Humidity Sensing Behavior of Endohedral Li-Doped and Undoped SWCNT/SDBS Composite Films.

Christian Müller,Olfa Kanoun,José Mauricio Rosolen,Mahfujur Rahaman,Elaine Yoshiko Matsubara,Dietrich R T Zahn,Ammar Al-Hamry

doi:10.3390/s19010171

Abstract

We have investigated single-walled carbon nanotube (SWCNT) networks wrapped with the cationic surfactant sodium dodecyl-benzenesulfonate (SBDS) as promising candidates for water detection. This is the first time that the humidity behavior of endohedral Li-doped (Li@) and undoped SWCNTs/SDBS has been shown. We identified a strong and almost monotonic decrease in resistance as humidity increased from 11 to 97%. Sensitivities varied between −3 and 65% in the entire humidity range. Electrical characterization, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) analysis revealed that a combination of the electron donor behavior of the water molecules with Poole-Frenkel conduction accounted for the resistive humidity response in the Li@SWCNT/SDBS and undoped SWCNT/SDBS networks. We found that Li@SWCNTs boosted the semiconducting character in mixtures of metallic/semiconducting SWCNT beams. Moreover, electrical characterization of the sensor suggested that endohedral Li doping produced SWCNT beams with high concentration of semiconducting tubes. We also investigated how frequency influenced film humidity sensing behavior and how this behavior of SWCNT/SDBS films depended on temperature from 20 to 80 C. The present results will certainly aid design and optimization of SWCNT films with different dopants for humidity or gas sensing in general.

Highlights

IntroductionDifferent materials, including carbon nanotubes (CNTs) [4,5], graphene [6], graphene oxide [7,8], carbon nitride [9], metal oxides [10], polymers and nanocomposites [11,12], have been explored for humidity sensing
Humidity sensors are highly important in many industrial fields, such as automobile industry, environmental monitoring, food production, health monitoring and production processes [1,2,3].To date, different materials, including carbon nanotubes (CNTs) [4,5], graphene [6], graphene oxide [7,8], carbon nitride [9], metal oxides [10], polymers and nanocomposites [11,12], have been explored for humidity sensing
We analyzed the structural properties of single-walled carbon nanotube (SWCNT) and Li@SWCNTs dispersed in SBDS by Raman spectroscopy (Figure 3)

Summary

Introduction

Different materials, including carbon nanotubes (CNTs) [4,5], graphene [6], graphene oxide [7,8], carbon nitride [9], metal oxides [10], polymers and nanocomposites [11,12], have been explored for humidity sensing. Among these materials, CNTs have gained great interest because of their excellent mechanical robustness, electrical conductivity, and chemical stability [13]. Zhao et al [31]

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