Void Channels Research Articles

New Insight into Phase Formation of MxMg2Al(4+x)Si(5-x)O18:Eu2+ Solid Solution Phosphors and Its Luminescence Properties.

Here we reported the phase formation of MxMg2Al4+xSi5−xO18:Eu2+ (M = K, Rb) solid solution phosphors, where M+ ions were introduced into the void channels of Mg2Al4Si5O18 via Al3+/Si4+ substitution to keep the charge balance. XRD results revealed that the as-prepared phosphors with different M+ contents were iso-structural with Mg2Al4Si5O18 phase. The combined analysis of the Rietveld refinement and high resolution transmission electron microscopy (HRTEM) results proved that M+ ions were surely introduced into the intrinsic channels in Mg2Al4Si5O18. The emission peaks of MxMg2Al4+xSi5−xO18:Eu2+ (M = K, Rb) phosphors with various x values performed a systematic red-shift tendency, which was ascribed to the elongation of [MgO6] octahedra. The temperature stable photoluminescence and internal quantum efficiency (QE) of MxMg2Al4+xSi5−xO18:Eu2+ (M = K, Rb) phosphors were enhanced owing to the filling of M+ in the void channels suggesting a new insight to design the solid solution phosphors with improved photoluminescence properties.

Gallium Arsenate Dihydrate under Pressure: Elastic Properties, Compression Mechanism, and Hydrogen Bonding.

Gallium arsenate dihydrate is a member of a class of isostructural compounds, with the general formula M(3+)AsO4·2H2O (M(3+) = Fe, Al, In, or Ga), which are being considered as potential solid-state storage media for the sequestration of toxic arsenic cations. We report the first high-pressure structural analysis of a metal arsenate dihydrate, namely, GaAsO4·2H2O. This compound crystallizes in the orthorhombic space group Pbca with Z = 8. Accurate unit cell parameters as a function of pressure were obtained by high-pressure single-crystal X-ray diffraction, and a bulk modulus of 51.1(3) GPa for GaAsO4·2H2O was determined from a third-order Birch-Murnaghan equation of state fit to the P-V data. Assessment of the pressure dependencies of the unit cell lengths showed that the compressibility of the structure along the axial directions increases in the order of [010] < [100] < [001]. This order was found to correlate well with the proposed compression mechanism for GaAsO4·2H2O, which involves deformation of the internal channel void spaces of the polyhedral helices that lie parallel to the [010] direction, and increased distortion of the GaO6 octahedra. The findings of the high-pressure diffraction experiment were further supported by the results from variable-pressure Raman analysis of GaAsO4·2H2O. Moreover, we propose a revised and more complex model for the hydrogen-bonding scheme in GaAsO4·2H2O, and on the basis of this revision, we reassigned the peaks in the OH stretching regions of previously published Raman spectra of this compound.

Stabilization of Hexaborate Net with Mixed Co(II) Metal and Organic Cations: Synthesis, Rationale Characterization, Comparative Study and Enhancement of the Bioactivity

A new Co(II)-hexaborate containing [Co{B6O7(OH)6}2]2− building blocks decorated with 1-cyanopiperazinium organic cation; (C5H11N3)[Co{B6O7(OH)6}2]·4H2O (1-CPCoB6) was synthesized from aqueous solution and the crystals were grown by the slow evaporation technique and characterized by means X-ray diffraction, IR UV–Vis and fluorescence spectroscopy measurements, elemental analysis and TDA-TG thermal analysis. The powder and single crystal XRD analysis revealed that the isolated pure crystals belong to the triclinic system. The structure exhibits interesting porous 3D-hydrogen-bonded network built by [Co{B6O7(OH)6}2]2−monomers. The cyanopiperazinium dications are filled in the free void channels of the inorganic framework and interact by means extensive hydrogen bonds. This hydrated mixed hexaborate thermally decomposed in multiple steps involving dehydration and release of organic cation leading to a novel unknown phase which undergoes crystallization. Moreover, the fluorescent and antimicrobial properties of 1-CPCoB6 have also been carried out, showing a red photoluminescence and a promising enhancement of biological activity of reported material in comparison with its parent reactants.

