Andrzej Olszyna

Recent advances in graphene family materials toxicity investigations

Recently, graphene family materials (GFMs) have been introduced among all fields of science and still get numerous attention. Also, the applicability of these materials in many areas makes them very attractive. GFMs have attracted both academic and industrial interest as they can produce a dramatic improvement in materials properties at very low filler content. This article presents recent findings on GFMs toxicity properties based on the most current literature. This article studies the effects of GFMs on bacteria, mammalian cells, animals, and plants. This article also reviews in vitro and in vivo test results as well as potential anticancer activity and toxicity mechanisms of GFMs. The effect of functionalization of graphene on pacifying its strong interactions with cells and associated toxic effects was also analyzed. The authors of the article believe that further work should focus on in vitro and in vivo studies on possible interactions between GFMs and different living systems. Further research should also focus on decreasing GFMs toxicity, which still poses a great challenge for in vivo biomedical applications. Consequently, the potential impact of graphene and its derivatives on humans and environmental health is a matter of academic interest. However, potential hazards sufficient for risk assessment first need to be investigated.

Molecular structure of E-BN

Abstract E-BN layers were deposited on non-heated CaF2 and Si substrates using the method of electrostatic acceleration of h-BN powder in a high-voltage cascade accelerator. The phase compositions of the layers were examined by the XRD method — the values of d obtained were similar to those reported by Batzanov et al. [1]. IR examinations were conducted within the range 400–4000 cm−1. The molecular structure of E-BN was modelled using a computer simulation (with the Hyper-Chem computer program) based on the results obtained. The model thus obtained differs from those known earlier for h-BN, w-BN and c-BN.

The ecotoxicity of graphene family materials: current status, knowledge gaps and future needs

Recently, graphene family materials (GFMs) have been introduced among all fields of science and still get numerous attention. Also, the applicability of these materials in many areas makes them very attractive. GFMs have attracted both academic and industrial interest as they can produce a dramatic improvement in materials properties at very low filler content. The aim of this review is to identify, summarize, and present the first available information on the influence of GFMs on soil and water environment as well as identify the knowledge gaps and indicate the directions for the next generation of the original scientific investigations. The paper also presents our first preliminary impact assessment and potential pathways of GFMs distribution in the environment. We used as an example the reduced graphene oxide/Al2O3 nanocomposite (RGO/Al2O3) that has been previously designed and synthesized by us. Authors believe that further work should focus on improvement of characterization methodology applicable for ecotoxicity analyses and possible interactions between GFMs and different living ecosystems. Consequently, the potential impact of graphene and its derivatives on environmental health is a matter of academic interest. However, potential hazards sufficient for risk assessment and concerned with GFMs usage in consumer products first need to be investigated and identified. Further research should focus on gathering knowledge on GFMs properties for life cycle analyses, which still poses a great challenge for scientists.

In vitro assessment of antibacterial properties and cytotoxicity of Al2O3–Ag nanopowders

Abstract Abstract The present paper describes an in vitro assessment of the antibacterial properties and cytotoxic activity on mammalian cells of silver nanoparticles incorporated into an aluminium nano-oxide substrate produced by the thermal decomposition–reduction method. The Al2O3–Ag nanopowders show good bactericidal and fungicidal properties. An Al2O3–Ag (12·55 wt-%) specimen at the concentration of 50 mg mL−1 reduced considerably the populations of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis species, whereas the same nanopowder in a concentration of 90 mg mL−1 inhibited significantly the growth of P. aeruginosa, E. coli, S. aureus and Candida albicans and also significantly limited the number of B. subtilis. The Al2O3–Ag nanoparticles also showed no cytotoxic effects on the three selected cell lines, i.e. L929, BJ and HeLa, and the cells remained >75% viability, as measured by MTT assay, and >102% viability, obtained by EZ4U assay, relative to control at concentration as high as 200 μg mL−1.

