Search

Composite systems of monolayer and multilayer nickel films electrochemically deposited on single crystal (100)-oriented silicon wafers were fabricated with and without the ultrasonic agitation. The hardness and adhesion behaviour of these composite structures were characterized by Vickers microindentation test. The dependence of composite microhardness and film adhesion on the structure of the film and mixing conditions of electrolyte were analysed. Mathematical models of Chicot-Lesage and Chen-Gao were applied to experimental data in order to obtain the film hardness and adhesion parameter respectively. It is confirmed that the mechanical properties of composite systems of nickel thin films on silicon substrate can be enhanced by formation of multilayer film structure by ultrasound-assisted electro-deposition and by reducing the layer thickness in the multilayer film. Formirani su kompozitni sistemi od jednoslojnih i višeslojnih filmova nikla elektrohemijski deponovanih sa i bez ultrazvučnog mešanja na pločicama od monokristalnog silicijuma orijentacije (100). Tvrdoća i adhezija tih kompozitnih struktura su okarakterisane testom mikrotvrdoće po Vikersu. Analizirana je zavisnost mikrotvrdoće kompozita i adhezije filma od strukture filma i uslova mešanja elektrolita. Matematički modeli Šiko-Lezaža i Čen-Gaoa su primenjeni na eksperimentalne podatke kako bi se dobile vrednosti tvrdoće filma i parametra adhezije. Potvrđeno je da se mehanička svojstva kompozitnih sistema sastavljenih od tankih filmova nikla na silicijumskoj podlozi mogu poboljšati formiranjem višeslojne strukture filmova, primenom ultrazvučnog mešanja pri elektrodepoziciji i smanjenjem debljine sloja u višeslojnom filmu.

Based on microscopic (exciton) theory of optical properties of perturbed ultrathin molecular films, the absorption, reflection, and transparency indices were formulated and presented in dependence on frequencies of an external electromagnetic field in near IR region. It has been shown that all optical properties depend on the position of the crystal plane with regard to boundary planes of the film. We have determined and analyzed optical properties relations for the whole film structure based on the consideration for multiple reflection, absorption, and transparency in observed multilayered structure. The four-layered dielectric nanofilms with different boundary conditions on surfaces were analyzed and some discrete resonant absorption lines were obtained. Their number, position, and distribution depend on the boundary parameter values, i.e. on the type and the technological process of their preparation/fabrication. Practically monochromatic absorption may occur. Unlike the corresponding bulk-samples, which are total absorbers throughout the near IR, region, in ultrathin films will appear selective and discrete reflection and transparency. These results could provide a great contribution to optical engineering of nanostructures, especially in technology of designing of new electronic and photonic equipment, and for nanoparticles construction for drug carrier/delivery in nanomedicine.

The main advantage of a theoretical approach is essential knowledge of the mechanisms that allow us to comprehend the experimental conditions that we have to fulfill to be able to get the desired results. Based on our research in ultrathin crystal structures performed so far, superlattices, Q-wires and Q-dots, we will consider the materials that can act as carriers for medicines and tagged substances. For this purpose we established a shell-model of ultrathin crystals and investigated their fundamental characteristics. This could be considered as a form of nano-engineering. In this paper we will analyze application of nanomaterials in biomedicine, that is to say we will present the recent accomplishments in basic and clinical nanomedicine. Achieving full potential of nanomedicine may be years or even decades away, however, potential advances in drug delivery, diagnosis, and development of nanotechnology-related drugs start to change the landscape of medicine. Site-specific targeted drug delivery (made possible by the availability of unique delivery platforms, such as dendrimers, nanoparticles and nanoliposomes) and personalized medicines (result of the advance in pharmacogenetics) are just a few concepts on the horizon of research. In this paper, especially, we have analyzed the changes in basic physical properties of spherical-shaped nanoparticles that can be made in several (nano)layers and have, at the same time, multiple applications in medicine. This paper presents a review of our current achievement in the field of theoretical physics of ultrathin films and possible ways to materialize the same in the field of nanopharmacy.

