Denis Kuznetsov

Considerable Variation of Antibacterial Activity of Cu Nanoparticles Suspensions Depending on the Storage Time, Dispersive Medium, and Particle Sizes

Suspensions of Cu nanoparticles are promising for creating the new class of alternative antimicrobial products. In this study we examined copper nanoparticles of various sizes obtained by the method of wire electric explosion: nanopowder average size 50 nm (Cu 50) and 100 nm (Cu 100). The paper presents the complex study of the influence of physicochemical properties such as particle size and concentration of the freshly prepared and 24-hour suspensions of Cu nanoparticles in distilled water and physiological solution upon their toxicity to bacteria E. coli M-17. Ionic solution of Cu2+ and sodium dichloroisocyanurate was used for comparison study. It has been shown that decrease in the nanoparticle size leads to changes in the correlation between toxicity and concentration as toxicity peaks are observed at low concentrations (0.0001⋯0.01 mg/L). It has been observed that antibacterial properties of Cu 50 nanoparticle suspensions are ceased after 24-hour storage, while for Cu 100 suspensions no correlation between antibacterial properties and storage time has been noted. Cu 100 nanoparticle suspensions at 10 mg/L concentration display higher toxicity at substituting physiological solution for water than Cu 50 suspensions. Dependence of the toxicity on the mean particle aggregates size in suspension was not revealed.

Analysis of the effect of preparation conditions for potassium polytitanates on their morphological properties

Results are provided for a study of the effect of preparation conditions on the structural properties of dispersed systems based on potassium polytitanates. It is established that on heating there are complex structural transformations within polytitanates, and the composition of modifying surface-active substances (SAS) has a specific effect on microstructure formation and the final morphology of polytitanate particles. Temperature regimes are determined making it possible with use of non-iogenic SAS to prepare nanostructured powder materials consisting of uniform fiber particles less than 10 nm thick, 30 – 50 nm wide, and 2 – 5 μm long.

Synthesis of five metal based nanocomposite via ultrasonic high temperature spray pyrolysis with excellent antioxidant and antibacterial activity

A unique five metal (Zn, Cu, Ni, Fe, and Mg) based nanocomposite material was prepared via ultrasonication high temperature spray pyrolysis maintained at 1200 °C. The influence of different concentrations (0.001 M, 0.01 M, and 1 M) on size and crystalline phase were analyzed. The nanocomposite exhibited excellent antioxidant and antibacterial activity.

Acute toxic and cytogenetic effects of carbon nanotubes on aquatic organisms and bacteria

This paper summarizes a comprehensive study concerning the acute toxicity of a commercial carbon nanomaterial consisting mostly of carbon nanotubes to larvae of Chironomidae, crustaceans Ceriodaphnia affinis, algae Scenedesmus quadricauda, and bacteria Escherichia coli. It is shown that the nucleolar organizer region (NOR) index of polytene chromosomes in the salivary gland cells of midge larvae depends on the duration of concentration and exposure. This fact is indicative of the switching on of cell adaptation pathways in response to a xenobiotic stressor to restore cell homeostasis. The investigated nanomaterial is labeled as a Class III environmentally hazardous material (moderately hazardous). Safe concentrations of the carbon nanomaterial in aquatic media are less than 2 mg/L. It is concluded that larvae of Chironomidae are the most resistant to the material of all test species, whereas Scenedesmus quadricauda and Escherichia coli are the most sensitive.

Nanosized zero-valent iron as Fenton-like reagent for ultrasonic-assisted leaching of zinc from blast furnace sludge

Ultrasonic-assisted sulphuric acid leaching combined with a Fenton-like process, utilizing nanoscale zero-valent iron (nZVI), was investigated to enhance the leaching of zinc from the blast furnace sludge (BFS). The leaching of iron (Fe) and zinc (Zn) from the sludge was investigated using Milli-Q water/BFS ratio of 10 and varying the concentration of hydrogen peroxide, sulphuric acid, the temperature, the input energy for ultrasound irradiation, and the presence or absence of nZVI as a Fenton reagent. The results showed that with 1g/l addition of nZVI and 0.05M of hydrogen peroxide, the kinetic rate of Zn leaching increased with a maximum dissolution degree of 80.2%, after 5min treatment. In the absence of nZVI, the maximum dissolution degree of Zn was 99.2%, after 15min treatment with 0.1M of hydrogen peroxide. The rate of Zn leaching at several concentrations of hydrogen peroxide is accelerated in the presence of nZVI although a reduction in efficiency was observed. The loss of Fe was no more than 3%. On the basis of these results, the possible route for BFS recycling has been proposed (BFS slurry mixed with sulphuric acid and hydrogen peroxide is recirculated under ultrasonic irradiation then separated).

