Evaluation of Optical Properties of Ag, Cu, and Co Nanoparticles Synthesized in Organic Medium

The surface plasmon resonance evaluation of colloidal metal nanoparticles, synthesized in organic medium, is reported in this work. Metal salts were dissolved in dioxane/AOT solution and reduced by hydrazine hydrate under vigorous stirring. Optical properties of obtained colloidal nanoparticles were investigated by UV-VIS spectroscopy. Theoretical predictions of optical properties of metal nanoparticles were made by means of the Mie theory and the Drude free-electron model. Geometrical parameters and distribution of metal nanoparticles in colloidal solutions were characterized by atomic force microscopy. The results show that Ag, Cu, and Co nanoparticles, synthesized in organic medium distinguish plasmonic properties. Surface plasmon resonance bands were obtained in all cases: Ag - at 430 nm, Cu - at 570 nm, Co - at 350 nm (SPR1) and 430 nm (SPR2). Comparing theoretical evaluation of nanoparticles size with atomic force microscopy analysis, we can assume that our calculations are accurate. It was found that dominating nanoparticles diameter in Ag colloidal solution is ≈ 150 nm, in Cu colloidal solution is ≈ 70 - 80 nm and in Co colloidal solution is ≈ 150 nm. It can be concluded that nanoparticles with enhanced plasmonic properties synthesized in organic medium can be widely used in order to increase efficiency of various optical elements

Formowanie i antybakteryjne właściwości elektroprzędzionych włóknin PVA zawierających małe ilości nanocząstek srebra

Electrospinning is a process which produces nonwoven material from nano/microfibres. The aim of this study was to electrospin poly(vinyl alcohol) nano/microfibres material with small amount of silver nanoparticles (Ag-NPs), and estimate the influence of Ag-NPs on the structures and antibacterial properties of nonwoven materials. It was found that the Ag-NPs concentration does not have a significant influence on the viscosity and morphologies of electrospun materials. The addition of Ag-NPs causes the formation of thinner PVA nano/microfibres. The antibacterial activity test showed that a small amount of Ag-NPs provides antibacterial properties to electrospun PVA nano/microfibres. Antibacterial properties were tested with different bacteria: Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 12453, Bacillus cereus ATCC 11778 and Candida albicans ATCC 10231. It was also noticed that the concentration of Ag-NPs in nonwoven materials affects antibacterial properties. Clearly superior antibacterial properties were obtained from nonwoven materials with a higher concentration of Ag-NPs.Celem badań było wyprzędzenie włóknin z alkoholu poliwinylowego składających się z cienkich (nano-/mikro-) włókien zawierających małe ilości nanocząstek srebra. Badano wpływ ilości nanocząstek srebra na strukturę i właściwości antybakteryjne otrzymanych włóknin. Stwierdzono, że stężenie nanocząstek srebra nie wywiera istotnego wpływu na lepkość roztworu przędzącego i morfologię wyprzędzionych włókien. Dodatek mikrocząstek srebra prowadzi do otrzymania cieńszych włókien. Stwierdzono, że już małe ilości cząstek nanosrebra powodują uzyskanie właściwości antybakteryjnych. Badano je stosując następujące szczepy: Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 12453, Bacillus cereus ATCC 11778 and Candida albicans ATCC 10231. Stwierdzono również, że stężenie nanocząstek srebra we włóknach polepsza właściwości antybakteryjne

Research into nanoparticles obtained by electric explosion of conductive materials

One of the primary nanoparticles production methods is electric explosion of wire (further - EEW) which is known as a physical phenomenon since 1771. Limitation of EEW as a method of nanoparticles production lies in a great dispersion of particle diameters - a spectrum of nano- and micrometric diameters (10(3) and higher differences in diameters are likely). Due to great differences in nanoparticles diameters formed by explosion (in aerosol conditioned by explosion), a continuous separation of nanoparticles from aerosol flows is essential. Dispersion of conductor explosion products is mostly affected by a diameter of wire, density of comparative energy, duration of the energy input. Objective of this research is to investigate the vista of producing nanoparticles by EEW at low voltage and high energy surplus using the wire of an enlarged diameter. Analyses have been made by exploding the iron wire of 60 mm length and 0.31 and 0.45 mm diameter and the copper wire of 0.375 and 0.49 mm diameter. Purity of the wire material was 99.5% of iron and 99.9% of copper. To separate nanoparticles from aerosol a separation device was used which consists of a precipitator and three stages centrifugal cyclone. SEM analysis of Fe nanoparticles using SEM showed the mean diameter of particles about 69 nm (for wire 0.45 mm). Cu nanoparticles was 97 nm in diameter (for wire 0.49 mm). XRD spectra of iron and copper nanoparticles indicated a high oxidation level of Fe and Cu (oxides of different crystollagraphic axes are formed such as Fe(3)O(4), Fe(2)O(3), CuO, Cu(2)O). A moderate quantity of pure Fe and Cu metals (Fe(110), Fe(211), C(l 11), Cu(200))Vytauto Didžiojo universitetasŽemės ūkio akademij