Giant Negative Area Compressibility Tunable in a Soft Porous Framework Material.

A soft porous material [Zn(L)2(OH)2]n·Guest (where L is 4-(1H-naphtho[2,3-d]imidazol-1-yl)benzoate, and Guest is water or methanol) exhibits the strongest ever observed negative area compressibility (NAC), an extremely rare property, as at hydrostatic pressure most materials shrink in all directions and few expand in one direction. This is the first NAC reported in metal-organic frameworks (MOFs), and its magnitude, clearly visible and by far the highest of all known materials, can be reversibly tuned by exchanging guests adsorbed from hydrostatic fluids. This counterintuitive strong NAC of [Zn(L)2(OH)2]n·Guest arises from the interplay of flexible [-Zn-O(H)-]n helices with layers of [-Zn-L-]4 quadrangular puckered rings comprising large channel voids. The compression of helices and flattening of puckered rings combine to give a giant piezo-mechanical response, applicable in ultrasensitive sensors and actuators. The extrinsic NAC response to different hydrostatic fluids is due to varied host-guest interactions affecting the mechanical strain within the range permitted by exceptionally high flexibility of the framework.

Dimensionality-dependent oxygen reduction activity on doped graphene: Is graphene a promising substrate for electrocatalysis?

Graphene, a two-dimensional layer framework of sp2-hybridized carbon, has attracted tremendous attentions as a promising material for oxygen reduction reactions (ORRs) due to its ideal uniqueness of high surface area and electrical conductivity. Contrary to the general belief, however, graphene catalysts have shown poor catalytic activities compared with those of other carbon-based catalysts. Herein, to understand the low ORR kinetics on the graphene catalysts, the dimensionality of graphene catalysts is sequentially tuned from sheets (2D) to ribbons (1D) and to dots (0D), and then the accompanying changes in terms of physical and electrochemical properties are investigated. In ultraviolet photoelectron spectroscopy, an increment in electropotential is measured as the dimensionality of the graphene catalysts decreases, of which the result infers the enhanced kinetics of the electron transfer from the graphene catalysts to O2 (electropotential: 0D>1D>2D). However, ORR performance does not follow the order of electropotential, and the graphene ribbons show the best activity among the prepared graphene catalysts (ORR activity: 1D>0D>2D). Further electrochemical impedance spectroscopy studies demonstrate that ORR kinetics is primarily determined by charge transfer rates in the fabricated graphene electrodes, which are strongly related to the electrode configurations and thus also to the length-to-width ratios of the graphene catalysts. The graphene sheets and dots, of which the length-to-width ratios are almost 1, handily lay over each other, leading to an impedance of efficient charge transfers. This study suggests the importance of void channels in the fabricated graphene electrode, which have not previously been considered significantly as a factor for improving ORR activity on the graphene catalysts.

The three-dimensional coordination polymer poly[[aqua[μ4-2,2'-(diazene-1,2-diyl)dibenzoato]lead(II)] 1,2-bis(pyridin-4-yl)ethylene hemisolvate

A novel three-dimensional coordination polymer, {[Pb(C14H8N2O4)(H2O)]·0.5C12H10N2}n, has been synthesized by hydrothermal reaction of Pb(OAc)2·3H2O (OAc is acetate), 2,2'-(diazene-1,2-diyl)dibenzoic acid (H2L) and 1,2-bis(pyridin-4-yl)ethylene (bpe). The asymmetric unit contains a crystallographically independent Pb(II) cation, one L(2-) ligand, an aqua ligand and half a bpe molecule. Each Pb(II) centre is seven-coordinated by six O atoms of bridging-chelating carboxylate groups from L(2-) ligands and by one O atom from a coordinated water molecule. The Pb(II) cations are bridged by L(2-) ligands, forming [PbO2]n chains along the a axis. These chains are further connected by L(2-) ligands along the b and c axes to give a three-dimensional framework with a 4(12)6(3) topology. The channel voids are occupied by bpe molecules.

