Distinguishing of linkage isomers of lactotetra oligosaccharides by using the relative ion intensity analysis of post-source decay fragment ions in curved-field reflectron matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The native oligosaccharides of lacto-N-neotetraose (Gal beta1-4GlcNAc beta1-3Gal beta1-4Glc; LNnT) and lacto-N-tetraose (Gal beta1-3GlcNAc beta1-3Gal beta1-4Glc; LNT) were analyzed by using curved-field reflectron matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Since a curved-field reflectron TOFMS enables a simultaneous focusing of a wide mass range of metastable fragment ions, the relative ion intensities in the post-source decay (PSD) mass spectra can be discussed. The PSD mass spectra of LNnT and LNT were distinguishable in their relative ion intensities. In the case of LNT, beta-elimination could occur in the N-acetyl glucosamine (GlcNAc) at the C-3 position, which was bonded by galactose (Gal); however, it did not occur in LNnT. The 3-O elimination caused a difference in the relative ion intensities in the PSD mass spectra of LNnT and LNT. The beta1-3 glycosyl linkage cleaved more easily than the beta1-4 glycosyl linkage in the MALDI-PSD fragmentation. An analysis of the relative ion intensities in the MALDI-PSD mass spectra of oligosaccharides was very useful for distinguishing the linkage isomers and for characterizing the types of glycosyl linkages.     

Electron spin resonance study of γ-irradiated poly(methacrylic acid)

Low temperature relaxations in poly(methacrylic acid) (PMAA) have been studied by electron spin resonance (ESR) spectroscopy. The observed 8 line ESR spectra of irradiated PMAA in the temperature range 77-300K (LNT-RT) is attributed to the free radicals of the type ～ CH₂? CH? CH₃. Assignment of ESR spectra to free radicals has been made on the basis of magnetic parameters employed to simulate ESR spectra at different temperatures. Further, ESR spectra below LNT have been simulated, using the set of parameters employed to simulate the experimental spectrum at LNT. Magnetic parameters of the ESR spectra at LNT and below LNT indicate γ- and δ-relaxations of PMMA chains. © 1994 John Wiley & Sons, Inc.     

Mössbauer Investigation of FeSbO4

Mössbauer data are presented for FeSbO₄ at room temperature (RT) and liquid-nitrogen temperature (LNT). An interpretation of the relaxation phenomena in this compound at LNT is given which differs from previous conclusions (G. M. Bartenev et al. [9]) and shows a correlation with FeSbO₄ particle size. The results permit a more accurate evaluation of the phase composition of (Fe, Sb)O catalysts by means of Mössbauer spectroscopy.     

Formation and characterization of self-organized TiO2 nanotube arrays by pulse anodization

This paper describes TiO2 nanotube arrays prepared by anodic oxidation of Ti substrates using pulse voltage waveforms. Voltages were pulsed between 20 and -4 V or between 20 and 0 V with varying durations from 2 to 16 s at the lower limit of the pulse waveform. Ammonium fluoride or sodium fluoride (and mixtures of both) was used as the electrolyte with or without added medium modifier (glycerol, ethylene glycol, or poly (ethylene glycol) (PEG 400)) in these experiments. The pulse waveform was optimized to electrochemically grow TiO2 nanotubes and chemically etch their walls during its cathodic current flow regime. The resultant TiO2 nanotube arrays showed a higher quality of nanotube array morphology and photoresponse than samples grown via the conventional continuous anodization method. Films grown with a 20 V/-4 V pulse sequence and pulse duration of 2 s at its negative voltage limit afforded a superior photoresponse compared to other pulse durations. Specifically, the negative voltage limit of the pulse (-4 V) and its duration promote the adsorption of NH4+ species that in turn inhibits chemical attack of the growing oxide nanoarchitecture by the electrolyte F- species. The longer the period of the pulse at the negative voltage limit, the thicker the nanotube walls and the shorter the nanotube length. At variance, with 0 V as the low voltage limit, the longer the pulse duration, the thinner the oxide nanotube wall, suggesting that chemical attack by fluoride ions is not counterbalanced by NH3/NH4+ species adsorption, unlike the interfacial situation prevailing at -4 V. Finally, the results from this study provide useful evidence in support of existing mechanistic models for anodic growth and self-assembly of oxide nanotube arrays on the parent metal surface.     

