Crystal Channels Research Articles

4-tert-Butyl-pyridinium chloride-4,4'-(propane-2,2-di-yl)bis-(2,6-di-methyl-phenol)-toluene (2/2/1).

In the title solvated salt, C9H14N+·Cl−·C19H24O2·0.5C7H7, two mol­ecules of 4,4′-(propane-2,2-di­yl)bis­(2,6-di­methyl­phenol) are linked via O—H⋯Cl hydrogen bonds to two chloride ions, each of which is also engaged in N—H⋯Cl hydrogen bonding to a 4-tert-butyl­pyridinium cation, giving a cyclic hydrogen-bonded entity centred at 1/2, 1/2, 1/2. The toluene solvent mol­ecule resides in the lattice and resides on an inversion centre; the disorder of the methyl group requires it to have a site-occupancy factor of 0.5. No crystal packing channels are observed.

Tubular structures bearing channels in organic crystals composed of adamantane-based macrocycles

Five macrocyclic molecules (1–5) were efficiently synthesized from the dimerization and trimerization of di-substituted adamantane derivatives, which were composed of three different aromatic units and two different linker groups. Three single-crystals were obtained from these macrocyclic molecules, including a set of pseudopolymorphs (3a and 3b) of macrocycle 3 and another macrocycle 5 (5a). Single crystal X-ray analysis revealed that the three monocyclic compounds were rectangular or square in shape with solvent molecules in the cavity. Macrocycle 3 in 3a formed stacks to produce tubular structures with channels that assembled into three-dimensional networks through CH/π interactions.

About the probability of close collisions during stochastic deflection of positively charged particles by a bent crystal

The probability of close interactions of high-energy positively charged particle with atoms in a bent crystal was considered as a function of the angle between the initial particle momentum and the bending plane. The results of simulation of particle motion presented in the article show the great efficiency of high-energy positively charged particle deflection by a bent crystal due to the stochastic deflection mechanism and strong reduction of the probability of close collisions during the stochastic deflection in comparison to the planar channeling in a bent crystal.

Spatially Controlled Channel Entrances Functionalization of Zeolites L

The spatially controlled channel entrances functionalization of disk shaped zeolite L crystals is described. Fluorescent dye or bioactive molecules are immobilized at one end of the channels of zeolite crystals and subsequently the other side of the crystals is derivatized with magnetic iron oxide nanoparticles. The asymmetrically functionalized crystals were used for the control of the movement of bacteria in solution.

Deflection of a 100-MeV positron beam by repeated reflections in thin crystals

The phenomenon of the deflection of a charged particle beam due to channeling in a bent crystal is thoroughly investigated and successfully applied for the extraction of the beam in high-energy accelerators, at the energies of about 10 GeV and higher. However, a big practical interest lies in the task of bending and extracting charged particles with energies below 1 GeV, for example, for the production of ultrastable beams of low emittance for medical and biological applications. That is why a novel crystal technique, namely thin straight crystal targets, is investigated in this article, using crystals as elements for extraction and collimation of the circulating beam in a ring accelerator. The advantages of reflection in straight crystals in comparison with bent crystal channeling consist in the small length of straight crystals along the beam that reduces the amount of nuclear interactions and improves the background. Experimental results were obtained for the bending of a 100 MeV positron beam with using five sequential straight crystals.

Structural transformation of confined iodine in the elliptical channels of AlPO4-11 crystals under high pressure

Iodine molecules confined in the elliptical nanochannels of AlPO4-11 crystals can only rotate in the plane passing through the major axis of the elliptical cross-section due to size confinement. This leads to different dynamic behaviors of iodine from those confined in round channels of AlPO4-5 crystals under ambient conditions. In this work, we use high pressure technology to manipulate the nanoscaled iodine species confined in the elliptical channels of AlPO4-11 crystals. In situ polarized Raman measurements and theoretical simulations have been carried out to study the topological geometry of the confined iodine species upon compression. It was found that the population of iodine chains could significantly increase at the expense of standing iodine molecules under pressure up to 6 GPa, due to the pressure-induced rotation of standing iodine molecules. Besides, the contraction of the host framework along the channel axis favors the formation of iodine chains and strengthens the interaction of neighbouring molecules in a chain, consequently leading to a frequency redshift of the corresponding Raman mode. The different transformation dynamics of the confined iodine in AlPO4-11 crystals upon compression, compared to those in round channels of AlPO4-5 crystals, have been discussed in terms of the unique nanochannels that offer the quasi two-dimensional nanoscaled confinement environment.

Cholanamide components for organic alloys; expanding the scope of nanoporous steroidal ureas

Amide-linked side-chains can substitute for esters in crystalline nanoporous steroidal ureas (NSPUs). This efficient conjugation method increases the versatility of NPSUs, and should aid the inclusion of complex functional units in the crystal channels.

