Electrical response of electrospun PEDOT-PSSA nanofibers to organic and inorganic gases

https://doi.org/10.1016/j.snb.2011.02.053Get rights and content

Abstract

Electrospun isolated nanofibers of poly(3,4-ethylenedioxythiophene) doped with (poly styrene sulfonic acid)-PEDOT-PSSA were used to sense vapors of several aliphatic alcohols. Due to the large surface to volume ratio and small quantity of active material used in their fabrication, these sensors have a similar or faster response time when compared to alcohol sensors based on PEDOT. Increasing the size of the alcohol molecule leads to longer response times, which is attributed to slower diffusion of the larger molecule into the polymer. The sensors were annealed in air at 70 °C and used to sense NH3, HCl and NO2 gas. The response time for NH3 was faster than HCl, and the sensors showed a large initial response to NO2 at room temperature which is very desirable, as some NO2 gas sensors only operate at elevated temperatures. Electrospinning is a simple and inexpensive method of preparing PEDOT-PSSA nanofibers making it an attractive technique to fabricate polymer based low cost, rapid response and reusable gas sensors.

Introduction

The rapid detection of minute traces of toxic gases in an inadequately ventilated environment is crucial to effectively reduce any widespread loss to life and property. This requires sensors capable of detecting small quantities of gas, such as those fabricated using nanofibers that posses enhanced surface to volume ratio [1], [2]. Organic conducting polymers (CP's) are especially suited for use as gas sensors for a variety of reasons. In particular, the oxidation/reduction states of these polymers can be reversibly tuned by exposure to basic/acidic environments, resulting in several orders of magnitude change in the conductivity with no polymer degradation [3] and that would extend the lifetime of sensors based on these polymers. Furthermore, CP's are cheap and easy to synthesize in bulk quantities, they are relatively stable under ambient conditions and can readily be processed as films or fibers.

Poly(3,4-ethylenedioxythiophene) doped with (poly styrene sulfonic acid)-PEDOT-PSSA is one of most widely used CP's in electronic devices due to its high stability in the doped state, with conducting properties that remain unaffected with time under ambient environmental conditions [4], [5]. Several methods have been utilized in the past to obtain CP nanofibers that include the use of a template or without a template [6], [7], [8], [9], interfacial polymerization [10] and electrospinning [11], [12]. Of the aforementioned techniques, electrospinning is by far simpler, cheaper and a faster method of obtaining isolated and relatively long polymer nanofibers [13]. Here we report experiments where we used this technique to fabricate sub 50 nm diameter PEDOT-PSSA nanofibers in air, and within seconds, that are several hundreds of microns in length and used them in sensing several toxic gases. The alcohol sensing response times are comparable or faster when compared to similar sensors based on PEDOT-PSSA [14], [15], [16], [17], [18] that either had thicker fibers, fiber mats or patterned films as the active sensing material. Annealing a nanofiber sensor makes it reusable to detect a variety of gases. The advantage of using a single nanofiber chemical sensor is its small size and potential for higher sensitivity. Finally, the ability to prepare long nanofibers of PEDOT-PSSA via electrospinning that have a large aspect ratio and an even larger surface to volume ratio, makes this technique very attractive for use in the fabrication of cheap, low power consumption and rapid response gas sensors.

Section snippets

Experimental

PEDOT-PSSA was purchased from Bayer Corp. (Baytron® P) and used as received. A 1 wt.% of polyethylene oxide (PEO-plasticizer) in PEDOT-PSSA was prepared and the solution used to fabricate nanofibers via electrospinning. The basic elements of the electrospinning apparatus consists of a hypodermic syringe (1/2 cm3 tuberculin syringe), a high voltage power supply (Gamma Research), a grounded cathode (Al foil) and a syringe pump (Cole Parmer). About 0.5 ml of the solution was placed in the hypodermic

