Electrostatic Self-assembly Method Research Articles

Fabrication of ZnO nanorods/Fe3O4 quantum dots nanocomposites and their solar light photocatalytic performance

ZnO nanorods (NRs)/Fe3O4 quantum dots (QDs) nanocomposites were successfully synthesized via an easy electrostatic self-assembly method. The results showed that Fe3O4 QDs with an average diameter of 4–5 nm were well dispersed on the surface of the ZnO NRs with an average diameter of 118 nm, forming ZnO NRs/Fe3O4 QDs nanocomposites. The ZnO NRs/Fe3O4 QDs nanocomposites were used as photocatalysts for the degradation of Rhodamine B under solar light irradiation. The kinetic rate constant of the ZnO NRs/Fe3O4 QDs nanocomposites was two times higher than that of the ZnO NRs. The enhanced photocatalytic property was attributed to the extended absorption spectrum of the nanocomposites.

Detection of ammonia in human breath using quartz crystal microbalance sensors with functionalized mesoporous SiO2 nanoparticle films

Quartz crystal microbalance (QCM) sensors with porous films comprising silica nanoparticles and poly(allylamine hydrochloride) (PAH) were fabricated. The films were deposited via an electrostatic self-assembly method, and they exhibited considerable sensitivity to relative humidity. The infusion of poly(acrylic acid) (PAA) into multi-layer porous films (5 or 10 cycles) enabled the construction of a highly sensitive and selective QCM sensor device for the detection of gaseous ammonia. Two types of QCM sensors, with and without PAA, were used as sensors for the simultaneous quantitative detection of humidity and ammonia. A comprehensive Fourier transform infrared (FTIR) investigation of the fabricated films was conducted to elucidate the mechanism of the chemical interaction at the sensor device interface. Preliminary tests were conducted to detect low concentrations of ammonia in human breath, which are of clinical relevance. The results of these tests showed that the sensor can detect ammonia in human breath at pathological levels (greater than 3ppm).

Face-to-face self-assembly graphene/MnO2 nanocomposites for supercapacitor applications using electrochemically exfoliated graphene

Layered graphene/manganese oxide (G/MnO2) nanocomposites for supercapacitor applications were prepared with a face-to-face electrostatic self-assembly method using high-quality graphene, which was obtained from the one-step electrochemical exfoliation of graphite. The results reveal that the graphene and MnO2 nanaosheets need to be oppositely charged for the electrostatic self-assembly process. The face-to-face contact between the MnO2 nanosheets and graphene can effectively improve the conductivity of MnO2 and prevent the restacking and agglomeration of graphene. In addition, the composites exhibit an electrochemical-activation behavior, and the ratio of MnO2/graphene in composites significantly influences the electrochemical performance. The G-2/MnO2 composite displays a specific capacitance of 319Fg−1 at 0.2Ag−1, and only 4.4% of the capacitance degrades after 10,000 cycles, which demonstrates the composite's excellent cycle stability. Furthermore, the composite features a high energy density of 31.5Whkg−1 at a power density of 100Wkg−1. This attractive performance makes it a promising candidate as an electrode material for supercapacitors. Remarkably, although the graphene content in G-4/MnO2 composite is the same, the specific capacitance reduced to 186Fg−1 due to the different mixing times.

A bisphenol A sensor based on novel self-assembly of zinc phthalocyanine tetrasulfonic acid-functionalized graphene nanocomposites.

In this work, a novel zinc phthalocyanine tetrasulfonic acid (ZnTsPc)-functionalized graphene nanocomposites (f-GN) was synthesized by a simple and efficient electrostatic self-assembly method, where the positive charged GN decorated by (3-aminopropyl) triethoxysilane (APTES) was self-assemblied with ZnTsPc, a two dimensional (2-D) molecules. It not only enhanced its stability for the hybrid structure, but also avoided the reaggregation of ZnTsPc or f-GN themselves. Based on layered ZnTsPc/f-GN nanocomposites modified glassy carbon electrode, a rapid and sensitive sensor was developed for the determination of bisphenol A (BPA). Under the optimal conditions, the oxidation peak current increased linearly with the concentration of BPA in the range of 5.0×10(-8) to 4.0×10(-6)M with correlation coefficient 0.998 and limits of detection 2.0×10(-8)M. Due to high absorption nature for BPA and electron deficiency on ZnTsPc/f-GN, it presented the unique electron pathway arising from π-π stackable interaction during redox process for detecting BPA. The sensor exhibited remarkable long-term stability, good anti-interference and excellent electrocatalytic activity towards BPA detection.

