Since the discovery of carbon nanotubes in 1991, [1] extensive research has been carried out on one-dimensional nanostructures because of their unique properties. [2][3][4][5][6] Various methods have been developed for the synthesis of nanotubes. [7] In general, it is relatively easy for layered materials to form nanotubes directly under the appropriate experimental conditions. [8] For materials that do not have a layered structure, nanotubes may be synthesized by a variety of methods, such as decomposition of the precursor, [9] templateassisted growth, [8,[10][11][12][13][14] self-assembly, [15,16] and vapor deposition. [17,18] However, these methods are still limited to the synthesis of specific kinds of nanotubes.
Lead chalcogenides (PbE, E = S, Se, Te) are important semiconductors with narrow band gaps that are showing great promise in the field of IR photoelectronic and thermoelectric devices. [19][20][21] Various nanostructures of lead chalcogenides, such as quantum dots, [22][23][24] nanorods, [25,26] nanowires, [27,28] and nanotubes, [14,15,29,30] have been reported over the past decade. However, to the our knowledge, little work has been reported on polycrystalline nanotubes of lead chalcogenides assembled from nanocrystals, although one key example is the formation of composite nanotubes consisting of PbS nanoparticles, sodium dodecyl sulfate, and poly(ethylene oxide). [15] Herein we report a novel biomolecule-assisted route to the synthesis of lead chalcogenide polycrystalline nanotubes by the self-assembly of nanocrystals at room temperature. Cysteine (HSCH 2 CH(NH 2 )COOH, including l-cysteine, lcysteine hydrochloride monohydrate, and dl-cysteine hydro-