A. Sokołowska

Visualization of interaction between inorganic nanoparticles and bacteria or fungi

Purpose The objective of the present investigation was to evaluate the morphologic characteristics of self-assemblies of diamond (nano-D), silver (nano-Ag), gold (nano-Au), and platinum (nano-Pt) nanoparticles with Staphylococcus aureus (bacteria) and Candida albicans (fungi), to determine the possibility of constructing microorganism–nanoparticle vehicles. Methods Hydrocolloids of individual nanoparticles were added to suspensions of S. aureus and C. albicans. Immediately after mixing, the samples were inspected by transmission electron microscopy. Results Visualization of the morphologic interaction between the nanoparticles and microorganisms showed that nano-D, which are dielectrics and exhibit a positive zeta potential, were very different from the membrane potentials of microorganisms, and uniformly surrounded the microorganisms, without causing visible damage and destruction of cells. All metal nanoparticles with negative zeta potential had cell damaging properties. Nano-Ag showed the properties of self-organization with the cells, disintegrating the cell walls and cytoplasmic membranes, and releasing a substance (probably cytoplasm) outside the cell. Arrangement of nano-Au with microorganisms did not create a system of self-organization, but instead a “noncontact” interaction between the nanoparticles and microorganisms was observed to cause damage to fungal cells. Nano-Pt caused both microorganisms to release a substance outside the cell and disintegrated the cytoplasmic membrane and cell wall. Conclusion Nano-Ag, nano-Au, and nano-Pt (all metal nanoparticles) are harmful to bacteria and fungi. In contrast, nano-D bind closely to the surface of microorganisms without causing visible damage to cells, and demonstrating good self-assembling ability. The results indicate that both microorganisms could be used as potential carriers for nano-D.

Reactive pulse plasma crystallization of diamond and diamond-like carbon

Abstract Thin layers of tetrahedral carbon phases (diamond, lonsdaleite etc.) were crystallized under reduced pressure (10 -3 / Pa) using a coaxial plasma generator. On the basis of comparison of known diamond crystallization processes under reduced pressure it was assumed that the electric charge plays an important part in the nucleation process.

Diamond-like carbon coatings for biomedical applications

Abstract The results of experimental studies on amorphous diamond carbon layers obtained by a new method of r.f. dense plasma chemical vapour deposition onto orthopaedic pins and screws are presented. Research on this subject which has been carried out over many years allows us to draw optimistic conclusions concerning the biomedical applications of diamond-like carbon (DLC). In particular, preliminary medical research on a new DLC-steel substrate system developed in 1992, which has just been concluded, is extremely promising.

The deposition of thin films of materials with high melting points on substrates at room temperature using the pulse plasma method

Abstract The pulse plasma method was used to deposit thin films of diamond, borazone, Al 2 O 3 , Ta 2 O 5 and other materials. The main advantage of this method is the possibility that films with good adhesion to the substrate can be prepared under low temperatures and at pressures attainable with a rotary pump. Films of diamond, which are very hard, may have applications as hard coatings and in electronic devices. The main disadvantage of this method in its present stage of development is that the purity of the films produced is insufficient for their application as semiconductors in electronic devices.

The “in-flame-reaction” method for Al2O3 aerosol formation

In this paper a study was made of the conditions of formation and properties of Al2O3 aerosol obtained by oxidation of aluminium acetylacetonate ultrasonically sprayed into a hydrocarbon-oxygen flame. Spherical particles with diameters as small as 30 A were obtained at sprayer frequency ν = 1 MHz as a result of rapid combustion. Temperature measurements and investigation of the flame emission spectrum as well as of the shape and size of particles suggest that liquid Al2O3 droplets are formed from the gaseous phase next to be crystallized from the liquid phase. Comparison of the results concerning Al2O3 formation in H2 + O2 flame and in the hydrocarbon-oxygen flame leads to the suggestion that the γ-Al2O3 phase is formed if synthesis and crystallization occurs in the presence of the H2O and/or OH and the liquid particles are rapidly cooled. The following scheme of the aerosol formation mechanism is proposed: [Al2O3]L. OHads denotes Al2O3 particle with chemisorbed OH.

Electric charge influence on the metastable phase nucleation

Abstract On the basis of existing crystallization theories, diamond should not be formed under conditions of its thermodynamic instability. The growth of this material at reduced pressure and low temperature can be explained by the influence of electric energy on the nucleation process which, according to A.J. Rusanov, makes the formation of extremely small, stable crystals possible. The pressure caused by the surface tension will then be so great that the diamond is thermodynamically stable.

Properties and growth of β-BN (borazon) layers from a pulsed plasma under reduced pressure

Thin fine-grained layers of diamond-like β-BN were crystallized under reduced pressure using a coaxial plasma generator. They exhibited n-type conductivity, electric resistivity of 1013 ω m, and improved performance when used in an MIS structure.

The structure and mechanical properties of carbon layers formed by crystallization from pulse plasma

The structure of amorphous carbon layers thicker than 10 µm, obtained from a pulse plasma has been studied. Their hardness, friction coefficient and response to the action of a uniaxial force were determined. The conclusions from X-ray diffraction data, especially from the atomic radial distribution, from annealing experiments and from investigation of the mechanical properties are complementary to one another.

Application of diamond-like layers as gate dielectric in metal/insulator/semiconductor transistor

Abstract In this work the application of diamond-like carbon (DLC) layers formed by r.f. plasma-enhanced chemical vapour deposition (PECVD) as the dielectric layer in a metal/insulator/semiconductor (MIS) transistor (MISFET) is presented. In the course of this work the technology has been developed, enabling the manufacture of MIS transistors with DLC layers as gate insulator. The r.f. PECVD method was used for the formation of DLC layers. The transistors, with channel sizes ranging from 10 × 10 μm 2 to 200 × 200 μm 2 , were manufactured in a microelectronics standard technological laboratory. Selective etching of source and drain contact holes was performed by a “lift off” technique, which required some modifications to the typical MOSFET fabrication procedure. Auger electron spectroscopy measurements proved the high purity of the gate dielectric DLC films and the penetration of carbon into the silicon substrate. Both the measured electrical characteristics, transient and output, confirmed the transistor action of the manufactured MISFET.

Open-circuit mode drift mobility measurements in DLC films

Abstract In the paper the first results of the open-circuit mode time-of-flight experiment for diamond-like carbon films are presented. The electron drift mobility obtained is of the order of 10−6 cm2 V−1 s−1 at room temperature. This suggests that hopping may be considered as the predominant transport mechanism for diamond-like carbon films prepared by r.f. glow discharge from methane.