Graphene oxide as a corrosion-inhibitive coating on magnesium alloys

A graphene oxide film was formed on the PEO coatings of magnesium alloys via an electrostatic self-assembly method, which functioned as a physical separation with inhibiting effects between the protected metal and reactants.

Facile synthesis of N-halamine-labeled silica-polyacrylamide multilayer core-shell nanoparticles for antibacterial ability.

Silica-polymer antimicrobial composites with a core-shell nanostructure are often prepared through a polymeric process. However, it is difficult to control the polymerization degree of the polymers to give a uniform size distribution. In this article, we present a facile approach to produce antimicrobial silica@polyacrylamide (SiO2@PAM) core-shell nanoparticles, which were synthesized via an electrostatic self-assembly method using acyclic N-halamine polymeric polyacrylamide. The morphologies and structures of these as-prepared nanoparticles were characterized by different techniques. And their antibacterial performance against both Gram-positive bacteria and Gram-negative bacteria was also evaluated. Based on the preliminary results, these core-shell nanosized spheres were made of an outer polymer shell which decorated the inner SiO2 core, showing the encapsulation of silica nanoparticles with PAM polymers. After chlorination, the resultant nanosized particles displayed a powerful and stable bactericidal capability toward both of the two model bacterial species. Bactericidal assessment further suggested a coordinated effect of the well-known antibacterial performance of N-halamines and the flocculation of PAM on the antibacterial behavior. The in vitro cytotoxicity of the prepared nanoparticles with varying concentrations was studied using mouse fibroblast cells (L929). The CCK-8 assay revealed that the SiO2@PAM composites possessed a non-cytotoxic and favorable response to the seeded cells in vitro. These results indicate the suitability of the SiO2@PAM composite particles for controlling biocidal activity, demonstrating their potential applications in deactivating bacteria or even disease control.

Improved electrode durability using a boron-doped diamond catalyst support for proton exchange membrane fuel cells

BDD was produced by an electrostatic self-assembly (ESA) method. We investigated the improvement of durability by performing tests under real PEMFC operating conditions and observing changes in the support material morphology.

Rationally designed 1D Ag@AgVO3nanowire/graphene/protonated g-C3N4nanosheet heterojunctions for enhanced photocatalysis via electrostatic self-assembly and photochemical reduction methods

1D Ag@AgVO3nanowire/graphene/protonated g-C3N4nanosheet heterojunctions were fabricated and applied as an efficient photocatalyst for organic pollutant degradation.

Constructing one-dimensional silver nanowire-doped reduced graphene oxide integrated with CdS nanowire network hybrid structures toward artificial photosynthesis.

A ternary hybrid structure of one-dimensional (1D) silver nanowire-doped reduced graphene oxide (RGO) integrated with a CdS nanowire (NW) network has been fabricated via a simple electrostatic self-assembly method followed by a hydrothermal reduction process. The electrical conductivity of RGO can be significantly enhanced by opening up new conduction channels by bridging the high resistance grain-boundaries (HGBs) with 1D Ag nanowires, which results in a prolonged lifetime of photo-generated charge carriers excited from the CdS NW network, thus making Ag NW-RGO an efficient co-catalyst with the CdS NW network toward artificial photosynthesis.

Electrostatic self-assembly of graphene oxide wrapped sulfur particles for lithium–sulfur batteries

A novel graphene oxide (GO)/sulfur (S) composite is developed by electrostatic self-assembly method. Remarkably, the core–shell structure of the composite and the GO support helps to retard the diffusion of polysulfides during the electrochemical cycling process. The GO/sulfur cathode presents enhanced cycling ability. Specific discharge capacities up to 494.7mAhg−1 over 200 cycles at 0.1C is achieved with enhanced columbic efficiency around 95%, representing a good cathode material for lithium–sulfur batteries.

PH-sensing properties of cascaded long- and short-period fiber grating with poly acrylic acid/poly allylamine hydrochloride thin-film overlays

Based on coupled-mode theory and transfer matrix method, the mode coupling mechanism and the reflection spectral properties of coated cascaded long- and short-period gratings (CLBG) are discussed. The effects of the thin-film parameters (film refractive index and film thickness) on the reflection spectra of the coated CLBG are simulated. By using electrostatic self-assembly method, poly acrylic acid (PAA) and poly allylamine hydrochloride (PAH) multilayer molecular pH-sensitive thin-films are assembled on the surface of the partial corroded CLBG. When the CLBG coated with PAA/PAH films are used to sense pH values, the resonant wavelengths of the CLBG have almost no shift, whereas the resonance peak reflectivities change with pH values. In addition, the sensitivities of the resonance peak reflectivities responding to pH values are improved by an order of magnitude.