Influence of nanoparticles on lubricity of base mineral oil

The tribological properties of mineral oil SAE 10 modified with metallic nanoparticles were investigated. The tribological tests were performed using four-ball test rig. Friction and wear reduction properties were measured. The positive influence of nanoparticles on lubricity of mineral oil was observed. The best result was obtained when using the copper nanoparticles for a single metal nanosuspension (0.25 % Cu). Using double metal nanoparticles the best result show iron – copper nanosuspension (0.125 % Fe + 0.125 % Cu). The use of those suspensions was most efficient for pure base mineral oil. The cobalt nanosuspension does not show a significant increase in lubricity. It was observed that nanosuspensions stabilize and decrease the friction during the testsVytauto Didžiojo universitetasŽemės ūkio akademij

Tribologic properties of vegetable and mineral oils with suspended nanoparticles

Wear of the surfaces results in substantial levels of metal nanoparticles in lubricants during their service life. Prefabricated Fe, Cu and Zn nanoparticles were characterized and then added to several vegetable and mineral oils, inhibited with antioxidant. Friction, wear and heat emission of 0.1 to 1% suspensions were tested on Four-ball AW tribotester at 150N load. Fe nanoparticles did not affect the performance of mineral oils, but reduced wear tendencies of rapeseed oil. Zn nanoparticles have somewhat beneficial effect on mineral oil, without affecting rapeseed oil significantly. Blends with 1.8% ZDDP showed excellent AW performance, which was not affected by 1% Fe nanoparticle addition. In oils with other lubricity additives, the nanoparticles were generally detrimental to wear prevention, they also resulted in higher static friction coefficient and higher test sample temperatures. Inclusion of pre-fabricated nanoparticles into bench tests can accelerate evaluation of lubricant tribologic propertiesVytauto Didžiojo universitetasŽemės ūkio akademij

Optical Properties of “Black Silicon” for Solar Cells Application Formed by Laser Radiation

“Black silicon” can be formed by different methods, such as chemical, electrochemical etching and laser assisted chemical etching. Si structures produced by these methods can be used for solar cells, sensors, medical application and etc. In this work we present investigation of optical properties of “black silicon” formed by laser radiation, depending on formation circumstances. The formation of structures by laser radiation is clean and ecological method. The shape and height of micro-cone structures strongly depend on Nd:YAG laser intensity and number of laser pulses. SEM-EDX and photoluminescence methods were used to investigate the “black silicon” structures. The investigation of UV-VIS radiation spectra of Si micro-cone structure shows that they are similar to “black body”, which makes these structures useful for solar cells application

Elektrolitinių nanokristalinių volframo-kobalto ir volframo-geležies dangų plyšių susidarymo būvis

Mechaninės inžinerijos srityje, siekiant sumažinti trintį ir dilimą, pastaruoju metu didėja susidomėjimas mikrometrinio storio dangomis. Šiame darbe yra nagrinėjamas elektrolitiniu būdu gautų Co-W ir Fe-W dangų deformavimas, panaudojant įspaudimo bandymus ir nustatant tokių elektrolitinių sluoksnių paviršių mikroskopines savybes. Be to, šis tyrimas grindžiamas plastinės deformacijos laukų įspaudimo bandyme analize, ypač gūbrelio susidarymo aplink įspaudą mechanizmo susidarymuiThe use of micrometer thick coatings in tribosystems now is of increasing interest in the area of mechanical engineering to reduce friction and wear. This work was initiated to analyse critically the deformation of electrode-posited Co-W and Fe-W coatings resulting from indentation tests, and to identify the microscopic features of the surfaces of such electrodeposited layers. On other hand, the present work focuses on an improved understanding of the plastic deformation field of the indentation made in thin layer deposited on a substrate, especially the mecha-nisms formation of the pileups around the indenterVytauto Didžiojo universitetasŽemės ūkio akademij

Tribological properties of mineral oils modified with metallic nano-particles

The suspensions of metallic nano-particles stabilised with different surfactants can considerably reduce the wear of friction surfaces. Fe and Fe+Cu nano-particles can reduce the wear up to 30-45 % even taking into account the wear resistance properties of surfactants itself. Oils suspensions with nano-particles stabilise the friction torque comparing to friction of pure surfactants' suspensions, in most cases significantly reduce the friction coefficient (up to 40 %) and contribute to reducing trend of friction coefficient. Tribological efficiency of oil modified with surfactant lanolin FVE VO2 and Fe+Cu nano-particles show clear correlation of friction measurements with wear tests. Optical investigations show that it could be partially explained by forming of different wear resistant films on friction surfaceVytauto Didžiojo universitetasŽemės ūkio akademij