Brick-like Structure Research Articles

Symmetry of Pyridine Derivatives Controlled Two-Dimensional Nanostructural Diversity by Co-Assembly with Aromatic Carboxylic Acids.

The self-assembly behaviors of aromatic carboxylic acids are commonly investigated at the liquid/solid interfaces because of their rigid skeletons and both hydrogen-bond donors and receptors. However, self-assemblies of aromatic carboxylic acids with low symmetry and interactions between carboxylic acid and pyridine derivatives are worth exploring. In this work, the self-assembled structural transitions of a kind of low-symmetric aromatic carboxylic acid (H4QDA) are regulated by the coadsorption of two pyridine derivatives (DPE and T4PT) with different symmetry, which are investigated by scanning tunneling microscopy under ambient conditions. For the H4QDA/DPE system, the grid structure appears. For the H4QDA/T4PT system, the coassembled morphologies display an obvious concentration dependence. With the increase of solution concentration of T4PT, three coassembled patterns (network structure, chiral linear structure, and brick-like structure) are observed. Corresponding structural models suggest that the O-H···N hydrogen bonds have great contributions to stabilizing these coassembled structures. Our studies will help to explore the complexity, diversity, and functionality of multiple component systems and are conducive to further understanding the underlying mechanisms in the assembly process.

Electrochemical Performance of Chemically Integrated N-Doped Carbon Dots/Bi2MoO6 Nanocomposites for Symmetric Supercapacitors

Mixed transition-metal oxides (MTMOs) are attracting tremendous attention as a battery-type electrode due to their high electrical conductivity and structural stability. However, utilizing these electrodes in practical applications is hindered by capacity degradation, especially during the long-term cycle. These limitations could be overcome by constructing electrodes by introducing the carbonaceous material into the MTMO matrix. Accordingly, in this work, a facile hydrothermal method is employed to develop nitrogen-doped carbon dots (NCDs)-integrated bismuth molybdenum oxide (Bi2MoO6; BMO) (NCD/BMO) composites, where the concentration of NCDs is varied, such as 2, 5, 10, and 15 wt %. The structural and chemical state analyses of the samples confirm the formation of the orthorhombic BMO system and the chemically integrated NCD/BMO composites. The morphology analysis revealed a brick-like structure for bare-BMO with an average size of ∼100 nm and a rod-like morphology for the NCD/BMO composites, which is attributed to the interaction of NCDs with growing BMO particles leading to the rod-like formation of the resultant composites. The electrochemical performance of the developed materials is studied in a three-electrode and symmetric assembly system. Among the composites, the 10 wt % NCD/BMO (BMO–C10) composite exhibited an enhanced specific capacity of 561 C g–1 (155.8 mA h g–1) at a current density of 1 A g–1 in 6 M KOH electrolyte. Besides, the assembled symmetric device achieved an energy density and a power density of 44.2 W h kg–1 and 720 W kg–1, respectively, at a current density of 1 A g–1. In addition, the assembled symmetric device maintained excellent cyclic stability of ∼87.3% up to 10,000 cycles at 20 A g–1 current density. The obtained results demonstrate that the NCD/BMO composite could be an efficient battery-type electrode material for promising supercapacitor applications.

Phylogenomic characterization of the 2022 outbreak of monkeypox virus—The importance of sustained genetic surveillance

Phylogenomic characterization of the 2022 outbreak of monkeypox virus—The importance of sustained genetic surveillance

Porous In2O3 thick films as a low temperature NO2 gas detector

In this work, porous indium oxide is synthesized by hydrothermal method. The In2O3 has been structurally and optically characterized by using XRD, XPS, FESEM and TEM techniques. The morphological studies have revealed the growth of self-assembled In2O3 nanoparticles which helpts to form a brick-like structure. The porous In2O3 nanoparticles have provided the large number of active sites for the adsorption of gas molecules which resulted in a quick sensor response of 6877 for 10 ppm of NO2 gas at very low temperature of 50 °C. Remarkably, the In2O3 sensor has shown the detection of NO2 gas down to 60 ppb.

Anatomical and morphometric evaluation of the orbit, eye tunics, eyelids and orbital glands of the captive females of the South African painted dog (Lycaon pictus pictus Temminck, 1820) (Caniformia: Canidae).

