Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template.

Three-dimensional graphene architectures with periodic nanopores­reminiscent of zeolite frameworks­are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure. Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures. However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.

Patient's Satisfaction in Skeletal Class III Cases Treated With Two-Jaw Surgery Using Orthognathic Quality of Life Questionnaire: Conventional Three-Stage Method Versus Surgery-First Approach.

OBJECTIVE: To compare the quality of life (QoL) of Class III patients between conventional three-stage method (CTM) and surgery-first approach (SFA) using Orthognathic QoL Questionnaire (OQLQ). MATERIALS AND METHODS: The subjects consisted of 26 Class III patients treated with nonextraction and two-jaw surgery. They were divided into CTM group (N = 15) and SFA group (N = 11). They retrospectively rated the OQLQ scores of 4 domains (social relationship, facial esthetics, function, and awareness of dentofacial deformity) using 0 to 4 scale at initial (T0), just before surgery (T1), 3 month after surgery (T2), and at debonding (T3). Mann-Whitney test and Wilcoxon signed-rank test were performed for statistical analysis. RESULTS: After total OQLQ score of CTM group was deteriorated at T1 stage compared with T0 stage, it was improved at T2 and T3 stages (T0 = 53.9, T1 = 58.1, T2 = 23.5, and T3 = 11.6). Total OQLQ score of SFA group, however, was improved at T2 and T3 stages compared with T0 stage (T0 = 51.6, T2 =  3.1, and T3 = 11.4; T1 was omitted.). Orthognathic QoL Questionnaire scores and their amounts of change did not show any significant difference in each domain and at each stage between 2 groups (T0, T2, T3, ΔT2 - T0, ΔT3 - T2, ΔT3 - T0; all P > 0.05). Both groups showed large change in effect size (ES) of all domains with descending order during T3 - T0: facial esthetics, oral function, social relationship, and awareness of dentofacial deformity (CTM group: -3.97, -3.40, -2.23, -1.25; SFA group: -2.83, -2.33, -1.76, -1.73) CONCLUSIONS: SFA might have an advantage over CTM group in terms of no deterioration stage of OQLQ score.

Defect-free, size-tunable graphene for high-performance lithium ion battery.

The scalable preparation of graphene in control of its structure would significantly improve its commercial viability. Despite intense research in this area, the size control of defect-free graphene (df-G) without any trace of oxidation or structural damage remains a key challenge. Here, we propose a new scalable route for generating df-G with a controllable size of submicron to micron through sequential insertion of potassium and pyridine at low temperature. Structural and chemical analyses confirm that the df-G perfectly preserves the intrinsic properties of graphene. The Co3O4 (<50 nm) wrapped by ∼ 10.5 µm(2) df-G has unprecedented capacity, rate capability, and cycling stability with capacities as high as 1050 mAh g(-1) at 500 mA g(-1) and 900 mAh g(-1) at 1000 mA g(-1) even after 200 cycles, which suggests enticing potential for the use in high performance lithium ion batteries.

Imbricate scales as a design construct for microsystem technologies.

Spatially overlapping plates in tiled configurations represent designs that are observed widely in nature (e.g., fish and snake scales) and man-made systems (e.g., shingled roofs) alike. This imbricate architecture offers fault-tolerant, multifunctional capabilities, in layouts that can provide mechanical flexibility even with full, 100% areal coverages of rigid plates. Here, the realization of such designs in microsystems technologies is presented, using a manufacturing approach that exploits strategies for deterministic materials assembly based on advanced forms of transfer printing. The architectures include heterogeneous combinations of silicon, photonic, and plasmonic scales, in imbricate layouts, anchored at their centers or edges to underlying substrates, ranging from elastomer sheets to silicon wafers. Analytical and computational mechanics modeling reveal distributions of stress and strain induced by deformation, and provide some useful design rules and scaling laws.

Photo-configurable embossed liquid crystal alignment layer with high azimuthal anchoring strength.

Herein we describe a photo-alignment layer of improved azimuthal anchoring energy comparable to conventional rubbing method. In order to address the inherent low anchoring stability of photo-alignment layer, we applied embossing technique to conventional photosensitive polymer film, based on the cinnamoyl photoreactive groups, to introduce physical micro-groove effect for additional anchoring energy. From this, 2.5 × 10⁻4 J/m² of azimuthal anchoring energy was achieved, which is considered as synergistic effect from both photoinduced chemical interaction and physical microgroove alignment. In this study, we conducted systematic study on change in anchoring energy as a function of both aspect ratio of embossed pattern and UV exposure dose. We also demonstrated fabrication of sophisticated multi-domain structure of LC cells and discussed theoretical interpretation through LC simulation.

Directional photofluidization lithography for nanoarchitectures with controlled shapes and sizes.

