Joung et al. Nanoscale Research Letters 2012, 7:93 http://www.nanoscalereslett.com/content/7/1/93 moieties while preserving the P-Si bond. Introducing bulky side chains in our study improved the stability while facilitating InP formation with strong confinement at a readily low temperature regime (210°C to approxi- mately 300°C) by controlling nucleation in the reaction. We therefore were able to obtain a facile synthetic route, achieving highly uniform large-sized InP NQDs. Further growing a shell of a large bandgap material, ZnS, around each core particle using a single-source precursor resulted in highly luminescent NQDs in the entire visible range (560 nm to 640 nm) where their quantum yield [QY] range from 18% to 28%. Experimental details All reagents were purchased from Sigma-Aldrich Cor- poration (St. Louis, MO, USA) and used without further purification. Reactions were performed in an inert atmosphere. Materials All manipulations were carried out under a dinitrogen atmosphere using standard Schlenk and glovebox techni- ques. Indium(III) acetate [In(OAc)3] (99.99%), myristic acid [MA] (95%), oleic acid [OLA], ODE (90%), and zinc diethyldithiocarbamate [ZDC] were purchased from Sigma-Aldrich and used without further purification. Toluene, hexane, diethylether, and tetrahydrofuran [THF] were dried with sodium/benzophenone ketyl, and methy- lene chloride was distilled from CaH2. All solvents were stored over activated 3-Å molecular sieves [10-12]. All deuterium solvents were dried over activated molecular sieves (3 Å) and were used after vacuum transfer to a Schlenk tube equipped with a J. Young valve [10-12]. P (SiMe3)3 (1) was synthesized using the procedure in the literature [13]. The slightly modified literature method was analogously employed in preparing P(SiMe2-tert-Bu)3 (2). Synthesis of tris(tert-butyldimethylsilyl)phosphine (P(SiMe2-tert-Bu)3) (2) A solid mixture of sodium (0.32 g, 14 mmol) and potas- sium (0.41 g, 10.5 mmol) in a two-necked Schlenk flask connected by a reflux condenser was suspended and stir- red at 120°C without any solvents for several hours. Sodium and potassium were completely melted, and a mercury-like gray alloy was formed. At an ambient tem- perature, 50 ml of dimethoxyethane and red phosphorus (0.22 g, 7.0 mmol) were added to a flask containing the sodium/potassium alloy. The reaction mixture was slowly allowed to warm to 50°C and stirred vigorously for 24 h. To the resulting solution, tert-butyldimethylchlorosilane (3.48 g, 23.1 mmol) in 20 ml of dimethoxyethane was added via cannula and heated at reflux for another 24 h. The reaction mixture was allowed to cool to room Page 2 of 8 temperature, and then, the volatiles were evaporated under vacuum, leaving a yellow oil to which 15 ml of THF was added. The colorless solution was filtered, and the sol- vents evaporated to dryness to afford 2 as a white solid (0.8 g, 30.8%). The boiling point of 2 was observed at 108°C to 110°C under the pressure of 10-3 Torr. A solution 1H nuclear magnetic resonance [NMR] spectrum (400.13 MHz) at C6D6 solvent gave only two peaks at 0.34 and 1.04 ppm, which were assigned to SiMe2 and CMe3, respectively. Because of the coupling with phosphorus and protons, all peaks were split as doublets with the coupling constants of 3.6 Hz and 0.4 Hz, respectively. 13C{1H} NMR spectrum (100.61 MHz) at the same deuterium solvent gave three peaks at 1.7, 20.3, and 27.8 ppm, which were associated with SiMe2, CMe3, and CMe3, respectively. Like 1H NMR spectrum, all peaks are split as doublets with the coupling constants of 5.03, 17.02, and 3.00 ppm. 31P{1H} NMR (161.98 MHz) spectrum gave only one peak at 30.05 ppm. Electron impact mass spectrometry [EI-MS] showed the molecular peak of compound 2 at m/z = 376, and the ele- mental analysis of 2 contained 57.25 wt.% C and 12.16 wt. % H, corresponding to a molecular formula of C18H45PSi3. Synthesis of tris(dimethylphenylsilyl)phosphine (P (SiMe2Ph)3) (3) The desired product 3 was prepared from sodium (0.32 g, 14 mmol), potassium (0.41 g, 10.5 mmol), red phosphorus (0.217 g, 7 mmol), and dimethylphenylchlorosilane (3.94 g, 23 mmol) in a yield of 67.1% (2.05 g) in a manner analo- gous to the procedure for 2. In the 1H NMR (400.13 MHz) spectrum of 3 at C6D6 solvent, peaks at 0.30 and 7.57 to 7.15 ppm were observed. Like compound 2, the peak at 0.30 ppm originated from SiMe2 was split as doublets with the coupling constant of 6.0 Hz. As expected, one aliphatic carbon at 1.93 ppm and four aromatic carbons peaks at 128.31, 130.50, 133.37, and 136.38 ppm were observed in the 13C{1H} NMR (100.61 MHz) spectrum. 31P{1H} NMR (161.98 MHz) spectrum gave only one peak at 24.38 ppm. EI-MS showed the molecular peak of compound 3 at m/z = 437, and the ele- mental analysis of 3 contained 65.82 wt.% C and 7.55 wt.% H, corresponding to a molecular formula of C24H33PSi3. Synthesis of indium phosphide NQDs For a typical experiment of InP NQDs(’standard reaction’; Figure 1), 0.04 mmol of In(OAc)3 was added to a mixture of 0.12 mmol MA and 4 ml ODE in a 50-ml three-necked flask. The solution was then heated to 110°C for 1.5 h in vacuum. Injection solution was prepared by dissolving 0.02 mmol of P(SiMe3)3, P(SiMe2-tert-Bu)3, or P(SiMe2Ph) 3 in 1 ml of ODE while the mixture was still degassed from the reaction vessel. Then, the solution was injected