Supporting Information Ag2Se Quantum Dots with Tunable Emission ...
Supporting Information
Ag2Se 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 430072, P. R. China ‡
Wuhan Institute of Biotechnology, Wuhan 430075, P. R. China
§
Research Center of Ion Beam Application in Functional Materials, Wuhan University, Wuhan 430072, P. R. China
* [email protected]
Experimental Section Materials Se powder (≥99.5%), 1-octanethiol (≥98.5%), oleic acid (OAc, 90%), and indocyanine green (ICG, polymethine dye) were purchased from Sigma Aldrich. Oleylamine (OAm, approximate C18-content 80-90%) and 1-octadecene (ODE, tech. 90%) were purchased from ACROS. Tri-n-octylphosphine (TOP, tech. 90%), tetradecylphosphonic acid (TDPA, 98%), and tetrachloroethylene (C2Cl4, 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 Ag2Se quantum dots Preparation of Se stock solution: 0.1 mmol of Se was dissolved in 1.5 mL of TOP under inert atmosphere (denoted as TOPSe). In a typical synthesis, 0.1 mmol of AgAc, 1.64 mmol of 1-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 160 °C under vigorous stirring. Subsequently, the growth of Ag2Se quantum dots proceeded at 130 °C. To monitor the growth of the nanoparticles, aliquots were
taken at different reaction times for absorption and FL measurements. The products were mixed with acetone and precipitated through centrifugation at 10000 rpm for 3 min. The precipitate was dispersed in nonpolar solvents for further characterizations. The as-prepared Ag2Se quantum dots were transferred to the aqueous phase by ligand exchange as our previous report.1 Ag2Se quantum dots dispersed in n-hexane were mixed with an ethanol solution containing 11-mercaptoundecanoic acid. The mixture was magnetically stirred overnight. After evaporating the solvents, the final Ag2Se quantum dots were washed with ethanol and dispersed in 0.1 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 1600 nm). C2Cl4 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 ≈ 0.13 in DMSO). Transmission electron microscopy (TEM) images and high-resolution TEM (HRTEM) images were obtained on a JEM-2010FEF (UHR) electron microscope operated at 200 kV. Energy dispersive X-ray (EDX) measurement was performed using a JEM-2010FEF (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 Kα radiation (wavelength 1.5406 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 iS10 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.
Figure S1. Temporal shape evolution of nanoparticles when OAm was used.
Figure S2. Temporal shape evolution of nanoparticles when TDPA was used.
Figure S3. XRD pattern of 3.9 nm Ag2Se QDs grown for 1 h.
For the orthorhombic Ag2Se with the unit cell parameters of a=4.333, b=7.062 and c=7.764 (JCPDS Card No. 24-1041), the interplanar angle Φ could be calculated according to the following equation:
h1h2 k1k 2 l1l 2 + 2 + 2 2 a b c cos Φ = 2 2 2 2 h1 k1 l1 h2 k 22 l 22 ( 2 + 2 + 2 )( 2 + 2 + 2 ) a b c a b c
Figure S4. HRTEM images of Ag2Se QDs with different reaction times: 1 min (A), 5 min (B), and 1 h (C).
Table S1. Comparison of interplanar angles Φ calculated from lattice parameters and those measured from HRTEM images sample A
lattice planes (122) (d=0.222 nm)
calculated interplanar
interplanar angle Φ measured
angle Φ (º)
from HRTEM images (º)
58.9
57.4
55.6
55.3
73.1
72.7
(200) (d=0.216 nm) B
(013) (d=0.246 nm) (121) (d=0.259 nm)
C
(031) (d=0.225 nm) (004) (d=0.192 nm)
Figure S5. EDX spectrum of the as-prepared Ag2Se QDs.
Figure S6. (A) XPS survey spectrum of the as-prepared Ag2Se QDs. High-resolution XPS spectra of Ag 3d (B), Se 3d (C) and S 2p (D).
