Papers by Keyword: Layer-by-Layer Self-Assembly

Abstract: The transparent nanosized TiO₂ film was fabricated by a layer-by-layer assembly method starting from the highly dispersed anatase oppositely charged TiO₂ nanoparticles without using anypoly electrolytes. The positively charged TiO₂ nanoparticles (ca.7 nm) and negatively charged TiO₂ nanoparticles (ca.7 nm) were synthesized by a subsequently hydrothermal process. Field-emission scanning electron microscopy, UV-vis transmittance spectra and Contact angle measurement were employed to characterize TiO₂films.By the treatment of 500°C for 2hrs, the nanostructured TiO₂ film showed a water contact angle of below 10°andthe relative transmittance to quartz glass of over 90%.

Abstract: Encapsulated carbon black pigment was prepared by layer-by-layer self-assembly method. The RX8002 carbon black particles were well coated by a SiO₂ layer, which makes it has good connection with ZrSiO₄ layer. Meanwhile, dense ZrSiO₄ layer was coated on the C@SiO₂ particles surface to prevent the corrosive effects of glaze. The structure and morphology of samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The chromatic value of the pigments was measured by the CIE color system. The results show that the carbon black particles can be well coated by SiO₂ and ZrSiO₄ layer. When the TEOS/H₂O ratio is 0.002 and the ZrSiO₄/C ratio is 0.71, the chromatic value of the encapsulated carbon black pigment is 42.55, and the pigment has a good stability in glaze.

Abstract: HgS nanoparticles were loaded on the silica microspheres by an improved layer-by-layer self-assembled technique following low temperature heat-treatment. The optical properties of HgS nanoparticles on the silica microspheres were characterized with UV-vis and fluorescence spectra. The results suggested that the HgS nanoparticles were formed on the silica microspheres, and the average size of particles was approximately 15 nm. The direct band gap of the loaded HgS nanoparticles was calculated to be 2.4 eV from the absorption spectrum, which was blue-shifted by 0.4 eV from its bulk value due to quantum size effect. The photoluminescence showed a broad emission around 440 nm from sulfur vacancies. These results indicate that the optical properties of HgS nanoparticles loaded on the silica microspheres are similar to those of free HgS nanoparticles, which is encouraging for potential applications.

Abstract: Electrostatic layer-by-layer (LbL) self-assembly is widely used in sequential adsorption of nanometer-thick monolayers of oppositely charged polyelectrolytes to form a multi-layer film with molecular-level control over the architecture. To offer functional material for the potential application, this paper exploits PDDA and PSS as polycation and polyanion for LbL self-assembly to fabricate polyelectrolyte nanocomposite films. The preparation and film-growing mechanism is investigated under the influences of multi-factor such as polyelectrolyte concentration, ionic strength, and assembling duration using quartz crystal microbalance (QCM). The research results indicate the formation mechanism of multi-layer PDDA/PSS films and offer fundamental basis for the optimum preparation of polyelectrolyte films.

Abstract: In this paper, Old Corrugated Container (OCC) was used as the raw material for making paper. The layer-by-layer (LBL) assembly process of creating highly structured thin films was adopted to modify the surface of OCC fibres. Poly dimethyldiallylammonium chloride (PDADMAC) and hydroxyethyl cellulose (HEC) have been used to build up polyelectrolyte multilayers on OCC fibres under a certain condition. Zeta potential analyzer was used to monitor the dynamic adsorption of PDADMAC and HEC with different amount on OCC fibers. Strength measurements of the sheets including tensile index and bursting index were also determined, showing a significant improvement in physical strength with the increase of adsorbed layer number. Compared with not being processed sheets, tensile index and bursting index of sheets from treated fibre with polyelectrolyte multilayers were raised by 36.65% and 49.50%, respectively. Furthermore, filtration time analysis of OCC fibre suspension showed that the built up of PDADMAC and HEC on OCC fibres could improve the fiber-fiber joint strength of joints from polymer-treated fibers, which made the filtration time decline from 30 s to 10.6 s. In addition, SEM was introduced to observe the morphology of the PDADMAC/HEC multilayers. The images revealed that the surface of OCC fibres structured a film like plastic, which could be ascribed to the adsorption layer of polyelectrolyte.