Assembling nanotubes with cyclic peptoids

Cyclic alpha-peptoids hold the attention of both synthetic and supramolecular chemists for their biostability and potential diversity but also for their elegant and intriguing architectures.[1] Peptoids differ from peptides in the side chains, which are shifted by one position along the peptide backbone to the nitrogen atom to give N-substituted oligoglycine. The lack of the amide proton prevents the formation of NH···OC hydrogen bonds and weaker interactions, as CH···OC hydrogen bonds and CH-pi interactions, play a key role. Inter-annular CH···OC hydrogen bonds can provide face to face or side by side arrangement of macrocycles mimicking beta-sheet secondary structure in proteins.[2] In particular, the role of side chains in the solid state assembly of peptoid macrocycles will be discussed to show how they can promote the formation of a peptoid nanotube by acting as pillars, extending vertically with respect to the macrocycle planes. [3] Examples of the solid state assembly of free and metallated cyclic peptoids will be reported to show their extreme versatility as building blocks for designing new materials, with novel chemical properties and defined biological activities. In particular the first crystal structure of a recently synthesized novel cyclic alpha-peptoid, containing open channels with a radius of approximately 7 Å, will be discussed as a case of the successful engineering of cyclopeptoid crystals. In figure it is shown the channel void surface as seen along the a axis (0.0003 au, CrystalExplorer 3.1). The results of recent variable temperature high resolution XRPD measurements performed at ESRF beamline ID31 will be also reported to highlight the unusual thermal stability of this class of compounds and how the mobility of the side chains may be exploited to prepare new functional materials. EU FP7-People- IRSES grant number 319011 is gratefully acknowledged.

Effects of inorganic salts on the morphological, structural, and electrochemical properties of prepared nickel-rich Li[Ni0.6Co0.2Mn0.2]O2

The cathode active materials Li[Ni0.6Co0.2Mn0.2]O2 are synthesized using different inorganic salts, sulfate [NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O], nitrate [M(NO3)2·6H2O (M = Ni, Co, Mn)] and acetate [M(CH3COO)2·4H2O (M = Ni, Co, Mn)]. The X-ray diffraction (XRD) patterns indicate that sulfate and nitrate starting materials formed a well-ordered hexagonal α-NaFeO2 layered structure (space group: 166, R3¯m). However, acetate starting material is led to a poorly layered structure compared to the other materials. Field emission scanning electron microscope (FE-SEM) images show that sulfate and acetate starting materials formed nano-sized primary particles with a size of about 200–500 nm and 300 nm, and void channels. However, the primary particles with a size of 300 nm from nitrate starting material agglomerate together to form micro-sized secondary particles. The initial discharge capacities of the sulfate, nitrate, and acetate starting materials are 138.3, 142.4, and 135.9 mAh g−1 at 1 C-rate in the voltage range 3.0–4.3 V vs. Li/Li+, respectively. The discharge capacity retentions of sulfate, nitrate, and acetate starting materials are 92.5%, 63.9%, and 78.1% at 1 C-rate after 50 cycles, and 83.2%, 48.0%, and 71.7% at 6 C-rate after 100 cycles, respectively.

Space charge neutralization by electron-transparent suspended graphene

Graphene possesses many fascinating properties originating from the manifold potential for interactions at electronic, atomic, or molecular levels. Here we report measurement of electron transparency and hole charge induction response of a suspended graphene anode on top of a void channel formed in a SiO2/Si substrate. A two-dimensional (2D) electron gas induced at the oxide interface emits into air and makes a ballistic transport toward the suspended graphene. A small fraction (>~0.1%) of impinging electrons are captured at the edge of 2D hole system in graphene, demonstrating good transparency to very low energy (<3 eV) electrons. The hole charges induced in the suspended graphene anode have the effect of neutralizing the electron space charge in the void channel. This charge compensation dramatically enhances 2D electron gas emission at cathode to the level far surpassing the Child-Langmuir's space-charge-limited emission.

