Turkish Journal of Chemistry
Abstract
In this study, the effects of number of washes, oxidation degree, carboxylation, and hydrothermal reduction temperature on the antibacterial activity of graphene oxide (GO) and reduced graphene oxide (rGO) nanomaterials were investigated. GO derivatives with different numbers of washes (1–5W) and oxidation levels (3X, 6X, and 9X), carboxylated GO (GO-COOH), and rGO samples obtained at different hydrothermal reduction temperatures (100, 140, and 180 °C) were characterized by X-ray diffraction, field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, zeta potential analysis, and Raman spectroscopy, and were subsequently evaluated for antibacterial activity against gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli). The washing experiments showed that, in the presence of residual acids (1W), a 5-log reduction was achieved for S. aureus at 600 μg/mL, whereas after acid removal (5W), purified GO produced a 2-log reduction at the same concentration. In contrast, no meaningful change in activity was observed for E. coli as a function of number of washes (~1 log). In the oxidation optimization experiments, the 6X oxidation level yielded the highest antibacterial efficacy against S. aureus, producing a 5-log reduction at 800 μg/mL, while excessive oxidation (9X) led to a plateau in activity because of structural defects. Carboxylation decreased activity against S. aureus by 40% at 800 μg/mL (from 5 log to 3 log) because of electrostatic repulsion, while leaving the already low activity against E. coli (~1 log) unchanged. In the hydrothermal reduction experiments, partial reduction at 100 °C produced the optimal hydrophilic–hydrophobic balance for S. aureus (3-log reduction at 240 μg/mL), whereas the higher hydrophobicity at 180 °C enabled effective inhibition of E. coli (2- to 3-log reduction at 180–240 μg/mL). These findings show that antibacterial efficacy depends on the compatibility between surface chemical properties and bacterial cell-wall structure.
Author ORCID Identifier
EMİR BOZTEPE: 0009-0007-5748-0040
CEREN POYRAZ: 0009-0003-3249-771X
RUKİYE TAŞDEMİR: 0000-0002-1150-1420
EBRU ÖNEM: 0000-0002-7770-7958
ÜMRAN SOFU: 0000-0001-6563-8441
KERİM YAPICI: 0000-0002-3902-9375
DOI
10.55730/1300-0527.3919
Keywords
Graphene oxide, reduced graphene oxide, antibacterial activity, hydrothermal reduction, bacteria-material interaction
First Page
554
Last Page
569
Publisher
The Scientific and Technological Research Council of Türkiye (TÜBİTAK)
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
BOZTEPE, E, POYRAZ, C, TAŞDEMİR, R, ÖNEM, E, SOFU, Ü, & YAPICI, K (2026). Effects of washing, oxidation, carboxylation, and hydrophobicity on the antibacterial activity of graphene oxide and reduced graphene oxide. Turkish Journal of Chemistry 50 (5): 554-569. https://doi.org/10.55730/1300-0527.3919
