Supporting Information. for. Gold Nanoparticles Supported on Alumina as a Catalyst for Surface Plasmon-Enhanced Selective Reductions of Nitrobenzene

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1 Supporting Information for Gold Nanoparticles Supported on Alumina as a Catalyst for Surface Plasmon-Enhanced Selective Reductions of Nitrobenzene Kittichai Chaiseeda, Shun Nishimura, and Kohki Ebitani * School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa, , Japan Natural Products Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand S1

2 For Table of Contents Only: 1. Chemicals 2. Preparation of supported gold nanoparticles 3. Characterization Figure S1. TEM image and gold size distribution for gold nanoparticles supported on alumina (Au/Al2O3). Table S2. XRD patterns of Al2O3 and Au/Al2O3. Figure S3. XPS spectrum of Au/Al2O3. 4. Fabrication of LED reactor Figure S4. Home-made LED reactor: a) image of the LED reactor, b) top-view diagram of the LED reactor, c) side-view diagram of the LED reactor. 5. Photocatalytic reduction of nitrobenzene Table S1. Influence of the amount of formic acid on reduction of nitrobenzene using formic acid and supported Au catalyst. Figure S5. GC chromatogram of standard samples. Scheme S1. Reduction of nitrobenzene proposed by Haber. Scheme S2. Proposed reaction pathway for reduction of nitrobenzene using formic acid as a hydrogen donor. Scheme S3. Reduction of nitrobenzene using formic acid as a hydrogen donor on the surface of Au/Al2O3. Scheme S4. Proposed reaction pathway for reduction of nitrobenzene using KOH and 2- propanol. Scheme S5. Hydrogen abstraction by gold nanoparticles. Scheme S6. Reduction of nitrobenzene using 2-propanol and KOH on the surface of Au/Al2O3. References S2

3 1. Chemicals The following reagents were used in the preparation of gold nanoparticles supported on alumina: hydrogen tetrachloroaurate (III) tetrahydrate (HAuCl4 4H2O) and ammonia solution (NH3, 25%) were obtained from Wako Pure Chemical Industries, Ltd.; high purity alumina (γ- Al2O3) type: AKP-G015 was purchased from Sumitomo Chemical Co., Ltd. The following reagent, standards, and solvents were used in the experiments: nitrobenzene, aniline, and formic acid were purchased from Wako Pure Chemical Industries, Ltd.; nitrosobenzene and N-phenylhydroxylamine were purchased from Sigma-Aldrich Co. LLC.; azoxybenzene, azobenzene, hydrazobenzene, naphthalene, and formanilide were obtained from Tokyo Chemical Industry Co., Ltd.; potassium hydroxide was obtained from Kanto Chemical Co., Inc.; acetonitrile and 2-propanol were obtained from Kanto Chemical Co., Inc. 2. Preparation of supported gold nanoparticles 1 To a 100-mL pear-shaped evaporating flask were added water (40 ml), HAuCl4 4H2O (0.1 mmol, from a 1-mM in water stock solution), and γ-al2o3 (1.0 g). The solution was stirred at 400 rpm for 2 min and 25% ammonia solution (0.4 ml) was added immediately. The ph of the solution was checked with a ph paper to ensure a ph 10. The flask was sealed with a Parafilm and stirred at 400 rpm at room temperature for 6 h. The solution was then refluxed at 100 C for 30 min. After cooling down, the particles were filtered using no. 4A filter paper (Advantec MFS, Inc.) and the particles and filter paper were heated at 200 C for 4 h in an oven. Finally, the supported gold nanoparticles were allowed to cool, removed from the filter paper, and ground. S3

4 3. Characterization The morphology of Au/Al2O3 was observed by transmission electron microscopy (TEM; Hitachi H-7100) at 100 kv accelerating voltage. The gold nanoparticles were dispersed in deionized water and dropped onto a copper grid, then dried overnight in a vacuumed desiccator. Powder X-ray diffraction (XRD) patterns were obtained with a Rigaku Smartlab X- ray diffractometer using Cu 22 Kα radiation (λ = nm) at 40 kv and 20 ma. Gold content was determined using Shimadzu ICPS-7000 Ver.2 Sequential Plasma Spectrometer. Diffuse reflectance UV-vis spectra were measured using JASCO V-670 UV-vis spectrophotometer equipped with a JASCO ISN-470 integrating sphere system. 1 H NMR spectra were obtained using a Bruker AVANCE III 400 MHz NMR spectrometer. X-ray photoelectron spectroscopy (XPS) was measured on a Shimadzu Kratos AXIS-ULTRA DLD spectrometer using an Al target at 15 kv and 10 ma. The binding energies were calibrated with the C 1s level (285.0 ev) as the internal standard reference. S4

5 mean = 3.9 ± 0.7 nm 70 Counts Au Particle Size (nm) Figure S1. TEM image and gold size distribution for gold nanoparticles supported on alumina (Au/Al2O3). S5

6 Au/Al 2 O 3 Al 2 O 3 Intensity (a.u.) Au RRUFF ID: R (111) (200) (220) (311) Θ (degree) Figure S2. XRD patterns of Al2O3 and Au/Al2O3. S6

