Nanoporous Silver Submicrocubes Layer by Layer Encapsulated with Polyelectrolyte Films: Nonenzymatic Catalysis for Glucose Monitoring.

This article describes the synthesis of nanoporous silver submicrocubes (Np-Ag) capped with poly(allylamine hydrochloride) PAH/poly(styrenesulfonate) PSS bilayers (Np-Ag(PAH/PSS), 1 ≤ ≤ 4) via layer-by-layer (LBL) assembly for the electrochemical glucose sensing. The consecutive LBL encapsulation of Np-Ag (average size ≈530 nm) with positively charged PAH and negatively charged PSS layers was monitored by using ζ-potential analyses, which showed that the sign of the ζ-potential became positive (+10 mV) or negative (-22 mV) depending on the charge of the encapsulating species. The thickness of two PAH/PSS bilayers on the Np-Ag was estimated to be ∼4 nm (consistent with a literature value of ∼1 nm per PAH or PSS layer) on the basis of a high-resolution transmission electron microscopy image of the Np-Ag(PAH/PSS).

Gold nanorods based multicompartment mesoporous silica composites as bioagents for highly efficient photothermal therapy.

Photothermal therapy (PTT) based on photothermal effect of the gold nanostructures, has been widely applied as a noninvasive therapy approach in cancer treatment. However, bare Au nanoparticles are not stable enough during the irradiation process, and cannot harvest sufficient energy to kill tumor cells. To improve this, we have fabricated a stable bioagent by loading gold nanorods (AuNRs) into multicompartment mesoporous silica nanoparticles (MMSNs) for the photothermal therapy.

Proton-consumed nanoarchitectures toward sustainable and efficient photophosphorylation.

At present, photophosphorylation in natural or artificial systems is accomplished by the production of protons or their pumping across the biomembranes. Herein, different from this strategy above, we demonstrate a designed system which can effectively enhance photophosphorylation by photo-induced proton-scavenging through molecular assembly. Upon the introduction of photobase generators, a (photo-) chemical reaction occurs to produce hydroxyl ions.

Facile and Scalable Synthesis Method for High-Quality Few-Layer Graphene through Solution-Based Exfoliation of Graphite.

Here we describe a facile and scalable method for preparing defect-free graphene sheets exfoliated from graphite using the positively charged polyelectrolyte precursor poly(p-phenylenevinylene) (PPV-pre) as a stabilizer in an aqueous solution. The graphene exfoliated by PPV-pre was apparently stabilized in the solution as a form of graphene/PPV-pre (denoted to GPPV-pre), which remains in a homogeneous dispersion over a year. The thickness values of 300 selected 76% GPPV-pre flakes ranged from 1 to 10 nm, corresponding to between one and a few layers of graphene in the lateral dimensions of 1 to 2 μm.

Nitrogen-Doped Holey Graphene Film-Based Ultrafast Electrochemical Capacitors.

The commercialized aluminum electrolytic capacitors (AECs) currently used for alternating current (AC) line-filtering are usually the largest components in the electronic circuits because of their low specific capacitances and bulky sizes. Herein, nitrogen-doped holey graphene (NHG) films were prepared by thermal annealing the composite films of polyvinylpyrrolidone (PVP), graphene oxide (GO), and ferric oxide (Fe2O3) nanorods followed by chemical etching with hydrochloride acid. The typical electrochemical capacitor with NHG electrodes exhibited high areal and volumetric specific capacitances of 478 μF cm(-2) and 1.

A high-performance moisture sensor based on ultralarge graphene oxide.

This article describes the effect of the lateral size of graphene oxide (GO) on the humidity sensing properties of a GO-based sensor. The GO size effect on the humidity sensing performance was evaluated on gold electrodes drop-coated with either an ultralarge graphene oxide (UGO) sheet (lateral size = 47.4 ± 22.

Dual-protection of a graphene-sulfur composite by a compact graphene skin and an atomic layer deposited oxide coating for a lithium-sulfur battery.

A reduced graphene oxide (rGO)-sulfur composite aerogel with a compact self-assembled rGO skin was further modified by an atomic layer deposition (ALD) of ZnO or MgO layer, and used as a free-standing electrode material of a lithium-sulfur (Li-S) battery. The rGO skin and ALD-oxide coating worked as natural and artificial barriers to constrain the polysulfides within the cathode region. As a result, the Li-S battery based on this electrode material exhibited superior cycling stability, good rate capability and high coulombic efficiency.

Dopamine-melanin nanofilms for biomimetic structural coloration.

This article describes the formation of dopamine-melanin thin films (50-200 nm thick) at an air/dopamine solution interface under static conditions. Beneath these films, spherical melanin granules formed in bulk liquid phase. The thickness of dopamine-melanin films at the interface relied mainly on the concentration of dopamine solution and the reaction time.

Highly compressible macroporous graphene monoliths via an improved hydrothermal process.

An improved hydrothermal process is developed to fabricate macroporous graphene monoliths (MGMs) using a soft template of organic droplets. The MGMs are constructed from closed-cell distorted spherical pores. This unique microstructure makes MGMs that have low weight densities, good electrical conductivities, and excellent elasticity with rapid recovery rates.

Multilayered poly(p-phenylenevinylene)/reduced graphene oxide film: an efficient organic current collector in an all-plastic supercapacitor.

This article describes the preparation, using layer-by-layer deposition techniques, of an all-solid-state flexible in-plane supercapacitor based on a poly(ethylene terephthalate) (PET) substrate, laminated with two strata of ultrathin multilayer films composed of 30 polyaniline (PANi)/reduced graphene oxide (RGO) bilayers and 30 poly(p-phenylenevinylene) (PPV)/RGO bilayers. The influence of the (PPV/RGO)30 stratum on the electrochemical properties of the (PANi/RGO)30/(PPV/RGO)30 film (denoted P30) (d = 90.1 nm) supported on a PET was evaluated and compared to the corresponding influence of the (PANi/RGO)53 film (denoted P53) (d = 91.

