Valeriy A. Skryshevsky

Influence of the interfacial chemical environment on the luminescence of 3CSiC nanoparticles

Surface chemistry of as-prepared 3Cue5f8SiC nanoparticles obtained by electrochemical etching of bulk 3Cue5f8SiC substrates was studied. Chemical environment was found to influence strongly the photoinduced electronic transitions in the 3Cue5f8SiC nanoparticles. The influence of different interfacial chemical environments of the 3Cue5f8SiC nanoparticles, such as surface chemistry, solvent nature, and surface charges on the photoinduced absorption and luminescence of the nanoparticles at room temperature, is described and discussed in detail. For example, oxidation induced passivation of the radiative band gap states allows visualization of the transitions between energy levels in the nanoparticles in which photogenerated charge carriers are quantumly confined. Electrostatic screening of the radiative band gap states by highly polar solvent media leads to a blueshift and a decrease in the width at half maximum of the photoluminescence spectra of the nanoparticles. As for the surface charges, they govern band bending slope...

Enzyme biosensor systems based on porous silicon photoluminescence for detection of glucose, urea and heavy metals

A phenomenon of changes in photoluminescence of porous silicon at variations in medium pH is proposed to be used as a basis for the biosensor system development. The method of conversion of a biochemical signal into an optical one is applied for direct determination of glucose and urea as well as for inhibitory analysis of heavy metal ions. Changes in the quantum yield of porous silicon photoluminescence occur at varying pH of the tested solution due to the enzyme-substrate reaction. When creating the biosensor systems, the enzymes urease and glucose oxidase (GOD) were used as a bioselective material; their optimal concentrations were experimentally determined. It was shown that the photoluminescence intensity of porous silicon increased by 1.7 times when increasing glucose concentration in the GOD-containing reaction medium from 0 to 3.0mM, and decreased by 1.45 times at the same increase in the urea concentration in the urease-containing reaction medium. The calibration curves of dependence of the biosensor system responses on the substrate concentrations are presented. It is shown that the presence of heavy metal ions (Cu(2+), Pb(2+), and Cd(2+)) in the tested solution causes an inhibition of the enzymatic reactions catalyzed by glucose oxidase and urease, which results in a restoration of the photoluminescence quantum yield of porous silicon. It is proposed to use this effect for the inhibitory analysis of heavy metal ions.

Photoluminescence properties of silica aerogel/porous silicon nanocomposites

The luminescent properties of nanocomposite pellets based on silica aerogel and porous Si powder are studied depending on the ratio of chemical compounds. The photoluminescence of nanocomposites is characterized by a red–orange band related to silicon nanoparticles and a blue–green band related to silica aerogel with close values of decay time and activation energy. Remarkable tuning of nanocomposites photoluminescence spectra in the RGB region is established allowing their use as promising phosphor materials for light-emitting diodes. The outgoing spectra of pellet photoluminescence are guided by the chemical composition ratio, porous Si and silica aerogel technology, and the storage time in ambient atmosphere. It was shown that using the silica aerogel as a dielectric matrix considerably increases the stability of photoluminescence yield of silicon nanoparticles.

Monitoring of melamine contamination in fat watery milk by the photoluminescence analysis.

A photoluminescence method to detect the toxic melamine contamination in fat watery milk has been proposed. Despite the quite different luminescence origins of milk and melamine patterns, their wide emission spectra under UV excitation are similar and in the range of 2.2-3.5 eV. The complex milk photoluminescence spectrum composed of riboflavin, furosine, lactulose, Vitamin E and tryptophan emitting species can be modified if milk pattern is undergone by acid treatment (for example, in vinegar). At the same time the melamine emission is not subjected to any modification in vinegar. It allows quantitatively discriminating the melamine contamination in milk in linear range, at least, 0.05-7 g/l from different photoluminescence spectra of milk (water) with and without melamine. Limit of melamine detection achieves 0.01 g/l.

Might Silicon Surface Be Used for Electronic Tongue Application

An electronic tongue concept based on 2D mapping of photogenerated charge carrier lifetimes in silicon put in contact with different liquids is reported. Such method based on intrinsic sensitivity of the silicon surface states to the surrounding studied liquids allows creation of their characteristic electronic fingerprints. To increase recognition reliability, a set of characteristic fingerprints for a given liquid/silicon interface is proposed to be recorded at different bias voltages. The applicative potential of our sensing concept was demonstrated for different spirits and water samples.

Size tuning of luminescent silicon nanoparticles with meso-porous silicon membranes

Size tuning of silicon (Si) nanoparticles (NPs) with the use of meso-porous silicon (meso-PS) free-standing layers is reported for the first time. Accumulation of Si NPs inside the membrane pores during the filtering process (NP transport through the meso-PS) leads to an auto-filtration effect (called Si-by-Si (SBS) filtration) allowing more efficient size selection of the NPs. General complex fractal shape and surface chemistry of the whole porous network, layer thickness as well as a given initial NP size dispersion determine final size of the NPs in the filtered solution. Moreover, quantum of step-like NP size increasing equal to 0.12 nm was found.

Delivery of SiC-based nanoparticles into live cells driven by cell-penetrating peptides SAP and SAP-E

The delivery of SiC-based nanoparticles (SiC-NPs) into living eukaryotic cells is facilitated in the presence of cell-penetrating peptides, both cationic (SAP) and anionic (SAP-E). The SiC-NP surface functional group modification combined with rational CPP selection introduces an additional mode of delivery control.

Trypsinization-dependent cell labeling with fluorescent nanoparticles.

Trypsin is often used to detach adhered cell subculture from a substrate. However, the proteolytic activity of trypsin may harm cells by cleaving the cell membrane proteins. The present study shows that cellular uptake of fluorescent nanoparticles is remarkably increased within 24xa0h after trypsinization. These results highlight the trypsin-induced protein digestion, provoking leaky cell plasma membrane which leads to the strongly enhanced cellular uptake of the nanoparticles. To prevent this effect, one should expose cells to the nanoparticle (NP)-based fluorescent labels at least 48xa0h after trypsinization.

Optical Addressing Electronic Tongue Based on Low Selective Photovoltaic Transducer with Nanoporous Silicon Layer

The electronic tongue based on the array of low selective photovoltaic (PV) sensors and principal component analysis is proposed for detection of various alcohol solutions. A sensor array is created at the forming of p-n junction on silicon wafer with porous silicon layer on the opposite side. A dynamical set of sensors is formed due to the inhomogeneous distribution of the surface recombination rate at this porous silicon side. The sensitive to molecular adsorption photocurrent is induced at the scanning of this side by laser beam. Water, ethanol, iso-propanol, and their mixtures were selected for testing. It is shown that the use of the random dispersion of surface recombination rates on different spots of the rear side of p-n junction and principal component analysis of PV signals allows identifying mentioned liquid substances and their mixtures.

Memristor Effect in Sandwich-Type Ni-TiOx-p/Si-Ni Heterojunction

I-V, C-V characteristics and current change kinetics of the Ni-TiOx-p/Si-Ni heterojunction were studied under different speeds of voltage sweep, in darkness and under illumination of various spectral regions. It was found that Ni-TiOx-p/Si-Ni heterojunction shows pronounced hysteretic behavior and can act as memristor cell. Results of studies of photosensitivity and current kinetics under abrupt changes of applied voltage and illumination reveal considerable role of surface states recharging in TiOx oxide layer or at TiOx-p/Si interface in the switching effects.The studied Ni-TiOx-p/Si-Ni heterostructure is prospective as a basis for low-cost, CMOS- and SOI-compatible microelectronic devices with non-volatile memory.