A Multichannel Chemical Sensing Method Using Single Quartz Resonator and Micro Flow Channel

In this paper, the development of a multi chemical sensing method using a single quartz crystal resonator and micro flow channel has been reported. In the developed device, samples pass through two capacitors that are mounted as sensing parts in a microchannel with a time lag. Connecting the capacitors to the single quartz crystal resonator, one can obtain frequency change ΔF of the resonator as time lag signals depending on the relative permittivity of samples. The optimization of resonator diameter was also carried out in this paper. Using the proposed method, we can realize multi chemical sensing with a single resonator.

Aluminium chloride: A new aluminium source to prepare SAPO-34 catalysts with enhanced stability in the MTO process

The MTO process produces lower olefins from natural gas or coal via methanol, providing an interesting route to obtain valuable petrochemicals from carbon sources alternative to petroleum. Small-pore silicoaluminophosphate SAPO-34 has been proven an efficient catalyst for the MTO process, showing exceptionally high selectivity to lower olefins. However, these catalysts undergo rapid deactivation due to deposition of high molecular weight hydrocarbons on the pore entrances, which completely blocks the internal channels of the SAPO-34 crystals. In the present work, we explore the use of very dilute zeotype precursor solutions to reduce the size of the crystals of these materials, improving greatly their catalytic behaviour in the MTO process by increasing the catalyst life time.

An ultra-small heterostructure wavelength division multiplexer (WDM) with the ability to select two wavelengths from the s-band

In this article, a photonic crystal channel drop filter (CDF) based on \(2\times 3\) ring resonators is presented. At first, the effects of changing the radius of lattice rods and the lattice dielectric constant on the dropping efficiency of a 3-port CDF with one resonator are investigated. Then by developing this base structure, a new 4-port heterostructure CDF composed of two regions with rods made of silicone and germanium is presented, which can operate in the ‘S’ band of the communication window. The photonic crystal heterostructure CDF consists of a horizontal waveguide and two ring resonators that have been installed, in symmetry to the horizontal axis, in two regions with different refractive indices. These ring resonators act as energy couplers and capture at their resonant frequencies the electromagnetic energy which is propagated in the bus waveguide. For the analysis of transmission characteristics and the band structure of the filter, two methods have been employed: the two-dimensional Finite–difference time domain method and the Plane Wave Expansion method. In the final structure, dropping efficiencies of 97 and 89 % can be achieved at ports D and B, respectively, and also an acceptable quality factor can be obtained in the communication window. The overall size of this device is 174.14 \(\upmu \hbox {m}^{2}\). Due to its small size, this structure can be used in Wavelength Division Multiplexer applications in the Optical Integrated Circuits.

Modeling the deflection of relativistic particles in axial and planar channels of a silicon crystal

Modeling the deflection of protons and π−-mesons in axial and planar channels of a bent silicon crystal was performed by numerically solving the kinetic Fokker-Planck equation in the space of transverse coordinates and velocities, as well as in the space of transverse energies. We discuss the reasons of forming an angular distribution with two maxima for the beam of π−-mesons under planar channeling in a silicon crystal that was obtained as a result of simulation in our previous work. The modeling results in the space of transverse energies and in the phase space of transverse coordinates and velocities prove to be in rather good agreement for protons, but are somewhat different for π−-mesons.

Quenching and channeling of nuclear recoils in NaI(Tl): Implications for dark-matter searches

A new experimental evaluation of the quenching factor for nuclear recoils in NaI[Tl] is described. Systematics affecting previous measurements are addressed by careful characterization of the emission spectrum of the neutron source, use of a small scintillator coupled to an ultra-bialkali high quantum efficiency photomultiplier, and evaluation of non-linearities in the electron recoil response via Compton scattering. A trend towards a rapidly diminishing quenching factor with decreasing sodium recoil energy is revealed. Additionally, no evidence for crystal lattice channeling of low-energy recoiling ions is found in a scintillator of known crystallographic orientation. A discussion on how these findings affect dark matter searches employing NaI[Tl] (e.g., DAMA/LIBRA) is offered.

A New Two-Dimensional Photonic Crystal Channel Drop Filter Based on Two-Resonant Cavities

In this paper, a channel drop filter (CDF) is composed of two cubic lattice circular ring resonator cavities and point micro-cavities in a two-dimensional photonic crystal. The photonic band gap is calculated using the plane wave expansion (PWE) method and the optical characteristics of proposed structure are studying by the finite difference time domain (FDTD) method with perfectly matched layers (PMLs) acting as the boundary conditions . Two different wavelengths centered at 1773 nm and 1742 nm have been successful separation in this CDF. These demonstrate that our proposed structure is suitable for photonic integrated circuits (PICs) and coarse wavelength division multiplexing (WDM) optical communication systems.