Figure S7. FT-IR spectrum of the as-prepared Ag2Se QDs. The peaks at 2954, 2923 and 2852 cm-1 corresponded to asymmetric and symmetric stretching vibrations of methyl and methylene. The absence of a peak at 2490 cm-1 suggested the inexistence of free thiols.2,3 Bending vibration peak of methylene appeared at 1464 cm-1. The peaks at 1377 and 1262 cm-1 can be attributed to bending vibrations of C-CH3 and CH2-S, respectively. The bands at 3438 cm-1 and 1630 cm-1 could be assigned to the O-H stretching and the H-O-H bending of water molecules4,5 absorbed by KBr in
the process of FT-IR characterization.
Figure S8. Absorption spectra (A) and Tauc plots (B) 6,7of Ag2Se QDs with reaction time of 1 min, 5 min and 1 h, respectively.
Figure S9. (A) Size (11.16 ± 0.61 nm) and (B) zeta potential (-39.8 mV) distributions of water-soluble Ag2Se QDs with emission at 1090 nm.
Figure S10. FL emission spectra of Ag2Se QDs emitting at 1180 nm before/after ligand exchange. REFERENCES (1) Jiang, P.; Tian, Z. Q.; Zhu, C. N.; Zhang, Z. L.; Pang, D. W. Chem. Mater. 2012, 24, 3-5. (2) Cumberland, S. L.; Berrettini, M. G.; Javier, A.; Strouse, G. F. Chem. Mater. 2003, 15, 1047-1056. (3) Wu, L.; Quan, B. G.; Liu, Y. L.; Song, R.; Tang, Z. Y. ACS Nano 2011, 5, 2224-2230. (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. 2009, 48, 11559-11565. (5) Ohno, Y.; Tomita, K.; Komatsubara, Y.; Taniguchi, T.; Katsumata, K.; Matsushita, N.; Kogure, T.; Okada, K. Cryst. Growth Des. 2011, 11, 4831-4836. (6) Harpeness, R.; Palchik, O.; Gedanken, A.; Palchik, V.; Amiel, S.; Slifkin, M. A.; Weiss, A. M. Chem. Mater. 2002, 14, 2094-2102. (7) Anthony, S. P. Mater. Lett. 2009, 63, 773-776.
Ag2Se 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 430072, P. R. China ‡
Wuhan Institute of Biotechnology, Wuhan 430075, P. R. China
§
Research Center of Ion Beam Application in Functional Materials, Wuhan University, Wuhan 430072, P. R. China
* [email protected]
Experimental Section Materials Se powder (≥99.5%), 1-octanethiol (≥98.5%), oleic acid (OAc, 90%), and indocyanine green (ICG, polymethine dye) were purchased from Sigma Aldrich. Oleylamine (OAm, approximate C18-content 80-90%) and 1-octadecene (ODE, tech. 90%) were purchased from ACROS. Tri-n-octylphosphine (TOP, tech. 90%), tetradecylphosphonic acid (TDPA, 98%), and tetrachloroethylene (C2Cl4, 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 Ag2Se quantum dots Preparation of Se stock solution: 0.1 mmol of Se was dissolved in 1.5 mL of TOP under inert atmosphere (denoted as TOPSe). In a typical synthesis, 0.1 mmol of AgAc, 1.64 mmol of 1-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 160 °C under vigorous stirring. Subsequently, the growth of Ag2Se quantum dots proceeded at 130 °C. To monitor the growth of the nanoparticles, aliquots were
taken at different reaction times for absorption and FL measurements. The products were mixed with acetone and precipitated through centrifugation at 10000 rpm for 3 min. The precipitate was dispersed in nonpolar solvents for further characterizations. The as-prepared Ag2Se quantum dots were transferred to the aqueous phase by ligand exchange as our previous report.1 Ag2Se quantum dots dispersed in n-hexane were mixed with an ethanol solution containing 11-mercaptoundecanoic acid. The mixture was magnetically stirred overnight. After evaporating the solvents, the final Ag2Se quantum dots were washed with ethanol and dispersed in 0.1 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 1600 nm). C2Cl4 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 ≈ 0.13 in DMSO). Transmission electron microscopy (TEM) images and high-resolution TEM (HRTEM) images were obtained on a JEM-2010FEF (UHR) electron microscope operated at 200 kV. Energy dispersive X-ray (EDX) measurement was performed using a JEM-2010FEF (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 Kα radiation (wavelength 1.5406 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 iS10 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.
