Table of contents

I review the major research activities of my groups at the National University of Information Technologies, Mechanics, and Optics (St Petersburg) and Nonlinear Physics Center (Canberra, Australia) in the field of electromagnetic metamaterials operating at microwave and optical frequencies.

Some aspects of the thermodynamics and mechanics of solid surfaces, in particular with respect to surface stress and surface energy, are reviewed. The purpose is to enlighten the deep differences between these two physical quantities. We consider successively the case of atomic flat surfaces and the case of vicinal surfaces characterized by surface stress discontinuities. Finally, experimental examples, concerning Si surfaces, are described.

This paper describes the attachment of conjugated oligomers onto electrode surface through the reduction of diazonium compounds. In this connection some properties of conjugated oligomers and of layers grafted through diazonium electroreduction will first be briefly presented. The electrochemical behavior of conjugated oligomers grafted on a surface using diazonium electroreduction will then be discussed.

Structural modifications in silicon matrix due to heavy ion (Au²⁺) implantation are studied using mainly Raman spectroscopy and x-ray diffraction (XRD) method. Raman spectra show a red-shift in their peak position along with line-width broadening with respect to increase in implantation fluence. This is explained taking both phonon confinement and stress into account. Heavy ion implantation introduces tensile stress in the silicon matrix. The amount of stress produced as a function of fluence has been calculated. A proposed model explaining the Raman shift and peak broadening is discussed in detail. XRD results also go in-line with the above analysis.

In this paper we propose a new protocol which allows two distant parties to simultaneously and deterministically exchange their states under control of a third remote party in such a way that it cannot succeed without permission of the controller. The original non-local quantum resource a priori shared among the three parties is a quintet of qubits in a so-called linear cluster state.

Perpendicularly self-aligned TiO₂ nanotube samples of size of 3 × 5 cm² were fabricated by the electrochemical anodization method using a solution containing NH₄F. Influences of the technological conditions such as NH₄F concentration and anodization voltage were studied. It was found that NH₄F concentration in the solution and anodization voltage significantly affect the diameter and length of a TiO₂ nanotube. The diameter and the length of a TiO₂ nanotube were observed and estimated by using scanning electron microscopy. It has shown that the largest diameter and the longest length of about 80 nm and 20 μm, respectively, were obtained for the sample anodized in a solution containing 0.4% of NH₄F, under a voltage of 48 V. Photoluminescence spectra excited by laser lights having wavelengths of 325 and 442 nm (having energies higher and lower than the band gap energy of TiO₂) was recorded at room temperature for the TiO₂ nanotube arrays. An abnormal luminescence result was observed. It is experimental evidence that the manufactured TiO₂ nanotube array is an expected material for hydrogen splitting from water by photochemical effect under sunlight as well as for the nano solar cells.

We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter.

Hesperetin (HET), a naturally occurring plant bioflavonoid present in citrus fruits, possesses potential anti-inflammatory and anti-carcinogenic activities but poor aqueous solubility limits its applications. To improve its applicability in cancer therapy, hesperetin was encapsulated in Eudragit^® E (EE) 100 nanoparticles in the presence of polyvinyl alcohol (PVA) as a stabilizer and its anticancer efficacy in oral carcinoma (KB) cells was studied. Hesperetin-loaded nanoparticles (HETNPs) were prepared by nanoprecipitation method and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and x-ray diffraction (XRD). The results thus displayed that the prepared nanoparticles showed a particle size in the range from 55 to 180 nm. The encapsulation efficiency of hesperetin was 83.4% obtained by UV spectroscopy. The in vitro release kinetics of hesperetin under physiological condition show initial rapid release followed by slow and sustained release. 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed higher cytotoxic efficacy of HETNPs than native hesperetin in KB cells. Further, it has been found that reactive oxygen species (ROS) generation, DNA damage and apoptotic indices in HETNPs treated cells are greater than those in native hesperetin treatment. Hence these findings demonstrate that HETNPs could be a potentially useful drug delivery system to produce better hesperetin therapeutics of cancers.

Adsorbates on graphene can create resonances that lead to efficient electron scattering and strongly affect the electronic conductivity. Therefore, a proper description of these resonances is important to gain a good insight into their effect on conductivity. The characteristics of the resonance and in particular its T-matrix depend on the adsorbate itself but also on the electronic structure of graphene. Here we show that a proper tight-binding model of graphene which includes hopping beyond the nearest-neighbor leads to sizable modifications of the scattering properties with respect to the mostly used nearest neighbor hopping model. We compare results obtained with hopping beyond the nearest-neighbor to those of our recent work (2013 Phys. Rev. Lett.113 146601). We conclude that the universal properties discussed in our recent work are unchanged but that a detailed comparison with experiments requires a sufficiently precise tight-binding model of the graphene layer.

