PANI-gold

The detection of DNA hybridization using electrochemical readout is particularly attractive for the development of clinical diagnostics. The use of nanostructured materials in electrical detection for biomolecular sensing offers unique opportunities for electrochemical transduction of DNA sensing events. Tian and co-workers [175] have reported that PANI/Gold nanoparticle multilayer films electrocatalyze the oxidation of nicotinamide adenine dinucleotide (NADH) and detect DNA hybridization by both an electrochemical method and by surface plasmon enhanced fluorescence... 

FTO fluorine-doped tin oxide films, PVP poly(4-vinylphenol), Au-PVS/N-PANI gold electrode modified with LbL film of poly(vinyl sulfonic acid) (PVS) and nanostructurated polyaniline (N-PANI)... 

The biopolymer chitosan has also been used in combination with PANl films by Srivastava et al. [51]. They developed a modified PANI-gold electrode with immobilization of cholesterol oxidase on a chitosan matrix. First, nanocomposites of PANI and gold were prepared. After complete polymerisation, the nanocomposites were incorporated in chitosan. This mixture was then spin coated onto an indium tin oxide (ITO) glass. The success of the immobilization was assessed by cyclic voltammetry measurements that showed a lower current peak caused by the electrical hindrance of the immobilized enzyme. The biosensor was optimized for the detection of cholesterol. Cholesterol is oxidized by cholesterol oxidase which produces H2O2, that is oxidized producing electrons that are transferred to the electrodes via the redox mediator Fe(CN)6 The signal is a peak in current that increases with the cholesterol concentration. The biosensor was stable over the time and retained a 90 % cholesterol oxidase activity over two weeks. 

Tamer et al. [55] worked on the optimization of the fabrication of the composites PANI/gold nanorod for glncose detection. In this biosensor, the enzyme GOx was covalently bound to the electrode via the linker glutaraldehyde. This matrix offered a large surface to functionalize. 

Figure 8. Voltammograms of CO oxidation recorded on bulk Pt (—), Pt-PAni (—), PtRu-Pani (—) and PtSn-PAni ( ) electrodes deposited on a gold substrate (CO-saturated in 0.1 M HCIO4, v = 5 mV s, T = 20°C).

Figure J0.4 3D-UV-visible Differential Reflectance Spectra recorded in 0,5 M H2SO4 of a PAni film (0,5 pm thickness) deposited on a gold electrode (a), and of a PAni film containing tetrasulphonated cobalt phthalocyanine (b). Potential limits Er = — 0.1 V/RHE and Ea = 0.9 V/RHE v = 2 mV s T = 20 C. (Reprinted with permission from ref. 146)...

Figure 2.33 PANI-NFs/Au nanoparticle bistable digital memory device (from Table of Contents of Reference 504). (Reprinted with permission from Nano Letters, Polyaniline nanofiber/Gold Nanoparticle Nonvolatile Memory by R. j. Tseng, J. Huang, j. Ouyang et ai, 5, 6, 1077-1080. Copyright (2005) American Chemical Society)...

Coaxial PMMA/PANI composite nanofibers have also been fabricated using the electro-spinning technique and an in situ polymerization method and were then transferred to the surface of a gold interdigitated electrode to constmct a gas sensor (Figure 4.22) [102]. It was... 

The design of subtle specific methods for depositing metal NPs, e.g. [144,145] is another way to control the location of the metal deposit within the CP layer. One proposed approach involves the deposition of a thin, sacrificial Au layer on a Pt substrate, electropolymerization of PANI on the Au-plated substrate, gold oxidation in chloride solution, and finally reduction of the AuCU eomplexes entrapped in the PANI structure. Thus gold/ polyaniline free-standing eomposite films are produced [144,145]. 

In the first case, the tip serves both as monomer (and electrolyte) dehvery tool and as the cathode for the electrochemical polymerization, while the conductive substrate is the anode. The polymerized material with a well-defined pattern and shape is subsequently deposited on the substrate. Many kinds of CPNWs, e.g. PPY, PANI, and PEDOT nanowires have been prepared with this approach on (semi-)conducting substrates e.g. silicon, graphite, or gold, using STM or conductive AEM tips [17-21]. Figure 10.8 is an AFM... 

Figure 14.8 Cyclic voltammograms of glassy carbon electrodes modified with PANI hollow spheres and gold nanoparticles (A), PANI alone (B) and gold nanoparticles alone (C) in a range of concentrations of dopamine (DA) at a scan rate of 100 mV s vs. SCE. (Reprinted with permission from Langmuir, Polyaniline / Au composite hollow spheres Synthesis, characterisation, and application to the detection of dopamine by X. M. Feng, C.j. Mao, G. Yang et a ., 22, 9, 4384-4389. Copyright (2006) American Chemical Society)...

There are no reports about PANI composites with oxides of silver and gold because of the high redox reactivity of these oxides (e.g., Ag O and Au O can oxidize PANI), while PANI composites with copper oxides are known. Electrodeposition of mesoporous bilayers of PANI supported Cu O semiconducting films from lyotropic liquid crystalline phase has recently been reported by Xue et al. [16]. The control of size, morphology, and conductivity of PANI nanofibers (PANI-NFs) in PANI-NFs/CuO nanocomposites (Figure 2.1) was achieved by systematic variation of CuO loadings during the oxidative polymerization of aniline with mixture of oxidants [ammonium peroxydisulfate (APS) and sodium hypochlorite] in an acidic aqueous solution [17]. 

Deepshikha etal. have fabricated a novel nanobiocomposite bienzymatic amperometric cholesterol biosensor, coupled with cholesterol oxidase (ChOx) and horseradish peroxidase (HRP), based on the gold nanoparticle-decorated graphene-nanostructured PANI nanocomposite (NSPANI-AuNP-GR) film which was electrochemically deposited onto indium tin oxide (ITO) electrode from the nanocomposite (NSPANI-AuNP-GR) dispersion, as synthesized by in situ polymerization technique [166]. The... 

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