Preparation of Large-area, Crack-free Polysilazane-based Photonic. Crystals

Transcription

1 Supporting Information Preparation of Large-area, Crack-free Polysilazane-based Photonic Crystals Zongbo Zhang a,c, Weizhi Shen a,c, Changqing Ye a,c, Yongming Luo a, Shuhong Li b, Mingzhu Li a,*, Caihong Xu a,*, Yanlin Song a a Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, , China b Beijing Technology and Business University, Beijing , China c Graduate University of Chinese Academy of Sciences, Beijing, , China Fax/Tel: (+86) caihong@iccas.ac.cn and mingzhu@iccas.ac.cn Experimental section Methods Fabrication of the opal template Mono-dispersed latex spheres of poly(styrene methyl methacrylate acrylic acid) were synthesized via batch emulsion polymerization. The photonic crystals (PCs) were fabricated via the vertical deposition method on glass slides. Prior to use, all glass slides and vials were soaked overnight in a chromic-sulfuric acid cleaning solution, rinsed with ultra-pure water, and dried in a stream of nitrogen. The glass slides were fixed vertically into the poly(st MMA AA) latex sphere suspensions (ca. 0.15%), and maintained for 2 3 days at 60 C with the humidity of 60%. Then, the dry poly(st MMA AA) colloidal films were obtained. Reference: J. Wang, Y. Wen, H. Ge, Z. Sun, Y. Zheng, Y. Song, L. Jiang. Macromol. Chem, Phys., 2006, 207, 596. Fabrication of the inverse opal HPSZ A 10wt% solution of the PSZ (yellow liquid, M n : 900) in hexane was used in this work. In the infiltrating process, firstly the template (10mm 25mm) on glass substrate was dried at 80 o C for 2 h in vacuum. After being dripped with PSZ solution in a dried culture dish, the template was then keep at room temperature for 4 h for full infiltration of the solution and evaporation of the solvent. The drippings were repeated once every 4 h. The template-psz composite in a quartz boat was then placed in a quartz tube furnace and heated S1

2 to 120 o C at a heating rate of 2 o C min -1 under dry Ar atmosphere and kept for 1 h, and then heated to 170 o C for 1 h to yield the cured composite. The cured sample was further heated at 0.5 o C min -1 to 500 o C and held for 2 h to remove the template and convert the PSZ to hybrid material. Finally, the sample was cooled down to room temperature at a rate of 1 o C min -1, and the centimeter-scale inverse opal hybrid SiCN pieces peeled off from the glass substrate. Different heating rates, including 0.5, 1, 3, 5 and 10 o C /min was adopted for pyrolysis process to optimize experiment condition. Characterization SEM images were taken on a JEOL S4800 or S4300 with an accelerating voltage of 15kV. Optical reflectance spectra were recorded with an Ocean Optic HR 4000 CG fiber optic UV-Vis-IR spectrometer. Complex viscosity was obtained using a TA AR 2000 Rheometer with a 20-mm diameter parallel plate at a heating rate of 4 o C/min. TGA measurement was performed on SII EXSTAR 6300 TG/DTA instrument. Nanoindentation experiments were carried on a MTS Nano Indenter XP with a diamond indentation tip. FT-IR spectra were obtained from a Bruker Tensor-27 FTIR spectrometer in the wavenumber range of cm -1. Thermal Mechanical Analysis (TMA) was run on a SII EXSTAR 6000 TMA instrument. XRD measurements were carried out on a Rigaku D/M4X 2500 diffractiometer with Cu-Kα radiation. Calculations For a typical fcc arrangement, the filling fraction can be calculated according to the following equation. f 4 Ras =1-3 2D 3 Where f is the filling fraction of solid material, here HPSZ, R as is the diameter of air spheres, and D is the distance between the centers of the nearest-neighbor air spheres. Here, as estimated from SEM images of I-HPSZ 1, R as =200 nm and D=260 nm. Thus, the filling fraction of I-HPSZ 1 is calculated as For HPSZ 2, R as =230 nm and D=270 nm, the filling fraction of I-HPSZ 2 is S2

3 calculated as The maximum reflectance wavelength was calculated using the following equations. =2d111neff n = fn +(1- f) n eff s i d111 = 2/3D where is the maximum wavelength of reflectance, d 111 is the lattice spacing, n eff is the effective RI of the inverse opal PC, n s is the RI of the solid material, here HPSZ, n i is the RI of solvent in air spheres (when no solvent in, is the RI of air), and D is the distance between centers of the nearest-neighbor air spheres. For I-HPSZ 1, f=0.66, n i =1, D=260 nm, the measured λ=800 nm, therefore, the n s is calculated as For I-HPSZ 2, f=0.51, n s =2.21, n i =1, D=270 nm, therefore, the calculated λ=755 nm, which was well close to the experimental result of 745 nm. Figure S1. Enlarged SEM image of the low-magnification I-HPSZ in Fig. 1b. S3

