Self‐Assembly and Surface Photovoltage Response of ZnS Nanoparticulate Films Sensitized by Tetrasulfonated Copper Phthalocyanine

Composite films of ZnS nanoparticle‐polyelectrolyte were fabricated by the layer‐by‐layer self‐assembly technique. The optical properties and structure of the films were characterized by UV‐vis absorption spectra and AFM. The films sensitized by tetrasulfonated copper phthalocyanine (CuTsPc) show wide photovoltaic response range. The surface photovoltages corresponding to the ZnS nanoparticle interband transition and CuTsPc Q band transition in the sensitized film are approximately three to four times stronger than those in the ZnS nanoparticle‐polyelectrolyte film and CuTsPc film, respectively, which is attributed to the electron transition from the excited state of CuTsPc to the conduction band of ZnS nanoparticles.     

Fabrication of Patterned Conducting Polymers on Insulating Polymeric Substrates by Electric‐Field‐Assisted Assembly and Pattern Transfer

Summary: The use of electrostatically addressable templates for the directed assembly of conducting polymers and pattern transfer to another polymer substrate is demonstrated. Doped conducting polyaniline was selectively assembled on the patterned template assisted by a DC electric field. Adding an insulated silicon dioxide layer onto the surface of the silicon wafer is critical to the formation of patterned PANi rather than a PANi film. After deposition, it was demonstrated that by compression molding or solution casting methods, patterned PANi can be completely transferred to a secondary polymer substrate, such as an NBR sheet or a polyurethane film. The conductivity of PANi lines on the PU film was found to be as high as 0.87 S · cm⁻¹. The simple one‐step assembly process for patterning conductive polymers and transfer provides a promising nanomanufacturing approach for cost‐effective and high performance flexible nanoelectronics and biosensors.

Optical image of PANi‐assembled templates with patterned gold lines connected to negative electrodes at 10 V for 1 min.     

Directed Self‐Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays

The sequential layer by layer self‐assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large‐scale highly ordered metal nano­arrays prepared from solvent annealed thin films of polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle–substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self‐assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle–substrate interaction and nanoparticle–polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer.

     

Preparation and resistivity study of silver nanocomposite films using spin‐assisted layer‐by‐layer assembly

Nanocomposite films [Ag/(PAH‐PSS)_nPAH]_m were fabricated on a silicon substrate using a time‐ and cost‐efficient spin‐assisted layer‐by‐layer (SA‐LbL) self‐assembly technique. A virtually monolayer‐like layer of self‐assembled silver nanoparticles was formed when deposition time increased to 30 min. It was found that polymer multilayers could effectively decrease the resistivity of silver nanoparticle monolayer, which was far higher than that of bulk silver metal; however, the resistivity of Ag/(PAH‐PSS)_nPAH multilayer films increased along with the increasing of the number of polymer bilayers. XPS investigations showed that silver nanoparticles were partially oxidized, which might be the major cause of the high resistivity of silver nanoparticle monolayer. Copyright © 2008 John Wiley & Sons, Ltd.     

Bioactive Seed Layer for Surface‐Confined Self‐Assembly of Peptides

The design and control of molecular systems that self‐assemble spontaneously and exclusively at or near an interface represents a real scientific challenge. We present here a new concept, an active seed layer that allows to overcome this challenge. It is based on enzyme‐assisted self‐assembly. An enzyme, alkaline phosphatase, which transforms an original peptide, Fmoc‐FFY(PO₄^2?), into an efficient gelation agent by dephosphorylation, is embedded in a polyelectrolyte multilayer and constitutes the “reaction motor”. A seed layer composed of a polyelectrolyte covalently modified by anchoring hydrogelator peptides constitutes the top of the multilayer. This layer is the nucleation site for the Fmoc‐FFY peptide self‐assembly. When such a film is brought in contact with a Fmoc‐FFY(PO₄^2?) solution, a nanofiber network starts to form almost instantaneously which extents up to several micrometers into the solution after several hours. We demonstrate that the active seed layer allows convenient control over the self‐assembly kinetics and the geometric features of the fiber network simply by changing its peptide density.     

Forming Lipid Bilayer Membrane Arrays on Micropatterned Polyelectrolyte Film Surfaces

A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer‐by‐layer technique on a silicon oxide surface modified with a 3‐aminopropyltriethoxysilane (APTES) monolayer. The surface pK_a value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer‐by‐layer assembly. Micropatterned polyelectrolyte films were obtained by deep‐UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm² s^?1 in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field.     

Fabrication of Stable Chiral Polyaniline Nanocomposite‐Based Patterns

Summary: We report an artful method to form a stable pattern of chiral polyaniline nanocomposites (CPANs). It consists of the preparation of a diazoresin (DR)/poly(acrylic acid) (PAA) thin buffer layer on an Si substrate by self‐assembly, followed by the deposition of a multi‐layer film by spin‐assembly, leading to the formation of a (DR/PAA)₂DR/(CPAN/DR)_n film on the substrate. After selective exposure to UV light through a photomask and the development process, a defined pattern is formed.

