Simple fabrication of single- and multi-layer polymer nanotubes by spin-casting method within anodized aluminum oxide (AAO) templates

Polymer nanotubes (PNTs) were fabricated by a simple spin casting of the polymer solution into nanochannels of anodic aluminum oxide (AAO) membranes. The thickness of the polymer nanotubes could be reproducibly controlled by changing the concentration of the polymer solutions. Furthermore, multiple spin casting of different polymer solutions could produce multi-layer PNTs (MPNTs), whose formation was confirmed by a selective staining technique in transmission electron microscope (TEM) experiments. Luminescent molecules such as blue-emitting Ir(III) complex and orange-emitting rhodamine B derivative could be uniformly incorporated into each polymer layer simply by mixing them into each polymer solution. These dye-incorporated MPNTs could be easily fabricated by the same spin casting method. Their optical properties were determined by UV-Vis spectroscopy, photoluminescence, and fluorescence microscopy. The morphology of the nanotubes was characterized using a field emission-scanning electron microscope (FE-SEM) and TEM. These results showed that the MPNTs could be reproducibly fabricated throughout the length of the nanochannels of the AAO templates.