Carbon-Based Nanosensors for Microdomain Interrogation

Abstract

Nanosensors consisting of carbon-based nanostructures (CNS) enable the study of physical, chemical, and biological phenomenon occurring in microdomains. One approach for producing such sensors employs template-based nanomanufacturing processes, where carbon nanostructures are formed inside nanoporous templates. In this work, template-based nanomanufacturing was utilized as the foundation to produce two distinct sensors at the tips of pulled glass capillaries: a nanoscale thermocouple and self-contained electrochemical nanosensor. The initial manufacturing steps were the same for both sensors. Briefly, pulled quartz theta capillary templates were prepared, carbon was deposited on the templates via chemical vapor deposition (CVD), and templates were wet-etched at their tips to expose CNS. The resulting device consisted of two distinct CNS within a sub-500 nm tip connected to conductive carbon conduits running the length of the pulled glass capillary. To form the thermocouple, gold and nickel were electroplated onto the CNS scaffold. The configuration and material selection provided a thermoelectric power of 14.9 μV·K-1, a significant improvement over other micropipette-based thermocouples. To form the electrochemical sensor, one of the two CNS was electroplated with silver and chlorinated to serve as a pseudoreference electrode. With the working and reference electrodes positioned within 50 nm of each other, the overall sensor footprint was minimized in order to perform self-contained electrochemistry inside aqueous microdroplets. These CNS sensors were designed to readily integrate into standard laboratory equipment, promoting broad utilization. Figure 1