Al2O3–Ag nanopowders: new method of synthesis, characterisation and biocidal activity

Abstract Abstract The present paper describes an innovative method of producing silver nanoparticles incorporated into an aluminium nano‐oxide substrate. The method utilises thermal decomposition and reduction, which yields an Al2O3–Ag nanopowder with the average size of particles ranging from 43 to 60 nm and the average size of agglomerates between 330 and 870 nm. The average size of the silver nanoparticles incorporated in the aluminium nano‐oxide carrier ranges from 22 to 60 nm. The Al2O3–Ag nanopowders thus produced have a largely developed surface area (above 200 m2 g−1) with a great number of open pores (above 5×10−4 m3 g−1), which gives evidence that their tendency to agglomeration is only slight and that the possible agglomerates have a loose structure. Moreover, the nanopowders show good bactericidal and fungicidal properties. The results obtained in the present experiments show that the Al2O3–Ag nanopowders produced by the proposed method can be used successfully as the raw material in the production of biocidal biomaterials.

Diamond layers deposited from impulse plasma

Abstract Layers were deposited onto unheated substrates, from C + and C 2+ plasmoids emitted by a coaxial accelerator. X-ray and electron diffraction investigations revealed short-range ordering of σ sp 3 type. The value of the band gap E g of 3.8 eV, the small amount of C-H bonding, the high electrical resistivity, and refractive index n in the range 2–2.46 confirmed the diamond content of the layer. The layers were brittle and their hardness did not exceed 1000 HV. Pulse plasma deposited diamond layers can find applications as surface coatings of anti-abrasive TiN-C composites and passivating layers in semiconductor structures.

Si3N4–Al2O3–TiC–Y2O3 composites intended for the edges of cutting tools

Abstract This paper is concerned with the synthesis of composites in the Si 3 N 4 –Al 2 O 3 –TiC–Y 2 O 3 system. The materials obtained have a high density and a good fracture toughness (K IC =9.3 MPa√m). Machining tests show that the service life of the tool blades made of these composites may even be tenfold longer than that of commercial blades made of Si 3 N 4 with an additon of Al 2 O 3 , MgO and Y 2 O 3 .

Morphology, structure, and photoactivity of two types of graphene oxide-TiO2 composites

Two types of graphene oxide-TiO2 composites were prepared: one by including graphene oxide flakes in the TiO2 sol, followed by thermal treatment (GI composite) at 300°C, and the second by including graphene oxide flakes in the calcined (at 500°C) TiO2 xerogel (GII composite). The composites were characterized by SEM, TEM-EDS, TEM-SADP, STEM-HAADF, HRTEM coupled with FT, XRD, and XPS. Photocatalysis results were fitted to different kinetic models (pseudo-first and pseudo-second kinetics, intraparticle Weber-Morris diffusion, film diffusion, and external mass transfer). The results showed that by introducing graphene oxide flakes in the TiO2 sol, followed by thermal treatment at 300°C (GI composite), an efficient graphene oxide-TiO2 catalyst with high specific surface area, heterogeneity, and many graphitized areas can be obtained. Complete crystallization of the composite is not the key issue for the best photoactivity achievement. The rate limiting step in the photocatalytic process is the photooxidation of SA molecules on the TiO2 surface.

Electrical behaviour and breakdown in plasma deposited cubic BN layers

Abstract The paper presents results of an investigation of the electrical properties of cubic boron nitride (c-BN) layers deposited onto silicon substrates by the reactive pulse plasma method. Current-voltage characteristics of the layers in metal/insulator/semiconductor (MIS) structures were investigated in a wide voltage range for films of various thicknesses, obtained under different technological conditions. On the basis of I-V measurements, the breakdown properties of BN layers were also evaluated. In spite of many similarities of c-BN films to diamond-like carbon films, we have found a slightly different character of electrical properties. In most cases we observed switching phenomena and voltage-controlled negative resistance. The dielectric strength of investigated layers shows a wide range of critical electric fields in the range 0.5–6.0 MV cm −1 . An attempt to explain the observed effects on the basis of existing models, valid for similar materials, is also made.

Electron assisted chemical synthesis of E-BN

The electron assisted chemical synthesis of BN in a flux was examined. It has been found that the metastable E-BN phase crystallizes besides the stable h-BN phase. The relative content of E-BN depends on the quantity of electrons.