Size, dimensionality, and shape play important roles in determining the properties of nanomaterials. So far, most of the nanomaterial researches have been focused on zero-dimensional nanoparticles/nanodots and onedimensional nanowires/nanorods/nanotubes, but very few studies have been carried out on two-dimensional nanosheets. Starting from carbon, recently we have succeeded in growing a class of nanostructured two-dimensional materials either in the pure forms or in the form of composites with carbon. In this paper, we will first briefly discuss various types of two-dimensional systems and then focus on the formation mechanism of carbon nanowalls and their field-emission and electron transport properties. The use of carbon nanowalls as templates for the formation of other types of nanomaterials will also be discussed.

Magnetization properties of magnetic nanowire arrays are studied on various ferromagnetic materials grown in anodic alumina ͑alumite͒ and track etched polycarbonate ͑PCTE͒ membranes by pulsed electrodeposition. Magnetization curves were measured as functions of wire material, field orientation, and wire length. The coercivity (H c ) and remanent squareness ͑S͒ of the various wire arrays were derived from hysteresis loops as a function of angle ͑͒ between the field and wire axis. For PCTE membranes, H c () curves for CoNiFe, NiFe, and Co nanowire arrays all show an otherwise-bell-type variation, while they change shapes from the otherwise bell to bell type for Ni nanowire arrays as the wire diameter decreases to 30 nm. These characteristics can be understood based on different magnetization reversal mechanisms of small wires. The effect of magnetostatic interaction among wires on the magnetic properties was examined by changing the wire lengths in alumite membranes. It is found that the interaction reduces H c and S values significantly and may cause the overall easy axis change from parallel to perpendicular to the wire axis. However, the interaction is much weaker than expected from an independent precession theory. The strong coupling among the wire may also induce a change of magnetization reversal mechanism.

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Magnetic nanoparticles (Ni, CoNiFe) with diameters ranging from 30 to 200 nm were synthesized by electrodeposition using carbon nanowalls as templates. A series of experiments have been carried out to study the formation mechanism of nanoparticles. It was found that the formation of nanoparticles instead of continuous films was attributed to two key factors, i.e., the uneven current density distribution on the nanowall surfaces and the pulsed current supply with alternate polarities. The as-grown nanocomposite structures were characterized using energydispersive X-ray analysis, scanning electron microscopy, and magnetic measurement using a vibrating sample magnetometer. These types of nanostructures may have potential applications in batteries, supercapacitors, catalysts, and biomedical devices.

Well‐aligned carbon nanowalls with a thickness of a few nanometers and a lateral size in the micrometer range have been grown on various types of substrates. The nanowalls exhibit a remarkably different surface morphology as compared to fullerenes and carbon nanotubes, in particular their two‐dimensionality and high surface area. In this work, we focused on the second aspect and developed a templating method to fabricate a class of nanostructured materials based on the novel surface morphology of the carbon nanowalls. These structures may have potential applications in batteries, gas sensors, catalysts, and light‐emission/detection, field‐emission, and biomedical devices.