Journal of Nano Research Vol. 25

Abstract: LiCu_xMn_1-xPO₄/C nanorods are successfully prepared by a simple solvothermal process followed by calcination of the precursor LiCu_xMn_1-xPO₄ and sucrose. The effects of dopant and carbon coating on the physical and chemical characteristics of LiMnPO₄ are investigated. The results show that Cu successfully entered into the lattice of LiMnPO₄, and induced a decrease in the lattice parameters. A thin layer of carbon coating with an average thickness of 20 nm is formed on the surface of LiCu_xMn_1-xPO₄ particle. We also observe that the LiCu_xMn_1-xPO₄/C nanorods have higher electronic conductivity (5.5139×10^-4S cm^-1) and initial discharge capacity (87.5 mAh g^-1 at 0.5C) compared with pristine LiMnPO₄. Based on the results above, the developed nanocomposites could have potential applications in lithium-ion batteries.

Abstract: In this study, the antioxidant activity and antimicrobial effect of tellurium dioxide nanoparticles (TeO₂NPs) sols were evaluated by oxygen radical absorbance capacity (ORAC) and agar diffusion bioassay method, respectively. The results of ORAC demonstrated that the antioxidant activity of TeO₂NPs sols was in a dose-dependent manner and TeO₂NPs-gallic acid sol showed stronger antioxidant activity than TeO₂NPs-acetic acid sol due to the synergistic antioxidant effect of gallic acid and TeO₂NPs. On the other hand, the results of agar diffusion bioassay method demonstrated that the antimicrobial effect of TeO₂NPs-acetic acid sol was stronger than that of TeO₂NPs-gallic acid sol and the two kinds of TeO₂NPs sols could evidently inhibit the growth of some gram negative bacteria and gram positive bacteria which lack nitrate reductase. The antimicrobial mechanism of the TeO₂NPs sols might be similar to that of tellurite.

Abstract: Gold nanoparticles with an average diameter of ~15.5 nm as measured via TEM were functionalised with various amounts of thiol-terminated 5000MW poly (ethylene glycol) (0-37.75 μg/ml), or with a mixed monolayer of thiol-terminated BODIPY and poly (ethylene glycol) (PEG) in various ratios. BODIPY is a fluorescing molecule which was used here as a model payload, while PEG was added to the surface in order to increase nanoparticle stability and biocompatibility. It was observed that the gold nanoparticle surface saturates with PEG at a loading rate of ~15 wt%. Glutathione (GSH) is an antioxidant that occurs as high concentrations inside cells and this can be used to trigger therapeutic payload release therein. The release of BODIPY from nanoparticles functionalised with a mixed monolayer of PEG and BODIPY was investigated at typical intracellular glutathione concentrations. The release profiles were fitted using zero, first order, Higuchi and Reciprocal Powered Time (RPT) models. It was observed that BODIPY release from the surface of nanoparticles capped only with BODIPY and PEG was best described by the RPT and Higuchi models, suggesting diffusion and diffusion-dissolution controlled release. However, the release profile of the nanoparticles capped only with BODIPY did not fit the expected profile due to agglomeration effects. The ratio of BOBIPY to PEG on the surface had a dramatic effect on the release rate. The predicted time to release 50% of the payload compound from the gold nanoparticles displayed a ~500 fold increase for a mixed monolayer prepared with 0.5-18.75 μg/ml of BODIPY-PEG compared to nanoparticle samples prepared with 1.5-6.25 μg/ml of BODIPY-PEG.

Abstract: Electrokinetic potential (zeta potential) is a characteristic parameter for description of the surface chemistry of solid flat materials and it can be used for a fast analysis of materials modified by different chemical or physical methods. Due to its sensitivity, zeta potential is able to distinguish surface modified by coating with monolayers of various materials or nanostructures created after plasma treatment. Also metal nanostructures deposited on surfaces can be characterized by zeta potential. It can also be used for isoelectric point determination of materials. We present data on zeta potential in 0.001 mol/dm³ KCl at constant pH7.0 and also in pH range (2.5-7.0) for isoelectric point determination for pristine polymers PET, PTFE, PS, LDPE, HDPE, PLLA, PVF, PVDF, PMP and polyimides (Upilex R, Upilex S, Kapton). The zeta potential of selected polymers, modified by plasma and by chemical coatings (e.g. by biphenyldithiol or polyethyleneglycol) or by gold deposition was measured too. Zeta potentials of these modified materials were also studied to confirmation that electrokinetic analysis is acceptable method for their fast description.

