Effect of thermal post-treatment to increase the antibacterial activity of biogenic ZnO nanoparticles and implementation as a flexible nanogenerator
González-Montes de Oca Roel, Villanueva-Ibáñez Maricela, Jaramillo-Loranca Blanca Estela, Luis-Raya Gilgamesh, Castillo-Ojeda Roberto Saúl
Polytechnic University of Pachuca
Portable electronic devices are reducing their dimensions and improving their applications every day, but they need small and long-lasting power sources. One way to achieve this is through development of nanogenerators that allow harnessing energy from the environment like mechanical energy. Its implementation can be in daily use clothing based on lead-free piezoelectric nanomaterial fibers with antibacterial properties. In this work, the effect of thermal post-treatment (TPT) on the antibacterial activity of ZnO nanostructures obtained by biosynthesis using the aqueous extract of Schoenoplectus californicus was studied. The biosynthesis of the ZnO NPs was carried out at a temperature of 30 °C for 4 h and the biogenic ZnO was sintered at 700°C. Characterization by UV-Visible spectroscopy denoted the characteristic absorption peak of ZnO at 342 nm. Raman spectroscopy showed the ZnO band at 425 cm-1 and the presence of oxygen vacancies at 525 cm-1. The intensity ratio shows an increase in crystallinity and a decrease in the relative intensity of the 525 cm-1 band. Triangular scales, prisms, and irregular spheres of submicron sizes were observed by scanning electron microscopy (SEM). By dynamic light scattering (DLS), the increase in size in the nanostructures was observed, identifying two populations of interest: the first changed from 233nm to 302nm (30%) and the second changed from 931nm to 1435nm (54%). X-ray diffraction confirmed a hexagonal structure with an average crystal size of 30 nm. The antibacterial activity was correlated with the structural and superficial changes presented by the sensitivity of Gram-positive and Gram-negative bacteria, with a similar effect in both cases before TPT since the bacteria are inhibited by contact with the ZnO NPs that were subjected to TPT. Electric power generation was determined from a flexible biogenic ZnO film on PVA. The voltage obtained was 2.4 Vpp. Through a diode rectifier bridge, the energy was stored in a capacitor, reaching a voltage of 5 VDC.