A General Synthesis of Discrete Mesoporous Carbon Microspheres through a Confined Self- Assembly Process in Inverse Opals Zhenkun Sun,, Yong Liu, Bin Li, Jing Wei, Minghong Wang, Qin Yue, Yonghui Deng, Serge Kaliaguine, Dongyuan Zhao * Shanghai Key Laboratory of Molecular Catalysis and InnovativeMaterials, Department of Chemistry and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (P. R. China). Département de Génie Chimique, Faculté des Sciences et de Génie, Université Laval, 1065 Avenue de la Médecine, Québec (Québec), Canada G1V 0A6 dyzhao@fudan.edu.cn 1
Experimental Section Chemicals Polyvinylpyrrolidone (PVP, Mw = 30000) was purchased from Aldrich and used as received. Ammonium peroxodisulphate (APS), styrene (St), ethanol, concentrated HCl, phenol, NaOH, formalin solution (37 wt % formaldehyde), Co(NO 3 ) 2 6H 2 O and tetraethyl orthosilicate (TEOS) were purchased from Shanghai Chem. Corp. The polymerization inhibitor was removed from the styrene by infiltration through Al 2 O 3 column. Distilled water was used in this study. Preparation of resol precursor For a typical preparation, 10.0 g (106 mmol) of phenol was melted at 40-42 C, then 2.13 g of 20 wt % NaOH (10.7 mmol) aqueous solution was added slowly under stirring. After 10 min, 17.7 g (218 mmol) of formalin solution (37 wt % formaldehyde) was added dropwise, and the reaction mixture was stirred at 70 C for 60 min. Upon cooling the mixture to room temperature, the ph value was adjusted to about 6.0 by using 2.0 M HCl solution. Water was then removed under vacuum below 50 C. The resol precursors were redissolved in ethanol (20 wt % ethanolic solution); thereby separating sodium chloride as a precipitate at the same time. Preparation of Polystyrene Colloidal Crystals Monodisperse polystyrene (PS) microspheres with a mean size of ~ 1.1 µm were prepared through a dispersion polymerization approach. For a typical preparation, 8.0 g of styrene, 0.06 g of PVP, 12 ml of H 2 O and 0.15 g of APS were dissolved in ethanol (100 ml). The obtained solution was then added into a 250 ml Three-neck round bottom flask with a 2
magnetic stirrer, a refluxing condenser, and a nitrogen inlet. After sealing in a nitrogen atmosphere, the reactor was submerged in a water bath and the polymerization was carried out at 70 C for 15 h. Then, the obtained PS microspheres were washed by ethanol for 4 times and re-dispersed in water with the weight concentration of 2.5 %. The PS dispersed solution was obtained and placed in oven at 40 C for several days until the water was evaporated completely. Finally, the monolithic PS colloidal crystals were obtained. Protein Adsorption Three protein solutions were prepared in buffer solution and used for the adsorption test, including BSA (in NH 4 Ac/HAc buffer, ph = 4.8), Cyt.c (in NaOH/NaHCO 3 buffer, ph = 10.1) solution, and mixed solution of BSA and Cyt.c (in NaOH/NaHCO 3 buffer, ph = 9.4). Firstly, 0.020 g of the Co-MC-MS sample was added to 20 ml of BSA (100 mg/l) or Cyt.c aqueous solution (100 mg/l) respectively. Then the mixed solution was vibrated at room temperature for 5 h and subjected to separation by hand-held magnet. Supernatant was subjected for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and UV-Vis spectrum measurements. The UV characteristic absorption peak was selected at 280 nm for BSA and 409 nm for Cyt.c respectively. Standard curves were drawn by measuring a series of BSA or Cyt.c aqueous solutions with concentrations of 20 to 100 mg/l. Secondly, 0.020 g of the Co-MC-MS sample was added to an aqueous solution containing 10 ml of BSA (100 mg/l) and 10 ml of Cyt.c solution (100 mg/l) respectively. Then, the mixed solution was vibrated at room temperature for 5 h. After that, the solution with Co-MC-MSs particles was subjected to separation by 3
hand-held magnet, and the supernatant was also subjected to analysis by SDS-PAGE and UV-Vis spectrum measurements. SDS-PAGE was carried out on a vertical polyacrylamide gel system at a constant voltage of 60 V until the protein bands reached the interface between stacking and separating gels. Separation was performed at a constant voltage of 120 V. The electrophoresis was stopped when the tracker dye was ca. 1 cm above the end of the glass plates. Peroxidase activities of Cyt.c and desorbed Cyt.c The assay mixture containing 10 mm of potassium phosphate buffer (ph 7.4), 50 µm of ABTS, 0.15 mm of hydrogen peroxide and 4 µm of Cyt.c (before adsorption) in a total volume of 2 ml. The reaction was initiated by addition