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Crystals, Volume 4, Issue 4 (December 2014), Pages 427-515

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Research

Open AccessArticle Optical Effects Accompanying the Dynamical Bragg Diffraction in Linear 1D Photonic Crystals Based on Porous Silicon
Crystals 2014, 4(4), 427-438; doi:10.3390/cryst4040427
Received: 4 August 2014 / Revised: 26 September 2014 / Accepted: 26 September 2014 / Published: 14 October 2014
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Abstract
We survey our recent results on the observation and studies of the effects accompanying the dynamical Bragg diffraction in one-dimensional photonic crystals (PhC). Contrary to the kinematic Bragg diffraction, the dynamical one considers a continuous interaction between the waves travelling within a spatially-periodic
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We survey our recent results on the observation and studies of the effects accompanying the dynamical Bragg diffraction in one-dimensional photonic crystals (PhC). Contrary to the kinematic Bragg diffraction, the dynamical one considers a continuous interaction between the waves travelling within a spatially-periodic structure and is the most pronounced in the so called Laue geometry, leading to a number of exciting phenomena. In the described experiments, we study the PhC based on porous silicon or porous quartz, made by the electrochemical etching of crystalline silicon with the consequent thermal annealing. Importantly, these PhC are approximately hundreds of microns thick and contain a few hundreds of periods, so that the experiments in the Laue diffraction scheme are available. We discuss the effect of the temporal splitting of femtosecond laser pulses and show that the effect is quite sensitive to the polarization and the phase of a femtosecond laser pulse. We also show the experimental realization of the Pendular effect in porous quartz PhC and demonstrate the experimental conditions for the total spatial switching of the output radiation between the transmitted and diffracted directions. All described effects are of high interest for the control over the light propagation based on PhC structures. Full article
(This article belongs to the Special Issue Photonic Crystals)
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Open AccessArticle Crystal Structures of New Ammonium 5-Aminotetrazolates
Crystals 2014, 4(4), 439-449; doi:10.3390/cryst4040439
Received: 16 September 2014 / Revised: 30 October 2014 / Accepted: 13 November 2014 / Published: 19 November 2014
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Abstract
The crystal structures of three salts of anionic 5-aminotetrazole are described. The tetramethylammonium salt (P ) forms hydrogen-bonded ribbons of anions which accept weak C–H···N contacts from the cations. The cystamine salt (C2/c) shows wave-shaped ribbons of anions
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The crystal structures of three salts of anionic 5-aminotetrazole are described. The tetramethylammonium salt (P ) forms hydrogen-bonded ribbons of anions which accept weak C–H···N contacts from the cations. The cystamine salt (C2/c) shows wave-shaped ribbons of anions linked by hydrogen bonds to screw-shaped dications. The tetramethylguanidine salt (P21/c) exhibits layers of anions hydrogen-bonded to the cations. Full article
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Open AccessArticle Dialytic Separation of Bundled, Functionalized Carbon Nanotubes from Carbonaceous Impurities
Crystals 2014, 4(4), 450-465; doi:10.3390/cryst4040450
Received: 2 July 2014 / Revised: 31 October 2014 / Accepted: 7 November 2014 / Published: 20 November 2014
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Abstract
Separating functionalized single-wall carbon nanotubes (SWCNTs) from functionalized amorphous carbon is challenging, due to their polydispersity and similar physicochemical properties. We describe a single-step, dialytic separation method that takes advantage of the ability of heavily functionalized SWCNTs to bundle in a polar environment
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Separating functionalized single-wall carbon nanotubes (SWCNTs) from functionalized amorphous carbon is challenging, due to their polydispersity and similar physicochemical properties. We describe a single-step, dialytic separation method that takes advantage of the ability of heavily functionalized SWCNTs to bundle in a polar environment while maintaining their solubility. Experiments on functionalized SWCNTs were compared with functionalized, C60 fullerenes (buckyballs) to probe the general applicability of the method and further characterize the bundling process. This approach may simultaneously be used to purify a functionalization reaction mixture of unreacted small molecules and of residual solvents, such as dimethylformamide. Full article
(This article belongs to the Special Issue Carbon Nanostructures)
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Open AccessArticle Growth and Properties of Carbon Microcoils and Nanocoils
Crystals 2014, 4(4), 466-489; doi:10.3390/cryst4040466
Received: 26 September 2014 / Revised: 2 November 2014 / Accepted: 18 November 2014 / Published: 26 November 2014
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Abstract
Various types of coiled carbon filaments have been synthesized using chemical vapor deposition and other methods. These carbon filaments exhibit unique electrical and mechanical properties due to their versatile shapes and structures. To form coiled shapes, different types of catalyst compositions and reactive
