Tailoring of Double‐Walled Carbon Nanotubes for Formaldehyde Sensing through Encapsulation of Selected Materials

Abstract

Tailoring carbon nanomaterials for specific applications is of great importance in the quest to improve the properties of these materials, increasing their functionalities. Using a simple and easy to apply technique, zinc, zinc oxide, and iodine are encapsulated and confined within double‐walled carbon nanotubes (DWNTs) whose internal diameter ranges from 1.2 to 2.5 nm. The simultaneous confinement of zinc and iodine is shown to improve the sensitivity by 100 times while, at the same time, enhancing the selectivity of DWNTs toward formaldehyde. By exploiting the p‐doping effect of iodine, carbon nanotube (CNT) networks are engineered to differentiate formaldehyde from some of the common volatile organic compounds, such as ethanol and acetone. The ability to tune the chemical selectivity and sensitivity of CNT‐based sensors through inner encapsulation of a specific material thus appears as a new possible route compared with more conventional outer surface functionalization.

Highly Rapid and Sensitive Formaldehyde Detection at Room Temperature Using a ZIF-8/MWCNT Nanocomposite

“…21 In addition, Chimowa et al tested encapsulated zinc, zinc oxide, and iodine within double-walled carbon nanotubes (CNTs) for detection of various mass concentrations of formaldehyde ranging from 1.8 to 4%. 22 In this research, we selected ZIF-8 as an acceptable sensing material for sensing formaldehyde based on the literature. However, it should be used in a composite form with some conductive or semiconductive material.…”

“…For example, Jia et al fabricated a formaldehyde sensor by ZnSnO 3 , which could detect formaldehyde at a concentration range of 5–100 ppm; however, the working temperature for this sensor was higher than 200 °C . In addition, Chimowa et al tested encapsulated zinc, zinc oxide, and iodine within double-walled carbon nanotubes (CNTs) for detection of various mass concentrations of formaldehyde ranging from 1.8 to 4% …”

Filled carbon-nanotube heterostructures: from synthesis to application

“…Yang et al further studied the temperature-dependent charge transport characteristics of Dy@C 82 peapods FET. A transition from p-type to n-type conduction has been observed as the temperature decreases from room temperature to 265 K, indicating that charge transfers from the Dy@C 82 to the conductance band of carbon nanotubes at low temperatures [Figure 9E] [23] . At a temperature lower than 215 K, metallic behavior occurred, suggesting that additional electrons are continuously injected into the conductance band, shifting the Fermi level into the conduction band.…”

“…For weakly interacting heterostructure systems, although the electron transfer is hindered, the radial vibrations of the carbon nanotubes are suppressed, causing them to deform [22] . The single CNT in discrete-filled heterostructure systems would split into a series of quantum dots [23] . Therefore, CNTs can be designed with the help of filling for particular applications, such as sensors [24] , p-n junctions [25] , transistors [26] and so forth.…”

Applications of Filled Single-Walled Carbon Nanotubes: Progress, Challenges, and Perspectives

“…There are biosensors based on pristine and functionalized SWCNTs for different biomolecules [167][168][169]. In Reference [170], double-walled carbon nanotubes (DWCNTs) filled with zinc iodide were employed as sensors for formaldehyde. This study proved that the sensitivity and selectivity of the sensors can be tunedfor better performance by filling the DWCNT.…”