Highly ordered metallic nanostructures have attracted an increasing interest in nanoscale electronics, photonics, and spectroscopic imaging. However, methods typically used for fabricating metallic nanostructures, such as direct writing and template-based nanolithography, have low throughput and are, moreover, limited to specific fabricated shapes such as holes, lines, and prisms, respectively. Herein, we demonstrate directional photofluidization lithography (DPL) as a new method to address the aforementioned problems of current nanolithography. The key idea of DPL is the use of photoreconfigurable polymer arrays to be molded in metallic nanostructures instead of conventional colloids or cross-linked polymer arrays. The photoreconfiguration of polymers by directional photofluidization allows unprecedented control over the sizes and shapes of metallic nanostructures. Besides the capability for precise control of structural features, DPL ensures scalable, parallel, and cost-effective processing, highly compatible with high-throughput fabrication. Therefore, DPL can expand not only the potential for specific metallic nanostructure applications but also large-scale innovative nanolithography.

Efficiency Enhancement by Insertion of ZnO Recombination Barrier Layer in CdS Quantum Dot-Sensitized Solar Cells.

In this investigation we report the formation of thin ZnO recombination barrier layer at TiO2/CdS interface aimed for the improvement in performance of CdS sensitized solar cell. The film was deposited upon nanocrystalline mesoporous TiO2 surface by following a simple chemical process and characterized, using UV-Visible spectroscopy, X-ray diffraction and electron dispersive X-ray measurements. The insertion of ZnO thin layer enhances the QDSC (Quantum dot sensitized solar cell) performance, contributed mainly by an increase in open circuit voltage (Voc) due to reduced electron back transfer from TiO2 conduction band. Moreover, the analysis of photovoltaic characteristics upon increasing the thickness of the ZnO film reveals that the ZnO recombination barrier layer with optimum thickness at porous TiO2/CdS interface proved to be an effective potential barrier for minimizing electron back recombination.

Blue laser-sensitized photopolymer for a holographic high density data storage system.

We present a new blue-sensitized photopolymer to achieve a higher storage density compared to green/red-recordable media. Photopolymers are prepared based on a two-chemistry system and their holographic recording properties are investigated. A matrix of long and flexible ether units of an epoxy precursor and a multi-crosslinkable amine hardener enhances energetic sensitivity and suppresses volume shrinkage effectively. Page-wise recording of 961 bits/page of digital data is demonstrated and long term recording stability is also verified for a period of roughly 2 months.

Simple approach for enhancement of light harvesting efficiency of dye-sensitized solar cells by polymeric mirror.

A Polymeric mirror from 1D photonic crystal exhibiting full specular reflection is applied on the exterior of the counter electrode of a dye-sensitized solar cells (DSSCs). Reflection of exiting light from the cell allows for the reuse of the light and thereby significantly increases the efficiency of the DSSCs (from 8.07% to 8.85%). Furthermore, it is also found to be effective even with incorporation of an internal scattering layer, which is widely used within a TiO2 anode layer for enhancing light trapping in DSSCs (from 9.17% to 9.53%).

UV-driven in-plane rotation of a liquid crystal director in poly(vinyl cinnamate) films having microscale grooves.

The micropatterned poly(vinyl cinnamate) (PVCi) alignment layers are fabricated by a solvent-assisted micromolding method. Without UV irradiation, the alignment layer can induce the unidirectional liquid crystal (LC) orientation, which is influenced by topography-based anchoring energies. With photodimerization of PVCi by UV irradiation, we could modulate the anchoring energies caused by chemical interactions of the alignment layer. It is observed that these two different contributions compete against each other in determining LC rotation on the surface of the alignment layer. The rotation angle of LC directors could be controlled from 45° to 70° by simply changing the UV exposure dose.

Control of liquid crystal pretilt angles by using organic/inorganic hybrid interpenetrating networks.

A new photoalignment method of controlling the pretilt angle of liquid crystals (LCs) by using organic/inorganic hybrid interpenetrating polymer networks (IPNs) is proposed and demonstrated. In the hybrid IPN alignment layer system, the competition between poly(vinyl cinnamate) (PVCi) favoring planar alignment and poly(dimethyl siloxane) (PDMS) favoring vertical alignment made it possible to achieve pretilt angle in a wide range from 0 degrees to 90 degrees, and adjust pretilt angle as a function of PDMS content. In addition, we achieved the high azimuthal anchoring energy at the intermediate pretilt angle by using PDMS as the vertical-aligning component.

Generation of pretilt angles of liquid crystals on cinnamate-based photoalignment layer by a simple directional peel-off process.

As an alternative to the rubbing method, the photoalignment method has been extensively developed for liquid crystal displays owing to its various advantages including the absence of any contamination problems, feasibility of multi-domain structure formation, and low temperature processing capability. However, cinnamate-based photo-reactive materials that are widely used in photoalignment suffer from several limitations including low pretilt angle and limited control of tilted-up direction of the liquid crystals compared to that of the rubbing process. In this work, we demonstrate a simple and convenient method to generate the pretilt angle, compared to that achieved via the rubbing method, by means of a simple directional peel-off process using a photo-reactive cinnamate oligomer having flexible molecular chain.

Multifunctional photoreactive inorganic cages for three-dimensional holographic data storage.

