Synthesis and Application of Inorganic Nanoparticles as Lubricant Components – a Review

Recent achievements in chemistry and technology of nanosized inorganic particles provide possibility of synthesis in various metal oxides, chalcogenides, and so on. Surface modification of nanoparticles in some cases provides formation of their stable dispersions in liquid hydrocarbons. State of art in the field of inorganic nanoparticles’ synthesis and their application in tribology is discussed. Special attention is paid to synthesis of surface-capped and bare molybdenum sulfide nanoparticles and to testing thereof as friction-modifying additives for liquid lubricants. Differences in action mechanism of MoS_x nanoparticles and ‘molecular’ molybdenum complexes are discussed. Future trends of inorganic nanoparticles use as lubricant additives are suggested.     

One-step aqueous synthesis of CdS nanoparticles as a novel fluorescence probe for the ultrasensitive detection of DNA

One-step aqueous synthesis of CdS nanoparticles as a novel fluorescence probe for sensitive and selective determination of DNA with synchronous fluorescence spectrometric method has been developed. Different from the traditional organometallic route, in which toxic precursors or solvents might be used, the wet chemical approach demonstrated in this paper is superior in terms of simplicity, using of nontoxic materials, mild synthetic condition and good reproducibility. When Δλ=255 nm, maximum synchronous fluorescence is produced at 264 nm, the synchronous fluorescence intensity of the composite nanoparticles is significantly decreased in the presence of trace DNA at PH 0.91. Under optimal conditions, the linear ranges of the calibration curves are 0.08-30.0 μg mL⁻¹ for ctDNA and 0.05-35.0 μg mL⁻¹ for hsDNA, respectively. The detection limits are 1.5 ng mL⁻¹ for ctDNA and 2.2 ng mL⁻¹ for hsDNA, respectively. Furthermore, the method is successfully applied to the quantification of DNA in synthetic samples. The results show that this proposed method is stable, sensitive and practical for the determination of trace DNA.     

Poly(thymine)-templated copper nanoparticles as a fluorescence probe for highly selective and rapid detection of cysteine

A highly selective and rapid analytical method was proposed to detect cysteine in aqueous solution by using poly(thymine)-templated copper nanoparticles. In a neutral aqueous condition, the fluorescence of poly(thymine)-templated copper nanoparticles could be quenched by cysteine in 10?min effectively coexisting with common biological small molecules. Under the optimal experimental condition, the present assay allowed for the selective determination of cysteine in the range of 12.5–100?µM, with a detection limit of 7.3?µM. The results indicated that the poly(thymine)-templated copper nanoparticles probe would find potential application in bioanalysis.     

Photochemical decoration of silver nanoparticles on ZnO nanowires as a three‐dimensional substrate for surface‐enhanced Raman scattering measurement

To increase the sensitivity in surface‐enhanced Raman scattering (SERS) measurement, a three‐dimensional (3D) SERS substrate was prepared by the decoration of silver nanoparticles (AgNPs) on the side walls of ZnO nanowires. The prepared 3D SERS substrates provide the advantages of highly loaded density of AgNPs, with a large specific surface area to interact with analytes, and the ease for the analytes to access the surfaces of AgNPs. To prepare the substrates, ZnO nanowires were first grown on a glass plate by wet chemical method. By treating SnCl₂ on the surfaces of ZnO nanowires, Ag seeds could be formed on the side wall of the ZnO nanowires, which were further grown to a suitable size for SERS measurements via photochemical reduction. To optimize and understand the influences of the parameters used in preparation of the substrates, the reaction conditions were systematically adjusted and examined. Results indicated that AgNPs could be successfully decorated on the side wall of the ZnO nanowires only by the assistances of SnCl₂. The size and density of AgNPs were affected by both the concentration of silver nitrate and the irradiation time. With optimized condition, the prepared 3D substrates provided an enhancement factor approaching 7 orders of magnitude compared with conventional Raman intensity. Copyright © 2014 John Wiley & Sons, Ltd.     

Nanocomposite of polypyrrole and alumina nanoparticles as a coating filler for the corrosion protection of aluminium alloy 2024-T3

Aluminium (Al) alloys such as 2024-T3 are widely used in industry as low weight construction materials with excellent mechanical properties. Until recently corrosion protection of Al alloys was carried out with coatings containing hexavalent chromium (Cr⁶⁺). However, Cr⁶⁺ is a health and environmental hazard and has to be replaced. Intrinsically conducting polymer (ICP) technology is the promising alternative to chromate coating technology because of good corrosion protection properties of ICPs, their moderate cost and good environmental compatibility. In this paper we report successful attempt of making nanocomposite comprised of alumina nanoparticles modified by polypyrrole for the purpose of corrosion protection of Al alloy. Modified nanoparticles were used as coating filler. Coating was designated to perform as an active barrier to electrolyte diffusion. Properties of the coating were examined by adhesion test, electrochemical impedance spectroscopy, X-rays elemental analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy.     

Ultrasound mediation for one-pot sonosynthesis and deposition of magnetite nanoparticles on cotton/polyester fabric as a novel magnetic,photocatalytic, sonocatalytic,antibacterial and antifungal textile

A magnetic cotton/polyester fabric with photocatalytic, sonocatalytic, antibacterial and antifungal activities was successfully prepared through in-situ sonosynthesis method under ultrasound irradiation. The process involved the oxidation of Fe²⁺ to Fe³⁺ via hydroxyl radicals generated through bubbles collapse in ultrasonic bath. The treated samples were analyzed by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry. Photocatalytic and sonocatalytic activities of magnetite treated fabrics were also evaluated toward Reactive Blue 2 decoloration under sunlight and ultrasound irradiation. Central composite design based on response surface methodology was applied to study the influence of iron precursor, pH and surfactant concentration to obtain appropriate amount for the best magnetism. Findings suggested the potential of one-pot sonochemical method to synthesize and fabricate Fe₃O₄ nanoparticles on cotton/polyester fabric possessing appropriate saturation magnetization, 95% antibacterial efficiency against Staphylococcus aureus and 99% antifungal effect against Candida albicans, 87% and 70% dye photocatalytic and sonocatalytic decoloration along with enhanced mechanical properties using only one iron rich precursor at low temperature.     

Effects of ultrasound irradiation on Au nanoparticles deposition on carbon-coated LiNi0.5Mn1.5O4 and its performance as a cathode material for Li ion batteries

LiNi_0.5Mn_1.5O₄ (LMNO) has attracted considerable attention as a Li-ion battery cathode material, owing to its high discharge voltage of 4.7 V (vs. Li/Li⁺) and high energy density. However, the electronic conductivity of LMNO is low, resulting in a low discharge capacity at high current density. To overcome this limitation, we deposited Au nanoparticles (NPs), which have a high conductivity and chemical stability at high battery voltages, on carbon-coated LMNO (LMNO/C) using ultrasound irradiation. Consequently, Au NPs that are ∼16 nm in size were deposited on LMNO/C, and ultrasound irradiation was reported to disperse the NPs on LMNO/C more effectively than stirring. Furthermore, the deposition of Au NPs on LMNO/C using ultrasound irradiation improved its electronic conductivity, which is related to an increase in the discharge capacity due to the reduction of Ni⁴⁺ to Ni²⁺ in LMNO/C at a high current density.