The basis of modern optical engineering involves makes finding ways to design predefined optical (and in general – physical) properties of nanoscopic patterns. The boundary parameters of nano-patterns depend on (small) dimensions and the type of nanostructure substance, the external environment, as well as the form and the technical–technological of aspect of production. Fundamental properties of nano-structures can be drastically changed by changing these parameters. We have investigated the optical specificities of molecular dielectric crystal nanofilm under the influence of different confinement conditions. This paper presents a model of crystalline ultrathin molecular film and an analysis of dielectric, i.e. optical properties of these spatially much bounded structures – in their entirety. Using the two-time dependent Green's functions, the energy spectrum, the possible exciton states and their space distribution were determined and the dynamic permittivity was calculated. It was shown that the appearance of localized states in the boundary layers of the film depends on the thickness and the changing values of the system parameters in the boundary areas of the film. These localized states define the schedule and determine the number of resonant absorption peaks in the infrared region of the external electromagnetic radiation (EMR). Analytical analysis of the impact of the boundary parameters on the changes of the dielectric and optical properties of the nanofilm, as compared to the same properties of bulk samples with identical crystalline and chemical structure, is impossible. Thus, a software package (dubbed JOIG_S) has been developed and applied to perform the numerical analysis and plot graphic displays of the relation between microscopic (exciton) and macroscopic (dielectric and optical) properties as a function of the frequency of an external electromagnetic field (EMF), for a specified set of values of the boundary parameters. Optical, i.e. absorption and refraction properties of observed nanostructures demonstrate very narrow and strictly discrete characteristics. Characteristic resonant peaks appear in the dependence of the absorption index on the frequency of external EMF. All peaks fall into infrared region and indicate absorption of corresponding external EM frequencies. The number and distribution of these peaks depend on the number of layers in the film and the perturbation parameters, as a consequence of the quantum size and confinement effects. This proved that the outer environment of the film affects the given fundamental properties of a nano film, i.e. their choice/change directly controls the optical properties of the film. Such an approach could be considered as a kind of optical engineering.

Instead of usual approach, applying displacement-displacement Green’s functions, the momentum-momentum Green’s functions will be used to calculate the diffusion tensor. These functions enter into Kubo’s formula defining diffusion properties of the system. Calculation of the diffusion tensor requires solving of the system of difference equations. It is shown that the elements of the diffusion tensor express discrete behaviour of the dispersion law of elementary excitations and, more important - that they are temperature independent.

Nanotehnologije su u stanju pružiti velike mogućnosti u unapređivanju, prvenstveno termodinamičkih i mehaničkih, osobina građevinskih materijala, najčešće betona i betonskih konstrukcija. Nanomaterijali poboljšavaju održivost, izdržljivost, ali i neka druga svojstva kao što je, npr., mogućnost samočišćenja. Naučna istraživanja nanostruktura su u stalnom porastu, pružajući nova saznanja o potencijalu njihove primjene u građivinarstvu, čime se otvaraju mnogobrojne mogućnosti u poboljšanju karakteristika, ali i smanjenju troškova proizvodnje i ugradnje građevinskih materijala. Ovaj rad će dati pregled nekih osnovnih definicija nanotehnologija i karakterizacije nanostruktura, kao i nanoaditiva koji su danas najznačajniji u unapređenju građevinskih (betonskih) proizvoda.

In this paper we have applied theory of exciton on the ultrathin molecular dielectric films—layered nanostructures with the thickness up to 20 atomic layers. We have calculated optical properties: the absorption, reflection and transparency indices as the function of frequencies of external electromagnetic field in near IR region. We showed that one of the significant properties of the ultrathin film is their interaction with substrate or environment, which could be represented through perturbation parameters. For symmetrically perturbed films, all optical properties depend on the position of the crystal plane with regard on boundary planes of the film. We have analyzed optical properties for the whole film structure based on the consideration for multiple reflection, absorption and transparency. The theory has been applied for the four-layered dielectric nanofilms with various different boundary conditions on film surfaces. As a result, we obtain some discrete resonant absorption lines, where their number, position and distribution strongly depend on the boundary parameter values, i.e. on the type and the technological process of their preparation/fabrication. While balk made from the same material totally absorb the near IR region, in ultrathin films will appear only selective and discrete absorption (also with reflection and transparency too). These results could be used in optical engineering of nanostructures and technology of designing of new electronic, photonic and photovoltaic devices. In addition, particularly designed nanoparticles are used in nanomedicine, whose behavior strongly depends on external electromagnetic field, in purpose of drug carry or delivery.

