Supporting information

Transcription

1 Supporting information Thermo-responsive coatings on hollow particles with mesoporous shells serve as stimuliresponsive gates to species encapsulation and release. Yang Su 1, Olakunle Francis Ojo 1, Igor Kevin Mkam Tsengam 1, Jibao He 2, Gary L. McPherson 3, Vijay T. John 1 *, Julia A. Valla 4 1. Department of Chemical & Biomolecular Engineering, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana 70118, United States 2. Coordinated Instrumentation Facility, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana 70118, United States 3. Department of Chemistry, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana 70118, United States 4. Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, CT 06269, United States To whom correspondence may be addressed *Vijay T. John vj@tulane.edu Number of Pages (Including Cover): 6 Number of Figures: 3 S1

2 S1. Barret Joyner Halenda (BJH) pore size distribution calculation of mesoporous hollow silica particles. The mesopore size distribution was calculated using the Barret Joyner Halenda (BJH) method 1 with Jaroniec and coworkers modified equation for the statistical film thickness 2 as the following: 2 V L 0 0 RT ln[( p0 / p)] r( p / p ) t( p / p ) 0.3nm (Eq. S1) where t (p/p 0 ) is the statistical film thickness, t( p / p0) 0.1[ ] log( p / p ) (Eq. S2) V L is the molar volume of the liquid adsorbate, is its surface tension, R is the universal gas constant, and T is the absolute temperature. Figure S1 shows the BJH pore size distribution curve of the mesoporous silica hollow particles, indicating an average pore size of 2.5 nm. S2

3 Pore volume (cm 3 /g) Pore diameter Figure S1. BJH pore size distribution of the as-synthesized mesoporous hollow silica particles. S3

4 S2. Thermogravimetric analysis of the mesoporous hollow silica particles with poly (Nisopropyl acrylamide) (PNIPAM) shell (mesohp-pnipam). We used thermogravimetric analysis (TGA) to characterize the composite particles and the data is shown below. The instrument we used was a TA Instruments Q500, with a temperature range from 30 o C to 700 o C and a ramp rate of 2 o C/min. Experiments were done in air and we used lyophilized particles. As the Figure S2 shows, the initial weight loss is due to the loss of adsorbed water and surface hydroxyls (at higher temperatures). We see a second weight loss of about 18.2 wt% occurring around 340 o C, corresponding to the decomposition of PNIPAM. 3 Figure S2. Thermogravimetric analysis of mesoporous silica hollow particles with PNIPAM coating (mesohp-pnipam). S4

5 S3. The pore orientation of the mesoporous silica hollow particles. The high resolution TEM shown in Figure S3 indicates the mesopores appear to be perpendicular to the particle surface, although some of the mesopore channels could be bent because the mesopores are generated in the curved thin shell. Such a pore morphology has been noticed in the work by Yoon et al. 4 Figure S3. High magnification TEM images of mesoporous silica hollow particle. The scale bar is 50 nm. S5

6 References 1. Barrett, E. P. J., L. G.; Halenda, P. P., The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms. Journal of the American Chemical Society 1951, 73, Kruk, M.; Jaroniec, M.; Sayari, A., Application of large pore MCM-41 molecular sieves to improve pore size analysis using nitrogen adsorption measurements. Langmuir 1997, 13 (23), Bauri, K.; Roy, S. G.; Arora, S.; Dey, R. K.; Goswami, A.; Madras, G.; De, P., Thermal degradation kinetics of thermoresponsive poly(n-isopropylacrylamide-co-n,ndimethylacrylamide) copolymers prepared via RAFT polymerization. J Therm Anal Calorim 2013, 111 (1), Yoon, S. B.; Kim, J. Y.; Kim, J. H.; Park, Y. J.; Yoon, K. R.; Park, S. K.; Yu, J. S., Synthesis of monodisperse spherical silica particles with solid core and mesoporous shell: mesopore channels perpendicular to the surface. J Mater Chem 2007, 17 (18), S6