Precursor Customized Assembly of Wafer-Scale Polymerized Aniline Thin Films for Ultrasensitive NH3 Detection.

2D conducting polymer thin film recently has garnered numerous interests as a means of combining the molecular aggregate ordering and promoting in-plane charge transport for large-scale/flexible organic electronics. However, it remains far from satisfactory for conducting polymer chains to achieve desirable surface topography and crystallinity due to lack of control over the precursor-involved interfacial assembly. Herein, wafer-size polyaniline (PANI) and tetra-aniline thin films are developed via a controlled interfacial synthesis with customized surface morphology and crystallinity through two typical aniline precursors selective polymerization. Two crucial competing assembly mechanisms, a) direct interfacial polymerization, b) solution polymerization and subsequent interfacial assembly, are investigated to play a vital role in determining elemental chain length and aggregate architecture. The optimal PANI thin film manifests ultraflat surface topography and unambiguous crystalline domains, which also enabling fascinating ammonia sensing capability with 31.4% ppm-1 sensitivity, fast response time (88 s) with astonishing selectivity, repeatability, and recovery capability. The thus-demonstrated strategy with wafer-scale processing potential and flexible microdevice offers a promising route for large-scale manufacturing thin-film organic electronics.

Controlled assembly and release of retinoic acid based on the layer-by-layer method.

All-trans retinoic acid (RA) has been proved to play important roles in regulating cell growth in various types of cells. Yet most experiments were performed by adding RA in solution previously. In this Article, we focus on the incorporation of RA, as a negatively charged moiety, into layered polyelectrolyte films on surfaces by means of layer-by-layer (LbL) deposition, followed by adding of capping layers to regulate the release of RA from the films. The incorporated RA was designed to release over 5 days in buffer solution. The assembly and release of RA were verified by UV and QCM results. The controlled release of RA from multilayer films can serve as a model system to study the influence of small molecules on cell growth.

AFM-based force spectroscopy on polystyrene brushes: effect of brush thickness on protein adsorption.

Herein we present a study on nonspecific binding of proteins at highly dense packed hydrophobic polystyrene brushes. In this context, an atomic force microscopy tip was functionalized with concanavalin A to perform single-molecule force spectroscopy measurements on polystyrene brushes with thicknesses of 10 and 60 nm, respectively. Polystyrene brushes with thickness of 10 nm show an almost two times stronger protein adsorption than brushes with a thickness of 60 nm: 72 pN for the thinner and 38 pN for the thicker layer, which is in qualitative agreement with protein adsorption studies conducted macroscopically by fluorescence microscopy.

Coat thickness dependent adsorption of hydrophobic molecules at polymer brushes.

We study the adsorption properties of hydrophobic test particles at polymer brushes with different coat thicknesses via mesoscopic dissipative particle dynamics simulations. Our findings indicate stronger free energies of adsorption at thin polymer brushes. The reason for this difference is mainly given by entropic contributions due to different elastic deformations of the coatings. The numerical findings are supported by analytical calculations and are in good qualitative agreement to experimental fluorescence intensity results.

Nanoscaled surface patterning of conducting polymers.

In continuing the steady development of integrated-circuit-related fabrication, the ability to pattern conducting polymers into smaller and smaller sizes in order to realize devices with enhanced performance or even wholly new properties begins to take a more prominent role in their advanced applications. This review summarizes the recent advances in top-down and bottom-up patterning of conducting polymers on surfaces with different approaches including direct writing, in-situ synthesis or assembly, etching, and nanoscratching. All of the latest emerging strategies have the potential to go beyond the current state of the art towards real progress in terms of high-precision positioning, high resolution, high throughout, higher stability, facile processing, and lower-cost production.

Aggregation behaviour of peptide-polymer conjugates containing linear peptide backbones and multiple polymer side chains prepared by nitroxide-mediated radical polymerization.

A series of peptides with an alternating sequence of alkoxyamine conjugated lysine and glycine residues were synthesized by classical solution phase peptide coupling. The resulting peptides containing up to eight alkoxyamine moieties were used as initiators in nitroxide-mediated polymerization (NMP) to obtain peptide-polymer conjugates with well defined linear peptide backbones and a defined number of polymeric side chains. Polymerization of styrene and N-isopropylacrylamide (NIPAM) occurred in a highly controlled fashion. Molecular weight and polydispersity index (PDI) were determined by gel permeation chromatography (GPC). Aggregation behaviour of these hybrid materials was investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM). Depending on composition, number and length of the polymer side chains, the conjugates aggregate to different topologies. Whereas peptide-polystyrene conjugates may aggregate to so called honeycomb structures, peptide-poly-N-isopropylacrylamide conjugates show differentiated aggregation behaviour.

Combining host-guest systems with nonfouling material for the fabrication of a biosurface: toward nearly complete and reversible resistance of cytochrome c.

In this letter, a pH-responsive reactivated biointerface is fabricated using an inclusion reaction between an azobenzene-containing self-assembled monolayer and pH-responsive poly(ethylene glycol)-block-poly(acrylic acid) grafted with cyclodextrins. The pH-responsive interface can be switched between an extended state and a relaxed state for the reversible resistance of cytochrome c adsorption completely in cooperation with protein-resistant poly(ethylene glycol).

Ion strength and pH sensitive phase transition of N-isobutyryl-L-(D)-cysteine monolayers on Au(111) surfaces.