Size-dependent carbon monoxide adsorption on neutral gold clusters

We report on experiments probing the reactivity of neutral Au(n) clusters, n = 9-68, with carbon monoxide. The gold clusters are produced in a pulsed laser vaporization cluster source, operated at room temperature (RT) or at liquid-nitrogen temperature (LNT), pass through a low-pressure reaction cell containing CO gas, and are subsequently laser ionized. The reaction probabilities are determined by recording mass abundance spectra with time-of-flight mass spectrometry. The main observations are a strong temperature dependence and a remarkable size dependence. Upon cooling of the cluster source to LNT, the reactivity increases substantially. At LNT, the reaction probabilities for Au(n) with the first CO molecule are about a factor 10 higher than at RT. Moreover, adsorption of two, three, and even four CO molecules is observed, in contrast to RT clusters which at most adsorb one CO molecule. This temperature dependence is related to the lifetime of the cluster-molecule complexes, being much longer for cold clusters. The observed striking size dependence is similar at both temperatures and is discussed in terms of the electronic structure effects.     

Lipid Nanotube Tailored Fabrication of Uniquely Shaped Polydopamine Nanofibers as Photothermal Converters

Helically coiled and linear polydopamine (PDA) nanofibers were selectively fabricated with two different types of lipid nanotubes (LNTs) that acted as templates. The obtained coiled PDA‐LNT hybrid showed morphological advantages such as higher light absorbance and photothermal conversion effect compared to a linear counterpart. Laser irradiation of the coiled PDA‐LNT hybrid induced a morphological change and subsequent release of the encapsulated guest molecule. In cellular experiments, the coiled PDA‐LNT efficiently eliminated HeLa cells because of its strong affinity with the tumor cells. This work illustrates the first approach to construct characteristic morphologies of PDA nanofibers using LNTs as simple templates, and the coiled PDA‐LNT hybrid exhibits attractive photothermal features derived from its unique coiled shape.     

Tetragonal paramagnetic complex in Gd3+ doped Nd2(SO4)3·(NH4)2SO4·8H2O au]V.M. Malhotra

EPR studies of Gd³⁺ doped in single crystals of Nd₂(SO₄)₃·(NH₄)₂SO₄·8H₂O (hereafter referred to as NASO) at room (RT) and liquid nitrogen (LNT) temperatures exhibit that (1) the metal aquo complex has a tetragonal symmetry with abnormally low magnitudes of crystalline field parameters at RT and (2) NASO undergoes a possible phase transition between RT and LNT.     

Supramolecular self-assembly of nanotubes and supercoils from long-chain derivatives of pyrimindinetrione and triazine

The self-assembly of two complementary components, 5-(4-N-methyl-N-dodecylaminobenzylidene)-2,4,6-(1H,3H)-pyrimidi-netrione (1) and 4-amino-2,6-didodecylamino-1,3,5-triazine (2) was found to result in the formation of a hollow supramolecular nanotube with about 6 nm in diameter and hundreds of nanometers in length as observed directly by transmission electron microscope (TEM). X-ray diffraction patterns indicate that a periodical layered structure with a d spacing of 0.49 nm in the nanotube exists. If staining treatment were employed in TEM observations, the self-assembly was found to show a supercoil structure about 300 nm in diameter.     

DFT Study of Physisorption Effect of the Curcumin on CNT(8,0-6) Nanotube for Biological Applications

In the given work the adsorption properties of molecule curcumin((1 E,6 E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) on CNT(8,0-6) nanotube were investigated by the density functional theory(DFT) in the solvent water for the first time. The non-bonded interaction effects of compounds curcumin and CNT(8,0-6) nanotube on the electronic properties, UV/Vis spectra, chemical shift tensors and natural charges were determined and discussed. The electronic spectra of the compound curcumin and the complex CNT(8,0-6)/curcumin in the solvent water were calculated by time dependent density functional theory(TD-DFT) for investigation of the maximum wavelength value of molecule Curcumin before and after the non-bonded interaction with the CNT(8,0-6) nanotube and molecular orbitals involved in the formation of absorption spectrum of the complex CNT(8,0-6)/curcumin at maximum wavelength.     

