Joung et al. Nanoscale Research Letters 2012, 7:93 http://www.nanoscalereslett.com/content/7/1/93 Page 3 of 8 Figure 1 Absorption spectra of InP NQDs. (a) InP NQDs synthesized by varying the ratio of In and MA by 1:2.5, 1:3, and 1:3.5 using P(SiMe3)3; (b) InP NQDs synthesized at different reaction temperatures (In/MA = 1:3); (c) InP NQDs synthesized by varying the ratio of indium and MA by 1:3 and 1:3.5 using P(SiMe2-tert-Bu)3; and (d) InP NQD synthesized at different reaction temperatures (In/MA = 1:3). rapidly into the hot reaction solution at 270°C under N2. After injection, the solution was cooled. The products were precipitated and washed with methanol and 1-buta- nol and re-dispersed in hexane. Synthesis of InP/ZnS For in situ fabrication of InP/ZnS core-shell NQDs, the temperature of the growth solution of InP was lowered after a 10-min growth to 200°C. Thirty milligrams of ZDC, 1 ml of TOP, and 1 ml of OLA were added to 1 ml of ODE in nitrogen atmosphere. After injection, the solution was cooled to room temperature and the solu- tions were precipitated with an excess of methanol and 1-butanol and dried in air. Optical and structural characterizations The microstructure and crystallographic structures were investigated by field emission transmission electron microscopy (Tecnai F30 Super-Twin, FEI Co., Hillsboro, OR, USA; Yun-Chang Park, KAIST NanoFab). The absorption and photoluminescence were characterized with a UV-visible [Vis] spectrophotometer (SD-1000, Scinco Co., Ltd., Gangnam-gu, Seoul, South Korea) and a fluorometer (Fluorolog, Horiba Jobin Yvon Inc., Edison, NJ, USA). 1H, 13C{1H}, and 31P{1H} NMR spectra were recorded at ambient temperature on a Bruker DPX-400 NMR spectrometer (Bruker Optik GmbH, Ettlingen, Germany) using standard parameters. The chemical shifts are