Polyelectrolyte (PE)/gold nanoparticle hybrid films that can be utilized as efficient electrochemical sensors were prepared by infiltrating 4-(dimethylamino)pyridine-stabilized gold nanoparticles (DMAP−AuNP) into PE multilayers preassembled on indium tin oxide (ITO) electrodes. Quartz crystal microgravimetry (QCM) and UV−vis spectroscopy showed that via this infiltration method, composite films with densely packed DMAP−AuNP were obtained. Electrochemical experiments revealed that the presence of gold nanoparticles in the PE multilayers could significantly improve the electron-transfer characteristics of the films, which showed high electrocatalytic activity to the oxidation of nitric oxide (NO). The sensitivity of the composite films for measuring NO could be further tailored by controlling the gold nanoparticle loading in the film.

In summary, a single-phase perovskite anode has been demonstrated with comparable performance in hydrogen to nickel zirconia cermets. An all-perovskite SOFC has been achieved using LSCM as the anode, LSGMCo as the electrolyte, and GSC as the cathode, which minimizes the interface polarization losses across the electrolyte/electrode interfaces. Further investigation is necessary to optimize the materials and electrode microstructure to improve the fuel-cell performance. ExperimentalThe electrolyte La 0.8 Sr 0.2 Ga 0.8 Mg 0.15 Co 0.05 O 3±d (LSGMCo) was prepared by solid-state reaction. La 2 O 3 , SrCO 3 , Ga 2 O 3 , MgO, and CoCO 3 were mixed after drying to remove the absorbed water. The mixture was ball-milled for 30 min in the presence of acetone. After prefiring to decompose the SrCO 3 , the mixture was pressed into a pellet and finally fired at 1500 C for 4 h in air. A single perovskite phase was formed according to the X-ray diffraction (XRD) pattern. Pellets with thickness of 2 mm and 0.6 mm, respectively, were prepared for anode half-cell and whole-cell performance tests. In our electrochemical test set-up [15] some pressure has to be applied to the electrolyte to maintain good sealing. 0.6 mm is the minimum thickness of electrolyte LSGMCo which can resist the applied pressure in this geometry without cracking during the test due to its poor mechanical strength. (La 0.75 Sr 0.25 ) 0.95 Cr 0.5 Mn 0.5

911.[35] The nanocrystal powder is dispersed in a suitable amount of amine, such as octylamine, and stirred for several days. The nanocrystals are precipitated with dimethylformamide (DMF) and the procedure repeated. [5±7,9] inorganic oxides, [10,11] semiconductors, [12±15] polymers, [8,16,17] and carbon [18±20] have been prepared. Methods used to synthesize NTs in the pores of template membranes include electroless metal deposition, [9] sol±gel chemistry, [10,11] electrochemical deposition, [5±7] chemical vapor deposition, [21] and melting or dissolving polymer into the pores. [8,16,17] The size and the structural properties of the materials prepared by membrane templating are determined by the morphology of the templates employed. Highly-ordered nanowire and NT arrays can be obtained by using alumina membranes that contain highly-ordered pores.[7]The layer-by-layer (LbL) method, [22,23] recognized as a premier technique for the preparation of multilayer films, largely due to its low cost, simplicity, and versatility, also has potential for the preparation of designed nanotubes. This technique, which primarily exploits the electrostatic attraction between oppositely charged species deposited from solution, has been widely used to prepare multilayer films, both on planar supports [22±25] and, recently, on colloid particles.[26±31] The LbL technique permits the coating of substrates of various shapes and sizes with uniform layers of varying composition (polymers, biological macromolecules, dyes, and nanoparticles) and controllable thickness (nanometer resolution). However, previous studies have employed mostly nonporous substrates for coating, with relatively few reports focusing on the use of highly porous supports.[32±38] For example, polyelectrolyte (PE)/semiconductor nanoparticle (CdTe NPs) multilayers have been deposited onto macroporous (inverse opal) titania structures by the LbL method to yield heterogeneous inverse opaline materials. [32] In other work, Bruening and co-workers prepared PE multilayers on top of alumina membranes with pore sizes of~20 nm by the LbL method for ion transport investigations. [33] These studies showed that the underlying pores of the membranes were not ªcloggedº with PE, suggesting small amounts of PE were deposited in the pores of the alumina membranes, with a thin film forming on top of the membrane after the deposition of five PE bilayers. [33] PreviousLbL studies have not emphasized PE coating of the pores of membrane templates, and moreover, they have not dealt with the possible preparation of nanotubes from LbL-coated porous templates.In this work, we report the LbL templating of porous membranes to produce PE and PE/nanoparticle (NP) hybrid NTs. PC membranes containing cylindrical pores of diameter 400 nm and a pore depth of 10 lm were used. The procedure for preparation of the NTs involves three main steps ( Fig. 1): 1) LbL deposition of oppositely charged PEs (or PEs and nanoparticles) onto the membranes, including the inner surfaces (i.e., pores); 2) mechan...

