  This work explores the antimicrobial efficacy of ZnO nanoparticles (NPs)
films with varying microstructure, crystallographic orientation and surface
roughness. Thin films with different microstructures were obtained by varying
precursor concentrations (0.1 M, 0.25 M, and 0.4 M) and solvent types (Ethanol,
Propanol, and Butanol). The characterization of the films by X-ray diffraction
(XRD) revealed films with varying degrees of orientation along the c-axis,
which increased with the concentration of the precursor and with the decrease
in the carbon chain length of the alcohol. Raman spectroscopy analysis
confirmed the formation of a hexagonal wurtzite ZnO. Scanning Electron
Microscopy (SEM) analysis revealed the formation of dense and homogeneous films
with a thickness of 93 nm. Atomic force microscopy (AFM) showed changes in
surface irregularity and an increase in surface roughness with the carbon
length of solvent and a maximum roughness at a precursor concentration of 0.25
M in propanol. The antimicrobial activity was assessed following ISO 22196:2011
standards with few modifications. Results indicated that ZnO NPs films with
rougher surfaces reduced coli (gram(-)), Pseudomonas aeruginosa (gram(-)) and
Staphylococcus aureus (gram(+) ) bacteria populations due to an increase of
contact surface between NPs with bacteria. Their effectiveness against Candida
albicans was moderate, with a maximum reduction of 0.72 Log10 CFU/cm$^2$ with
rougher film.
