Formation of Free-Standing Inverse Opals with Gradient Pores
1
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
2
Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(10), 1923; https://doi.org/10.3390/nano10101923
Received: 25 August 2020
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Revised: 21 September 2020
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Accepted: 21 September 2020
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Published: 26 September 2020
(This article belongs to the Special Issue Advances in Electrochemical Fabrication of Nanoporous Materials)
We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.
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Keywords:
colloidal crystals; inverse opals; gradient pores; electrophoresis; self-assembly; mechanical properties
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MDPI and ACS Style
Hung, P.-S.; Liao, C.-H.; Huang, B.-H.; Chung, W.-A.; Chang, S.-Y.; Wu, P.-W. Formation of Free-Standing Inverse Opals with Gradient Pores. Nanomaterials 2020, 10, 1923. https://doi.org/10.3390/nano10101923
AMA Style
Hung P-S, Liao C-H, Huang B-H, Chung W-A, Chang S-Y, Wu P-W. Formation of Free-Standing Inverse Opals with Gradient Pores. Nanomaterials. 2020; 10(10):1923. https://doi.org/10.3390/nano10101923
Chicago/Turabian StyleHung, Pei-Sung, Chen-Hong Liao, Bo-Han Huang, Wei-An Chung, Shou-Yi Chang, and Pu-Wei Wu. 2020. "Formation of Free-Standing Inverse Opals with Gradient Pores" Nanomaterials 10, no. 10: 1923. https://doi.org/10.3390/nano10101923
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