Achieving cost-effective and defect-free graphene sheets is highly desirable for sensor devices. Aiming this, few-layer graphene (~ 3) sheets are prepared by an electrochemical exfoliation with [NMP] [ HSO4] electrolyte (i.e., Bronsted acidic ionic liquid). A novel approach for the effective exfoliation of graphene sheets is demonstrated by (i) simultaneously applying a constant potential through an electrochemical cell (with different electrolyte concentrations) and (ii) together with sonication. The exfoliated graphene sheets are characterized through state-of-the-art techniques and sprayed on a glass substrate at optimum conditions. Thus, the transparent conducting sensor device is fabricated with a suitable contact electrode and used for ammonia vapor sensing and the sensor performances are highly dependent on the concentration of the ionic liquid used during the electrochemical exfoliation. The sensing response and limit of detection for the exfoliated graphene-based film were calculated as 3.56% and 432 ppb, respectively. Further studies indicated that the fabricated sensors are more selective towards ammonia molecules with quick response and recovery times.

Synthesis of few-layer graphene through simultaneous ultrasonication and electrochemical exfoliation in a Bronsted acidic ionic liquid [NMP] [HSO4] aqueous electrolyte for NH3 vapor sensing
    Abstract
    1 Introduction
    2 Experimental details
        2.1 Materials
        2.2 Preparation of exfoliated graphene
        2.3 Fabrication of thin-film sensors and gas sensing
        2.4 Characterization techniques
    3 Results and discussion
        3.1 XRD analysis
        3.2 Raman analysis
        3.3 FT-IR analysis
        3.4 FE-SEM and TEM analyses
        3.5 Anodic exfoliation process of graphene.
        3.6 NH3 vapor sensing studies
    4 Conclusion
    Acknowledgements 
    References

• K. Lakshmanamoorthy(Carbon Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620 015, India)
• S. Manivannan(Carbon Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Tiruchirappalli 620 015, India) Corresponding author