Channel reusability for burst scheduling in OBS networks

This paper presents a novel channel scheduling policy for optical burst switching networks called least reusable channel (LRC). LRC decides to which interval of the output channel (void) an incoming burst should be allocated on the basis of reuse of the remaining voids. LRC dynamically uses information available to make allocation decisions. It is shown here that LRC produces lower blocking probability and distributes losses more uniformly among routes than do other existing scheduling policies.

A three-dimensional coordination polymer of 3-(3,5-dicarboxybenzyloxy)benzoic acid with zinc

The synthesis is reported of the tricarboxylic acid 3-(3,5-dicarboxybenzyloxy)benzoic acid (H₃L) and the product of its reaction under solvothermal conditions with ZnII cations, namely poly[[μ₆-3-(3,5-dicarboxylatobenzyloxy)benzoato](dimethylformamide)-μ₃-hydroxido-dizinc(II)], [Zn₂(C₁₆H₉O7)(OH)(C₃H₇NO)]n, the formation of which is associated with complete deprotonation of H₃L. Its crystal structure consists of a single-framework coordination polymer of the organic L³⁻ ligand with ZnII cations in a 1:2 ratio, with additional hydroxide and dimethylformamide (DMF) ligands coordinated to the ZnII centres. The ZnII cations are characterized by coordination numbers of 5 and 6, being bridged to each other by hydroxide ligands. In the polymeric framework, the carboxylate- and hydroxy-bridged ZnII cations are arranged in coordination-tessellated columns, which propagate along the a axis of the crystal structure, and each L³⁻ ligand links to seven different ZnII centres via Zn-O bonds of two different columns. The coordination framework, composed of [Zn₂(L)(OH)(DMF)]n units, forms an open architecture, the channel voids within it being filled by the zinc-coordinating DMF ligands. This report provides the first structural evidence for the formation of coordination polymers with H₃L via multiple metal-ligand bonds through its carboxylate groups.

Horizontal slot waveguide channel for enhanced Raman scattering

Herein we characterize and experimentally demonstrate a new type of a horizontal slot waveguide structure for remarkably enhanced Raman scattering detection in nanometer-scale void channels. As the measurement sensitivity is one of the key limiting factors in nanofluidic detection, it is essential to search advanced solutions for such detection. Combining an all dielectric resonance waveguide grating and a surface enhanced Raman scattering (SERS) substrate in a close proximity it is possible to create high electromagnetic field energy hot zones within an adjustable slot region. This results in a strong enhancement in Raman scattering. We show the theoretical principles and demonstrate, with rhodamine 6G molecules, an approximately 20-fold enhancement compared to a conventional SERS substrate within the corresponding slot arrangement. We foresee potential applications for the proposed approach in the fields of medical, biological and chemical sensing, where the high detection sensitivity is essential due to integration with nanofluidic devices.

Coordination polymers of flexible poly-carboxylic acids with metal ions. IV. Syntheses, structures, and magnetic properties of polymeric networks of 5-(3,5)-(dicarboxybenzyloxy)isophthalic acid with Cd(ii), Cu(ii), Co(ii) and Mn(ii) ions

Four new framework solids consisting of coordination polymers [Cd2(L)(H2O)2(DMA)]n (1), [Cu2(L)(H2O)2]n (2), [Co2(L)(H2O)5]n (3) and [Mn2(L)(H2O)5]n (4) (H4L = 5-(3,5-dicarboxybenzyloxy)isophthalic acid; DMA = dimethyl acetamide) have been synthesized under hydro(solvo)thermal conditions and characterized by X-ray crystallography. In all cases, the metal-ion connectors consist of di-nuclear clusters. The fully de-protonated flexible tetradentate organic linker assumes a flat conformation with laterally oriented carboxylate functions in 1 and 2, but a twisted conformation with one carboxyphenyl residue rotated by nearly 90° with respect to the other in the isomorphous structures of 3 and 4. The resulting polymeric metal–organic lattices in 1 and 2 are perforated by wide (accounting for more than 50% of the crystal volume) solvent-accessible channel voids. In 3 and 4 the organic linker is characterized by tetrahedral tetra-carboxylate functionality, inducing the formation of open polymeric architectures with diamondoid geometries which interweave into one another in the crystal to fill most of the empty space. The remaining voids are filled by molecules of water. Thermal analysis (TGA and DTA) features of 1–4, nitrogen gas sorption behavior of 2 and solid-state variable temperature magnetic susceptibility data of 3 and 4 are reported as well.

