Modeling of the electronic structure of semiconductor nanoparticles

This paper deals with the mathematical modeling of the electronic structure of semiconductor particles. Mathematically, the task is reduced to a joint solution of the problem of free energy minimization and the set of chemical kinetic equations describing the processes at the surface of a nanoparticle. The numerical modeling of the sensor effect is carried out in two steps. First, the number of charged oxygen atoms on the surface of the nanoparticle (Formula presented.) is determined. This value is found by solving a system of nonlinear algebraic equations, where the unknowns are the stationary points of this system describing the processes on the surface of a nanoparticle. The specific form of such equations is determined by the type of nanoparticles and the mechanism of chemical reactions on the surface. The second step is to calculate the electron density inside the nanoparticle (Formula presented.), which gives the minimum free energy. Mathematically, this second step reduces to solving a boundary value problem for a nonlinear integro-differential equation. The calculation results are compared with experimental data on the sensor effect

Modelling Evaporation And Chemical Reaction In A Multi-Component Droplet From Spray Pyrolysis Synthesis Of Mixed Metal-Oxide Nanocomposite Films

This paper describes the mathematical modelling of transport and chemical reaction phenomena in a single droplet deposited on a heated substrate by spray pyrolysis. The droplet contains mixed salt solutions of tin chloride (SnCl4) and indium nitrate (In(NO3)3) which react on the substrate to produce mixed oxides (In2O3-SnO2) and water residue. The water residue is subsequently evaporated, leaving a thin film of the mixed oxides. The droplet, containing solvent and precursors is modelled using computational fluid dynamics technique. The various stages of droplet morphology associated with surface energy and evaporation are predicted. The transient distribution is also predicted of the concentration of the various species in the droplet. The results show that homogeneous chemical reaction occurs within 60% of the radial distance from the centre. This in turn results in the deposition of metal oxide within that region while a significant amount of unused reactants remains thereafter

Effect of Nanoparticle Interaction on Structural, Conducting and Sensing Properties of Mixed Metal Oxides

This review analyzes the studies published, mainly in the last 10–15 years, on the synthesis, structure, and sensor properties of semiconductor nanocomposites. Particular attention is paid to the interaction between nanoparticles of the sensitive layer, and its effect on the structure, sensitivity, and selectivity of semiconductor sensor systems. Various mechanisms of interaction between nanoparticles in metal oxide composites are considered, including the incorporation of metal ions of one component into the structure of another, heterocontacts between different nanoparticles, and core–shell systems, as well as their influence on the characteristics of gas sensors. The experimental data and studies on the modeling of charge distribution in semiconductor nanoparticles, which determine the conductivity and sensor effect in one- and two-component systems, are also discussed. It is shown that the model which considers the interactions of nanoparticles best describes the experimental results. Some mechanisms of detection selectivity are considered in the conclusion

Synthesis, Structural and Sensor Properties of Nanosized Mixed Oxides Based on In₂O₃ Particles

The paper considers the relationship between the structure and properties of nanostructured conductometric sensors based on binary mixtures of semiconductor oxides designed to detect reducing gases in the environment. The sensor effect in such systems is determined by the chemisorption of molecules on the surface of catalytically active particles and the transfer of chemisorbed products to electron-rich nanoparticles, where these products react with the analyzed gas. In this regard, the role is evaluated of the method of synthesizing the composites, the catalytic activity of metal oxides (CeO2, SnO2, ZnO), and the type of conductivity of metal oxides (Co3O4, ZrO2) in the sensor process. The effect of oxygen vacancies present in the composites on the performance characteristics is also considered. Particular attention is paid to the influence of the synthesis procedure for preparing sensitive layers based on CeO2–In2O3 on the structure of the resulting composites, as well as their conductive and sensor properties

Physico-chemical phenomena in thin films and at solid surfaces.

