4.3 Electrochemical modified electrode

The chemistry of copper is interesting and complicated and therefore is attractive to the electrochemist in the world to try making it as a sensor. Copper-plated screen printed carbon electrode (CuSPE) has been widely employed in the electrochemical analysis of o- diphenols, glucose, amino acids and oxygen etc. Its preparation is easy and fast with electrodeposition of copper on the surface of screen printed carbon electrode. The Cu particle size can be easily controlled by appropriate electrochemical parameters, and the particle size is around 100-500 nm as shown in Figure 1. The typical voltammogram of CuSPE is shown in Figure 2, the reduction peak at ~ -0.2 V (C1) is attributed to CuΙΙO →CuΙ2O and ~ -0.25 V (C2) is for CuΙ2O → Cu0 (vs. Ag/AgCl), and the anodic peak (A1/A2) is the oxidation of Cu0 to CuΙΙO and CuΙ2O. (1)

• 4.3.1 Photoelectrochemical oxygen sensor using copper-plated screen printed carbon electrodes

  
  The dissolved oxygen (DO) sensor was successfully achieved by using copper-plated screen printed carbon electrode (CuSPE). The photoelectrochemical activity toward DO of the CuSPE was related to the formation of a p-type semiconductor CuΙ2O. It is said that the procedure of photochemical reduction of DO goes with three steps. The first one is that H2O2 must be produced on CuSPE at a potential negative enough (-0.3V vs Ag/AgCl). And then the produced H2O2 is able to oxidize Cu0 to CuΙ2O chemically in the dark. The 3rd step is to excite the semiconductor, CuΙ2O, with light to become CuΙ2O* and thus reduce DO to H2O2 as the signal. Therefore, the DO concentration is measured in the range of 1-8 ppm and further toward real sample analysis of groundwater and tap water.
  



• 4.3.2 Selective detection of o-diphenols on copper-plated screen printed electrodes

  
  



• 4.3.2 Selective detection of o-diphenols on copper-plated screen printed electrodes

  
  It is available to selective detect the o-diphenols such as catechol, dopamine, and pyrogallol with copper-plated screen printed electrode (CuSPE) in the presence of other diphenol and ascorbic acid for clinical and biochemical examination. The possible catalytic oxidation mechanism on the CuSPE is illustrated in the Figure 4. It goes with the following 3 steps, (1) o-diphenol chelating with Cu(II) to form a weak five-member complex intermediate, (2) electron transfer and dehydrogenation reaction, and (3) formation of o- quinone derivative with reduced Cu(I), which can be further reoxidized to Cu(II). As a result, the selective o-diphenols sensor is achieved with amperometric method as shown in Figure 5. (1)
  
  

• 4.3.4 Electrochemical investigation of glucose sensor fabricated at copper-plated screen-printed carbon electrodes

  
  Copper-plated screen-printed carbon electrode (CuSPE) provides a suitable catalytic surface for the amperometric detection of hydrogen peroxide. Glucose oxidase (GOD) is immobilized on the top of the CuSPE to form a glucose sensor. The interaction of copper oxide with GOD was found to be an important factor in the glucose detection. Preliminary investigation under hydrodynamic conditions showed a linear calibration plot up to 26.7 mM glucose with a slope and regression coefficient of 4.5 μA/mM and 0.9902, respectively. The Michaelis-Menten kinetics by nonlinear curve fitting yielded a Km value close to that in solution indicating the ideality and suitability of the present system. Classical mixed potential mechanism is for the first time applied to the enzyme-coated CuSPE to further understand the system.
  
  



• 4.3.5 Amino acid analysis using disposable copper nanoparticle plated electrodes

  
  A disposable copper nanoparticle-plated screen-printed carbon electrode (designated as Cun-SPE100-nm) provides a new material for the determination of native amino acids. All 20 underivatized amino acids can be sensitively determined at 0.0 V vs. Ag/AgCl in pH 8 phosphate buffer solution. The precisely controlled copper nanoparticles can boost up the CuIIO/CuI2O redox signal on the working surface without any prior pretreatment procedure. The formation of a reversible 1:1 CuIIO–amino acid complex on the Cun-SPE100-nm was proposed to play a key role in the reaction mechanism. Stable detection responses were obtained for all amino acids by flow injection analysis with detection limits (S/N = 3) that lie in the range of 24 nM–2.7 μM. Selected amino acids from six representative chemical natures were separated by HPLC and detected at the Cun-SPE100-nm with promising results.
  
