Hollow Capsules of Reduced Graphene Oxide Nanosheets ...
Supporting Information
Hollow Capsules of Reduced Graphene Oxide Nanosheets Assembled on a Sacrificial Colloidal Particle Jinkee Hong, Kookheon Char,* and Byeong-Su Kim*
Experimental Materials. Graphite oxide was synthesized from graphite powder (45 micron, SigmaAldrich) by modified Hummers method and reduced according to the previous report. Negatively and positively charged GO suspensions were reduced by hydrazine solution (35 wt% in water, Aldrich). As-prepared negatively charged GO suspension (5.0 mL) was mixed with 5.0 μL of hydrazine solution and 35.0 μL of ammonia solution (28-30%, Samchun) in a 20-mL glass vial. After stirred for a few minutes, the vial was put in a water bath at 95 oC for 1 h. The reduction of positively charged GO suspension was identically carried out without mixing of the ammonia solution. The positively charged Au-NPs were synthesized as reported previously. PS colloids with a diameter of 2.0 m were purchased from Microparticles GmbH.
S1
Preparation of rGO Multilayers on PS Colloids. The concentration of rGO solutions used in all the deposition experiments was fixed at 0.10 wt%. The (rGO-NH3+/rGO-COO-)n multilayer-coated polystyrene colloids were prepared as follows: 100 L of a concentrated dispersion (6.4 wt%) of negatively charged polystyrene colloids was diluted to 0.50 mL with deionized water. Subsequently, 0.50 mL of rGO-NH3+ (pH 6) was added. After deposition for 10 min with a gentle vortex, the excess rGO-NH3+ were removed by three centrifugation (8,000 rpm at 4 oC for 5 min)/wash cycles. A suspension of rGO-COO- (pH 6) was then allowed to deposit on the rGO-NH3+-coated PS colloids under the same conditions. The above process was repeated until 3 bilayers of (rGO-NH3+/rGO-COO-)3 have been deposited onto PS colloids. In order to incorporate Au-NPs into the (rGO-NH3+/rGO-COO-) multilayers, the LbL sequence of preparing multilayer film was modified to (rGO-NH3+/rGO-COO-/AuNPs/rGO-COO-)n tetralayer combination.
Characterizations. Zeta-potential measurements were measured by electrophoretic light scattering spectrophotometer (ELS-8000). The morphologies of the reduced graphene oxide capsules were examined by Field-Emission SEM (JEOL JSM-7401F) and Energy-Filtering Transmission Electron Microscope (Carl Zeiss-LIBRA 120).
S2
Figure S1. SEM images of (rGO-NH3+/rGO-COO-)n multilayer films on PS colloidal particles as a function of bilayer (n): (a), (b) n = 1, (c) n = 2, (d) n = 3, (e) n = 4, and (f) n = 5
S3
Figure S2. (a-e) TEM images of hollow graphene capsule films after removing the sacrificial PS colloidal particles as a function of bilayer: (rGO-NH3+/rGO-COO-)n (a) n = 3, (b, c) n = 5 and (rGO-NH3+/rGO-COO-/Au-NPs/rGO-COO-)n (d) n = 2 and (e) n = 3. (f) TEM image of Au-NPs/rGO-COO- nanocomposite sheet detached after the removal of PS template.
S4
Figure S3. TEM images of hollow graphene capsule films after removing the sacrificial PS colloidal particles as a function of bilayer: (rGO-NH3+/rGO-COO-)n: (a) n = 0.5, (b) n = 1.
S5
Hollow Capsules of Reduced Graphene Oxide Nanosheets Assembled on a Sacrificial Colloidal Particle Jinkee Hong, Kookheon Char,* and Byeong-Su Kim*
Experimental Materials. Graphite oxide was synthesized from graphite powder (45 micron, SigmaAldrich) by modified Hummers method and reduced according to the previous report. Negatively and positively charged GO suspensions were reduced by hydrazine solution (35 wt% in water, Aldrich). As-prepared negatively charged GO suspension (5.0 mL) was mixed with 5.0 μL of hydrazine solution and 35.0 μL of ammonia solution (28-30%, Samchun) in a 20-mL glass vial. After stirred for a few minutes, the vial was put in a water bath at 95 oC for 1 h. The reduction of positively charged GO suspension was identically carried out without mixing of the ammonia solution. The positively charged Au-NPs were synthesized as reported previously. PS colloids with a diameter of 2.0 m were purchased from Microparticles GmbH.
S1
Preparation of rGO Multilayers on PS Colloids. The concentration of rGO solutions used in all the deposition experiments was fixed at 0.10 wt%. The (rGO-NH3+/rGO-COO-)n multilayer-coated polystyrene colloids were prepared as follows: 100 L of a concentrated dispersion (6.4 wt%) of negatively charged polystyrene colloids was diluted to 0.50 mL with deionized water. Subsequently, 0.50 mL of rGO-NH3+ (pH 6) was added. After deposition for 10 min with a gentle vortex, the excess rGO-NH3+ were removed by three centrifugation (8,000 rpm at 4 oC for 5 min)/wash cycles. A suspension of rGO-COO- (pH 6) was then allowed to deposit on the rGO-NH3+-coated PS colloids under the same conditions. The above process was repeated until 3 bilayers of (rGO-NH3+/rGO-COO-)3 have been deposited onto PS colloids. In order to incorporate Au-NPs into the (rGO-NH3+/rGO-COO-) multilayers, the LbL sequence of preparing multilayer film was modified to (rGO-NH3+/rGO-COO-/AuNPs/rGO-COO-)n tetralayer combination.
Characterizations. Zeta-potential measurements were measured by electrophoretic light scattering spectrophotometer (ELS-8000). The morphologies of the reduced graphene oxide capsules were examined by Field-Emission SEM (JEOL JSM-7401F) and Energy-Filtering Transmission Electron Microscope (Carl Zeiss-LIBRA 120).
S2
Figure S1. SEM images of (rGO-NH3+/rGO-COO-)n multilayer films on PS colloidal particles as a function of bilayer (n): (a), (b) n = 1, (c) n = 2, (d) n = 3, (e) n = 4, and (f) n = 5
S3
Figure S2. (a-e) TEM images of hollow graphene capsule films after removing the sacrificial PS colloidal particles as a function of bilayer: (rGO-NH3+/rGO-COO-)n (a) n = 3, (b, c) n = 5 and (rGO-NH3+/rGO-COO-/Au-NPs/rGO-COO-)n (d) n = 2 and (e) n = 3. (f) TEM image of Au-NPs/rGO-COO- nanocomposite sheet detached after the removal of PS template.
S4
Figure S3. TEM images of hollow graphene capsule films after removing the sacrificial PS colloidal particles as a function of bilayer: (rGO-NH3+/rGO-COO-)n: (a) n = 0.5, (b) n = 1.
S5
