Supporting Information
Monitoring the Formation Process of Gold Nanomaterials by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry
Iva Tomalová1, Chia-Hsin Lee2, Wen-Tsen Chen2, Cheng-Kang Chiang2, Huan-Tsung Chang 2*, and Jan Preisler, 1*
1CEITEC MU and Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, Brno, Czech Republic. 2Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 106, Taiwan.
Correspondence/Address reprint requests to:
Jan Preisler, CEITEC MU and Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, Brno, Czech Republic, Tel: 00420-549-49-6629; E-mail:
Huan-Tsung Chang, Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 106, Taiwan, Tel: 011-886-2-33661171, E-mail:
Figure S1. Representative SALDI mass spectra of solution of 10 mM phosphate (pH 7.2)
and 200 μM dopamine with 14 nm AuNPs as SALDI matrixes. The peak at m/z 176.07 was assigned to [dopamine + Na]+ ion
Figure S2. (a) UV-Vis absorbance spectra of the solutions containing 200 μM HAuCl4, and 10 mM phosphate (pH 7.2) in the addition of various concentration of dopamine (0–1000 μM). The absorbance intensities are plotted in arbitrary units (a.u.). (b-d) TEM images of the solutions containing 200 μM HAuCl4 in the addition of (b) 100, (c) 200, and (d) 400 μM dopamine, respectively
Figure S3. SALDI mass spectra of solutions containing 200 μM HAuCl4 in the (a) absence and presence of (b) 100, (c) 200, (d) 300, (e) 400, and (f) 500 μM catechin. The peaks at m/z 287.05 and 289.07 were assigned to the [quinone – H]– and [catechin – H]– ions, respectively
Characterization of catechin-reduced AuNPs
The UV-Vis results (Figure S4a) show that the absorbance of the AuNPs at 540 nm is first intensified and the absorbance maxima are eventually red-shifted as the concentration of catechin was increased above 400 μM. The TEM images of the prepared AuNPs (Figure S4b–d), revealed that the sizes of AuNPs are within similar particle dimension (20–30 nm) upon increasing the catechin concentrations from 200 to 400 μM. The AuNPs possessed core-shell structures, probably due to the oxidized- and reduced-residues of catechin molecules assembled on the AuNP surfaces. By adding 400 μM catechin or higher, three-dimensional branched Au nanomaterials having the size of ca 10 nm of low contrast were observed. The branched Au nanomaterials were formed through the self-assembly of short nanorods. At the same time, the SALDI-MS spectra indicated that the excess amount of non-oxidized catechin form played an important role in reduction of Au(III) ions to form larger AuNPs and in stabilizing the branched Au nanomaterials. This implies that the SALDI-MS method is not only useful in the analysis of adsorbates on AuNPs, but can also reflect the direct information of the chemical redox reaction in the aqueous solution.
Figure S4. (a) UV-Vis absorbance spectra of the solutions containing 200 μM HAuCl4 in the addition of different concentration of catechin (0–1000 μM). (b-d) TEM images of the solutions containing 200 μM HAuCl4 in the addition of (b) 200, (c) 300, and (d) 400 μM catechin, respectively
Figure S5. SALDI mass spectra of solutions containing 200 μM HAuCl4, and phosphate (10 mM, pH 7.2) in the (a) absence and presence of (b) 100, (c) 200, (e) 400, (d) 500 and (f) 1000 μM ascorbic acid. The signals at m/z 173.01 and 175.02 were assigned to the monoisotopic forms of ions [dehydroascorbic acid – H]– and [ascorbic acid – H]–, respectively
SALDI-MS assays for ascorbic acid reduced AuNPs – AuNP characterization
The absorbance spectra of the AuNPs prepared by reduction of ascorbic acid (Figure S6a) displayed no observed change of absorbance maxima at 525 nm when employing the ascorbic acid in the concentrations ranging from 300 μM to 1 mM while flatter and slightly red-shifted absorbance maxima were observed at lower concentrations of ascorbic acid. The conclusions from UV-Vis spectra were in agreement with TEM images (Figure S6b-d), which showed that the AuNPs with lower size dispersity (15–30 nm) were prepared by the reduction with ascorbic acid at a concentration higher than 300 μM, whereas variously shaped and sized AuNPs were formed upon lowering the concentration of ascorbic acid below 300 μM.
Figure S6. UV-Vis absorbance spectra of the solutions containing 200 μM HAuCl4, and 10 mM phosphate (pH 7.2) in the addition of various concentration of ascorbic acid (0–1 mM). The absorbance intensities are plotted in arbitrary units (a.u.). (b–d) TEM images of the solutions containing 200 μM HAuCl4 in the addition of (b) 200, (c) 300, and (d) 400 μM ascorbic acid, respectively.