  



• 4.3.5 Amino acid analysis using disposable copper nanoparticle plated electrodes

  
  
  
  



• 4.3.6 Novel Preparation and Photoelectrochemical Properties of γ-CuI Semiconductor Nanocrystallites on Screen-Printed Carbon Electrodes

  
  Cuprous iodide (γ-CuI) is an important semiconductor material having a bang gap of 3.1 eV often used for visible light assisted photoelectrochemical and solar energy conservation systems. It is reported that the first and unique preparation of fine and precisely controlled g-CuI semiconductor nanocrystallites on the surface of a screen-printed carbon electrode using a photoelectrochemical copper nanoparticle deposition method with tris(hydroxymethyl)-aminomethane (Tris) buffer solution as a control medium. Tris buffer helps to split CuI2O and CuIIO oxidation states through specific complexation mechanism and in turn to selective iodination of CuI2O to the formation of γ-CuI on the electrode. Stable and linear photoelectrochemical response was further demonstrated against variable light intensity up to 400 Klux using the γ-CuI modified system.
  
  

• 4.3.6 Novel Preparation and Photoelectrochemical Properties of γ-CuI Semiconductor Nanocrystallites on Screen-Printed Carbon Electrodes

  
  
  
  

• 4.3.7 Multiple screening of urolithic organic acids with copper nanoparticle-plated electrode: Potential assessment of urolithic risks

  
  There is yet to be a reliable prediction of urolithiasis. To facilitate early diagnosis, a simple and rapid high performance liquid chromatography method with electrochemical detection using disposable coppernanoparticle-plated electrodes (Cun-SPE) was developed for multiple detection of creatinine and 4 urolithic organic acids. A total of 206 normal and urolithic human and canine urines and urolith samples were collected for direct analysis of creatinine, cystine, uric acid, oxalic acid, and citric acid without sample cleanup and derivatization processes. Urinary organic acids were separated in 11 min and were devoid of ascorbic acid interference. The detection limits (S/N > 3) were at the nanomolar level with linear dynamic ranges spanning 2–3 orders of magnitude. Recoveries in urine ranged from 99.5% for creatinine to 86.5% for citric acid. The analytical variations (RSD) were less than 6.2% in phosphate buffer and 7.7% in urine. Important differences in organic acid levels/profiles between animal species and among normal and urolithic urines/urolith were unveiled and corresponded well (70–90%) with the urolithic risk in a retrospective assessment. The simplicity and reproducibility of this method using disposable Cun-SPE has made routine urine analysis possible and can be of great clinical and diagnostic potential in the screening of urolithiasis and abnormal states related to excess secretion of organic acids and amino acids in humans and animals.
  

• 4.3.7 Multiple screening of urolithic organic acids with copper nanoparticle-plated electrode: Potential assessment of urolithic risks

  
  
  

Reference

Please click the link below

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• 2.Jyh-Myng Zen,* Hsieh-Hsun Chung, and Annamalai Senthil Kumar, Anal. Chem. 2002, 74, 1202-1206
• 3.Annamalai Senthil Kumar and Jyh-Myng Zen, Electroanalysis 2002, 14, No. 10
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• 5.Chung-Wei Yang, Jyh-Myng Zen, Yu-Lin Kao, Cheng-Teng Hsu, Tung-Ching Chung, Chao-Chin Chang, Chi-Chung Chou, Analytical Biochemistry 395 (2009) 224–230
• 6.Cheng-Teng Hsu, Hsieh-Hsun Chung, Annamalai Senthil Kumar, Jyh-Myng Zen, Electroanalysis 17, 2005, No. 20, 1822 – 1827