Organometallic Zinc Cages Open New Possibilities for Semiconductors
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RESEARCH/RESEARCHERS
Organometallic Zinc Cages Open New Possibilities for Semiconductors Spurred by the increasing use of nitride semiconductors such as GaN, AlN, and InGaN in optoelectronic, high-frequency, and highpower devices, there has been a lot of recent interest in finding single-source precursors to make these materials. Group 13 hydrazides are particularly attractive candidates for cleanly fabricating these important materials. However, not much is known about main-group hydrazides. In the February issue of Chemical Communications (DOI: 10.1039/ b516431a; p. 523), C. Redshaw from the University of East Anglia (Norwich, U.K.) and M.R.J. Elsegood from Loughborough University (Loughborough, U.K.) reported the preparation of novel tetrametallic zinc cages, which are good starting materials for the synthesis of other interesting architectures. By reacting 1,1′-dimethylhydrazine with diethylzinc, the researchers were able to obtain a Zn4N8 cage complex with two six-membered rings linked together by four five-membered rings. The lack of hydrogen bonding in these networks is expected to lead to improved conductivity for these materials. On reaction with tert-butyllithium, the cage-like structure of this novel hydrazide complex is disrupted, yielding a chain of Zn4N7 clusters bridged together by lithium. The structure of the lithiated compound was determined using high-intensity x-rays generated by the synchrotron at Daresbury Laboratory. The researchers said that the Zn4N8 organometallic “cube” can potentially be used to prepare many other interesting structural motifs that have not been seen before. These hydrazide complexes are expected to be useful precursors for the improved fabrication of semiconductors. SARBAJIT BANERJEE
Flexible Carbon Nanotube–Polymer Composites Display Excellent Electromechanical Properties Carbon nanotubes are known to exhibit exceptional electrical and mechanical properties. To tap these qualities for useful applications, nanotube structures need to be organized into stable device architectures. In the March 8 issue of Nano Letters (DOI: 10.1021/nl052238x; p. 413), Y.J. Jung of Northeastern University, S. Kar of Rensselaer Polytechnic Institute, A. Avadhanula of New Mexico State University, and their colleagues have presented a method to obtain aligned and patterned multiwalled carbon nanotubes (MWNTs) embedded in a soft poly (dimethylsiloxane) (PDMS) matrix. The resulting composite is an extremely flexible thin film with valuable electromechanical properties. An array of cylindrical pillars (diameter, ~500 μm; height, ~100 μm) comprising vertically aligned MWNTs was grown on prepatterned SiO2/Si substrates using thermal chemical vapor deposition (CVD) of ferrocene and xylene at 800°C. After pouring a prepolymer solution of PDMS on the substrate and curing at 100°C for 1 h, self-standing nanotube–PDMS composite thin films were peeled off from the substrate. By varying the CVD growth conditions and changing the quantity of PDMS backbone, the shape and size of these composites can be e
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