Abstract: Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiol (4,4-bifenyldithiol, BFD)) to create thiol (-SH) groups on polymer surface. This short dithiol is expected to be fixed via one of-SH groups to radicals created by the plasma treatment on the PET surface. Free-SH groups are allowed to interact with Au nanoparticles. Xray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Electrokinetic Analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the samples were studied by Atomic Force Microscopy (AFM).The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on modified surface in the case of bifenyldithiol pretreatment. The rigid molecule of biphenyldithiol is bounded via only one-SH group to the modified PET surface and the second one remains free for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface.

Abstract: Based on silicon on insulator (SOI) technology [, a monocrystalline membrane is fabricated, in which a buried silicon dioxide layer in the silicon material is the sacrifice layer for the cavity. The membrane is a monocrystalline silicon top layer which contains nanoholes for creating the cavity in the buried oxide (BOX). To encapsulate the cavity the holes are sealed by using different techniques like non-stressed plasma-enhanced chemical vapour deposited (PECVD)-nitride and-oxide, thermal oxidation and evaporation of aluminum. To determine the sticking behavior of the membrane different sizes of membranes are fabricated and compared due to their sticking behavior. The experimental result shows that a membrane, having the size of 25 μm × 25 μm or below, has a perfect non-sticking behavior and can be used for further fabrication (cf. Fig. 8). For comparison, Figure 9 shows a membrane which delivers sticking behavior. The knowledge of this work can be widely used for several applications that need a cavity with a monocrystalline membrane like an absolute pressure sensor with a fully integrated CMOS-circuit on top of it [. This delivers a large variety of possibilities for novelty MEMS devices in different fields of research.

Abstract: LaB₆/ITO films were prepared by magnetron sputtering technique on borosilicate glass substrates. The transmittance of ITO and LaB₆/ITO films was analyzed by using UV/VIS spectrophotometer, whereby the sheet resistance of the ITO films was measured by four point probes. The effect of temperature and post-annealing processes on ITO film properties optimizing UV transparency and sheet resistance were investigated in detail. ITO films with an optimized thickness of 31 nm exhibited a low sheet resistance of 64 Ω/sq and a high ultraviolet transmittance of 81% at a wavelength of 365 nm. The additional LaB₆ layer controls the UV transmittance behavior of the bilayer structure of LaB₆/ITO by improving the photon absorption with thicker LaB₆ films. The work function of LaB₆ (32 nm)/ITO films with a value of 4.98 eV was measured by ultraviolet photoelectron spectroscopy (UPS).

Abstract: Cu and Ni from CuNi metallic targets (composition 20-80 and 46-54 at.%) are deposited on Corning glass, quartz and the native oxide of Si (100) wafers by direct current magnetron sputtering in a high vacuum chamber (base pressure 5 x 10^-5 mbar). The CuNi films, with thickness 40 200 nm, are post annealed at temperatures 400 - 500 °C in a furnace under atmospheric air in order to be fully oxidized. The structure of the films is studied by x-ray diffraction experiments. Phase separation of the oxides is evident. The optical properties are studied via ultraviolet-visible light absorption spectroscopy. The spectra of CuNi-oxide films are compared with the spectra of the pure CuO and NiO films. Features originating from both CuO and NiO are detected in the spectra of the CuNi-oxide thin films.

Abstract: Thin films composed of titanium nitride doped with silver were deposited by DC reactive sputtering, with Ag contents varying between 0 and 50 at.%. The as-deposited samples were subjected to vacuum annealing treatments, with a range of temperatures varying from 200 to 500 °C, in order to study the morphological and structural changes that may occur. The as-deposited samples showed three main zones of basic characteristics, which differ both in terms of morphology and structural features. By increasing the annealing temperature, the thermodynamic stability is accelerated, giving rise to (i) a uniform dispersion of silver particles at 200 °C; (ii) the start of segregation at 300 °C; (iii) at 400 °C the coalescence of the segregated Ag particles takes place and finally (iv) at 500 °C the formation of large Ag clusters is evident, particularly within the zone that comprises the samples with higher Ag content. In addition to corroborate the presence of free Ag in Ag:TiN thin films, the increasing annealing temperature promotes the improvement of the coatings crystallinity, as well as Ag grain growth.