graphene sheets have become a versatile platform for the fabrication of innovative hybrid materials with various functions due to their unique electrical, optical, thermal, and mechanical properties. The preparation of graphene-based composites with nanoscale precision is highly important for reproducible and controllable performance through the analysis of interplay between each component. In particular, the layer-by-layer (LbL) assembly technique is known as a simple, inexpensive, and versatile process for the fabrication of highly ordered multilayer film structures from various types of materials. The LbL structures capable of controlling nanoscale composition and architectures are achieved through the sequential adsorption of oppositely charged components by attractive forces such as electrostatic interactions. In this review, we will focus on the recent progress in graphene-based nanocomposites hybridized with various nanomaterials such as carbon nanomaterials, polymers, and inorganic nanoparticles by the LbL assembly. Multilayered graphene nanocomposites exhibit improved physical/chemical properties and superior performance compared with the individual components due to the synergistic effects in various applications including electric devices, energy storage and conversion, and biological usages.

Organic light-emitting diodes have been recently focused for flexible display and solid-state lighting applications and so much effort has been devoted to achieve highly efficient organic light-emitting diodes. Here, we improve the efficiency of inverted polymer light-emitting diodes by introducing a spontaneously formed ripple-shaped nanostructure of ZnO and applying an amine-based polar solvent treatment to the nanostructure of ZnO. The nanostructure of the ZnO layer improves the extraction of the waveguide modes inside the device structure, and a 2-ME þ EA interlayer enhances the electron injection and hole blocking in addition to reducing exciton quenching between the polar-solvent-treated ZnO and the emissive layer. Therefore, our optimized inverted polymer light-emitting diodes have a luminous efficiency of 61.6 cd A À 1 and an external quantum efficiency of 17.8%, which are the highest efficiency values among polymer-based fluorescent light-emitting diodes that contain a single emissive layer.

Alternative materials obtained from natural resources have recently garnered considerable attention as an innovative solution to bring unprecedented advances in various energy storage systems. Here, we present a new class of heterolayered nanomat-based hierarchical/asymmetric porous membrane with synergistically coupled chemical activity as a nanocellulose-mediated green material strategy to develop smart battery separator membranes far beyond their current state-of-the-art counterparts. This membrane consists of a terpyridine (TPY)-functionalized cellulose nanofibril (CNF) nanoporous thin mat as the top layer and an electrospun polyvinylpyrrolidone (PVP)/polyacrylonitrile (PAN) macroporous thick mat as the support layer. The hierarchical/asymmetric porous structure of the heterolayered nanomat is rationally designed with consideration of the trade-off between leakage current and ion transport rate. The TPY (to chelate Mn(2+) ions) and PVP (to capture hydrofluoric acid)-mediated chemical functionalities bring a synergistic coupling in suppressing Mn(2+)-induced adverse effects, eventually enabling a substantial improvement in the high-temperature cycling performance of cells.

Hybrid nanoparticles composed of multiple components can offer unique opportunities for understanding the nanoscale mechanism and advanced material applications. Here, we report the synthesis of heterodimeric silver-carbon dot nanoparticles (Ag-CD NPs) where the Ag NP is grown on the surface of CDs derived from polysaccharides, such as chitosan and alginate, through the photoelectron transfer reaction between CD and Ag(+) ions. The nanoscale interface between the Ag NPs and the CDs is highly tunable depending on the precursor of the CDs and the amount of additives, resulting in fine modification of photoluminescence of the CDs as well as the related surface plasmon resonance of the Ag NPs. This result demonstrates the critical role of the interface between the hybrid nanoparticles in governing the electrical and optical properties of respective nanoparticles.

The performance of fiber-reinforced composites is governed not only by the nature of each individual component comprising the composite but also by the interfacial properties between the fiber and the matrix. We present a novel layer-bylayer (LbL) assembly for the surface modification of a glass fiber to enhance the interfacial properties between the glass fiber and the epoxy matrix. Solution-processable graphene oxide (GO) and an aramid nanofiber (ANF) were employed as active components for the LbL assembly onto the glass fiber, owing to their abundant functional groups and mechanical properties. We found that the interfacial properties of the glass fibers uniformly coated with GO and ANF multilayers, such as surface free energy and interfacial shear strength, were improved by 23.6% and 39.2%, respectively, compared with those of the bare glass fiber. In addition, the interfacial adhesion interactions between the glass fiber and the epoxy matrix were highly tunable simply by changing the composition and the architecture of layers, taking advantage of the versatility of the LbL assembly.

