Oleg Viktorovich Salata

Applications of nanoparticles in biology and medicine

Nanomaterials are at the leading edge of the rapidly developing field of nanotechnology. Their unique size-dependent properties make these materials superior and indispensable in many areas of human activity. This brief review tries to summarise the most recent developments in the field of applied nanomaterials, in particular their application in biology and medicine, and discusses their commercialisation prospects.

Nanoparticles – known and unknown health risks

Manmade nanoparticles range from the well-established multi-ton production of carbon black and fumed silica for applications in plastic fillers and car tyres to microgram quantities of fluorescent quantum dots used as markers in biological imaging. As nano-sciences are experiencing massive investment worldwide, there will be a further rise in consumer products relying on nanotechnology. While benefits of nanotechnology are widely publicised, the discussion of the potential effects of their widespread use in the consumer and industrial products are just beginning to emerge. This review provides comprehensive analysis of data available on health effects of nanomaterials.

Green phosphorescent dendrimer for light-emitting diodes

Highly efficient organic LEDs made by solution processing are reported. It is shown that the dendritic architecture (see Figure) can be used to solubilize luminescent chromophores and form uniform films of blends. The simple device structures containing a light-emitting chromophore are amongst the most efficient solution-processed devices reported. Thanks to this technique, the inkjet printing of phosphorescent materials becomes feasible.

High resolution x-ray photoemission study of plasma oxidation of indium–tin–oxide thin film surfaces

The influence of plasma oxidation and other surface pretreatments on the electronic structure of indium–tin–oxide (ITO) thin films has been studied by high resolution x-ray photoemission spectroscopy. Plasma oxidation compensates n-type doping in the near surface region and leads to a reduction in the energy of plasmon satellite structure observed in In 3d core level spectra. In parallel, the Fermi level moves down within the conduction band, leading to a shift to low binding energy for both core and valence band photoemission features; and the work function increases by a value that corresponds roughly to the core and valence band binding energy shifts. These observations suggest that the conduction band of ITO is fixed relative to the vacuum level and that changes of work function are dominated by shifts of the Fermi level within the conduction band.

Uniform GaAs quantum dots in a polymer matrix

A novel technique suitable for the preparation of uniformly sized nano‐ and microparticles of a wide range of compound semiconductors embedded in different polymers is described. Optical absorption spectra and high resolution electron micrographs of a new composite material—GaAs quantum dots in a polymer matrix—are presented and are discussed.

New molecular lanthanide materials for organic electroluminescent devices

Organic electroluminescent (EL) devices based upon the new lanthanide EL material Tb[Ph2P(O)NP(O)Ph2]3 (Tbpip3) are described. Several device structures are reported and the effect of charge transporting material and layer thickness on device performance critically assessed. Device performance is optimised in a three-layer structure containing TPD and Alq as the charge transport layers. This device has an efficiency of 0.7 cd A−1 at 20 cd m−2 at 25 V and 1 mA cm−2.

A low reflectivity multilayer cathode for organic light-emitting diodes

In this paper, a vacuum-deposited multilayer cathode for organic light-emitting diodes (OLEDs) with reduced reflectivity is described. The reduced reflectivity (58% at 550 nm) is due to the addition of a smooth and compact carbon film between a thin semi-transparent magnesium layer and the top aluminum contact. For the following light-emitting organic structure deposited on indium-tin-oxide substrates: N,N′-diphenyl-N,N′-bis-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD)/terbium tris(1-phenyl-3-methyl-4-(tertiarybutyryl)pyrazol-5-one) triphenylphosphine oxide [(tb-PMP)3Tb(Ph3PO)]/3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), the injection properties of such a multilayer cathode are presented and compared to those of Al/Mg and C/Al cathodes. Such a cathode shows promise for contrast improvements in OLEDs.

Comparison of models of electroluminescence in organic double-layer light-emitting diodes

A theoretical model of leakage and barrier-limited recombination of charge carriers at the interface separating two disordered organic materials in organic light-emitting diodes is formulated. Spatial disorder of molecular materials is reflected in the model by differentiating the hopping distances associated with jumps leading to recombination from those leading to leakage. The former and the latter are determined by the mean intersite distance and by the shortest hopping distance, respectively. It is shown that the effect of the difference between the two hopping distances on the current and recombination efficiencies depends on a barrier height and electric field strength at the organic–organic interface. The results of the models with barrier-limited recombination and Langevin recombination are compared. It is shown that both models yield comparable results for the steady-state recombination efficiency and current, if at least one of the interfacial energy barriers is small enough and the leakage is m...

Preparation of nanoparticulate CdS films suitable for opto-electronic device applications

Abstract A simple route for preparation of aqueous colloidal solutions of cadmium sulfide nanoparticles with a narrow size distribution, showing a quantum confinement effect (Q-CdS), is described. A combination of the widely-used spin/dip coating techniques was utilised to deposit high optical quality Q-CdS films on indium tin oxide glass; film thickness can be varied from 50 to 200 nm. The results of optical and structural characterisation of the Q-CdS films with photoluminescence, light absorption and high resolution electron microscopy are presented and discussed.

Highly efficient solution-processible phosphorescent dendrimers for organic light-emitting diodes

Currently, most research into organic light-emitting diodes (OLEDs) has focused on two main classes of materials: small organic molecules and conjugated polymers. An alternative approach is to use conjugated dendrimers. We show that conjugated dendrimers are a promising new class of solution-processible materials for use as the active layer in highly efficient organic LEDs. By optimizing the choice of device structure, host material, and electron transport layer, we can obtain efficiencies of 55 cd/A and power efficiencies of 40 lm/W. This is an excellent result for a spin-coated emissive layer.