Carbon nanotubes-based cues: A pathway to future sensing and detection of hazardous pollutants

In the past few years, nanostructured materials-based sensing cues have gained high research interests for a variety of sensing and detection processes. Among them, carbon nanotubes (CNTs) are the emerging class of nano structured materials for the development of chemical sensors to monitor human and environmental health. In addition, CNTs offer unique multifunctional features such as great surface-to-volume ratios, outstanding chemical and tunable physical properties. However, the elucidation of the detection processes, selectivity, and sensitivity of the CNT-assisted chemical sensors is a challenging task. Herein, we reviewed an array of CNTs-based chemical sensors and their unique environmental perspectives to monitor various pollutants of high concern. Following a brief introduction, the first part of the review focuses on the sensing mechanisms of CNTs-based chemical sensors and their tunable functionalization via covalent, noncovalent, and polymers-based wrapping of CNTs. In addition, we discuss the influencing parameters that can affect the sensing capabilities such as selectivity, sensitivity, coordination interaction, and detection mechanism. Furthermore, this review elucidates the sprawling applications of nanostructured chemical sensors for the detection of a variety of environmental pollutants including, gaseous, liquid/vapor phase and heavy metal with the help of electrochemical, field-effect transistors and optical sensors. The nanoelectrode/microelectrode, electrodes decorated with nanoparticles as arrays and electrochemical sensors are discussed. Additionally, the coordinating strategies between various analytes and nanostructured material that impart the molecular interactions and selectivity between the analyte and selector are discussed. Finally, a brief outlook in the field of nanostructured electrochemical/chemical sensors with special emphasis on their commercialization has also been presented in this review. (C) 2019 Elsevier B.V. All rights reserved.