Scanning electron microscopy image of the patterned (CPAN/DR)₅ thin film on Si wafer.     

Vortex‐Pattern Self‐Assembly in Mn‐Doped ZnSe Nanorods

Spontaneous patterning of anisotropic nanostructures into ordered assemblies remains a challenging quest, which requires controlled innovative approaches. One way to achieve such ordering of 1D nanorods is by manipulating the varieties of interactions (attractive and repulsive forces) present in colloidal solutions of anisotropic nanocrystals. The other ingenuous pathway is solvent‐evaporation‐mediated self‐organization of the 1D nanorods. By following the second protocol, we have achieved exclusive pillar self‐assembled patterns of visible‐light‐emitting Mn‐doped ZnSe nanorods. The nanorods also exhibit intriguing vortex patterning observed by directional solvent evaporation from the nanorod solution. The effect of solvent evaporation to generate such unique morphologies on the TEM grid is discussed and the reported procedure to obtain the assembled patterns of visible‐light‐emitting, doped nanorods might be useful for future technological applications.     

Fabrication of a Stable Polyelectrolyte/Au Nanoparticles Multilayer Film

The fabrication of stable polyelectrolyte/Au nanoparticle multilayer films was achieved by the UV irradiation of layer‐by‐layer self‐assembled multilayers consisting of diazoresins and Au nanoparticles. The method promises to be a simple and efficient strategy to construct covalently attached organic/inorganic multilayer hybrids.     

Odd‐even effect during layer‐by‐layer assembly of polyelectrolytes inspired by marine mussel

Biomimetic polyelectrolyte of Dopa modified poly(acrylic acid) (PAADopa) was synthesized taking advantage of Dopa, the major unit of marine adhesive proteins. Zinc crosslinked PAADopa (PAADopa‐Zn) were formed at acidic pH for more compact structure and assembled with the positively charged polyethylenimine (PEI) to build robust polyelectrolyte multilayers at high salt concentration. Effects of pH, crosslinking degree, and salt concentration on polymer structure, film building process, and morphology were investigated, respectively. An “odd‐even” effect was observed by quartz crystal microbalance with dissipation and AFM in the presence of zinc ion, which becomes more obvious with an optimum crosslinking degree (Zn/Dopa = 2.0) under high salt concentration (0.6 M NaCl). It indicates the different swollen properties of PEI chain and PAADopa‐Zn complexes during the layer‐by‐layer building process under optimum crosslinking degree of PAADopa‐Zn at high salt concentration. Such odd‐even phenomenon of the biocompatible system is of critical importance for understanding the mechanism of layer formation and film structures. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 245–255     

Synthesis of chitosan‐based thermo‐ and pH‐responsive porous nanoparticles by temperature‐dependent self‐assembly method and their application in drug release

In this research, thermo‐ and pH‐responsive chitosan‐based porous nanoparticles were prepared by the temperature‐dependent self assembly method. The chitosan‐graft‐poly(N‐isopropylacrylamide) (CS‐g‐PNIPAAm) copolymer solution was prepared through polymerization of N‐isopropylacrylamide (NIPAAm) monomer in the presence of chitosan (CS) solution using cerium ammounium nitrate as the initiator. Then, CS‐g‐PNIPAAm solution was diluted by deionized water and heated to 40 °C for CS‐g‐PNIPAAm self‐assembly. After that, CS‐g‐PNIPAAm assembled to form micelles in which shell layer was CS. Crosslinking agent was used to reinforce the micelle structure to form nanoparticle. The molar ratio of CS/NIPAAm in the feed mixture was changed to investigate its effect on structure, morphology, thermal‐ and pH‐responsive properties of the nanoparticles. TEM images showed that a porous structure of nanoparticles was developed. The synthesized nanoparticles carried positive charges on the surface and exhibited stimuli‐responsive properties, and their mean diameter thus could be manipulated by changing pH value and temperature of the environment. The nanoparticles showed a continuous release of the encapsulated doxycycline hyclate up to 10 days during an in‐vitro release experiment. These porous particles with environmentally sensitive properties are expected to be utilized in hydrophilic drug delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5126–5136, 2009     

Layer‐by‐layer self‐assembly of a metallo‐supramolecular coordination polyelectrolyte studied by infrared spectroscopy,microgravimetry, and X‐ray reflectance

Layer‐by‐Layer self‐assembly on planar substrates of a Fe(II) metallo‐supramolecular coordination polyelectrolyte (MEPE) and poly‐(styrene sulfonate) (PSS) is investigated with a variety of surface sensitive techniques. Results from reflection‐absorption infrared (RAIR) spectroscopy and microgravimetry are in agreement with linear multilayer build‐up. Furthermore, RAIR spectroscopy indicates close to complete counter ion exchange during polyion deposition. The multilayers contain approximately 20 mass‐percent water under ambient conditions. Water uptake and loss is completely reversible. Annealing to 250°C in air does not affect the structural integrity of the film as demonstrated by XRR measurements.     

