A copper-sensitive chemically modified electrode (CME) has been constructed by incorporating di(2-imino-cyclopentylidine mercaptomethyl) disulfide (didd) into the carbon paste composed of graphite powder and Nujol oil. Copper(1) ion was chemically deposited on the CME by immersing it in the Cu(1) solution. The resulting surfaces were characterized by cyclic and differential pulse voltammetry. The CME's surface could be regenerated by applying more positive potential than the stripping potential of the Cu(1) ion and then used for another deposition. After seven deposition/measurement/ regeneration cycles, the peak current of voltammograms of the analyte decreases slightly. The differential pulse technique was also applied to the above system. In this case, the detection limit for Cu(1) ion was 5 X lo-'' M for 30 minutes of deposition time. After reduction of Cu(I1) ion to Cu(1) in the sample solution with hydroxylamine, satisfactory results were obtained for the determination of copper in certified standard urine reference material SRM's 2670 (trace elements in urine).
KEY WORDS:Chemically modified electrode, Determination of Cu( I), Di(2-imino-cyclopentylidine mercaptomethyl) disulfide.
In this paper, we propose a new buried channel array transistor structure to solve the problem of current leakage occurring in the capacitors of dynamic random-access memory (DRAM) cells. This structure has a superior off current performance compared with three previous types of structures. In particular, the proposed buried channel array transistor has a 43% lower off current than the conventional asymmetric doping structure. Here, we show the range of the effective buried insulator parameter according to the depth of the buried gate, and we effectively show the range of improvement for the off current.
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