Quantifying Single-Carbon Nanotube–Electrode Contact via the Nanoimpact Method

Abstract

A new methodology is developed to enable the measurement of the resistance across individual carbon nanotube-electrode contacts. Carbon nanotubes (CNTs) are suspended in the solution phase and occasionally contact the electrified interface, some of which bridge a micron-sized gap between two microbands of an interdigitated gold electrode. A potential difference is applied between the contacts and the magnitude of the current increase after the arrival of the CNT gives a measure of the resistance associated with the single CNT-gold contact. These experiments reveal the presence of a high contact resistance (∼50 MΩ), which significantly dominates the charge-transfer process. Further measurements on ensembles of CNTs made using a dilute layer of CNTs affixed to the interdigitated electrode surface and measured in the absence of solvent showed responses consistent with the same high value of contact resistance.

Understanding gold nanoparticle dissolution in cyanide-containing solution via impact-chemistry

“…For potentials in the range of 0.5 to 0.8 V, the rate constant is approximately independent of potential, whilst for the range of 0.8 to 1.0 V it is higher (Figure 7(b Figure 3 and Figures 6 and 7 shows that significantly higher potentials are required for particle oxidation in the case of impactchemistry over ensembles. This likely reflects partly a high electrical contact resistance in the case of solution phase impacts as compared to dried drop casted deposits as noted in related cases through direct measurement of contact resistance via "bridging" impacts 54 , coupled with a possible loss of driving force for electron transfer resulting from the capping agent (citrate) on the particles and also possibly from oxide layer formation. Assuming a significant contact resistance, the two kinetic regimes evidenced in Figure 7 might be tentatively attributed to the change in rate-determining step identified by Kirk et al 49 and discussed above on the basis of reaction 3, 4 and 5.…”

Impact electrochemistry reveals that graphene nanoplatelets catalyse the oxidation of dopamineviaadsorption

“…For the duration of the impact the conducting particle may act as a tiny electrode with the same potential of the impacted microelectrode and hence electrochemistry can be observed exclusively during the duration of the impact if the redox process studied occurs selectively on the particle rather than the electrode. 15 , 16 Thus by careful choice of the electrode material, the electrochemistry at single particles can be observed. In particular if an electrochemical response is seen during the ‘nano-impact’ and not on the substrate electrode then clearly the process is more favoured – thermodynamically and/or kinetically – on the material of the particle than that of the electrode so providing a very easy, qualitative assessment of the relative catalytic behaviour of the two materials for the process of interest.…”

Individual Detection and Characterization of Non‐Electrocatalytic, Redox‐Inactive Particles in Solution by using Electrochemistry

“…An additional category could be defined and referred to as ‘bridging impacts’ as in very recent experiments by Compton et al ,. where carbon nanotubes are detected individually when landing on the sensor in such a way that they bridge a micron‐sized gap between two microbands of an interdigitated electrode.…”