Mesoporous silicas (MS), porous materials with extremely high surface areas and pore sizes in the range of 2 to 50 nm, have attracted significant interest since being reported in the early 1990s. [1,2] Owing to their unique pore structures, these materials have been utilized as hosts for the template synthesis of various materials, including metal, [3] metal oxide, [4] carbon, [5] and polymer [6] replicas. In a typical synthesis strategy, the constituent materials (e.g., metal precursors, sucrose, organic monomers) are infiltrated into the mesopores. Reduction, carbonization, or cross-linking reactions are then performed to obtain an interconnected network, and the silica template is removed by dissolution. Despite these studies, there has been no report on the sequential infiltration and coating of MS materials with preformed polymers for the fabrication of controlled porous polymer structures. Porous polymer materials, especially in particulate form, are of interest in a diverse range of applications, including drug delivery, molecular separation technology, and as hosts for chemical synthesis. [7] A facile approach for coating MS is to exploit electrostatic interactions between the MS support and charged polymers (polyelectrolytes, PEs) through solution self-assembly. Sequentially depositing PEs of opposite charge by the layerby-layer (LbL) technique would potentially permit the formation of PE multilayers inside the MS pores. Since its introduction in 1991, [8,9] the LbL method has been widely used to deposit multilayers of various materials (such as, polymers, enzymes, nanoparticles, dyes) on both planar [10] and colloidal [11] supports. More recent studies have focused on the use of porous substrates, such as macroporous titania, [12] polycarbonate membranes, [13] alumina membranes, [14] and porous calcium carbonate microparticles. [15] However, there has been no report of the LbL assembly of PEs in MS structures and, more specifically, of the LbL MS-templated formation of porous materials with interconnected polymer networks.

Polydopamine is a dark brown-black insoluble biopolymer produced by autoxidation of dopamine. Although its structure and polymerization mechanism have not been fully understood, there has been a rapid growth in the synthesis and applications of polydopamine nanostructures in biomedical fields such as drug delivery, photothermal therapy, bone and tissue engineering, and cell adhesion and patterning, as well as antimicrobial applications. This article is dedicated to reviewing some of the recent polydopamine developments in these biomedical fields. Firstly, the polymerization mechanism is introduced with a discussion of the factors that influence the polymerization process. The discussion is followed by the introduction of various forms of polydopamine nanostructures and their recent applications in biomedical fields, especially in drug delivery. Finally, the review is summarized followed by brief comments on the future prospects of polydopamine.

Infrared stimulation offers an alternative to electrical stimulation of neuronal tissue, with potential for direct, non-contact activation at high spatial resolution. Conventional methods of infrared neural stimulation (INS) rely on transient heating due to the absorption of relatively intense laser beams by water in the tissue. However, the water absorption also limits the depth of penetration of light in tissue. Therefore, the use of a near-infrared laser at 780 nm to stimulate cultured rat primary auditory neurons that are incubated with silica-coated gold nanorods (Au NRs) as an extrinsic absorber is investigated. The laser-induced electrical behavior of the neurons is observed using whole-cell patch clamp electrophysiology. The nanorod-treated auditory neurons (NR-ANs) show a significant increase in electrical activity compared with neurons that are incubated with non-absorbing silica-coated gold nanospheres and control neurons with no gold nanoparticles. The laser-induced heating by the nanorods is confirmed by measuring the transient temperature increase near the surface of the NR-ANs with an open pipette electrode. These findings demonstrate the potential to improve the efficiency and increase the penetration depth of INS by labeling nerves with Au NRs and then exposing them to infrared wavelengths in the water window of tissue.

The usage of gold nanoparticles (Au NPs) in biological applications has risen significantly over the last 10 years. With the wide variety of chemical and biological functionalization available and their distinctive optical properties, Au NPs are currently used in a range of biological applications including sensing, labeling, drug delivery, and imaging applications. Among the available particles, gold nanorods (Au NRs) are particularly useful because their optical absorption can be tuned across the visible to near infrared region. Here, we present a novel application of Au NRs associated with low power laser exposure of NG108-15 neuronal cells. When cells were irradiated with a 780 nm laser, the average number of neurons with neurites increased. A similar stimulatory effect was observed for cells that were cultured with poly-(4-styrenesulfonic acid)-coated and silica-coated Au NRs. Furthermore, when the NG108-15 cells were cultured with both bare and coated Au NRs and then irradiated with 1.2-7.5 W/cm(2) at 780 nm, they showed a neurite length increase of up to 25 µm versus control. To the best of our knowledge, this effect has never been reported before. While the pathways of the stimulation is not yet clear, the data presented here demonstrates that it is linked to the absorption of light by the Au NRs. These initial results open up new opportunities for peripheral nerve regeneration treatments and for novel approaches to addressing central nervous system axons following spinal cord injury.

Porous polycarbonate (PC) membranes with pore diameters of either 400 or 100 nm were used as supports for the layer-by-layer deposition of peroxidase-poly(sodium 4-styrenesulfonate) complexes [(POD-PSS) c ] and oppositely charged poly(allylamine hydrochloride) (PAH) to prepare high-surfacearea thin films for biocatalysis. Formation of the multilayer films was verified by scanning electron microscopy and transmission electron microscopy following dissolution of the porous PC template to generate POD/polyelectrolyte (PE) tubes. An average thickness of ∼5 nm was calculated for each (POD-PSS) c /PAH bilayer, as determined from microscopy images. The activity of the POD/PE multilayer films was found to be dependent on the amount of enzyme in the film (which is determined by the number of (POD-PSS) c layers deposited) and the total membrane surface area. Films deposited on the PC membranes with 100-nm-diameter pores showed maximum bioactivity at five (POD-PSS) c layers. Beyond this layer number the total membrane activity decreased sharply, which is attributed to membrane pore blockage. Films deposited on PC membranes with pore diameters of 400 nm showed regularly increasing bioactivity up to seven (POD-PSS) c layers, with a plateau in activity observed thereafter. Activity enhancements of up to almost an order of magnitude larger were observed for the enzyme films deposited on the PC membranes (e.g., 100-nm pore diameter membranes with 4% porosity), compared with identical films formed on nonporous supports (e.g., quartz slides) with the same geometrical area. The reported method for the preparation of membrane-supported biocatalysts provides a viable approach for the generation of high-enzyme-content thin films with tailored bioactivity.