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Layer-by-layer Self-assembly (layer-by-layer + self-assembly)

Distribution by Scientific Domains

Polymers and Materials Science	80%

Selected Abstracts

Interaction of Zoospores of the Green Alga Ulva with Bioinspired Micro- and Nanostructured Surfaces Prepared by Polyelectrolyte Layer-by-Layer Self-Assembly

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2010
Xinyu Cao
Abstract The interaction of spores of Ulva with bioinspired structured surfaces in the nanometer,micrometer size range is investigated using a series of coatings with systematically varying morphology and chemistry, which allows separation of the contributions of morphology and surface chemistry to settlement (attachment) and adhesion strength. Structured surfaces are prepared by layer-by-layer spray-coating deposition of polyelectrolytes. By changing the pH during application of oppositely charged poly(acrylic acid) and polyethylenimine polyelectrolytes, the surface structures are systematically varied, which allows the influence of morphology on the biological response to be determined. In order to discriminate morphological from chemical effects, surfaces are chemically modified with poly(ethylene glycol) and tridecafluoroctyltriethoxysilane. This chemical modification changes the water contact angles while the influence of the morphology is retained. The lowest level of settlement is observed for structures of the order 2,µm. All surfaces are characterized with respect to their wettability, chemical composition, and morphological properties by contact angle measurement, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. [source]

Construction of Polycation-Based Non-Viral DNA Nanoparticles and Polyanion Multilayers via Layer-by-Layer Self-Assembly,

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2005
Kefeng Ren
Abstract Summary: The multilayers of polycation-based non-viral DNA nanoparticles and biodegradable poly(L -glutamic acid) (PGA) were constructed by a layer-by-layer (LbL) technique. Poly(ethyleneimine) (PEI) was used to condense DNA to develop non-viral DNA nanoparticles. AFM, UV-visible spectrometry, and TEM measurements revealed that the PEI-DNA nanoparticles were successfully incorporated into the multilayers. The well-structured, easily processed multilayers with the non-viral DNA nanoparticles may provide a novel approach to precisely control the delivery of DNA, which may have great potential for gene therapy applications in tissue engineering, medical implants, etc. A TEM image of the cross section of a (PGA/PEI-DNA nanoparticle)20 multilayer. [source]

Quantum-Dot-Functionalized Poly(styrene- co -acrylic acid) Microbeads: Step-Wise Self-Assembly, Characterization, and Applications for Sub-femtomolar Electrochemical Detection of DNA Hybridization

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
Haifeng Dong
Abstract A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene- co -acrylic acid) microbeads with CdTe quantum dots. CdTe-tagged polybeads are prepared by a layer-by-layer self-assembly of the CdTe quantum dots (diameter,=,3.07,nm) and polyelectrolyte on the polybeads (diameter,=,323,nm). The self-assembly procedure is characterized using scanning and transmission electron microscopy, and X-ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum-dot coverage is (9.54,±,1.2),×,103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe-tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin,biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square-wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier-bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L,1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events. [source]

Vapor Sorption and Electrical Response of Au-Nanoparticle, Dendrimer Composites,

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007
N. Krasteva
Abstract Films comprising Au nanoparticles and polyphenylene dendrimers (first and second generation) are deposited onto transducer substrates via layer-by-layer self-assembly and characterized by atomic force microscopy and X-ray photoelectron spectroscopy. Their sorption behavior is studied by measuring the uptake of solvents from the vapor phase with quartz crystal microbalances (QCMs). The resistance of the films is simultaneously monitored. Both sensor types, QCMs and chemiresistors, give qualitatively very similar response isotherms that are consistent with a combination of Henry- and Langmuir-type sorption processes. The sorption-induced increase in relative differential resistance scales linearly with the amount of analyte accumulated in the films. This result is in general agreement with an activated tunneling process for charge transport, if little swelling and only small changes in the permittivity of the film occur during analyte sorption (a first-order approximation). The relative sensitivity of the films to different solvents decreases in the order toluene,,,tetrachloroethylene,>,1-propanol,,,water. Films containing the larger second-generation dendrimers show higher sensitivity than films containing first-generation dendrimers. [source]

Charge Transport in Redox Polyelectrolyte Multilayer Films: The Dramatic Effects of Outmost Layer and Solution Ionic Strength

CHEMPHYSCHEM, Issue 13 2010
Dr. Mario Tagliazucchi
Abstract The redox switching kinetics, that is, charge transfer and transport in layer-by-layer-deposited electroactive polyelectrolyte multilayers is systematically studied with variable-scan-rate cyclic voltammetry. The experiments are performed with films finished in the redox polycation (an osmium pyridine,bipyridine derivatized polyallylamine, PAH-Os) and the polyanion (polyvinyl sulfonate, PVS), in solutions of different electrolyte concentrations. A modified diffusion model is developed to account for the experimentally observed dependence of the average peak potential with the scan rate. This model is able to describe both the redox peak potential and the current, providing information on the electron-transfer rate constants and the diffusion coefficient for the electron-hopping mechanism. While the former does not vary with the ionic strength or the nature of the outmost layer, polyanion-capped films present an electron-hopping diffusion coefficient at low ionic strength that is three orders of magnitude smaller than that for PAH-Os-capped films. The effect is offset at high ionic strength. We discuss the possible causes of the effect and the important consequences for electrochemical devices built by layer-by-layer self-assembly, such as amperometric biosensors or electrochromic devices. [source]