Supporting Information Synthesis of InP Branched Nanostructures by Controlling the Intermediate Nanoclusters Yongju Kwon a , Gyuhyun Bang a , Jeongmin Kim a , Anastasia Agnes a and Sungjee Kim* a a Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, South Korea Experimental Chemicals. Indium acetate (In(Ac) 3 , 99.99%), indium chloride (InCl 3 , 98%), myristic acid (HMy) (≥ 99%), anhydrous toluene (99.5%), 1-octadecene (ODE, 90%), acetonitrile (99.8%) were purchased from Aldrich. Tris(trimethylsilyl)phosphine ((TMS) 3 P) (95%) was purchased from SK chemicals. All chemicals were used without further purification. Synthetic procedures General procedure for synthesis of 386-MSCs. 386-MSCs were synthesized using a reported method. 1 First, 0.8 mmol of In(Ac) 3 and 2.9 mmol of HMy in a three-necked round-bottom flask containing 20 mL ODE was degassed for 2 hours at 110 °C, then 0.4 mmol of (TMS) 3 P was added to the mixture and it was stirred for 2 hours under N 2 atmosphere. Purification of 386-MSCs. As-synthesized 386-MSCs were purified with toluene as solvent and acetonitrile as anti- solvent twice by precipitation-dissolution. First, 35 mL acetonitrile was added into 0.5 mL 386-MSCs solution in conical tube and followed by centrifugation (4500 rpm, 3 minutes). After discarding transparent supernatant and drying, yellow precipitants were dissolved with 0.5 mL anhydrous toluene. 35 mL acetonitrile was added into 0.5 mL 386-MSCs solution again and followed by centrifugation (4500 rpm, 3 minutes). Final products were stored in anhydrous toluene. General procedure for synthesis of InP NPs from molecular precursors. First, 0.4 mmol of In(Ac) 3 and 1.2 mmol of HMy were prepared in 12 mL ODE. The solution was degassed for 2 hours at 110 °C and cool down to room temperature, then 0.4 mmol of (TMS) 3 P was added to the mixture. The mixture solution was heated to 300 °C and maintained for 30 minutes under N 2 atmosphere. Heating rate is around 20 °C/min. General procedure for synthesis of InP NPs from purified 386-MSCs. First, 12 mL ODE was degassed for 1 hour at 110 °C and cool down to room temperature. Purified 386-MSCs in toluene was added to ODE making 0.44 mM solution at room temperature and the toluene was removed under vacuum. After that, the solution was heated to 300 °C. Heating rate is around 20 °C/min. The temperature was maintained for 30 minutes and followed by cooling down. General procedure for synthesis of InP NPs from purified 386-MSCs and In(My) 3 . First, 0.3 mmol of In(Ac) 3 and 0.9 mmol of HMy were prepared in 12 mL ODE. The solution was degassed for 2 hours at 110 °C and cool down to room temperature. Purified 386-MSCs in toluene was added to In(My) 3 solution making 0.44 mM solution at room temperature and the toluene was removed under vacuum. After that, the solution was heated to 300 °C. Heating rate is around 20 °C/min. The temperature was maintained for 30 minutes and followed by cooling down. General procedure for synthesis of InP NPs from as-synthesized 386-MSCs. First, 4 mL ODE was degassed for 1 hour at 110 °C and cool down to room temperature. As-synthesized 386-MSCs solution with 8 mL volume was injected into ODE at room temperature. After that, the solution containing the 386-MSCs was heated to 300 °C. Heating rate is around 20 °C/min. The temperature was maintained for 30 minutes and followed by cooling down. Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C. This journal is © The Royal Society of Chemistry 2019