Preparation and characterization of natural zeolite supported nano TiO2photocatalysts by a modified electrostatic self-assembly method

Natural zeolite supported nano TiO2 photocatalysts were prepared by a modified electrostatic self-assembly (ESA) method. First, γ-mercaptopropyltrimethoxysilane with sulfhydryl (―SH) functional groups was modified on the zeolite powders by using a ‘dry process’. Second, silane with ―SH functional groups was oxidized to sulfonate (―SO3H) groups by using a hydrogen peroxide/glacial acetic acid mixed solution, and the surface of ―SO3H silane–zeolite was electronegative charged due to the ionization of ―SO3H. Third, the hydrolytic titanium polycation from TiCl4 solution assembled onto the electronegative charged zeolite under electrostatic attraction in the reaction solutions. Finally, zeolite supported nano TiO2 photocatalysts can be obtained after the above compounds calcined at certain temperature. The samples were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF). The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in aqueous solution. The results showed that ESA method effectively improved the composite efficiency of zeolite with TiO2. The photocatalysts prepared by ESA method exhibited higher photocatalytic and recycling activities than that of traditional method. Copyright © 2014 John Wiley & Sons, Ltd.

Electrochemical Characterization of Multilayered CdTe/PSS Films Prepared by Electrostatic Self-assembly Method

Multilayered CdTe/PSS films were prepared by the electrostatic self-assembly method in an aqueous medium. Positively-charged cadmium telluride (CdTe) nanoparticles and anionic polyelectrolyte, poly (sodium 4-styrene sulfonate) (PSS) were assembled alternately in order to build up a multilayered film structure. A linear proportion of absorbance to the number of bilayers suggests that an equal amount of CdTe was adsorbed after each dipping cycle, which resulted in the buildup of a homogenous film. The binding energies of elements (Cd and Te) in multilayered CdTe/PSS film shifted from those of the CdTe nanoparticles in the pure state. This result indicates that the interfacial electron densities were redistributed by the strong electrostatic interaction between the oppositely-charged CdTe and PSS. Electrochemical properties of the multilayered CdTe/PSS films were studied in detail by cyclic voltammetry (CV).

A novel solution-controlled hydrogel coated mesh for oil/water separation based on monolayer electrostatic self-assembly

Solution-controlled hydrogel coated materials for oil/water separation have been successfully fabricated. The as-prepared mesh can switch between superhydrophilicity/underwater superoleophobicity and superhydrophobicity/superoleophilicity through self-assembly and dis-assembly pathways. The PDMAEMA hydrogel coated mesh is firstly prepared via photo induced free radical polymerization. A facile monolayer electrostatic self-assembly method was involved by immersing the hydrogel coated mesh in an ethanol solution of stearic acid for a few minutes. The stearic acid modified mesh converts to superhydrophobicity/superoleophilicity. More importantly, the mesh can return to the original state swiftly after the dis-assembly of the monolayer by immersion in a NaOH aqueous solution. The unique superiority of this material is that the transition of wettability can be achieved in situ, so that oil and water can pass through the mesh in sequence through the control of the NaOH solution. Therefore, the as-prepared meshes have great potential in practical applications dealing with both water-rich and oil-rich oil/water mixture separation with high separation efficiency (>99.3%). The synthetic method is simple, time saving and cost saving.

Structural colors of the SiO2/polyethyleneimine thin films on poly(ethylene terephthalate) substrates

The SiO2/polyethyleneimine (PEI) films with structural colors on poly(ethylene terephthalate) (PET) substrates were fabricated by an electrostatic self-assembly method. The morphology of the films was characterized by Scanning Electron Microscopy. The results showed that there was no distinguishable multilayered structure found of SiO2/PEI films. The optical behaviors of the films were investigated through the color photos captured by a digital camera and the color measurement by a multi-angle spectrophotometer. Different hue and brightness were observed at various viewing angles. The structural colors were dependent on the SiO2 particle size and the number of assembly cycles. The mechanism of the structural colors generated from the assembled films was elucidated. The morphological structures and the optical properties proved that the SiO2/PEI film fabricated on PET substrate formed a homogeneous inorganic/organic SiO2/PEI composite layer, and the structural colors were originated from single thin film interference.

