Biomimetic synthesis of gold nanocrystals using a reducing amphiphile. Ferdinand Gonzaga, Sherdeep Singh and Michael A. Brook. Department of Chemistry

Transcription

1 Biomimetic synthesis of gold nanocrystals using a reducing amphiphile. Ferdinand Gonzaga, Sherdeep Singh and Michael A. Brook Department of Chemistry 1280 Main St. W. Hamilton ON L8S 4M1 Canada Outline of Supporting Information 1) Experimental 2) UV-Visible spectroscopy and kinetics of formation 3) Imaging techniques and EDX spectroscopy 3.1.TEM and High Resolution TEM 3.2 SEM 3.3 AFM 3.4 EDX Spectroscopy 4) X-Ray spectroscopy 5) Supporting Figures Referred to in the main text Figure S1 Additional TEM images of gold nanoleaves. Figure S2 Additional SEM images of gold nanoleaves. Figure S3 EDX analysis of gold nanoleaves. Figure S4 Control experiments with Citric acid and with lipid 5 in a THF-Water binary solvent. Figure S5 Kinetic study of lipid 5-induced gold reduction at ph Figure S6 Kinetic study of lipid 5-induced gold reduction at ph Figure S7 Kinetic study of lipid 5-induced gold reduction at ph Figure S8 UV-Vis characterization of intermediate lipid 5-gold (III) complexes. 1

2 Figure S9 Gold nanoplates produced at ph 6.30 in the dark and their corresponding UV-Vis absorbance. Figure S10 Gold colloids produced at ph

3 Supporting Information 1) UV-Visible spectroscopy and kinetics of formation UV-Vis-NIR spectroscopic measurements of colloids were performed with a Varian Cary 50 Probe spectrometer. Kinetic for the ambient synthesis were performed by transferring the content of a synthesis experiment into a UV-Vis cuvette followed by spectra recording, at different times of reaction. Kinetics for the dark experiments were realized by transferring the content of a dark synthesis experiment into a UV cuvette under reduced light conditions. To avoid any UV-spectrometer irradiation effect, every spectrum was recorded from a different synthesis experiment. 2) Imaging techniques and EDX spectroscopy 2.1) TEM and High Resolution TEM TEM imaging was performed with a JEOL JEM 1299 EX TEMSCAN transmission electron microscope (JEOL, Peabody, MA, USA) operated at an accelerating voltage of 80 kv. High-Resolution TEM was carried out with a JEOL 2010 field emission TEM/STEM, operating at an accelerating voltage of 200kV. Sample preparation: a 4 µl drop of as synthesized or purified gold nanoleaves was deposited over a formvar-coated TEM grid, and the excess solution was blotted with Kimwipe paper. The resulting thin film was dried under ambient conditions before being imaged. The same procedure was used for High-Resolution TEM, but samples were deposited over carbon holey grids. 2.2) SEM 3

4 SEM imaging was performed with a JEOL JSM-7000F Scanning Electron Microscope, equipped with a Schottky type Field Emission Gun (FEG) filament. Sample preparation: 2µL of a concentrated solution of purified gold nanoleaves were directly deposited on a SEM stub. The drop was allowed to evaporate under ambient conditions. A second drop (2 µl) was then deposited over the first evaporated ring, allowed to evaporate before imaging. 2.3) AFM Atomic force microscopy was performed in tapping mode on a Veeco Enviroscope with a Nanoscope IIIa controller and Veeco RTESP p-doped Si tips with a nominal radius of less than 10 nm. 2.4) Energy-Dispersive X-Ray Spectroscopy (EDX) Energy dispersive X-ray (EDX) spectra of elements with atomic numbers greater than 10 were obtained using a Tracor Northern X-ray detector (Noran, Madison, Wisconsin, USA) and EDS 2004 microanalysis software (IXRF Systems Inc., Houston, Texas, USA). 3) X-Ray spectroscopy X-Ray diffraction analysis was acquired on a Bruker D8 Advance Powder Diffractometer using Copper Kα1 radiation. Sample preparation: a glass cylinder (1 cm diameter) was pasted over a microscope glass slide. 2 ml of a purified gold nanoleaf aqueous solution was introduced into the cylinder, and the leaves were allowed to settle (until solution turned colorless). The supernatant layer was then carefully removed with a Pasteur pipette, and the residual thin film was dried in the dark under ambient conditions before being analyzed. 4

