Electrochemically composite films

Despite the considerable progress made in the few years in which anodic insertion/extraction films have been known, neither film compositions, film properties, nor electrochemical reactions are sufficientiy well characterized. There have been disagreements, as indicated for h-IrO and h-NiO in Table 2, as to whether is being extracted or OH inserted during coloration. The general problem is best illustrated by the important example of Pmssian blue. Early work (47—50) resulted in two different sets of equations for electrochromic reduction ... 

G. Wang, J.J. Xu, and H.Y. Chen, Interfacing cytochrome c to electrodes with a DNA-carbon nanotube composite film. Electrochem. Commun. 4, 506-509 (2002). 

Q. Huang, Z. Lu, and J.F. Rusling, Composite films of surfactants, Nafion, and proteins with electrochemical and enzyme activity. Langmuir 12, 5472-5480 (1996). 

Constantinos G. Tsiafoulis et al. report the electrochemical behaviour of a composite film based on ferrocene intercalated V205.nH20 xerogel (FeCp2-VXG) with photocrosslinkable polyvinyl alcohol with styrylpyridinium residues (PVA-SbQ), in order to be used as an electrocatalyst and host protein platform to develop an amperometric biosensor. 

Owing to these characteristics, PG has been extensively used for the adsorption of DNA and its derivatives. DNA was successfully adsorbed on PG by dry-adsorption at 100 °C [67]. The electrodes were stored in TriS buffer at 4 °C without loss of DNA, showing that DNA was firmly adsorbed on PG. It was demonstrated that the adsorbed ODN was also able to be hybridized with its complementary strand, suggesting that although DNA bases are compromised in the adsorption, they are still available for hybridization [67]. A composite film of DNA and the polyanionic perfluorosulfonated ionomer Nation was cast on PG by the layer-by-layer procedure performed by dry-adsorption [68]. In another approach, the PG surface was electrochemically pretreated at - 1.7 V for 60 s. DNA was then wet-adsorbed at the pretreated electrode surface from solutions containing 0.2 M NaCl, 10 mM Tris- HCl, pH 7.4, for 1 min followed by rinsing the electrode with distilled water [69,70]. 

Sun, H., Direct electrochemical and electrocatalytic properties of heme protein immobilized on ionic liquid-clay-nanoparticle-composite films,/. Porous Mater., 13, 303-397,2006. 

Ghen, H., Wang, Y, Liu, Y., Wang, Y, Qi, L., and Dong, S., Direct Electrochemistry and electrocatalysis of horseradish peroxidase immobilized in Nafion-RTIL composite film, Electrochem. Commun., 9, 469-474, 2007. 

The incorporation of Ru(II) chelates in various types of silica sol-gel-based composite films is another mode of immobilization.262,280-284 Silica sol-gel materials provide some advantages over organic polymers such as the ease with which they can be prepared, modified, and doped with various reagents. Particularly, silica sol-gel films are stable upon continuous electrochemical oxidation or upon drying the gels in a high humidity environment. 

Huang, F., Z. Fu, and Q. Qin. 2003. A novel Li2Ag05V2O5 composite film cathode for all-solid-state lithium batteries. Electrochem. Comm. 5 262-266. 

Kuwabata S, Kishimoto A, Tanaka T, Yoneyama H. Electrochemical synthesis of composite films of manganese dioxide and polypyrrole and their properties as an active material in lithium secondary batteries. J Electrochem Soc 1994 141 10-15. 

Due to their small size and high surface area, nanoparticles can be applied to modify electrode surface property. Convenient and sensitive electrochemical sensors to various targets have been set up by using nanoparticle modification. The determination of acetaminophen in a commercial paracetamol oral solution was reported using a multiwall CNTs composite film-modified glassy carbon electrode with a detection limit of 50 nM (Li etal. 2006a). Heavy metal ions, such as ar-senite (Dai and Compton 2006 Majid et al. 2006) and lead ion (Cui et al. 2005),... 