Self-assembly synthesis of magnetic fluorescein derivatives for Cu(II)-assisted OFF–ON fluorescence probe of nitric oxide

By the electrostatic adsorption self-assembly method, one of the typical fluorescein derivatives (2-{2-Chloro-6-hydroxy-5-[(2-(methylcarboxy) quinolin-8-ylamino)methyl]-3-oxo-3H-xanthen-9-yl}benzoic acid, abbreviated as FL) was conjugated with polyethylenimine modified Fe3O4 nanoparticles to form Fe3O4 at FL complex, which then directly reacted with CuII to generate Fe3O4 at FL–CuII accompanied by fluorescence reduction (OFF). Introduction of nitric oxide (NO) induced the conversion of Fe3O4 at FL–CuII to Fe3O4 at FL–NO due to N-nitrosate reaction, together with dramatic fluorescence enhancement (ON). Experimental results proved that this PL enhancement response to NO was highly selective and sensitive over other competing species, indicating that Fe3O4 at FL complex was promising, especially as a novel magnetism-targeted and CuII-assisted nanoprobe for highly effective OFF–ON fluorescence detection of NO.

Self‐assembly of different graphene‐modified morphologies of TiO 2 : nanoparticle, nanorod and nanowire for bisphenol‐A photodecomposition

Different graphene (GR)-modified morphologies of TiO 2 including nanoparticles, nanorods and nanowires were prepared by a simple and efficient electrostatic self-assembly method followed by a hydrothermal reduction process. Characterisations reveal that different morphologies of TiO 2 are distributed on GR and that they decrease the electron-hole recombination rate and extend the light absorption range compared with pure TiO 2 . The as-prepared different morphologies of GR-modified TiO 2 nanocomposites are used to photodecompose bisphenol-A in water under visible-light irradiation. All morphologies of TiO 2 anchored onto the surface of a GR sheet exhibit higher photocatalytic activity under irradiation than pure TiO 2 . Photocatalytic activity is also increased by the increase in length of TiO 2 distributed on GR. The photodegradation activities of all GR/TiO 2 nanocomposites are stable under light after three successive cycles.

Nano polyurethane based surface modification on the anti-felting functionalization of wool fabrics

Nano polyurethane (Nano PU) was used for the fabrication of multilayer nanocomposite film deposition on wool fabrics by electrostatic self-assembly to improve the anti-felting properties. Oppositely charged cationic poly (diallyldimethylammonium chloride) (PDDA) and anionic Nano PU were alternately deposited on the surface of wool fabrics. 8, 12 and 16 multilayer films of PDDA/Nano PU were deposited on the wool fabric surfaces using a padder. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM-EDX) were used to verify the presence of deposit nanolayers. Breaking strength, whiteness and yellowness value analysis was performed on the fabrics before and after the treatment with Nano PU by the electrostatic self-assembly method. The build-up of the multilayer films and the level of colour strength (K/S) achieved are discussed after the acid dyeing process. To examine the anti-felting properties of the multilayered fabrics, the fabric shrinkage after washing was determined.

Highly Disordered Carbon as a Superior Anode Material for Room‐Temperature Sodium‐Ion Batteries

Highly Disordered Carbon as a Superior Anode Material for Room‐Temperature Sodium‐Ion Batteries

A general strategy for protein immobilization in layered titanates: Polyelectrolyte-assisted self-assembly

A general strategy was demonstrated here to immobilize proteins with various isoelectric points (IPs) in layered titanates. The immobilization of proteins with relative low IPs, such as bovine serum albumin (BSA) and lipase, in layered titanates was successfully by a novel polyelectrolyte-assisted electrostatic self-assembly technique, which is impossible by a conventional electrostatic self-assembly method. Lysozyme with relative high IP was detractively interacted with negative titanate nanosheets to form a bioinorganic composite. The native structures of proteins were retained after immobilizing although a significant difference in microstructures was observed among these composites. The amounts of immobilized proteins were up to ∼68.3wt.% for lysozyme, 37.2wt.% for BSA and 21.5wt.% for lipase. These composites were stable in the neutral and weakly acidic condition, and only releases <10% proteins in the pH<4 solution. The immobilized lysozyme and lipase exhibit excellent thermal stability, which retain their initial activities of about 70% at 70°C for about 40min. In addition, these composites are reusable, and the residual activities of immobilized enzymes are 68% for lysozyme and 61% for lipase after 10 recycles.