Chemical vapour deposition and characterization of uniform bilayer and trilayer MoS2 crystals

Molybdenum disulfide (MoS2) is a promising two-dimensional semiconductor for applications in electronics, optoelectronics and catalysis. Chemical vapor deposition (CVD) is a popular approach for the large-scale growth of thin MoS2 crystals. As the properties of MoS2 strongly depend on the number of layers, it is important to reliably grow MoS2 crystals with different thicknesses. In this paper, we present a CVD procedure for MoS2 growth from MoO3 and S, which yields predominantly bilayer and trilayer MoS2 triangular islands as opposed to monolayer MoS2 triangles typically observed in similar CVD experiments. The growth of bilayer and trilayer MoS2 crystals is achieved by increasing the flow rate of sulfur after the original nucleation of MoS2 triangles. Most bilayer MoS2 crystals are uniform in height, such that in a typical crystal the top layer fully extends to the edges of the bottom layer. While trilayer MoS2 crystals grown by this procedure are in general less uniform than bilayers and often form terraced structures, it is still common to observe uniform trilayer MoS2 triangles as well. In addition to standard characterization methods for MoS2, such as Raman spectroscopy, atomic force microscopy and photoluminescence microscopy we demonstrate that scanning electron microscopy can be used to distinguish between monolayer and few-layered MoS2 flakes at low accelerating voltages. The field-effect transistors based on CVD-grown MoS2 triangles have electron mobilities reaching ∼10 cm2 V−1 s−1 and ON/OFF ratios reaching ∼105. The reported CVD procedure can be used for growing large quantities of uniform bilayer and trilayer MoS2 crystals for materials studies.

Morphometric Parameters and Biochemical Status of Oilseed Rape Exposed to Fine-dispersed Metallurgical Sludge, PHMB-stabilized Silver Nanoparticles and Multi-wall Carbon Nanotubes

Thepaper Presents Biological Properties of Threefine-Dispersed Materials, Namely Metallurgical Sludge, Colloidal Silver Andmulti-Wall Carbon Nanotubes (MWCNT) Exposing Oilseed Rape Plants. the Stimulationof Plant’s Growth by Silver Nanoparticles and the Intensification of Plantpigments Synthesis by MWCNT have been Experimentally Demonstrated. A Small Decreasein Energy and Germination Capacity were Noticed Whereby Colloidal Silver Hadthe Lowest Suppressive Effect, MWCN Tubes had the Highest Effect, and Sludge Wasfound in between Two above-Mentioned Materials. According to the Research, the Usageof Sludge is the most Effective at the Concentration of 10 and 100 g/l,colloidal Silver – 10 g/l and 300 g/l, MWCNT – 0,001 g/l and 1 g/l.

Nitrobacter sp. extract mediated biosynthesis of Ag2O NPs with excellent antioxidant and antibacterial potential for biomedical application

In this study, extracellular extract of plant growth promoting bacterium, Nitrobacter sp. is used for the bioconversion of AgNO3 (silver nitrate) into Ag2O (silver oxide nanoparticles). It is an easy, ecofriendly and single step method for Ag2O NPs synthesis. The bio-synthesized nanoparticles were characterized using different techniques. UV-Vis results showed the maximum absorbance around 450 nm. XRD result shows the particles to have faced centered cubic (fcc) crystalline nature. FTIR analysis reveals the functional groups that are involved in bioconversion such as C-N, N-H and C=O. Energy-dispersive X-ray spectroscopy (EDAX) spectrum confirms that the prepared nanoparticle is Ag2O NPs. Particle size distribution result reveals that the average particle size is around 40 nm. The synthesized Ag2O NPs found to be almost spherical in shape. Biosynthesized Ag2O NPs possess good antibacterial activity against selected Gram positive and Gram negative bacterial strains namely Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae when compared to standard antibiotic. In addition, Ag2O NPs exhibits excellent free radical scavenging activity with respect to dosage. Thus, this study is a new approach to use soil bacterial extract for the production of Ag2O NPs for biomedical application.

Conjugates of α-Cobratoxin with CdSe Quantum Dots: Preparation and Biological Activity

α-Cobratoxin is the main neurotoxin in the cobra Naja kaouthia venom; it binds efficiently and selectively with neuronal α7 and muscle type nicotinic acetylcholine receptor and can be used for specific labeling and visualization of these receptors in organs and tissues. For these applications we have prepared conjugates of α-cobratoxin with CdSe quantum dots which have many benefits as compared to organic fluorescent labels. To prepare the conjugate, CdSe quantum dots with ZnS shell were functionalized using a tripeptide glutathione and coupled to toxin using water soluble carbodiimide. The conjugate was purified by gel-filtration chromatography and tested for biological activity. It was found that conjugate preserved the capacity to interact with both neuronal α7 and muscle type nicotinic acetylcholine receptor. Its cytotoxicity to mammalian cells was not higher than that of functionalized quantum dots.

Gold Nanoflowers and Gold Nanospheres as Labels in Lateral Flow Immunoassay of Procalcitonin

In this study, new types of nanogold labels for lateral flow immunoassay of model antigen procalcitonin based on photometric and surface-enhanced Raman scattering methods of detection were obtained. The linear range of procalcitonin determination applying gold nanoflowers as a label was between 0.5 and 10 ng/mL. The limit of photometric detection was achieved at 0.1 ng/mL that was five times lower than the sensitivity of traditional lateral flow immunoassay with spherical gold nanoparticles as a label. In addition, the conjugate of polyclonal antibodies against procalcitonin with spherical gold nanoparticles labeled with 4-mercaptobenzoic acid as Raman reporter molecule was prepared and used as an immunoprobe in lateral flow immunoassay based on surface-enhanced Raman spectroscopy to improve assay sensitivity.