Paper-Based Nanoplatforms for Multifunctional Applications

Abstract

In this work, zinc oxide (ZnO) and titanium dioxide (TiO 2 ) nanostructures were grown on different cellulose paper substrates, namely, Whatman, office, and commercial hospital papers, using a hydrothermal method assisted by microwave irradiation. Pure ZnO and TiO 2 nanostructures were synthesized; however, the growth of TiO 2 above ZnO was also investigated to produce a uniform heterostructure. Continuous ZnO nanorod arrays were grown on Whatman and hospital papers; however, on office paper, the formation of nanoplates originating nanoflower structures could be observed. TiO 2 nanoparticles homogeneously covered all the substrates, in some conditions forming uniform TiO 2 films. Structural characterization was carried out by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The optical characterization of all the materials was carried out. The produced materials were investigated for multifunctional applications, like photocatalyst agents, bacterial inactivators, and ultraviolet (UV) sensors. To evaluate the photocatalytic activity under UV and solar radiations, rhodamine B was the model-test contaminant indicator and the best photocatalytic activity was achieved with Whatman paper. Hospital paper with TiO 2 nanoparticles showed significant antibacterial properties against Staphylococcus aureus. ZnO-based UV sensors demonstrated a responsivity of 0.61 μA W -1 .

TiO2 Nanostructured Films for Electrochromic Paper Based-Devices

“…Figure 2 depicts the SEM images of pristine Au paper together with the TiO 2 nanostructured films. As observed in analogous studies [10,43], the TiO 2 nanostructured films were grown on the cellulose-based substrate without any seed layer and directly on the Au contact. It has been previously stated that the paper roughness facilitates nucleation and fixation of the TiO 2 nanostructures [10].…”

“…Au comes from the contacts deposited, and no other impurities were detected. The significant presence of C and O is also related to the Whatman paper substrate used [43]. Moreover, it has been noticed that the Ti EDS map is more intense for the acetic-based film, with is expectable since this is the thicker film synthesized (Figure 3l).…”

“…Whatman chromatography paper grade two was used as substrate. This pure cellulose paper has been selected due to the lack of impurities or additives present together with its uniformly absorbent properties [42,43]. Prior to synthesis, the paper substrate was subjected to the conductive layer deposition.…”

“…Any seed layer has been used for assisting the TiO 2 growth [10,43]. Afterwards, the gold coated paper substrate was cut (30.0 × 15.0 mm) and prepared for synthesis.…”

“…Nevertheless, in the present study, the deposition parameters have been systematically maintained and highly reproducible thin films have been obtained, so the influence of Au sheet resistance is expected to be equivalent for all the devices produced. Any seed layer has been used for assisting the TiO2 growth [10,43]. Afterwards, the gold coated paper substrate was cut (30.0 × 15.0 mm) and prepared for synthesis.…”