Fabrication and characterization of antibacterial surfaces derived from geranium essential oil using PECVD

Essential oils and plant extracts are rich sources of biologically-active compounds that can be used for manufacturing of antibacterial surfaces. This thesis reports the fabrication of pristine polymers, and zinc oxide/polymer films from geranium essential oil utilizing low power plasmaenhanced chemical vapor deposition technique (PECVD). The topographical, optical, mechanical, chemical, electrical and antibacterial properties of the fabricated films were in-depth studied. Geranium-derived polymer films were fabricated at various input RF power. The resultant polymer were founded to be optically transparent in the visibly region. The refractive index, extinction coefficient, and optical band gap were found to be not significantly dependent on the RF power. The crosslinking of the material increased with increasing input power. The topographical features appeared to be uniform, smooth, and pinhole free for all samples, and the surface roughness increased with an increase in the input power. Sample fabricated at 10 W demonstrated a remarkable reduction in the number of cells, biovolume, or biofilm thickness, while there was no significant difference in the bacterial growth between samples fabricated at 50 W and control. Zinc oxide nanoparticles were incorporated in the fabricated polymer films via a single-step approach that combines simultaneous plasma polymerization of geranium oil with thermal decomposition of zinc acetylacetonate Zn(acac)₂. The resultant nanocomposite thin films were systematically investigated. XPS survey proved the presence of ZnO in the matrix of formed polymers at 10 W and 50 W. SEM images demonstrated that the average size of ZnO nanoparticle slightly increased with an increase in the power of deposition from approximately 60 nm at 10 W to approximately 80 nm at 50 W. Confocal scanning laser microscopy images showed that viability of S. aureus and E.coli cells significantly reduced on surfaces of ZnO/composites compare to pristine polymers. The electrical properties of pristine and ZnO/composites thin films were investigated in metal– insulator–metal (MIM) structures. It was found that the capacitance of the films decreases at low frequencies (C ≈ 10⁻¹¹) and remains at a relatively constant value (C ≈ 10⁻¹⁰) at high frequencies. These films also have a low dielectric constant across a wide range of frequencies that decreases as the input RF power increases. The conductivity of pristine polymers was determined to be around 10⁻¹⁶–10⁻¹⁷ Ω⁻¹ m⁻¹, which is typical for insulating materials. Incorporation of ZnO nanoparticles into the polymer films did not change the nature of charge transport, as the nanocomposite films were found to behave as an insulator. However, the conductivity slightly of nanocomposite materials slightly improved measuring 10⁻¹⁴ Ω⁻¹ m⁻¹. Increasing the input power, along with introducing hydrogen gas to the plasma tube, produces desired sp2-bonded carbon nanostructures such as graphene materials. PECVD) had been utilized for the fabrication of high-quality vertically erected graphene nano-walls from geranium essential oil. The graphene synthesized using well-controllable system directly on silicon and quartz substrates without use any catalyst. SEM showed that the formed graphene had a length of few hundreds nanometers with thickness of 7 to 25 nm. AFM further confirmed the very sharp edges of the produced graphene. The material revealed relatively high water contact angle value ranging around 123˚. Antibacterial performance of graphene nano-walls was studied against grampositive and gram-negative microorganisms. Confocal scanning laser microscopy images demonstrated that the viability of E.coli and S. aureus cells were 32% and 38% were alive on graphene compare to controls, respectively.