No abstract

Incorporating the nanoscale properties of carbon nanotubes (CNTs) and their assemblies into macroscopic materials is at the forefront of scientific innovation. The electrical conductivity, chemical inertness, and large aspect ratios of these cylindrical structures make them ideal electrode materials for electrochemical studies. The ability to assemble CNTs into nano-, micro-, and macroscale materials broadens their field of applications. Here, we report the fabrication of random arrays of CNT cross-sections and their performance as nanoelectrode ensembles (NEEs). Single ribbons of drawable CNTs were employed to create the CNT-NEEs that allows easier fabrication of nanoscale electrodes for general electrochemical applications. Surface analysis of the prepared NEEs using scanning electron microscopy showed a random distribution of CNTs within the encapsulating polymer. Electrochemical testing via cyclic voltammetry and scanning electrochemical cell microscopy revealed voltametric differences from the typical macroelectrode response with the steady-state nature of NEEs. Finally, when the NEE was employed for Pb2+ detection using square-wave anodic stripping voltammetry, a limit of detection of 0.57 ppb with a linear range of 10–35 ppb was achieved.

Cadmium (Cd) is a non-essential toxic heavy metal. Human exposure to Cd occurs from multiple sources, including diet, tobacco smoke, fossil fuel combustion, and variously contaminated environments. This work reports a rapid method for Cd 2+ detection in simulated urine samples containing glucose (GLC) and actual human urine using the electrochemical technique of square wave anodic stripping voltammetry (ASV). Electrochemical techniques for onsite analysis and detection are preferred for their quick response time, application simplicity, inexpensive instrumentation, and potential portability. This approach is a step forward towards Cd 2+ detection in biological fluids, despite their composition complexity due to possible interference of its constituents. Application of a simple, well controlled, and uniform carbon nanotube (CNT) thin film generated through spinnable CNT arrays enabled us to increase the surface area of traditional glassy carbon electrodes and made possible the detection of nanomolar concentration of Cd ions in urine samples. Employing 120s deposition time on anodic stripping voltammetry led to 1.9 nM and 324 nM limit of detection (LOD) in simulated urine and human samples, respectively. The developed method would facilitate high throughput screening of human urine samples for assessing Cd exposure in future studies.

Nanochannels, such as ion channels, are present in many biological functions and can control ion flow through the channel for cellular function. The trigger of the ion flow can be achieved through changes of pH, voltage, or others variables. Ion channels are important to studying some diseases, however, biological ion channels are embedded in fragile lipid bilayer membranes making them difficult to study. This research is focused on creating a synthetic nanochannel that employs the internal diameter of carbon nanotubes (CNTs) as pores. The CNTs are naturally hydrophobic and studies have shown fast water transport though the CNTs making them a good material for synthetic ion channels. We will assemble 107 channels in parallel to each other within a CNT fiber. This approach will allow easy assembly of the nanochannels for exploration of their capabilities and limitations. This project looks at the diameter correlation to ion dimensions as well as the size selectivity of the nanochannels. Preliminary work has been focused on electrochemical measurements that confirm flow of ions through the CNT nanochannels. Blank samples show current flow close to zero, while samples containing the CNT nanochannel show current flow higher then 4 nA.