B. Todorović Marković

Gamma ray-assisted irradiation of few-layer graphene films: a Raman spectroscopy study

This paper represents results of a Raman spectroscopy study of gamma-irradiated few-layer graphene thin films at three different doses: 25, 50 and 110 kGy. Graphene thin films were deposited by the vacuum filtration method and then transferred onto glass substrate. Raman spectroscopy and atomic force microscopy analysis have shown that the average in-plane crystallite size La of graphene thin films varies slightly when an irradiation dose is applied. Raman spectroscopy revealed that gamma irradiation of graphene thin films resulted in slight p-doping of the graphene thin film surface. It was found that during gamma irradiation at a dose of 110 kGy, the graphene sheets merged. As a result, the number of incorporated defects in the graphene structure was reduced (the ID/IG ratio decreased with the increase in the applied dose).

Novel method for graphene functionalization

In this paper we present a novel method to obtain a stable dispersion of graphene in water using carbon quantum dots as surface active agents. In this way it is possible to achieve graphene concentrations in dispersion up to 2.7 mg ml−1. Fourier transform infrared spectroscopy and UV–Vis measurements confirmed the presence of oxygen-containing functional groups in the graphene–carbon quantum dot (gCQD) structure, responsible for its good solubility in water. The stability of the gCQD dispersion is due to π–π interactions formed between graphene and graphene-like sites of carbon quantum dots. According to Raman spectroscopy, as well as transmission electron microscopy and atomic force microscopy analysis, graphene sheets consist of several layers.

Raman spectroscopy of graphene nanoribbons synthesized by longitudinal unzipping of multiwall carbon nanotubes

Graphene nanoribbons (GNRs) were synthesized by longitudinal unzipping of multiwall carbon nanotubes (MWCNTs), and changes in Raman spectra were followed. Transmission electron microscopy was used to investigate the longitudinal opening of carbon nanotubes. Height and height profiles of GNRs are observed by atomic force microscopy. Considering that GNRs are carbon-based material, we conducted a detailed Raman spectroscopy study of this new material. Raman measurements were performed at three different laser excitational lines: 532, 633 and 785 nm. We noticed a considerable increase in the ratio between D and G bands compared to the same parameter for MWCNTs. The contribution of the edge structure is much higher in GNRs than in the structure of pristine MWCNTs, which is a main reason for the high increase in structural disorder. It was also noticed that the intensity of the 2D band was significantly lower compared to the same band in the Raman spectra of pristine MWCNTs.

Raman spectroscopy study of carbon-doped resorcinol-formaldehyde thin films

In this work, we investigated the properties of carbon resorcinol-formaldehyde (RF) cryogel thin films. RF cryogels were doped by single-wall carbon nanotubes, graphene and graphene quantum dots. The structure of the deposited films was investigated by Raman spectroscopy, and optical, transmission electron and atomic force microscopy. Raman spectroscopy was performed using three excitation laser energies in the visible range. The effect of glass substrate on the Raman features of investigated carbon cryogel thin films was determined as well. The particle size of the carbon-doped RF cryogel thin films was determined by atomic force microscopy.

Ambient light induced antibacterial action of curcumin/graphene nanomesh hybrids

Curcumin and its derivates are well-known for their different biological activities including antibacterial. On the other hand there are controversial reports concerning the antibacterial potential of graphene and, in particular, graphene oxide. In this study we have reported for the first time the antibacterial activity of curcumin/graphene nanomesh hybrids under ambient light conditions. The graphene nanomesh was synthesized by electrochemical exfoliation of highly oriented pyrolytic graphite in 1 M solution of ammonium persulfate and further functionalized by curcumin. Identical values of minimum inhibitory concentration (1 mg mL−1) were determined for pure curcumin and curcumin/graphene nanomesh hybrids toward Staphylococcus aureus. All tested samples had more pronounced antibacterial activity against Gram positive bacteria, Staphylococcus aureus compared to Escherichia coli as a representative of Gram negative strains. The poor antibacterial potential of exfoliated graphene improves significantly by the functionalization with curcumin, which allows for its usage as a antibacterial coating.

Surface modification of single-wall carbon nanotube thin films irradiated by microwaves: a Raman spectroscopy study

In this work, we present the results of a Raman spectroscopy study of single-wall carbon nanotube (SWCNT) thin films treated with microwave irradiation. SWCNT thin films were deposited by the vacuum filtration method and transferred onto alumina substrate. These thin films were exposed to microwave irradiation of 25 and 250 W at 2.45 GHz. All samples were characterized by Raman spectroscopy and atomic force microscopy. Raman spectroscopy analysis showed that there was neither selective destruction of metallic nor semiconducting nanotubes. It was noticed that samples were heated only during microwave irradiation at 250 W. The major effect of microwave irradiation on SWCNTs was their debundling.