Self‐Assembly of Platinum Nanoparticle/Multiwalled Carbon Nanotube Multilayer Film on Au Substrate Electrode

A novel approach to assemble multilayer films of Pt nanoparticle/multiwalled carbon nanotube (MWNTs) composites on Au substrate has been developed for the purpose of improving the methanol oxidation efficiency by providing high catalytic surface area. MWNTs were firstly functionalized with 4‐mercaptobenzene and then assembled on an Au substrate electrode. Pt nanoparticles were fabricated and attached to the surface of the functionalized MWNTs subsequently. Thus a layer of Pt/MWNT composites were assembled on the Au substrate electrode. Repeating above process can assemble different layers of film of Pt/MWNTs composites on the Au electrode. Cyclic voltammetry shows that the Au electrode modified with two layers of film of Pt/MWNT composites exhibits high catalytic ability and long‐term stability for methanol oxidation. The layer‐by‐layer self‐assembly technique provides an efficient strategy to construct complex nanostructure for improving the methanol oxidation efficiency by providing high catalytic surface area.     

Electropolymerization of layer‐by‐layer precursor polymer films

The layer‐by‐layer (LbL) self‐assembly has been used to fabricate polymer thin films on any solid substrates. The multilayer polymer thin films are constructed by alternating adsorption of anionic and cationic polymers. Polyelectrolyte multilayer ultrathin films containing anionic poly[2‐(thiophen‐3‐yl)ethyl methacrylate‐co‐methacrylic acid]; P(TEM‐co‐MA) and cationic poly[4‐(9H‐carbazol‐9‐yl)‐N‐butyl‐4‐vinyl pyridium bromide]; P4VPCBZ, were fabricated. The growth of multilayer ultrathin films was followed by UV–Vis absorption spectrophotometer and surface plasmon resonance spectroscopy (SPR). The deposition of P(TEM‐co‐MA)/P4VPCBZ as multilayer self‐assembled ultrathin films regularly grow which showed linear growth of absorbance and thickness with increasing the number of layer pair. Cross‐linking of the layers was verified by cyclic voltammetry (CV), UV–Vis spectrophotometry and electrochemical surface plasmon resonance (EC‐SPR) spectroscopy with good electro‐copolymerizability. This was verified by spectroelectrochemistry. The SPR angular‐reflectivity measurement resulted in shifts to a higher reflectivity according to the change in the dielectric constant of the electropolymerized film. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and hierarchical superstructures of side‐chain liquid crystal polyacetylenes containing galactopyranoside end‐groups

Three kinds of chiral saccharide‐containing liquid crystalline (LC) acetylenic monomers were prepared by click reaction between 2‐azidoethyl‐2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranoside and 1‐biphenylacetylene 4‐alkynyloxybenzoate. The obtained monomers were polymerized by WCl₆‐Ph₄Sn to form three side‐chain LC polyacetylenes containing 1‐[2‐(2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranos‐1‐yl)‐ethyl]‐1H‐[1,2,3]‐triazol‐4′‐biphenyl 4‐alkynyloxybenzoate side groups. All monomers and polymers show a chiral smectic A phase. Self‐assembled hiearchical superstructures of the chiral saccharide‐containing LCs and LCPs in solution state were studied by field‐emission scanning electron microscopy. Because of the LC behavior, the LC molecules exhibit a high segregation strength for phase separation in dilute solution (THF/H₂O = 1:9 v/v). The self‐assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self‐assembled morphology to change from a platelet‐like texture ( LC‐6 ) to helical twists morphology ( LC‐11 and LC‐12 ). Furthermore, the helical twist morphological structure can be aligned on the polyimide rubbed glass substrate to form two‐dimensional ordered helical patterns. In contrast to LC monomers, the LCP‐11 self‐assembled into much more complicate morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6596–6611, 2009     

Surface‐attached polymer networks through carbene intermediates generated from α‐diazo esters

