Nano

A review of preparation of chiral carbon nanotubes (CNTs) and carbon nanotube chiral composites is presented. Novel chiral separation science and technology based on CNTs is analyzed and discussed, with the emphasis in two topics. The first topic concerns the possibility of application of chiral CNTs in resolution and chiral sensing. The second topic centers on the subject of enantioseparation based on CNT chiral composites. Despite the crucial functionalization of CNTs using chiral selectors, better resolution could also be achieved by using a mixture of CNTs and optical pure substances as chiral selectors. Due to their ability of improving the degree of enantioseparation, CNTs could find their potential applications in the resolution in the future.

A novel tree-like nano-cadmium sulfide (CdS) with the fractal feature is synthesized by solid-state reaction at room temperature from complex precursor with aminotrimethylenephosphonic acid (ATMP) as ligand. The obtained sample is the crystalline cubic beta cadmium sulfide. The tree is composed of nanorods with an average diameter of ca. 95 nm and a length of up to 100–650 nm. The nanorods grow in the asymmetrical "Y" shape. The amount of ATMP plays an important role in the formation of fractal structure. Nonlinear optical (NLO) measurements by the Z-scan technique exhibit that the tree-like fractal nano-CdS has the third-order nonlinear optical properties of both NLO absorption and NLO refraction with self-focusing effect and the optical limiting performance.

Ultramicrotomy was used to prepare a cross-section of shell-like amorphous SiO₂ spherical particle synthesized by the multistage Stöber method which allowed performing first direct observations of the hierarchical structure of the SiO₂ particle by transmission and scanning electron microscopy. The presence of primary, secondary and tertiary particles forming the inner structure of SiO₂ spheres was established. The use of the small angle scattering of neutrons and synchrotron radiation techniques has enabled to define the size of the primary particles, the fractal parameters of their surface and the bulk density of the SiO₂ spheres.

A sensitive and selective colorimetric biosensor for determination of gentamicin, amikacin and tobramycin was proposed with the unmodified gold nanoparticles (GNPs) as the sensing element. Gentamicin, amikacin and tobramycin can rapidly induce the aggregation of gold nanoparticles and is accompanied by a color change from red to blue. The concentration of gentamicin, amikacin and tobramycin can be determined by using UV-Vis spectrometer. The experimental parameters were optimized with regard to pH, incubation time and the concentration of the GNPs. Under optimal experimental conditions, the linear range of the colorimetric sensor for gentamicin/amikacin/tobramycin were 2.67–33.93 ng mL^-1, 13.33–66.67 ng mL^-1 and 20–180 ng mL^-1, respectively. The corresponding limit of detection (3σ) was 0.354 ng mL^-1, 0.999 ng mL^-1 and 0.579 ng mL^-1, respectively. This assay was simple and used to detect aminoglycoside antibiotics in milk and medicine products.

Zn was firstly used to improve wear resistance of a TA7 (Ti–5Al–2.5Sn) titanium alloy surface by mean of a laser alloying (LA) technique. The synthesis of the hard coating on a TA7 titanium alloy by LA of Co–Ti–Cr–TiB₂–Zn–CeO₂ pre-placed powders was investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). Experimental results indicated lot of the nanocrystals, such as Ti–B/CoZn₁₃ and the amorphous phases were produced in such LA coating. The nucleation and growth of the amorphous phases were retarded by the nanocrystals in a certain extent during the crystallization process of the amorphous phases. Compared with a TA7 alloy substrate, an improvement of the wear resistance was obtained for such LA composite coating.

The Fe₃O₄@C core/shell microspheres were fabricated via a two-step process. Fe₃O₄ microspheres were firstly prepared, and Fe₃O₄@C core/shell microspheres were subsequently fabricated using glucose as a carbon source by a hydrothermal route, in which the thickness of the carbon coating was about 20 nm. The resulting products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The Nitrogen adsorption–desorption isotherms reveal their mesoporous structure and larger BET surface area (62.3 m²g^-1). The Fe₃O₄@C core/shell microspheres possess ferromagnetism and high saturation magnetization (39.2 emu ⋅ g^-1). Bovine hemoglobin (BHb) was used as a model protein to test the adsorption and desorption properties of the Fe₃O₄@C core/shell microspheres. The capacity for BHb adsorption was more than 71.3 mg/g. According to the values obtained in the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay the Fe₃O₄@C core/shell microspheres show a low toxicity. Therefore, the prepared Fe₃O₄@C core/shell microspheres are of great significance for guided site-specific drug delivery.

