Yen-Wen Lin

Synthesis and characterization of acrylic acid-containing dextran hydrogels

pH-Sensitive dextran hydrogels were prepared by free radical polymerization of methacrylate derivatized dextran, acrylic acid and N-t-butylacrylamide. Incorporation of acrylic acid in hydrogels was confirmed by Fourier transform infrared spectroscopy. The pH-dependent swelling of hydrogels was strongly influenced by the acrylic acid content, conjugation degree of methacrylate moiety with dextran and modified dextran concentration. Intermolecular polymerization that occurred to a greater extent with a lower degree of conjugation of methacrylate and/or higher concentration of modified dextran effectively increased the network density of hydrogels. An increase of acrylic acid reduced the enzymatic degradability of pre-swollen hydrogels by dextranase, although the increased equilibrium swelling was observed.

Nanostructured Ag surface fabricated by femtosecond laser for surface-enhanced Raman scattering

Femtosecond laser was employed to fabricate nanostructured Ag surface for surface-enhanced Raman scattering (SERS) application. The prepared nanostructured Ag surface was characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The FESEM images demonstrate the formation of nanostructure-covered femtosecond laser-induced periodic surface structure, also termed as ripples, on the Ag surface. The AFM images indicate that the surface roughness of the produced nanostructured Ag substrate is larger than the untreated Ag substrate. The XRD and XPS of the nanostructured Ag surface fabricated by femtosecond laser show a face centered cubic phase of metallic Ag and no impurities of Ag oxide species. The application of the produced nanostructured Ag surface in SERS was investigated by using rhodamine 6G (R6G) as a reference chemical. The SERS intensity of R6G in aqueous solution at the prepared nanostructured Ag surface is 15 times greater than that of an untreated Ag substrate. The Raman intensities vary linearly with the concentrations of R6G in the range of 10(-8)-10(-4)M. The present methodology demonstrates that the nanostructured Ag surface fabricated by femtosecond laser is potential for qualification and quantification of low concentration molecules.

Preparation and Electrochemical Performance of Externally Doped Sulfonated Polyaniline/Multiwalled Carbon Nanotube Composites

The externally doped sulfonated polyaniline (ED-SPANI) has emerged as a potential candidate for electrochemical sensors because of its unique electroactive property and water solubility. However, the lower conductivity is the major drawback for the application of ED-SPANI. Thus, this study describes a simple procedure for the fabrication of water-soluble and high conductivity composites containing ED-SPANI and multiwalled carbon nanotubes with attached carboxylic groups (c-MWCNTs) by electrostatic adsorption in aqueous colloids. The results of Fourier transform IR and Raman spectroscopy demonstrate the electrostatic interaction between the C―N + species of the ED-SPANI structures and the COO- species of the c-MWCNTs. The incorporation of the c-MWCNTs into ED-SPANI can significantly enhance the electrical conductivity and electrochemical activity of ED-SPANI/c-MWCNT composites. Furthermore, the morphology of ED-SPANI/c-MWCNT composites measured by scanning electron microscopy and atomic force microscopy indicates the presence of well-distributed tubular structures that are individually coated with ED-SPANI on the surface of the composite, in accordance with the high electrical conductivity and electrochemical properties of the composites.