is higher than that observed for Co 3 O 4 with an average particle size of 20 nm (25 K). [11] This is in accordance with the smaller average particle size, which corresponds to a higher fraction of surface spins, and hence for which bulk behavior is expected to occur at higher temperatures. Relationships between block temperature and particle size have also been studied for Mn 3 O 4 and c-Fe 2 O 3 , and the peak temperature was also found to increase with decreasing particle size.[12]In conclusion, mesostructured Co 3 O 4 with Ia3d symmetry has been nanocast from cubic Ia3d mesoporous vinylsilica. The vinyl groups play an important role in entrapping Co(NO 3 ) 2 inside the pores. This process seems to be extendable to other metal oxides. The cobalt oxide synthesized has interesting magnetic properties, and may be the basis of magnetic nanocomposites, if the pore system can be filled with another ferromagnetic material. It will be very interesting to see what kind of magnetic properties result from the interaction of two different, ordered, ferromagnetic structures on a nanometer size scale.Experimental 0.5 g of vinyl-functionalized silica (synthesized using 20 % vinyltriethoxysilane and aged at 100 C [4], hereafter called vinylsilica) was soaked in 5 mL of 0.8 M Co(NO 3 ) 2 ethanolic solution, dried at 200 C, re-impregnated, and then calcinated at 450 C for 6 h. The amount of cobalt oxide in the composite was then typically 50± 55 wt.-%. The silica was then dissolved in a 2 M NaOH aqueous solution, with the NaOH solution being replaced 3 times. The samples were characterized using standard techniques, such as XRD, N 2 sorption analysis, and TEM. The magnetic properties were measured using a superconducting quantum interference device (SQUID). Orientation-Controlled Growth of Single-Crystal Silicon-Nanowire Arrays** By Shuaiping Ge, Kaili Jiang,* Xiaoxiang Lu, Yaofeng Chen, Rongming Wang, and Shoushan Fan* Development in the integrated-circuit (IC) industry is directed towards creating smaller and faster components that consume less power.[1] Owing to their unique structures and properties, one-dimensional nanoscale objects have shown many promising potential applications in future nanoscale electronics [2±4] and photonics applications. [2,5,6] Since the IC industry is currently dominated by silicon-based devices, silicon nanowires (SiNWs) will have the advantage of technical compatibility, compared with other semiconducting nanowires. Recently, many efforts have been directed towards the growth of SiNWs. [7,8] However, most of these methods give
