M Kh Salakhov

Plasmonic optical antenna design for performing tip-enhanced Raman spectroscopy and microscopy

This paper highlights optical plasmonic antennas designed with dc-pulsed low-voltage electrochemical etching of a gold wire for implementing tip-enhanced Raman scattering (TERS) measurements. We demonstrate a versatile electrochemical system that allows one to engineer TERS-active metallic gold tips with diverse shapes and sizes in a highly reproducible fashion. The underlying etching mechanism at a voltage-driven meniscus around a gold wire immersed into an electrolyte is discussed in detail. We show that the developed method is suitable to produce not only the simplest geometries such as cones and spheroids, but more complex designs. Attempts have been made to design plasmonic tapered antennas with quasi-uniformly spaced nano-sized bumps on the mesoscopic zone for the extra surface plasmon-light coupling. The capability of the patterned antenna to enhance and localize optical fields is demonstrated with near-field Raman microscopy and spectroscopy of single-walled carbon nanotubes bundles.

Pb3+ radiation defects in Ca9Pb(PO4)6(OH)2 hydroxyapatite nanoparticles studied by high-field (W-band) EPR and ENDOR

W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca(9)Pb(PO(4))(6)(OH)(2) are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure.

Electron spin resonance detection and identification of nitrogen centers in nanodiamonds

Individual nitrogen centers N0 and nitrogen pairs N2+ have been detected and identified in natural diamond nanocrystals by means of the high-frequency electron spin resonance method. The N0 nitrogen centers have been observed in synthetic diamond nanocrystallites with a size of less than 10 nm produced by high-temperature high-pressure sintering of detonation nanodiamonds. Thus, the possibility of the stable state of impurity nitrogen atoms in diamond nanoparticles has been demonstrated.

Stationary and high-frequency pulsed electron paramagnetic resonance of a calcified atherosclerotic plaque

New possibilities of applying high-frequency electron paramagnetic resonance in medicine are demonstrated on an example of the investigation of a calcified atherosclerotic plaque. After the irradiation of the atherosclerotic plaque by x rays, a new type of paramagnetic centers—organomineral radicals—is detected. The spectral and relaxation characteristics of these radicals depend on the calcification degree of the atherosclerotic plaque and can be used for diagnostics.

Perspective of zero-field ODMR to study nano-biological systems

This work presents an introduction, a short literature review as well as our recent optical and high field magnetic resonance experiments with regard to the applications of nitrogen paramagnetic defects in (nano)diamonds for biomedical related research. The perspectives of combination of optical and magnetic resonance (high field electron paramagnetic resonance) spectroscopic methods for the sensitive spatially resolved screening of electrical and magnetic gradients in biological tissues on the nanoscale level are discussed.

Optical contrast of a photonic crystal and the self energy shift of the energy levels of atoms

The influence of a photonic crystal medium on the character of the interaction of electrons with their own radiation field is studied. As was recently shown, this influence changes the electromagnetic mass of the electrons in photonic crystals. This alters atomic energy levels. The dependence of this effect on the optical contrast of photonic crystals is studied.

Manganese in atherogenesis: Detection, origin, and a role

The role of transition metal ions in atherogenesis is controversial; they may be involved in hydroxyl radical generation and can also catalyze the reactive oxygen species neutralization reaction as cofactors of antioxidant enzymes. Using EPR spectroscopy, we revealed that 70% of aorta specimens with atherosclerotic lesions possessed superoxide dismutase activity, 100% of the specimens initiated Fenton reaction and demonstrated the presence of manganese paramagnetic centers. The sodA gene encoding manganese-dependent bacterial superoxide dismutase was not found in the samples of atherosclerotic plaques by PCR using degenerate primers. The data obtained indicate prospects of manganese analysis as a marker element in the express diagnostics of atherosclerosis.

Particle swarm optimization in the problem of decomposing two-component spectral profiles

An approach based on stochastic particle swarm optimization is proposed for the mathematical processing of spectral profiles. It is shown that the proposed approach allows accurate decomposition of complex model spectra and determination of the parameters of spectral components.

Separation of closely located IR Fourier absorption bands using the genetic algorithm

The genetic algorithm was used for analyzing experimental closely located analytical conformation-sensitive IR Fourier absorption bands of low-molecular compounds incorporated into a polymeric matrix. Model experiments demonstrated the efficiency of spectrum reconstruction using the genetic algorithm as compared to the least squares method in the case of closely located components and in the presence of low-frequency noise in the spectrum.

Investigation of atherosclerotic plaque by high-frequency EPR

We present a comparative study of samples of aorta walls from male patients with atherosclerosis and hydroxyapatite powders with the average size of crystallites of 30 nm synthesized by the wet precipitation technique by using 94 GHz pulsed EPR. Origin of the observed paramagnetic centers is discussed. Supported by the electron microscopy and microanalysis, it is shown that EPR spectra from the calcified biological tissues correlates with those obtained in inorganic hydroxyapatites. The hypothesis about the important role of (nano)hydroxyapatite in formation of the mineral deposits and atherosclerotic plaque instability is further sustained.