Interplay of Metallophilic Interactions, π–π Stacking, and Ligand Substituent Effects in the Structures and Luminescence Properties of Neutral PtIIand PdIIAryl Isocyanide Complexes

Packing interactions in the crystal structures of a series of cis-M(CNAr)(2)Cl(2) complexes (M = Pt, Pd; Ar = substituted phenyl) were examined and correlated with the luminescence properties of the Pt complexes. The structures of the PhNC and p-tolyl isocyanide complexes exhibit extended chains of metallophilic interactions with M···M distances of 3.24-3.25 and 3.34 Å, respectively, with nearly isostructural Pt and Pd compounds. Both structure types contain void channels running parallel to the M···M chains. The channels are 3-4 Å wide and vacant for the phenyl structures, while those in the p-tolyl structures are up to 7.6 Å wide and contain water. These channeled structures are stabilized by a combination of metallophilic bonding and aryl π-π stacking interactions. The Pt structure with 4-F substituents also features extended Pt···Pt chains, but with longer 3.79 Å distances alternating with shorter 3.37 Å contacts. Structures with 4-CF(3) and 4-OMe substituents exhibit mostly isolated dimers of M···M contacts. In complexes with 2,6-dimethylphenyl isocyanide, steric hindrance precludes any short M···M contacts. The primary effect of aryl substitution is to provide alternative packing motifs, such as CF(3)···π and CH(3)···π interactions, that either augment or disrupt the combination of metallophilic contacts and π-π stacking needed to stabilize extended M···M chains. Differences in the Pt and Pd structures containing 4-F and 4-OMe substituents are consistent with a higher driving force for metallophilic interactions for Pt versus Pd. The M-C and M-Cl bond distances indicate a slightly higher trans influence for aryl isocyanides bound to Pt versus Pd. The three extended Pt···Pt chain structures display luminescence assignable to (dσ*→pσ) excited states, demonstrating the existence of substantial orbital communication along the metal-metal chains. Face-indexing shows that the preferred crystal growth axis is along the metal-metal chains for the luminescent structures. Variable temperature structural studies showed that both M···M and π-π interactions contract upon cooling. Overall, this study suggests that synergy with π-π and other interactions is necessary to stabilize extended M···M chain structures. Thus, efforts to design functional materials based on metallophilic bonding must consider the full array of available packing motifs.

An open calculation of RD-14M small-break LOCA experiments using CATHENA code

The open calculations of two Small Break Loss of Coolant Accident (SBLOCA) experiments in the RD-14M integral test facility are performed as an International Atomic Energy Agency (IAEA) activity of International Collaborative Standard Problem (ICSP) with the objective to benchmark and validate the thermal–hydraulic analysis code against qualified data for Heavy Water Reactor (HWR) systems. This ICSP started with the first meeting of the participants in Vienna in 2007 November. Two tests were selected for this activity, test B9006, a 7-mm inlet header break experiment with pressurized accumulator emergency coolant injection, performed in 1990, and test B9802, a 3-mm inlet header break experiment, performed in 1998, to provide data with full channel power to study boiling in the channels and condensation in the steam generators. The previously performed blind simulations demonstrated that the CATHENA code is capable of adequately predicting the primary pressure depressurization, channel flow rate, channel voiding for tests B9006 and B9802, and the high pressure core injection flow by CATHENA accumulator model and switching time from high pressure to low pressure injections for test B9006. However, several significant discrepancies between the code predictions and the measurement data were noted, and attributed to the input errors and the code models relevant to post-dryout (PDO) heat transfer phenomena in the heated channels of test B9802. Therefore, the open calculations are performed to allow correction of previous blind calculations in the present study. These open calculations include the Senaratne and Leung model with the optimized coefficients of its correlation for the test B9802, which can predict more accurately the onset of sustained dryout on the surface of the heater rods. The improvement of the open calculation results are shown by comparing them with the test data and also with the blind calculation results.

