Surface Modification of ZnO Nanoparticles with L-Serine and Preliminary Antibacterial Properties Against Escherichia coli

Due to bacterial mutation and evolution to survive and to the misuse of antibiotics, there is greater resistance to different medications among different bacteria. This study presents the modification of ZnO nanoparticles with L-serine via ultrasound, their physicochemical evaluation, and antibacterial performance against Escherichia coli (E. coli). Among the most significant results are: by FT-IR, a union between the carbonyl and amino groups of two L-serine amino acids was observed, indicating the formation of a peptide bond corresponding to amide group II. In the TGA of the samples modified with L-serine, weight losses between 360 and 455 °C were observed, supporting that the chemical modification was effective for both reaction times (60 and 90 min). In XRD, it could be observed that the characteristic peak of L-serine is at 22.8°, and there are other signals that oscillate between 10 and 20° of the peptide interlaces formed between the amino acids present in the modified particles. XPS analysis showed that, for the samples modified with L-serine, the N1s and C1s signals appeared, and deconvolution was performed for these signals in order to see their interactions in the chemical environment. The value of zeta potential of the sample ZnOMOD90 showed a bigger change. TEM images indicated that the ZnO pure nanoparticles have a hemispherical morphology and a size of approximately 24 nm, while ZnOMOD90 nanoparticles have a size of approximately 53 nm. Modified ZnO nanoparticles increased the inhibition zone halo for the ZnOMOD90 sample to 31 mm against E. coli bacteria, compared to pure ZnO, which had an inhibition zone of only 1 mm.