Light-Controlled Shrinkage of Large-Area Gold Nanoparticles Monolayer Film for Tunable SERS Activity

Transcription

1 Light-Controlled Shrinkage of Large-Area Gold Nanoparticles Monolayer Film for Tunable SERS Activity Xuefei Lu a,b, Youju Huang b,c,d, *, Baoqing Liu a,b, Lei Zhang b,c, Liping Song b,c, Jiawei Zhang b,c, Afang Zhang a, and Tao Chen b,c, * a Department of Polymer Materials, College of Materials Science and Engineering, Shanghai University, Nanchen Road 333, Shanghai 00444, China. b Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, 31501, China c University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing , China d Max Planck Institute for Polymer Research, Ackermannweg 10, 5518, Mainz, Germany

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3 Figure S3. SEM images of monolayer films of Au NPs functionalized with acrylamide and photo-initiator (I-959). (A) Before and (B) after being irradiated by UV-light. Figure S4. Schematic illustration of applied forces of Au NPs assembled at the interface: capillary and van der Waals attraction denoted by green arrows, electrostatic and steric repulsion denoted by purple arrows, solvation and line tension denoted by red arrows under UV-light irradiation.

4 Figure S5. TEM images of AuNPs films after irradiation by UV-light used different acrylic monomers: -aminoethyl methacrylate (AEMA), acrylic acid (AAc), -hydroxyethyl methacrylate (HEMA), N-isopropylacrylamide (NIPAM). Figure S6. Elemental evaluation of interfacial cross-linked Au NPs films. (A) HAADF-STEM image and (B-F) EDS (Energy Disperse Spectroscope) elemental mapping of interfacial cross-linked Au NPs films by polyacrylamide after being immersed into the solution of model Raman analyte (4-ATP). Corresponding EDS elemental mapping images: light blue (B), green (C), red (D), orange (E) and yellow (F) colors stand for gold, S, C, N and O element, respectively.

5 Figure S7. (A)The maximum absorption peak of films transferred onto thin PDMS (silicone elastomer : curing agent =10 : 1) substrates versus the time of UV-light irradiation. (B) The statistic maximum absorption peak versus the time of irradiation. The standard deviations are averaged from three individual experiments. Figure S8. Original Raman spectra normalized (divided by max) of cross-linked Au NPs SAMs with gradually increased irradiation time for 0 min (black line), min (red line), 5 min (green line) and 10 min (blue line) by UV-light shown in Figure 7A.

6 Scheme S1. Schematic demonstration of the click reaction of 4-ATP and AAm by thiol ene click chemistry. (1) Figure S9. (A) Raman spectra of cross-linked Au NPs SAMs with gradually increased irradiation time for 0 min (black line), min (red line), 5 min (blue line) and 10 min (magenta line) by UV-light. Raman intensity of probe molecule: 4-methylthiobenzoic acid (4-MBA) of 10-6 M. The exposure time was 10 s, laser wavelength was 785 nm and laser power was 1.4 mw. (B) The plot of SERS intensity from peak 1076 cm 1 and maximum absorption peak versus the time of irradiation. The standard deviations are averaged from ten individual experiments.

7 Figure S10. Optical images of isotropic AuNPs: (A, a) 3 nm and (B, b) 75 nm, and anisotropic Au NRs SAMs: (C, c) 86 nm 3 nm before (A-C) and after (a-c) irradiation by UV-light. The UV-vis spectra of nanoparticles solution (D) and monolayer films transferred onto PDMS after irradiation (E). The scale bar is 3 cm.

8 Figure S11. TEM images of isotropic AuNPs: (A, a) 3 nm and (B, b) 75 nm, and anisotropic Au NRs: (C, c) 86 nm 3 nm after irradiation by UV-light. The scale bars are 00 nm (A-C), 0 nm (a-c). Figure S1. Photograph of the fabrication process of SAMs at the interface as the introduction of absolute ethyl alcohol.

9 Calculation of EFs values for D Au NPs films. For solid 4-ATP sample, since the spot activated by the laser was a circle with diameter of 1.77 µm, and the depth the laser could reach was about 13 µm, according to the density (1.18 g/cm 3 ) and molecular weight (15.19 g/mol) of solid 4-ATP, the number of 4-ATP molecules activated in the bulk solid, N bulk, can be determined as following: N bulk dspot π Dρ = M r,4 ATP 4 ATP N A where d spot is the diameter of circular laser spot, D is the depth of the incident laser beneath the surface of 4-ATP solid, ρ 4-ATP and M r, 4-ATP are the density and molecular weight of 4-ATP, respectively, N A represents the Avogadro constant. The calculated value of N bulk equals to Scheme S. Projection of D SAMs structure. For the 4-ATP molecules adsorbed on the surface of D Au NPs films, assuming that the 4-ATP molecules are adsorbed vertically on Au surface, then the area occupied by one 4-ATP molecule is considered to be equal to the cross-sectional area of the molecule. It has been reported that each 4-ATP molecule occupies ~0.0 nm on the surface of Au. [S1] Therefore, taking into account the D structure (Scheme S1), the ratio between the actual activated area of Au surface and the

10 projected area can be calculated as following: A A actual projected = π 3 R 3R + πr = 1+ 3π = where R represents the pore diameter. Then the number of 4-ATP molecules activated on the surface of the D Au NPs films, N surf, could be calculated as following: N surf dspot 1.91π = 0.0nm where d spot is the diameter of circular laser spot. The calculated value of N surf equals to Then, the Raman scattering intensity at 1076 cm -1 can be used to calculate the EFs by employing the following equation: EF = N N I bulk surf I surf bulk Figure S13. Raman spectrum of 4-ATP power at 785 nm laser. The exposure time was 10s, laser power was 1.4 mw.

11 References [S1] Hong, G.; Li, C.; Limin, Q., Facile Fabrication of Two-Dimensionally Ordered Macroporous Silver Thin Films and Their Application in Molecular Sensing. Adv. Funct. Mater. 010, 0,