One of the most commonly used techniques for purification and eventual dispersion of single-wall carbon nanotubes (SWNTs) is oxidation using strong acid and ultrasonication. Literature review reveals that ultrasonication of varying radiation intensities have been used during the acid oxidation, but few have reported whether ultrasonication of different intensities would have different effects on the structure and properties of SWNTs and how the effects are. An investigation of the effects of ultrasonic radiation intensity on SWNTs during oxidation in a mixture of sulfuric and nitric acids was conducted. Ultrasonication using different intensities (50 W, 100 W, 200 W and 300 W) was used. The acid-treated SWNTs were characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, zeta potential test Boehm titration test and Raman spectrum analysis. Data from these experiments showed that high intensities provided stronger oxidizing conditions than lower ones. As ultrasonic intensity increased, larger number of SWNTs were destroyed and consumed to produce carbonaceous impurities, and more defects appeared in the tube walls.

We report a multilayer moisture barrier structure comprised of alternating inorganic aluminum oxide and plasma-polymerized organic layers. The inorganic and organic layers were grown by atomic layer deposition (ALD) and plasma polymerization in vacuum, respectively. The inclusion of plasma-polymerized layers in the multilayer barrier structure enhanced the moisture barrier performance by around 15% for as-deposited samples. After being subjected to 10 000 bending cycles with a bending radius of 2 cm, however, the moisture barrier performance of the multilayer structure was improved by 50% from that of pure inorganic counterpart.

In this paper, we firstly synthesized glycyrrhetinic acid-modified double amino-terminated poloxamer 188 (GA–NH–POLO–NH–GA). The structure of the synthesized compound was confirmed by ¹H-NMR and Fourier transform infrared (FT-IR) spectroscopy. Then the nanoparticles composed of GA–NH–POLO–NH–GA/chitosan (GA–NH–POLO–NH–GA/CTS) were prepared by an ionic gelation process. The characterization of the nanoparticles was measured by dynamic light scattering (DLS) and scanning electron microscope (SEM). The results showed that the nanoparticles were well dispersed with a spherical shape and the particle size was distributed between 100 nm and 300 nm. The cytotoxicity based on MTT assay against cells (QGY-7703 cells and L929 cells) showed that the nanoparticles had low toxicity and good biocompatibility. The encapsulation efficiency and drug loading of 5-fluorouracil-loaded nanoparticles (5-FU nanoparticles) were measured by high-performance liquid chromatography (HPLC) and fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorbance. The encapsulation of 5-Fu-loaded CTS nanoparticles was 12.8% and the drug loading was 2.9%, while the encapsulation of 5-Fu-loaded GA–NH–POLO–NH–GA/CTS nanoparticles was 20.9% and the drug loading was 3.36%. The release profile showed that the GA–NH–POLO–NH–GA/CTS nanoparticles were available for sustained release of 5-Fu. The GA–NH–POLO–NH–GA/CTS nanoparticles have a higher affinity to the QGY-7703 cells, so indicated that the GA–NH–POLO–NH–GA/CTS nanoparticles have the capacity of liver-targeting in vitro.

A novel hierarchical nanostructure of SiO₂ nanowires standing on SiO₂ microwires was synthesized through a catalyst-free thermal evaporation method in nitrogen atmosphere. The SiO₂ nanowires have an average diameter of 100 nm and length of 2 μm, while the diameter of the SiO₂ microwires is around 10 μm and the length is hundreds of micrometers. The photoluminescence spectrum of the SiO₂ hierarchical nanostructure shows stable blue and green emission at 442 nm and 533 nm, respectively. An oxygen-assisted three-step growth mechanism was suggested to interpret the growth of the SiO₂ hierarchical nanostructure.

We present experimental and numerical results of simultaneous surface plasmon polariton (SPP) excitation and in-plane manipulation with random arrays of gold nanoparticles. The recorded images were obtained by using leakage radiation microscopy (LRM) for the excitation wavelength of 633 nm and for different densities of particles. The numerical model makes use of a composed analytic Green dyadic which takes into account near- and far-field regions, with the latter being approximated by the part describing the scattering via excitation of SPP. The LRM optical images obtained are related to the calculated SPP intensity distributions demonstrating that the developed approach can be successfully used in studies of systems of closely spaced arrays.

The effects of oxygen-containing functional groups on the surface roughness of graphene oxide are thoroughly studied using three-dimensional atomic force microscopy images, ball-and-stick model and wire-frame view results. Moreover, X-ray diffraction method and Fourier transform infrared spectroscopy are employed for characterizing the structural and chemical behavior of graphene oxide, respectively. Graphene oxide sheets show a clear concavity on one side when the aggregation of functional groups increased on the other side. This behavior could be the main reason for the surface fluctuation of graphene oxide sheets that is observed in microscopic images. In addition, the individual graphene oxide sheet presents greater values of mean roughness compared to multilayered sheets.