Effect of fabrication tolerances on the performance of two-dimensional polymer photonic crystal channel drop filters: a theoretical investigation based on the finite element method

Guidelines for the design and fabrication of polymer photonic crystal channel drop filters for coarse wavelength division multiplexing are provided. A Fabry-Perot cavity consisting of a membrane-type slab photonic crystal, where a hole row perpendicular to the propagation direc- tion is removed, is considered. We selected nanoimprinting as the manu- facturing technique. The influence on the cavity performance of several key parameters, i.e., polymer core material, lattice geometry, defect length, and holes' radius, has been investigated in a device compliant with the requirement of the ITU-T G.694.2 standard. A detailed analysis of the fabrication tolerances has been carried out at 1551 nm. The maxi- mum acceptable drift of the geometrical parameters has been accurately evaluated by using the finite element method to prove that the fabrication tolerances do not significantly affect the performance of polymer filters for coarse wavelength division multiplexing, when manufactured by thermal nanoimprinting lithography. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI:

FROZEN IODINE MOLECULES IN NANO-PORES OF ZEOLITE SINGLE CRYSTALS

We review the recent study of novel optical properties of iodine molecules trapped inside the nano-channels of single zeolite crystals. It has been verified by Raman spectroscopy and molecular dynamics simulation that there are two favorite orientations of iodine molecules inside the AlPO 4-11 (AEL) and AlPO 4-5 (AFI) crystal channels: "lying" along the channel direction or "standing" inside the channel. Switching between the "lying" and "standing" configurations of iodine molecules inside the AEL crystals can be controlled by varying the density of water molecules inside the crystal channels. For extremely low iodine-loaded samples, the frozen "standing" iodine molecules in AEL crystals were observed whose Raman linewidth is independent of temperature. We also show that the radius of iodine atom can be determined from the fading nature and the broadening characteristics of overtones in Raman spectra of confined iodine molecules.

Simulations of electron channeling in bent silicon crystal

We report on the results of theoretical simulations of the electron channeling in a bent silicon crystal. The dynamics of ultra-relativistic electrons in the crystal is computed using the newly developed part [1] of the MBN Explorer package [2,3], which simulates classical trajectories of in a crystalline medium by integrating the relativistic equations of motion with account for the interaction between the projectile and crystal atoms. A Monte Carlo approach is employed to sample the incoming electrons and to account for thermal vibrations of the crystal atoms. The electron channeling along Si(110) crystallographic planes are studied for the projectile energies 195–855 MeV and different curvatures of the bent crystal.

DISCUSSION OF THE CENTER OF MASS MOTION IN A SYSTEM WITH THREE DEGREES OF FREEDOM

This paper considers the problem of the center of mass motion of three fermionic particles, e. g., equal nucleons (no spin), which can move only in the x-direction in the laboratory system. This system (with three degrees of freedom only) is transformed to a system where one coordinate is proportional to the center of mass coordinate. The center of mass moves in a harmonic oscillator potential. The basis set of wave functions is constructed with Hermite polynomials in part. As example we study the case of a quadratic intrinsic potential between the particles. The problem may be important for the motion of three nucleons in a crystal channel.

Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts

Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts.

Hydrothermal Synthesis, Crystal Structure and Characterization of New Coordination Polymer [Co2(pydc)2(H2O)6] n ·2nH2O

A coordination polymer of cobalt(II) containing the pyridine-2,5-dicarboxylate (pydc) ligand and having the composition [Co2(pydc)2(H2O)6]n·2nH2O was prepared by the hydrothermal method. The coordination polymer was characterised by FTIR, single crystal XRD, SEM, TGA–DTA, and N2 Temperature Programmed Desorption, Brunauer, Emmett and Teller surface area. The polymer contains two cobalt(II) ions with slightly distorted octahedral geometry. The carboxylate group at the 2-position of pyridine acts as a bridging ligand between two cobalt metal ions and this expansion leads to formation of a 1-D chain-like coordination polymer. The coordination polymer chains are packed together by well-directed hydrogen bonds to generate a three dimensional mesoporous network. The N2 TPD study shows that the polymer is mesoporous in nature and possesses slit-shaped mesopores with average pore size diameter of 17.78 nm. SEM micrographs show well-defined channels in the solid crystals confirming the porosity of polymer. Thermogravimetric studies indicate the robust nature of the polymer. The polymer undergoes thermal decomposition in well-defined steps leading to the formation of cobaltous oxide as the end-product.

Energy loss distributions of relativistic protons axially channeled in a bent silicon crystal

A detailed study of the energy loss distributions of the relativistic protons axially channeled in the bent<100>Si crystals is presented in this work. The bending angle was varied from 0 to 20μrad, while the crystal thickness was equal to 1mm. The proton energy was chosen to be 7TeV in accordance with the Large Hadron Collider (LHC) project, at the European Organization for Nuclear Research (CERN), in Geneva, Switzerland. The energy loss distributions of the channeled protons were generated using the numerical solution of the proton equations of motion in the transverse plane and the computer simulation method. An accurate energy loss model was used, which takes into account the trajectory dependence of the energy loss of protons during their motion through the crystal channels. Further, the dispersion of the proton’s scattering angle caused by its collisions with the electrons of the crystal and the divergence of the proton beam were taken into account. The calculated dependence of the number of dechanneled protons on the bending angle was excellently fitted by the Gompertz type dechanneling function.