Abstract: Layer-by-layer self-assembly technology has been widely used and developed recently. However, most assembly was directly carried out using polyamions and polycations which is simply based on electrostatic force. In this work, a coordination multilayer with PS ultrafiltration (UF) membrane as substrate was explored by the alternate deposition of a transition-metal-containing polyelectrolyte and a ligand-containing polymer via the formation of complexes. Desalination experiments showed that for single salt solution filtration, the prepared metal-ligand-coordinated multilayer membrane has a 85% rejection of Na2SO4 and a solution flux of 60 L/m2h at 1.0MPa, while the rejection of NaCl was only 20% and the solution flux was about 85 L/m2h at the same pressure. Continuous test indicated that the performance of the membrane is basically unchanged during the two weeks, so the prepared membrane has excellent stability and resistance to swelling.

Abstract: Nanocomposite films containing Au nanoparticles were fabricated by alternating adsorption of poly(diallydimethyl ammonium chloride) (PDDA) and HAuCl4 using layer-by-layer self-assembly technique and subsequent in situ electrochemical reduction of the AuCl4- ions. The composition and properties of the composite films were characterized by ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV).The UV-vis characteristic absorbances of PDDA and Au increase almost linearly with the number of bilayers, which suggests a progressive deposition with almost an equal amount of the PDDA and Au in each cycle. X-ray photoelectron spectroscopy further confirms the presence of the main components (such as PDDA and Au) of the nanocomposite films. Furthermore, the nanocomposite films also exhibit good electrocatalytic activity for the oxidation of ascorbic acid (AA), which may be used in electrochemical biosensors.

Abstract: We demonstrate a carbon nanotube based high-resolution biosensor for acetylcholine sensing. Carbon nanotubes are deposited on a silicon wafer in a repeated fashion with layer-by-layer nano self-assembly technique. With nano-assembled acetylcholinesterase molecules on the surface, the carbon nanotube biosensor is capable of detecting acetylcholine at an ultra-low concentration of 100 pM. The sensitivity of the acetylcholine sensor is measured as 7.2 µA/decade. The real-time measurement shows the response time of the biosensor is approximately 6 sec. Both the carbon nanotube film and the acetylcholinesterase film are crucial in the sensing process. Due to its high resolution, fast response, small size, and low cost, the carbon nanotube biosensor has tremendous potential for applications in medical research and clinical diagnosis.

Abstract: A novel nanosized multilayer film containing polyoxometalate anion with a pendant supportligand α-[SiW11O39Co(H3P2O7)]7- (abbr. SiW11Co-P2O7) and poly(diallyldimethyl ammonium chloride (PDDA) was fabricated by layer-by-layer self-assembly. The multilayer film was characterized by XPS, UV-vis, AFM and ESR. The mean interface roughness was about 2.0 nm, calculated from an area of 0.5 × 0.5 μm2. The electrochemical property was studied by the cyclic voltammetry, the results indicating that the self-assembly film exhibited favorable electrochemical behavior of polyoxometalate.

Abstract: The ultra-thin film composed of chitosan (CS) and sulfated chitosan (SCS) was assembled on the titanium oxide surface by layer-by-layer (LBL) self-assembly methods. The titanium oxide film was treated by NaOH solution, followed by successively dipping the substrates in 5mg/ml sulfated chitosan (SCS) and 5mg/ml chitosan (CS) solutions alternatively, We hypothesized that this biologic coating may have the property of good biocompatibility, antibacteriostatic effect, anticoagulant activitves and enhancing sell biocompatibility.