Description
We developed a new, highly general methodology for synthesis of magic-size nanomaterials using transitional metal salts of sterically bulky or moderate length aliphatic carboxylic acids, moderate reaction temperatures and prolonged reaction times. Using this methodology we were able to synthesize nanowires (NWs) of ZnSe and ZnTe with diameter of 1.0-1.7 nm. ZnTe NWs with diameters of ~1.7 nm are the thinnest NWs that have been reported for this material. The NWs have high aspect ratios (>200) and multiple sharp (~8 nm FWHM) band gap absorbance and photoluminescence maxima. Some of these narrow features have been attributed to nanoplatelets consisting of several atomic layers of ZnSe and ZnTe. The similar synthetic approach has produced CdS, ZnSe, and ZnTe magic-size nanocrystals, InSe and Zn3P2 1-D nanostructures. In particular, nanoscrolls, nanorolls, and nanoplatelets of indium selenide were synthesized using zinc acetate and trioctylphosphine selenide for the first time. The material has sharp absorption maxima at 340 nm and 370 nm with the corresponding band-gap photoluminescence. Transmission electron microscopy (TEM) images and spectroscopy data indicate that layered structures of hexagonal InSe are either half a unit cell or one unit cell thick. TEM of CdS shows monodisperse 1.45 nm nanocrystals. These CdSe nanocrystals have sharp absorption maxima around 325 nm with broad photoluminescence peak at 530 nm, which can be attributed to surface-trap emission. Compared to ZnTe nanoplatelets, zinc phosphide materials show unique paw-print patterns of nanoplatelets. For the first time it has been demonstrated that CdS, CdSe, and CdTe nanocrystals can be transferred in polar solvents such as acetonitrile through surface ligand exchange reaction with diethylene glycol bis (3-aminopropryl) ether. This opens up a possibility for performing mass spectrometry and electrochemistry studies on these nanocrystals. During phase transfer, CdTe nanocrystals undergo size-selective purification leading to the narrower absorbance maxima.
