Highly emissive CdTe nanowires grown in a phosphate buffer solution

One-dimensional structures of metal and semiconductor materials (nanowires), have become a focus of interdisciplinary research in recent years both as a model system for studies of 1D quantum confinement effects and because of their potential applications in electronics and photonics. We report the assembly of CdTe nanocrystals into nanowires using an approach that attempts to capitalize on the self-assembling properties of naturally occurring processes. CdTe nanocrystals -building blocks for the nanowires -were synthesized in aqueous solution using thioglycolic acid as stabilizer. Post-preparative size-selective precipitation was applied to the crude solution of nanocrystals to remove the non-reacted species and separate the strongly emitting fractions of nanocrystals with narrow size distribution (photoluminescence quantum yield of 20-25%). We present details on the CdTe nanowires formation and properties, which were found to grow in a standard physiological phosphate-buffered solution, including micro-photoluminescence, fluorescence lifetime imaging (FLIM), in-situ observation of growth with a confocal microscope and high-resolution TEM analysis. The choice of proper nanocrystals concentration allowed reasonably slow growth rates and thus a controllable formation of nanowires. Once formed in solution, nanowires showed a significant degree of structural rigidity and resistance to externally applied mechanical stress. Structural integrity of nanowires and the high efficiency and stability of their luminescence properties make them attractive objects for future biological and/or biomedical experiments.