B degradation under solar radiation, and BNC based devices revealed to be the best photocatalyst. The structural characteristics of the TiO2 films and substrates were correlated to the differences in the UV photodetection and photocatalytic performances. Graphical Abstract: [Figure not available: see fulltext.]

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The work was supported by the FCT-Portuguese Foundation for Science and Technology, through the scholarship BPD/84215/2012. This work is also funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT -Portuguese Foundation for Science and Technology under the project number POCI-01-0145-FEDER-007688, Reference UID/CTM/50025/2013. The Center of Biological Engineering acknowledges funding through UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684).