Dielectric elastomer and ferroelectret films combined in a single device: how do they reinforce each other?

Dielectric elastomers (DE) are soft polymer materials exhibiting large deformations under electrostatic stress. When a prestretched elastomer is stuck to a flat plastic frame, a complex structure that can be used as an actuator (DEA) is formed due to self-organization and energy minimization. Here, such a DEA was equipped with a ferroelectret film. Ferroelectrets are internally charged polymer foams or void-containing polymer-film systems combining large piezoelectricity with mechanical flexibility and elastic compliance. In their dielectric spectra, ferroelectrets show piezoelectric resonances that can be used to analyze their electromechanical properties. The antiresonance frequencies (fp) of ferroelectret films not only are directly related to their geometric parameters, but also are sensitive to the boundary conditions during measurement. In this paper, a fluoroethylenepropylene (FEP) ferroelectret film with tubular void channels was glued to a plastic frame prior to the formation of self-organized minimum-energy DEA structure. The dielectric resonance spectrum (DRS) of the ferroelectret film was measured in-situ during the actuation of the DEA under applied voltage. It is found that the antiresonance frequency is a monotropic function of the bending angle of the actuator. Therefore, the actuation of DEAs can be used to modulate the fp of ferroelectrets, while the fp can also be taken for in-situ diagnosis and for precise control of the actuation of the DEA. Combination of DEAs and ferroelectrets brings a number of possibilities for application.

A New Correlation of Acid-Fracture Conductivity Subject to Closure Stress

Summary The conductivity of an acid-etched fracture depends strongly on void spaces and channels along the fracture resulting from uneven acid etching of the fracture walls. In this study, we modeled deformation of the rough fracture surfaces acidized in heterogeneous formations based on synthetic permeability distributions and developed a new correlation to calculate the acid-etched fracture conductivity. In our previous work, we modeled the dissolution of the fracture surfaces in formations having small-scale heterogeneities in permeability. The characterization of the correlated permeability fields of rock includes the average permeability, normalized correlation lengths in both horizontal and vertical directions, and normalized standard deviation. These statistical parameters have a significant influence on the fracture-etching profiles obtained from the model. Beginning with this fracture-width distribution, we have modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. The elastic properties of the rock, such as Young's modulus and Poisson's ratio, have effects on the size of the spaces remaining open after fracture closure. After the model yields the width profile under closure stress, the overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system. In this paper, we introduce our models and investigate the effects of permeability and mineralogy distributions and rock elastic properties on the overall conductivity of an acid-etched fracture. A new acid-fracture conductivity correlation is developed on the basis of many numerical experiments.