Nanoparticles of ZnO₂ were synthesized by a sol–gel method using Zn(CH₃COO)₂ and H₂O₂ in an aqueous solution exposed to either ultraviolet (UV) or ultrasound irradiation. X-ray diffraction and scanning electron microscopy showed that the nanostructures consisted of spherical blackberry-like clusters. Nanoparticles fabricated by using UV irradiation had smaller sizes and narrower size distributions than nanoparticles prepared by using ultrasound. Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms, and the antibacterial activity of the ZnO₂ nanoparticles was studied by use of the well diffusion agar bacteriological test. ZnO₂ nanoparticles synthetized using UV had the best antibacterial properties. The inhibition zone was largest for B. subtilis but was present also for S. aureus and E. coli.

The formation of nanoscale droplets/bubbles from a metastable bulk phase is still connected to many unresolved scientific questions. In this work we analyze the stability of multicomponent liquid droplets and bubbles in closed N_j, V, T systems (total mass of components, total volume and temperature). To investigate this problem, square gradient theory combined with an accurate equation of state is used. We compare the results from the square gradient model to the macroscopic capillary description. We find that both predict a finite threshold size for droplets/bubbles. The work reveals a metastable region close to the minimal droplet/bubble radius. We find that the liquid compressibility is crucial for the existence of this minimum threshold size for bubble formation.

Composites based on polyaniline (PANi) and rice husk (RH) were prepared by two methods: the first one was chemical method by combining RH contained in acid medium and aniline using ammonium persulfate as an oxidation agent and the second one was that of soaking RH into PANi solution. The presence of PANi combined with RH to form nanocomposite was clearly demonstrated by infrared (IR) spectra as well as by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Lead(II) and cadmium(II) ion concentrations in solution before and after adsorption process on those composites were analysed by atomic adsorption spectroscopy. Of the above preparation methods, the soaking one provided a composite onto which the maximum adsorption capacity was higher for lead(II) ion (200 mg g⁻¹), but lower for cadmium(II) ion (106.383 mg g⁻¹) in comparison with the chemical one. However, their adsorption process occurring on both composites also fitted well into the Langmuir isotherm model.

It is well known that multi-walled carbon nanotubes (MWCNTs) are an excellent nanomaterial. In this paper, the nanocomposite ultra-thin films were fabricated consisting of MWCNTs and poly (3,4-ethylene dioxy thiophene-poly(styrene sulfonate) (PEDOT-PSS) for organic light-emitting diode (OLED). The field-emission scanning electron microscopy (FESEM) images of MWCNTs thin films show that the diameter of MWCNTs are 10–30 nm and their length is 300–500 nm. Electrical and optical properties of the films are investigated and the sheet resistance can reach minimum value at 36.5 Ω sq⁻¹ and the transparency of the film is about 80%. The current density–voltage (J–V) characteristics of the devices were also studied.

Injectable chitosan-based hydrogels have been widely studied toward biomedical applications because of their potential performance in drug/cell delivery and tissue regeneration. In this study we introduce tetronic–grafted chitosan containing tyramine moieties which have been utilized for in situ enzyme-mediated hydrogel preparation. The hydrogel can be used to load nanoparticles (NPs) of biphasic calcium phosphate (BCP), mixture of hydroxyapatite (HAp) and tricalcium phosphate (TCP), forming injectable biocomposites. The grafted copolymers were well-characterized by ¹H NMR. BCP nanoparticles were prepared by precipitation method under ultrasonic irradiation and then characterized by using x-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The suspension of the copolymer and BCP nanoparticles rapidly formed hydrogel biocomposite within a few seconds of the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂). The compressive stress failure of the wet hydrogel was at 591 ± 20 KPa with the composite 10 wt% BCP loading. In vitro study using mesenchymal stem cells showed that the composites were biocompatible and cells are well-attached on the surfaces.

Effects of iron and copper nanopowders (particle size of 20–40 nm) were investigated on rabbits of 1 month age and heifers of 6 months. For introduction of nanometals into the animal's ration, the mixed fodder was treated with the nanometal powder suspension in such a way: 0.08 mg of nanoiron per kg of animal's body weight and 0.04 mg kg⁻¹ for nanocopper. The weight gain of the heifers who received nanoiron and nanocopper after 8 months was 22.4 and 10.7% higher than that of the control, respectively. For the rabbits who received nano Fe and Cu after 3 months, the weight gain was 11.7 and 7.3% compared to the control, respectively. Under the action of metal nanopowders morphological indices of blood were changed in comparison with the control: after 8 months the quantity of erythrocytes increased by 19.6%, hemoglobin by 17.1% and leukocytes by 7.6%. There was a realignment in leukocytic formula: the quantity of lymphocytes increased by 9% compared to the control. Biogenic metals in superdispersive state were able to stimulate immune, enzymatic and humoral systems of the animal's organism, promoting metabolism. Adding Co and Cu metal nanopowders to the bull-calves' fodder rations increased content of Ca by 31.8 and 0%, Fe by 38.8 and 37.5%, K by 19.2 and 15.3%, Mg by 17.6 and 23.5%, Mn by 9.8 and 45% and Na by 20.5 and 8.8%, respectively, compared to control. Metal nanopowders improved the quality indices and meat productivity of black–white bull-calves, expressed in intensive growth of muscle, tissue and more nutritious meat. The conducted veterinary–sanitary expertise showed that the supplements based on iron, cobalt and copper nanopowders can be used as safe bioactive supplements in animal husbandry.