In continuation of our research regarding the phonon-induced properties of the low dimensional structures, we are investigating the impact of changes in boundary parameters onto the thermodynamic properties of the quasi 2D crystals (ultrathin films). Internal energy and thermal capacitance of the ultrathin film are theoretically analyzed and numerically and graphically presented for the various combinations of boundary surface parameters. This research is motivated by efforts to explain many unusual thermal properties of novel two-dimensional materials. The obtained results are also of great significance for the heat removal and other important physical properties and processes in ultrathin films, with special emphasis to the improvement of the superconducting properties towards the high T C superconductivity.

This work primarily analyses the temperature dependence of the relaxation time of elementary excitations – quasi-particles (electrons) in graphene. Various mechanisms of relaxation (electrons collisions with impurities, with phonons, with vacancies, etc.) are essential in transport processes. Therefore, for some of the most characteristic and most common collisions a relaxation time is obtained. Regardless of which method (for example, solving the Boltzmann equation with the adequate initial boundary conditions and similar) is used for studying the transport characteristics, these relaxation times play a fundamental role. Their role is particularly significant in obtaining the temperature dependence of coefficients of electronic and thermal conductivity, as measurable macroscopic transport characteristics. In this text, relaxation times have been obtained by analytical analysis of the scattering process in the characteristic processes mentioned above. However, the temperature dependence of the relaxation time, including the relevant transport values, is not possible to obtain without the adequate law of scattering of elementary excitations. Here in this work, it was obtained by the method of Green's functions and it was applied to determine the temperature dependence of the relaxation time of charge carriers in the main scattering processes in graphene.

Recent research in nano-optical engineering and in nanomedicine as well, seeks for methods of construction of various types of nano-markers, nano-carriers, and ways to deliver drugs to the exactly determined regions of body. In this process it is important to find methods of recognition of certain types of molecules. It is obvious that optical recognition would be the easiest and the most effective way to do it. Our research presents a model of a molecular ultrathin crystalline film and generated exciton system inside it and corresponding methodology of analysis of their optical characteristics. Properties of these spatially very restricted structures are very sensitive to their surrounding surfaces. Using the two-time Green’s functions adapted for crystalline structures with symmetry breaking, and graphical-numerical software, we have calculated the energy spectra and possible exciton states. We have shown that the appearance and the presence of localized states on the surfaces and in the boundary layers of the film depend on the thickness of the film and the film surroundings, presented through the perturbation of parameters on surfaces. Optical properties in these structures demonstrate discrete and very selective resonant absorption spectra, depending on the perturbation on their surfaces.

In this paper, we investigated the influence of size effect on thermodynamic properties of ultra-narrow wires with a simple cubic lattice, by means of two-time dependent Green functions method, adjusted to confined crystalline structures. Poles of Green functions, which defining phonon spectra, are found by solving the secular equation. For different boundary parameters, this problem is presented graphically. The temperature behavior of ultra-narrow wire thermal capacitance is compared to that of bulk structures. It turned out that in low-temperature region thermal capacitance of the ultra-narrow wire is notably lower than in the corresponding bulk sample. How this fact reflects the thermal, conducting and superconducting properties of materials, is discussed in the conclusion.

Optoelectronic properties of ultra-thin boron nitride nanotubes and charge carrier hopping properties between them were investigated within density functional theory. The study encompassed calculations of optoelectronic quantities, such as reorganization energies, oxidation and reduction potentials and charge carrier hopping rates between mentioned nanotubes. Charge coupling was calculated applying full quantum mechanical treatment, while Marcus theory was used for calculations of charge carrier hopping rates. Results indicate differences between investigated types of boron nitride nanotubes. With the increase in dimensions of boron nitride nanotubes optoelectronic properties are improving, while charge carrier hopping rates are the highest for (6, 0) boron nitride nanotube.

