Supporting Information. Dai-Wen Pang,

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1 Supporting Information Ag Se Quantum Dots with Tunable Emission in the Second Near-Infrared Window Chun-Nan Zhu,, Peng Jiang,, Zhi-Ling Zhang,, Dong-Liang Zhu,, Zhi-Quan Tian, *,,, and Dai-Wen Pang, Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 43007, P. R. China Wuhan Institute of Biotechnology, Wuhan , P. R. China Research Center of Ion Beam Application in Functional Materials, Wuhan University, Wuhan 43007, P. R. China * zqtian@whu.edu.cn Experimental Section Materials Se powder ( 99.5%), -octanethiol ( 98.5%), oleic acid (OAc, 90%), and indocyanine green (ICG, polymethine dye) were purchased from Sigma Aldrich. Oleylamine (OAm, approximate C8-content 80-90%) and -octadecene (ODE, tech. 90%) were purchased from ACROS. Tri-n-octylphosphine (TOP, tech. 90%), tetradecylphosphonic acid (TDPA, 98%), and tetrachloroethylene (C Cl 4, 99%) were purchased from Alfa Aesar. Silver acetate (AgAc), dimethyl sulfoxide (DMSO), n-hexane, methanol, and acetone were purchased from China National Pharmaceutical Group Corporation. Synthesis of Ag Se quantum dots Preparation of Se stock solution: 0. mmol of Se was dissolved in.5 ml of TOP under inert atmosphere (denoted as TOPSe). In a typical synthesis, 0. mmol of AgAc,.64 mmol of -octanethiol and 5 ml of ODE were loaded into a three-neck flask filled with argon. Then the TOPSe solution was swiftly injected into the reaction mixture at 60 C under vigorous stirring. Subsequently, the growth of Ag Se quantum dots proceeded at 30 C. To monitor the growth of the nanoparticles, aliquots were

2 taken at different reaction times for absorption and FL measurements. The products were mixed with acetone and precipitated through centrifugation at 0000 rpm for 3 min. The precipitate was dispersed in nonpolar solvents for further characterizations. The as-prepared Ag Se quantum dots were transferred to the aqueous phase by ligand exchange as our previous report. Ag Se quantum dots dispersed in n-hexane were mixed with an ethanol solution containing -mercaptoundecanoic acid. The mixture was magnetically stirred overnight. After evaporating the solvents, the final Ag Se quantum dots were washed with ethanol and dispersed in 0. M NaOH solution. Characterizations Absorption spectra were recorded with a UV-3600 ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (SHIMADZU). FL spectra were measured on a Fluorolog-3 fluorescence spectrophotometer (HORIBA JOVIN YVON INC.) equipped with a liquid nitrogen cooled InGaAs detector (between 800 nm to 600 nm). C Cl 4 was employed as the solvent for absorption and FL spectra. FL quantum yields (QYs) of the samples were determined through comparison using an ICG standard organic dye (Φ 0.3 in DMSO). Transmission electron microscopy (TEM) images and high-resolution TEM (HRTEM) images were obtained on a JEM-00FEF (UHR) electron microscope operated at 00 kv. Energy dispersive X-ray (EDX) measurement was performed using a JEM-00FEF (UHR) electron microscope equipped with an EDX spectrometer (EDAX Inc.). Powder X-ray diffraction (XRD) pattern was obtained on a Bruka D8 Advanced X-Ray diffractometer (Bruker axs) using Cu K α radiation (wavelength.5406 Å). X-ray photoelectron spectroscopy (XPS) spectra were collected on a Kratos XSAM 800 spectrometer. Fourier transform infrared (FT-IR) analysis was conducted using pressed KBr pellets with a Thermo Scientific Nicolet is0 spectrometer. It should be noted that all the samples for XRD, XPS, and FT-IR measurements were washed five times with methanol to remove excess precursors and ligands.

3 Figure S. Temporal shape evolution of nanoparticles when OAm was used. Figure S. Temporal shape evolution of nanoparticles when TDPA was used.

4 Figure S3. XRD pattern of 3.9 nm Ag Se QDs grown for h. For the orthorhombic Ag Se with the unit cell parameters of a=4.333, b=7.06 and c=7.764 (JCPDS Card No. 4-04), the interplanar angle Φ could be calculated according to the following equation: ) )( ( cos c l b k a h c l b k a h c l l b k k a h h Φ = Figure S4. HRTEM images of Ag Se QDs with different reaction times: min (A), 5 min (B), and h (C).

5 Table S. Comparison of interplanar angles Φ calculated from lattice parameters and those measured from HRTEM images sample lattice planes calculated interplanar angle Φ (º) interplanar angle Φ measured from HRTEM images (º) A () (d=0. nm) (00) (d=0.6 nm) B (03) (d=0.46 nm) () (d=0.59 nm) C (03) (d=0.5 nm) (004) (d=0.9 nm) Figure S5. EDX spectrum of the as-prepared Ag Se QDs.

6 Figure S6. (A) XPS survey spectrum of the as-prepared Ag Se QDs. High-resolution XPS spectra of Ag 3d (B), Se 3d (C) and S p (D). Figure S7. FT-IR spectrum of the as-prepared Ag Se QDs. The peaks at 954, 93 and 85 cm - corresponded to asymmetric and symmetric stretching vibrations of methyl and methylene. The absence of a peak at 490 cm - suggested the inexistence of free thiols.,3 Bending vibration peak of methylene appeared at 464 cm -. The peaks at 377 and 6 cm - can be attributed to bending vibrations of C-CH 3 and CH -S, respectively. The bands at 3438 cm - and 630 cm - could be assigned to the O-H stretching and the H-O-H bending of water molecules 4,5 absorbed by KBr in

7 the process of FT-IR characterization. Figure S8. Absorption spectra (A) and Tauc plots (B) 6,7 of Ag Se QDs with reaction time of min, 5 min and h, respectively. Figure S9. (A) Size (.6 ± 0.6 nm) and (B) zeta potential (-39.8 mv) distributions of water-soluble Ag Se QDs with emission at 090 nm.

8 Figure S0. FL emission spectra of Ag Se QDs emitting at 80 nm before/after ligand exchange. REFERENCES () Jiang, P.; Tian, Z. Q.; Zhu, C. N.; Zhang, Z. L.; Pang, D. W. Chem. Mater. 0, 4, 3-5. () Cumberland, S. L.; Berrettini, M. G.; Javier, A.; Strouse, G. F. Chem. Mater. 003, 5, (3) Wu, L.; Quan, B. G.; Liu, Y. L.; Song, R.; Tang, Z. Y. ACS Nano 0, 5, (4) Yang, M.; You, H. P.; Zheng, Y. H.; Liu, K.; Jia, G.; Song, Y. H.; Huang, Y. J.; Zhang, L. H.; Zhang, H. J. Inorg. Chem. 009, 48, (5) Ohno, Y.; Tomita, K.; Komatsubara, Y.; Taniguchi, T.; Katsumata, K.; Matsushita, N.; Kogure, T.; Okada, K. Cryst. Growth Des. 0,, (6) Harpeness, R.; Palchik, O.; Gedanken, A.; Palchik, V.; Amiel, S.; Slifkin, M. A.; Weiss, A. M. Chem. Mater. 00, 4, (7) Anthony, S. P. Mater. Lett. 009, 63,