Carbon-nanotube-based liquids—a new class of nanomaterials—have shown many interesting properties and distinctive features offering unprecedented potential for many applications. This paper summarizes the recent progress on the study of the preparation, characterization and properties of carbon-nanotube-based liquids including so-called nanofluids, nanolubricants and different kinds of nanosolutions containing multi-walled carbon nanotubes/single-walled carbon nanotubes/graphene. A broad range of current and future applications of these nanomaterials in the fields of energy saving, power electronic and optoelectronic devices, biotechnology and agriculture are presented. The paper also identifies challenges and opportunities for future research.

In this communication a mechanism for spider silk strain hardening is proposed. Shear failure of β-sheet nanocrystals is the first failure mode that gives rise to the creation of smaller nanocrystals, which are of higher strength and stiffness. β-sheet unfolding requires more energy than nanocrystal separation in a shear mode of failure. As a result, unfolding occurs after the nanocrystals separate in shear. β-sheet unfolding yields a secondary strain hardening effect once the β-sheet conformation is geometrically stable and acts like a unidirectional fibre in a fibre reinforced composite. The mechanism suggested herein is based on molecular dynamics calculations of residual inter-β-sheet separation strengths against residual intra-β-sheet unfolding strengths.

Superdispersive iron, cobalt and copper nanocrystalline powders were synthesized in a water–ethanol medium by the reduction method using sodium borohydride as a reducing agent and carboxymethyl cellulose as a stabilizer (for Fe and Co nanoparticles). Transmission electron microscopy micrographs and x-ray diffraction analyses of the freshly prepared nanocrystalline powders indicated that they were in a zerovalent state with particle sizes ranging from 20 to 60 nm. The soybean seeds were treated with an extra low nanocrystalline dose (not more than 300 mg of each metal per hectare) and then sowed on an experimental landfill plot consisting of a farming area of 180 m². This pre-sowing treatment of soybean seeds, which does not exert any adverse effect on the soil environment, reliably changed the biological indices of the plant growth and development. In particular, in laboratory experiments, the germination rates of soybean seeds treated with zerovalent Cu, Co and Fe were 65, 80 and 80%, respectively, whereas 55% germination was observed in the control sample; in the field experiment, for all of the nanoscale metals studied, the chlorophyll index increased by 7–15% and the number of nodules by 20–49% compared to the control sample, and the soybean crop yield increased up to 16% in comparison with the control sample.

Nitrogen-doped TiO₂ nanoparticle photocatalysts were synthesized by a sol–gel procedure using tetra-n-butyl orthotitanate as a titanium precursor and urea as a nitrogen source. Systematic studies for the preparation parameters and their impact on the material's structure were carried out by multiple techniques: thermogravimetric and differential scanning calorimetric analysis, x-ray diffraction, scanning electron microscope, transmission electron microscopy, energy dispersive x-ray spectroscopy and UV–Vis diffuse reflectance spectrophotometry showed that the nitrogen-doped TiO₂ calcined at 500 °C for 3 h exhibited a spherical form with a particle size about 15–20 nm and crystal phase presented a mixture of 89.12% anatase. The obtained product was deposited on a porous quartz tube (D = 74 mm; l = 418 mm) to manufacture an air photocatalytic cleaner as a prototype of the TIOKRAFT company's equipment. The created air cleaner was able to remove 60% of 10 ppm acetone within 390 min and degrade 98.5% of bacteria (total aerobic bacteria and fungi, 300 cfu m⁻³) within 120 min in a 10 m³ box. These photodegradation activities of N-TiO₂ are higher than that of the commercial nano-TiO₂ (Skyspring Inc., USA, particle size of 5–10 nm).

Nanostructured diffusion-limited-aggregation (DLA) crystal pattern formation in microemulsion consisting of water, styrene, cetyltrimethylammonium chloride (CTACl), potassium persulphate and an oscillating Belousov–Zhabotinsky (BZ) reactant is reported. A variety of spatiotemporal patterns like concentric wave, spatial (stripe) and chaotic patterns appear. A colloidal phase composed of numerous nano-sized particles has been observed. The solid phase nucleation has been found to occur in the colloidal phase and has been found to grow in a symmetric crystal pattern with the progress of the reaction finally exhibiting DLA structures. We show that the formation of a nanostructured DLA crystal pattern is governed by spatial structures emerging in the BZ microemulsion system. Without any spatial structure in the microemulsion system only hydrogel of high viscosity is formed. A nano-sized branched crystal pattern was formed with a particle diameter in the range of 60–100 nm, as evident by transmission electron microscope, powder x-ray diffraction and particle size analyser studies.