7 Au4f 5/2 Au4f 7/2 Intensity (a.u.) Binding Energy (ev) Figure S3. XPS spectrum of Au/Al2O3. S7

8 4. Fabrication of LED reactor The LED reactor (Figure S4) consists of 4 10-watt green LED emitters (LZ4-00G100; LED Engin, Inc.) on each wall of a 10-cm x 10-cm copper block with 2 heat sinks and 2 fans on 2 opposite sides of the block to reduce heat (Figure S4). In addition, an extra fan was used to reduce the heat from the LED emitters. Each emitter produces light intensity of 3.38 x 10 5 lux (measured 2.5 cm from the LED emitter using an LX-1108 light meter; Lutron Electronic Enterprise Co., Ltd.). The spectrum of the emitters was measured using C7473 photonic multichannel spectral analyzer (Hamamatsu Corp.). Temperature of the reaction mixture during the illumination was 23 C, which is ca. 10 C higher than the beginning (15 C). This temperature was achieved during the irradiation at 20 min. The dark experiments were conducted with the Au/Al2O3 while the reactor was wrapped with Al foil under the irradiation, where the temperature of the reactor was 23 C. S8

9 a) D C A C D A E A B A b) G F A.4 10-watt Green LED emitters B.Copper block C.2 Heat sinks D.2 Fans E.Reaction tube F. Controller G.Plug to power source D C B B C A A. Copper block B.2 Heat sinks C.2 Fans D.Reaction tube c) Figure S4. Home-made LED reactor: a) image of the LED reactor, b) top-view diagram of the LED reactor, c) side-view diagram of the LED reactor. S9

10 5. Photocatalytic reduction of nitrobenzene To a 100-mL reaction tube were added Au/Al2O3 (50 mg), nitrobenzene (1 mmol, 103 µl), naphthalene (0.5 mmol, 64 mg, an internal standard), and either formic acid (3.5 mmol, 132 µl) and acetonitrile (40 ml) (Method A) or KOH (3 ml of 0.1 M in 2-propanol) and 2- propanol (37 ml) (Method B) (See Scheme 1 in the main article). The mixture was flushed with 20-mL/min argon for 10 min and stirred at 500 rpm for the specified time under either green LED or wrapped with aluminum foil (for dark condition) in water bath at the specified temperature. After the specified time, 1-mL of the solution was filtered using a Millipore Millex LG filter unit (0.20 µm, 13 mm) to remove the catalyst. The filtered solution was analyzed using a Shimadzu GC-2014 equipped with Agilent DB-1 column (length: 50 m, diameter: 0.32 nm, film thickness: 0.25 µm). The GC chromatogram is shown in Figure S5. To recover the catalyst after the reaction for characterization, the reaction mixture was poured into a 50-mL centrifuge tube and centrifuged at 4,000 rpm for 6 min. The solution was decanted off and 30-mL of solvent was added to the wash the remaining catalyst by shaking the tube vigorously. The mixture was centrifuged again and the washing process was repeated twice more. The remaining catalyst was air-dried overnight and used for further analysis. S10

11 Table S1. Influence of the amount of formic acid on reduction of nitrobenzene using formic acid and supported Au catalyst a Entry Formic Acid (mmol) Conv. (%) b A Yield (%) b B Yield (%) b C Yield (%) b D Yield (%) b E Yield (%) b c a Reaction condition: 1 mmol of nitrobenzene, 50 mg of catalyst, 5 ml of acetonitrile, 80 C, 2 h, under 10 ml/min argon flow. b Determined by GC using naphthalene as an internal standard. c 4 h reaction time. S11

12 Figure S5. GC chromatogram of standard samples. Note: formanilide s retention time was min under the same condition.* *GC Chromatogram was obtained by using following conditions. GC: Shimadzu GC Column: Agilent DB-1; Length: 50 m; Diameter: 0.32 mm; Film thickness: 0.25 µm Injection port temperature: 280 C; FID detector temperature: 280 C. Temperature program: 20 C/min 60 C to 200 C, 10 C/min 200 C to 280 C (15 min total). S12

13 Scheme S1. Reduction of nitrobenzene proposed by Leipzig. 2 S13

14 Scheme S2. Proposed reaction pathway for reduction of nitrobenzene using formic acid as a hydrogen donor. S14

15 Scheme S3. Reduction of nitrobenzene using formic acid as a hydrogen donor on the surface of Au/Al2O3. S15

16 Scheme S4. Proposed reaction pathway for reduction of nitrobenzene using KOH and 2- propanol. Scheme S5. Hydrogen abstraction by gold nanoparticles. S16

17 Scheme S6. Reduction of nitrobenzene using 2-propanol and KOH on the surface of Au/Al2O3. S17

18 References: (1) Gupta, N. K.; Nishimura, S.; Takagaki, A.; Ebitani, K. Green Chem. 2011, 13, (2) (a) Leipzig, B. Z. Elektrochem. 1898, 4, (b) Blaser, H.-U. Science 2006, 313, S18