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Abstract: In the present study, two types of graphene quantum dots (GQDs) were investigated: green-emitting (G-GQDs) and blue-emitting (B-GQDs). Physicochemical characterisation was performed using transmission electron microscopy (TEM), zeta potential, and hydrodynamic radius measurements to evaluate the morphology, particle size, aggregation behaviour, and colloidal stability of the GQDs in both water and cell culture medium. G-GQDs exhibited superior colloidal stability and more uniform dispersion than B-GQDs, whereas both types showed reduced aggregation and surface charge in cell culture medium due to protein corona formation. Toxicological characterisation was performed using an in vitro human hepatocellular carcinoma (HepG2) 3D spheroid model, with GQDs exposures up to 250 µg/mL (100 µg/cm2). Cytotoxicity was measured using the CellTiter-Glo luminometric assay, while genotoxicity was evaluated by the comet assay and flow cytometric analysis of γH2AX and phosphorylated histone H3 (p-H3) after 24 h of exposure. Both GQDs induced dose-dependent cytotoxic effects in HepG2 spheroids. At non-cytotoxic concentrations, a dose-dependent increase in DNA damage was observed, as determined by the comet assay. However, no evidence of DNA double-strand breaks (γH2AX) or elevated p-H3 levels was detected, suggesting the absence of clastogenic and aneugenic activity. The observed DNA single-strand breaks may be partly attributed to reactive oxygen species induction. These results indicate that, although GQDs induced cytotoxicity and single-strand DNA damage, no clear evidence of more severe genotoxic effects was observed under the tested conditions. Further studies are warranted to elucidate underlying mechanisms and comprehensively assess the safety profile of GQDs for biomedical applications.
Keywords: nanomaterials, graphene quantum dots, HepG2 spheroids, toxicity
Published in DiRROS: 19.03.2026; Views: 244; Downloads: 73
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Keywords: gamma irradiation, nanocomposite, graphene oxide, silver nanowire
Published in DiRROS: 26.02.2026; Views: 263; Downloads: 117
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Abstract: The outbreak of the Coronavirus disease 2019 (COVID-19) pandemic has highlighted the importance of developing antiviral surface coatings that are capable of repelling pathogens and neutralizing them through self-sanitizing properties. In this study, a novel coating design based on few-layer graphene (FLG) is proposed and silver-decorated micro copper flakes (CuMF) that exhibit both antibacterial and antiviral properties. The role of sacrificial anode surfaces and intrinsic graphene defects in enhancing the release of metal ions from CuMF embedded in water-based binders is investigated. In silico analysis is conducted to better understand the molecular interactions of pathogen-repelling species with bacterial or bacteriophage proteins. The results show that the optimal amount of CuMF/FLG in the coating leads to a significant reduction in bacterial growth, with reductions of 3.17 and 9.81 log for Staphylococcus aureus and Escherichia coli, respectively. The same coating also showed high antiviral efficacy, reducing bacteriophage phi6 by 5.53 log. The antiviral efficiency of the coating is find to be doubled compared to either micro copper flakes or few-layer graphene alone. This novel coating design is versatile and can be applied to various substrates, such as personal protective clothing and face masks, to provide biocidal activity against both bacterial and viral pathogens.
Keywords: antibacterial, antiviral, copper micro flakes, few-layer graphene, pathogen-repelling coating
Published in DiRROS: 16.12.2025; Views: 307; Downloads: 228
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Abstract: Using scanning tunneling microscopy (STM) and inelastic tunneling spectroscopy, the low-frequency vibrational modes of a 7-atom wide armchair graphene nanoribbon (7-AGNR) is mapped. The inelastic tunneling channel is enhanced over the elastic one by a covalently bonded 7-AGNR to the apex of an STM tip. This setup has led to resonant inelastic tunneling between vibrational states of supported 7-GNR on Au(111) substrate and the states of the functionalized STM tip. The low-energy spectra reveal two localized peaks at the armchair edges with energies at ±14 and ±30 mV. The peaks are assigned to twice the energies of longitudinal compressive and shear-like modes of 7-AGNR, respectively. Remarkably, the well-separated peaks evolve rapidly into one broader peak toward the bulk of the ribbon due to scattering from substrate interactions. This suggests that edge state phonons are uniquely protected from the microenvironment and may have a profound effect on the transport properties of GNR devices.
Keywords: scanning tunneling microscopy, inelastic tunneling spectroscopy, armchair graphene nanoribbons
Published in DiRROS: 12.09.2025; Views: 440; Downloads: 259
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Abstract: We have developed a significantly enhanced method for the effective and homogeneous decoration of graphene oxide (GO) and reduced graphene oxide (r-GO) flakes with gold (Au) and platinum (Pt) nanoparticles. This method involves the direct nucleation of nanoparticles on the surface of dispersed GO through a single-step reaction. By carefully controlling the stepwise introduction of gold and platinum complexes at elevated temperatures, without additional reducing agents, we successfully achieved a homogeneous distribution of Au and Pt nanoparticles, ∼ 20 nm and ∼ 3 nm in size, densely covering the GO sheets. The decoration yield in a mass ratio between Au and GO was up to 20 %. Reduced GO with attached gold and platinum nanoparticles was obtained using ascorbic acid as a reducing agent. Finally, we embedded Au-decorated r-GO in polydimethylsiloxane (PDMS) to form a composite. We show how this stable hybrid material composite can be spin-coated to form a thin thermoelastic film on a flexible substrate, enabling promising photoacoustic properties that could be exploited further in biomedical applications.
Keywords: graphene oxide, decoration, nanoparticles, nanocomposites
Published in DiRROS: 04.06.2025; Views: 712; Downloads: 361
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