Supporting Information

A visible light-driven plasmonic photocatalyst

Francesca Pincella,a,b Katsuhiro Isozaki,a,c* and Kazushi Mikia,b*

aPolymer Materials Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki

305-0044, Japan, and bDepartment of Pure and Applied Sciences, University of Tsukuba, 1-1-1

Tennodai, Tsukuba, Ibaraki 305-8571, JapancCurrent address: International Research Center for Elements Science, Institute for Chemical

Research, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan

E-mail: kisozaki@scl.kyoto-u.ac.jp, MIKI.Kazushi@nims.go.jp

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Figure S1. Extinction spectra of 36 nm citrate capped AuNPs in water solution (red line) and 2D array of 36 nm AuNPs capped with hexanethiol: dodecanethiol on MPTMS-Hexdt functionalized ITO substrate (blue line).

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Figure S2. a) TEM micrograph of titania nanocrystals on copper grids, b) plot of (αhν)2

versus hν for a titania nanocrystals film, c) Raman spectrum of titania nanocrystals film, each phonon peak identified belongs to anatase titania, d) XRD spectrum of titania nanocrystals powder, red square: titania anatase peaks, green triangles: titania rutile peaks.

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Figure S3. Extinction spectra of AuNPs 2D array without (a) and with (b) TMOS layer. Blue line: 2D array, red line: titania on 2D array, magenta line: sample after 30 s sonication in DI water, green line: sample after 1 min sonication in DI water, black line: sample after 3 min sonication.

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Figure S4. Contact angle before (a) and after (b) titania nanocrystals deposition.

Figure S5. a) AFM image and b) SEM micrograph of 2D array of 36 nm AuNPs coated with titania nanocrystals, inset: higher magnification.

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Figure S6. SAXS patterns of 2D array of 30 nm AuNPs before (blue line) and after (red line) functionalization with TMOS and deposition of titania nanocrystals.

Figure S7. Plots of difference absorbance (ΔA) spectra (spectrum after irradiation is subtracted from initial spectrum) obtained after MB photocatalytic degradation on titania coated 2D array with 700 nm light irradiation (excitation λ = 700 nm, FWHM = 10 nm) for different amounts of time: delta absorbance increases from 1 min irradiation (blue line) to 15 min irradiation (brown line). Spectra were acquired at 1 min intervals from 1 min to 8 min and then after 10 and 15 min of irradiation.

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Figure S8. Action spectra of photocatalytic degradation rate per unit power versus excitation wavelength (λ = 480, 560, 700, 830 nm). Comparison of photocatalytic degradation rate (k) with absorbance spectrum of MB (dotted line) and extinction spectrum of titania coated 2D array (green line).

Figure S9. MB photocatalytic degradation under solar illumination. The photocatalytic degradation experiment was performed with titania coated ITO substrate (circles in the figure) and titania coated 2D array (triangles in the figure). Inset: pseudo first-order kinetics of initial reaction steps for titania coated 2D array and titania sample.

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Preparation of control samples for photocatalytic degradation of methylene blue

A quartz sample coated with titania nanocrystals was prepared by immersing an ITO substrate in a 5% v/v 3-mercaptopropyltrimethoxysilane solution in methanol overnight and then rinsing with methanol three times. This produced a silane terminated substrate, analogous to the terminal group of the TMOS coated 2D array. The MPTMS functionalized substrate was then immersed in the titania nanocrystals solution at 37 °C overnight, rinsed in DI water and annealed at 90 °C for 12 h.The quartz reference sample was prepared by immersing the quartz substrate in piranha solution (H2SO4 30%: H2O2 = 2:1 v/v; handle with care: piranha solution is highly corrosive and reacts violently with organic matter). The AuNPs 2D array reference sample was prepared following the same procedure reported in the manuscript.

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