In this study, we present the first data concerning the anatomical, morphometrical, histological and histochemical study of the orbit, eye tunics, eyelids and orbital glands in South African Painted Dogs (Lycaon pictus pictus). The study was performed using eyeball morphometry, analysis of the bony orbit including its morphometry, macroscopic study, morphometry, histological examination of the eye tunics and chosen accessory organs of the eye and histochemical analysis. The orbit was funnel shaped and was open-type. There was a single ethmoid opening for the ethmoid nerve on the orbital lamina. The pupil was round, while the ciliary body occupied a relatively wide zone. The iris was brown and retina had a pigmented area. The cellular tapetum lucidum was semi-circular and milky and was composed of 14–17 layers of tapetal cells arranged in a bricklike structure. In the lower eyelid, there was a single conjunctival lymph nodule aggregate. One or two additional large conjunctval folds were observed within the posterior surface of the upper eyelids. The superficial gland of the third eyelid had a serous nature. The third eyelid was T-shaped and was composed of hyaline tissue. Two to three conjunctival lymph nodul aggregates were present within the bulbar conjunctiva of the third eyelid. The lacrimal gland produced a sero-mucous secretion. A detailed anatomic analysis of the eye area in the captive South African Painted Dogs females showed the similarities (especially in the histological examination of the eyetunics and orbital glands) as well as the differences between the Painted dog and the other representatives of Canidae. The differences included the shape and size od the orbita with comparison to the domestic dog. Such differences in the orbit measurements are most likely associated with the skull type, which are defined in relation to domestic dogs. The presented results significantly expand the existing knowledge on comparative anatomy in the orbit, eye and chosen accessory organs in wild Canidae.

Highly sensitive detection of nitrobenzene by a series of fluorescent 2D zinc(ii) metal-organic frameworks with a flexible triangular ligand.

Four fluorescent zinc(ii) metal–organic frameworks, namely [Zn(HCIA)(4,4′-bipy)] (1), [Zn2(CIA)(OH)(1,4-bibz)1.5]·H2O (2), [Zn(CIA)(OH) (4,4′-bbpy)] (3), and [Zn2(HCIA) (4,4′-bimp)]·H2O (4), were prepared hydrothermally with a flexible triangular ligand (H3CIA) and a series of linear N-donor ligands (H3CIA = 5-(2-carboxybenzyloxy) isophthalic acid, 4,4′-bipy = 4,4′-bipydine, 1,4-bibz = 1,4-bis(1-imidazoly)benzene; 4,4′-bbpy = 4,4′-bis (imidazolyl) biphenyl; 4,4′-bimp = 4,4′-bis (imidazole-1-ylethyl) biphenyl). Structural analyses revealed that complex 1 exhibited a 2D brick-like network structure based on the basic bimetallic ring, 2 was also a 2D interspersed structure from the 1D tubular structure, compound 3 possessed a 2D (4,4) network with 4,4′-bbpy occupying the holes, and complex 4 displayed a 2D network from the 1D ladder-like chain. The thermal stabilities and fluorescent properties of these complexes were investigated in the solid state. The fluorescent sensing experiments revealed that all Zn-MOFs could highly sensitively detect nitrobenzene in aqueous solution, which indicated that these materials can be used as fluorescent probes for the detection of nitrobenzene.

A novel hollow core terahertz refractometric sensor

A novel hollow core photonic crystal fiber (PCF) based on Zeonex is proposed for sensing in the terahertz frequency range. A high level of asymmetry is introduced in the cladding by using a brick-like structure with identical square shaped air cavities. By filling the core with analytes of different refractive indices, the sensing characteristics of the fiber are numerically investigated using the finite element method (FEM) based COMSOL v5.3 software. The simulation results show that the proposed PCF displays a sensitivity as high as 98.9% and a minimum confinement loss of 5.5 × 10−10 cm−1 at an operating frequency of 2 THz. In addition, the fiber also shows ultra-low effective material loss (EML), high birefringence, large modal effective area and high numerical aperture at the optimum design conditions. The practical implementation of the fiber using different fabrication technologies is also discussed in detail. The excellent sensing performance and the design simplicity of the proposed PCF makes it highly suitable for use as a chemical sensor in different industrial and medical sectors.

Lightweight and flexible MXene/CNF/silver composite membranes with a brick-like structure and high-performance electromagnetic-interference shielding.