Figure S1. Temporal shape evolution of nanoparticles when OAm was used.
Figure S2. Temporal shape evolution of nanoparticles when TDPA was used.
Figure S3. XRD pattern of 3.9 nm Ag2Se QDs grown for 1 h.
For the orthorhombic Ag2Se with the unit cell parameters of a=4.333, b=7.062 and c=7.764 (JCPDS Card No. 24-1041), the interplanar angle Φ could be calculated according to the following equation:
h1h2 k1k 2 l1l 2 + 2 + 2 2 a b c cos Φ = 2 2 2 2 h1 k1 l1 h2 k 22 l 22 ( 2 + 2 + 2 )( 2 + 2 + 2 ) a b c a b c
Figure S4. HRTEM images of Ag2Se QDs with different reaction times: 1 min (A), 5 min (B), and 1 h (C).
Table S1. Comparison of interplanar angles Φ calculated from lattice parameters and those measured from HRTEM images sample A
lattice planes (122) (d=0.222 nm)
calculated interplanar
interplanar angle Φ measured
angle Φ (º)
from HRTEM images (º)
58.9
57.4
55.6
55.3
73.1
72.7
(200) (d=0.216 nm) B
(013) (d=0.246 nm) (121) (d=0.259 nm)
C
(031) (d=0.225 nm) (004) (d=0.192 nm)
Figure S5. EDX spectrum of the as-prepared Ag2Se QDs.
Figure S6. (A) XPS survey spectrum of the as-prepared Ag2Se QDs. High-resolution XPS spectra of Ag 3d (B), Se 3d (C) and S 2p (D).
Figure S7. FT-IR spectrum of the as-prepared Ag2Se QDs. The peaks at 2954, 2923 and 2852 cm-1 corresponded to asymmetric and symmetric stretching vibrations of methyl and methylene. The absence of a peak at 2490 cm-1 suggested the inexistence of free thiols.2,3 Bending vibration peak of methylene appeared at 1464 cm-1. The peaks at 1377 and 1262 cm-1 can be attributed to bending vibrations of C-CH3 and CH2-S, respectively. The bands at 3438 cm-1 and 1630 cm-1 could be assigned to the O-H stretching and the H-O-H bending of water molecules4,5 absorbed by KBr in
the process of FT-IR characterization.
Figure S8. Absorption spectra (A) and Tauc plots (B) 6,7of Ag2Se QDs with reaction time of 1 min, 5 min and 1 h, respectively.
Figure S9. (A) Size (11.16 ± 0.61 nm) and (B) zeta potential (-39.8 mV) distributions of water-soluble Ag2Se QDs with emission at 1090 nm.
Figure S10. FL emission spectra of Ag2Se QDs emitting at 1180 nm before/after ligand exchange. REFERENCES (1) Jiang, P.; Tian, Z. Q.; Zhu, C. N.; Zhang, Z. L.; Pang, D. W. Chem. Mater. 2012, 24, 3-5. (2) Cumberland, S. L.; Berrettini, M. G.; Javier, A.; Strouse, G. F. Chem. Mater. 2003, 15, 1047-1056. (3) Wu, L.; Quan, B. G.; Liu, Y. L.; Song, R.; Tang, Z. Y. ACS Nano 2011, 5, 2224-2230. (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. 2009, 48, 11559-11565. (5) Ohno, Y.; Tomita, K.; Komatsubara, Y.; Taniguchi, T.; Katsumata, K.; Matsushita, N.; Kogure, T.; Okada, K. Cryst. Growth Des. 2011, 11, 4831-4836. (6) Harpeness, R.; Palchik, O.; Gedanken, A.; Palchik, V.; Amiel, S.; Slifkin, M. A.; Weiss, A. M. Chem. Mater. 2002, 14, 2094-2102. (7) Anthony, S. P. Mater. Lett. 2009, 63, 773-776.
