B. A. Snopok

Theory and Practical Application of Surface Plasmon Resonance for Analytical Purposes

On the basis of an analysis of current views about plasmonics a conceptual examination of propagating surface plasmon resonance (SPR) in relation to the basic mechanisms and operating forces was undertaken with the aim of defining the characteristics of SPR transducers for analytical applications. A simple model of a sensor system that makes it possible to relate the analytical requirements to the intrinsic physical or mechanical characteristics of SPR is examined. A brief review of modern developments is presented.

Nonexponential Kinetics of Surface Chemical Reactions

On the basis of current trends in the description of adsorption processes in complex media a conceptual analysis was made of the mechanisms of the appearance of nonexponential kinetics (stretched exponential function) in chemical reactions on a surface. A review of approaches ranging from a phenomenological description to a generalized fractal formalism is presented, and it was used to develop a model of adsorption in nonuniform media in terms of the concepts of the reaction space as a topological subject. By “geometric description” of the evolution of the surface reactions it is possible to unify the various types of effect in terms of a reaction space of required dimensionality and to establish a relationship between the parameters of macroscopic kinetics and features of the trajectory of the analyte in the nonuniform environment during its movement toward the receptor center.

Generation of diversiform gold nanostructures inspired by honey's components: growth mechanism, characterization, and shape separation by the centrifugation-assisted sedimentation.

The green synthesis of irregular-shaped nanomaterials used for various applications in nanoplasmonics, medicine, and biotechnology creates an economical and environmental challenge. We describe the rapid wet-chemical approach to synthesis of stable and water-soluble gold nanostructues at room temperature. In addition to spherical and road-like nanoparticles, gold decahedra and triangular plates were grown using the one-step synthesis process of HAuCl(4) in the presence of honey, in which main components act as reducing (glucose) and stabilizing (fructose) agents; the mechanism of the process is discussed in details. The requirements for anisotropic phase boundaries for generation of polyhedral gold nanocrystals in solutions are highlighted. The synthesis, morphology, and separation procedure of gold nanoparticles are examined using the techniques of optical spectroscopy, transmission electron microscopy, and atomic force microscopy. We demonstrate that centrifugation can be used for efficient separation of nanoparticles with different shapes from a mixture. It was found that while centrifuging, the spheres sediment at the bottom of the tube, segregating from rods that form a deposit on the side wall, whereas polygons remain in the solution.

Effect of Al3+ Additions on the Microstructure and Photoluminescence of SrTiO3:Pr3+ Phosphors Produced by the Sol–Gel Method

The effect of various concentrations of Pr3+ on the structural and luminescent characteristics of SrTiO3:Pr3+ phosphors synthesized by the sol–gel method was investigated. Maximum intensity of red luminescence (617 nm) for SrTiO3:Pr3+ with excitation by ultraviolet radiation is observed at an effective Pr3+ concentration of 0.2 mole %. It was shown that the addition of aluminum at the optimum Pr3+ concentration leads to deterioration of the crystallinity and reduces brightness of the SrTiO3:Pr3+ luminescence. The reason for the last effect may be the presence of minute amounts of iron impurity in the initial reagents.

Confocal Raman Spectroscopy of Biological Objects under Conditions of Photoinduced Luminescence Self-Quenching

A study was carried out on the mechanism of luminescence self-quenching of heterogeneous biological objects using laser irradiation at 532 nm (50 μW/ μm2) in the format of a confocal microscope. Laser irradiation was found to reduce the luminescence intensity of material by a factor of 3–5, which permits us to obtain informative Raman scattering spectra of the dried cellular envelope of yeast. For irradiation times less than ~3-5 min, quenching is probably due either to formation of radiationless complexes of the excited chromophore molecules with the environment (excimers and/or exciplexes) or partial photodecomposition. Longer irradiation times lead to thermal degradation of the samples with the appearance of peaks corresponding to amorphous carbon.

Features of Cooperative Adsorption Described by Sticking Probability that Depends on the Number of Neighbors

The kinetic curves and monolayer clusters on a flat surface for cooperative adsorption, where the probability of sticking of the particles depends on the amount of neighbors on the surface, were calculated by nonequilibrium molecular dynamics. It was found that the type of distribution of the sticking coefficients has a large effect both on the dynamic and on the structural characteristics of the adsorption process. It is shown that the most informative algorithm for classifying the adsorption type is based on the dependence of the fractal dimensionality of the surface structure on the degree of surface coverage.

Effect of the Formation of Silicon Oxide on the Sign, Magnitude and Formation of Surface Charge Upon Water Adsorption on a Silicon Surface

The adsorption of water vapor on the Si(100) surface was found to proceed with formation of a charged form of an adsorption complex using the transverse acoustoelectric effect in the layered piezodielectric/air-gap/semiconductor structure. The sign of the localized surface charge is a function of the formation of silicon oxide and changes from positive to negative in going from the crystalline silicon(100) surface to the oxide-coated surface. Discrete states of the surface charge were observed.

New High-Efficiency Red-Emitting Phosphor Produced by the Sol–Gel Method

The sol–gel method was used to obtain high-brightness crystal phosphors from SrTiO3: Pr3+ producing more than 1800 cd/m2. A ten-fold increase in the intensity of the main luminescence spectrum band at λ = 617 nm by doping SrTiO3: Pr3+ was achieved by adding a ferric ion coactivator (5 · 10–5 mole %). The results indicated a possible mechanism for the enhancement of the Pr3+ ion luminescence in the presence of the coactivator.

Reproducibility and Uniqueness of Information Coding as Key Factors For Array Optimization

An approach for the evaluation of sensor array efficiency is proposed. The reproducibility of sensor responses and the uniqueness of chemical images (CI) formed by the array are considered as dominant factors that determine sensor array functionality. The key feature of the method is representation of array response as a numerical function of sensors responses. This allow making mathematical operations with CI. The dispersion of CIs of given set of analytes can serve as a measure of their uniqueness. The coefficient of covariance in the set of measurements expresses their reproducibility. The rate of influence of both reproducibility and CI uniqueness on the discriminating ability is shown qualitatively on the example of three QCM sensor array with metal phthalocyanines sensitive coatings. The illumination of sensors surfaces in the Q‐band region of Pc’s adsorption spectra was applied as a factor affecting both the reproducibility and the uniqueness of CIs.

SPR Study of the Blocking Activity of Soybean Trypsin Inhibitor by Macrocyclic Complexes of Nickel Immobilized on a Gold Surface

A method is proposed for the modification of metallic gold surfaces by self-organization of a nickel(II) macrocyclic complex containing a thiol substituent. Effective blocking of biologically active soybean trypsin inhibitor by the immobilized complex was observed. The prospects of using the given surface to create sensitive elements for sensors capable of detecting both small molecules (thiocyanate ions) and some protein substrates is demonstrated.