Papers by Keyword: Self-Assembled

Abstract: In this paper a new robust and precise ordering criterion for the characterization of self-assembled hexagonal lattice like Anodic aluminum Oxide (AAO) has been proposed. In order to unveil the mechanism for the self-organization process and deposition techniques in AAO, it is necessary to be able to have a quantitative objective criterion to evaluate the amount of order through every SEM sample of a material. Most of methods in the literature are only able to characterize the extreme case of highly ordered or lowly ordered texture well. But the real challenge is in characterizing the order of medium-ordered texture which is the dual concept of near-regular texture analysis in image processing. Our method based on more advanced image processing techniques, Gabor filter-bank, are able to characterize medium-ordered AAO textures more precisely. Our idea is also able to define the domain's place of the AAO image.

Abstract: In₂O₃ nanorods have been fabricated on Cr comb-shaped interdigitating electrodes using thermal evaporation of the mixed powders of In₂O₃ and active carbon with Au catalysts. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The self-assembly grown sensors of In₂O₃ nanorods have excellent performance in sensor response to alcohol concentration of 500 ppm under operated temperature of 300°C.

Abstract: The Ag nanoparticles was prepared by reduction of silver nitrate with sodium citrate, and the APS monolayers was self-assembled with 3-Aminopropyltrimethoxysilane (APS) on the monocrystalline silicon surface. Then, Ag/APS molecular self-assembled film was formed with Ag nanoparticles and APS membrane by liquid method. The chemical structure and morphology of the Ag nanoparticles and self-assembled film were investigated by AFM, XRS and IR. Meanwhile, the friction performances of self-assembled film was also investigated. The results shown that the Ag nanoparticle have the morphology of spherical particles with an average particle size of ca. 65 nm in diameter which were successful assembled on the surface of APS film and partially oxidized into Ag₂O. The friction coefficient of the Ag-APS molecular self-assembled film has been decreased with the assembled time extened while the wear rate has improved.

Abstract: A novel reagentless H₂O₂ biosensor based on ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF₆) functionalized nano-gold as the biocompatible interface of Cytochrome C (Cyt c) by self-assembled method was proposed. The immobilized Cyt c showed direct electrochemistry and displayed an excellent electrocatalytic response to the reduction of H₂O₂ without the aid of any electron mediator. Under optimal experimental conditions, the as-prepared biosensor showed a wide linear response to H₂O₂ in the range of 0.23 µM to 3.0 mM with a detection limit of 0.12 µM (S/N = 3). The resulting biosensor can reached 95% of steady-state current within 5 s. The K^app_m value for H₂O₂ was found to be 1.2 mM.

Abstract: Octadecyltrichlorosilane (OTS) was prepared on glass substrate to form self-assembled monolayer (OTS-SAM). The OTS-SAM was then UV-irradiated to endow the film with good chemisorption ability. Zirconia films were formed on silanol SAM by the LPD method. The phase structure and surface configuration of the zirconia films were studied by XRD and SEM respectively. The XRD results indicate that the as-deposited ZrO2 thin films are pure tetragonal phase after being annealed at 500°C for 1 h. SEM images show the zirconia film is uniform, but not very compacted.

Abstract: In this article, (NH4)2TiF6, SrNO3 and H3BO3 were used as raw materials to prepare the precursor solution with the ratio of AHFT/SN/BA=1:1:3. The thin films of SrTiO3 were fabricated on the functional silicon substrates (100) by self-assembled monolayers (SAMs) with the liquid phase deposition (LPD). This article also studied the effects of wet state and the deposition temperature of the precursor solution before and after the functionalization of silicon substrate on the thin film growth. The results indicated that after the immersion in OTS for 30min, the surface contact angle of the silicon substrate changed from 24.64° to 100.91°. The substrate appeared hydrophobic property and it was irradiated by UV light for 30min. Then the surface contact angle of the substrate decreased to 5.00°. The substrate appeared hydrophilicity. The concentration of the precursor solution was 0.025 mol/L, the deposition temperature was 40°C and the deposition time was 9h, which were all helpful to SrTiO3 crystallization. XRD and SEM were used to characterize the physical phase of thin film and surface morphology at 600 °C with annealing and heat retaining for 2h. The results indicated that the thin film prepared by the mono-crystal Si substrate was SrTiO3 thin film with better crystalline. On the crystal surfaces of (110), (100), (200) and (211), there appeared the obvious diffraction peaks. The SrTiO3 grains on the surface had the clear outline and were regular and long columnar crystals.