of hydrogen peroxide and the increase in UV absorbance at 415 nm was measured by a UV/Vis spectrophotometer. For the activity measurements of desorbed proteins, 0.010 g of the Co-MC-MS sample was added to an aqueous solution containing 30 ml of Cyt.c solution (150 mg/l). After 5 h shaking, the sorbent Co-MC-MS was separated from the solution and subjected to 2 times quick washing by water. Then this sorbent was re-dispersed in 5 ml of potassium phosphate buffer (ph 7.4) for the desorption process. After 4 h, the sample Co-MC- MS was separated and the resultant solution with desorbed protein was obtained. The amount of the desorbed Cyt.c was ~ 11.7 % corresponding to the adsorbed protein measured by UV/Vis spectrophotometer at 409 nm. Then the peroxidase activity of the desorbed Cyt.c was also measured using the same method as mentioned above. 4
Figure S1. SEM images of different stages during the fabrication of the silica inverse opal monolith: (a) The SEM image of the monolithic opal structured PS microspheres and (a inset) their optical photo, (b) SEM image of the monolithic PS microspheres after the impregnation with ethanolic silicate solution and its magnified SEM image. (c, d) SEM images of the obtained silica inverse opals in different magnification. 5
Figure S2. N 2 adsorption-desorption isotherms (a) and the corresponding pore size distribution (b), SAXS pattern (c) and low magnification SEM image (d) of the mesoporous carbon microspheres synthesized at the weight ratio of F127: resol: ethanol of 1: 1: 14. 6
Figure S3. The TEM (top) and SEM (bottom) images of the mesoporous carbon microspheres prepared by using the silica inverse opal derived from the PS microspheres with a diameter of ~ 1.6 µm. 7
Figure S4. SEM images at different magnification of the mesoporous carbon microspheres MC-MS-2 (a, b) with a body-centered cubic (space group Im3m) mesostructure and mesoporous carbon microspheres MC-MS-3 (c, d) with high porousity mesostructure. TEM images of the samples MC-MS-2 (e and inset) and MC-MS-3 (f). N2 sorption-desorption isotherms (g, h) and pore size distribution curves (inset) of the samples MC-MS-2 (g and inset) and MC-MS-3 (h and inset), respectively. Insets in Fig. S4a and S4b are their corresponding SAXS patterns. 8
Figure S5. SEM images (a, b, c) and TEM image (c) of the mesoporous carbon microspheres prepared by using the silica inverse opals with macropores of ~ 330 nm after the ultrasonic treatment for 5 h. 9
Figure S6. N 2 adsorption-desorption isotherms (a) and SAXS pattern (b) of the mesoporous carbon microspheres prepared by using the silica inverse opals with macropores of ~ 330 nm. The inset (a) is the corresponding pore size distribution curve. 10
Figure S7. SEM image (a) and N 2 adsorption-desorption isotherms (b) of the Cobased nanoparticles containing mesoporous carbon microspheres. The inset in (b) is the corresponding pore size distribution curve. 11
Figure S8. The TGA curve (left) and wide-angle X-ray diffraction pattern (right) of the Co-based nanoparticles contained mesoporous carbon microspheres. 12
Figure S9. Scanning transmission electron microscopy (STEM) image (a) and elements mapping for C (b), O (c), and Co (d) of the Co-based nanoparticles contained mesoporous carbon microspheres. 13
Figure S10. A dye solution (Left image, containing Rodinmine B of 10-5 M) was added with 1.0 mg of the Co-based nanoparticles containing mesoporous carbon microspheres Co-MC-MS (Middle image) as a sorbent. After 30 seconds, a magnet was applied to the solution. Five minutes later, the sorbent could be effectively separated (Right image). The addition of dye is for visually observe the adsorption ability of Co-MC-MS sample. 14
Figure S11. Structural models (a) of the proteins BSA and Cyt.c; UV-Vis spectra (b - d) of the solutions containing (b) both BSA and Cyt.c, (c) Cyt.c and (d) BSA before and after the adsorption by the Co-based nanoparticles containing mesoporous carbon microspheres. Due to the similar concentration of BSA in its aqueous solution, the UV-Vis spectra curves (black and red line) in Figure S11d are overlapping. 15
Figure S12. The UV absorbance at 415 nm of the solution containing ABTS as a substrate functioned with the reaction time catalyzed by cytochrome c, showing enzymatic activity of cytochrome c before adsorption on the mesoporous carbon microspheres Co-MC-MS (black line) and after desorption from the sample Co-MC-MS (red line). In the control test, all the condition was same besides the addition of Cyt.c. 16