Magnetically Aligned Iron Oxide/Gold Nanoparticle-Decorated Carbon Nanotube Hybrid Structure as a Humidity Sensor

Abstract

Functionalized carbon nanotubes (f-CNTs), particularly CNTs decorated with nanoparticles (NPs), are of great interest because of their synergic effects, such as surface-enhanced Raman scattering, plasmonic resonance energy transfer, magnetoplasmonic, magnetoelectric, and magnetooptical effects. In general, research has focused on a single type of NP, such as a metal or metal oxide, that has been modified on a CNT surface. In this study, however, a new strategy is introduced for the decoration of two different NP types on CNTs. In order to improve the functionality of modified CNTs, we successfully prepared binary NP-decorated CNTs, namely, iron oxide/gold (Au) NP-decorated CNTs (IA-CNTs), which were created through two simple reactions in deionized water, without high temperature, high pressure, or harsh reducing agents. The physicochemical properties of IA-CNTs were characterized by ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, a superconducting quantum interference device, scanning electron microscopy, and transmission electron microscopy. In this study, IA-CNTs were utilized to detect humidity. Magnetic IA-CNTs were aligned on interdigitated platinum electrodes under external magnetic fields to create a humidity-sensing channel, and its electrical conductivity was monitored. As the humidity increased, the electrical resistance of the sensor also increased. In comparison with various gases, for example, H2, O2, CO, CO2, SO2, and dry air, the IA-CNT-based humidity sensor exhibited high-selectivity performances. IA-CNTs also responded to heavy water (D2O), and it was established that the humidity detection mechanism had D2O-sensing capabilities. Further, the humidity from human out-breathing was also successfully detected by this system. In conclusion, these unique IA-CNTs exhibited potential application as gas detection materials.

3D Printing‐Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

“…[83][84][85] As a result, their conduc tivity and sensitivity would be orders of magnitude higher than even the best randomly dispersed states of nanoparticles, significantly improving performances of electrodes, superca pacitors, transistors, sensors, actuators, heat exchangers, ther moelectrical converters, optics, and biomedical devices. [86][87][88] The assembly of nanoscale particles can learn from macro scale manufacturing. Traditionally, continuous carbon fibers (CFs) or GF reinforced polymer matrix depends on fiber ori entations for tailored composite mechanics.…”

Gold-carbonaceous materials based heterostructures for gas sensing applications

“…Jaewook et al 160 demonstrated the binary type of NP-CNT composite for humidity sensors using a simple physiochemical method. In a two-step process, rstly positive charge bearing Au particles stacked on the surface of CNT and then gallic acid-modied iron oxide NPs (GA-IONPs) which act as reducing agent to synthesize Au NPs and while mixing with CNT-Au 3+ solution both metal nanoparticles attach on CNT surface through pi-pi interactions (IA-CNT).…”

Synthesis of Heterocyclic Compounds Catalyzed by Metal/Metal Oxide-Multiwall Carbon Nanotube Nanocomposites

“…They are used as electrochemiluminescence sensors for the detection of diphenhydramine hydrochloride, humidity sensors, impedimetric immunosensors, electrocatalytic detectors, etc. They are also used in various chemical transformations, some of which are listed in Table .…”