The book is devoted to the consideration of the different processes taking place in thin films and at surfaces. Since the most important physico-chemical phenomena in such media are accompanied by the rearrangement of an intra- and intermolecular coordinates and consequently a surrounding molecular ensemble, the theory of radiationless multi-vibrational transitions is used for its description. The second part of the book considers the numerous surface phenomena. And in the third part is described the preparation methods and characteristics of different types of thin films. Both experimental and theoretical descriptions are represented. Media rearrangement coupled with the reagent transformation largely determines the absolute value and temperature dependence of the rate constants and other characteristics of the considered processes. These effects are described at the atomic or molecular level based on the multi-phonon theory, starting from the first pioneering studies through to contemporary studies. A number of questions are included at the end of many chapters to further reinforce the material presented. Unified approach to the description of numerous physico-chemical phenomena in different materials Based on the pioneering research work of the authors Explantion of a variety of experimental observations Material is presented at two levels of complexity for specialists and non-specialists Identifies existing and potential applications of the processes and phenomena Includes questions at the end of some chapters to further reinforce the material discussed.The book is devoted to the consideration of the different processes taking place in thin films and at surfaces. Since the most important physico-chemical phenomena in such media are accompanied by the rearrangement of an intra- and intermolecular coordinates and consequently a surrounding molecular ensemble, the theory of radiationless multi-vibrational transitions is used for its description. The second part of the book considers the numerous surface phenomena. And in the third part is described the preparation methods and characteristics of different types of thin films. Both experimental and theoretical descriptions are represented. Media rearrangement coupled with the reagent transformation largely determines the absolute value and temperature dependence of the rate constants and other characteristics of the considered processes. These effects are described at the atomic or molecular level based on the multi-phonon theory, starting from the first pioneering studies through to contemporary studies. A number of questions are included at the end of many chapters to further reinforce the material presented. Unified approach to the description of numerous physico-chemical phenomena in different materials Based on the pioneering research work of the authors Explantion of a variety of experimental observations Material is presented at two levels of complexity for specialists and non-specialists Identifies existing and potential applications of the processes and phenomena Includes questions at the end of some chapters to further reinforce the material discussed.1. Introduction, Leonid I. Trakhtenberg, Sheng H. Lin, Olusegun J. Ilegbusi -- Part I. Theoretical Approaches to the Study of the Processes in Films and at the Surfaces -- 2. Conventional Theory of Multi-Phonons Eelectron Transitions, Mortko A. Kozhushner -- 3. Contemporary Theory of Electrons Tunneling in Condensed Matter, Mortko A. Kozhushner -- 4. Ab Initio Calculations of Electronic Transitions and Photoabsorption and Photoluminescence Spectra of Silica and Germania Nanoparticles, Aleksandr M. Mebel, Aleksandr S. Zyubin, Michitoshi Hayashi, and Sheng H. Lin -- 5. Density Matrix Treatments of Ultrafast Radiationless Transitions, Sheng H. Lin, Kuo K. Liang, Michitoshi Hayashi, and Aleksanr M. Mebel -- 6. Ultrafast Radiationless Transitions, Michitoshi Hayashi, Aleksandr M. Mebel, and Sheng H. Lin -- Part II. Physico-Chemical Processes at the Surface of Solids -- 7. Point Defects on the Silica Surface: Structure and Rreactivity, Viktor A. Radzig -- 8. Atomic -- Molecular Kinetic Theory of Physico-Chemical Processes in Condensed Phase and Interfaces, Yuriy K. Tovbin -- Part III. Formation and Physico-Chemical Properties of Thin Films -- 9. Integrated Approach to Dielectric Film Growth Modeling: Growth Mechanisms and Kinetics, Alexander A. Bagatur'yants, Maxim A. Deminskii, Andrei A. Knizhnik, Boris V. Potapkin, and Stanislav Ya. Umanskii -- 10. Vapor Deposited Composite Films Consisting of Dielectric Matrixe with Metal/Semiconductor Nanoparticles, Genrikh N. Gerasimov, Leonid I. Trakhtenberg -- 11. Transport and Magnetic Properties of Nanogranular Metals, Boris A. Aronzon, Sergei V. Kapelnitsky and Aleksandr S. Lagutin -- 12. Organized Organic Thin Films: Structure, Phase Transitions and Chemical Reactions, Sofia L. Trakhtenberg -- 13. Non-Catalytic Photoinduced Immobilization Processes in Polymer Films, Sofia L. Trakhtenberg, Amy S. Cannon and John C. Warner -- 14. Formation of Unconventional Compounds and Catalysts in Magnesium-Containing Organic Films, -- Vladimir V. Smirnov, Ludmila A. Tyurina and Irina P. Beletskaya -- 15. Charge Effects in Catalysis by Nanostructured Metals, Sergei A. Gurevich, Vladimir M. Kozhevin, Irina N. Yassievich, Denis A. Yavsin, Tatyana N. Rostovshchikova, Vladimir V. Smirnov -- 16. Synthesis of Crystalline C-N Thin films, Hongwei Song and Olusegun J. Ilegbusi.Print version record.Elsevie

Structure, Conductivity, and Sensor Properties of Nanosized ZnO-In₂O₃ Composites: Influence of Synthesis Method

The influence of the method used for synthesizing ZnO-In2O3 composites (nanopowder mixing, impregnation, and hydrothermal method) on the structure, conductivity, and sensor properties is investigated. With the nanopowder mixing, the size of the parent nanoparticles in the composite remains practically unchanged in the range of 50–100 nm. The impregnation composites consist of 70 nm In2O3 nanoparticles with ZnO nanoclusters 2 is 1.3–1.5 times higher than the response of the mixed composite. Additives of 15–20 and 85 wt.% ZnO to mixed and impregnated composites lead to an increase in the response compared with pure In2O3. In the case of hydrothermal composite, up to 20 wt.% ZnO addition leads to a decrease in response, but 65 wt.% ZnO addition increases response by almost two times compared with pure In2O3. The sensor activity of a hydrothermal composite depends on the phase composition of In2O3. The maximum efficiency is reached for the composite containing cubic In2O3 and the minimum for rhombohedral In2O3. An explanation is provided for the observed effects