A Study of Self-Assembling Membrane Separation and Amperometric Molecular Sensing
Date Issued
2004
Date
2004
Author(s)
Chen, Hung-Chieh
DOI
zh-TW
Abstract
Due to the common problems found in bio-analytical methods, in which high cost, large instrument, uneasy storage and time consuming are encountered. This research tries to develop an inexpensive, small and fast response analyzing method by a modified membrane and a modified electrode. Major results of this research are summarized in the following paragraphes.
In polycarbonate track-etched (PCTE) porous membrane, its basic separation properties were measured by the fluid permeation, SEM and AFM. The results showed that the effective pore radius was 21±1 nm and the pore density was 7.5x108 pores/cm2. By using an electroless plating method, the surface of the PCTE membrane was covered with a conductive golden thin film. The average electroless plating rate was around 8~9 nm/hr. Based on this conductive golden-coated PCTE membrane, the permeated flux of the ions could be adjusted by an applied potential. Besides, a cysteine (Cys) self-assembling monolayer (SAM) of golden-coated PCTE membrane was used. Adjusting the pH value of the solution could control the surface charge of SAM membrane and achieve the selective permeation for a target molecule in the solution. The permeated properties of SAM membrane were studied with three kinds of molecules, methyl blue (MB), methyl orange (MeO) and morphine (MO). The results showed that the highest permeated flux were obtained with high, low and neutral pH values solution for MB, MeO, and MO, respectively.
In electrochemical MO sensing, cyclic voltammetry (CV) results showed that only high concentration of iodide solution could promote the oxidation of MO and enhance the current response. The amperometric detection of MO was performed by a static potential at 0.65 V (vs. Ag/AgCl) in 0.1 M iodide solution with the sampling time of 150 s. The sampled current was linearly dependent on MO concentration ranged from 100 μM to 600 μM. The sensing sensitivity was 3.69 μA/cm2-μM. Oxidized MO in this study would precipitate as white powder. After rinsing the white precipitation, it was analyzed by 1H NMR and MS, and identified to be the pseudomorphine (PMO) which was the same as the product reported in the literature.
Another electrochemical sensing was performed with a nickel hexacyanoferrate (NiHCF) modified electrode for Cys sensing. The NiHCF thin film was coated by the CV method on a F-doped tin oxide (FTO) conductive glass substrate. It was found that the stability of the NiHCF modified electrode could be improved by adding Ni2+ ions in the solution. The amperometric detection of Cys was performed by a static potential at 0.8 V (vs. Ag/AgCl) in 15 mM Ni2+ ions and 0.1 M KH2PO4 solution with the sampling time of 50 s. The sampled current was linearly dependent on Cys concentration ranged from 150μM to 1 mM. The linear correlation is within the normal Cys concentration in a healthy human body.
From the above results, the SAM modified membrane and the modified electrode provide a bioanalytical detection method with the potential for easy operation, short detecting time, inexpensive material and easy storage. We believe that the results will promote the multi-development on the bioanalysis.
Subjects
電化學感測
嗎啡
半胱胺酸
SAM薄膜分離
修飾電極
morphine
modified electrode
SAM membrane separation
cysteine
electrochemical detection
SDGs
Type
thesis
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