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Various types of coiled carbon filaments have been synthesized using chemical vapor deposition and other methods. These carbon filaments exhibit unique electrical and mechanical properties due to their versatile shapes and structures. To form coiled shapes, different types of catalyst compositions and reactive gases have been explored. Generally, coiled carbon filaments are classified by coil diameter and shape (e.g., microcoil and nanocoil). In this review, coiled carbon filaments are classified into three growth mechanism categories: (1) bidirectional double helical growth; (2) bidirectional twisted growth; and (3) tip single helical or twisted growth. Next, their synthesis methods and hypothetical growth mechanisms are discussed. Then, their electrical and mechanical properties are listed. Finally, potential applications and uses of coiled carbon filament are mentioned. Full article
(This article belongs to the Special Issue Carbon Nanostructures)
Open AccessArticle Crystallization and Structure Determination of Fac-Triammin-Aquo-Oxalato-Cobalt (III)-Nitrate Monohydrate
Crystals 2014, 4(4), 490-497; doi:10.3390/cryst4040490
Received: 8 October 2014 / Revised: 17 November 2014 / Accepted: 19 November 2014 / Published: 28 November 2014
Cited by 1 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The title compound, fac-triammin-aquo-oxalato-cobalt(III)-nitrate monohydrate, fac-[Co(NH3)3(C2O4)(H2O)]NO3·H2O (2), was prepared according to an original synthetic protocol published exactly 100 years ago by Alfred Werner by dissolving
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The title compound, fac-triammin-aquo-oxalato-cobalt(III)-nitrate monohydrate, fac-[Co(NH3)3(C2O4)(H2O)]NO3·H2O (2), was prepared according to an original synthetic protocol published exactly 100 years ago by Alfred Werner by dissolving the indigo-blue non-electrolyte complex mer-triammin-chloro-oxalato-cobalt(III), mer-[Co(NH3)3(C2O4)Cl] (1), in boiling half-concentrated nitric acid. Contrary to the literature, it did not crystallize directly from the reaction mixture, but crystallization could be induced by saturating the solution with NaClO4. The structure of 2 has monoclinic (P21/n) symmetry. The crystal structure displays an extensive array of N–H···O and O–H···O hydrogen bonding. Full article
Open AccessArticle Plasmonic Photonic-Crystal Slabs: Visualization of the Bloch Surface Wave Resonance for an Ultrasensitive, Robust and Reusable Optical Biosensor
Crystals 2014, 4(4), 498-508; doi:10.3390/cryst4040498
Received: 17 July 2014 / Revised: 10 October 2014 / Accepted: 31 October 2014 / Published: 4 December 2014
Cited by 2 | PDF Full-text (16252 KB) | HTML Full-text | XML Full-text
Abstract
A one-dimensional photonic crystal (PhC) with termination by a metal film—a plasmonic photonic-crystal slab—has been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition simulating the molecular binding event. Visualization of the
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A one-dimensional photonic crystal (PhC) with termination by a metal film—a plasmonic photonic-crystal slab—has been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition simulating the molecular binding event. Visualization of the Bloch surface wave resonance (SWR) was done with the aid of plasmon absorption in a dielectric/metal/dielectric sandwich terminating a PhC. An SWR peak in spectra of such a plasmonic photonic crystal (PPhC) slab comprising a noble or base metal layer was shown to be sensitive to a negligible variation of refractive index of a medium adjoining to the slab. As a consequence, the considered PPhC-based optical sensors exhibited an enhanced sensitivity and a good robustness in comparison with the conventional surface-plasmon and Bloch surface wave sensors. The PPhC biosensors can be of practical importance because the metal layer is protected by a capping dielectric layer from contact with analytes and, consequently, from deterioration. Full article
(This article belongs to the Special Issue Photonic Crystals)
Open AccessArticle Synthesis and Crystal Structures of Azolo[b]1,3,4-Thiadiazinium Bromides
Crystals 2014, 4(4), 509-515; doi:10.3390/cryst4040509
Received: 29 October 2014 / Revised: 14 November 2014 / Accepted: 21 November 2014 / Published: 11 December 2014
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Abstract
Three azolo[b]1,3,4-thiadiazinium bromides were prepared from the respective N-amino-N'-methylazolethiones and phenacyl bromide, and their crystal structures were determined. 6-Phenyl-1-methylimidazo[2,1-b]1,3,4-thiadiazinium bromide (1) crystallized as methanol solvate (P21/n), 6-phenyl-1-methyl-1,2,4-triazolo[3,4-b]1,3,4-thiadiazinium bromide (2) as
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Three azolo[b]1,3,4-thiadiazinium bromides were prepared from the respective N-amino-N'-methylazolethiones and phenacyl bromide, and their crystal structures were determined. 6-Phenyl-1-methylimidazo[2,1-b]1,3,4-thiadiazinium bromide (1) crystallized as methanol solvate (P21/n), 6-phenyl-1-methyl-1,2,4-triazolo[3,4-b]1,3,4-thiadiazinium bromide (2) as hemi-ethanol solvate (P21/n), and 6-phenyl-1-methyl-1,2,4-triazolo[3,2-b]1,3,4-thiadiazinium bromide (3) solvent-free (P21/c). Interionic contacts were identified. Full article
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