Humidity Sensitivity of Carbon Nanotube and Poly (Dimethyldiallylammonium Chloride) Composite Films

Abstract

This paper demonstrates a highly sensitive humidity sensor based on carbon nanotube and poly (dimethyldiallylammonium chloride) composite films. The composite film is deposited between interdigitated electrodes on a Si SiO 2 substrate through layer-by-layer self-assembly technique. The resistance stability of the composite film is effectively improved through thermal annealing, and I-V characteristic of the film exhibits a very good linear behavior. The resistance increases exponentially with relative humidity from 20% to 98%, and a much higher sensitivity in comparison with pure carbon nanotube networks is achieved. With temperature increased, the water vapor density versus RH shifts upwards, while the resistance is reduced downwards. The resistance is dependent on temperatures with a negative coefficient. The composite films with multiwalled carbon nanotubes show an adjacent sensitivity, compared with the single-walled carbon nanotube composite films. The experimental results show that the humidity sensors have a fast response and a short recovery time, and their response is reversible. A simple model is proposed to explain the change of composite film resistance with humidity. The carbon nanotubes junctions may play a more important role in the overall resistance change for water molecule absorption.Index Terms-Carbon nanotube (CNT), composite film, humidity sensitivity, layer-by-layer (LbL) self-assembly, poly (dimethyldiallylammonium chloride).

Effect of humidity on electrical properties of micro/nano-polyaniline thin films with different D-CSA doping degree

“…[25]. Therefore, the two polyelectrolytes (PDDA and PSS) were used as the electrostatic ''glue'' in the layer-by-layer self-assembly process to form stable and strong multilayer films [2]. The self-assembly process involved the following steps.…”

“…In the past years, a lot of research has been focused on development of humidity sensitive materials such as carbon nanotube [2], graphene oxide [3], Manganese tungsten oxide (MnWO 4 ) [4], Zinc oxide (ZnO) [5], polyaniline (PANI), polypyrrole (PPY) and polythiophene (PTH) [6,7]. Meanwhile, mature products based on the silicon cup can be used as a novel sensor with humidity sensing films [8].…”

Highly sensitive, room temperature gas sensor based on polyaniline-multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite for trace-level ammonia detection

“…Thus, during physisorption, a net charge transfer from NH 3 molecules to MWCNT/PANI occurs leading to the localization of polarons in MWCNT/PANI which result in increase in resistance. Apart from this, swelling of the PANI upon adsorption of NH 3 molecules can deteriorate the degree of connectivity in the nanocomposites and also could result in increase in resistance of MWCNT/PANI nanocomposites[50][51]. As these intermolecular interactions being generally weak forces, it is easy to desorb the physisorbed gas molecules without application of any external energy.…”

“…complex proton exchange mechanism[5,[50][51][52][53][54][55]. As the water molecules are ionisable, dissociate into proton (H + ) and hydroxyl ions (OH − ).…”

Enhanced performance of core-shell structured polyaniline at helical carbon nanotube hybrids for ammonia gas sensor

“…When exposed to NH 3 , the protons on -NH-groups on PANi would be transferred to NH 3 molecules to form ammonium ions (NH 4 þ ) while PANi itself turned into its base form. 28 Besides, charge would transfer from NH 3 molecules to PANi@HCNTs, which led to the localization of polarons of PANi@HCNTs, 28,29 which might change the resistance. As shown in Fig.…”