Deog-Su Park

Determination of HgII Ion with a 1,11-Bis(8-quinoyloxy)-3,6,9-trioxaundecane-Modified Glassy Carbon Electrode Using Spin-Coating Technique

A glassy carbon electrode modified with an open-chain crown ether, 1,11-bis(8-quinolyloxy)-3,6,9-trioxaundecane (BQT), using a spin coating method, has been applied for the highly selective and sensitive analysis of trace amounts of HgII. The modified electrode HgII ion was spontaneously deposited on the modified electrode and the resulting surfaces were characterized by anodic stripping voltammetry. The linear sweep voltammogram of the modified electrode deposited with HgII ion shows a well-defined anodic peak at +0.17 V. The detection limit with linear sweep voltammetry was 1.0 × 10−8 M and was about 7.0 × 10−10 M HgII by differential pulse anodic voltammetry. The response reproduced with a value of 6.1 % relative standard deviation. The presence of 20-fold molar AgI, CdII, PbII, FeII, NiII, CoII, CuII, AlIII, MgII, SbIII, TiII, and ZnII did not interfere in the analysis of HgII ion except FeII. The electrode has been successfully applied to the determination of trace amounts of the HgII ion in the human urine sample.

Water sensor for a nonaqueous solvent with poly(1,5-diaminonapthalene) nanofibers.

A water sensor for a nonaqueous solvent was fabricated using poly(1,5-diaminonapthalene (DAN) nanofibers, which were prepared through a catalytic chemical polymerization of the DAN monomer using Fe(III) salt as the catalyst. Poly(1,5-DAN) nanofibers were characterized by atomic force microscope (AFM), transmission electron microscope (TEM), scanning electron microscope (SEM), and UV-vis spectroscopy. The electrochemical properties of poly(1,5-DAN) nanofibers were investigated using cyclic voltammetry (CV). The electrochemical activity of poly(1,5-DAN) nanofibers was utilized for water sensing. The fabrication of water sensor was followed by placing one drop (about 2 microL) of 0.01% poly(1,5-DAN) nanofibers solution in the gap between two split gold electrodes (PBSA) and completely dried. The response of the water sensor in an acetonitrile solution was evaluated under optimized conditions. The linear dynamic range was from 0.05 to 20%, and the detection limit was determined to be 0.01%. The response of this sensor was shown to be comparable to that obtained with the Karl Fischer titration method.

Development of extraction and analytical methods of nitrite ion from food samples: microchip electrophoresis with a modified electrode.

Two simple and fast methods for the extraction of the nitrite ion (NO(2)(-)) from food samples have been developed. The methods were characterized by UV-visible spectroscopic and electrochemical measurements, and their performance for NO(2)(-) extraction was compared with a standard method. The extraction methods yielded relative recoveries between 100 and 120% with good reproducibility of 3.9% (RSD, n = 4) in UV-visible experiments. Microchip electrophoresis with electrochemical detection (MCE-ED) coupled with a copper (3-mercaptopropyl)trimethoxysilane [Cu(II)-MPS] complex-modified carbon paste electrode (CPE) has been employed to detect NO(2)(-) in extracted samples. The Cu(II)-MPS complex was synthesized and characterized by voltammetry, XPS, and FT-IR analyses. Experimental parameters affecting the separation and detection performances of the MCE-ED method were assessed and optimized. The potential for the electrocatalytic reduction of NO(2)(-) for MCE-ED was found to be -190 mV (vs Ag/AgCl). When extracted food samples were analyzed by the MCE-ED method, a reproducible response for the NO(2)(-) reduction (RSD of 4.3%) at the modified-CPE reflected the negligible electrode fouling. A wide dynamic range of 1.0-160 ppm was observed for analyzing standard NO(2)(-) with a sensitivity of 0.05106 ± 0.00141, and the detection limit, based on S/N = 3, was found to be 0.35 ± 0.05 ppm. No apparent interference from NO(3)(-), other inorganic ions, and biological compounds was observed under the optimal experimental conditions. A standard addition method for real samples showed wide concentration ranges of 1.10-155 and 1.2-150 ppm for analyzing NO(2)(-) in ham and sausage samples, respectively.

Polyterthiophene π-conjugated by organomolybdenum complex (II): electropolymerization of erythro-[(η5-C5H5)2Mo2(O)2(μ-O){μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}]

Abstract Terthiophene, to which the organomolybdenum oxide cluster complex is π-conjugated, erythro-[(η5-C5H5)2Mo2(O)2(μ-O){μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}] (2) was prepared by treatment of erythro-[(η5-C5H5)2Mo2(CO)4{μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}] (1) with air in the presence of trimethylamine N-oxide in 1:1 MeCN–CH2Cl2. The structure of 2 was identified by spectroscopic methods and elemental analysis. CV of 2 in TBAP–CH2Cl2 solution exhibits three discrete electrode processes. Two reversible processes, at Epa=0.89 and 1.08 V, are associated with the oxidation of the cluster core to the radical cation, [Mo2core] + and dication, [Mo2core]2+, respectively. Irreversible process at Epa=1.30 V can be assigned to the terthiophene moiety. Electrochemically active, polymer film of 2 shows an electrochromic switching between shiny purple (undoped) and transparent blue (doped), which is sharply discerned form the color contrast of the typical polythiophenes as well as 1. Such a unique electrochormism can be ascribed to the direct π-electronic interaction between the conjugated organomolybdenum cluster and the polythiophene backbone.