XRD measurements

Fig. 2 shows the XRD spectra of a thin cast film of PEDOT-PSSA and of electrospun PEDOT-PSSA nanofibers. The main diffraction peak occurs at ∼13° (d-spacing of 6.8 Å) rather than ∼26° as seen by others [9], [19] and could be due to the presence of the dopant PSSA anion that increases the inter-chain packing distances in PEDOT-PSSA. Although PEDOT salt structures have been successfully investigated by XRD, PEDOT-PSSA studies only show broad amorphous peaks similar to those in Fig. 2. The presence

Conclusions

Sub 50 nm diameter nanofibers of commercially available PEDOT-PSSA were electrospun in air. XRD results on a cast film and on electrospun fibers of the polymer show no significant difference in their structure. Individual nanofibers were used as sensors and tested in the presence of various aliphatic alcohol vapors and water vapor. As a result of polymer swelling, the sensor resistance increases in the presence of these vapors. Due to the large surface to volume ratio and small quantity of

Acknowledgements

This work was supported in part by NSF under grants DMR-PREM 0934195 and DMR-RUI 0965023. J.H.L. and A.T.J. acknowledge support from the NSF under grant DMR0805136.

Nicholas J. Pinto is a professor in the Department of Physics and Electronics at the University of Puerto Rico, Humacao Campus. He has a BSc (1985) in physics from Bombay University, an MS (1987) in physics from Bowling Green State University (OH) and a Ph.D. (1992) in physics from Montana State University (MT). His research is in the field of conducting polymers for use as gas sensors, devices and in organic electronics at the nanoscale. He is also engaged in efforts to integrate undergraduate

References (26)

  • A. Karthigeyan et al.

    Low temperature NO2 sensitivity of nanoparticle SnO2 film for work function sensors

    Sens. Actuators, B: Chem.

    (2001)
  • J. Huang et al.

    Polyaniline nanofibers: synthesis, properties and applications

  • A. Kolmakov et al.

    Detection of CO and O2 using tin oxide nanowire sensors

    Adv. Mater.

    (2003)

    • Cited by (33)

    • A comparative study between vapor phase polymerized PPy and PEDOT - Thermoplastic polyurethane composites for ammonia sensing

      2021, Polymer
      Citation Excerpt :

      The sensing mechanisms of CPs greatly depend on the change in conductivity, which is influenced by the modulation of redox rates and partial charge transfers [59]. The diffusion of NH3 into the PEDOT layer dedopes the conducting polymer, therefore causing the formation of a neutral backbone, resulting in a decrease in the number of charge carriers which in turn results in a significant drop in conductivity [60,61]. PEDOT also exhibited a total adsorption [55], wherein it irreversibly changed resistance during the NH3 sensing, but the change in resistance was dependent on the NH3 concentration.

    • PEDOT-PSS nanoribbon and cast film field effect transistors with ferroelectric gating

      2019, Synthetic Metals
      Citation Excerpt :

      It is a water soluble complex that is chemically stable under normal laboratory conditions. Nano-ribbons of this polymer were fabricated via electrospinning [13–17]. Fig. 1(a) shows the schematic diagram of the electrospinning apparatus.

    • Achieving humidity-insensitive ammonia sensor based on Poly(3,4-ethylene dioxythiophene): Poly(styrenesulfonate)

      2018, Organic Electronics
      Citation Excerpt :

      For NH3 sensing, the adsorbed electron-donating NH3 molecules on the PEDOT:PSS surface deplete the holes in the conductive film, resulting in decrease of the electrical conductivity [5]. To improve the sensitivity, especially in the low concentration range, there has been extensive research being carried out, including synthesis of various PEDOT based nanostructures in rods [9], tubes [10] and fibers [11], or through physical mixing of PEDOT:PSS with conductive nanostructures such as carbon nanotubes [12,13], graphene [14,15] and silver nanowires [3]. Meanwhile, PEDOT:PSS also presents high sensitivity and reversible electrical properties when exposed to changing humidity, and has thus been regarded as ideal material for humidity sensing applications [16,17].

