Potentiometric Online Detection of Aromatic Hydrocarbons in Aqueous Phase Using Carbon Nanotube-Based Sensors

Abstract

Surfaces made of entangled networks of single-walled carbon nanotubes (SWCNTs) display a strong adsorption affinity for aromatic hydrocarbons. Adsorption of these compounds onto the walls of SWCNTs changes the electrical characteristics of the SWCNT-solution interface. Using these features, we have developed a potentiometric sensor to detect neutral aromatic species. Specifically, we can detect online aromatic hydrocarbons in industrial coolant water. Our chromatographic results confirm the adsorption of toluene onto the walls of carbon nanotubes, and our impedance spectroscopy data show the change in the double layer capacitance of the carbon nanotube-solution interface upon addition of toluene, thus confirming the proposed sensing mechanism. The sensor showed a toluene concentration dependent EMF response that follows the shape of an adsorption isotherm and displayed an immediate response to the presence of toluene with a detection limit of 2.1 ppm. The sensor does not respond to other nonaromatic hydrocarbons that may coexist with aromatic hydrocarbons in water. It shows a qualitative sensitivity and selectivity of 100% and 83%, respectively, which confirms its ability to detect aromatic hydrocarbons in aqueous solutions. The sensor showed an excellent ability to immediately detect the presence of toluene in actual coolant water. Its operational characteristics, including its fast response, low cost, portability, and easy use in online industrial applications, improve those of current chromatographic or spectroscopic techniques.

Carbon nanotubes versus polyaniline nanoparticles; which transducer offers more opportunities for designing a stable solid contact ion-selective electrode

“…These results correspond fairly well with the previously published results on solid contacts electrodes based on carbon nanotubes [25,26] and PANI [27,28] where the potential drift was almost in the range of 1.0 mV h −1 .…”

Applications of nanomaterials in potentiometric sensors

“…The change in electrical characteristics of SWCNTs makes them suitable for potentiometric detection. For example, Rius et al [75] used SWCNTs as a receptor layer to develop a potentiometric sensor for detecting neutral aromatic hydrocarbon in aqueous solutions with low ionic strength. The sensing mechanism is that the adsorption of aromatic hydrocarbons onto the side walls of the CNTs through hydrophobic and p-p stacking interactions could lead to the change of the interfacial double-layer capacitance between the CNTs and the sample solution and subsequently influence the potential response.…”

Electroanalytical Sensor Technology

“…The use of molecularly imprinted polymers (MIPs) has been greatly increasing in ISEs [148][149][150][151]. For example, Liang et al [148] report the use of a polymeric membrane ISE to detect neutral molecules, utilising a MIP, as the sensing element and an indicator ion that is similar in structure to the targeted neutral species.…”