With the increasing global electromagnetic pollution, it is more and more important to develop lightweight, flexible, and high electromagnetic shielding materials. Two-dimensional (2D) transition metal material MXenes have good conductivity and excellent electromagnetic shielding performance. Herein, a facile and effective method is reported to synthesize lightweight and flexible MXene/CNF/silver (MCS) composite membranes with a brick-like structure and high-performance electromagnetic interference shielding. MCS composite membranes have an electromagnetic shielding performance of ≈50.7 dB due to MXene self-reduction of silver nanoparticles and the brick-like structure, compared with that of MXene/CNF (MC) membranes (≈14.98 dB). In addition, the MCS composite membranes exhibit super-thin thickness (46 μm) and good tensile strength (up to 32.1 MPa), and their good mechanical properties are attributed to the addition of CNFs. Moreover, the MCS composite membranes show good electrical conductivity (588.2 S m−1). Therefore, MCS composite membranes that are lightweight and flexible and have high electromagnetic shielding performance can replace other electromagnetic shielding materials and be used in aerospace, weapon equipment, and wearable smart materials.

One-pot solvothermal synthesis of rGO-CAS nanobrick composites with enhanced photoelectric properties

A facile and efficient one-pot solvothermal synthesis of reduced graphene oxide-CuSbS2 (rGO-CAS) nanobrick composite has been processed using ethylenediamine as reaction medium. In this case reduction of GO and the formation of CAS nanobricks on the surface of GO occurs simultaneously. The structural and morphological confirmation of the GO reduction and composite formation have been characterized using X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) analysis. Highly crystalline CAS material with orthorhombic structure in the composite has been observed through structural analysis. SEM micrographs reveal the brick-like structure of the CAS nanocrystals, which are well attached onto the individual layers of the graphene sheets. Improved optical absorption of the composite has been studied by absorption spectroscopy and the band gap tailoring of CAS nanobricks has also been achieved with GO matrix. XPS analysis verify the valence state of the composite material to be Cu+Sb3+(S2−)2. The composite also exhibits a remarkable photoelectric response due to increased surface to volume ratio. The good electron trapping, shuttling ability of GO resulted in an efficient separation of the photo-excited charge carriers from rGO-CAS nanobrick composites. The photocurrent demonstrated by the composite is 46% higher than that of the bare CAS nanobricks.

The fabrication of solid state dye-sensitised solar cells with I2 doped CuI as the hole conductors

The fabrication (ss-DSSC) were done by employing the iodine doped CuI (I2:CuI) as the hole conductors. The hole conductor deposition was done by varying the I2:CuI weight in order to investigate its effect to the device performance. The brick-like structure with smooth faces and sharp edges were seen for the doped thin films. The high electrical resistivity of I2:CuI thin films were observed compared to the undoped CuI thin films which is caused by the surface traps create by iodine doping. The ss-DSSC fabricated with undoped CuI hole transport layer shows the highest efficiency of 1.05% which is in a good agreement with the resistivity value of CuI thin films. The cell fabricated with 40 mg I2:CuI shows the lowest conversion efficiency of 0.45%. The crystals size of CuI and its degree of crystallisation are greatly affect the solar cells performance.

Structures and standard molar enthalpies of formation of a series of Ln(III)–Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

Fifteen lanthanide–copper heteronuclear compounds, formulated as [CuLn2(pzdc)4(H2O)6]·xH2O (1–6(x=2), 8(x=3), 9–10(x=4)); [CuLn2(pzdc)4(H2O)4]·xH2O (7, 12–13, 15(x=4), 14(x=5), 11(x=8)) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H2pzdc (C6H4N2O4)=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with {4.62}2{42.62.82}{63}2{65.8}2 topology. Using 1molcm−3 HCl(aq) as calorimetric solvent, with an isoperibol solution–reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state.

Fabrication of noncovalently functionalized brick-like β-cyclodextrins/graphene composite dispersions with favorable stability

Noncovalently functionalized β-cyclodextrins (β-CDs)/graphene composite dispersions have been fabricated through layer-by-layer self-assembly. Scanning electron microscope and transmission electron microscopy characterization confirm that the β-CDs/graphene composites possess brick-like sandwich-type structure. X-ray diffraction results illustrate that β-CDs covering on the surface of graphene possess channel-type structures. Moreover, the obtained β-CDs/graphene composites exhibit good dispersibility in common polar solvents and could exist for several weeks. In particular, the composites could be dispersed well in water at concentrations up to 2 mg mL−1 and stably exist at pH values from 4 to 12. The facts indicate that there exist certain forces between graphene and β-CDs. In order to clarify the interaction between them, we adopt a molecular mechanics (MM) method to evaluate the driving force. According to MM simulations, van der Waals forces should be the driving force for the formation of the well-defined β-CDs/graphene composites, and hydrogen-bonding interaction between adjacent β-CD molecules is another driving force for the formation of this stable graphene dispersion, which is similar to that of the β-CDs/carbon nanotubes composite. But the binding energy of the β-CDs/graphene composite is larger than that of the latter, suggesting much stronger interaction between graphene and β-CD molecules due to the two-dimensional flat-structure of graphene offering more and efficient sites to interact with β-CD molecules compared to carbon nanotubes with large interfacial curvature. These theoretical data for the existence of these interactions are further confirmed by experimental results from Raman and thermogravimetric analysis-differential scanning calorimetry.

