The microwave spectrum,substitution structure and dipole moment of cyanobutadiyne,HCCCCCN

Cyanobutadiyne (cyanodiacetylene), HCCCCCN, is sufficiently stable at low pressures to permit its rotational spectrum to be studied by microwave spectroscopy. The spectrum consists of a series of R-branch transitions typical of a linear molecule. The transitions with J = 9 to 14 which lie between 26.5 and 40.0 GHz have been measured for the vibrational ground state. Transitions have also been detected in natural abundance for all possible singly substituted ¹³C and ¹⁵N isotopic species. Deuteriated cyanobutadiyne, DCCCCCN, has also been synthesized and its ground state spectrum recorded. These measurements have enabled a complete substitution structure to be derived for the first time for a polyacetylene: r₈(HC_a) = 1.0569 ± 0.001, r₈(C_aC_b) = 1.2087 ± 0.001, r₈(C_bC_c) = 1.3623 ± 0.003, r₈(C_cC_d) = 1.2223 ± 0.004, r₈(C_dC_e) = 1.3636 ± 0.003, $\text{r}{}_8\text{(}\text{C}{}_{\mathrm{e}}\text{}\text{N}\text{) = 1.1606 ± 0.001}\text{A}\text{?}\text{(10}{}^{\mathrm{?10}}\text{m}\text{)}$. The spectroscopic parameters for the ground state are B₀ = 1331.3313 ± 0.001 MHz and D₀ = 0.0257 ± 0.002 KHz. The dipole moment, determined from the Stark effects of the J = 9 and 10 lines, is 4.33 ± 0.03 Debye.     

Catalysed growth of novel aluminium oxide nanorods

Micron-scale coral-like aluminium oxide structures have been generated by heating a mixture of AlB₂ and Co powders in a quartz boat at ca. 1050 °C under N₂. Upon sonication in acetone, the structures break down into elongated single-crystal aluminium oxide nanorods ranging from 20 to 200 nm in diameter and up to 5 μm in length. Single Co particles are often found attached to nanorod tips. A vapour–liquid–solid (V–L–S) mechanism appears to be responsible for the aluminium oxide nanorod growth. Received: 21 January 2003 / Accepted: 22 January 2003 / Published online: 28 March 2003 RID="*" ID="*"Corresponding author. E-mail: d.walton@sussex.ac.uk     

Shock-wave resistance of WS2 nanotubes

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.     

Mössbauer Study of Iron-Containing Carbon Nanotubes

⁵⁷Fe transmission Mössbauer at temperatures between 18 and 298 K and magnetic measurements have been used to characterize Fe-filled carbon nanotubes which were prepared by pyrolisis of Ferrocene + C₆₀ at atmospheric pressure under an Ar atmosphere at 1050°C. The Mössbauer data have shown that the Fe phases encapsulated within the carbon nanotubes are -Fe, Fe₃C and -Fe. The magnetic results are compatible with the Mössbauer data. Taken together the results allow us to propose a simple picture of the distribution of iron phases within the carbon nanotubes which would consist of an -Fe core surrounded by an -Fe shell, finally covered by an Fe₃C layer.     

Efficient synthesis and tailoring of magnetic and dielectric properties of Pb‐free perovskite‐like ABX3 metal‐organic frameworks

Perovskite‐like metal‐organic frameworks (MOFs) are hybrid materials of high interest for their potential in information storage technology, as Pb‐free substitutes for the widely used lead zirconate titanate (PZT) family of multiferroics. We report here a new, microwave‐assisted method of synthesis for perovskite‐like MOFs, which exploits the advantages of rapid and volumetric heating by microwaves in order to achieve synthesis within minutes, compared to days required by previously reported methods. The preliminary results demonstrate a broad control over the size and morphology of the products, by minor changes in the reaction conditions. An investigation of the effects of size and morphology on the magnetic and dielectric properties is presented here.

     

A novel route to aligned nanotubes and nanofibres using laser-patterned catalytic substrates

We describe the generation of aligned carbon nanotube bundles and films by pyrolysis of solid organic precursors (for example 2-amino-4,6-dichloro-s-triazine, s-triaminotriazine) at 950-1050 °C over laser-patterned thin metal (Fe, Co, Ni) films, deposited on silica substrates. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies reveal that surface roughness of the laser-etched catalytic substrates plays a key role in achieving control of nanotube growth. We believe that, during the etching process, the energised (ablated) metal clusters condense and recrystallise evenly, possibly as the metal oxide, within the edges or surface of the eroded regions. During pyrolysis these catalytic particles, embedded in the silica substrates, are responsible for carbon agglomeration and subsequent tube axial growth, suggesting that nanotube alignment strongly depends upon the etching conditions (for example laser power, pulse duration, and focal distance). The pyrolysed products (usually nanotubes or nanofibres) were characterised by SEM, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDX). Samples containing only small amounts of amorphous carbon and other carbonaceous particles are notably absent. We observe that the degree of graphitisation is dependent upon the catalyst and the organic precursor. Interestingly, a nitrogen content З% was detected within the nanofibres, which exhibit corrugated graphite-like morphologies. This pyrolytic method may be used to advantage in generating aligned heteroatomic nanostructures such as B_xC_yN_z systems.     

The microwave spectrum,structure and dipole moment of thiocarbonyl fluoride,F2CS

The microwave spectrum of thiocarbonyl fluoride, F₂CS, has been investigated in the region 26.5–40.0 GHz. Transitions of the ¹⁹F₂¹²C₃₂S and ¹⁹F₂¹²C³⁴S isotopic species have been observed and the derived rotational constants yield the following ground stale structural parameters

The ground state rotational constants of the normal species are (in MHz)

The asymmetry parameter, x = ?0.62640, and the inertial defect Δ⁰ = 0.203 u A² which is consistent with that expected for this type of molecule, if planar.The dipole moment was determined from the Stark effect of two lines, and was found to be μ_A = 0.080 D.     

The microwave spectra of 1-cyanobut-3-ene-1-yne, CH2=CH---CC---CN and 1-cyanobut-1-ene-3-yne, HCC---CH=CH---CN

Two molecules related to cyanobutadiyne, H---CC---CC---CN, 1-cyanobut-3-ene-1-yne, CH₂=CH---CC---CN, and 1-cyanobut-1-ene-3-yne, H---CC---CH=CH---CN, have been synthesized and their microwave spectra assigned. The resulting rotational constants can be used to search for these species in the interstellar medium using radioastronomy. Interstellar information on such species will enable a better understanding of the chemistry responsible for the production of carbon chain molecules in the interstellar medium.