Polyterthiophene appended by transition-metal cluster: electropolymerization of 3′-[CCo3(CO)9]-5,2′:5′,2″-terthiophene

Abstract Terthiophene, to which cobalt carbonyl cluster complex is π-conjugated, 3′-[CCo3(CO)9]-5,2′:5′,2″-terthiophene (3′-CoTTh), was prepared by reaction of 3′-chloromercuro-5,2′:5′,2″-terthiophene with HCCo3(CO)9. The molecular structure of 3′-CoTTh is identified by spectroscopic methods and elemental analysis. Cyclic voltammetry of 3′-CoTTh showed deposition of electroactive polymer films on the electrode surface. The absorption spectra of 3′-CoTTh and its polymer films are presented.

Fabrication of a novel disposable glucose biosensor using an electrochemically reduced graphene oxide–glucose oxidase biocomposite

A disposable glucose biosensor has been fabricated on the surface of a cost-effective pencil graphite electrode (PGE) by an electrochemical method, using glucose oxidase (GOx) and reduced graphene oxide (rGO). Electrochemical pre-treatment of the PGE enables the adsorption of the rGO–GOx biocomposite. The biocomposites of GOx and rGO were simply prepared by the electrochemical potential cycling method. Efficient immobilization of rGO–GOx is confirmed by field emission scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry measurements. The rGO nanosheets enhance direct electron transfer (DET) between GOx and the electrode surface. Determination of glucose indirectly by O2 reduction was achieved, which showed high sensitivity, selectivity, reproducibility and stability without a redox mediator. The sensor exhibits a linear current response for a wide range of glucose concentrations between 1.0 × 10−5 and 1.0 × 10−3 M (R = 0.998), and a dynamic range up to 10.0 × 10−3 M with a detection limit of 5.8 μM. The rGO–GOx biosensor showed an excellent anti-interference ability against electroactive species and proved to be useful for the determination of glucose in human serum samples.

Disposable in-field electrochemical potable sensor system for free available chlorine (FAC) detection

The work described in this study concerns the development of a disposable amperometric sensor for the electrochemical detection of a well-known aqueous pollutant, free available chlorine (FAC). The FAC sensor developed used screen printed carbon electrodes (SPCEs) coupled with immobilised syringaldazine, commonly used as an indicator in photometric FAC detection, which was directly immobilised on the surface of SPCEs using a photopolymer PVA-SbQ. To enable in-field analysis of FAC, a prototype hand-held electrochemical analyzer has been developed to withstand the environment with its rugged design and environmentally sealed connections; it operates from two PP3 (9 volt) batteries and is comparable in accuracy and sensitivity to commercial bench top systems. The sensitivity of the FAC sensor developed was and the detection limit for FAC was found to be .

Tri-enzyme modified electrochemical biosensor for paracetamol detection

A new disposable amperometric tri-enzyme biosensor for the detection of paracetamol has been developed. The paracetamol sensors developed uses horseradish peroxidase modified screen-printed carbon electrodes (HRP-SPCEs) coupled with immobilized enzymes, tyrosinase and aryl acylamidase, prepared using a poly (vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) matrix. Optimization of the experimental parameters has been performed and the paracetamol biosensor showed detection limit for paracetamol is as low as and the sensitivity of the sensor is .

Fabrication of Flow Cell Using Carbon Fiber and Electrochemical Decomposition Characteristics for Organic Dyes

Abstract The simulated dyes solution containing Basic Red 46(BR 46), Yellow 21(Y 21), and Maxilon Blue 30(MB 30) were electrochemically oxidized using carbon fiber as an anode. The electrolyses were performed in a electrolytic flow cell constructed by Vycor glass tube. The carbon fiber was positioned in the inside of Vycor glass tube and platinum wire coiled around outside of tube as a cathode. Several operating variables, such as current, time, pH and flow rate of solution were studied. Increasing current density would lead to a corresponding increase in the dye removal efficiency 99.2 % at a 200 mA. The electrolyses time could also improve and removal efficiency was about 99 % after 1.5 hours of electrolyses. The removal efficiency was increased with the increase of flow rate of solution and optimum flow rate was 5 mL/min. THe pHs of solution affect the removal efficiency. The removal efficiency was decreased with the increase of pH of solution and optimum pH was 5.05 (0.1 M KNO 3 ).

Fabrication of Polyimide Film Electrode by Laser Ablation and Application for Electrochemical Glucose Biosensor

An ultraviolet pulsed laser ablation of polyimide film coated with platinum has been used to enhance the sensitivity for the application as an electrochemical biosensor. Densely packed cones are formed on polyimide surface after UV irradiation which results in increase of surface area. In order to apply the sensitivity improvement of laser ablated polyimide film electrodes, the glucose oxidase modified biosensor was fabricated by using an encapsulation in the gel matrix through sol-gel transition of tetraethoxysliane on the surface of laser ablated polyimide film. The optimum conditions for glucose determination have been characterized with respect to the applied potential and pH. The linear range and detection limit of glucose detection were from 2.0 mM to 18.0 mM and 0.18 mM, respectively. The sensitivity of glucose biosensors fabricated with laser ablated polyimide film is about three times higher than that of plain polyimide film due to increase in surface area by laser ablation.