Shock-wave Resistance of WS2 Nanotubes

Journal of the American Chemical Society. Feb, 2003  |  Pubmed ID: 12553835

The shock-wave resistance of WS(2) nanotubes has been studied and compared to that of carbon nanotubes. Detailed structural features of post-shock samples were investigated using HRTEM, XRD, and Raman spectroscopy. WS(2) nanotubes are capable of withstanding shear stress caused by shock waves of up to 21 GPa, although some nanotube tips and nanoparticles containing multiple structural defects in the bending regions are destroyed. Small WS(2) species, consisting of only a few layers, are extruded from the nanotubes. Well-crystallized tube bodies were found to exhibit significant stability under shock, indicating high tensile strength. XRD and Raman analyses have confirmed this structural stability. Under similar shock conditions, WS(2) tubes are more stable than carbon nanotubes, the latter being transformed into a diamond phase. WS(2) nanotubes containing small concentrations of defects possess significantly higher mechanical strength, and, as a consequence, hollow WS(2) nanoparticles are expected to act as excellent lubricants under much higher loading than was previously thought.

Large-scale Production of NbS(2) Nanowires and Their Performance in Electronic Field Emission

Angewandte Chemie (International Ed. in English). Oct, 2004  |  Pubmed ID: 15495149

Polar Assembly in a Designed Protein Fiber

Angewandte Chemie (International Ed. in English). Dec, 2004  |  Pubmed ID: 15614890

Polyurea-functionalized Multiwalled Carbon Nanotubes: Synthesis, Morphology, and Raman Spectroscopy

The Journal of Physical Chemistry. B. Jun, 2005  |  Pubmed ID: 16852469

An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloride-functionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH2). In the presence of MWNT-NH2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,4'-methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flat- or flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs.

Enhancement of Polymer Luminescence by Excitation-energy Transfer from Multi-walled Carbon Nanotubes

Small (Weinheim an Der Bergstrasse, Germany). Nov, 2007  |  Pubmed ID: 17935066

Carbon nanotubes have been shown to efficiently quench luminescence from conjugated polymers when incorporated in a composite. However, shown here is an up to 100-fold increase in the visible photoluminescence signal from fluorescent chromophores in nylon 10,10 by incorporating multi-walled carbon nanotubes (MWCNTs). Using 325- and 488-nm excitation the optical absorption by MWCNTs embedded within the polymer matrix is demonstrated, followed by efficient excitation-energy transfer to emissive chromophores intrinsic to the polymer but only when the MWCNTs are acid functionalized. Furthermore, the MWCNTs are shown to significantly retard photobleaching of fluorescent centers in the nylon composites. These remarkable properties greatly advance the prospects of utilizing MWCNTs in organic solar cells and electroluminecent devices to improve performance.

In Situ Nucleation of Carbon Nanotubes by the Injection of Carbon Atoms into Metal Particles

Nature Nanotechnology. May, 2007  |  Pubmed ID: 18654289

The synthesis of carbon nanotubes (CNTs) of desired chiralities and diameters is one of the most important challenges in nanotube science and achieving such selectivity may require a detailed understanding of their growth mechanism. We report the formation of CNTs in an entirely condensed phase process that allows us, for the first time, to monitor the nucleation of a nanotube on the spherical surface of a metal particle. When multiwalled CNTs containing metal particle cores are irradiated with an electron beam, carbon from graphitic shells surrounding the metal particles is ingested into the body of the particle and subsequently emerges as single-walled nanotubes (SWNTs) or multiwalled nanotubes (MWNTs) inside the host nanotubes. These observations, at atomic resolution in an electron microscope, show that there is direct bonding between the tubes and the metal surface from which the tubes sprout and can be readily explained by bulk diffusion of carbon through the body of catalytic particles, with no evidence of surface diffusion.

Order-disorder Antiferroelectric Phase Transition in a Hybrid Inorganic-organic Framework with the Perovskite Architecture

Journal of the American Chemical Society. Aug, 2008  |  Pubmed ID: 18636729

[(CH3)2NH2]Zn(HCOO)3, 1, adopts a structure that is analogous to that of a traditional perovskite, ABX3, with A = [(CH3)2NH2], B = Zn, and X = HCOO. The hydrogen atoms of the dimethyl ammonium cation, which hydrogen bond to oxygen atoms of the formate framework, are disordered at room temperature. X-ray powder diffraction, dielectric constant, and specific heat data show that 1 undergoes an order-disorder phase transition on cooling below 156 K. We present evidence that this is a classical paraelectric to antiferroelectric phase transition that is driven by ordering of the hydrogen atoms. This sort of electrical ordering associated with order-disorder phase transition is unprecedented in hybrid frameworks and opens up an exciting new direction in rational synthetic strategies to create extended hybrid networks for applications in ferroic-related fields.

Multiferroic Behavior Associated with an Order-disorder Hydrogen Bonding Transition in Metal-organic Frameworks (MOFs) with the Perovskite ABX3 Architecture

Journal of the American Chemical Society. Sep, 2009  |  Pubmed ID: 19725496

Multiferroic behavior in perovskite-related metal-organic frameworks of general formula [(CH(3))(2)NH(2)]M(HCOO)(3), where M = Mn, Fe, Co, and Ni, is reported. All four compounds exhibit paraelectric-antiferroelectric phase transition behavior in the temperature range 160-185 K (Mn: 185 K, Fe: 160 K; Co: 165 K; Ni: 180 K); this is associated with an order-disorder transition involving the hydrogen bonded dimethylammonium cations. On further cooling, the compounds become canted weak ferromagnets below 40 K. This research opens up a new class of multiferroics in which the electrical ordering is achieved by means of hydrogen bonding.

Science and Mexico Are the Losers in Institute Politics

Nature. Mar, 2010  |  Pubmed ID: 20220820

Working at the Coal Face

Nature. Oct, 2010  |  Pubmed ID: 20944613

Electric Control of Magnetization and Interplay Between Orbital Ordering and Ferroelectricity in a Multiferroic Metal-organic Framework

Angewandte Chemie (International Ed. in English). Jun, 2011  |  Pubmed ID: 21618371

Crossdisciplinary Fundamental Research--the Seed for Scientific Advance and Technological Innovation

Physical Chemistry Chemical Physics : PCCP. Dec, 2011  |  Pubmed ID: 22052113

As it was earlier in the 1980's, so it is now, fundamental science research is under threat as decisions are made on science funding by people who do not do fundamental research, seem congenitally incapable of understanding what it is and furthermore in the face of countless examples seem blind to how important it has been to the technologies that govern our modern life and will be to the future technologies that we desperately need to develop to survive. In this article some general observations are made on how the fascination for what happens in space and stars was the key trigger that gave birth to Science itself and a particular case is outlined which indicates that this same fascination is still the catalyst of some fundamental breakthroughs today. This article also outlines an archetypal example of the way major breakthroughs are often made by the synergy that comes from cross-disciplinary research in a way which is totally surprising. In this case it started from a curiosity about the quantum mechanical description of molecular dynamics and involved pioneering advances in synthetic organic chemistry which led to the suprising discovery that some exotic carbon molecules were abundant in space and stars. These results initiated an experiment using a new technology that represented a major breakthrough in cluster science. The upshot was totally unpredictable, the birth of a whole new field of Chemistry as well as a paradigm shift in major areas of Nanoscience and Nanotechnology.

For Young Architects of the Nanoscale World

Advanced Materials (Deerfield Beach, Fla.). Jan, 2012  |  Pubmed ID: 22223152