We demonstrate a holographic photopolymer based on multifunctional photoreactive inorganic cages, polyhedral oligomeric silsesquioxane (POSS). It is shown that a second photopolymerizable monomer, POSS, for the photopolymer, contributes to significantly enhance photosensitivity as well as refractive index modulation (Deltan). We also found that during the formation of holographic gratings, polymerization of POSS could effectively suppress volume shrinkage of photopolymer resin, owing to its filler-strengthening effect of inorganic cages accompanied with interpenetrating effect.

Holographic diffraction gratings with enhanced sensitivity based on epoxy-resin photopolymers.

Photopolymers are interesting materials to obtain high-quality performance for the volume holographic data storage with a low noise and high diffraction efficiency. In this paper, the recording of holographic diffraction gratings with a spatial frequency of 1285lines/mm in photopolymerizable epoxy resin materials is experimentally demonstrated. Diffraction efficiency near 92% and an energetic sensitivity of 11.7 x 10-3cm2/J are achieved by designing the proper structure of matrix and also optimizing photopolymer compositions. The effect of photopolymer compositions on the fundamental optical properties is also discussed.

Facile fabrication of close-packed microlens arrays using photoinduced surface relief structures as templates.

We demonstrate the cost-effective and facile method of fabricating close-packed microlens arrays using photoinduced two-dimensional (2-D) surface relief structures as original templates. 2-D surface relief structures are produced by successive inscription of two beams interference patterns with different grating vectors on azopolymer films. The employed exposure dose of 1st inscription stage and 2nd inscription stage are optimized to obtain symmetrical modulation heights. These photoinduced 2-D surface relief structures on azopolymer films are used directly to mold PDMS, and PDMS molds were then transferred onto photopolymer to imprint microlens arrays. Using this method, tetragonally and hexagonally close-packed microlens arrays are successfully fabricated in rapid and cost-effective way.

In situ micro-sized gel-forming injectable implant using biodegradable amphiphilic graft copolymer.

A synthesized graft polymer is used as a biodegradable polymer for an in situ gel-forming injectable implant system. The amphiphilic character of the polymer in the graft structure lowered the viscosity of the polymer solution, which enabled easy injection. A micro-sized gel can be obtained with this system, which has not been found for previous in situ gel-forming systems with poly[(D,L-lactide)-co-glycolide] copolymer. In addition, a protein particle embedded gel exhibits good in vitro drug release performance as a result of the enhanced stability and shorter diffusion length.

Nanoparticle-induced refractive index modulation of organic-inorganic hybrid photopolymer.

An organic-inorganic photopolymers have been studied for their potential in of reducing the volume shrinkage during photopolymerization and enhancing the dimensional stability of photopolymers. We demonstrate the diffraction efficiency of photopolymers could be significantly enhanced by the interfacial interactions induced at the surface of inorganic nanoparticles.

Synthesis, cytotoxicity and structure-activity relationship study of terpyridines.

For the development of novel antitumor agents, we designed and synthesized terpyridines, and their biological activities were evaluated. Although most of the newly prepared terpyridines showed strong cytotoxicity against several human cancer cell lines, [2,2';6',2"]-terpyridine displayed the most significant cytotoxicity.

Sustainable Redox Mediation for Lithium-Oxygen Batteries by a Composite Protective Layer on the Lithium-Metal Anode.

A synergic combination of a soluble -redox mediator and a protected Li metal -electrode to prevent the self-discharge of the redox mediator is realized by -exploiting a 2,2,6,6-tetramethylpiperidinyl 1-oxyl (TEMPO) redox mediator and an Al2 O3 /PVdF-HFP composite -protective layer (CPL). Stabilization of Li metal by simple CPL coating is effective at -suppressing the chemical reduction of the oxidized TEMPO and opens up the possibility of sustainable redox mediation for robust cycling of Li-O2 batteries.

Structural modulation of lithium metal-electrolyte interface with three-dimensional metallic interlayer for high-performance lithium metal batteries.

The use of lithium (Li) metal anodes has been reconsidered because of the necessity for a higher energy density in secondary batteries. However, Li metal anodes suffer from 'dead' Li formation and surface deactivation which consequently form a porous layer of redundant Li aggregates. In this work, a fibrous metal felt (FMF) as a three-dimensional conductive interlayer was introduced between the separator and the Li metal anode to improve the reversibility of the Li metal anode. The FMF can facilitate charge transfer in the porous layer, rendering it electrochemically more active. In addition, the FMF acted as a robust scaffold to accommodate Li deposits compactly in its interstitial sites. The FMF-integrated Li metal (FMF/Li) electrode operated with a small polarisation even at a current density of 10 mA cm(-2), and it exhibited a seven times longer cycle-life than that of an FMF-free Li electrode in a symmetric cell configuration. A Li metal battery (LMB) using the FMF/Li electrode and a LiFePO4 electrode exhibited a two-fold increase in cycling stability compared with that of a bare Li metal electrode, demonstrating the practical effectiveness of this approach for high performance LMBs.