(581e) Vertically Aligned Multiwalled Carbon Nanotubes for Electrochemical Biosensing

Based on the recent achievements in carbon nanotechnology, CNTs have been considered as potential interface materials of electrochemical biosensors due to their high accessible surface area, electronic conductivity, stability, and capacity to immobilize enzymes. Moreover, aligned CNTs have an outstanding ability to mediate fast electron-transfer kinetics for a wide range of electroactive species and are suitable to be used directly as a working electrode for further modification. Vertically aligned multiwalled carbon nanotube (VAMWNTs) on the substrates has been envisioned to enhance performance of various technologically important devices such as sensors, field emitters, and organic light-emitting diodes. The organization of nanomaterials into controlled surface architectures is essential for the successful realization of multiple sensing protocols. ??Trees'' of aligned CNT in the nanoforest, prepared by self assembly, can act as molecular wires to allow electrical communication between the underlying electrode and proteins covalently attached to the ends of the SWNT. The ability of CNT to promote electron transfer reactions is attributed to the presence of edge plane defects at their end caps. Carbon nanotube-modified electrodes have also been shown to be extremely useful for circumventing surface fouling associated with the oxidation of the liberated product. Organophosphates (OPs) are a class of compounds, containing a phosphorus atom in the structure with four side chains. Multiple world-wide terrorist events associated with the threat of hazardous chemical agent proliferation, and outbreaks of chemical contamination in the food supply have demonstrated an urgent need for sensors that can directly detect the presence of dangerous chemical toxins. Organophosphorus hydrolase (OPH) using in this paper is an enzyme that exhibits the ability to hydrolyze a large variety of OP compounds. The carboxylated MWNTs were covalently attached to the silicon wafer surface using an amine linkage and OPH was covalently immobilized on the interface. This nanostructure was characterized using atomic force microscopy (AFM) visualizing vertical alignment and resonance Raman spectroscopy with FTIR spectroscopy indicating pendant carboxylic acid groups for further reaction. The electrochemistry of these VAMWNTs on Glassy carbon electrode (GCE) was investigated using 1 mM FcMeOH in 0.1 M KCl as a redox mediator; it was demonstrated that the electrodes have excellent electrochemical properties with an electron transfer. In addition to enhanced electron flow, impedance spectroscopy demonstrated the decrease of charge-transfer resistance measurements with the VAMWNTs. This nanostructure assembly was used as a sensor to detect Organophosphate compounds with high sensitivity. Additionally, this procedure can be easily extended to the immobilization of other biomolecules.