Electronic Sensitivity of Carbon Nanotubes to Internal Water Wetting

Abstract

We have constructed devices in which the interior of a single-walled carbon nanotube (SWCNT) field-effect transistor acts as a nanofluidic channel that connects two fluid reservoirs, permitting measurement of the electronic properties of the SWCNT as it is wetted by an analyte. Wetting of the inside of the SWCNT by water turns the transistor on, while wetting of the outside has little effect. These observations are consistent with theoretical simulations that show that internal water both generates a large dipole electric field, causing charge polarization of the tube and metal electrodes, and shifts the valance band of the SWCNT, while external water has little effect. This finding may provide a new method to investigate water behavior at nanoscale. This also opens a new avenue for building sensors in which the SWCNT simultaneously functions as a concentrator, nanopore and extremely sensitive electronic detector, exploiting the enhanced sensitivity of the interior surface.

Electronic sensitivity of a single-walled carbon nanotube to internal electrolyte composition

“…The electronic transport measurement in air (grey curves) suggested the FET was p-type, which is “on” at negative gate voltage and “off” at positive gate voltage. After adding DI-water, the device became insensitive to the back gate voltage, keeping I ds constant for the entire range of V g (green curves) as previously reported [12]. We then studied the response of the SWCNT FET when KCl solutions with different concentrations were injected into the reservoirs sequentially in an order from low to high.…”

“…The internal wetting of semiconducting SWCNTs by pure water significantly modifies the FET characteristics [7, 12]. In contrast, external wetting has little effect.…”

Carbon nanotube-based nano-fluidic devices

“…V ds = 0.8V for both (a) and (b). (c) I ds time traces during adding water into the reservoirs for both unopened and opened tubes at V ds = 0.8 V and V gs = 10 V. 124 Studies of external wetting [117][118][119][120] have been carried out using a window opened in dielectric material that covers the metallic contacts (Figure 6.5).…”

Effects of surface morphology, size effect and wettability on interfacial adhesion of carbon nanotube arrays

“…61 and 62 is 40 and 50 nm, respectively, (2) a difference in the interstitial spaces between adjacent CNTs, and (3) system errors in the force field physical model, i.e. some uncontrollable errors might be induced due to thermal drift [69,70], electronic noise [71,72], and aperiodic resonance [73,74].…”