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The difference between the values of 4-carboxyphenyl groups, covalently attached to either graphite (BAcarbon) or glassy carbon (BA-GC) surfaces, and benzoic acid in solution is explored using potentiometric titration and cyclic voltammetry. In solution, benzoic acid has a pKaof 4.20 at 25 °C. However, the observed pKavalue on the graphitic surfaces shows significant deviations, with BAcarbon exhibiting a large shift to higher pKavalues (pKa6.45) in contrast to BA-GC, which is shifted to lower pKavalues (pKa3.25). Potentiometric titrations at temperatures between 25 and 50 °C allowed us to determine the surface pKaof these materials at each temperature studied and hence to determine the enthalpy, entropy, and Gibbs' energy changes associated with the ionization of the carboxylic acid groups. It was found that the enthalpic contribution is negligible and that the changes in surface pKavalues are entropically controlled. This suggests that solvent ordering/disordering around the interface strongly influences the observed pKavalue, which then reflects the relative hydrophobicity/hydrophilicity of the different graphitic surfaces. [ABSTRACT FROM AUTHOR]

A synthesis of graphite powder covalently modified with gallic acid (3,4,5-trihydroxybenzoic acid), via a 1,2-diaminoethane “linker” molecule, to form gallylaminoethylaminocarbonyl graphite (gallic-carbon) is reported. The synthesis was used as a model for a “ground-upwards building-block” approach to a primary dendrimer of gallic acid covalently attached to the surface of graphite powder, tris-(O-gallyl)-gallylaminoethylaminocarbonyl graphite (TGGA-carbon). The resulting modified carbon materials were characterized at each stage of the syntheses using X-ray photoelectron spectroscopy (XPS) analysis. The effects of increasing the modifier’s structural complexity from monomeric gallic-carbon to the analogous primary dendrimer TGGA-carbon were explored by comparing each material’s efficacy toward the adsorption of Al(III) ions from water. The uptake of Al(III) ions by gallic-carbon and TGGA-carbon was measured using UV−vis spectroscopy. In comparison to the case of monomeric gallic-carbon, the rate of adsorption of Al(III) ions by the TGGA-carbon was found to be 2.3 times more rapid. Furthermore, the total uptake of Al(III) ions was greater (reducing the concentration of 1000 ppb Al(III) solutions to below the WHO legal limit of 100 ppb in less than 5 min) and irreversible, in contrast to the gallic-carbon where the adsorption was found to be under thermodynamic control and to follow a Freundlich isotherm. [ABSTRACT FROM AUTHOR]

ortho-Quinones can be differentiated from other oxygen-containing surface functional groups on the surfaces of graphite, glassy carbon, “bamboo-like”, and “hollow-tube” multiwalled carbon nanotubes and single-walled carbon nanotubes by chemically labeling them with either an inorganic hexamminechromium(III) complex or organic 1,2-phenylenediamine derivatives. Both types of labels can be observed using cyclic voltammetry or by X-ray photoelectron spectroscopy and used to quantify the numbers and relative distribution of ortho-quinones from other oxygen-containing species on the surface including electroactive para-quinones which are not labeled. Labeling of ortho-quinones with 1,2-phenylenediamine derivatives results in the formation of phenazine-like adducts on the graphitic surface which have a distinct voltammetry particularly from that of the underivatized para-quinones. [ABSTRACT FROM AUTHOR]

Carbon nanotubes, even after extensive posttreatment, contain metallic impurities which may produce misleading results, giving rise to false claims of the properties of carbon nanotubes. To overcome this, we report on high-purity catalyst-free multiwalled carbon nanotubes which have been explored with transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry using the electrochemical oxidations of hydrazine and potassium ferrocyanide. The multiwalled carbon nanotubes are approximately 150 nm in length and consist of 6−10 graphite layers. Due to the definitive absence of metallic impurities, experimentalists using these carbon nanotubes can avoid potential misinterpretations of their results. [ABSTRACT FROM AUTHOR]