Abstract: Urchin-like CuO, consisting of closely packed nanorods with a diameter of 10nm, have been successfully synthesized by a poly(ethylene glycol) (PEG)-assisted hydrothermal route at low temperature of 100°C. The as-obtained Urchin-like CuO were thoroughly characterized by X-ray diffraction (XRD) study, Field emission scanning electron microscope (FESEM), High-resolution transmission electron microscopy (HRTEM) and Gas sensor measurements. From the XRD pattern, all the peaks detected can be assigned to CuO in a monoclinic structure with lattice parameters a=4.662, b=3.416 and c=5.118 (JCPDS card no. 65-2309). The FESEM and TEM showed that the diameter of the urchin-like CuO sphere is about 1µm. Further investigation of the formation mechanism reveals that the PEG-assisted hydrothermal process is vital to the formation of 3D structures. Besides the template function, PEG often plays as a reductant while reacting with Cu(+2). In our case, no impurity peaks of Cu2O were observed in the XRD pattern, implying that PEG did not reduce Cu(+2) to Cu(+1). We attribute this to the high concentration of PEG. The sensor based on the urchin-like CuO nanostructures exhibit excellent ethanol-sensing properties at reduced working temperature (200°C), which shows a sensitivity two times higher than that of CuO particles(about 100nm, made from calcinations of Cu(NO3)2 at 400°C). The enhancement in sensitivity of the as-prepared CuO may be contributed to the fancy 3D nanostructures.

Abstract: Carbon nanotubes (CNTs) were functionalized using a simple method of heat treatment under oxygen atmosphere followed by an immersion in a tin nitrate aqueous solution. And well-dispersed SnOx nanodots were decorated on the surface of CNTs. X-ray photoelectron spectroscopy (XPS) analysis showed that the O/C ratio increases with oxygen-treated time. The distribution of carbon-containing functional groups on the CNTs surface, i.e., C−C, C−O, C=O, O−C=O, and π−π* shake up bonds can be identified and deconvoluted by a symmetrical Gauss function. The contact angle of H2O and CNTs is dependent on O/C ration. The relationships between the fraction of carbon-containing functional groups and various oxygen treatment times are also discussed.

Abstract: As a “bottom-up” approach to nanostructures for nanofabrication, self-assembled block copolymer thin films have received much attention not only thanks to the scale of the microdomains but also due to the convenient shape tunability. In order to realize applications of self-assembled block copolymer thin films in nanotechnologies, control over microdomain spatial and orientational order is paramount. In this paper, using atomic force microscopy (AFM), we studied systemically nanostructure transitions induced by post-solvent annealing in self-assembled block copolymer thin films. Furthermore, a variety of thin films with well-ordered nanostructures, which can be employed as templates for nanotechnologies, have been realized simply and at low cost.

Abstract: Exciton states in type-II InP/InGaP and GaSb/GaAs self-assembled quantum dots and quantum-dot superlattices subject to a normal magnetic field are calculated. Strain is explicitly taken into account in single particle models of the electronic structure, while an exact diagonalization approach is adopted to compute the exciton states. Strain reverts type II band alignment in InP quantum dots to type I, therefore no transitions between the lowest energy states of different angular momenta are observed. On the other hand, strain increases the barrier for the electron in the conduction band of GaSb/GaAs quantum dots, therefore the exciton, being composed of electron and hole states of various angular momenta, may have a finite angular momentum in the ground state. Consequently, the oscillator strength in the InP single quantum dot and quantum-dot superlattice increases with the magnetic field, while the angular momentum transitions between the bright and the dark exciton states in the GaSb system bring about decay of the oscillator strength when the magnetic field exceeds a certain value.