The changes of optical properties under boundary presence in molecular crystal nanofilm were theoretically investigated in this work. The dispersion law and states of excitons as well as their space distribution along boundary direction have been determined using adjusted Green’s function method and also by combined analytical and numerical calculations. We study the basic micro and macroscopic physical characteristics of symmetric ultrathin molecular crystalline films and one can see that essential optical properties of these systems arise with perturbation conditions, which appear at their surface layers. On the basis of real and imaginary part of relative permittivity, the absorption, refraction, reflection and transparency indices were determined, and the influences of boundary parameters on occurrence of a very selective and strictly discrete absorption, refraction and transparency were analyzed. What we have found particularly interesting is the significant percentage of reflected and transparent electromagnetic IR radiation in the nanofilm, although bulk samples of the same crystallographic structure are complete absorbers of this spectrum.

In this paper we have calculated optical changes under the influence of the boundary conditions in molecular crystalline nanostructured films. We have used theoretical model with the adjusted Greens functions, and using numerical calculations we have calculated dispersion law for excitons, and their spatial distribution along the boundary planes. In this procedure we limited ourselves on case with symmetrically perturbed conditions, and showed that the primary optical properties significantly change just in these planes where perturbations have main influence. We have determined coefficient of absorption, reflection, transparency and refraction on the base of real and imaginary part of the relative dielectric permittivity. Especially interesting case is that those structures show significantly contribution of the reflective and transparent radiation in the IR part of the spectra, while the same material in bulk almost completely absorb radiation in this part of spectra.

Metoprolol (MET) belongs to a group of frequently used β1-blockers, which often occur in waste waters. The objective of this work was to employ liquid chromatography (LC) and total organic carbon methods to study the photocatalytic degradation of MET in UV irradiated aqueous suspensions of TiO2 (Wackherr's “Oxyde de titane standard” and Degussa P25), in the presence of different electron acceptors such as molecular oxygen, hydrogen peroxide, potassium bromate, and ammonium persulfate. The degradation rates were found to be strongly influenced by the kind of electron acceptor and the type of catalyst. The optimal amount of hydrogen peroxide and potassium bromate was investigated as well. MET photocatalytic degradation was the fastest in the presence of O2 and potassium bromate with TiO2 Degussa P25, while mineralization was most efficient in the presence of molecular oxygen alone. In all investigated cases, degradation followed a pseudo-first order kinetics. Reaction intermediates of MET degradation in the presence of different electron acceptors with both catalysts were studied in detail and a number of them were indentified using LC-ESI-MS/MS. The interactions with MET of reactive radical species relevant to this study (O2˙−, ˙OH, BrO2˙, and SO4˙−) were theoretically investigated by means of density functional theory (DFT) computations.

This paper presents the results of research conducted in the field of confinement effects in ultrathin dielectric films. Method of choice is the method of Green's functions which proved to be a very powerful tool for theoretical research in solid state physics. Among many other properties of materials, such as optical, conductive, etc. with this method it is possible to obtain critical values of boundary parameters corresponding to all transitions from bulk to localized exciton states. This research is valid for four layered crystalline film, since that type of ultrathin structure was the object of research. Conditions for occurrence of one, two, three, or even four localized states have been found and analyzed and regions with equal number of localized states have been defined. This corresponds to the process of reconstruction of the energy spectra of excitons in quasi 2D nanostructures with respect to those in corresponding bulk-structures.

Instead of usual approach, applying displacement-displacement Green's functions, the momentum-momentum Green's functions will be used to calculate the diffusion tensor. With this type of Green's function we have calculated and analyzed dispersion law in film-structures. A small number of phonon energy levels along the direction of boundary surfaces joint of the film are discrete-ones and in this case standing waves could occur. This is consequence of quantum size effects. These Green's functions enter into Kubo's formula defining diffusion properties of the system and possible heat transfer direction through observed structures. Calculation of the diffusion tensor for phonons in film structure requires solving of the system of difference equations. Boundary conditions are included into mentioned system through the Hamiltonian of the film-structure. It has been shown that the diagonal elements of the diffusion tensor express discrete behavior of the dispersion law of elementary excitations. More important result is that they are temperature independent and that their values are much higher comparing with bulk structures. This result favors better heat conduction of the film, but in direction which is perpendicular to boundary film surface. In the same time this significantly favors appearance 2D superconducting surfaces inside the ultra-thin crystal structure, which are parallel to the boundary surface. This is the peer-reviewed version of the article: Šetrajčić, Jovan P., Stevo Jaćimovski, and Siniša M. Vučenović. 2017. ‘Diffusion of Phonons through (along and across) the Ultrathin Crystalline Films’. Physica A-Statistical Mechanics and Its Applications 486: 839–48. [https://doi.org/10.1016/j.physa.2017.06.003]