Feng, K. J., Yang, Y. H Wang, Z. J., Jiang, J. H., Shen, G. L. and Yu, R. Q. (2006), A nano-porous Ce02/Chitosan composite film as the immobilization matrix for colorectal cancer DNA sequence-selective electrochemical biosensor. Talanta, 70(3) 561-565. 

Li, C. Y., Zhan, G. Q., Yang, Q. D. and Lu, J. J. (2006a), Electrochemical investigation of acetaminophen with a carbon nano-tube composite film electrode. Bull. Korean Chem. Soc., 27(11) 1854-1860. 

The second important feature of a metal-semiconductor composite approach is that the metal can function as a template for chemical or electrochemical deriva-tization to afford a film comprising of molecular redox-semiconductor (or even semiconductor-semiconductor) contacts. Figure 34 generically illustrates the occlusion electrosynthesis approach for preparing M-TiO composite films and a subsequent derivatization with ferri/ferrocyanide to afford the corresponding metal hexacyanoferrate (MHCF)-Ti02 counterparts [424]. 

Yogeswaran et al., designed a new bimetallic nanoparticles (Au and Pt) modified electrodes for simultaneous determination of AA, EP and UA [169], First, a composite film comprising of functionalized multiwall carbon nanotubes and nafion was formed on the GC electrode. Then Au and Pt NPs were electrochemically deposited on to the composite film modified GC electrode. The voltammetric peaks of AA, EP and UA are well resolved with the peak separations of 222 mV and 131 mV respectively. Lu et al., demonstrated the determination of UA on GC electrode electrodeposited with AuNPs and DNA [170], Clean GC electrode was immersed into a AuNPs colloidal solution and a potential of +1.5 V is applied for 60 min for the deposition of AuNPs. Then the electrode was dipped into a DNA solution (0.1 mg/ml) and a potential of +1.5 V is applied for 30 min to electrodeposit DNA. Finally, DNA/AuNPs modified electrode excellently separates the voltammetric signals of UA, NEP and AA. Li et al., electrodeposited AuNPs on the GC electrode modified with the ultrathin overoxidized polypyrrole film [171], The modified determines the UA in the presence of EP and AA with a lowest detection limit of 1.2 x 10"8 M. 

Figure4. (A) SEM imagesof prepared porous nanosheet-based ZnOmicrosphere with different magnification. (B) FTIR spetra of hemoglobine (Hb) and Hb-ZnO- nafion composite film. (Reprinted from Biosensors and Bioelectronics 24, X. Lu, H. Zhang, Y. Ni, Q. Zhang, J. Chen, Porous nanosheet-based ZnO microspheres for the construction of direct electrochemical biosensors, 95, Copyright ( 2008) with permission fom Elsevier.

Ingersoll, D., Kulesza, P.J., and Faulkner, L.R. 1994. Polyoxometallate-based layered composite films on electrodes. Preparation through alternate immersions in modification solutions. Journal of the Electrochemical Society 141, 140-147. 

Bardetsky, D. and Zhitomirsky, L, Electrochemical preparation of composite films containing cationic polyelectrolytes and cobalt hydroxide, Surf. Eng., 21, 125, 2005. 

Other workers have prepared poly(V-methylpyrrole)/poly(biphenol-A-carbon-ate) (PC) using this approach.68 The electrodes were dip-coated with the PC and then electropolymerization was induced. Thermogravimetric analysis verified that a graft copolymer was produced. A similar procedure has been used to prepare PAn composites with the same host polymer.69 The in situ electrochemical polymerization process has also been used to prepare polyacrylonitrile/PPy composite films.70... 

Ogura K. and Shiigi H., A CO2 sensing composite film consisting of base-type poly-anihne and poly (vinyl alcohol), Electrochem. Soli-State Lett., 2, 478-480, 1999. 

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