Shape-Controlled Solution-Synthesis of Single Crystalline ZnTe 1D Nanocrystals
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1035-L05-24
Shape-Controlled Solution-Synthesis of Single Crystalline ZnTe 1D Nanocrystals Jun Zhang1, Amar Kumbhar2, Kai Sun3, and Jiye Fang1 1 SUNY at Binghamton, Binghamton, NY, 13902-6000 2 Clemson University, Anderson, SC, 29625 3 University of Michigan, Ann Arbor, MI, 48109 ABSTRACT
Precursor-reduction method is employed to synthesize nanostructures of ZnTe. The shape of zinc blende ZnTe nanocrystals could be influenced by reaction temperature, concentration of the precursors as well as the use of stabilizing agent. By controlling the synthetic conditions, three types of nanoscaled ZnTe, quasi-spherical ZnTe nanocrystals, ZnTe nanobelts and ZnTe nanorods have been observed. Their crystalline structures are also discussed.
INTRODUCTION Compared with the size-control [1], maintenance of the particle shape is hard and there still have been plenty of targets to challenge [2-5]. ZnTe is an attractive semiconductor with a direct band gap of 2.1 - 2.26 eV [6,7] and a Bohr exciton radius of 6.2 nm [8]. Its broad range of potential applications in optoelectronic devices operating in the blue-green region of the spectrum and thermoelectric devices has attracted increasing attention recently [5,9,10]. In addition, the crystal structure of ZnTe is very similar to that of CdSe, a commonly studied semiconductor [2,11,12]. Compared with other semiconductor NCs, however, studies on the preparation of colloidal ZnTe NCs are still limited. Previous studies indicated that a direct reaction between metal zinc (or zinc salts) and tellurium could result in very little ZnTe leaving most reactant unreacted10. Yadong Li [13] etc. suggested that this might be due to the fact that tellurium was not easily to be reduced to anions. We therefore design a reaction approach in which the Te precursor reduction and NC growth could be “separated” by altering the reducing rate. The feature of this strategy is that the NC shape could be controlled through various parameters, such as reaction temperature, concentration of precursors, and use of crystallographic-plane-selective stabilizing agent. EXPERIMENT Chemicals: Metal tellurium (99.99%), zinc acetate dehydrate (98+%), trioctylphosphine (TOP, 90%), oleylamine (70%), oleic acid (90%), benzyl ether (99%), dioctyl ether (99%) and superhydride (LiBH(CH2CH3)3) solution in THF (1M) are Aldrich products and were used as received. tetradecylphophonic acid (TDPA, 98%) and phenyl ether (99%) were purchased from Alfa Aesar. Anhydrous ZnCl2 was dried in an oven at 130 oC for one week before use. Super-hydride solution in dioctyl ether (1M) was freshly prepared before use according to literature [14,15]. Synthesis of ZnTe Quasi-spheres: In a typical experiment, zinc acetate dihydrate (1 mmol), benzyl ether (15 mL), oleic acid (1 mL) were mixed and heated to 150 °C for 30 min under vacuum to
remove moisture. The temperature was then raised to 250 °C. A mixture of Te-TOP solution (1 mL) and 1 M superhydride solution in dioctal ether (1 mL) was then rapidly injected into this hot solution. The colloidal
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