Micro X-ray CT를 이용한 글라스 비드의 3차원 간극 구조 정량화

무질서하고 불균질한 형상을 갖는 지반 재료 내 간극 구조는 하중에 의한 재료의 변형 및 간극 내 유체의 흐름 등 물리 역학적 거동에 중요한 영향 인자이다. 최근 들어 X-ray CT에 의한 비파괴 검사를 통해 지반 재료의 내부 구조를 마이크로미터 단위의 높은 해상도를 통해 평가하는 기법이 사용되고 있다. CT 이미지는 재료의 많은 정보를 포함하고 있음에도 그에 따른 이미지 해석 기법의 개발이 다소 미흡하여 2, 3차원 이미지의 정성적 관찰 및 간극비와 같은 거시적인 물성치 획득만이 이루어지고 있다. 본 연구에서는 연속적으로 획득된 글라스 비드의 2차원 CT 이미지에 기반하여 3차원 입자 및 간극 구조를 형성하고, 복잡한 간극구조를 간극셀과 간극채널로 정량적 분리를 실시하였다. 이를 위해 좌표 변환법, 이진화, 들로네 삼각망, 그리고 유클리디안 거리변환법과 같은 이미지 프로세싱 기법을 3차원 CT 이미지에 적용하였고 불균질한 글라스 비드의 간극구조에 대해 정량적으로 간극셀의 분포 및 간극간의 연결도 평가가 가능함을 확인하였다. The random and heterogeneous pore structure is a significant factor that dominates physical and mechanical behaviors of soils such as fluid flow and geomechanical responses driven by loading. The characterization method using non-destructive testing such as micro X-ray CT technique which has a high resolution with micrometer unit allows to observe internal structure of soils. However, the application has been limited to qualitatively observe 2D and 3D CT images and to obtain the void ratio at macro-scale although the CT images contain enormous information of materials of interests. In this study, we constructed the 3D particle and pore structures based on sequentially taken 2D images of glass beads and quantitatively defined complex pore structure with void cell and void channel. This approach was enabled by implementing image processing techniques that include coordinate transformation, binarization, Delaunay Triangulation, and Euclidean Distance Transform. It was confirmed that the suggested algorithm allows to quantitatively evaluate the distribution of void cells and their connectivity of heterogeneous pore structures for glass beads.

Effect of Incorporation of Polypropylene on the Physico-Mechanical and Thermo-Mechanical Properties of Gelatin Fiber Based Linear Low Density Polyethylene Bio-foamed Composite

Gelatin fiber (10 wt%) based linear low density polyethylene (LLDPE) bio-foamed composite was fabricated using compression molding and physico-mechanical and thermo-mechanical properties were studied. Gelatin fiber was prepared from 20% gelatin-based aqueous solution by extrusion method. Polypropylene (PP) was blended (20—80 wt%) with LLDPE matrix in the 10% gelatin fiber based bio-foamed composites and their physico-mechanical and thermo-mechanical properties were investigated and compared with the control composite. It was found that with the increase of PP content in the LLDPE-based composites, the properties were found to improve significantly. Degradation test of the composites upto 24 weeks was performed in soil medium. Water uptake and thermo-mechanical properties of the composites were also studied. Void spaces and channels in the bio-foamed composites were observed from optical microscopic image.

Fine tuning of emission color of iridium(iii) complexes from yellow to red via substituent effect on 2-phenylbenzothiazole ligands: synthesis, photophysical, electrochemical and DFT study

Four novel iridium(III) complexes bearing biphenyl (7a-7c) or fluorenyl (7d) modified benzothiazole cyclometallate ligands are synthesized. In comparison with the yellow parent complex, bis(2-phenylbenzothiozolato-N,C(2')) iridium(III) (acetylacetonate) [(pbt)(2)Ir(acac)] (λ(PLmax) = 557 nm, φ(PL) = 0.26), 7a-7d show 20-43 nm bathochromic shifted orange or red phosphorescence in solution, with maximum photoluminescence (PL) quantum yield of 0.62, and PL lifetime of 1.8-2.0 μs. Meanwhile, the resulting complexes also exhibit intense orange or red phosphorescence of λ(PLmax) = 588-611 nm in solid films. The complex 7c with two tert-butyl substituents possesses the highest phosphorescent efficiency both in dilute solution and thin solid films, therefore may be a prospective candidate for both doping and host emitting electrophosphorescent material. Furthermore, despite the observation of severe oxygen quenching for 7a-7d in solution, 7a and 7c even show efficient emission intensity quenching by oxygen in their solid state due to the existence of void channels in crystals; consequently, they are promising molecular oxygen sensor reagents. Electrochemical measurement and DFT calculation results suggest that all these chelates own declined LUMOs of 0.1 eV relative to that of (pbt)(2)Ir(acac) owing to the contribution of the phenyl substituents; whereas only 7d shows a more destabilized HOMO (∼0.1 eV) compared with the parent chelate.