Electrode BPPG

Figure 3.12 Cyclic voltammetric response of (a) abrasively modified MWNT basal pyrolytic graphite (bppg) and (b) film modified MWNTs on bppg electrodes in a pH 7.4 phosphate buffer solution containing 1.2 mM NADH.

Clay/ionic liquid modified electrodes Sun investigated the use of Hb/clay/IL composite MEs for the electrocatalytic detection of HjOj, TCA, and nitrite [43]. The IL [C4CiIm][PFg] (2 mL) was stirred with bentonite clay (1 mg) for 1 h after which 1 mg of Hb was dispersed into the mixture. A volume of this dispersion was then cast onto a freshly polished basal plane pyrolytic graphite (BPPG) electrode. UV-Vis studies revealed the position of the Hb Soret band to be 410 and 412 nm for dry and buffer-immersed films, respectively. This is consistent with a near-native environment surrounding the heme within Hb in the Hb/clay/... 

Fig. 9.11 Basal-plane pyrolytic graphite electrode in vitamin Bi2r at a scan rate of 0.5 V for (a) unmodified BPPG in 1.2 mM vitamin Bur solution, (b) modified BPPG with DBCH in buffer solution, and (c) modified BPPG in vitamin Bi2r solution. Reproduced from P. Tomcik et al, Anal. Chem. 76 (2004) 161, with permission from the American Chemical...

The choice of a BPPG electrode for the experiment described is partly since the material needs to be inactive with respect to the reduction of DBCH. The reduction of allylbromides has a high overpotential on carbon electrodes as compared to, say, silver electrodes. Additionally, the flat surface allows droplets of the oily DBCH to be formed on the electrode surface. 

Fig. 9.18 Cyclic voltammograms for the reduction of chlorine in 0.1 M nitric acid solution using EPPG (0.196 cm2), qq (0.07cm2), BPPG (0.196cm ), and BDD (0.07cm ) electrodes. All scans were recorded at 100 mV s vs. SCE. Reproduced from E.R. Lowe et al, Anal. Bioanal. Chem. 382 (2005) 1169, with permission from Springer.

One simple way of characterization of CNT/MN4 electrodes using electrochemical techniques like cyclic or linear voltammetry is using a well-known redox probe, for example, the couple ferri/ferrocyanide, Fe(CN)6 /Fe(CN)6. The MWCNT-BPPG... 

Luz et al. have proposed the combination of an iron-porphyrin (iron(m) tetra-(iV-methyl-4-pyridyl)-porphyrin noted as FeT4MPyP) co-adsorbed with MWCNTs on BPPG electrode for the electrocatalysis of GSH oxidation in phosphate buffer (pH 7.4). In comparison to bare BBPG or BBPG modified with either FeT4MPyP or MWCNTs only, the hybrid FeT4MPyP/MWCNT electrode exhibits improved catalytic effect in terms of overpotential and of catalytic current intensity (Fig. 19). 

Fig. 19 a Cyclic voltammograms obtained at bare BPPG and at FeT4MPyP/MWCNT/BPPG electrode in presence (2 and 4, respectively) or in absence (1 and 3, respectively) of 5 mM glutathione. b Evolution of anodic peak euiient intensity of GSH oxidation as a function of GSH concentration between 0 and 6 mM (in phosphate buffer pH 7.4, deduced from square wave voltammograms shown in the insert). Adapted from Ref [184]... 

Fig. 6 (A) Cyclic voltaimnograms (scan rates 0.1 Vs ) for the reduction and back-oxidation of MB-UMCM-1 immobilised at a bppg electrode and immersed in aqueous 0.1 M acetate solution at (i) pH 2.2, (ii) pH 5.0, (iii) pH 7.0, (iv) pH 9.0, and (v) pH 11.3. Inset molecular and pore structure. (B) Plot of the midpoint potentials versus pH (taken from ref. 71).

Fig. 7 (A) CycKc voltammograms (scan rate (i) 10, (ii) 35 and (iii) 100 mVs ) for the oxidation of UMCM-l-NHFc powder immobilised at bppg electrode and immersed in DCE with 0.1 M NBU4PF6. Schematic diagram of the ferrocenyl MOF reactivity in organic media. (B) CycHc voltammograms (scan rate 20 mVs , the first four scans shown) for the oxidation of UMCM-l-NHFc powder in aqueous 0.1 M phosphate buffer pH 1. Schematic drawing of reactivity in aqueous media. (Q Drawing of the proposed pore redox process present in MIL-53(Al)-NHFc involving (i) removal of one electron, (ii) fast expulsion of one proton and (iii) attack of the hydroxide on the framework (taken from ref. 72).

Fig. 12 (A) Cyclic voltammograms (scan rate 100 mV s ) for Co-MOF-71 particles on a bppg electrode immersed in a 0.1 M NaOH over 10 scans (first scan shown as dashed line). (B) As before but with Co(OH)2 particles. (C) Photographs of crystal colours during transformation. (D) Microscopy images of a crystal (ca. 20 pm) during conformal transformation from Co-MOF-71 (red) to CoOOH (brown) (taken from ref. 86).

Fig. 9 (A) Cyclic voltammograms of an EPPG (black line) and a BPPG (grey line) electrode in...

In the case of modification of BPPG electrode with graphene, a contrasting behaviour is observed as the addition of small and larger quantities of graphene resulted both in a decreased electron transfer kinetics and even in completely blocked interfaces. 

An important contribution towards understanding the electrochemical reactivity of graphene is that by Tsai et al. They compared naked basal (BPPG) and edge plane pyrolytic graphite (EPPG) electrodes with... 

Fig. 15 (A) CV recorded on bare BPPG (a), rGO/BPPG (b), bare EPPG (c), and rGO/EGGP (d) electrodes in NADH (2 mM)/PBS (0.1 M, pH 7) (print with permission from ref. 72). (B) CV of GC electrode modified with chitosan (a), glucose oxidase-chitosan (b), GO-chitosan (c), and glucose oxidase-GO-chitosan (d) films in PBS with N2 saturation, scan rate 100 mV s (print with permission from ref. 75).

The diagnosis of an adsorbed species is to explore the effect of scan rate on the voltammetric response, which should yield a linear response for the case of Ipversus scan rate n. A practical example is shown in Fig. 2.45 where Hemoglobin (Hb)— Dimyristoyl phosphatidylcholine (DMPC) films are immobilised upon a BPPG surface. The modified electrode was then explored with the voltammetric response evident in Fig. 2.45a, with a plot of peak current against scan rate also... 

Using a simple redox couple. Fig. 3.5 depicts the voltammetry obtained when using either a Basal Plane Pyrolytic Graphite (BPPG) (i) or (ii) an EPPG electrode of HOPG, and the responses are compared with numerical simulations (iii) assuming linear diffusion only, in that, all parts of the electrode surface are uniformly (incorrectly) electrochemically active. Two features of Fig. 3.5 are to be... 

Fig. 3.19 Cyclic voltammetric profiles recorded utilising 1 mM potassium ferrocyanidefll) in 1 M KCl. a obtained using a BPPG electrode (dotted line) with the addition of increasing amounts of 2, 4, 50, 100, and 200 pg graphite (solid lines), b obtained using an EPPG electrode (dotted line) with the addition of increasing amounts of 10, 20, 30, and 40 ng graphene (solid lines). Scan rate 100 mVs (vs. SCE). Reproduced from Ref. [33] with permission from The Royal Society of Chemistry...

Fig. 4.1 Cyclic voltammograms obtained using (a) bare BPPG electrode (b) graphene modified BPPG electrode...

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