The Photovoltaic Performance of Doped-CuI Hole Conductors for Solid State Dye-Sensitized Solar Cells

The iodine doped copper (I) iodide (I2: CuI) at different weight of iodine dopant have been prepared to investigate its thin films properties and photovoltaic performance. A novel method of mist atomization technique has been used for the deposition of CuI materials. The structural and electrical properties of CuI thin films deposited on the glass substrates were studied. The thin films morphology examined by FESEM shows a variation of crystal size and structure. Brick-like structure with smooth faces and sharp edges were seen for the doped thin films. The CuI thin films at 30 mg of iodine doping shows the highest resistivity of 4.56 × 101 Ω cm which caused by the surface traps create by iodine doping. The photovoltaic performance of ss-DSSC on the effect of variation iodine doping was investigated. The ss-DSSC fabricated with undoped CuI materials shows the highest efficiency of 1.05% while the 40 mg I2 content shows the lowest conversion efficiency of 0.45%. The crystals size of CuI and its degree of crystallization are greatly contributed to the high filling fraction of the porous TiO2 layer and hence the cells performance.

X-ray Structure of Snow Flea Antifreeze Protein Determined by Racemic Crystallization of Synthetic Protein Enantiomers

Chemical protein synthesis and racemic protein crystallization were used to determine the X-ray structure of the snow flea antifreeze protein (sfAFP). Crystal formation from a racemic solution containing equal amounts of the chemically synthesized proteins d-sfAFP and l-sfAFP occurred much more readily than for l-sfAFP alone. More facile crystal formation also occurred from a quasi-racemic mixture of d-sfAFP and l-Se-sfAFP, a chemical protein analogue that contains an additional -SeCH2- moiety at one residue and thus differs slightly from the true enantiomer. Multiple wavelength anomalous dispersion (MAD) phasing from quasi-racemate crystals was then used to determine the X-ray structure of the sfAFP protein molecule. The resulting model was used to solve by molecular replacement the X-ray structure of l-sfAFP to a resolution of 0.98 A. The l-sfAFP molecule is made up of six antiparallel left-handed PPII helixes, stacked in two sets of three, to form a compact brick-like structure with one hydrophilic face and one hydrophobic face. This is a novel experimental protein structure and closely resembles a structural model proposed for sfAFP. These results illustrate the utility of total chemical synthesis combined with racemic crystallization and X-ray crystallography for determining the unknown structure of a protein.

Influence of film thickness on texture and electrical and optical properties of room temperature deposited nanocrystalline V2O5 thin films

Nanocrystalline V2O5 thin films have been grown at low temperature on glass substrates by dc magnetron sputtering using a vanadium metal target. Film thickness was found to have a great impact on the orientation, shape, and size of the crystallites of these films. X-ray diffraction (XRD) patterns of the films with a thickness of 110nm show a strong c-axis orientated crystal structure with a preferred (001) orientation, while those with a thickness of 315nm show mixed orientations (a-axis+c-axis). With further increase in film thickness, an a-axis orientation with predominant (200) reflection was observed in the XRD pattern. The shape of the crystallite changes from a rodlike to a bricklike structure with change in crystallographic orientation from (001) to (200). Atomic force microscopy results were also in agreement with the field emission scanning electron microscopy and XRD results. A direct correlation has been established between the semiconductor to metal transformation of V2O5 films and their crystallite size and orientation. The optical measurement also revealed a systematic band gap variation (from 2.50to2.20eV) with variation in film thickness.

Montmorillonite based artificial nacre prepared via a drying process

Taking advantage of the specific behaviour of Na/Ca montmorillonite in aqueous dispersion, textured films were prepared by progressive evaporation of dispersions with low concentrations of delaminated platelets. The increase of the concentration of ions during evaporation changes the nature of the clay mineral platelet face interactions from repulsive to attractive. After complete drying, a dense brick-like structure is obtained when a sodium salt is used as deflocculant. The bending strength of the textured film is strongly affected by cracks formation during drying, specially when the sample thickness increases. After optimisation, crack-free textured samples with a 140 μm thickness, 20 cm × 25 cm area and 120 MPa bending strength were obtained.