Self-assembled monolayers (SAMs) of N-isobutyryl-L-(D)-cysteine (NIBC) on Au(111) surfaces were successfully prepared by immersing the Au(111) surfaces in the preheated pure NIBC aqueous solutions for a certain time and characterized by means of scanning tunneling microscopy. Close-packed lamellar structures with a rectangular (4 x radical3) lattice were found both in the SAMs of L-NIBC and D-NIBC. The pH value of the aqueous solutions was found to be sensitive to adjust the SAM structures during the assembly. Changing the pH value from 5 to 7 may completely shift the SAM structures from close-packed lamellar phase to loose-packed perpendicular phase. Combined with density functional theory calculations, such kind of phase transition was explained by the breaking of hydrogen bonds between carboxylic groups and the formation of extra interactions between COO(-) and Au.

Defect-Controlled Preparation of UiO-66 Metal-Organic Framework Thin Films with Molecular Sieving Capability.

Metal-organic framework (MOF) UiO-66 thin films are solvothermally grown on conducting substrates. The as-synthesized MOF thin films are subsequently dried by a supercritical process or treated with polydimethylsiloxane (PDMS). The obtained UiO-66 thin films show excellent molecular sieving capability as confirmed by the electrochemical studies for redox-active species with different sizes.

Osteoblast alignment, elongation and migration on grooved polystyrene surfaces patterned by Langmuir-Blodgett lithography.

Topographically patterned surfaces are known to influence cellular behavior in a controllable manner. However, the relatively large surface areas (several cm2) required for many biomaterial applications are beyond the practical limits of traditional lithography. Langmuir-Blodgett lithography, a recently developed method, was used to fabricate regularly spaced grooves of different depths (50 and 150 nm) with a periodicity of 500 nm over several square centimeter on silicon surfaces. These topographies were transferred into polystyrene surfaces by means of nanoimprinting. Primary osteoblasts were cultured on the patterned polymer surfaces. They were observed to align, elongate and migrate parallel to the grooves. The combination of Langmuir-Blodgett lithography with nanoimprinting enables the fabrication of large, nanostructured surface areas on a wide spectrum of different biomaterials. Osteoblasts show a significant anisotropic behavior to these surfaces, which can enhance cell settlement on the surface or be used to direct tissue generation on the biomaterial interface.

Biomimetic antireflective silicon nanocones array for small molecules analysis.

Biomimetic antireflective silicon nanocones array is used for analysis of small molecules by mass spectrometry. The role of the absorbed laser energy and its distribution in the laser desorption/ionization process has been investigated by varying the antireflective features precisely. By optimizing the antireflective silicon array, the absorbed laser energy can be channeled completely into the desorption/ionization of analytes. The optimized silicon array exhibits excellent performance to detect peptide, amino acid, drug molecule, and carbohydrate without any interference in the low-mass region.

High-performance and stable organic transistors and circuits with patterned polypyrrole electrodes.

High performance p-/n-type transistors and complementary inverter circuits are demonstrated using patterned polypyrrole (PPY) as pure electrodes. Strikingly, these devices show good stability under continuous operation and long-term storage conditions. Furthermore, PPY electrodes also exhibit good applicability in solution-processed and flexible devices. All these results indicate the great potential of PPY electrodes in solution-processed, all-organic, flexible, transparent, and low-power electronics.

Host-guest chemistry at interface for photoswitchable bioelectrocatalysis.

Photoswitchable bioelectrocatalysis of glucose with glucose oxidase in an "On-Off" state is fabricated from host-guest chemistry at an interface by using the photocontrolled reversible immobilization and detachment of ferrocene-labeled redox-polymer as mediator.

Fabrication of gradient mesostructures by Langmuir-Blodgett rotating transfer.

In this letter, we present a simple yet novel method, Langmuir-Blodgett (LB) rotating transfer, to achieve a continuous gradient mesostructure in a well-ordered fashion over large areas. A mixed monolayer of phospholipid and dye is chosen as a model system to test the feasibility of LB rotating transfer to fabricate continuous gradient structures, which is confirmed by the simulation and experimental results. The technique presented here to obtain gradient structures is low-cost and high-throughput and can be extended to other systems of LB patterning.

Studies on the influence of phasins on accumulation and degradation of PHB and nanostructure of PHB granules in ralstonia eutropha H16.

Phasins play an important role in the formation of poly(3-hydroxybutyrate) [PHB] granules and affect their size and number in the cells. Recent studies on the PHB granule proteome and analysis of the complete genomic DNA sequence of Ralstonia eutropha H16 have identified three homologues of the phasin protein PhaP1. In this study, mutants of R. eutropha deficient in the expression of the phasin genes phaP1, phaP2, phaP3, phaP4, phaP12, phaP123, and phaP1234 were examined by gas chromatography. In addition, the nanostructures of the PHB granules of the wild-type and of the mutants were imaged by atomic force microscopy (AFM), and the molecular masses of the accumulated PHB were analyzed by gel permeation chromatography. For this, cells were cultivated under conditions permissive for accumulation of PHB and were then cultivated under conditions permissive for degradation of PHB. Mutants deficient in the expression of phaP2, phaP3, or phaP4 genes mobilized the stored PHB only slowly like the wild-type, whereas degradation occurred much earlier and faster in the phaP1 single mutant as well as in all multiple mutants defective in the phaP1 gene plus one or more other phasin genes. This indicated that the presence of the major phasin PhaP1 on the granule surface is important for PHB degradation and that this phasin is therefore of particular relevance for PHB accumulation. It was also shown that the molecular weights of the accumulated PHB were identical in all examined strains; phasins have therefore no influence on the molecular weight of PHB. The AFM images obtained in this study showed that the PHB granules of R. eutropha H16 form a single interconnected system inside the wild-type cells.