Two hydrothermally synthesised allophanes (Si/Al = 0.5 and 1) were modified by heating at 400 degrees C. N-methyl-D-glucamine, a specific boron complexant, was grafted on the allophane material with Si/Al = 0.5. The surface and structural properties of the different materials were characterised by infrared spectroscopy and Si-29 CP MAS NMR spectroscopy. The porous characteristics of the different allophanes (specific surface area, pore size distribution) were determined by nitrogen adsorption at 77 K using the BET equation and the BJH model. The adsorption of boron, i.e. boric acid/borate, by the modified allophanes was studied in aqueous solutions with boron contents of 1 to 100 mg L-1. The pH-dependence of boron adsorption of all the sorbents showed a maximum at a pH value close to the pKa value of boric acid (pKa H3BO3/B (OH)(4)(-) = 9.26). The adsorption isotherms of boron by raw and modified allophanes were fitted with a double Langmuir equation, assuming the presence of two sets of adsorption sites. The grafting of N-methyl-D-glucamine did not improve the boron adsorption of the allophanes but the structural changes by heating at 400 degrees C increased the adsorption. (C) 2011 Elsevier B.V. All rights reserved.

We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single-and multiwalled carbon nanotubes with diameters in the range from 0.7 to 100 nm and with number of walls from 1 to 90. We provide models on how diameter and the number of nanotube walls influence NMR linewidth and line position. Both models are supported by theoretical calculations. Increasing the diameter D, from the smallest investigated nanotube, which in our study corresponds to the inner nanotube of a double-walled tube to the largest studied diameter, corresponding to large multiwalled nanotubes, leads to a 23.5 ppm diamagnetic shift of the isotropic NMR line position d. We show that the isotropic line follows the relation d = 18.3/D + 102.5 ppm, where D is the diameter of the tube and NMR line position d is relative to tetramethylsilane. The relation asymptotically tends to approach the line position expected in graphene. A characteristic broadening of the line shape is observed with the increasing number of walls. This feature can be rationalized by an isotropic shift distribution originating from different diamagnetic shielding of the encapsulated nanotubes together with a heterogeneity of the samples. Based on our results, NMR is shown to be a nondestructive spectroscopic method that can be used as a complementary method to, for example, transmission electron microscopy to obtain structural information for carbon nanotubes, especially bulk samples.

A novel modeling procedure for semi-symmetrical plant organs using longitudinal and transverse organ profiles was developed to simplify and improve virtual organ representation. Fruits were used as model organs. The fruits were divided into halves to capture the fruit profile. Using a regular photo camera (Nikon-Coolpix 4500), and an in-house image acquisition setup, the half fruit images were captured. In-house Matlab (The Mathworks, Natick, MA) based program was used to determine the boundaries of the digitized images. Based on the boundary points, and using Fourier series approximation, the image boundaries were defined mathematically. Fourier series approximation defines boundary shapes using the sum of sine and cosine terms. Based on the Fourier descriptors, which are coefficients of the Fourier series approximation, fruit contours were extracted. Surface construction algorithms based on smoothed contour boundaries were developed. Because of non-axis symmetricity of most fruits, and the presence of surface perturbations, for example, carpels in tomato fruits, models based on only longitudinal cross sections were not satisfactory. A complete fruit model was finally developed by combining the longitudinal cross section of half fruits and the transverse cross section of whole fruits. To our knowledge, this is the first realistic geometrical fruit model that captures the fruit shape complexities. Such a model may be useful to analyze the genetic and environmental controls of fruit morphological and biochemical properties. Our modeling approach has limitation in producing geometric models for unusual curved shape plant organs such as banana, cucumbers, cassava and Jerusalem artichoke that are not quasi-symmetrical along the longitudinal axis. (C) 2010 Elsevier B.V. All rights reserved.

We present 13 C high-resolution magic-angle-turning (MAT) and magic angle spinning nuclear magnetic resonance data of Cs and Rb intercalated single walled carbon nanotubes. We find two distinct phases at different intercalation levels. A simple charge transfer is applicable at low intercalation level. The new phase at high intercalation level is accompanied by a hybridization of alkali (s) orbitals with the carbon (sp2) orbitals of the single walled nanotubes, which indicate bundle surface sites is the most probable alkali site. (C) 2011 American Institute of Physics. [doi:10.1063/1.3631052]

This paper presents a potential new way to detect radio-frequency signals originating from nuclear magnetic resonance in the presence of a high static magnetic field. Our work concerns the design and the characterization of a nano-antenna based on nanoelectromechanical systems. For this purpose, single carbon nanotube devices have been selected for their unique interplay between electrical and mechanical characteristics. Following, the careful determinations of the field emission properties and the resonance frequencies of the device, the detection of a radio-frequency signal from an external radio-frequency source is shown to be realistic. Work is in progress in order to validate the use of this type of nano-probe for the NMR investigations of reference and real samples.

Understanding and controlling the dynamical, electronic and magnetic properties of carbon-based materials is of fundamental relevance for employing these structures in future nano- and bioscience applications. In this talk, we report on the recent discoveries obtained in these new hybrid materials with a special focus on results obtained by solid state nuclear magnetic resonance spectroscopy. These studies provide a new insight into such structures and allow to model some of their exotic properties. Our contribution to the knowledge of 1D-confined molecules address more general topics on the confinement that profoundly changes the properties of matter and the opportunity to engineer nano-systems. Some potential applications of these new hybrid materials in nuclear magnetic resonance spectroscopy and imaging will be presented.

We have encapsulated adamantane (C10H16) in single- and multi-walled carbon nanotubes. Adamantane is a high symmetry cage like molecule with point group symmetry T-d and can be considered as a hydrogen-terminated diamond fragment. We confirmed and identified the successful filling by high resolution transmission electron microscopy, C-13 nuclear magnetic resonance, infrared and Raman spectroscopy. C-13 nuclear magnetic resonance of the adamantane filled nanotubes reveals that the adamantane molecules stop rotating after encapsulation. A blue-shift of the Raman active radial breathing modes of the carbon nanotubes supports this and suggests a significant interaction between encapsulated adamantane molecules and the single wall nanotubes. The encapsulated adamantane molecules exhibit red shifted infrared C-H vibration modes which we assign to a slight elongation of the C-H bonds. We observe both a nanotube diameter dependence of the adamantane filling ratio and a release rate of adamantane from the CNTs that depends on the CNT diameters. (C) 2010 Elsevier Ltd. All rights reserved.