Knowledge-based expert systems for better vehicle aerodynamics simulation

From the missile-shaped design of the modern F1 Grand Prix racing car to the brick-like structure of a heavy truck, aerodynamics plays a crucial role in how well vehicles behave on the road and how efficiently they perform the tasks they are designed for.

Hydrothermal Syntheses, Structures and Luminescent Properties of Lanthanide-Zinc Coordination Polymers, [Ln2Zn(pzdc)4(H2O)6·2H2O]n (pzdc = pyrazine-2,3-dicarboxylate, Ln = Gd, Nd, Sm)

Abstract The hydrothermal reactions of Ln2O3, Zn(NO3)2·6H2O, pyrazine-2,3-dicarboxylic acid (H2pzdc) and H2O resulted in the formation of three isostructural coordination polymers [Ln2Zn(pzdc)4(H2O)6·2H2O]n (Ln = Gd, 1; Nd, 2; and Sm, 3). The crystal structures of complexes 1 and 2 were determined by X-ray diffraction methods. Compounds 1, 2 and 3 are isomorphous and crystallize in the monoclinic space group P21/n with a = 6.1196(2), b = 22.5318(8), c = 11.9617(1) Å, β = 91.766(2), V = 1648.56(8) Å3, Z = 2 for 1, a = 6.1644(3), b = 22.6577(12), c = 12.0384(6) Å, β = 91.513(2), V = 1680.8(2) Å3, Z = 2 for 2. X-ray diffraction analyses confirm that complexes 1 and 2 possess a 3-D brick-like framework structure, each framework being surround by metal atoms, with a size of 16.37×6.12 Å, accommodating two water molecules as guests. The Ln(III) ions in compounds 1 to 3 are coordinated by seven oxygen and two nitrogen atoms. In addition, the zinc(II) ions are bonded by two carboxyl oxygen, two nitrogen and two apical carboxyl oxygen atoms in an octahedral geometry. The excitation spectrum and luminescent properties of 1 and 3 were studied qualitatively.

Shaping of grain architecture in tungsten using selective doping

The purpose of this work is to experimentally demonstrate that overlapping grain structures can be generated and stabilized at high temperatures by embedding arrays of grain boundary barriers. In tungsten lamp wire, strings of embedded potassium bubbles stabilize an overlapping grain structure along the wire axis. This markedly increases its resistance to creep and rupture. Stabilized overlapping grain structures can be achieved in sheet components by selectively doping a material using a combination of ion implantation and diffusion bonding. In this method foils of polycrystalline matrix material are doped with an insoluble element (potassium) by the ion implantation technique. This establishes atomically dispersed potassium in the near-surface regions of the foils. The doped foils are diffusion bonded to form a laminate with embedded, discrete layers of dopant. During diffusion bonding, the dopant atoms diffuse, cluster, and form planar arrays of potassium bubbles. After diffusion bonding, the laminate is annealed for recrystallization. The grain boundaries migrate parallel to the bubble arrays, but are pinned in directions perpendicular to them. This establishes a stabilized, brick-like grain structure.

Exciton superradiance in aggregates: The effect of disorder, higher order exciton-phonon coupling and dimensionality

In this paper a detailed theoretical analysis is presented of the temperature dependent radiative decay in aggregates of pseudoisocyanine (PIC). Our approach extends the original linear exciton-phonon coupling model used by Spano, Kuklinsky, and Mukamel [Phys. Rev. Lett. 65, 212 (1990)] including static disorder and second order exciton-phonon interactions. It is shown that for a one-dimensional exciton model neither of these additional effects alone or in combination with linear electron–phonon coupling can explain the steep rise in radiative lifetime at 40 K observed in the J-aggregate of PIC. However, when the aggregate assembles into a two-dimensional bricklike structure its radiative dynamics can be simulated, with linear exciton-optical phonon coupling as the only source for exciton scattering. Exciton-phonon scattering transfers oscillator strength from the k=0 state to other band states and also generates a nonequilibrium population among the exciton states, which persists during the superradiant decay. These effects together explain the marked temperature dependence of the radiative lifetime of the PIC J aggregate. When disorder limits the coherence length at low temperatures to a few molecules, as seems the case in several light harvesting complexes, the exciton population can equilibrate on the time scale of the superradiance. This situation pertains to the strong collision limit of the master equation, where the radiative decay is insensitive to details of the electron–phonon coupling, but only senses change in the thermal population among the exciton states.