    • Ionic liquid gel gated electro-spun poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) nano-ribbon

      2017, Thin Solid Films

    • Monolayer WS<inf>2</inf> crossed with an electro-spun PEDOT-PSS nano-ribbon: Fabricating a Schottky diode

      2016, Materials Science and Engineering: B

    • Electrospinning of magnesium-ion linked binder-less PEDOT:PSS nanofibers for sensing organic gases

      2015, Sensors and Actuators, B: Chemical
      Citation Excerpt :

      Electrospinning, one well-known technique, which exhibits a unique ability to produce diverse forms of polymer fibers, provides a facile approach to continuously prepare highly porous polymer films with remarkably high surface-to-volume ratios [4,7–12]. However, without adding a great amount of non-conducting carrier polymers, such as polyvinyl alcohol (PVA) [7], polyvinylpyrrolidone (PVP) [5,6], chitosan [4], and poly(ethylene oxide) (PEO) [13,14], it is rather difficult to manufacture PEDOT nanofibers using electrospinning since main chains of the conducting polymers are generally rigid, which lead poor entanglement and interactions between polymer chains. In this work, by adding a small amount of magnesium nitrate as a physical cross-linker, highly porous PEDOT:PSS (Clevios PH1000) films comprising uniform nanofibers can be successfully electrospun without heavily adding any carrier polymers.

    View all citing articles on Scopus

    Nicholas J. Pinto is a professor in the Department of Physics and Electronics at the University of Puerto Rico, Humacao Campus. He has a BSc (1985) in physics from Bombay University, an MS (1987) in physics from Bowling Green State University (OH) and a Ph.D. (1992) in physics from Montana State University (MT). His research is in the field of conducting polymers for use as gas sensors, devices and in organic electronics at the nanoscale. He is also engaged in efforts to integrate undergraduate research into the Senior Lab course.

    Danairé Rivera is an undergraduate student at the University of Puerto Rico, Humacao Campus.

    Anamaris Melendez is a laboratory technician of the Partnership for Research and Education in Materials Program in the University of Puerto Rico at Humacao. She has a BSc (2008) in physics from the University of Puerto Rico at Humacao. Her research is in the synthesis, characterization and electrical application of electrospun semiconducting nanofibers.

    Idalia Ramos is a Professor in the Department of Physics and Electronics of the University of Puerto Rico, Humacao Campus. She holds degrees in Physics and Electrical Engineering. Her current research interests are in the area of nanomaterials for sensors and actuators. She is the Principal Investigator of the NSF-Partnership for Research and Education in Materials (PREM), a collaborative program between the University of Puerto Rico and the University of Pennsylvania.

    Jong Hsien Lim is currently a junior at Swarthmore College, majoring in physics. He is interested in experimental condensed matter physics and works as an undergraduate researcher in the lab of Professor A.T. Charlie Johnson at the University of Pennsylvania. Lim's current research is focused on the transport properties of graphene nanostructures, and biomolecular functionalization of graphene devices for applications in biomedical diagnostics. He earlier research on graphene electronics led to co-authorship of the publication: “High On/Off Ratio Graphene Nanoconstriction Field Effect Transistor” (Small, 2010). Lim received the 2010 Deborah A. DeMott ‘70 Student Research and Internship Award from Swarthmore College to support his work in Johnson's lab. Previously, he worked on the flow of fluids in converging microchannels with Professor Nelson Macken at the Department of Engineering, Swarthmore College.

    A.T. Charlie Johnson has led an independent research group focused on nanostructure physics and single-molecule electronics since 1994. He has worked extensively in the science of carbon nanotubes for 12 years, making significant contributions to the understanding of thermal and electronic transport in this important nanomaterial. More recently he has been active in the area of vapor- and liquid-phase molecular sensing using functionalized nanotube field effect transistors, as well as graphene electronics and synthesis of wafer-scale graphene. He was an NSF Graduate Research Fellow and a NRC Postdoctoral Research Fellow. He has received numerous other honors, including a Packard Foundation Science and Engineering Fellowship and a Sloan Fellowship. Along with the authorship of over 130 peer-reviewed articles, Johnson holds two awarded patents, with 12 other patents submitted to the US Patent Office.

    View full text
    Copyright © 2011 Elsevier B.V. All rights reserved.