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Polyaniline anchored MWCNTs on fabric for high performance wearable ammonia sensor DEBASIS MAITY, and Ramasamy Thangavelu Rajendra Kumar ACS Sens., Just Accepted Manuscript • DOI: 10.1021/acssensors.8b00589 • Publication Date (Web): 31 Aug 2018 Downloaded from http://pubs.acs.org on August 31, 2018
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Polyaniline anchored MWCNTs on fabric for high performance wearable ammonia sensor Debasis Maity1, Ramasamy Thangavelu Rajendra Kumar 1,2* 1
DRDO - Center for Life Sciences, Bharathiar University, Coimbatore – 64146, India.
2
Department of Nanoscience and Technology, Bharathiar University, Coimbatore - 641046, Tamil
Nadu, India. * Corresponding Author:
[email protected] ACS Paragon Plus Environment
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Abstract: Polyaniline (PANI) functionalized multiwall carbon nanotubes (MWCNTs) were prepared via in situ chemical polymerization process of aniline, in which MWCNTs were spray coated on the fabric for wearable ammonia sensor. Structural, morphological, thermal properties and wettability were analyzed by scanning electron microscope, X-ray diffraction, Raman analysis and contact angle measurement. No substantial change in base resistance of MWCNTs/PANI fabric sensor was observed for a wide range of bending (from 90° to 270°) shows excellent wearability. The sensors were exposed to 20-100 ppm ammonia vapor at room temperature. It was observed that sensing response of PANI coated MWCNTs was enhanced than MWCNTs and PANI. The sensor has the capability to detect ammonia with high sensitivity (92% for100 ppm ), excellent selectivity quick response (9 sec) and recovery time (30 sec). The lower detection limit (LOD) for the MWCNTs/PANI fabric sensor was found to be 200 ppb. The influence of humidity on sensing parameters was studied. Sensing response and resistance of sensor have shown excellent stability after one month. We observed that PANI have a dual role in enhancing flexibility as well as improve the sensor performance towards ammonia. The results reveal the potential application of fabric based sensor for monitoring NH3 gas under ambient conditions. Keywords: Wearable sensor, Flexible sensor, Ammonia sensor, MWCNTs, PANI.
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Ammonia is an essential element and source of nitrogen for the plant, animal and human life 1. Ammonia in the environment originates from the natural dead plants and animals, the breakdown of manure, and also man-made sources that include fertilizers, food technology, medical diagnosis 2–4
. According to the Occupational Safety and Health Administration (OSHA), the least amount of
ammonia which is found to be irritating to the eyes, nose, throat respiratory tract and skin of the most sensitive individuals is 50 ppm. According to Agency for Toxic Substances and Disease Registry (ATSDR), permanent lung damage has been associated with acute 500 ppm ammonia exposure along with chemical bronchitis, fluid accumulation in the lungs, chemical burns of the skin and is potentially fatal. Therefore, it is necessary to develop the ammonia sensor in the range of 20-100 ppm to take protective action against serious health effects and also to monitor ammonia concentration during industrial activities. In the last decade, metal oxide semiconductors such as SnO2, ZnO, In2O3, TiO2, and Fe2O3 have been used as a sensing material in ammonia sensing applications 5–14. Metal oxide semiconductorbased sensors require high operating temperature (100-300°C) with high power consumption and unsuitable for a flexible device. Current research trends mainly focus on the development of flexible gas sensors that can be operated at room temperature. Recently, carbon-based nanomaterials like a carbon nanotube, graphene oxide has been found to be ideal candidates for gas sensing due to its unique electrical, physical and chemical properties with excellent chemical stability
15–18
. It is possible to enhance sensitivity and selectivity of MWCNTs by surface
treatments and organic and inorganic functionalization. Recent research interests on electrically conducting polymers (such as Polypyrrole, polythiophene, and Polyaniline) in chemical sensing applications were due to the advantages in synthesis techniques and high conductivity, environmentally friendly nature that helps to function at room temperature. Polyaniline has a special attraction in different applications due to high polymerization conversion, low cost, ease in synthesis approach, high stability than other polymers19–21. As the detection of ammonia is very essential in the current scenario, there is a need to develop wearable, flexible, faster, ultra-sensitive, repeat and quick reversible on spot ammonia sensing devices which can work under ambient temperature and presser. Ammonia gas sensing at room temperature22–26using MWCNTs modified by PANI were reported and very few reports are available as flexible sensor 27–30. The existing report based on MWCNTs/PANI that was used as a sensing material for detection of ammonia gas, it was found to be less potential when it comes
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to field level sensing approach. The important parameters like selectivity, the effect of humidity and stability study were not elaborated in maximum reports. So far developed technologies about flexible sensors for ammonia detection have not performed flexibility study and effect of bending on sensing performances of the sensor is essential to ascertain them to suitability for wearable devices. In this paper, we demonstrate synthesis and fabrication of PANI on sprayed coated MWCNTs on fabric as a flexible, wearable and handheld ammonia sensor with a lower detection limit. The properties of sensing material were investigated by SEM, X-ray diffraction and Raman analysis. Wetting Properties and flexibility of sensing material also investigated for wearable and flexible device fabrication. Sensing performance of fabricated MWCNTs/PANI based fabric sensor was also studied under different humidity conditions and different bending angles. Essential sensing parameters such as sensitivity, selectivity, response and recovery time, stability, and repeatability were investigated in detail. 2. Experiment Details 2.1. Materials Ammonia disulfate, aniline, Hydrochloric acid, N, N-dimethylformamide (DMF), ethanol, methanol, ammonia, acetone, benzene, cyclohexane, toluene, and xylene were purchased from Sigma-Aldrich (India). Commercially available fabrics (material: polypropylene, type: woven fabric cross type, weight: 50 g/m, thickness about 1.5 mm) was obtained from Filter (Lab) India. 2.2. Characterization SEM images were acquired using FEI-QUANTA 200 instrument by 30 kV beam under vacuum. X-ray diffraction (XRD) measurement was obtained by X’pert Pro diffractometer with CuKα radiation in the range 5
