No abstract

Single Wall Carbon Nanotubes (SWCNTs) have been successfully functionalized by electrochemical oxidation in presence of 4-aminophenyl phosphonic acid (4-APPA).Electrochemical modification has been performed by cyclic voltammetry using different upper potential limits, producing the incorporation of N and P functionalities on SWCNT through polymerization reactions, although some covalent attachment cannot be discarded. Electrochemical oxidation in presence of CNT produces polymerization of 4-APPA, what has been related to the interaction between monomer and the CNT surface.The voltammograms of the functionalized SWCNT show different well-defined redox processes that are maintained at high pH. Raman spectroscopy shows that the structure of the SWCNT is maintained even at high potentials suggesting that oxidation selectively occurs in the 4-APPA monomer favoring polymer chain growth. The degree of modification of SWCNT can be easily controlled by selecting the electrochemical conditions.

Different functionalized Multi-Wall Carbon Nanotube and gold nanoparticles (AuNPs) were synthesized as biosensor electrodes. These materials have been applied to the detection of the Prostate Specific Antigen (PSA). The synthesis of AuNPs was carried out using polyvinylpyrrolidone (PVP) as protecting agent. The PVP/Au molar ratio (0.5 and 50) controls the nanoparticle size distribution, obtaining a wide and narrow distribution with an average diameter of 9.5 and 6.6 nm, respectively. Nanoparticle size distribution shows an important effect in the electrochemical performance of the biosensor, increasing the electrochemical active surface area (EASA) and promoting the electron-transfer from the redox probe (Ferrocene/Ferrocenium) to the electrode. Furthermore, a narrow and small nanoparticle size distribution enhances the amount of antibodies immobilized on the transducer material and the performance during the detection of the PSA. Significant results were obtained for the quantification of PSA, with a limit of detection of 1 ng·ml −1 and sensitivities of 0.085 and 0.056 μA·mL·ng −1 for the two transducer materials in only 5 min of detection.

Electrochemical functionalization of pristine Multiwall Carbon Nanotube (MWCNT) and oxidized MWCNT with 4-aminophenyl phosphonic acid (4-APPA) has been studied. Electrochemical modification has been carried out by cyclic voltammetry using different upper potential limits, what results in the incorporation of N and P functionalities through polymerization and covalent attachment. The electrochemical characterization shows that there are important differences among the functionalized materials derived from the pristine MWCNT or the oxidized materials. For the pristine MWCNT, well-defined redox processes are observed. Characterization by X-Ray photoelectron spectroscopy, Raman spectroscopy and electron microscopy, show that oligomerization is easier for the pristine MWCNT and the presence of polymer chains are clearly distinguished for the lowest oxidation potentials. However, the presence of surface oxygen groups in the oxidized MWCNT modify the interaction of the 4-APPA with the surface promoting mainly covalent attachment.

In this study, the phosphonation of a polyaniline (PANI) backbone was achieved in an acid medium by electrochemical methods using aminophenylphosphonic (APPA) monomers. This was done through the electrochemical copolymerization of aniline with either 2- or 4-aminophenylphosphonic acid. Stable, electroactive polymers were obtained after the oxidation of the monomers up to 1.35 V (reversible hydrogen electrode, RHE). X-ray photoelectron spectroscopy (XPS) results revealed that the position of the phosphonic group in the aromatic ring of the monomer affected the amount of phosphorus incorporated into the copolymer. In addition, the redox transitions of the copolymers were examined by in situ Fourier-transform infrared (FTIR) spectroscopy, and it was concluded that their electroactive structures were analogous to those of PANI. From the APPA monomers it was possible to synthesize, in a controlled manner, polymeric materials with significant amounts of phosphorus in their structure through copolymerization with PANI.