Graphene oxide (GO) can affect the antibacterial ability of antibiotics by serving as an antibiotic carrier. However, the mechanisms for the antibacterial activity of a combination of GO and antibiotics are not known. In this study, we examined the effect of GO on the antibacterial activity of three antibiotics (i.e., lincomycin hydrochloride (LMH), chloramphenicol (CPC) and gentamycin sulfate (GMS)) against Gram-negative Escherichia coli bacteria (e.g. E. coli) and Gram-positive Staphylococcus aureus bacteria (e.g. S. aureus). GO will coat on the bacteria and cause cell membrane damage, assisting growth inhibition of bacteria, with a stronger effect on S. aureus than E. coli. The inactivation of E. coli and S. aureus with bare GO is concentration- and time-dependent. The presence of GO increases or decreases the antibacterial ability of antibiotics, depending on the interaction of GO with the antibiotic, the interaction of GO with bacteria, and the sensitivity of bacteria to the antibiotic. The contact order of GO, the antibiotic and the bacterium has a notable effect on the combined antibacterial activity of antibiotics and GO. The pretreatment of GO with bacteria will increase the antibacterial ability of LMH and CPC significantly, while LMH and CPC show relatively low sensitivity to bacteria. The combination of GO and different antibiotics provides different extents of antibacterial efficiency toward microorganisms.

A series of Zn_xCd_1−xS photocatalysts were synthesized via a solvothermal method using ethylenediamine (EDA) as the solvent. The structural, optical and morphological properties have been investigated extensively by various analytical techniques. It has been found that Zn_xCd_1−xS (x ≤ 0.5 in the precursor) nanorods and nanoparticles can be formed as good homogeneous solid solutions. During the synthesis process, EDA played an important dual role as the solvent and the coordinating agent, which contributed to the formation of nanosized Zn_xCd_1−xS solid solutions. Efficient hydrogen production from the aqueous solution containing S²⁻ and SO₃ ^{2 −} sacrificial reagents was observed over these photocatalysts under visible light irradiation (λ ≥ 420 nm) in the absence of any expensive metal components and co-catalysts. The highest photocatalytic activity for hydrogen production was obtained over Zn_0.5Cd_0.5S with a rate of 1097 μmol h⁻¹ and the corresponding quantum efficiency of 30.4% at 420 nm. These values are much higher than those previously reported for Zn–Cd binary sulfide photocatalysts. The excellent photocatalytic performance can be attributed to the efficient visible light absorption and the suitable band structure due to the formation of solid solutions.

Ni²⁺-doped photocatalysts Ni(y)-Zn_xCd_1−xS (where 0 ≤ x ≤ 0.80, 0% ≤ y ≤ 8%) were prepared by a two-step route, which consisted of a first precipitation of single-source precursors and a subsequent solvothermal treatment of the precursors in ethylenediamine. Structural, morphological and optical properties of the as-prepared samples were characterized by XRD, UV-vis DRS, FESEM, TEM, N₂ physisorption, ICP-AES and XPS techniques. The photocatalytic activity was evaluated for hydrogen evolution from the aqueous solution containing sodium sulfide and sodium sulfite under visible light irradiation. All Ni²⁺-doped samples exhibit enhanced photocatalytic activity compared with the non-doped sample. Sample Ni(4%)-Zn_0.4Cd_0.6S gives the highest hydrogen evolution rate of 941 μmol h⁻¹ under the optimized reaction conditions without any co-catalysts, with a corresponding quantum efficiency of 22.8% at 420 nm which is much higher compared to those of previously reported Ni²⁺-doped metal sulfide photocatalysts. It is suggested that good crystallinity, suitable band structure and the accommodation sites introduced by Ni²⁺ doping for charge carrier separation together contribute to the high activity of such photocatalysts for hydrogen evolution.