Local environment and property of water inside the hollow cylinder of a lipid nanotube

We investigated the local environment of water confined inside the hollow cylinder of lipid nanotubes (LNTs) by time-resolved fluorescent measurements and attenuated-total-reflectance infrared (ATR-IR) spectroscopy. The LNT was obtained by self-assembly of cardanyl glucosides in water at room temperature and had an open-ended cylindrical nanospace with a diameter of 10-15 nm, a length of 10-100 microm, and hydrophilic inner and outer surfaces. We introduced a fluorescent probe of 8-anilinonaphthalene-1-sulfonate into the confined water and observed an extremely slow dynamic Stokes shift with a correlation time of 1.26 ns, which was 2-3 orders of magnitude longer than that of bulk-phase water. From the peak shift of the fluorescent spectrum, the local solvent polarity (ET(30)) of the confined water was estimated as 50 kcal/mol, which is 20% lower than that in bulk water. ATR-IR measurements showed that the hydrogen-bond network of water inside the LNT was more developed than that in bulk water at room temperature, which is in contrast to the water in other self-assembled confined geometries, such as Aerosol-OT (AOT) reversed micelles.     

The IR reflectance spectra of the nu 3(SO4(2-)) and nu 4(SO4(2-)) band regions of some Tutton salts using polarized radiation: testing the model dielectric function

The investigation of the vibrational bands of the SO(4)(2-) ions (in the nu(3) and nu(4) frequency regions) of six different Tutton salts was performed with specular IR reflectance spectroscopy using polarized radiation, on single crystal samples. The reflectance function under oblique incidence using dielectric model function as parameter (originally derived for optically uniaxial crystals) appeared to be readily applicable for the investigated monoclinic crystals. The frequencies of the transversal and longitudinal phonons were obtained by fitting of spectra recorded from (0 1 0), (0 0 1) and (1 0 0) crystal planes. Further, the symmetry types of all experimentally detected phonons were identified. Some of the results were further confirmed from IR absorption spectra recorded at liquid nitrogen temperature (LNT) of isomorphously isolated SO(4)(2-) ions into the corresponding selenate matrices.     

TiO2 nanotube/ZnO nanorod/CdS on Ti mesh with three-dimensional array structure for photocatalytic degradation under visible light irradiation

Research on Chemical Intermediates - The three-dimensional (3D) TiO2 nanotube arrays (TNTA) were prepared by electrochemical anodization of Ti mesh in a mixed electrolyte solution of (NH4)2SO4 and...     

Investigation of structures and properties of cyclic peptide nanotubes by experiment and molecular dynamics

In order to investigate the structures and properties of cyclic peptide nanotubes of cyclo[(-D: -Phe-L: -Ala)( n = 3,4,5,6)-], cyclo[(-D: -Phe-L: -Ala)( n = 4)-] was synthesized and self-assembled to nanotubes, and its structure and morphology of the nanotube were characterized by mass spectrometry (MS), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). On the basis of these experimental results, the structures of cyclo[(-D: -Phe-L: -Ala)( n = 3,4,5,6)-] were characterized by molecular dynamics. In addition, the motion behaviors of H(2)O molecules in nanotubes were investigated by molecular dynamics using a COMPASS force field. Experimental results show that cyclo[(-D: -Phe-L: -Ala)( n = 4)-] peptides self-assemble into nanotube bundles. Molecular modeling results indicate that cyclic peptide nanotubes with n = 3, 4, 5 and 6 are very stable; these nanotubes have internal diameters of 5.9 A, 8.1 A, 10.8 A and 13.1 A and outer diameters of 18.2 A, 21.7 A, 23.4 A and 25.9 A respectively. Modeling results demonstrate that H(2)O molecules move in cooperation in single nanotube and they diffuse in one dimension, but they did not diffuse unilaterally due to the antiparallel ring stacking arrangement.     

Morphologies of branched-chain pyrogallol[4]arenes in the solid state

A suite of branched-chain pyrogallol[4]arene (Pg) macrocycles, most of which show activity in bilayer membranes, has been prepared and studied by X-ray crystallography. The little-known branched side-chain Pgs include 2-propyl, 2-butyl, 2-pentyl, 3-pentyl, 3-heptyl, 4-heptyl, 5-nonyl and cyclohexyl. The Pgs form self-assembled structures having bilayer, capsule or, in one case, a nanotube morphology. The nanotube structure observed for C-(di-n-ethyl)pyrogallol[4]arene was confirmed by X-ray structure analysis and by transmission and scanning electron microscopies.     

