Bamboo-like multiwalled (b-MWCNT), hollow-tube multiwalled (h-MWCNT) and single-walled C nanotubes (SWCNT), chem. modified with 1-anthraquinonyl (AQ) or 4-nitrophenyl (NP) groups, are characterized using voltammetric, electron microscopic and Raman spectroscopic techniques. The pKa values of the AQ-modified CNTs are shifted by >3 units when compared to the pKa values of anthrahydroquinone (AHQ, the reduced form of AQ) in aq. soln. to beyond pH 14. These large changes in the surface pKa values of the modified CNTs are explored further by comparing the pKa values of CNTs modified with an anthraquinonyl-2-carboxylic acid group. These groups are attached to the CNT surface via the formation of an amide bond with an aminophenyl spacer unit derived from the chem. redn. of NP modified CNTs. The location of reactive sites on the CNT surface is studied and their influence on the pKa of the modified materials is discussed. Comparison with modified pyrolytic graphite electrodes exposing pure edge-plane or pure basal-plane crystal faces indicates that the modifying aryl groups are predominantly located on edge-plane like defects at the tube ends of MWCNTs. The effect of polymer formation on electron transfer kinetics of b-MWCNTs and h-MWCNTs is also discussed. In contrast SWCNTs show both significant side-wall functionalization and fast electron transfer kinetics which is attributed to their different electronic structure. [on SciFinder(R)

4-Nitrophenol (4-NP)or 4-nitrobenzyl alc. (4-NBA) are used as voltammetric and X-ray photoelectron spectroscopic (XPS) labels for carboxylic acid groups on the surface of single-walled carbon nanotubes, "bamboo-like" and "hollow-tube" multi-walled carbon nanotubes. The surface carboxyl groups are first converted to the corresponding acyl chlorides, and coupled to the labels via the formation of an ester linkage. The voltammetric redn. of the arylnitro label allows the no. of carboxyl groups on the surface to be estd. Alternatively the percentage of the elemental surface compn. corresponding to the carboxyl groups can be measured using XPS via the emission from the N1s level of the label. The no. of electroactive quinonyl groups present on the surface relative to the no. of carboxyl groups can also be detd. voltammetrically by measuring the area under the voltammetric wave corresponding to the surface quinone groups. By combining these voltammetric and XPS results the relative percentages of the O1s spectral peak, which correspond to carboxyl and quinonyl groups, can then be detd., which also allows, by difference, an est. of the percentage elemental surface compn. of total other oxygen-contg. functionalities present such as lactones, ethers, aliph. ketones etc. The effect of std. acid pre-treatments used to introduce carboxyl groups onto the CNT surface (such as stirring in relatively concd. mixts. of nitric and sulfuric acids) on the no. of each type of oxygen functionality is compared. In all cases the no. of carboxyl groups is found to increase, but the no. of quinonyl and other oxygen-contg. functionalities is also found to increase, often to a greater extent than the carboxyl groups. [on SciFinder(R)

A facile and rapid method of covalently modifying the surface of graphite powders with aminophenyl groups is described. This chem. modification strategy gave bulk quantities of amino-modified C powder. 4-Nitrophenyl groups are covalently attached to graphite powder via the chem. redn. of the corresponding 4-nitrobenzenediazonium tetrafluoroborate salt using aq. hypophosphorous acid. The 4-nitrophenyl groups on the C surface are then reduced to the corresponding 4-aminophenyl groups using alk. Fe(II) ammonium sulfate solns. Electrochem. and x-ray photoelectron spectroscopic characterization is carried out at each stage of the synthesis. [on SciFinder(R)

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