Browsing by Author "Zeng, Jun-Ru"

Now showing 1 - 2 of 2

Fabrication of two-dimensional photonic crystals of tethered polyvinyltetrazole on silicon surfaces for visualization in Cu2+ ion sensing
(2017-04)
Zeng, Jun-Ru
;
Cheng, Chih-Chia
;
Chang, Chi-Jung
;
Huang, Chi-Hsien
;
Chen, Jem-Kun
We grafted polyacrylonitrile (PAN) from a flat silicon substrate via atom transfer radical polymerization (ATRP) as a bottom layer. Fabrication processes, involving very-large-scale integration (VLSI) and reactive ion etching (RIE), are sequentially used to generate 800 nm-diameter hole array of tethered PAN layer as two-dimensional photonic crystals (2DPCs). The tethered PAN 2DPCs were then subjected to a cyano-totetrazole conversion reaction to generate tethered polyvinyltetrazole (PVT) 2DPCs. Fabricating hole array could be regarded as air filling within the PVT layer, resulted in a significant decrease of effective refractive index of the PVT film. In addition, the adsorption of Cu2+ ions to the tetrazolyl groups was highly selective in solutions also containing Na+, K+, Ca2+, and Mg2+ ions. After absorption of Na+, K+, Ca2+, Mg2+, Fe3+, and Zn2+ ions, the tethered PVT 2DPC displayed insignificant changes in its effective refractive index; in contrast, upon absorbing Cu2+ ions, a dramatic change in effective refractive index occurred, resulting in a color change from red to green, observable to the naked eye along an incident angle of 30-40 degrees. The holes dimension within the array of tethered PVT shrunk after absorption of Cu2+ ions leading to a predominated blue-shift in the diffractive peak position. The tethered PVT 2DPC-based assay exhibited high sensitivity and selectivity in an experimentally simple setup for visualization in Cu2+ ion sensing.(C) 2016 Elsevier Ltd. All rights reserved.
Visualization platform of one-dimensional gratings of tethered polyvinyltetrazole brushes on silicon surfaces for sensing of Cr(III)
(2017-08-01)
Zeng, Jun-Ru
;
Cheng, Chih-Chia
;
Lee, Ai-Wei
;
Wei, Po-Li
;
Chen, Jem-Kun
Polyacrylonitrile (PAN) was grafted on silica (Si) surfaces in the form of one-dimensional (1D) gratings to form well-defined line patterns. The tethered PAN 1D gratings were then subjected to a cyano-to-tetrazole conversion reaction to generate a tethered polyvinyltetrazole (PVT) 1D grating. This results in different properties for the transverse magnetic (TM) and transverse electric (TE) polarizations, i.e. perpendicular and parallel to the line patterns, respectively. After adsorption of Cr(III), the negative charges of PVT chains were neutralized, and this results in a collapse of the polymer brushes. As a result, the effective refractive indices vary with the concentration of Cr(III). This causes a gradual color change from yellow via green to blue at incident angles of 30-40 degrees. The adsorption of the ions Na+, Ag+, Ca2+, Cd2+, Fe3+, Zn2+ and Cr6+ ions, in contrast, does not cause significant changes in the effective refractive index. The Cr(III)-induced deswelling transitions can be reversed by treatment with acid. The assay has a limit of detection (LOD) as low as 20 mu g.L-1 of Cr( III). The ions Pb(II), Cu(II) and Cr(VI) are also adsorbed by the PVT grating, but the respective LODs are higher (80, 100 and 40 mu g.L-1)