The different nanostructures (quantum dots, wires and wells) have specific properties which differ from those of the corresponding bulk structures. This fact leads to many applications in several branches of physics. In the paper we examine the behavior of a quantum system (a free particle and a quantum free particle gas) trapped inside the infinite quantum well, by using the coherent states formalism. Our approach is based on the fact that the dynamical group associated with the infinite quantum well is SU(1, 1), with the Bargmann index k = 1/2. These coherent states always have the sub-Poissonian behavior. There is a similarity between the energy main quantum number n and the absolute value of the complex variable z which labels the coherent states. This allows us to make a useful approximation in order to calculate the partition function and some thermodynamic characteristics of a canonical non interacting particle gas embedded in the infinite square quantum well.

The changes of optical properties under boundary presence in molecular crystal nanofilm were theoretically investigated in this work. The dispersion law and states of excitons as well as their space distribution along boundary direction have been determined using adjusted Green's function method and also by combined analytical and numerical calculations. On the basis of real and imaginary part of relative permittivity, both absorption and refraction indices were determined, and the influences of boundary parameters on occurrence of a very selective and strictly discrete absorption were analyzed.

Difficulties connected to solving difference equations of hyperbolic type were analyzed in this work and discussed in detail. The results are compared to those of the standard wave equation and certain similarities were established. The method of solving the equation is generalized by means of kernel expanded into separable polynomials. The analysis was inspired by some new ideas concerning quantization of time. Two examples are given: excitons and phonons in thin crystalline films. The advanced methodology of Green’s function method and the application of this new methodology resulted in a set of interesting conclusions concerning thin film properties. The significance of the obtained spatial dependence of exciton concentration was discussed and it was concluded, on the basis of the found spatial dependence of exciton concentration, that such boundary conditions of a thin molecular film which lead to high exciton concentrations can be determined. It was also concluded that thin films possess high superconductive properties, that physical characteristics of thin films are spatially dependent and that the spatial dependence can be the basis for widening the field of application of nanostructures.

We investigated the effects of substitution on the sumanene benzylic CH2 groups with BH and NH groups using density functional theory computations. Our study shows that various properties of sumanene could be finely tuned for the application in the areas closely related to the materials science. Structural properties are significantly altered with such modifications and other properties as well. Charge distributions were evaluated through natural population analysis (NPA), while stability of investigated structures was investigated using quantum molecular descriptors. Using molecular orbital analysis further insight into the effects of substitution was obtained. Potential of sumanene as a candidate for application in the field of organic electronics is assessed through calculations of exciton binding energy. Non-linear optical properties of investigated structures were investigated using the first hyperpolarizability tensor. Special attention was paid to the aromaticity of sumanene. This property was evaluated employing NICS parameter while for detailed study of obtained results we used NBO and NBOdel analysis.

Based on the formed model of nanofilm crystal structures, changes of optical properties due to the presence of borders for the case of symmetrical ultrathin films are theoretically investigated in this paper. Influence of five border parameters on the occurrence of localized exciton states is examined, as well as their relation with the effects of discretization and selection of resonant absorption of present electromagnetic radiation. Used combined analytical-numerical calculation to find the allowed energy states of excitons and their spatial distribution (per layers) along the axis perpendicular to surface planes. We determined permittivity for the observed models of these ultrathin dielectric films and explored the influence of boundary parameters on the occurrence of discrete and selective absorption.

Numerous studies associated with carbon-based materials have shown excellent results for the adsorption of important molecules. Bearing in mind that hydrogen is important as an energy source in this paper we investigated the adsorption properties of sumanene toward hydrogen molecules. We used a theoretical and computational approach in the framework of density functional theory. Frontier molecular orbitals, HOMO and LUMO, are visualized and molecular electrostatic potential surfaces are created, in order to locate adsorption places. We determined H2 adsorption binding energies, for which we obtained the applicable results. The adsorption properties of sumanene molecules toward hydrogen molecules were discussed through analysis of the density of states, partial density of states and overlap population density of states. Our results indicate that the sumanene can be very useful in the practical application for storage of hydrogen, which is the basis for its successful energy implementation.

