Preparation And Electrochemical Study Of Carbon Nanotube Electrodes Modified With Layered Double Hydroxides-Intercalation Compounds

Carbon nanotubes (CNTs) as important class of one dimensional nanostructure have attracted much attention due to their unique large surface area, high aspect ratio, electronic and chemical properties. Numerous novel applications of CNTs have been investigated including nanocomposites, nanoelectronic devices, chemical sensors and biological fields. But the surface of CNTs does not have abundant functional groups and poor dispersibility of CNTs in solvents, the modification of CNTs surface by physical bonding and chemical bonding is an effective method to prepare CNTs electrodes. Especially it enlarges the application in the electrochemical analysis after the modification of CNTs with inorganic nanaoparticals, polymers, protein and amino acid biomolecules.Layered double hydroxides (LDH), also known as anionic or hydrotalcite like clays, have becomes as attractive materials for electrochemical sensors owing to large adsorption, good biocompatibility, good chemical stability and high catalytic activity. However LDH nanoparticacles aggregate to each other and less catalytic sites, limit their wide application in electrochemistry. For those restrictions, immobilizations of electroactive materials into the layers of LDHs and acquisition the high dispersibility of LDHs with vactors have been developed. Aiming at a synergetic combination of outstanding physicochemical properties of two types of functional CNT and LDH materials and thus enhanced performance to meet advanced applications, in this contribution, we established a facile noncovalent modification for poly acrylic acid (PAA)-functionalized CNTs with electroactive species intercalation LDHs. Also the electrochemical performance of the electrodes modified with the nanocomposites is also studies.PAA was used to functionalize the surface of CNTs, and functionalized CNTs were further modified successfully with ZnAl-LDH through the electrostatic interaction between the positively charged layers of LDH and the negatively charged functional groups (-COO-) of PAA chains enwinding CNTs. Because of the addition of the CNTs, the dispersability and stability of LDHs are improved. And the CNTs have the ability to promote electro-transfer velocity during electrochemical reactions. The influence of the amount of LDH on the electrocatalytic efficiency of modified electrodes was investigated. The electrochemical investigation indicated that the LDH-PCNT modified electrodes exhibited excellent electrocatalytic activity toward the oxidation of catechol. Furthermore, such modified electrode could effectively distinguish catechol from its isomers with high sensitivity.Fluorescein (Fl) dye is also play the role of promoter during the electrochemical reactions, so we prepared the LDH-intercalation compounds with the F1 and surfactants. The amount of Fl can be controlled by the co-intercalated surfactants. Then Fl-intercalated LDH composites has successfully attached on the surface of PAA-grafted CNTs by a one-step co-precipitation method. Furthermore, the use of the LDH-F1-PCNTs nanocomposite modified electrodes was investigated for the oxidation properties of DA. The results showed that pH largely affected the Fl-intercalation compounds, the electroactive LDH-F1 retain morphologically hexagon-like, the LDH-F1 can disperse on the surface of CNTs. The modified electrode shows an interesting property that could detect dopamine with high sensitivity and low detection limit with the promoter combination of the Fl and CNTs.Fe(CN)63- ion, which is well known as an electrocatalytic activity substance, is selected to prepare intercalation compounds with the LDH. And PCNTs was further modified by LDH-Fe (CN) 63- through coprecipitation. After the preparation, the new composite materials are casted on the electrode surface, and the properties of the electrocatalytic oxidation of ascorbic acid are studied. The electroactive composites show good electrocatalytic activity on the detection of the ascorbic acid. Among the electrochemical tests, it was also found that when the mass ratio of LDHs and CNTs is 1:0.3, the peak current response reaches the largest. Meanwhile, the modified electrodes exhibit a higher affinity and sensitivity for ascorbic acid.