Simple method of DNA stretching on glass substrate for fluorescence imaging and spectroscopy.

We demonstrate a simple method of stretching DNA to its full length, suitable for optical imaging and atomic force microscopy (AFM). Two competing forces on the DNA molecules, which are the electrostatic attraction between positively charged dye molecules (YOYO-1) intercalated into DNA and the negatively charged surface of glass substrate, and the centrifugal force of the rotating substrate, are mainly responsible for the effective stretching and the dispersion of single strands of DNA. The density of stretched DNA molecules could be controlled by the concentration of the dye-stained DNA solution.

Layer-by-layer self-assembled multilayer films composed of graphene/polyaniline bilayers: high-energy electrode materials for supercapacitors.

Multilayer assemblies of uniform ultrathin film electrodes with good electrical conductivity and very large surface areas were prepared for use as electrochemical capacitors. A layer-by-layer self-assembly approach was employed in an effort to improve the processability of highly conducting polyaniline (PANi) and chemically modified graphene. The electrochemical properties of the multilayer film (MF-) electrodes, including the sheet resistance, volumetric capacitance, and charge/discharge ratio, were determined by the morphological modification and the method used to reduce the graphene oxide (GO) to reduced graphene oxide (RGO) in the multilayer films.

Self-standing polyelectrolyte multilayer films based on light-triggered disassembly of a sacrificial layer.

In the present article, we present a new and convenient optical method for the preparation of self-standing polyelectrolyte multilayer films. This method employs the disassembly of a sacrificial layer stratum composed of five poly(acrylate, merocyanine) PMC/poly(diallyldimethylammonium chloride) PDADMAC bilayers, which is triggered by the irradiation with visible light. This leads to the conversion of the zwitterionic PMC to its neutral isomer poly(acrylate, spiropyran) PSP, whereby the attractive ionic interactions between the neighboring bilayers vanish.

Ion-permselective polyelectrolyte multilayer membrane installed with a pH-sensitive oxazine switch.

This paper describes a pH-responsive multilayer film composed of two layered components, namely poly(allylamine hydrochloride) (PAH) and a copolymer of acrylic acid and [1,3]oxazine-modified acrylate (POA). The oxazine ring is an acidochromic chromophore and opens to form either cationic 3H-indolium or anionic hemiaminal in a pH-dependent manner. This structural transition was used to generate a net positive or negative charge on the membrane for selective ion permeation.

Use of 1,3-dithiane combined with aryldiazonium cation for immobilization of biomolecules based on electrochemical addressing.

We report the use of 1,3-dithiane combined with aryldiazonium cation for the immobilization of biomolecules based on electrochemical addressing.

Photoregulation of ion permeation through a polyelectrolyte multilayer membrane by manipulating the chromophore orientation.

Toward the realization of nanoscale device control, we report a novel method for photoregulation of ion flux through a polyelectrolyte multilayer membrane by chromophore orientation that is adjusted either by illumination at normal incidence or by slantwise irradiation at an angle of 10 degrees with respect to the surface. Our results indicate that the chromophore reorientation caused by the slantwise irradiation controls the effective pore size and, consequently, the transport behavior on the nanoscale. The slantwise illumination, which includes six EZE photoisomerization cycles generated by alternately irradiating with ultraviolet (lambda = 360 nm) and visible (lambda = 450 nm) light, reversibly switches the orientation of E-azobenzene in the membrane between 53 +/- 2 degrees (high tilt) and 17 +/- 5 degrees (low tilt) with respect to the surface.

Azide-assisted cross-linked sulfonated poly(ether sulfone)s as stable and highly conductive membranes with low methanol diffusion coefficients.

Novel cross-linked sulfonated poly(ether sulfone)s, prepared by azide-assisted thermal irradiation, show not only low methanol permeability but also exceptionally high proton conductivity with oxidative and hydrolytic stability.

Photoresponsive ion gating function of an azobenzene polyelectrolyte multilayer spin-self-assembled on a nanoporous support.

The fabrication of a polyelectrolyte multilayer (PEM) on a porous membrane was successfully improved by using spin-coating electrostatic self-assembly. Surprisingly, the quality of the PEM film obtained on the nanoporous alumina substrate (i.e.

Spatial control of quantum sized nanocrystal arrays onto silicon wafers.

Monolayer arrays of monodispersed nanocrystals (<10 nm) onto three dimensional (3D) substrates have considerable potential for various engineering applications such as highly integrated memory devices, solar cells, biosensors and photo and electro luminescent displays because of their highly integrated features with nanocrystal homogeneity. However, most reports on nanocrystal arrays have focused on two dimensional (2D) flat substrates, and the production of wafer-scale monolayer arrays is still challenging. Here we address the feasibility of arraying nanocrystal monolayers in wafer-scale onto 3D substrates.

Electrostatic self-assembly of a macrocyclic amphiphile for inducing the flat orientation of chromophores.

In this article, a new methodological approach to the fabrication of organized molecular films with chromophores lying flat on the film surface has been investigated with the design of an azacrown-type multication, 1,4,10-[3-(4-(4'-methoxy-phenylazo)-2-nitro-phenoxy)propyl]-1,4,7,10,13,16-hexamethylhexaazacyclooctadecane, and LBL film deposition by using the electrostatic self-assembly method. The chromophore alignment was analyzed on the basis of the polarized UV-visible spectra: the tilt angle of the transition moment of trans-azobenzene with respect to the surface normal was determined to 64 +/- 2 degrees , indicating a strong trend for chromophores in the multilayered films to planar alignment.