Sumanene has three sp 3 hybridized carbon atoms at the benzylic positions. This specific structural property can allow the functionalization of a new bowl shaped structure. We investigated the effects of substitution of the benzylic carbon atoms of sumanene with boron and nitrogen atoms within the density functional theory and time-dependent density functional theory computations. The sumanene derivatives were subjected to the analysis of changes of the molecular electrostatic potential surfaces, optical properties (UV/Vis spectra) and bowl-to-bowl inversion barrier properties with solvent effects. The bowl shaped geometry and other properties were significantly affected by the introduction of hetero atoms.

Based on microscopic (exciton) theory of optical properties of symmetrically perturbed ultrathin molecular films, the absorption, reflection and transparency indices were formulated and presented in the function of frequencies of external electromagnetic field in near infrared (IR) region. It has been showed that all optical properties depend on the position of the crystal plane with regard on boundary planes of the film. We have determined and analyzed optical properties relations for the whole film structure based on the consideration for multiple reflection, absorption and transparency in those multilayered structure. The three-layered dielectric nanofilms with different boundary conditions on surfaces were analyzed and some discrete resonant absorption lines were obtained. Their number, position and distribution depend on the boundary parameter values, i.e. on the type and the technological process of their preparation/fabrication. Practically monochromatic absorption may occur. Unlike the corresponding bulk-samples which are total absorbers throughout the near IR region, in ultrathin films will appear selective and discrete reflection and transparency too. These results could give a great contribution in optical engineering of nanostructures, especially in technology of designing of new electronic and photonic equipment, and for nanoparticles construction for drug carrier/delivery in nano-medicine.

This paper analyzes behavior (spectra and states) of the elementary charge carriers in anisotropic perovskite structures, such as modern superconducting ceramics. Translational symmetry of the atom (ion) distribution of the electron (or hole) system is broken by atomic/ionic/molecular sputtering and doping, as well as due to existence of two boundary surfaces. This is a charge carrier's model of high-temperature superconductors in which the observed symmetry breaking orthogonal to CuO planes was treated as a perturbation. The single-particle fermion's wave functions and the possible energies of charge carriers were determined.

In this article we focused on computational research of sumanenes disubstituted by boron where the two carbon atoms are substituted by two boron atoms. Disubstitution of rim carbon atoms with boron atoms significantly affected the geometry of the bowl. The main stability factors were used to determine the stability of isomers. The most stable, the shallowest and the deepest isomers were subjected to further study of NMR parameters, chemical shielding and NICS, aromaticity, bowl to bowl inversion barrier and NBO/NPA analysis. The introduction of boron atoms significantly affected the above parameters, changing the aromatic nature of rings, reducing bowl to bowl inversion barrier and produced charge transfer. The NICS are correlated with bowl depth having the result that the function of the fourth degree of bowl depth does not only correlate well to the bowl to bowl inversion barrier with bowl depth, but also finely correlates the change of the NICS and NICSzz with bowl depth.

The aim of this study is to investigate the active components of representative drugs for blood pressure regulation by applying quantum mechanical computer codes and comparison of the same for the sake of obtaining knowledge about the properties associated with the electronic structure of given molecules. The study included three well-known, but not theoretically investigated enough, active components of β-blockers: acebutolol, metoprolol and atenolol. The results are in agreement with the experimental data and were used for initial assumptions concerning the degradation of these compounds.

We have formulated a microscopic theory of optical properties of ultrathin molecular films (nanofilms), i.e. quasi 2D systems parallel to XY planes bounded by two surfaces. Exposure of nanofilms to the external electromagnetic fields has result in creation of excitons – but different than bulk ones. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green’s functions. It has been shown that two types of optical excitations can occur: bulk and surface exciton states. Exciton energy dispersion law shows discrete behavior with non-zero values. Analysis of the dielectric properties of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. In addition, permittivity shows very narrow and discrete dependence of external electromagnetic field frequency, which is a consequence of both resonance and quantum size effects. Influences of boundary conditions on optical characteristics (through analyses of dynamical absorption coefficient) of these nanostructures were specially and in details explored.