화학공학소재연구정보센터
Langmuir, Vol.26, No.13, 10636-10644, 2010
Synthesis, Characterization, and Self-Organization of Dendrimer-Encapsulated HgTe Quantum Dots
Mercury telluride (HgTe) quantum clots (QDs) were synthesized in methanol at 5 degrees C using generation 5 (G5) and 7 (G7) polyamidoamine (PAMAM) dendrimers, which function both as nucleation sites and as nanoparticle stabilizers. Transmission electron microscopy (TEM) data indicate these particles were slightly oblate, with an average aspect ratio of 1.3 +/- 0.1 and a minor axis of 2.6 +/- 0.3 nm. The crystal phase was determined to be coloradoite (cubic system) by analysis of the electron diffraction pattern. Absorption maxima for HgTe QDs ranged from 950 to 970 nm, depending on the dendrimer generation and concentration. QD size distribution was optimized by careful variation of the Hg2+ : dendrimer surface group molar ratio for both G5 and G7 dendrimers. An increase in molar ratio from 1:0.5 to 1:4 resulted in a decrease in the half-width at half-maximum (HWHM) of the HgTe bandgap absorption from 68 +/- 3 to 52 +/- 2 nm, indicating a size distribution focusing of 23 +/- 4%. Second-derivative analysis of HgTe QD FTIR absorption spectra suggested that the quantum clots were fully encapsulated by a single G7 dendrimer, whereas multiple G5 dendrimers were necessary to stabilize a single nanoparticle. TEM and EH R data revealed that the HgTe QDs form two-dimensional necklace-type arrays through a self-organization process, which proceeds through interpenetration of dendritic arms. TEM data further indicated that the average nanonecklace contained 10-15 QDs with an average ititer-QD separation of 1.3 +/- 0.7 nm and a total chain length of 46 +/- 6 nm.