We herein report a facile synthetic method for the preparation of goldcore, silver-shell nanoparticles (Au@Ag NPs) with tunable surface plasmon resonance (SPR) using the double hydrophilic block copolymer (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA), as a template (Au@Ag@DHBC NPs), and the utilization of their unique optical properties in polymer solar cells (PSCs). It is demonstrated that two different functionalities of DHBC facilitate the formation of the respective Au-core and Ag-shell NPs. Interestingly, the isolated core−shell NPs in solution are found to be transformed into coupled NPs that ultimately exhibit the transition of intrinsic plasmonic properties to a wide range in the visible spectrum. Furthermore, plasmonic Au@Ag@DHBC NPs are effectively integrated into the active layer of PSCs, which remarkably enhance the power conversion efficiency (PCE) up to 9.0% (16% enhancement) because of the strong plasmonic effect of the coupled NPs and the thin polymeric layer surrounding the NPs. This study suggests the widespread potential application of DHBCs as a template for the synthesis of novel core−shell nanostructures. We anticipate that this approach will provide new means for creating a variety of plasmonic nanomaterials in various fields of optoelectronic devices. ■ INTRODUCTIONThe emergence of plasmonics in nanoscale materials has renewed interests in the fundamental understanding of localized surface plasmons, which arise from collective and coherent oscillations of the conduction electrons in resonance with the incident light frequency on the surface of a metal nanoparticle (NP). 1−3 The creation and examination of numerous metal NPs have demonstrated the importance of each parameter, such as size, shape, and assembly, on tailoring their intrinsic plasmonic characteristics. 4−15 Novel metal nanostructures and their alloys have been the subject of intensive research owing to their interesting plasmonic behavior, including localized surface plasmon resonance (LSPR), surface-enhanced Raman scattering (SERS), and metal-enhanced fluorescence, which are useful for various applications toward biosensors, bioimaging, catalysis, thermal therapy, and optoelectronic devices, such as solar cells and light emitting diodes. 16−22 In particular, plasmonic metal NPs have received significant attention in polymer solar cells (PSCs) applications because their LSPR effect can lead to enhancement of incident light absorption and improvement of intrinsic scattering power for higher efficiency of solar cells. Among many novel metal NPs, gold and silver possess very effective plasmonic effects to trap incident light, which exhibit relatively strong scattering in the visible range. 23,24 However, attempts at obtaining high efficiency in PSCs by employing the SPR effect are limited because of the narrow resonant wavelength region of metal nanostructures. 2 In addition, direct integration of metal NPs into the active layer of PSCs often leads to exciton quenching in the system, 25,26 which inevitably re...

The coil-to-globule transition of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) in aqueous solution was investigated by all-atomistic molecular dynamics simulations. The polymer consistent force field (PCFF) was applied to the PDMAEMA model with a proper protonation state. The structural analysis indicates a distinct difference in the hydration state of particular functional groups of PDMAEMA as well as in the conformational state of PDMAEMA below and above the lower critical solution temperature (LCST). In particular, by monitoring the motion of water molecules, we observe that water molecules in the vicinity of the carbonyl group are relatively restricted to the motion in the globule state due to the extended relaxation time of hydrogen bonds among water molecules. The degree of protonation was also adjusted to study the effect of protonation on the conformational state of PDMAEMA.

With its superior electrical, optical, thermal, and mechanical properties, graphene offers a versatile platform for fabricating innovative hybrid composite materials with diverse potential applications. The preparation of graphene-based composites, particularly as thin films with nanoscale precision, is highly important for fabricating electrodes for energy and electronic devices as well as for facilitating understanding of the interplay between each component within the composites. In this context, the layer-by-layer (LbL) assembly technique offers a simple and versatile process for the fabrication of highly ordered multilayer film structures from various types of materials in a controllable manner. This paper presents details of the preparation and functionalization of these materials and the techniques for the LbL assembly of different graphenebased nanocomposites using polymers and nanoparticles. We anticipate that the protocols presented in this paper will guide researchers in the reproducible assembly of various high-quality graphene-based nanocomposites for fundamental researches and for diverse potential applications.