Supporting Information
Journal of Nanoparticle Research
Photocatalytic Synthesis of Intensely Photoluminescent Gold Nanoclusters and Application in Cell Imaging
Ming Wei, Ye Tian, Lijun Wang, Yuankai Hong, and Yinlin Sha*
Single-molecule and Nanobiology Laboratory, Department of Biophysics, School of Basic Medical Sciences, and Biomed-X Center, Peking University, Beijing 100191, P. R. China
E-mail: ; Tel: +86-10-8280-1278
1. Exploration of optimal synthesis condition
The optimal condition for synthesis of high PL QY AuNC@TMT was explored by adjusting the molar concentration of TMT, pH value and wavelength of irradiation, and PL efficiency were measured at 400 nm. The concentration of tetrachloroauric acid and temperature were fixed to 0.99 mM and 25 ℃ respectively. First, the pH value and wavelength of irradiation were fixed to 9 and 365 nm respectively to determine the optimal molar concentration of TMT (Fig. S2). Then, the molar concentration and wavelength of irradiation were fixed to 1.98 mM and 365 nm respectively to determine the optimal pH value (Fig. S3). Last, the molar concentration and pH value were fixed to 1.98 mM and 9 to determine the optimal wavelength of irradiation (Fig. S4). From Fig. S2, S3 and S4, we can know that when molar concentration of TMT, pH value and wavelength of irradiation are 1.98 mM, 9 and 365 nm respectively, the PL efficiency is maximal at 70 minutes.
2. Caculation of the average relative molecular mass
For the purpose of obtaining the average relative molecular mass of AuNC@TMT, in addition to TEM result, thermogravimetric analysis (TGA) result is also needed. In Fig. S6, we can know that the moisture content was 1.8%, and the ligands were 40.9%, while the gold was 57.3% in weight. After we know the mass ratio of the gold and liands, the molar ratio can be aquired. Based on the average diameter of gold core measured in TEM image, the average number of gold atoms in each AuNC@TMT is about 149 depending on the formula N(Au)=n*NA=(m/M)*NA=(ρV/M)*NA (Liu et al. 2009), so the number of TMT is 101 depending on TGA result. Therefore, the molecular formula of AuNC@TMT is Au149TMT101.
3. Cytotoxicity Measurement
The cytotoxicity measurements were performed by MTT assay. Briefly, HepG2 cells were trypsinized and resuspended in DMEM containing 10% FBS and 1% penicillin/streptomycin. The cells were seeded at a density of 5000 cells per well in a 96-well plate. After 24 h of incubation at 37 ℃ with 5% CO2 the cells were washed with PBS (100 mM Na2HPO4, 20 mM KH2PO4, 137 mM NaCl, 27 mM KCl, pH 7.4). The AuNC@TMT solutions with different concentrations (10 mL, 0.002-0.5 mg/mL) and DMEM (90 mL) were added to the wells. After 24 h of incubation, the supernatant was removed, and the cells were washed with PBS three times. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT, Amresco) solution (10 μL, 0.5 mg/mL) was then added to each well. After 4 h of incubation, the medium was discarded and the intracellular water-insoluble formazan blue was collected by DMSO (100 μL). The optical absorbance was measured at 570 nm on a BioRad model 550 microplate reader. Each data point was collected by averaging that of 6 wells, and the cells treated with 100 mL DMEM (without AuNC@TMT, 0 mg/mL) were used as controls. Hela cells were also used for cytotoxicity measurements with the same process.
Fig. S1 The simulation diagram of synthesizing AuNC@TMT, under 365 nm or 254 nm UV lamp (6 Watts for both of them), the distance about 10 centimeters between the lamp and the liquid level
Fig. S2 Under different concentrations of TMT to synthesize AuNC@TMT, fixing the pH value and wavelength of irradiation to 9 and 365 nm respectively
Fig. S3 Under different pH values to synthesize AuNC@TMT, fixing the concentration of TMT and wavelength of irradiation to 1.98 mM and 365 nm respectively
Fig. S4 Under different wavelengths of irradiation to synthesize AuNC@TMT, fixing the concentration of TMT and pH value to 1.98 mM and 9 respectively
Fig. S5 The photoluminescence quantum yield (PL QY) of AuNC@TMT.
PL QY=63340/304786*0.95=19.7%.
Fig. S6 TGA spectrum of as-synthesized AuNC@TMT, the moisture content occupied 1.8% in weight, and the ligands occupied 40.9% in weight
Fig. S7 Time courses of PL intensity changes of AuNC@TMT containing 1 mg/mL ascorbic acid under continuous excitaion for 3600 s.
Fig. S8 Time courses of PL intensity changes of AuNC@TMT-Gal under continuous excitaion for 3600 s.
Fig. S9 AuNC@TMT incubated with HepG2 cells for 2 hours at 37 ℃. a) DIC, b) Fluorescence and c) Merge of DIC and Fluorescence, and AuNC@TMT-Gal incubated with Hela cells for 2 hours at 37 ℃. d) DIC, e) Fluorescence and f) Merge of DIC and Fluorescence.
References
Liu C-L et al. (2009) Thiol-functionalized gold nanodots: two-photon absorption property and imaging in vitro The Journal of Physical Chemistry C 113:21082-21089 doi:10.1021/jp9080492
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