The mechanical stability of gold microparticles during anodic stripping voltammetric (ASV) detection over a large range of mercury concentrations was investigated. Mercury was detected at gold microparticles chemically deposited onto glassy carbon microspheres using ASV. Oxidation was observed at 0.5 and 0.8 V vs. SCE. Which peak was observed was dependent on the concentration of mercury and the deposition potential. The formation of the amalgam was of interest. As mercury was deposited for longer time intervals, scanning electron microscopy (SEM) analysis showed the microparticles increasing in size from 0.76 ± 0.03 μm (initial) to 1.51 ± 0.14 μm (Hg2+ deposited for 1980 s at 0.35 V) in diameter. In order to ascertain if multiple expansion and contraction cycles damaged the gold microparticles, cyclic voltammetry was used to monitor the amount of gold on the electrode as mercury was deposited and stripped repeatedly. It was seen that the area under the cathodic gold peak decreased with repetitive scans. SEM analysis revealed that the mechanical stress of repetitive deposition and stripping cycles of mercury caused the gold microparticles to fracture, appearing as irregular cuboid crystals rather than as the orderly polycrystallite formations seen initially. Energy dispersive X-ray (EDX) analysis indicated that the composition of the microparticles changed over the course of repetitive deposition and stripping cycles from gold to an Au–Hg amalgam, which may not be in electrical contact with the carbon support. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of 1-butyl-3-methylimidazolium nitrate [C4mim][NO3] was studied by cyclic voltammetry in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C2mim][NTf2]. A sharp peak was observed on a Pt microelectrode (d = 10 μm), and a diffusion coefficient at infinite dilution of ca. 2.0 × 10−11 m2 s−1 was obtained. Next, the cyclic voltammetry of sodium nitrate (NaNO3) and potassium nitrate (KNO3) was studied, by dissolving small amounts of solid into the RTIL [C2mim][NTf2]. Similar oxidation peaks were observed, revealing diffusion coefficients of ca. 8.8 and 9.0 × 10−12 m2 s−1 and solubilities of 11.9 and 10.8 mM for NaNO3 and KNO3, respectively. The smaller diffusion coefficients for NaNO3 and KNO3 (compared to [C4mim][NO3]) may indicate that NO3− is ion-paired with Na+ or K+. This work may have applications in the electroanalytical determination of nitrate in RTIL solutions. Furthermore, a reduction feature was observed for both NaNO3 and KNO3, with additional anodic peaks indicating the formation of oxides, peroxides, superoxides and nitrites. This behaviour is surprisingly similar to that obtained from melts of NaNO3 and KNO3 at high temperatures (ca. 350–500 °C), and this observation could significantly simplify experimental conditions required to investigate these compounds. We then used X-ray photoelectron spectroscopy (XPS) to suggest that disodium(i) oxide (Na2O), which has found use as a storage compound for hydrogen, was deposited on a Pt electrode surface following the reduction of NaNO3. [ABSTRACT FROM AUTHOR]

Monodisperse, size-controlled Ni–P nanoparticles were synthesised in a single step process using triphenyl-phosphane (TPP), oleylamine (OA), and Ni(ii)acetyl-acetonate. The nanoparticles were amorphous, contained ∼30 at% P and their size was controlled between 7–21 nm simply by varying the amount of TPP. They are catalytically active for tailored carbon nanotube growth. [ABSTRACT FROM AUTHOR]

The sidewall functionalisation of carbon nanotubes using the standard nitric acid treatment can be greatly enhanced by first removing the amorphous carbon present in the sample. [ABSTRACT FROM AUTHOR]

X-Ray Photoelectron Spectroscopy (XPS) was used to quantify the amount of bromide ions present in two samples of [C4mpyrr]Br dissolved in the room temperature ionic liquid (RTIL) [C4mpyrr][N(Tf)2]. One sample was of a known concentration (0.436 Br atom%); the other was a saturated solution. The results obtained from quantitative XPS analysis indicated that the saturated sample had a concentration, or solubility, of 0.90 Br atom% (746 mM) at 298 K, which was then independently confirmed by potential-step chronoamperometry of the same solution. [ABSTRACT FROM AUTHOR]