GeO2/ZnWO4@CNT nanocomposite as a novel anode material for lithium-ion battery

Journal of Solid State Electrochemistry - Single-walled carbon nanotube (SWCNT) wrapped GeO2/ZnWO4 nanocomposite was prepared by single-step solvothermal method. In this work, GeO2/ZnWO4...     

Polymer‐Infiltrated Aligned Carbon Nanotube Fibers by in situ Polymerization

Carbon nanotube–polymer composite fibers are obtained by infiltration of a monomer liquid into aligned carbon nanotube aerogel fibers with subsequent in situ polymerization. The monomer, methyl methacrylate (MMA), was infiltrated into the aerogel fibers of multi‐walled carbon nanotubes (MWNTs) at room temperature and subsequently polymerized at 50 °C into poly(methyl methacrylate) (PMMA). Cross‐sections of the PMMA/MWNT composite fibers showed that the PMMA filled the spaces of the nanotube fibers and bound the nanotubes together. PMMA in the composite fibers exhibited local order. The resultant composite fibers with 15 wt.‐% nanotube loading exhibited a 16‐fold and a 49‐fold increase in tensile strength and Young's modulus, respectively, compared to the control PMMA.

     

n-Pentane and isopentane in one-dimensional channels

Molecular dynamics studies of n-pentane and isopentane in one-dimensional channels of AlPO(4)-5 and a carbon nanotube are reported. Variation of the structure and energetics in AlPO(4)-5 along the channel axis of isopentane is similar to what has been found for other rigid molecular systems. In n-pentane, these properties exhibit more frequent undulations along the channel due to flexibility. The end-to-end distance of n-pentane is a function of its position along the channel in AlPO(4)-5, suggesting that n-pentane has to alternately stretch in the narrow part and destretch or coil in the broader part of the channel. n-Pentane lies flat instead of upright on the inner surface of the carbon nanotube. Both of the species exhibit diffusive motion in AlPO(4)-5, and the self-diffusivity is higher than that in bulk. Isopentane has a higher diffusivity than does n-pentane. This is attributed to the higher cross section of isopentane, which is closer to the void cross section. Further, the coupling of the translational motion with the slower dihedral angle reorientation in the case of n-pentane decreases its mobility. Superdiffusive motion is seen for both species in the carbon nanotube. These results can be understood in terms of the levitation effect.     

Synthesis of N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates from O-isobutyl xanthate and amines using a nano-platinum multi-walled carbon nanotube catalyst

Abstract  

Twelve N-(3- and 4-substituted phenyl)-O-isobutyl thionocarbamates, eight of which are novel, were synthesized from O-isobutyl xanthate and 3- and 4-substituted anilines in the presence of a nano-platinum aminophenyl modified multi-walled carbon nanotube catalyst. The nano-Pt catalyst was prepared on a carbon nanotube support modified by diazotization, nitro group reduction, and subsequent microwave-assisted nano-Pt precipitation. The catalyst was characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, thermogravimetric analysis, and transmission electron microscopy. The nano-platinum/modified carbon nanotube catalyst was compared with a commercial Pt/active carbon catalyst in terms of product purity and yield. The results obtained by the use of the catalysts were additionally compared with those obtained by reaction of sodium isobutyl xanthogenacetate and 3- and 4-substituted anilines. Full structure characterization of the synthesized N-(substituted phenyl)-O-isobutyl thionocarbamates was achieved using FT-IR, ¹H and ¹³C NMR, and mass spectrometric methods, and their purity was proved by elemental analysis and gas chromatography. The new catalytic method offers advantages over the commercial method, such as higher yields and no product purification is required, thus conforming to the principles of ecologically friendly syntheses.     

Amino acid functionalization of double-wall carbon nanotubes studied by Raman spectroscopy

Double-wall carbon nanotubes (DWNT) have been functionalized with lysine after a strong oxidation with MnO4- in acid solution which, as suggested by the Raman spectra, attacked the external nanotube of the DWNT.     

一种新的WO3纳米管的制备方法

一维纳米材料因可用来构造高性能纳米器件的结构单元而成为纳米材料研究的热点．目前的研究重点集中在材料的制备和结构性能表征方面,已发展了多种制备方法,主要有模板法、V-L-S法、L-L-S法和V-S法等,其中阳极氧化铝(AAO)模板法是制备一维材料的好方法．AAO模板的制备工艺已相当成熟,