Ultrasensitive Chemical Detection Using a Nanocoax Sensor

Abstract

We report on the design, fabrication, and performance of a nanoporous, coaxial array capacitive detector for highly sensitive chemical detection. Composed of an array of vertically aligned nanoscale coaxial electrodes constructed with porous dielectric coax annuli around carbon nanotube cores, this sensor is shown to achieve parts per billion level detection sensitivity, at room temperature, to a broad class of organic molecules. The nanoscale, 3D architecture and microscale array pitch of the sensor enable rapid access of target molecules and chip-based multiplexing capabilities, respectively.

Nanocoaxes for optical and electronic devices

“…45 The performance of the device for detection of different concentrations of volatile organic compounds diluted in N 2 gas, as well as various humidity levels, was reported with an ultimate sensitivity of sub-part-per-billion for ethanol, corresponding to about 30 ethanol molecules per nanocoax, as shown in Figure 23. However, the device as described has limited chemical specificity.…”

“…Figure 2 shows a schematic along with scanning electron microscope (SEM) and transmission electron microscope (TEM) images of a single unit from an array of open-ended CNF-Al 2 O 3 -Al nanocoaxes, as reported by Zhao, et al 45 To fabricate these arrays, they deposited Al 2 O 3 and Al layers on a vertically-oriented CNF array, the latter prepared by PECVD, as first demonstrated by Chen, et al 58 As an initial coating outside the CNTs, 10 nm Al 2 O 3 was deposited by ALD to prevent potential electrical shortages between the inner and outer coax electrodes. Following this, reactive sputtering was employed to apply ~100 nm porous Al 2 O 3 by introducing O 2 during Al sputter deposition.…”

“…Other well known deposition techniques, such as ALD, CVD, PECVD and PVD were used to deposit dielectric or semiconducting material and the outer metal layer on vertically aligned CNT or carbon nanofibers (CNF) arrays to make CNT-SiN x -Cr, 48 CNT-Si-ITO, 27 CNT-Al 2 O 3 -Al 15,45 and CNT-CdTe/CdSe-ITO 25 coaxial nanostructures of different diameters.…”

A nanocoaxial-based electrochemical sensor for the detection of cholera toxin

“…It consists of two concentric electrodes separated by a dielectric or an air gap. The nanocoax has demonstrated ultrasensitive chemical detection of volatile organic compounds (Zhao et al, 2012), and exhibited nanophotonic properties as a waveguide for visible light (Merlo et al, 2014; Rybczynski et al, 2007). Recently, nanocoaxial arrays demonstrated electrochemical sensing capabilities via the detection of the redox species ferrocenecarboxylic acid (FCA) (Rizal et al, 2013).…”

Gas sensing properties and p-type response of ALD TiO2coated carbon nanotubes

“…Carbon nanotubes (CNTs) appear as an ideal support for such applications due to their intrinsic electrical properties, which can be influenced by the surrounding atmosphere. CNTs have been already employed as support for various metal oxide sensing layer [8][9][10][11][12][13][14] and a recent paper described a general sensing mechanism for SnO 2 -carbon heterostructures [15].…”