5 Figure S1 a, b and c, TEM of gold nanoleaves prepared at ph 7.30, showing the presence of geometric (triangles, truncated triangles, hexagons) or fractal shapes. d, HRTEM of an edge of a gold nanoleaf, showing well-resolved lattice fringes, and the presence of a diffuse layer of lipid 5 at the interface. 5

6 Figure S2 a, Rolled film of gold nanoleaves. b, detail of the gold nanoleaves film c, some nanoleaves appear as large and flat crystals; the thinnest ones (central part of the image) can bend and roll. d, Typical gold nanoleaves, presenting both geometrical and fractal shapes. 6

7 Figure S3 EDX analysis of gold nanoleaves prepared at ph 7.30 (from crystals shown in Figure S1). Spectrum indicates the presence of elemental Gold and Silicon (from lipid 5). The Copper peaks come from the TEM grid. 7

8 Figure S4 a, b Typical Gold structures obtained when reduction occurs in a binary solvent system which prevents lipid 1 self-assembly (1:1, v:v, THF:H 2 O), at ph 6.30 and 7.30, respectively. Only ill-defined polycrystalline structures were observed. c, d Roughly spherical gold nanoparticles are produced when lipid 5 is replaced by citric acid, at ph 7.30 and 6.30 respectively. All others experimental conditions (light exposure and concentrations) were kept identical to the process described previously in order to be comparative. 8

9 2.4 2 Absorbance Wavelength (nm) On mixing 1Hour 2Hours 4Hours 8Hours 12Hours 16Hours 20Hours 24Hours 48Hours b: dark conditions Absorbance Wavelength (nm) 12Hours 24Hours 48Hours Figure S5 a, b Evolution of the UV-Vis spectra during the lipid 5-catalyzed formation of gold nanoleaves at ph 6.30, in the presence or absence of light, respectively. The overall absorbance in the dark process was lower then in the light process, due to precipitation of micrometer-sized gold nanoplates. 9

10 2.4 2 Absorbance Wavelength (nm) 0.5hour 7hours 13hours 18hours 21hours 24hours 34hours 41hours 48hours 72hours 96hours b: dark conditions Absorbance hours 13hours Wavelength (nm) 21hours 34hours 48hours 72hours 96hours 120hours 144hours Figure S6 a, b Evolution of the UV-Vis spectra during the lipid 5-catalyzed formation of gold nanoleaves at ph 7.30, in the presence or absence of light, respectively. 10

11 1.6 Absorbance Wavelength (nm) 0.5Hours 7Hours 13Hours 21Hours 24Hours 34Hours 48Hours 72Hours 96Hours 120Hours 144Hours b: dark conditions 1.6 Absorbance Wavelength (nm) 5Hours 13Hours 21Hours 34Hours 48Hours 72Hours 96Hours 120Hours 144Hours Figure S7 a, b Evolution of the UV-Vis spectra during the lipid 5-catalyzed formation of gold nanoleaves at ph 8.30, in the presence or absence of light, respectively. 11

12 Absorbance Wavelength (nm) On mixing 1Hour 2Hours 4Hours 8Hours Figure S8 UV-Vis evolution with time reveals that appearance of 2 new absorptions at 419 and 448 nm, attributed to lipid 5-gold complexes. Spectra are taken from Figure S5a (ph 6.30, light conditions). These 2 new bands appear after 1 hour, and are not visible anymore after 12 hours. 12

13 Figure S9 a, b Representative images of gold nanoplates prepared at ph 6.30 in the absence of light, showing large gold nanoplates with size over 1 micrometer. c, Compared UV-Vis spectra of gold colloids prepared at ph 6.30, in the light or dark conditions. Gold nanoplates prepared in the dark aggregate, and can be visually observed in the vial (golden aspect), while gold nanoleaves remain in solution for days (see Figure 1). 13

14 a b 50 nm 50 nm Figure S10 a, b Representative images of gold colloids prepared at ph 8.30 in ambient conditions. Roughly spherical polydisperse particles are obtained, with a few prisms and parallelograms, and ill-defined particles. A marginal amount of thin nanowires were also found, as seen in b. 14