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Reproducible and Bendable SERS Substrates with Tailored Wettability Using Block Copolymers and Anodic Aluminum Oxide Templates
(1970-01-01)
Lin, Yu-Liang
;
Karapala, Vamsi Krishna
;
Shen, Ming-Hui
;
Chen, Yi-Fan
;
He, Hung-Chieh
Surface properties are essential for substrates exhibiting high sensitivity in surface-enhanced Raman scattering (SERS) applications. In this work, novel SERS hybrid substrates using polystyrene-block-poly(methyl methacrylate) and anodic aluminum oxide templates is presented. The hybrid substrates not only possess hierarchical porous nanostructures but also exhibit superhydrophilic surface properties with the water contact angle approximate to 0 degrees. Such surfaces play an important role in providing uniform enhanced intensities over large areas (relative standard deviation approximate to 10%); moreover, these substrates are found to be highly sensitive (limit of detection approximate to 10(-12) m for rhodamine 6G (R6G)). The results show that the hybrid SERS substrates can achieve the simultaneous detection of multicomponent mixtures of different target molecules, such as R6G, crystal violet, and methylene blue. Furthermore, the bending experiments show that about 70% of the SERS intensities are maintained after bending from approximate to 30 degrees to 150 degrees.
Laser-Assisted Nanowetting: Selective Fabrication of Polymer/Gold Nanorod Arrays Using Anodic Aluminum Oxide Templates
(1970-01-01)
He, Hung-Chieh
;
Yan, Ai-Ling
;
Karapala, Vamsi Krishna
;
Wang, Shun-Fa
;
Shen, Ming-Hui
1D polymer nanomaterials have attracted significant interest in recent years because of their unique properties and promising applications in various fields. It is, however, still a challenge to fabricate polymer nanoarrays with desired sizes and controlled morphologies. Here, an unprecedented approach, the laser-assisted nanowetting (LAN) method, to selectively fabricate polymer nanoarrays is presented. Polystyrene (PS) is blended with gold nanorods (AuNRs), which are used to absorb the energy from the laser. After the blend films are brought in contact with AAO templates, the AuNRs at regions shone by the laser beams absorb the energy and heat the surrounding polymer chains, resulting in the formation of PS/AuNRs arrays in selected areas. This work paves a new research direction for developing template-based polymer nanomaterials.
Alignment-Improved and Diameter-Reduced Electrospun Polymer Fibers via the Hot-Stretching Process
(1970-01-01)
Hsu, Hsun-Hao
;
Chiu, Yu-Jing
;
Li, Jia-Wei
;
Tseng, Hsiao-Fan
;
Chang, Kai-Chieh
Electrospinning is one of the most facile and versatile techniques to prepare polymer fibers ranging from micrometers to nanometers. Although several parameters can be tuned to control the sizes and morphologies of electrospun fibers, many obstacles are still encountered as the target sizes of the fibers are getting smaller; for example, the sizes of the fibers can be effectively reduced by lowering the polymer solution concentrations but beaded or beads-on-string structures are usually formed. To overcome such obstacles, here a simple technique to prepare alignment-improved and diameter-reduced fibers without bead formation by hot-stretching electrospun fibers at temperatures higher than the glass transition temperatures of the polymers is developed. Polystyrene and poly(methyl methacrylate) are both used in this work as model materials. The relationship between the draw ratio and diameter of the fibers is quantitatively analyzed, demonstrating the control of the fiber diameters. Moreover, higher degrees of alignment improvement at the middle part of the fibers than those at the end part is observed, which results in lower water contact angles at the middle part of the fibers. This work provides a useful post-treatment technique to control the sizes and orientations of electrospun polymer fibers.
Rayleigh-Instability-Induced Transformation for Confined Polystyrene Nanotubes Prepared Using the Solvent-Vapor-Induced Wetting Method
(1970-01-01)
Fang, Zhi-Xuan
;
Chu, Chien-Wei
;
Tsai, Chia-Chan
;
Chang, Chun-Wei
;
Cheng, Ming-Hsiang
Polystyrene (PS) nanotubes prepared using the solvent-vapor-induced wetting method with anodic aluminum oxide templates are for the first time applied to study the thermal stabilities of polymer nanotubes confined in cylindrical geometries. The morphologies of the PS nanotubes and the corresponding transformed PS nanostructures driven by the Rayleigh instabilities after thermal annealing treatments are characterized by scanning electron microscopy. Morphology diagrams of the Rayleigh-instability-induced nanostructures for PS nanotubes prepared via the solvent-vapor-induced wetting method and the solution wetting method are constructed to study the differences in kinetics for samples using different wetting methods. Slower transformation kinetics for the PS samples prepared by the solvent-vapor-induced wetting method than those prepared by the solution wetting method are observed, indicating the better thermal stabilities and the relatively denser packings of the polymer chains in the nanopores for the PS samples prepared using the solvent-vapor-induced wetting method.
Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers
(1970-01-01)
Li, Jia-Wei
;
Chiu, Yu-Jing
;
Chang, Chia-Jui
;
He, Hung-Chieh
;
Tu, Yi-Hsuan
Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI-based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp(2) bonding between carbon atoms.
Hierarchical and Spiral Polymer Structures: Direct Electrospinning on Porous Anodic Aluminum Oxide Templates
(1970-01-01)
Liu, Ying-Hsuan
;
Chiu, Yu-Jing
;
Chen, Jiun-Tai
;
交大名義發表
;
應用化學系
Electrospun fibers with hierarchical structures have attracted a great deal of attention because they have distinct properties, such as large specific surface areas and high surface area-to-volume ratios, and can be applied to various fields. Here, a simple and versatile method is demonstrated to prepare electrospun fibers with hierarchical structures by directly electrospinning poly(methyl methacrylate) (PMMA) solutions on porous anodic aluminum oxide (AAO) templates. Hierarchical PMMA structures with micro- and nanometer scales can be generated. The two length scales of the hierarchical structures can be independently controlled; the first length scale is controlled by the electrospinning conditions, and the second length scale is controlled by the pore sizes of the AAO templates. By adding water in the polymer solutions, the evaporation of the solvents and the whipping instability of the solution jets can be manipulated. Consequently, spiral and hierarchical structures can be obtained. This study opens a promising avenue in fabricating electrospun polymer fibers with hierarchical structures, which should have great potential in a variety of applications, such as filtration, diagnosis, and tissue regeneration.
Effect of Nonsolvent on the Formation of Polymer Nanomaterials in the Nanopores of Anodic Aluminum Oxide Templates
(1970-01-01)
Lee, Chih-Wei
;
Wei, Tzu-Hui
;
Chang, Chun-Wei
;
Chen, Jiun-Tai
;
應用化學系
"We study the effect of nonsolvent on the formation of polymer nanomaterials in the nanopores of porous templates. Water (nonsolvent) is added into a poly (methyl methacrylate) (PMMA) solution in dimethylformamide (DMF) confined in the nanopores of an anodic aluminum oxide (AAO) template. Water forms a wetting layer on the pore wall and causes the PMMA solution to be isolated in the center of the nanopore, resulting in the formation of PMMA nanospheres or nanorods after the solvent is evaporated. The formation of the polymer nanomaterials induced by nonsolvent is found to be driven by the Rayleigh-instability-type transformation. Without adding the nonsolvent, PMMA chains precipitate on the walls of the nanopores after the solvent is evaporated, and PMMA nanotubes are obtained."
Rayleigh-Instability-Driven Morphology Transformation by Thermally Annealing Electrospun Polymer Fibers on Substrates
(1970-01-01)
Fan, Ping-Wen
;
Chen, Wan-Ling
;
Lee, Ting-Hsien
;
Chiu, Yu-Jing
;
Chen, Jiun-Tai
"Electrospinning has been widely used to prepare polymer fibers with diameters ranging from a few nanometers to micrometers. While most studies focus on controlling the sizes and morphologies of electrospun polymer fibers by changing electrospinning conditions, the effect of post-treatments such as thermal annealing on the properties of electrospun polymer fibers has been less studied. Here, we investigate the effect of thermal annealing on the morphology changes of electrospun polystyrene (PS) fibers on substrates. Different from annealing the fibers in a uniform environment, annealing the fibers on substrates results in a substrate-dependent morphology transformation. When the electrospun PS fibers are annealed on a glass substrate, wetting of the fibers on the glass substrate occurs. When the electrospun PS fibers are annealed on a poly(methyl methacrylate) (PMMA)-coated substrate, a Rayleigh-instability-driven morphology transformation is observed. The polymer fibers transform into hemispherical polymer particles caused by the lower surface tension of PS than that of PMMA and the interfacial tension between PS and PMMA. This transformation process is influenced by the annealing time and temperature. The characteristic time of the transformation process is shorter when the sample is annealed at a higher temperature because of the lower polymer viscosity. The size of the polymer particles fits well with the theoretical prediction, which is dependent on the initial fiber diameter and is independent of the annealing temperature."

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