We report on the generation of surface attached polymer networks through C,H insertion reactions based on carbene intermediates. To this copolymers based on N,N‐dimethyl acrylamide, which contain α‐diazo ester groups, are generated and coated onto a solid substrate covered with a self‐assembled monolayer of a silane. After deposition, films having thicknesses of approximately 120 nm are irradiated with UV light having a wavelength of 254 nm or 360 nm or heated to temperatures between 80 and 180 °C. During the light or heat‐induced activation process, carbenes are formed, which react via C—H insertion with any neighboring polymer chain and/or with the self‐assembled monolayer on the substrate, thus forming surface‐attached polymer networks. To follow the kinetics of the crosslinking process, the conditions are adjusted, so that they range between 5 and 10 min for the UV‐crosslinking and 5 to 15 min for the heat‐induced crosslinking. UV‐patterning of the surface‐attached polymer networks through chrome contact masks allows generation of microstructures in the micrometer range. We investigate the layer formation process and describe the formation of microstructured surfaces based on these surface‐attached polymer networks. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3276–3285     

Corrosion‐Mediated Self‐Assembly (CMSA): Direct Writing Towards Sculpturing of 3D Tunable Functional Nanostructures

Inexpensive and readily available metal foils have been extracted and sculptured into nanocomposites without the expense of applied energy. The unwanted corrosion phenomenon has been contrarily utilized to realize desirable 3D nanostructures through a corrosion‐mediated self‐assembly (CMSA) method, which is unattainable by conventional 2D patterning routes. By virtue of electrochemical dissolution/re‐deposition initiated by brass corrosion, ionic derivatives (Zn²⁺ and Cu²⁺) are continuously supplied and seized by etchant ions (PO₄^3?) to self‐assemble into well‐defined nanocomposites. Beyond 3D geometry patterning, CMSA enables arbitrarily tailoring of structures and chemical compositions with in situ multiphase amalgamation of hybrid materials, which improves homogeneity and thus mitigates phase separation issues. Importantly, the CMSA technique is demonstrated on transition metals for functional photocatalytic applications.     

A Reagentless Tyrosinase Biosensor Based on 1,6‐Hexanedithiol and Nano‐Au Self‐Assembled Monolayers

An amperometric tyrosinase biosensor was developed via a simple and effective immobilization method using the self‐assembled monolayers (SAMs) technique. The organic monolayer film was first formed by the spontaneous assembly of thiolor sulfur compound (1,6‐hexanedithiol, HDT) from solution onto gold electrode. When these thiol‐rich surfaces were exposed to Au colloid, the sulfurs form strong bonds to gold nanoparticles, anchoring the clusters to the electrode substrate. After the assembly of gold nanoparticles layer, a new nano‐Au surface was obtained. Thus, the tyrosinase could be immobilized onto the electrode. The tyrosinase retained its activity well in such an immobilization matrix. The various experimental variables for the enzyme electrode were optimized. The resulting biosensor can reach 95% of steady‐state current within 10 s, and the trend in the sensitivity of different phenolic compounds was as follows: catechol>phenol>p‐cresol. In addition, the apparent Michaelis–Menten constant (K and the stability of the enzyme electrode were estimated.     

Layer‐by‐layer assembly of {chitosan/Pd}n multilayer film based on in‐situ photochemical reduction with excellent electrocatalytic properties

Chitosan/palladium {CTS/Pd}_n composite multilayer film was assembled based on layer‐by‐layer self‐assembly technique and in‐situ photo‐chemical reduction reaction, in which the CTS plays the role of a photo‐reduction agent and an assembly reagent. Transmission electron microscopy (TEM) shows that spherical Pd nanoparticles with diameter of 20 nm are well‐dispersed in the composite multilayer films, and the size of Pd nanoparticles increased gradually with the extension of illumination time. Besides, the {CTS/Pd}_n composite multilayer film exhibits linear, uniform and regular layer‐by‐layer growth. Furthermore, the {CTS/Pd}_n composite multilayer film presents an excellent catalytic properties for oxygen reduction, and it has potential application in energy, chemical synthesis and biological processes. Copyright © 2015 John Wiley & Sons, Ltd.     

QCM 表面自组装胱氨酸1，3－桥连杯[4]芳烃膜用于识别气相丁胺

Two cystine-bearing 1,3-bridged calix[4]arenes were used as the coatings of the quartz crystal microbalance (QCM) with gold electrodes. The two calix[4]arene derivatives were self-assembled onto the gold electrode surface by the covalent attachment between the di-sulfur and gold. The compound of cystine-bearing bi-phenylalanine 1,3-bridged calix[4]arene (CPC) with longer alkyl chain had better self-assembled capacity onto the fresh surfaces of gold electrode than that of cystine-bearing 1,3-bridged calix[4]arene (CC) with comparably shorter alkyl chain.The modified QCM sensors were used to recognize the butylamine isomers in gas. The results showed that the QCM coated with both compounds had preferential affinity to n-butylamine, then i-butylamine, t-butylamine in the range of low concentrations, indicating that in the recognition process, the steric hindrance effect played an important role when forming complex with guest molecules. When the concentrations of the analytes were increased, the polarity and the magnetism of the butylamine became determinative factors. The reversibility was improved greatly and the equilibrium time was much shorter on the self-assembled film than on the film obtained by dropping coating.