4 Figure S2. Optical images for samples (a) opal template, (b) opal template infiltrated with 10wt% PSZ solution for two days, (c) the infiltrated opal template heated at 60 o C for 1h, and (d) the infiltrated opal template heated at 120 o C for 1h, the magnification for all images is 400. We can find that the opal template is full of microcracks and different colors such as yellow and black exist in the large-region green color, which indicates the cracks do disorder the optical property of polymer photonic crystals (a). After infiltrated with 10wt% PSZ for two days, the opal template still shows cracks (b). However, the distance between cracks is widened. After heated at 60 o C for 1h, microcracks are not observed and larger uniform area shows (c). For infiltrated sample treated at 120 o C for 1h, a very smooth and uniform surface was obtained (d). Figure S3. SEM images of I-HPSZs with heating rate of (a) 1 o C /min, (b) 3 o C /min, (d) 5 o C /min, and (d) 10 o C /min. S4

5 Figure S4. SEM images of I-HPSZs obtained at different pyrolyzing temperature (a) 600 o C, (b) 700 o C, and (c) 800 o C. Figure S5. FT-IR spectrum of HPSZ obtained at 500 o C under Ar atmosphere. The HPSZ is composed of inorganic skeleton of Si-N and organic side groups as Si-CH 3. The inorganic skeleton will sustain much higher temperature than the organic polymer, which contains C-C backbone. Meanwhile, the organic side groups will endow the material properties over ceramics, such as toughness. Reference: E. Kroke, Y. L. Li, C. Konetschny, E. Lecomte, C. Fasel, R. Riedel, Mater. Sci. Eng., 2000, 26, 97. S5

6 Figure S6. X-ray diffraction patterns of HPSZ hybrid. There is only one broad peak in the spectrum, indicating an amorphous state of the material. If crystalline phases form, the crystalline particles in the material will grow at certain orientation. This will induce inner strain and destroy the original structure. Figure S7. Photograph of (a) I-HPSZ 1 and (b) bulk HPSZ. S6

7 Figure S8. Raman spectra of HPSZ pyrolyzed at 500 o C. Peaks located at around 1300 cm -1 and 1600 cm -1 belonging to free carbon are not observed from the spectrum, indicating this pyrolyzing condition will not produce free carbon and the black color of the HPSZ is derived from the organic side groups. Figure S9. The normalized reflectance spectra of I-HPSZ 1 in air and immersed in different solvents. On the basis of the theoretical formula for calculating the maximum reflectance wavelength provided above. =2d111neff n = fn +(1- f) n eff s i S7

8 d111 = 2/3D where is the maximum wavelength of reflectance, d 111 is the lattice spacing, n eff is the effective RI of the inverse opal PC, n s is the RI of the solid material, here HPSZ, n i is the RI of solvent in air spheres (when no solvent in, is the RI of air), and D is the distance between centers of the nearest-neighbor air spheres. We calculated the maximum reflectance wavelength for different solvents as follows: For I-HPSZ 1 immersed in ethanol, f=0.66, n s =2.21, n i =1.36, D=260 nm, therefore, the calculated λ=835 nm. For I-HPSZ 1 immersed in chloroform, f=0.66, n s =2.21, n i =1.45, D=260 nm, therefore, the calculated λ=843 nm. The measured maximum reflectance wavelength for I-HPSZ 1 and I-HPSZ 2 was 857 nm and 865 nm, respectively. Therefore, about 20 nm deviation between the calculated and experimental results for both I-HPSZ 1 and I-HPSZ 2 was found. Figure S10. (a) Reflectance spectra of I-QSiCN 1 after treated at different temperature in air. (b) TG curves of QSiCN in both N 2 and air, inset in (b) is the SEM image of I-QSiCN 1 treated at 500 o C in air, the scale bar=500 nm. The samples annealed at 100, 200, and 300 o C show similar reflectance spectra with their maximum peaks at 800 nm. Then, the reflectance peak slightly shifts to shorter wavelength for the sample treated at 400 o C. After annealed at 500 o C, an obvious blue-shift is observed and the maximum peak arrives at 755nm, while the diameter of air spheres still holds (Figure S9b inset). TGA analyses (Figure 5b) indicate the good thermal stability of QSiCN in N 2 and no weight change is found until 560 o C. But in air condition, a weight gain is observed above 300 o C, due to oxidation of sample surface, which lowers the RI of QSiCN. S8